Comparative analysis of the combined petrosal and the pretemporal transcavernous anterior petrosal approach to the petroclival region

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  • 1 Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona; and
  • | 2 Department of Neurosurgery, University of Colorado, Denver, Colorado
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OBJECTIVE

The combined petrosal (CP) approach has been traditionally used to resect petroclival meningioma (PCM). The pretemporal transcavernous anterior petrosal (PTAP) approach has emerged as an alternative. A quantitative comparison of both approaches has not been made. This anatomical study compared the surgical corridors afforded by both approaches and identified key elements of the approach selection process.

METHODS

Twelve cadaveric specimens were dissected, and 10 were used for morphometric analysis. Groups A and B (n = 5 in each) underwent the CP and PTAP approaches, respectively. The area of drilled clivus, lengths of cranial nerves (CNs) II–X, length of posterior circulation vessels, surgical area of exposure of the brainstem, and angles of attack anterior and posterior to a common target were measured and compared.

RESULTS

The area of drilled clivus was significantly greater in group A than group B (mean ± SD 88.7 ± 17.1 mm2 vs 48.4 ± 17.9 mm2, p < 0.01). Longer segments of ipsilateral CN IV (52.4 ± 2.33 mm vs 46.5 ± 3.71 mm, p < 0.02), CN IX, and CN X (9.91 ± 3.21 mm vs 0.00 ± 0.00 mm, p < 0.01) were exposed in group A than group B. Shorter portions of CN II (9.31 ± 1.28 mm vs 17.6 ± 6.89 mm, p < 0.02) and V1 (26.9 ± 4.62 mm vs 32.4 ± 1.93 mm, p < 0.03) were exposed in group A than group B. Longer segments of ipsilateral superior cerebellar artery (SCA) were exposed in group A than group B (36.0 ± 4.91 mm vs 25.8 ± 3.55 mm, p < 0.02), but there was less exposure of contralateral SCA (0.00 ± 0.00 mm vs 7.95 ± 3.33 mm, p < 0.01). There was no statistically significant difference between groups with regard to the combined area of the exposed cerebral peduncles and pons (p = 0.75). Although exposure of the medulla was limited, group A had significantly greater exposure of the medulla than group B (p < 0.01). Finally, group A had a smaller anterior angle of attack than group B (24.1° ± 5.62° vs 34.8° ± 7.51°, p < 0.03).

CONCLUSIONS

This is the first study to quantitatively identify the advantages and limitations of the CP and PTAP approaches from an anatomical perspective. Understanding these data will aid in designing maximally effective yet minimally invasive approaches to PCM.

ABBREVIATIONS

ACP = anterior clinoid process; CN = cranial nerve; CP = combined petrosal; GSPN = greater superior petrosal nerve; ICA = internal carotid artery; PCM = petroclival meningioma; PCP = posterior clinoidal process; PTAP = pretemporal transcavernous anterior petrosal; SCA = superior cerebellar artery; SPS = superior petrosal sinus.

OBJECTIVE

The combined petrosal (CP) approach has been traditionally used to resect petroclival meningioma (PCM). The pretemporal transcavernous anterior petrosal (PTAP) approach has emerged as an alternative. A quantitative comparison of both approaches has not been made. This anatomical study compared the surgical corridors afforded by both approaches and identified key elements of the approach selection process.

METHODS

Twelve cadaveric specimens were dissected, and 10 were used for morphometric analysis. Groups A and B (n = 5 in each) underwent the CP and PTAP approaches, respectively. The area of drilled clivus, lengths of cranial nerves (CNs) II–X, length of posterior circulation vessels, surgical area of exposure of the brainstem, and angles of attack anterior and posterior to a common target were measured and compared.

RESULTS

The area of drilled clivus was significantly greater in group A than group B (mean ± SD 88.7 ± 17.1 mm2 vs 48.4 ± 17.9 mm2, p < 0.01). Longer segments of ipsilateral CN IV (52.4 ± 2.33 mm vs 46.5 ± 3.71 mm, p < 0.02), CN IX, and CN X (9.91 ± 3.21 mm vs 0.00 ± 0.00 mm, p < 0.01) were exposed in group A than group B. Shorter portions of CN II (9.31 ± 1.28 mm vs 17.6 ± 6.89 mm, p < 0.02) and V1 (26.9 ± 4.62 mm vs 32.4 ± 1.93 mm, p < 0.03) were exposed in group A than group B. Longer segments of ipsilateral superior cerebellar artery (SCA) were exposed in group A than group B (36.0 ± 4.91 mm vs 25.8 ± 3.55 mm, p < 0.02), but there was less exposure of contralateral SCA (0.00 ± 0.00 mm vs 7.95 ± 3.33 mm, p < 0.01). There was no statistically significant difference between groups with regard to the combined area of the exposed cerebral peduncles and pons (p = 0.75). Although exposure of the medulla was limited, group A had significantly greater exposure of the medulla than group B (p < 0.01). Finally, group A had a smaller anterior angle of attack than group B (24.1° ± 5.62° vs 34.8° ± 7.51°, p < 0.03).

CONCLUSIONS

This is the first study to quantitatively identify the advantages and limitations of the CP and PTAP approaches from an anatomical perspective. Understanding these data will aid in designing maximally effective yet minimally invasive approaches to PCM.

In Brief

Two approaches for resection of petroclival meningioma (PCM) were compared to gain insight into the advantages and limitations of each approach. Although both approaches exposed similar areas of the upper brainstem, the medulla was exposed with only the combined petrosal approach through the presigmoid window and across the line of origin of the lower cranial nerves. Neither approach afforded adequate exposure of the hypoglossal nerve. This study will aid in tailoring surgical approaches to PCM.

Once described as a surgical “no man’s land,”1 the petroclival region remains one of the most complex skull base territories to approach surgically. This narrow space—between the medial petrous apex laterally, lower two-thirds of the clivus medially, and brainstem posteriorly—is the crossroads for half of the cranial nerves (CNs) en route to their extradural destinations. Similarly, the majority of the posterior circulation vasculature traverses this region. Petroclival meningioma (PCM) arises at the petrous tip, medial to the internal auditory meatus and posterior to the gasserian ganglion.2 These tumors may involve the upper clivus, cavernous sinus, Meckel’s cave, tentorium, and petrous apex to variable extents,3 but large meningiomas inevitably involve the suprasellar, interpeduncular, prepontine, and ambient cisterns.4 Identifying the best surgical approach for treating these lesions remains a challenge.

The combined petrosal (CP) approach, popularized by Hakuba et al.,5 Al-Mefty et al.,2,6–8 and many others,9,10 has been used to resect PCMs. The CP approach combines the anterior transpetrosal approach with the retrolabyrinthine presigmoid transtentorial approach. Gross-total resection can be achieved in some patients with large PCMs while hearing and facial nerve function are preserved.8 The CP approach also affords access to the posterior cavernous sinus, Meckel’s cave, posterolateral brainstem, and cerebellopontine angle, which facilitates tumor resection even in patients with firm lesions.8 Nonetheless, the inherent morbidities associated with sigmoid sinus thrombosis, venous infarction, temporal lobe injury secondary to excessive retraction, and damage to the labyrinth may dissuade surgeons and patients alike from choosing this approach.11,12

In our practice, we use the CP approach to resect large PCMs. Recently, however, a more anterolateral trajectory that combines the pretemporal transcavernous approach pioneered by Dolenc,13 the anterior transpetrosal approach of Kawase et al.,14 and trans–Meckel’s cave transtentorial exposure has emerged as an alternative for resection of large PCMs.4,15 In a recent series by Liao et al.,4 this pretemporal transcavernous anterior petrosal (PTAP) approach was used to achieve gross- or near-total resection of large PCMs with acceptable morbidity and no deaths.

