Foramen ovale puncture, lesioning accuracy, and avoiding complications: microsurgical anatomy study with clinical implications

Laboratory investigation

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Foramen ovale (FO) puncture allows for trigeminal neuralgia treatment, FO electrode placement, and selected biopsy studies. The goals of this study were to demonstrate the anatomical basis of complications related to FO puncture, and provide anatomical landmarks for improvement of safety, selective lesioning of the trigeminal nerve (TN), and optimal placement of electrodes.


Both sides of 50 dry skulls were studied to obtain the distances from the FO to relevant cranial base references. A total of 36 sides from 18 formalin-fixed specimens were dissected for Meckel cave and TN measurements. The best radiographic projection for FO visualization was assessed in 40 skulls, and the optimal trajectory angles, insertion depths, and topographies of the lesions were evaluated in 17 specimens. In addition, the differences in postoperative pain relief after the radiofrequency procedure among different branches of the TN were statistically assessed in 49 patients to determine if there was any TN branch less efficiently targeted.


Most severe complications during FO puncture are related to incorrect needle placement intracranially or extracranially. The needle should be inserted 25 mm lateral to the oral commissure, forming an approximately 45° angle with the hard palate in the lateral radiographic view, directed 20° medially in the anteroposterior view. Once the needle reaches the FO, it can be advanced by 20 mm, on average, up to the petrous ridge. If the needle/radiofrequency electrode tip remains more than 18 mm away from the midline, injury to the cavernous carotid artery is minimized. Anatomically there is less potential for complications when the needle/radiofrequency electrode is advanced no more than 2 mm away from the clival line in the lateral view, when the needle pierces the medial part of the FO toward the medial part of the trigeminal impression in the petrous ridge, and no more than 4 mm in the lateral part. The 40°/45° inferior transfacial–20° oblique radiographic projection visualized 96.2% of the FOs in dry skulls, and the remainder were not visualized in any other projection of the radiograph. Patients with V1 involvement experienced postoperative pain more frequently than did patients with V2 or V3 involvement. Anatomical targeting of V1 in specimens was more efficiently achieved by inserting the needle in the medial third of the FO; for V2 targeting, in the middle of the FO; and for V3 targeting, in the lateral third of the FO.


Knowledge of the extracranial and intracranial anatomical relationships of the FO is essential to understanding and avoiding complications during FO puncture. These data suggest that better radiographic visualization of the FO can improve lesioning accuracy depending on the part of the FO to be punctured. The angles and safety distances obtained may help the neurosurgeon minimize complications during FO puncture and TN lesioning.

Abbreviations used in this paper:AP = anteroposterior; FO = foramen ovale; TN = trigeminal nerve.

Article Information

Current affiliation for Drs. Mericle and Ulm: HW Neurological Institute, Nashville, Tennessee.

Current affiliation for Dr. Peris-Celda: Department of Neurosurgery, University of Florida, Gainesville, Florida.

Address correspondence to: Maria Peris-Celda, M.D., Ph.D., Department of Neurosurgery, School of Medicine, LSU Health Sciences Center, 2020 Gravier Street, 7th Floor, New Orleans, Louisiana 70112. email:

Please include this information when citing this paper: published online April 19, 2013; DOI: 10.3171/2013.1.JNS12743.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Measurements of the osseous structures surrounding the FO from the exocranial surface of the skull base. A: Photograph of a dry skull with labels indicating diameters (A–D) and distances (1–7, μ). A = diameters of the FO; B = diameters of the foramen lacerum; C = diameters of the carotid foramen; D = diameters of the jugular foramen. 1 = distance from the FO to the mandibular fossa; 2 = distance from the FO to the foramen spinosum; 3 = distance from the FO to the jugular foramen; 4 = distance from the FO to the carotid foramen; 5 = distance from the FO to the foramen lacerum; 6 = distance from the base of the pterygoid processes to the foramen lacerum; 7 = distance from μ to the FO. μ = distance from the external prominence above the second or third molar of the maxilla to the cranial base adjacent to the FO in a line parallel to the midline; CF = carotid foramen; FL = foramen lacerum; FS = foramen spinosum; JF = jugular foramen; MF = mandibular fossa. B and C: Lateral (B) and inferior (C) views of the angle measurements performed on the dry skull bases: α = angle between a needle located over the external prominence above the second or third molar of the maxilla to the FO, and a line traced over the inferior part of the maxilla in the lateral view; β = angle between the needle and a line parallel to the midline in an inferior view. The V3 and pars nervosa of the jugular foramen are shown in yellow, carotid artery in red, and jugular vein in blue with molding material.

