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Middle Fossa Approach for Vestibular Schwannoma (Acoustic Neuroma) Resection

This video demonstrates the operative setup and surgical steps of a middle fossa approach for the resection of vestibular schwannoma (acoustic neuroma).

Authors:

Cameron C. Wick, MD (cameron.wick@wustl.edu) 1

Samuel L. Barnett, MD (sam.barnett@utsouthwestern.edu) 2

J. Walter Kutz Jr., MD (walter.kutz@utsouthwestern.edu) 3

Brandon Isaacson, MD (brandon.isaacson@utsouthwestern.edu) 3

1 – Department of Otolaryngology – Head and Neck Surgery, Washington University School of Medicine, St. Louis, MO

2 – Department of Neurosurgery, University of Texas Southwestern Medical Center, Dallas, TX

3- Department of Otolaryngology – Head and Neck Surgery, University of Texas Southwestern Medical Center, Dallas, TX

Middle Fossa Approach for Vestibular Schwannoma (Acoustic Neuroma) Resection
Hearing preservation approach for small tumors (< 15 mm) Patient preference with reasonable expectations
Medium to large tumors with extension into the cerebellopontine angle (CPA) No Hearing Relative Contraindications: age > 65 years, no fundal cap (tumor abuts the cochlea in the lateral internal auditory canal), poor hearing (pure-tone average worse than 50 dB or speech discrimination worse than 70%), seizure disorder
Operative surgeon is at the head of the bed. Patient is in the supine position with head rotated so the operative ear is facing up. Intraoperative monitoring of cranial nerves 7 and 8.
MRI with and without gadolinium Audiogram
Anatomy Pearls - Create large craniotomy (5 cm x 5 cm) - Arcuate eminence only predicts the superior semicircular canal 50% of the time, therefore we advocate blue-lining the canal to create a definitive landmark - Geniculate ganglion is dehiscent 5 - 15% of the time, therefore elevate dura in posterior to anterior direction - There are multiple ways to identify the internal auditory canal (IAC). After blue-lining the superior semicircular canal, we advocate for finding the IAC medially at the porus because there is more room to dissect. Other approaches include: 1. House (1961) —> Retrograde dissection from the GSPN to the labyrinthine segment of facial nerve 2. Fisch (1970) —> Dissect in a 60-degree angle from a blue-lined semicircular canal 3. Garcia-Ibanez (1972) —> IAC bisects the angle formed between the superior semicircular canal and the GSPN - Medial IAC dissection allows 270-degrees of exposure while the lateral IAC dissection only allows 90-degrees - After exposing the porus, release CSF from the posterior fossa to relax the dura and possible allow withdrawal of the retractor - Try to dissect tumor in a lateral to medial direction to prevent cochlear nerve avulsion from the lamina cribrosa
Advantages: - Provides complete exposure of the IAC and possibly allows tumor resection with hearing preservation Disadvantages: - Technically challenging because of the limited exposure and often nebulous surgical landmarks along the floor of the middle fossa - Facial nerve is positioned between the dissection approach and the tumor, therefore potentially higher rates of facial nerve weakness. - Requires retraction of the temporal lobe.
CSF leak (2-7%), facial nerve weakness/paralysis (15% immediate, 5% long-term), hearing loss (outcomes dependent on tumor size, location, nerve of origin, and pre-operative hearing), seizure, stroke, meningitis, death
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1. Kartush JM, Kemink JL, Graham MD. The arcuate eminence: Topographic orientation in middle cranial fossa surgery. Ann Otol Rhinol Laryngol. 1985;94:25-28. 2. Isaacson B, Vrabec JT. The radiographic prevalence of geniculate ganglion dehiscence in normal and congenitally thin temporal bones. Otol Neurotol. 2007;28:107-110. 3. Wade PJ, House W. Hearing preservation in patients with acoustic neuromas via the middle fossa approach. Otolaryngol Head Neck Surg. 1984;92:184-193. 4. Gantz BJ, Parnes LS, Harker LA, et al. Middle cranial fossa acoustic neuroma excision: results and complications. Ann Otol Rhinol Laryngol. 1986;95:454-459. 5. Shelton C, Brackmann DE, House WF, Hitselberger WE Middle fossa acoustic tumor surgery: Results in 106 cases. Laryngoscope. 1989;99:405-408. 6. Shelton C, Brackmann DE, House WF, Hitselberger WE. Acoustic tumor surgery. Prognostic factors in hearing conservation. Arch Otolaryngol Head Neck Surg. 1989;115:1213-1216. 7. Dubrulle F, Ernst O., Vincent C., et al. Cochlear fossa enhancement at MR evaluation of vestibular schwannoma: Correlation with success at hearing-preservation surgery. Radiology. 2000;215:458-462. 8. Meyer TA, Canty PA, Wilkinson EP, Hansen MR, Rubinstein JT, Gantz BJ. Small acoustic neuromas: surgical outcomes versus observation or radiation. Otol Neurotol. 2006;27:380-392. 9. Kutz JW Jr, Scoresby T, Isaacson B, et al. Hearing preservation using the middle fossa approach for the treatment of vestibular schwannoma. Neurosurgery. 2012;70:334-340. 10. Friedman RA, Kesser B, Brackmann DE, Fisher LM, Slattery WH, Hitselberger WE. Long-term hearing preservation after middle fossa removal of vestibular schwannoma. Otolaryngol Head Neck Surg. 2003;129:660-665. 11. Woodson EA, Dempewolf RD, Gubbels SP, et al. Long-term hearing preservation after microsurgical excision of vestibular schwannoma. Otol Neurotol. 2010;31:1144-1152. 12. Quist TS, Givens DJ, Gurgel RK, et al. Hearing preservation after middle fossa vestibular schwannoma removal: are the results durable? Otolaryngol Head Neck Surg. 2015;152:706-711.

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