Middle fossa approach for a pediatric facial nerve meningioma

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  • 1 Departments of Neurological Surgery,
  • | 2 Surgery, Division of Otolaryngology, Head and Neck Surgery, and
  • | 3 Neurosciences and Pediatrics, University of California, San Diego, California
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Pediatric cerebellopontine angle (CPA) meningiomas are extremely rare and are usually treated with a retrosigmoid surgical approach or radiation. The authors present the use of a middle fossa approach for the treatment of a symptomatic CPA meningioma in a 22-month-old female. The patient initially presented at 17 months with isolated progressive, long-standing right-sided facial weakness. MRI demonstrated a 5.0 × 5.0–mm right CPA lesion just superior to the cisternal segment of cranial nerve (CN) VII, which demonstrated growth on interval imaging. At 22 months of age she underwent a successful middle fossa craniotomy, including wide exposure of the porus acusticus, allowing for a gross-total resection with preservation of CNs VII and VIII. Pathological analysis revealed a WHO grade I meningioma. The patient remained neurologically stable on follow-up. The middle fossa approach can be used to safely access the CPA in properly selected pediatric patients.

ABBREVIATIONS

BAER = brainstem auditory evoked response; CN = cranial nerve; CPA = cerebellopontine angle; IAC = internal auditory canal.

Pediatric cerebellopontine angle (CPA) meningiomas are extremely rare and are usually treated with a retrosigmoid surgical approach or radiation. The authors present the use of a middle fossa approach for the treatment of a symptomatic CPA meningioma in a 22-month-old female. The patient initially presented at 17 months with isolated progressive, long-standing right-sided facial weakness. MRI demonstrated a 5.0 × 5.0–mm right CPA lesion just superior to the cisternal segment of cranial nerve (CN) VII, which demonstrated growth on interval imaging. At 22 months of age she underwent a successful middle fossa craniotomy, including wide exposure of the porus acusticus, allowing for a gross-total resection with preservation of CNs VII and VIII. Pathological analysis revealed a WHO grade I meningioma. The patient remained neurologically stable on follow-up. The middle fossa approach can be used to safely access the CPA in properly selected pediatric patients.

Meningiomas represent less than 3% of pediatric CNS tumors,1 and when they do occur in children, the vast majority (approximately 90%) are supratentorial.1,2 Pediatric cerebellopontine angle (CPA) meningiomas are thus exceedingly rare.3 Described treatments typically involve radiation and/or resection, most commonly via a retrosigmoid craniotomy,1 with the majority of surgically treated patients being 4 years of age or older.1,4 Although use of skull base approaches in the pediatric population is both relatively limited and potentially complicated by differences in skull base anatomy between children and adults,5–8 more complex approaches, such as a translabyrinthine craniotomy with nerve grafting due to tumor infiltration into the fallopian canal, have been reported for pediatric CPA meningiomas.4

In this paper we present the use of a middle fossa approach for the successful treatment of a symptomatic CPA meningioma in a 22-month-old, with a focus on the surgical technique due to the rarity of skull base approaches performed in this population.

Case Report

History and Examination

A 17-month-old girl presented with progressive right-sided facial weakness over approximately 8 months. At the time of neurosurgical evaluation she had House-Brackmann grade V weakness but was otherwise neurologically intact and meeting all developmental milestones. A brain MR image demonstrated a 5.0 × 5.0–mm round enhancing lesion at the right CPA, appearing to be superior to the cisternal segment of cranial nerve (CN) VII (Fig. 1A). The differential diagnosis was a choroid plexus papilloma, schwannoma, meningioma, or less likely a focal inflammatory process or vascular lesion. Brainstem auditory evoked response (BAER) testing, imaging of the remainder of the neurological axis, and CSF analysis were within normal limits.

FIG. 1.
FIG. 1.

Preoperative MRI. A: Initial axial contrasted MR image demonstrating a 5.0 × 5.0–mm round enhancing lesion (arrow) at the right CPA in a young child patient with progressive right-sided facial weakness. B: Interval imaging 3 months later demonstrated lesional growth (arrow) to 6.5 × 7.5 mm, with development of brainstem and superior cerebellar peduncle edema (not shown). The lesion appeared to be located directly superior to the cisternal segment of CN VII. Figure is available in color online only.