Although both the CP and PTAP approaches may be feasible surgical options for managing PCMs, the indications for using one over the other remain unclear. Furthermore, objective data comparing both approaches are nonexistent. In this study, we conducted an anatomical investigation to 1) compare the technical nuances of the CP and the PTAP approaches, 2) provide quantitative comparisons of the exposures obtained with both approaches, and 3) identify key elements necessary to select the appropriate approach to PCMs.

Methods

The study was conducted in the surgical neuroanatomy laboratory at Barrow Neurological Institute. Twelve silicone-injected cadaveric head specimens were dissected using previously described methods.

CP Approach

The CP approach has been described elsewhere2,16,17 and is summarized below (Fig. 1 and Video 1).

VIDEO 1. Surgical videos illustrating the key steps involved in performing the CP and PTAP approaches. Copyright Samy Youssef. Published with permission. Click here to view.

FIG. 1.
FIG. 1.

Photographs of stepwise cadaveric dissection illustrating the CP approach. A: Elevation of the sternomastoid–temporal fascia flap on the left side. The temporalis muscle is subsequently incised and reflected anteroinferiorly (not shown). The sigmoid sinus (SS) is fully skeletonized, and the jugular bulb (JB) is exposed. The antrum is opened, and the semicircular canals are skeletonized. The mastoid segment of the facial artery (CN VII mastoid seg.) is identified. Trautmann’s triangle dura (bound by the SS, SPS, otic capsule, and JB) is exposed. Subsequently, a kidney-shaped craniotomy is drilled, exposing the temporal, inferior parietal, and retrosigmoid dura. B: The middle meningeal artery (MMA) is divided to allow for further anterior exposure. The inferior aspect of V3 and the gasserian ganglion (GG) are also dissected off the underlying bone to maximize exposure of the petrous apex (PA). C: Anterior petrosectomy is performed to expose the dura overlying the pons immediately underneath the trigeminal nerve (CN V) root as it enters Meckel’s cave. Meckel’s cave is opened, and the GG is exposed. D: The blue line indicates the dural incision pattern used in this approach. The middle fossa dura at the base of the temporal lobe is incised from anterior to posterior, parallel to the SPS and as far back as possible above the transverse sinus. The presigmoid dura is incised in a vertical fashion, behind the endolymphatic sac, from the bulb up to the SPS where the incision curves anteriorly below the SPS. The temporal and presigmoid incisions are then joined, while the SPS is divided medial to where the superior cerebellar venous complex enters and drains into the SPS. E: The tentorium is divided while the trochlear nerve (CN IV) is preserved. F: The divided tentorium is retracted anteriorly and then resected. CN IV and the SCA are shown coursing through the posterior part of the ambient cistern. G: The lateral aspect of the lower crus cerebri (CC) and upper pons is exposed in a subtemporal fashion after resection of the tentorium. H: The posterior clinoid process has been drilled and the posterior cavernous sinus has been opened, exposing the cavernous segments of the ICA and abducens nerve (CN VI). This allows for greater exposure of the ipsilateral pons and for exposure of a longer segment of the basilar artery (BA). I: Magnified view showing both the cisternal and cavernous segments of CN VI. J: View obtained from the presigmoid window. This unobstructed, superficial view of the surgical field, below and above the root entry zone of the CN V, can be obtained only by division of the SPS and retraction of the transverse-sigmoid venous complex posteriorly. K: The presigmoid view also allows excellent visualization of the facial-cochlear complex. L: A small segment of the lower CNs is also visualized. AICA = anterior inferior cerebellar artery; LM = Liliequist membrane; TS = transverse sinus. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Step 1: Elevation of the Sternomastoid–Temporal Fascia Flap

A C-shaped skin incision is made, extending from the level of the mastoid tip, curving superiorly parallel to the superior temporal line, and then descending to the level of the zygoma approximately two finger-widths anterior to the external auditory canal. The skin flap is retracted anteriorly and inferiorly. The temporalis fascia is incised and dissected posteriorly and in continuation with the sternomastoid muscle. The temporalis muscle is then incised and reflected anteroinferiorly.

Step 2: Retrolabyrinthine Presigmoid Exposure

The sigmoid sinus is fully skeletonized from its junction with the transverse sinus down to the jugular bulb. The antrum is opened, and the semicircular canals are exposed. The inferior aspect of the mastoid is drilled to expose the bulb. At the conclusion of this step, the dura mater of Trautmann’s triangle (bound by the sigmoid and superior petrosal sinuses, otic capsule, and jugular bulb) is exposed.

Step 3: Temporal, Parietal, Occipital Craniotomy

The dura overlying the sigmoid transverse junction is dissected. A kidney-shaped craniotomy exposing the temporal, inferior parietal, and lateral occipital (retrosigmoid) dura is fashioned.

Step 4: Anterior Petrosectomy

The dura of the temporal lobe is elevated off the middle fossa floor from posterior to anterior. The greater superior petrosal nerve (GSPN) is identified and followed anteriorly as it intersects V3 at the foramen ovale. The inferior aspect of V3 and the gasserian ganglion are also dissected off the underlying bone and reflected as anterior as possible to maximize exposure of the petrous apex. In this study, we also continued extradural dissection as far anterior as possible to expose V2 and the posterior aspect of the cavernous sinus. The Kawase triangle—delineated by the arcuate eminence, GSPN, V3, and petrous ridge—is outlined and drilled.

Step 5: Dural Opening and Tentorium Resection

The dura overlying the base of the temporal lobe is incised from anterior to posterior, parallel to the superior petrosal sinus (SPS), and as far back as possible above the transverse sinus. The presigmoid dura is incised in a vertical fashion, behind the endolymphatic sac, from the bulb to the SPS, where the incision curves anteriorly below the SPS. The temporal and presigmoid incisions are then joined, while the SPS is divided medial to where the superior cerebellar venous complex enters and drains into the SPS. The tentorium is divided while the trochlear nerve is preserved. The dura forming the roof of Meckel’s cave is cut, as well as the SPS above the porous, and the incision continues medially to include the tentorium; this maneuver completes the anterior cut of the tentorium resection. The posterior petroclinoid fold is divided, and the posterior aspect of the infratrochlear triangle is accessed.

PTAP Approach

The PTAP approach has been described elsewhere4,18 and is summarized below (Fig. 2 and Video 1).

FIG. 2.
FIG. 2.

