Vestibular schwannoma

Overview

A vestibular schwannoma (historically and commonly referred to as an acoustic neuroma) is a benign (non-cancerous), typically slow-growing tumor that develops on the vestibulocochlear nerve (Cranial Nerve VIII). This nerve is responsible for transmitting hearing and balance information from the inner ear to the brain.

Despite the term “tumor” often invoking fear of malignancy, vestibular schwannomas do not spread (metastasize) to other parts of the body. However, their location within the narrow internal auditory canal (IAC) and the cerebellopontine angle (CPA)—a tight space at the base of the brain—means that even a small growth can compress critical neurological structures, leading to significant functional impairment.

These tumors arise from Schwann cells, the specialized glial cells that produce the myelin sheath insulating peripheral nerves. While they can occur sporadically (unilaterally) in 95% of cases, bilateral vestibular schwannomas are the hallmark of a genetic disorder called Neurofibromatosis Type 2 (NF2).

Vestibular schwannoma is a manageable condition. With modern diagnostic imaging and a range of treatment paradigms—from active surveillance to microsurgery and stereotactic radiosurgery—long-term outcomes are generally excellent, with a primary focus on preserving facial nerve function and, where possible, hearing.

Epidemiology and Risk Factors

Anatomy and Pathophysiology: How Does It Look?

Understanding the appearance and growth pattern of a vestibular schwannoma is essential for grasping why specific symptoms occur and why treatment decisions are nuanced.

1. Cellular Origin: The Schwann Cell

The tumor originates from the Schwann cells forming the myelin sheath of the vestibular nerve (superior or inferior division), not the cochlear nerve. This is why “acoustic neuroma” is a misnomer—it is a vestibular schwannoma. Microscopically, these tumors exhibit two distinct histological patterns (Antoni A and Antoni B), often with Verocay bodies (palisading nuclei), though the patient never sees this; it confirms the diagnosis for the pathologist.

2. Gross Morphology: The “Ice Cream Cone” Shape

The classic vestibular schwannoma has a distinctive dumbbell or “ice cream cone” configuration dictated by the anatomy of the internal auditory canal (IAC) and the porus acusticus (the opening of the IAC into the brain cavity).

3. Vascular Supply

The tumor derives its blood supply primarily from the anterior inferior cerebellar artery (AICA) via the internal auditory artery (labyrinthine artery). Additional feeders may come from the petrosal branch of the middle meningeal artery or the basilar artery. Preservation of the AICA and the labyrinthine artery is critical during surgery to maintain hearing and facial nerve viability.

4. Growth Patterns

• Intracanalicular: Confined to the IAC (< 1.5 cm).
• Small: < 1.5 cm CPA extension.
• Medium: 1.5 – 2.5 cm CPA extension.
• Large: 2.5 – 4.0 cm CPA extension.
• Giant: > 4.0 cm CPA extension (causes significant brainstem displacement, hydrocephalus risk).
• Note: Growth is typically linear (1–2 mm/year), but “growth spurts” and periods of dormancy are common. Cystic degeneration or intratumoral hemorrhage can cause sudden symptom onset.

5. Imaging Appearance (MRI with Gadolinium)

This is the gold standard for “how it looks” clinically.

• T1-weighted (Post-Contrast): Intense, homogeneous enhancement (bright white) in solid tumors. Cystic areas appear dark (fluid signal).
• T2-weighted: Heterogeneous signal; solid components are iso- to hypointense relative to brain; cysts are hyperintense (bright).
• “Dural Tail” Sign: Occasionally, the dura mater thickens and enhances adjacent to the tumor (reactive, not invasion).
• Differential Diagnosis on Imaging: Meningioma (broader base, calcifications, dural tail), Epidermoid cyst (restricted diffusion on DWI), Arachnoid cyst (CSF signal), Facial nerve schwannoma (enlarged facial nerve canal).

Symptoms: Clinical Presentation

Symptoms correlate with tumor size, location, and the specific nerves compressed. They are often insidious, leading to an average diagnostic delay of 2–4 years.

1. Auditory Symptoms (The “Sentinel” Signs)

Present in >95% of patients at diagnosis.