After neurosurgical and neurooncological evaluation, an initial conservative strategy was pursued. However, 3-month interval imaging demonstrated lesional growth to 6.5 × 7.5 mm (Fig. 1B), with development of mild surrounding edema in the brainstem and superior cerebellar peduncle. MR angiography was negative at this time. Although the patient remained neurologically stable, a surgery for diagnosis and resection of the lesion via a middle fossa approach was recommended and performed at 22 months of age.

Surgical Intervention

Following intubation, the patient was positioned supine with the head supported in a rigid head holder frame (Mayfield Infinity System, Integra LifeSciences) and turned to the left. Neurological monitoring (including CNs VII and VIII) and neuronavigation were established, with normal auditory brainstem responses noted bilaterally. After a layered opening using a reverse question-mark right-sided temporal incision, an approximately 5.0 × 5.0–cm craniotomy was created in the temporal squamosa with two-thirds of the window positioned anterior to the external auditory canal and aligned inferiorly with the middle fossa floor. The dura was elevated off of the middle fossa floor from posterior to anterior, identifying the arcuate eminence, the greater superficial petrosal nerve, and the geniculate ganglion. The superior petrosal sinus was elevated from the posterior ridge of the petrous bone. A House-Urban retractor was used to retract the temporal lobe. Using the arcuate eminence and greater superficial petrosal nerve as landmarks, drilling of the anterior and posterior petrous apex centered over the internal auditory canal (IAC) was performed using a combination of diamond burrs (Fig. 2A and B). The superior semicircular canal and IAC were skeletonized. The posterior fossa dura was decompressed, as was the dura at the porus acusticus. The postmeatal triangle was drilled to expose the dura at the posterior aspect of the IAC. Medially, 180° of dural exposure was achieved around the porus acusticus. The dura of the IAC was incised longitudinally along its posterior aspect (Fig. 2C), and the facial nerve was identified with positive stimulation.

FIG. 2.
FIG. 2.

Key intraoperative steps during right middle fossa craniotomy for lesion resection. After performing an approximately 5.0 × 5.0–cm low temporal craniotomy positioned two-thirds anterior to the external auditory canal, the dura and superior petrosal sinus were elevated off of the middle fossa floor and posterior ridge of the petrous bone, respectively. A: A House-Urban retractor was placed to elevate the temporal lobe (TL), and the arcuate eminence (#), the greater superficial petrosal nerve, and the geniculate ganglion were identified. The IAC was unroofed with diamond burrs by drilling medially in the area of the bisection of the angle formed by the superior semicircular canal (approximated by the arcuate eminence) and the greater superficial petrosal nerve (angle of aforementioned structures highlighted by dashed white lines; area to be drilled marked by dashed black oval). B: Bone removal included exposure of the posterior fossa dura medially and the anterior and posterior aspect of the IAC at the porus. C: The dura of the IAC was incised longitudinally. D: The facial nerve was identified positively (asterisk), and the lesion was visualized as an exophytic mass in close association with the superior aspect of the facial nerve (arrow). E: The lesion was removed en bloc after careful dissection from the facial nerve (asterisk), with ultrasonic aspiration used to remove a small aspect of adherent lesional tissue from the brainstem. Figure is available in color online only.

The tumor was visualized as an exophytic mass in close association with the superior aspect of the facial nerve at the CPA, with some extension into the IAC (Fig. 2D). Sharp microdissection was used to dissect around the plane of the tumor, with great care taken to preserve the thin facial nerve, which was inferior to the mass. The mass was taken out en bloc and sent for pathological analysis, with frozen sections consistent with a spindle cell benign neoplasm. A small amount of residual tumor adherent to the brainstem was then dissected carefully using a combination of microdissection and ultrasonic aspiration with variable suction. This allowed for a gross-total resection (Fig. 2E). A layered closure including a bovine pericardial dural graft was performed, with the bone replated using a titanium plating system. Neuromonitoring signals were stable throughout the procedure. The facial nerve stimulated at 0.05 mA at the beginning of the case and remained anatomically intact throughout.

Postoperative Course

The patient was admitted to the pediatric intensive care unit after surgery. She was discharged home on postoperative day 4 at her neurological baseline with no new focal deficits, and was stable on 6-month follow up. Postoperative imaging demonstrated a gross-total resection (Fig. 3), with no recurrence at 3 months and serial imaging ongoing.