Photographs of stepwise cadaveric dissection illustrating the PTAP approach. A: Surgical view after completion of right-side orbitozygomatic craniotomy. The meningio-orbital fold (arrow) tethers the frontotemporal basal dura to the periorbita (PO). B: The meningio-orbital fold is divided as the outer dural layer is mobilized from anterior to posterior until the ACP is completely exposed and then drilled. C: Extradural dissection is continued posteriorly to expose V3 and the GSPN. The GG is completely exposed as peeling continues medially toward the tentorium. D: The PA segment to be drilled and the arcuate eminence (AE) are exposed. E: The PA is drilled, exposing the dura (asterisk) overlying the pons. F: The subtemporal dura, as well as that overlying the PA, has been opened. Similarly, the cavernous sinus has been opened, exposing CN III, CN IV, V1, and CN VI coursing below Gruber’s ligament (GL). G: The window afforded by drilling the PA and a part of the internal auditory canal. H: Magnified view of the nerves of the internal auditory canal. FD = frontal dura; P. maj. = portio major of the trigeminal nerve; P. min. = portio minor of trigeminal nerve; TD = temporal dura. See Fig. 1 for definitions of abbreviations. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Step 1: Orbitozygomatic Craniotomy

An orbitozygomatic craniotomy is performed, and the lesser wing of the sphenoid bone is drilled medially toward the superior superior orbital fissure.

Step 2: Exposure and Drilling of the Anterior Clinoid Process

The meningio-orbital fold is identified and divided. The meningio-orbital fold represents the easiest point at which to start dissection between the meningeal dura of the temporal lobe and the lateral wall of the cavernous sinus. The outer meningeal layer is mobilized from anterior to posterior until the anterior clinoid process (ACP) is completely exposed. Drilling begins at the superolateral aspect of the optic canal and progresses medially. The core of the ACP is drilled up to the periosteal layer encasing the optic nerve. The optic strut is then carefully drilled while great care is taken to avoid injury to the paraclinoid internal carotid artery (ICA), which courses against the posterior surface of the strut.

Step 3: Anterior Petrosectomy

Extradural dissection is continued posteriorly to expose V3, ligate the middle meningeal artery, and expose the GSPN. The gasserian ganglion is completely exposed as peeling continues medially toward the tentorium. The Kawase triangle is exposed and drilled.

Step 4: Dural Opening and Tentorium Resection

A T-shaped dural opening is made with the vertical limb along the sylvian fissure and the horizontal limb, extending from the ACP along the base of the temporal lobe toward the site for anterior petrosectomy. Meckel’s cave is then opened over the gasserian ganglion toward the tentorial incisura.

Step 5: Combined Intradural-Extradural Mobilization of Neurovascular Structures

Multiple neurovascular elements are mobilized to create a safe corridor for drilling the posterior clinoid and dorsum sella. The falciform ligament and the distal dural ring are divided to facilitate ICA mobilization. Subsequently, the oculomotor trigone is opened, and the nerve is sharply mobilized up to its entrance to the superior orbital fissure while the adjacent trochlear nerve is protected. The proximal sylvian fissure is then opened widely, and the posterior clinoidal process (PCP) is exposed and drilled.

Quantitative Measurements

Measurements were obtained using the StealthStation stereotactic navigation system (Medtronic). The CP approach was performed in 5 specimens (group A), whereas the PTAP approach was performed in another 5 specimens (group B). Figure 3 depicts the anatomical elements that were measured and compared.

Area of Drilled Clivus

Rhoton’s definition of the three clival segments was adapted.19,20 Accordingly, the upper third of the clivus extends from the dorsum sella rostrally to a transverse line connecting to the dural pori of the abducens nerves caudally. The middle clivus extends below the upper clivus down to the level of the glossopharyngeal meatus, whereas the inferior limit of the lower clivus is represented by the lower border of the anterior aspect of the foramen magnum. Several coordinate points along the margins of the drilled region of the clivus were recorded, and the areas were calculated.

Neurovascular Elements and Brainstem

The lengths of bilaterally exposed CNs II–X, posterior cerebral artery, superior cerebellar artery (SCA), and vertebral artery, as well as the length of the basilar artery, were recorded and compared between the two groups.

Several points on the ventral surface of the brainstem bilaterally were recorded: 1) superior-lateral exposable point on the ipsilateral side; 2) inferior-lateral exposable point on the ipsilateral side; 3) superior exposable point along a vertical line passing ipsilateral CN III; 4) inferior exposable point along a vertical line passing ipsilateral CN III; 5) superior exposable point along the midline; 6) inferior exposable point along the midline; 7) superior-lateral exposable point on the contralateral side; 8) inferior-lateral exposable point on the contralateral side; 9) superior-lateral exposable point through the presigmoid window; 10) inferior-lateral exposable point through the presigmoid window; 11) inferior-medial exposable point through the presigmoid window; and 12) superior-medial exposable point through the presigmoid window (Fig. 3). The areas created on the surface of the brainstem were calculated and compared between the two groups.

FIG. 3.
FIG. 3.

A and B: Schematic illustrations showing ventral (A) and lateral (B) views of the brainstem and relevant neurovascular elements that were identified and measured. The following elements are shown: superior-lateral exposable point on the ipsilateral side (1); inferior-lateral exposable point on the ipsilateral side (2); superior exposable point along the vertical dashed line passing ipsilateral CN III (3); inferior exposable point along the vertical dashed line passing ipsilateral CN III (4); superior exposable point along the midline (5); inferior exposable point along the midline (6); superior-lateral exposable point on the contralateral side (7); inferior-lateral exposable point on the contralateral side (8); superior-lateral exposable point through the presigmoid window (9); inferior-lateral exposable point through the presigmoid window (10); inferior-medial exposable point through the presigmoid window (11); and superior-medial exposable point through the presigmoid window (12). C: Photograph of cadaveric dissection showing the anterior and posterior angles of attack, with the target being the abducens nerve as it crosses Gruber’s ligament. The anterior and posterior angles are outlined in red and blue, respectively. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Angle of Attack

Maneuverability with each approach was evaluated with respect to a constant and easily accessible target, the point of intersection between CN VI and Gruber’s ligament. This value was quantitatively measured as the maximum allowable angle of attack in the horizontal plane. The angle of attack was measured by moving the proximal end of a probe from an extremely anterior position to an extremely posterior position, with the distal end placed at the target. A line perpendicular to the greater superficial petrosal nerve was defined as a neutral reference line, and the allowable angles of attack anterior and posterior to this line were defined as the anterior and posterior angles of attack, respectively. The total, anterior, and posterior angles of attack were measured and compared between the two approaches.

Statistical Analysis

Statistical comparisons were performed using PASW Statistics version 18.0.0 (IBM Corp.). Heron’s formula was used to calculate areas as the sum of triangles. The independent t-test was used for comparisons, and p < 0.05 was considered statistically significant.

Results

Morphometric Comparison of the CP and PTAP Approaches

Area of Drilled Clivus

The predrilled areas of the upper third of the clivus were similar between the two groups (p = 0.60), but a significantly greater area was drilled in group A than group B (mean ± SD 88.7 ± 17.1 mm2 vs 48.4 ± 17.9 mm2, p < 0.01). The lower third of the clivus could not be exposed in group B.