• Sensorineural Hearing Loss (SNHL):
• Usually unilateral, progressive, high-frequency initially.
• May be sudden (10–15% of cases) due to vascular compromise or intratumoral hemorrhage.
• Asymmetric hearing loss on audiogram is the #1 screening trigger for MRI.
• Tinnitus:
• High-pitched ringing, buzzing, or roaring in the affected ear.
• Often precedes noticeable hearing loss.
• Can be the only symptom in small tumors.
• Speech Discrimination Disproportionate to Pure-Tone Loss:
• “I can hear you, but I can’t understand you.” Poor word recognition scores (WRS) relative to the pure-tone average (PTA) suggest retrocochlear pathology (nerve/tumor) rather than cochlear (inner ear) damage.

2. Vestibular (Balance) Symptoms

• Chronic Disequilibrium/Imbalance: More common than true vertigo. Patients feel “off,” “unsteady in the dark,” or “veering to one side.”
• Episodic Vertigo: Less common; mimics Ménière’s disease (fluctuating hearing + vertigo + fullness).
• Compensation: The central nervous system often compensates for the slow vestibular nerve destruction, masking severity until the tumor is large or the contralateral system fails.

3. Facial Nerve (CN VII) Symptoms

• Early/Small Tumors: Often asymptomatic despite compression. The facial nerve is remarkably resistant to slow stretch.
• Twitching (Facial Myokymia): Fine, rippling contractions.
• Weakness/Palsy: Rare at presentation (< 5% for tumors < 2.5 cm). Indicates either large tumor, rapid growth, or pre-existing vulnerability. Acute facial palsy requires urgent exclusion of malignancy or stroke.

4. Trigeminal Nerve (CN V) Symptoms

• Facial Numbness/Hypesthesia: Typically in the V1 (ophthalmic) and V2 (maxillary) distributions (forehead, cheek).
• Loss of Corneal Reflex: Danger sign—patient cannot blink when eye touched; risk of corneal ulcer.
• Trigeminal Neuralgia: Paroxysmal, lancinating facial pain (less common than in primary trigeminal neuralgia).

5. Brainstem Compression & Hydrocephalus (Large/Giant Tumors > 3 cm)

• Headache: Occipital or retroauricular; worse with Valsalva (coughing/straining).
• Gait Ataxia: Wide-based, staggering walk (cerebellar compression).
• Hydrocephalus: Obstruction of CSF flow at the foramen of Luschka/Magendie.
• Symptoms: Morning headache, nausea/vomiting, papilledema (swollen optic nerves), cognitive decline, urinary incontinence.
• Lower Cranial Nerve Deficits (CN IX, X, XI): Dysphagia (swallowing difficulty), hoarseness (vocal cord paralysis), aspiration risk, shoulder weakness (trapezius/sternocleidomastoid).
• Brainstem Compression: Long tract signs (weakness/spasticity in limbs), altered consciousness (late/emergency).

6. Neurofibromatosis Type 2 (NF2) Specifics

• Bilateral vestibular schwannomas (diagnostic criteria).
• Earlier onset (teens/20s).
• Associated tumors: Meningiomas, ependymomas, peripheral schwannomas, cataracts (juvenile posterior subcapsular).
• Higher risk of multifocal disease and treatment morbidity.

Diagnostic Workup

1. Audiometry (The Gatekeeper)

2. Auditory Brainstem Response (ABR) / BAER

• Wave I: Normal (cochlear function intact).
• Wave III & V: Prolonged latency (I-III, I-V, III-V interpeak latency increased).
• Asymmetry: Interaural latency difference (I-V) > 0.2–0.3 ms is abnormal.
• Role: Screening tool historically; now largely superseded by MRI but useful if MRI contraindicated.

3. Vestibular Testing (VNG/vHIT/VEMP)

• Videonystagmography (VNG): Reduced caloric response (canal paresis > 20-25%) on tumor side. Direction-fixed nystagmus beating away from lesion.
• Video Head Impulse Test (vHIT): Reduced VOR gain on affected side (superior/inferior vestibular nerve specific).
• VEMPs: Cervical (cVEMP) assesses saccule/inferior nerve; Ocular (oVEMP) assesses utricle/superior nerve. Helpful for surgical planning (identifying which division is tumor origin).