FIG. 3.
FIG. 3.

Postoperative axial, postcontrast MR image demonstrating a gross-total resection, as well as expected postoperative sequelae from the right middle fossa approach. Pathology demonstrated a WHO grade I meningioma.

Pathology

Final pathological analysis revealed a WHO grade 1 meningioma (glial fibrillary acidic protein, synaptophysin, and S100 negative; EMA positive; Ki-67 index 1%–2%). There was no significant atypia, Verocay bodies, Rosenthal fibers, or Antoni A/B areas. Microarray genetic analysis was notable for a loss of chromosome 11q22.1-q24.2 encompassing 14 cancer genes including ATM.

Discussion

Although the use of skull base approaches in pediatric patients has been extensively described,4–6,9–14 they are less commonly utilized in this population due in part to differences in skull base anatomy that can affect the surgical technique.5–8 We and others have nonetheless reported the performance of anterior and/or posterior petrosal approaches for pediatric skull base lesions in patients as young as 1 year of age,6,13 without notable differences in relevant bony anatomy proportions in children versus adults. The use of a more focused middle fossa approach in pediatric patients, however, is not well described.

In planning this case, the posterolateral trajectory provided by the more commonly used retrosigmoid approach1 was believed to be suboptimal, given the imaging appearance of the tumor in close association with the superior aspect of CN VII as it exited the brainstem. In contrast, the middle fossa approach similarly preserved hearing, while providing direct visualization of the tumor and facilitating its dissection off of the facial nerve (confirmed to be below the tumor intraoperatively [Fig. 2D]) and brainstem. Although we were prepared to remove additional bone if needed from the anterior and/or posterior petrous apex, a generous bony exposure of the porus acusticus provided adequate visualization of the target area upon dural opening. This limited approach was facilitated by both the small size of the tumor and the patient’s relatively large porus acusticus, a common feature in children given their generally cone-shaped IAC.15

Regarding the timing of surgery, an initial conservative strategy was selected given the patient’s long-standing facial weakness upon neurosurgical presentation and unclear imaging diagnosis. Subsequent tumor growth necessitated treatment. Upfront radiosurgery was not pursued given the consensus on the importance of obtaining a tissue diagnosis based on a multidisciplinary case review, with the preoperative goal being a surgical cure without further neurological compromise and anatomical preservation of CN VII and the cochlear nerve. Repeat BAER testing after lesional growth was noted was not performed preoperatively given the patient’s stable clinical examination, with normal auditory brainstem responses noted and preserved intraoperatively. Although a gross-total resection was achieved in this case, aggressive resection of tumor significantly adherent to the facial nerve would not have been performed (if encountered) after histological confirmation of a benign lesion in an attempt to optimize the long-term chances of facial nerve recovery. Facial reanimation surgery has nonetheless been discussed if recovery of function does not occur. Additionally, while the patient lacked a relevant family history or other stigmata of genetic diseases such neurofibromatosis type 1 or 2, close follow-up and germline genetic testing is planned given the atypical genetic profile of the tumor.

Practical considerations for the safe performance of skull base approaches in pediatric patients are also highlighted by this case. For example, although the estimated blood loss of 150 ml would have been easily tolerated in an adult patient (occurring mainly from venous bleeding during dural exposure of the middle fossa floor), this represents nearly 20% of the blood volume in a 22-month-old, and an intraoperative transfusion was needed. Minimizing blood loss via meticulous surgical technique and working with an experienced pediatric anesthesia team is thus critical in such cases. Similarly, with the use of rigid head fixation required for neuronavigation (used sparingly herein but important if atypical anatomy is encountered), the thin skull of younger patients must be accounted for by combining rigid support with a low-pressure skull clamp to prevent iatrogenic fractures (achieved at our institution with the Mayfield Infinity system). Finally, as with adult patients, combined operations leveraging the skill sets of experienced neurootologic surgeons and neurosurgeons familiar with the chosen approach should be considered. Despite these challenges, the middle fossa approach can be safely used in properly selected pediatric patients for the resection of small CPA meningiomas or other similarly located lesions.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Rennert. Acquisition of data: Rennert. Analysis and interpretation of data: Rennert, DM Levy, Plonsker, Steinberg. Drafting the article: Rennert, DM Levy, Plonsker. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Rennert. Administrative/technical/material support: Friedman, Crawford, ML Levy. Study supervision: Friedman, ML Levy.