Neurovascular Elements

Longer segments of ipsilateral CN IV (mean ± SD 52.4 ± 2.33 mm vs 46.5 ± 3.71 mm, p < 0.02), CN IX, and CN X (9.91 ± 3.21 mm vs 0.00 ± 0.00 mm, p < 0.01) were exposed in group A than group B. However, shorter portions of CN II (9.31 ± 1.28 mm vs 17.6 ± 6.89 mm, p = 0.009) and V1 (26.9 ± 4.62 mm vs 32.4 ± 1.93 mm, p < 0.03) were exposed in group A than group B. There were no statistically significant differences with respect to the other evaluated ipsilateral or contralateral nerves (Fig. 4).

FIG. 4.
FIG. 4.

Quantitative comparisons of the CP and PTAP approaches. A: Lengths of the exposed optic nerve (CN II) and tract. B: Lengths of exposed ipsilateral and contralateral CN III. C: Lengths of exposed trochlear, ophthalmic, and maxillary nerves. D: Lengths of exposed cavernous abducens nerve (CN VI), facial nerve (CN VII), vestibulocochlear nerve (CN VIII), and glossopharyngeal and vagus nerves (lower CNs). E: Lengths of exposed ipsilateral and contralateral posterior cerebral artery (PCA), SCA, and basilar artery (BA). F: Combined areas of the cerebral peduncles and pons exposed lateral (ipsilateral lateral) and medial (ipsilateral medial) to the vertical line that crossed the point where CN III emerges from the interpeduncular fossa, as well as the area of the brainstem past the midline on the contralateral side (contralateral medial). G: Areas of exposed medulla. PMS = pontomedullary sulcus. Error bars indicate SD.

With regard to ipsilateral vessels, longer segments of SCA were exposed in group A than group B (mean ± SD 36.0 ± 4.91 mm vs 25.8 ± 3.55 mm, p < 0.02). Interestingly, group A had less exposure of contralateral SCA than group B (0.00 ± 0.00 mm vs 7.95 ± 3.33 mm, p < 0.01). There were no statistically significant differences between groups with respect to exposure of segments of the basilar artery or the ipsilateral or contralateral posterior cerebral artery.

Brainstem Exposure

There were no statistically significant differences between groups in terms of the combined areas of the cerebral peduncles and pons that were exposed lateral to the vertical line that crossed the point where CN III emerges from the interpeduncular fossa (p = 0.75; Figs. 3 and 4). Similarly, the areas of brainstem between that vertical line and the midline, as well as the areas past the midline on the contralateral side, were not different between groups (p = 0.47 and 0.60, respectively).

Although limited exposure of medulla was achieved in group A (mean ± SD 48.1 ± 19.9 mm2), the medulla was not exposed in group B (0.00 ± 0.00 mm2, p < 0.01; Fig. 4).

Angle of Attack

Group A had a smaller anterior angle of attack than group B (mean ± SD 24.1° ± 5.62° vs 34.8° ± 7.51°, p < 0.03) and a larger posterior angle of attack (27.9° ± 4.26° vs 18.3° ± 6.51°, p = 0.047; Fig. 5). There was no difference between groups with respect to the total angle confined by the anterior and posterior rays (51.9° ± 4.90° vs 53.2° ± 7.82°, p = 0.47).

FIG. 5.
FIG. 5.

Angles of attack for the CP and PTAP approaches. The PTAP approach allows for a larger angle of attack anterior to the target (intersection of CN VI with Gruber’s ligament), whereas the CP approach allows for a larger angle of attack posterior to the target. Error bars indicate SD.

Discussion

Direct surgical access into and maneuverability within the petroclival region are impeded by the inherent stereo-hindrance created by the osteological and neurovascular structures. Two surgical approaches, CP and PTAP, have been safely utilized to resect PCMs in this location.6,8–10,13 We present the first study to morphometrically compare both approaches on an anatomical basis.

Technical Comparison of Surgical Approaches to the Petroclival Region

Two components are common to both approaches: 1) anterior petrosectomy, and 2) trans–Meckel’s cave transtentorial exposure. In both approaches, interdural dissection is used to expose the gasserian ganglion and the lateral wall of the cavernous sinus to variable extents. Similarly, to maximize petroclival exposure, the inferior aspect of V3 is dissected off the underlying petrous ICA and trigeminal impression and reflected as anterior as possible to facilitate removal of the medial petrous apex. In both approaches, the internal acoustic meatus can be exposed from porous to fundus, if needed.

Despite these similarities, several key technical maneuvers differentiate the approaches. First, to gain adequate caudal exposure of the petroclival region from the anterolateral perspective afforded by the PTAP approach, extradural anterior clinoidectomy (with or without paraclinoid ICA mobilization) with full mobilization of CN III and drilling of the PCP are often necessary. Such extensive anterior exposure is not required for the CP approach. Second, the CP approach necessities extensive mastoidectomy with mobilization of the sigmoid sinus down to the jugular bulb to adequately expose the sinodural angle and presigmoid dura without violating the semicircular canals. Finally, to adequately mobilize the sigmoid sinus posteriorly with the CP approach, the retrosigmoid and occipital dura above the transverse sinus must be exposed first.

Quantitative Comparison of the CP and PTAP Approaches

To compare exposure between the groups, several neurovascular elements were used as surrogate targets. Our results indicated that the CP approach provides greater exposure of ipsilateral CN IV, CN IX, and CN X, as well as the ipsilateral SCA and medulla. Greater exposure of CN IV with the CP approach could only be achieved by dividing the SPS and resecting the posterior aspect of the tentorium to expose the quadrigeminal cistern. Similarly, exposure of the lower CNs and medulla in a retrolabyrinthine fashion was possible only after disconnecting the transverse-sigmoid junction from the SPS and tentorium and retracting the sinuses posteriorly. Regardless of the extent of drilling into the clivus, the PTAP approach failed to adequately expose CN IX, CN X, and medulla (Figs. 4 and 6). These findings are consistent with the intraoperative findings of Liao et al.4

FIG. 6.
FIG. 6.

MR images and schematic illustrations of the CP and PTAP approaches for PCM resection. A and B: Axial (A) and coronal (B) MR images with contrast illustrating a PCM that was best managed with the CP approach. C: Schematic illustration of the skin incision used to perform the CP approach. D: Schematic illustration of the surgical view of a PCM that was best approached with the CP approach. E and F: Axial (E) and coronal (F) MR images with contrast illustrating a PCM that was best managed with the PTAP approach. G: Schematic illustration of the skin incision used to perform the PTAP approach. H: Schematic illustration of the surgical view of a PCM that was best approached with the PTAP approach. mast. seg. = mastoid segment. See Fig. 1 for definitions of abbreviations. Used with permission from Barrow Neurological Institute, Phoenix, Arizona (panels C, D, G, and H).

Despite the improved exposure of the medulla and lower CNs obtained with the presigmoid component of the CP approach, it is evident that preservation of the labyrinth hinders the medial extent of the approach. Moreover, any attempt to reach further medially and anteriorly along the brainstem represents, by definition, a transgression of the plane of origin of the lower CNs, which may be at risk during dissection (Fig. 6).