4. Neuroimaging: The Gold Standard

Gadolinium-Enhanced MRI of the Internal Auditory Canals (IAC Protocol) with Thin-Cut T2 (CISS/FIESTA/3D-FLAIR).

• Sensitivity/Specificity: > 99% / > 99% for tumors > 3-4 mm.
• Protocol Essentials:
• Axial/Coronal T1 post-contrast (3mm or < 1mm slices).
• High-resolution T2 (0.6–0.8mm) for CSF-tumor interface, nerve separation, cyst detection.
• Diffusion Weighted Imaging (DWI) to rule out epidermoid.
• CT Scan: Reserved for surgical planning (bone anatomy, IAC width, sigmoid sinus position) or if MRI contraindicated (pacemaker). Shows bony erosion/widening of IAC.

Management Strategies: A Multidisciplinary Decision

There is no single “best” treatment. The decision is shared between the patient, neurotologist, neurosurgeon, and radiation oncologist, based on the “Three Pillars”:

1. Tumor Characteristics: Size, growth rate, cystic vs. solid, brainstem contact.
2. Patient Factors: Age, comorbidities, life expectancy, hearing status (serviceable vs. non-serviceable), anxiety preference.
3. Provider Expertise: Institutional volume and surgeon/facility track record (volume-outcome relationship is strong).

Option 1: Active Surveillance (“Watch and Wait” / “Scan and Wait”)

Indications:

• Small, intracanalicular tumors (< 1.5–2 cm).
• Asymptomatic or mild symptoms (tinnitus only, stable hearing).
• Elderly or comorbid patients (life expectancy < tumor doubling time).
• Only-hearing ear (attempt to preserve natural hearing as long as possible).
• Patient preference to avoid intervention risks.

Protocol:

• Baseline MRI at 3–6 months (confirm stability).
• Serial MRI: Annually for 3–5 years, then every 2 years if stable.
• Serial Audiograms: Every 6–12 months.
• Trigger for Intervention: Radiographic growth (> 2 mm linear growth or volume doubling), serviceable hearing loss deterioration, new/worsening brainstem compression.

Pros: Zero procedural risk; preserves current hearing/facial function longest.

Cons: Anxiety (“scanxiety”); risk of sudden growth/hemorrhage; hearing usually declines naturally over time; tumor harder to treat if it grows large.

Option 2: Stereotactic Radiosurgery (SRS) / Stereotactic Radiotherapy (SRT)

Modalities: Gamma Knife, CyberKnife, LINAC-based (Novalis, TrueBeam).

Mechanism: High-dose, conformal radiation → DNA damage in Schwann cells → Tumor growth arrest (stasis) + vascular occlusion → Long-term control. Does not remove the tumor.

Indications:

• Small-to-Medium tumors (< 2.5–3 cm CPA diameter).
• No significant brainstem compression (cisternal CSF margin preferred).
• Patients unfit for surgery or refusing surgery.
• Residual/recurrent tumor post-surgery.
• NF2 patients (controversial; risk of malignant transformation/radiation-induced neoplasia higher).

Dosing Paradigms (Evolving Lower for Hearing Preservation):

Outcomes:

• Tumor Control: > 95% at 10–15 years (growth arrest/shrinkage).
• Facial Nerve Preservation: > 95% (House-Brackmann Grade I-II).
• Hearing Preservation: Highly variable (depends on baseline hearing, cochlear dose, tumor size). Cochlear dose < 4–5 Gy correlates strongly with preservation.
• Delayed Effects: Transient swelling (6–18 mo) causing temporary symptom flare; rare radiation-induced necrosis (1–2%); theoretical risk of secondary malignancy (< 0.5% at 20 yrs).

Option 3: Microsurgical Resection

Goal: Total resection with facial nerve preservation (HB Grade I/II). Hearing preservation is secondary but attempted if preoperative hearing is serviceable (AAO-HNS Class A/B).