References

  • 1

    Liu H, Luo W, Li J, et al. Pediatric infratentorial meningiomas: a series of 19 cases and review of the literature. Childs Nerv Syst. 2017;33(5):777786.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2

    Thuijs NB, Uitdehaag BM, Van Ouwerkerk WJ, et al. Pediatric meningiomas in The Netherlands 1974-2010: a descriptive epidemiological case study. Childs Nerv Syst. 2012;28(7):10091015.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Holman MA, Schmitt WR, Carlson ML, et al. Pediatric cerebellopontine angle and internal auditory canal tumors: clinical article. J Neurosurg Pediatr. 2013;12(4):317324.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Deep NL, Gnagi SH, Carpentieri DF, et al. Facial nerve meningioma: a cause of pediatric facial weakness. Otol Neurotol. 2017;38(3):e8e12.

  • 5

    Gump WC. Meningiomas of the pediatric skull base: a review. J Neurol Surg B Skull Base. 2015;76(1):6673.

  • 6

    Klimo P Jr, Browd SR, Pravdenkova S, et al. The posterior petrosal approach: technique and applications in pediatric neurosurgery. J Neurosurg Pediatr. 2009;4(4):353362.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7

    Rennert RC, Hoshide R, Brandel MG, et al. Surgical relevance of pediatric skull base maturation for the far-lateral and extreme-lateral infrajugular transcondylar-transtubercular exposure approaches. J Neurosurg Pediatr. 2019;24(1):8591.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Scuderi AJ, Harnsberger HR, Boyer RS. Pneumatization of the paranasal sinuses: normal features of importance to the accurate interpretation of CT scans and MR images. AJR Am J Roentgenol. 1993;160(5):11011104.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9

    Alalade AF, Ogando-Rivas E, Boatey J, et al. Suprasellar and recurrent pediatric craniopharyngiomas: expanding indications for the extended endoscopic transsphenoidal approach. J Neurosurg Pediatr. 2018;21(1):7280.

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

    Brockmeyer D, Gruber DP, Haller J, et al. Pediatric skull base surgery. 2. Experience and outcomes in 55 patients. Pediatr Neurosurg. 2003;38(1):915.

  • 11

    Cavalheiro S, Yagmurlu K, da Costa MD, et al. Surgical approaches for brainstem tumors in pediatric patients. Childs Nerv Syst. 2015;31(10):18151840.

  • 12

    Patel AJ, Gressot LV, Cherian J, et al. Far lateral paracondylar versus transcondylar approach in the pediatric age group: CT morphometric analysis. J Clin Neurosci. 2014;21(12):21942200.

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

    Rennert RC, Hoshide R, Calayag M, et al. Extended middle fossa approach to lateralized pontine cavernomas in children. J Neurosurg Pediatr. 2018;21(4):384388.

  • 14

    Venkataramana NK, Anantheswar YN. Pediatric anterior skull base tumors: our experience and review of literature. J Pediatr Neurosci. 2010;5(1):111.

  • 15

    Marques SR, Ajzen S, D Ippolito G, et al. Morphometric analysis of the internal auditory canal by computed tomography imaging. Iran J Radiol. 2012;9(2):7178.

Illustration from Aldave (pp 572–577). Images created by Katherine Relyea and printed with permission from Baylor College of Medicine.

  • View in gallery

    Preoperative MRI. A: Initial axial contrasted MR image demonstrating a 5.0 × 5.0–mm round enhancing lesion (arrow) at the right CPA in a young child patient with progressive right-sided facial weakness. B: Interval imaging 3 months later demonstrated lesional growth (arrow) to 6.5 × 7.5 mm, with development of brainstem and superior cerebellar peduncle edema (not shown). The lesion appeared to be located directly superior to the cisternal segment of CN VII. Figure is available in color online only.