Although both the CP and PTAP approaches provided low enough exposure of the basilar artery to reach the origin of the ipsilateral SCA in each specimen, the mean length of exposed SCA was 28% greater with the CP approach. This improved exposure is directly related to the increased length of the pontomesencephalic segment of the SCA that is visible only from a subtemporal view after posterior division of the tentorium with the CP approach. Interestingly, the PTAP approach allowed for significantly greater exposure of the contralateral SCA (p < 0.01). It was visually evident that the convex shape of the pons, because it opposes the clivus at the level of the SCA origin, obstructed any attempt to reach the contralateral SCA with a posterior approach (such as the CP approach), regardless of the area of drilled clivus. This stereo-hindrance due to the pons limited the length of exposed contralateral SCA to a mean ± SD of 7.95 ± 3.33 mm, but did not completely obstruct exposure.

It was particularly interesting that no statistically significant difference (or even a trend) was found between groups with regard to the combined areas of ipsilateral cerebral peduncles and pons that were exposed lateral (p = 0.75) or medial (p = 0.47) to the vertical line that crossed the point where CN III emerges from the interpeduncular fossa. Similarly, neither approach provided an advantage over the other in terms of contralateral brainstem exposure. These findings are consistent with our clinical observations.

With regard to maneuverability, there was no overall difference between the approaches as measured according to the overall angle of attack (p = 0.47). However, the PTAP approach had better maneuverability than the CP approach in the region anterior to the entrance of CN VI to Dorello’s canal (p = 0.03). Conversely, the posterior angle of attack favored the CP approach (p = 0.05).

Approach Selection

Use of a minimally invasive skull base approach maximizes surgical efficiency and tumor resection while minimizing manipulation of neurovascular structures and subsequent morbidities. The results of our study may guide the surgical approach selection process on the basis of four key points (Fig. 6 and Video 2).

VIDEO 2. A 3D model showing tumors that were best approached with the CP approach or the PTAP approach. Used with permission from Barrow Neurological Institute, Phoenix, Arizona. Click here to view.

1) Degree and Direction of Tumor Extension

PCM arises at the tip of the petrous apex medial to the internal auditory canal.2 Ichimura and colleagues classified these tumors into four subtypes according to their origin, suspected location of dural attachment, and direction of trigeminal nerve displacement.3 The subtypes are 1) upper clival, where the tumor attaches medial to CN V and displaces it laterally without cavernous sinus invasion; 2) cavernous, where the tumor originates from the posterior cavernous sinus (medial to CN V) with bilateral extension into the posterior fossa and lateral displacement of CN V; 3) tentorial, where the tumor originates from the tentorium with significant attachment to the petroclival fissure and inferomedial displacement of CN V; and 4) petrous apex, where the tumor attaches to the petrous apex and lies lateral to CN V and medial to the internal auditory canal with superomedial CN V displacement.

In a series of 91 patients, the overall prevalence of tumor invasion into Meckel’s cave was 70.3%, with the lowest prevalence in those with the petrous apex subtype (2 of 8 patients). Hence, anterior transpetrosal and trans–Meckel’s cave exposure is usually an essential component of any surgical approach to large PCMs. The question then becomes whether this step should be combined with a posterior petrosal or an anterolateral transcavernous approach. Our results suggest that, in general, the medial and lateral extents of the tumor in relation to the pons and cerebral peduncles may not be a major determining factor for choosing one approach over the other, because there was no significant difference between groups A and B with respect to the exposed areas of the pons and peduncles (Fig. 4). This finding is consistent with our clinical observations and those of others.4,8 However, tumor extension along the rostral-caudal axis is what seems to be important. Specifically, lesions that extend to the lower clivus, compress the medulla, and displace the lower CNs are best managed with the CP approach (Fig. 6). According to our anatomical data, the PTAP approach does not adequately expose this region. However, the CP approach is not a panacea. Reaching further medial and anterior to the medulla through the presigmoid window is difficult because the surgeon would need to operate across the lower CNs, thereby risking iatrogenic injury (Fig. 6). Finally, our results show that the PTAP approach allows for greater exposure of the region anterior to the chiasm.

2) Venous Anatomy

Every patient with PCM must undergo preoperative cerebral venous imaging because such imaging aids in surgical approach planning. A prominent sigmoid sinus and high jugular bulb limit presigmoid exposure with the CP approach. Similarly, if a major draining vein, particularly one on the left side, terminates early into a tentorial sinus instead of entering the region of the transverse-sigmoid sinus junction, the surgeon would have to retract anterior to that vein and thereby limit exposure behind it. In these situations, the PTAP approach may be favored when feasible.

3) Cavernous Sinus Involvement

PCMs often involve the cavernous sinus, as described above. These tumors may infiltrate the ICA21 and CNs,22 which may explain the high functional cost and recurrence rate associated with aggressive cavernous sinus exploration.23–26 Although we do not advocate aggressive exenteration of meningioma from within the sinus proper, like others25,26 we believe that decompressing the lateral wall of the cavernous sinus by debulking the tumor in the interdural plane between the meningeal and periosteal dural layers of the lateral wall is beneficial. Hence, in these cases, the PTAP approach may be favored over the CP approach (provided that the tumor does not extend caudally toward the lower CNs as discussed above). Similarly, in patients who require decompression of the optic nerve and canal, anterior clinoidectomy combined with the PTAP approach provides significant value.

4) Hearing Status

It is important to objectively evaluate hearing status bilaterally in each patient with PCM. For patients with functional hearing on only the ipsilateral side of the lesion, performing the CP retrolabyrinthine approach on the functional side may put the only ear with functional hearing at risk of injury. Hence, the PTAP approach would be favored. For patients with significantly compromised hearing on the side of the lesion, the translabyrinthine variation of the CP approach provides greater exposure than the retrolabyrinthine variation without additional risk of morbidity.

Although the abovementioned factors are crucial for surgical approach selection, they cannot be used to predict the final outcome of each operation. As stated by Spetzler’s group in the early 2000s, “Regardless of the surgical approach used, the major determinants of the ability to achieve an excellent resection with a low rate of morbidity are the presence of an arachnoid plane around the tumor, the consistency of the tumor, and the degree of its involvement with critical neurovascular structures.”11 Nonetheless, selection of the appropriate surgical approach helps the surgeon to capitalize on these inherent tumor characteristics for the benefit of the patient during surgery.

Finally, regardless of the specific approach used, optimization of postoperative care is key to minimizing morbidities. Provision of adequate hydration after manipulation of the major venous sinuses, as performed with the CP approach, is necessary to prevent thrombosis. Sufficient eye patching and lubrication are mandatory for patients with transient or permanent facial weakness or paralysis. Prism lenses and extraocular muscle surgery may be used to treat patients with permanent cranial nerve palsy.

Literature Review

Considering the excellent yet different exposures afforded with the CP and PTAP approaches, we briefly reviewed the literature and focused on major clinical series that used either approach.

Cho and Al-Mefty wrote one of the first reports to describe the surgical techniques and outcomes of using the CP approach to manage PCM.8 In this series, they treated 7 patients, with a 71% rate of gross-total resection and no deaths. One of 6 patients lost hearing in the 1st year after surgery. Preoperatively, 6 patients had House-Brackmann grade I dysfunction and 1 patient had grade II–III dysfunction. At last follow-up, 5 patients had House-Brackmann grade I, 1 patient had House-Brackmann grade II, and 1 patient had House-Brackmann grade V dysfunction. Three patients developed transient abducens palsy, and 1 developed permanent abducens palsy.