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    Photographs showing dissection of the Meckel cave and cavernous sinus on the right side. A–C: Lateral (A), oblique (B), and posterior (C) views of the Meckel cave and cavernous sinus with the periosteal layer of the dura mater intact. D: Dissection after removing the periosteal layer of the dura mater. E: Illustration showing measurements in the middle fossa: 1 = distance from the FO to the posterior clinoid process; 2 = distance from the FO to the exit of the internal carotid artery from the petrous bone (not shown); 3 = distance from the FO to the middle part of V1 in the FO–posterior clinoid line; 4 = distance from the FO to the middle part of V2 in the FO–posterior clinoid line; 5 = distance from the FO to the common root of the TN in the middle fossa; 6 = distance from the middle part of the FO to the petrous ridge. Bas. A = basilar artery; CA = internal carotid artery; CN = cranial nerve; GSPN = greater superficial petrosal nerve; Hyp. = hypophyseal gland; Midd. Men. A. = middle meningeal artery; ON = optic nerve; PCA = posterior cerebral artery; Post. C. = posterior clinoid; SCA = superior cerebellar artery; Tent. = tentorium.

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    Anteroposterior (A) and lateral (B) radiographic views of the different angles and trajectories of the FO puncture in specimens. The trajectories were studied after insertion of lumbar puncture needles and have been highlighted with different colors. Two extradural trajectories were measured: 1) the medial trajectory, represented by a green line passing through the retrogasserian portion in the medial part of the common root of the TN in the trigeminal impression of the petrous ridge, and the medial part of the FO; and 2) the lateral trajectory, represented by a purple line passing through the lateral part of the common root of the TN in the trigeminal impression of the petrous ridge, and the lateral part of the FO. A shorter needle was placed between the FO and posterior clinoid process for additional measurements (blue lines). C: Photograph showing dissection of the cavernous sinus and Meckel cave, in which the medial and lateral trajectories have been represented. CA = carotid artery; CN = cranial nerve; GSPN = greater superficial petrosal nerve; Hyp = hypophyseal gland; Midd. Men. A. = middle meningeal artery; ON = optic nerve; PCA = posterior cerebral artery; Post. C. = posterior clinoid.

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    Photographs showing FO puncture and anatomical dissection of the percutaneous route. A: Oblique view. To reach the FO (black oval), the needle should be placed from the entry point, 2.5–3 cm lateral to the oral commissure to the intersection of a coronal plane 3 cm anterior to the tragus, a sagittal plane in the medial pupillary line, and an axial plane parallel to the skull base (Harthel technique). B: Trajectory of the needle to reach the FO (black oval) in the lateral view. In this specimen, the zygomatic arch, the squamous part of the temporal bone, and the lateral wall of the orbit have been removed. Bucc. M. = buccinator muscle; Facial A. = facial artery; Infraorb. N. = infraorbital nerve; Mass. M. = masseter muscle; Ment. N. = mentonian nerve; Orb. Oris M. = orbicularis oris muscle; Parotid G. = parotid gland; Sten. D. = Stensen duct; Temp. M. = temporalis muscle; Temp. L. = temporal lobe.

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    Dissection of the infratemporal fossa after removal of the ascending ramus of the mandible, masseter, and temporalis muscles. The middle cranial fossa and orbit have been dissected. A: The internal maxillary artery and pterygoid venous plexus are seen in depth, as well as V3 branches (buccal, lingual, inferior alveolar, masseteric, deep temporal, and auriculotemporal nerves). The lateral and superior walls of the orbit have been removed to show the relationship of the middle fossa with the orbit through the superior orbital fissure, and the infratemporal fossa with the orbit through the inferior orbital fissure. After removing the temporal lobe and dura mater of the middle fossa and cavernous sinus, the TN is shown as well as its relationships with the third and fourth cranial nerves and the carotid artery. B: Closer view of the infratemporal fossa, in which the pterygoid venous plexus has been removed to show the internal maxillary artery and its branches. C: Oblique view of the same dissection with the needle inserted pointing toward the retrogasserian part of the TN. D: Closer view of the TN in the Meckel cave, cavernous sinus, and their relationship with the orbit and infratemporal fossa. The triangular area shows the triangular plexus (TP), the retrogasserian portion of the TN in the Meckel cave. E: Dissection of the middle fossa and deep infratemporal fossa. View after drilling the middle fossa floor up to the FO and the anterolateral triangle of the middle fossa. The sphenoid sinus has been opened. F: After the resection of the lateral pterygoid muscle, V3 branches from the FO can be visualized. The Stensen duct, internal maxillary artery, and pterygoid venous plexus might be in the path of the needle. A = artery; Auric. Temp. N. = auriculotemporal nerve; Buccal A. N. = buccal artery and nerve; CA = carotid artery; CN = cranial nerve; Inf. Alv. A. N. = inferior alveolar artery and nerve; Infraorb. N. = infraorbital nerve; Int. Max. A. = internal maxillary artery; Lat. Rectus M. = lateral rectus muscle; Lat. Pter. M. = lateral pterygoid muscle; Lingual N. = lingual nerve; Mand. Cond. = mandibular condyle; Mass. A. N. = masseteric artery and nerve; Med. Pter. M. = medial pterygoid muscle; N. = nerve; Orb. Oculi = orbicularis oculi muscle; Orb. Oris = orbicularis oris muscle; Post. Sup. Alv. A. N. = posterior superior alveolar artery and nerves; Pter. Plex. = pterygoid venous plexus; Sph. Sin. = sphenoid sinus; Sten. D. = Stensen duct; Temp. A. N. = deep temporal artery and nerve.