  • View in gallery

    Key intraoperative steps during right middle fossa craniotomy for lesion resection. After performing an approximately 5.0 × 5.0–cm low temporal craniotomy positioned two-thirds anterior to the external auditory canal, the dura and superior petrosal sinus were elevated off of the middle fossa floor and posterior ridge of the petrous bone, respectively. A: A House-Urban retractor was placed to elevate the temporal lobe (TL), and the arcuate eminence (#), the greater superficial petrosal nerve, and the geniculate ganglion were identified. The IAC was unroofed with diamond burrs by drilling medially in the area of the bisection of the angle formed by the superior semicircular canal (approximated by the arcuate eminence) and the greater superficial petrosal nerve (angle of aforementioned structures highlighted by dashed white lines; area to be drilled marked by dashed black oval). B: Bone removal included exposure of the posterior fossa dura medially and the anterior and posterior aspect of the IAC at the porus. C: The dura of the IAC was incised longitudinally. D: The facial nerve was identified positively (asterisk), and the lesion was visualized as an exophytic mass in close association with the superior aspect of the facial nerve (arrow). E: The lesion was removed en bloc after careful dissection from the facial nerve (asterisk), with ultrasonic aspiration used to remove a small aspect of adherent lesional tissue from the brainstem. Figure is available in color online only.

  • View in gallery

    Postoperative axial, postcontrast MR image demonstrating a gross-total resection, as well as expected postoperative sequelae from the right middle fossa approach. Pathology demonstrated a WHO grade I meningioma.

  • 1

    Liu H, Luo W, Li J, et al. Pediatric infratentorial meningiomas: a series of 19 cases and review of the literature. Childs Nerv Syst. 2017;33(5):777786.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2

    Thuijs NB, Uitdehaag BM, Van Ouwerkerk WJ, et al. Pediatric meningiomas in The Netherlands 1974-2010: a descriptive epidemiological case study. Childs Nerv Syst. 2012;28(7):10091015.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Holman MA, Schmitt WR, Carlson ML, et al. Pediatric cerebellopontine angle and internal auditory canal tumors: clinical article. J Neurosurg Pediatr. 2013;12(4):317324.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Deep NL, Gnagi SH, Carpentieri DF, et al. Facial nerve meningioma: a cause of pediatric facial weakness. Otol Neurotol. 2017;38(3):e8e12.

  • 5

    Gump WC. Meningiomas of the pediatric skull base: a review. J Neurol Surg B Skull Base. 2015;76(1):6673.

  • 6

    Klimo P Jr, Browd SR, Pravdenkova S, et al. The posterior petrosal approach: technique and applications in pediatric neurosurgery. J Neurosurg Pediatr. 2009;4(4):353362.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7

    Rennert RC, Hoshide R, Brandel MG, et al. Surgical relevance of pediatric skull base maturation for the far-lateral and extreme-lateral infrajugular transcondylar-transtubercular exposure approaches. J Neurosurg Pediatr. 2019;24(1):8591.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Scuderi AJ, Harnsberger HR, Boyer RS. Pneumatization of the paranasal sinuses: normal features of importance to the accurate interpretation of CT scans and MR images. AJR Am J Roentgenol. 1993;160(5):11011104.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9

    Alalade AF, Ogando-Rivas E, Boatey J, et al. Suprasellar and recurrent pediatric craniopharyngiomas: expanding indications for the extended endoscopic transsphenoidal approach. J Neurosurg Pediatr. 2018;21(1):7280.

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

    Brockmeyer D, Gruber DP, Haller J, et al. Pediatric skull base surgery. 2. Experience and outcomes in 55 patients. Pediatr Neurosurg. 2003;38(1):915.

  • 11

    Cavalheiro S, Yagmurlu K, da Costa MD, et al. Surgical approaches for brainstem tumors in pediatric patients. Childs Nerv Syst. 2015;31(10):18151840.

  • 12

    Patel AJ, Gressot LV, Cherian J, et al. Far lateral paracondylar versus transcondylar approach in the pediatric age group: CT morphometric analysis. J Clin Neurosci. 2014;21(12):21942200.

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

    Rennert RC, Hoshide R, Calayag M, et al. Extended middle fossa approach to lateralized pontine cavernomas in children. J Neurosurg Pediatr. 2018;21(4):384388.

  • 14

    Venkataramana NK, Anantheswar YN. Pediatric anterior skull base tumors: our experience and review of literature. J Pediatr Neurosci. 2010;5(1):111.

  • 15

    Marques SR, Ajzen S, D Ippolito G, et al. Morphometric analysis of the internal auditory canal by computed tomography imaging. Iran J Radiol. 2012;9(2):7178.

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