In a subsequent series,27 64 patients with PCM were evaluated. In this series, the posterior petrosal, CP, anterior petrosal, total petrosal, and transmastoid retrosigmoid approaches were used to treat 27, 15, 11, 4, and 7 patients, respectively. Gross-total resection was achieved in 64% of patients. One postoperative death was related to pulmonary embolism. The mean preoperative Karnofsky Performance Status score was 85.31 (median 90), with a 47% rate of improvement after tumor resection. Preoperatively, 89% of patients had cranial nerve deficit. Of the 54 patients with more than 2 months of follow-up, 39% had persistent deficit. Of note, those with CN V and CN VIII deficits were more likely to improve from preoperative status, whereas those with CN VI deficit had a higher risk of sustaining new postoperative injury.

In another series reported by Kusumi et al.,28 23 patients underwent the CP approach for PCM resection, and the rate of gross- or near-total resection was 78.3% and there were no deaths. Eighteen patients had a Karnofsky Performance Status score > 90. Ten patients developed postoperative CN palsy (2 with CN V palsy, 2 with CN VI, 4 with CN VII, and 2 with lower CNs IX–XII). In a study by Mathiesen et al.,12 29 patients underwent the CP approach as a part of multimodal therapy for PCM. Simpson grade I and II resections were achieved in 12 patients, grade III in 2 patients, and grade IV in 15 patients. Four patients had preoperative CN III palsy, and 7 had postoperative palsy. All except 1 of these 7 patients with preoperative palsy recovered completely. With regard to CN VI, 3 patients had preoperative palsy, and a total of 6 patients had postoperative palsy. All deficits recovered during the follow-up period. Good facial function (House-Brackmann grades I and II) was obtained in 23 of 29 patients. Useful hearing (Gardner-Robertson hearing scale grades I and II) was preserved in 17 of 23 patients (74%) who underwent hearing preservation surgery. There were no deaths in this series.

To our knowledge, less surgical data are available for the PTAP approach than the CP approach. Liao et al.4 reported 18 patients who underwent the PTAP approach for resection of large PCMs. Gross-total resection was achieved in 7 patients (38.9%), near-total resection (> 95%) in 7 patients (38.9%), and subtotal resection (> 85%) in 4 patients (22.2%) (3 with > 90% resection and 1 with > 85%). Although no deaths were reported, all patients developed transient postoperative CN III palsy but recovered within 3 months. Transient abducens palsy was observed in 2 patients and permanent CN IV palsy in 3 patients. The same authors recently published29 the findings of their series of 109 patients with skull base meningiomas, of whom 28 had PCMs occupying what they referred to as zone IV (the anterior, middle, and posterior cranial fossa) and were treated with the PTAP approach. Simpson grade I, II, III, and IV resections were achieved in 3.6%, 32%, 17.9%, and 46.4% of patients, respectively. Seven patients developed new cranial nerve deficits and 7 developed strokes. Although the postoperative mortality rate of the entire cohort of 109 patients was 3.7%, the mortality rate of patients with tumor in zone IV was not mentioned.

Future Directions

To our knowledge, this study provides the first direct anatomical comparison of the CP and PTAP approaches. The anatomical advantages and limitations of both approaches were addressed quantitatively. Although the results of this study may guide the approach selection process, the true value of the key elements we identified can only be determined with prospective clinical studies. Future efforts are encouraged to compare the clinical outcomes of both approaches in a prospective manner. Furthermore, future studies—both cadaveric and clinical—should aim to identify strategies to overcome the limitations of each approach.

Conclusions

The CP and PTAP approaches have been used to treat large PCMs. Although each approach is associated with potential complications, true indications for choosing one over the other have not been established. This is the first study to provide objective insight into the advantages and limitations of both approaches from an anatomical perspective. Understanding the technical nuances and anatomical basis of each approach is incumbent on all skull base surgeons and is crucial for selecting the optimal management strategy.

Acknowledgments

We thank the staff of Neuroscience Publications at Barrow Neurological Institute for assistance with manuscript and video preparation.

Disclosures

Dr. Youssef is a consultant for Stryker and receives royalties from Mizuho.

Author Contributions

Conception and design: Labib, Zhao. Acquisition of data: Labib, Zhao, Houlihan, Abramov. Analysis and interpretation of data: Labib, Zhao, Houlihan. Drafting the article: Labib. Critically revising the article: Catapano, Naeem. Reviewed submitted version of manuscript: Lawton, Preul, Youssef. Administrative/technical/material support: Preul. Study supervision: Lawton, Preul, Youssef.

Supplemental Information

References

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    Kawase T, Toya S, Shiobara R, Mine T. Transpetrosal approach for aneurysms of the lower basilar artery. J Neurosurg. 1985;63(6):857861.

  • 2

    Al-Mefty O, Fox JL, Smith RR. Petrosal approach for petroclival meningiomas. Neurosurgery. 1988;22(3):510517.

  • 3

    Ichimura S, Kawase T, Onozuka S, et al. Four subtypes of petroclival meningiomas: differences in symptoms and operative findings using the anterior transpetrosal approach. Acta Neurochir (Wien). 2008;150(7):637645.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4

    Liao CH, Wang JT, Lin CF, et al. Pretemporal trans-Meckel’s cave transtentorial approach for large petroclival meningiomas. Neurosurg Focus. 2018;44(4):E10.

  • 5

    Hakuba A, Nishimura S, Jang BJ. A combined retroauricular and preauricular transpetrosal-transtentorial approach to clivus meningiomas. Surg Neurol. 1988;30(2):108116.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Al-Mefty O, Smith RR. Combined approaches in the management of brain lesions. In: Apuzzo MLJ, ed. Brain Surgery: Complication Avoidance and Management. Vol 2300. Churchill Livingstone;1993.

    • Search Google Scholar
    • Export Citation
  • 7

    Al-Mefty O, Ayoubi S, Smith R. The petrosal approach: indications, technique, and results. Acta Neurochir Suppl (Wien). 1991;53:166170.

  • 8

    Cho CW, Al-Mefty O. Combined petrosal approach to petroclival meningiomas. Neurosurgery. 2002;51(3):708718.

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    Fukushima T, Day JD, Hirahara K. Extradural total petrous apex resection with trigeminal translocation for improved exposure of the posterior cavernous sinus and petroclival region. Skull Base Surg. 1996;6(2):95103.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Miller CG, van Loveren HR, Keller JT, et al. Transpetrosal approach: surgical anatomy and technique. Neurosurgery. 1993;33(3):461469.

  • 11

    Bambakidis NC, Kakarla UK, Kim LJ, et al. Evolution of surgical approaches in the treatment of petroclival meningiomas: a retrospective review. Neurosurgery. 2007;61(5)(suppl 2):202211.

    • PubMed
    • Search Google Scholar
    • Export Citation
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    Mathiesen T, Gerlich A, Kihlström L, et al. Effects of using combined transpetrosal surgical approaches to treat petroclival meningiomas. Neurosurgery. 2007;60(6):982992.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Dolenc VV. A combined epi- and subdural direct approach to carotid-ophthalmic artery aneurysms. J Neurosurg. 1985;62(5):667672.