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    Photographs showing FO puncture and the internal carotid artery. A: Oblique lateral view of a representation with molding material of the carotid artery (CA), V1, V2, and V3 in a dry skull. The retrogasserian portion of the TN lies over the trigeminal impression (Trig. Impress.). B: Skull with molding material representing the previous structures and the optic nerve (ON). D = distance from midline to the theoretical location of the petrolingual ligament (PLL) between the petrous bone and the lingual process of the sphenoid bone. Midd. Men. A. = middle meningeal artery. C: According to our data, it is possible to puncture the CA in the cavernous sinus in 29 (36.7%) of 79 sides of skulls with an excessive medially directed puncture (shown), which can lead to a carotid-cavernous fistula. D and E: It is also possible to puncture the CA in the horizontal petrous segment in 24 (30.4%) of 79 sides of skulls (D), but with an extremely superior entry point in the facial region (shown) almost touching the zygoma (E).

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    Visualization of the FO using radiography. A: Radiographic view of the 40°/45° inferior transfacial–20° oblique projection. The FO (dashed elliptic shape, yellow arrow) can be identified between the line formed by the inferior line of the zygomamaxilla and the anterior line of the mandible. Adjusting the transfacial angle, the setting sun sign might be observed (line of the petrous ridge in the middle of the FO, not shown). B: Graphic illustration of these angles. C–E: Anatomical correlation of the radiograph visualizing the FO (arrows) in the 40°/45° inferior transfacial–20° oblique view in different anatomical types. In the most common view of the FO (C), note that the petrous ridge can be observed in the middle of the FO (correlation of setting sun sign). The next image (D) shows a specimen in which the FO was visualized with difficulties in the radiograph corresponding to a narrow, thick osseous canal. In the last image (E), the FO was not observed in any projection of the radiograph in this specimen due to the thickness of the pterygoid base and orientation of the FO canal.

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    Puncture in the medial, middle, and lateral thirds of the FO. A: Puncture in the middle part of the FO with the electrode curved up at +5 mm from the clival line. Note that the electrode anatomically misses most V1 fibers. Further advancement of the needle would probably not allow the complete lesioning of V1 fibers, whereas a more medial puncture within the FO would probably be more efficient in targeting V1. B: Graphic representation in a photograph of the TN of all the punctures performed in different anatomical specimens. Three parts of the FO were studied (medial, middle, and lateral) with the electrode tip located at +5, 0, and −5 mm from the clival line visualized on radiography, with curved Tew electrode up and down (quarter moon shape) and the straight electrode (long oval shape). The punctures performed in the medial portion are represented in blue, punctures in the middle portion in green, and in the lateral portion of the FO in red. Dots represent when the electrode was anatomically located in the gasserian ganglion (GG, shaded) of the TN. At −5 mm from the clival line, most electrodes were anatomically located in the gasserian ganglion. Note that the medial puncture reached V1 more efficiently than middle and lateral punctures.

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    Examples of incorrect placement of the needle in a 40°/45° inferior transfacial–20° oblique radiographic view (left column), with corresponding anatomical (center column) and lateral views (right column). The white dashed ellipse and arrow indicate the FO on the radiograph, and the yellow molding material indicates V3 in the FO in dry skulls. A–C: Needle in the orbit; note that on the radiograph, the FO, although posterior, is superimposed to this trajectory. D–F: Needle in the foramen lacerum; a lateral view (F) would not identify this misplacement. G–I: Needle injuring the carotid artery in the carotid foramen. J–L: Needle injuring the internal jugular vein, close to the jugular foramen.

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    Inferior view of the skull base and anatomical structures surrounding the third division of the TN that can be potentially injured with an incorrect puncture. Auric. Temp. N. = auriculotemporal nerve; CA = carotid artery; Chor. Tym. N. = chorda tympani nerve; CN = cranial nerve; Eust. T. = eustachian tube; Great. Pal. A. N. = greater palatine artery and nerve; Inf. Alv. N. = inferior alveolar nerve; Int. Max. A. = internal maxillary artery; Jug. V. = jugular vein; Lesser Pal. N. = lesser palatine nerve; Midd. Men. A. = middle meningeal artery; Pter. M. = pterygoid muscle; T.M.J. = temporomandibular joint.

  • View in gallery

    Relationships of the temporal lobe and mesial structures with the TN, carotid artery (CA), and third and fourth cranial nerves (CN). After piercing the dura mater with the needle, the FO electrodes are positioned in the ambient cistern in contact with the mesial temporal structures. Hyp. = hypophyseal gland; ON = optic nerve; PCA = posterior cerebral artery; SCA = superior cerebellar artery; Temp. L. = temporal lobe.



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