  • 14

    Kawase T, Shiobara R, Toya S. Anterior transpetrosal-transtentorial approach for sphenopetroclival meningiomas: surgical method and results in 10 patients. Neurosurgery. 1991;28(6):869876.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15

    Tripathi M, Deo RC, Suri A, et al. Quantitative analysis of the Kawase versus the modified Dolenc-Kawase approach for middle cranial fossa lesions with variable anteroposterior extension. J Neurosurg. 2015;123(1):1422.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Troude L Jr, Carissimi M Jr, Lavieille JP, Roche PH. How I do it: the combined petrosectomy. Acta Neurochir (Wien). 2016;158(4):711715.

  • 17

    Hanakita S, Watanabe K, Champagne PO, Froelich S. How I do it: combined petrosectomy. Acta Neurochir (Wien). 2019;161(11):23432347.

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    Labib MA, Borba Moreira L, Zhao X, et al. The side door and front door to the upper retroclival region: a comparative analysis of the open pretemporal and the endoscopic endonasal transcavernous approaches. J Neurosurg. 2020;133(6):18921904.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19

    Seker A, Inoue K, Osawa S, et al. Comparison of endoscopic transnasal and transoral approaches to the craniovertebral junction. World Neurosurg. 2010;74(6):583602.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20

    Funaki T, Matsushima T, Peris-Celda M, et al. Focal transnasal approach to the upper, middle, and lower clivus. Neurosurgery. 2013;73(2 Suppl Operative):ons155ons191.

    • Search Google Scholar
    • Export Citation
  • 21

    Kotapka MJ, Kalia KK, Martinez AJ, Sekhar LN. Infiltration of the carotid artery by cavernous sinus meningioma. J Neurosurg. 1994;81(2):252255.

  • 22

    Larson JJ, van Loveren HR, Balko MG, Tew JM Jr. Evidence of meningioma infiltration into cranial nerves: clinical implications for cavernous sinus meningiomas. J Neurosurg. 1995;83(4):596599.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    DeMonte F, Smith HK, al-Mefty O. Outcome of aggressive removal of cavernous sinus meningiomas. J Neurosurg. 1994;81(2):245251.

  • 24

    Sindou M, Wydh E, Jouanneau E, et al. Long-term follow-up of meningiomas of the cavernous sinus after surgical treatment alone. J Neurosurg. 2007;107(5):937944.

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    Chen SC, Lin CF, Liao CH, et al. The pretemporal trans-cavernous trans-Meckel’s trans-tentorial trans-petrosal approach: a combo skill in treating skull base meningiomas. J Neurooncol. 2020;146(3):407416.

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Illustration from Hanna (pp 927–930). Copyright Barbara A. Hanna. Published with permission.

  • View in gallery

    Photographs of stepwise cadaveric dissection illustrating the CP approach. A: Elevation of the sternomastoid–temporal fascia flap on the left side. The temporalis muscle is subsequently incised and reflected anteroinferiorly (not shown). The sigmoid sinus (SS) is fully skeletonized, and the jugular bulb (JB) is exposed. The antrum is opened, and the semicircular canals are skeletonized. The mastoid segment of the facial artery (CN VII mastoid seg.) is identified. Trautmann’s triangle dura (bound by the SS, SPS, otic capsule, and JB) is exposed. Subsequently, a kidney-shaped craniotomy is drilled, exposing the temporal, inferior parietal, and retrosigmoid dura. B: The middle meningeal artery (MMA) is divided to allow for further anterior exposure. The inferior aspect of V3 and the gasserian ganglion (GG) are also dissected off the underlying bone to maximize exposure of the petrous apex (PA). C: Anterior petrosectomy is performed to expose the dura overlying the pons immediately underneath the trigeminal nerve (CN V) root as it enters Meckel’s cave. Meckel’s cave is opened, and the GG is exposed. D: The blue line indicates the dural incision pattern used in this approach. The middle fossa dura at the base of the temporal lobe is incised from anterior to posterior, parallel to the SPS and as far back as possible above the transverse sinus. The presigmoid dura is incised in a vertical fashion, behind the endolymphatic sac, from the bulb up to the SPS where the incision curves anteriorly below the SPS. The temporal and presigmoid incisions are then joined, while the SPS is divided medial to where the superior cerebellar venous complex enters and drains into the SPS. E: The tentorium is divided while the trochlear nerve (CN IV) is preserved. F: The divided tentorium is retracted anteriorly and then resected. CN IV and the SCA are shown coursing through the posterior part of the ambient cistern. G: The lateral aspect of the lower crus cerebri (CC) and upper pons is exposed in a subtemporal fashion after resection of the tentorium. H: The posterior clinoid process has been drilled and the posterior cavernous sinus has been opened, exposing the cavernous segments of the ICA and abducens nerve (CN VI). This allows for greater exposure of the ipsilateral pons and for exposure of a longer segment of the basilar artery (BA). I: Magnified view showing both the cisternal and cavernous segments of CN VI. J: View obtained from the presigmoid window. This unobstructed, superficial view of the surgical field, below and above the root entry zone of the CN V, can be obtained only by division of the SPS and retraction of the transverse-sigmoid venous complex posteriorly. K: The presigmoid view also allows excellent visualization of the facial-cochlear complex. L: A small segment of the lower CNs is also visualized. AICA = anterior inferior cerebellar artery; LM = Liliequist membrane; TS = transverse sinus. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

  • View in gallery

    Photographs of stepwise cadaveric dissection illustrating the PTAP approach. A: Surgical view after completion of right-side orbitozygomatic craniotomy. The meningio-orbital fold (arrow) tethers the frontotemporal basal dura to the periorbita (PO). B: The meningio-orbital fold is divided as the outer dural layer is mobilized from anterior to posterior until the ACP is completely exposed and then drilled. C: Extradural dissection is continued posteriorly to expose V3 and the GSPN. The GG is completely exposed as peeling continues medially toward the tentorium. D: The PA segment to be drilled and the arcuate eminence (AE) are exposed. E: The PA is drilled, exposing the dura (asterisk) overlying the pons. F: The subtemporal dura, as well as that overlying the PA, has been opened. Similarly, the cavernous sinus has been opened, exposing CN III, CN IV, V1, and CN VI coursing below Gruber’s ligament (GL). G: The window afforded by drilling the PA and a part of the internal auditory canal. H: Magnified view of the nerves of the internal auditory canal. FD = frontal dura; P. maj. = portio major of the trigeminal nerve; P. min. = portio minor of trigeminal nerve; TD = temporal dura. See Fig. 1 for definitions of abbreviations. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

  • View in gallery

    A and B: Schematic illustrations showing ventral (A) and lateral (B) views of the brainstem and relevant neurovascular elements that were identified and measured. The following elements are shown: superior-lateral exposable point on the ipsilateral side (1); inferior-lateral exposable point on the ipsilateral side (2); superior exposable point along the vertical dashed line passing ipsilateral CN III (3); inferior exposable point along the vertical dashed line passing ipsilateral CN III (4); superior exposable point along the midline (5); inferior exposable point along the midline (6); superior-lateral exposable point on the contralateral side (7); inferior-lateral exposable point on the contralateral side (8); superior-lateral exposable point through the presigmoid window (9); inferior-lateral exposable point through the presigmoid window (10); inferior-medial exposable point through the presigmoid window (11); and superior-medial exposable point through the presigmoid window (12). C: Photograph of cadaveric dissection showing the anterior and posterior angles of attack, with the target being the abducens nerve as it crosses Gruber’s ligament. The anterior and posterior angles are outlined in red and blue, respectively. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

  • View in gallery

    Quantitative comparisons of the CP and PTAP approaches. A: Lengths of the exposed optic nerve (CN II) and tract. B: Lengths of exposed ipsilateral and contralateral CN III. C: Lengths of exposed trochlear, ophthalmic, and maxillary nerves. D: Lengths of exposed cavernous abducens nerve (CN VI), facial nerve (CN VII), vestibulocochlear nerve (CN VIII), and glossopharyngeal and vagus nerves (lower CNs). E: Lengths of exposed ipsilateral and contralateral posterior cerebral artery (PCA), SCA, and basilar artery (BA). F: Combined areas of the cerebral peduncles and pons exposed lateral (ipsilateral lateral) and medial (ipsilateral medial) to the vertical line that crossed the point where CN III emerges from the interpeduncular fossa, as well as the area of the brainstem past the midline on the contralateral side (contralateral medial). G: Areas of exposed medulla. PMS = pontomedullary sulcus. Error bars indicate SD.

  • View in gallery

    Angles of attack for the CP and PTAP approaches. The PTAP approach allows for a larger angle of attack anterior to the target (intersection of CN VI with Gruber’s ligament), whereas the CP approach allows for a larger angle of attack posterior to the target. Error bars indicate SD.

  • View in gallery

    MR images and schematic illustrations of the CP and PTAP approaches for PCM resection. A and B: Axial (A) and coronal (B) MR images with contrast illustrating a PCM that was best managed with the CP approach. C: Schematic illustration of the skin incision used to perform the CP approach. D: Schematic illustration of the surgical view of a PCM that was best approached with the CP approach. E and F: Axial (E) and coronal (F) MR images with contrast illustrating a PCM that was best managed with the PTAP approach. G: Schematic illustration of the skin incision used to perform the PTAP approach. H: Schematic illustration of the surgical view of a PCM that was best approached with the PTAP approach. mast. seg. = mastoid segment. See Fig. 1 for definitions of abbreviations. Used with permission from Barrow Neurological Institute, Phoenix, Arizona (panels C, D, G, and H).

  • 1

    Kawase T, Toya S, Shiobara R, Mine T. Transpetrosal approach for aneurysms of the lower basilar artery. J Neurosurg. 1985;63(6):857861.

  • 2

    Al-Mefty O, Fox JL, Smith RR. Petrosal approach for petroclival meningiomas. Neurosurgery. 1988;22(3):510517.

  • 3

    Ichimura S, Kawase T, Onozuka S, et al. Four subtypes of petroclival meningiomas: differences in symptoms and operative findings using the anterior transpetrosal approach. Acta Neurochir (Wien). 2008;150(7):637645.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4

    Liao CH, Wang JT, Lin CF, et al. Pretemporal trans-Meckel’s cave transtentorial approach for large petroclival meningiomas. Neurosurg Focus. 2018;44(4):E10.

  • 5

    Hakuba A, Nishimura S, Jang BJ. A combined retroauricular and preauricular transpetrosal-transtentorial approach to clivus meningiomas. Surg Neurol. 1988;30(2):108116.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Al-Mefty O, Smith RR. Combined approaches in the management of brain lesions. In: Apuzzo MLJ, ed. Brain Surgery: Complication Avoidance and Management. Vol 2300. Churchill Livingstone;1993.

    • Search Google Scholar
    • Export Citation
  • 7

    Al-Mefty O, Ayoubi S, Smith R. The petrosal approach: indications, technique, and results. Acta Neurochir Suppl (Wien). 1991;53:166170.

  • 8

    Cho CW, Al-Mefty O. Combined petrosal approach to petroclival meningiomas. Neurosurgery. 2002;51(3):708718.

  • 9

    Fukushima T, Day JD, Hirahara K. Extradural total petrous apex resection with trigeminal translocation for improved exposure of the posterior cavernous sinus and petroclival region. Skull Base Surg. 1996;6(2):95103.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Miller CG, van Loveren HR, Keller JT, et al. Transpetrosal approach: surgical anatomy and technique. Neurosurgery. 1993;33(3):461469.

  • 11

    Bambakidis NC, Kakarla UK, Kim LJ, et al. Evolution of surgical approaches in the treatment of petroclival meningiomas: a retrospective review. Neurosurgery. 2007;61(5)(suppl 2):202211.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Mathiesen T, Gerlich A, Kihlström L, et al. Effects of using combined transpetrosal surgical approaches to treat petroclival meningiomas. Neurosurgery. 2007;60(6):982992.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Dolenc VV. A combined epi- and subdural direct approach to carotid-ophthalmic artery aneurysms. J Neurosurg. 1985;62(5):667672.

  • 14

    Kawase T, Shiobara R, Toya S. Anterior transpetrosal-transtentorial approach for sphenopetroclival meningiomas: surgical method and results in 10 patients. Neurosurgery. 1991;28(6):869876.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15

    Tripathi M, Deo RC, Suri A, et al. Quantitative analysis of the Kawase versus the modified Dolenc-Kawase approach for middle cranial fossa lesions with variable anteroposterior extension. J Neurosurg. 2015;123(1):1422.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Troude L Jr, Carissimi M Jr, Lavieille JP, Roche PH. How I do it: the combined petrosectomy. Acta Neurochir (Wien). 2016;158(4):711715.

  • 17

    Hanakita S, Watanabe K, Champagne PO, Froelich S. How I do it: combined petrosectomy. Acta Neurochir (Wien). 2019;161(11):23432347.

  • 18

    Labib MA, Borba Moreira L, Zhao X, et al. The side door and front door to the upper retroclival region: a comparative analysis of the open pretemporal and the endoscopic endonasal transcavernous approaches. J Neurosurg. 2020;133(6):18921904.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19

    Seker A, Inoue K, Osawa S, et al. Comparison of endoscopic transnasal and transoral approaches to the craniovertebral junction. World Neurosurg. 2010;74(6):583602.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20

    Funaki T, Matsushima T, Peris-Celda M, et al. Focal transnasal approach to the upper, middle, and lower clivus. Neurosurgery. 2013;73(2 Suppl Operative):ons155ons191.

    • Search Google Scholar
    • Export Citation
  • 21

    Kotapka MJ, Kalia KK, Martinez AJ, Sekhar LN. Infiltration of the carotid artery by cavernous sinus meningioma. J Neurosurg. 1994;81(2):252255.

  • 22

    Larson JJ, van Loveren HR, Balko MG, Tew JM Jr. Evidence of meningioma infiltration into cranial nerves: clinical implications for cavernous sinus meningiomas. J Neurosurg. 1995;83(4):596599.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    DeMonte F, Smith HK, al-Mefty O. Outcome of aggressive removal of cavernous sinus meningiomas. J Neurosurg. 1994;81(2):245251.

  • 24

    Sindou M, Wydh E, Jouanneau E, et al. Long-term follow-up of meningiomas of the cavernous sinus after surgical treatment alone. J Neurosurg. 2007;107(5):937944.

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