References

Intraoperative Neurophysiological Monitoring (IONM) — Standard of Care

• Facial Nerve (CN VII): Free-run EMG + Triggered EMG (stimulated threshold < 0.05–0.1 mA). Essential.
• Cochlear Nerve (CN VIII): Compound Action Potential (CAP) / Electrocochleography (ECoG) / ABR. For hearing preservation cases.
• Brainstem Auditory Evoked Potentials (BAEP): Brainstem integrity.
• Lower Cranial Nerves (CN IX, X, XI): EMG monitoring for large tumors.
• Somatosensory/Motor Evoked Potentials (SSEP/MEP): For giant tumors with brainstem compression.

Extent of Resection

1. Gross Total Resection (GTR): No residual on post-op MRI. Standard goal.
2. Near-Total Resection (NTR): Tiny residual capsule left on facial nerve to preserve anatomy/function. Very low regrowth rate (< 5%).
3. Subtotal Resection (STR): Significant residual left intentionally (e.g., adherent to brainstem). Requires adjuvant SRS.

Postoperative Course & Complications

• ICU/Step-down: 1–2 nights (BP control, neuro checks).
• Hospital Stay: 3–5 days typically.
• CSF Leak: 5–15% (higher in translab/giant tumors). Managed with lumbar drain, re-exploration, or fat graft.
• Facial Nerve Outcome:
• Immediate HB Grade I/II: 70–90% (size dependent).
• Delayed recovery (weeks-months) common if nerve anatomically intact.
• Eye Care Critical: Lubrication, taping, tarsorrhaphy, gold weight if permanent palsy.
• Hearing Outcome: Preserved only if preop serviceable + CAPs maintained + small tumor + middle fossa/retrosigmoid approach. Success ~30-60%.
• Balance Rehab: Vestibular therapy essential for central compensation.

Comparative Outcomes Summary

Special Populations & Scenarios

1. Neurofibromatosis Type 2 (NF2)

• Genetics: Autosomal dominant; NF2 gene (Merlin protein) on 22q.
• Management Philosophy: “Functional Preservation > Total Resection.”
• Surgery: Often “hearing preservation” or “auditory brainstem implant (ABI)” placement at time of tumor debulking.
• Radiosurgery: Used cautiously; higher risk of cyst formation, edema, and malignant transformation.
• Medical Therapy: Bevacizumab (Anti-VEGF) – FDA approved for NF2-related VS with hearing loss. Can shrink tumors / improve hearing in ~30-50%. Requires multidisciplinary NF2 clinic.

2. “Only Hearing Ear” / Serviceable Hearing

• Observation often first line to maximize time with natural hearing.
• SRS preferred over surgery if growth documented (lower facial nerve risk, reasonable hearing preservation).
• Surgery (Middle Fossa/Retrosigmoid) only if brainstem compression or patient chooses.

3. Pregnancy

• Hormonal influence (progesterone/estrogen receptors on tumor) may accelerate growth.
• MRI without Gadolinium (T2 CISS/FIESTA only) safe for monitoring.
• Treatment deferred unless brainstem compression/hydrocephalus (emergency surgery in 2nd trimester preferred).

4. Pediatric VS

• Extremely rare (< 5% of cases).
• High suspicion for NF2 (genetic counseling mandatory).
• Surgery preferred over SRS (long-term radiation risks in developing brain).

Rehabilitation and Quality of Life (QoL)

1. Hearing Rehabilitation

• CROS Hearing Aid / Bone Anchored Hearing Aid (BAHA): Routes sound from deaf side to good ear. Good for localization? No. Good for “head shadow” effect? Yes.
• Contralateral Routing of Signal (CROS): Non-surgical.
• Cochlear Implant (CI): Only if cochlear nerve intact (rare post-surgery/SRS; possible in NF2 with ABI).
• Auditory Brainstem Implant (ABI): For NF2 patients with bilateral nerve sacrifice. Open-set speech perception variable; excellent environmental awareness.

2. Vestibular Rehabilitation Therapy (VRT)

• Essential post-surgery (acute vestibular loss) and for chronic imbalance (observation/SRS).
• Exercises: Gaze stabilization (VOR x1, x2), habituation, balance training (static/dynamic), gait training.
• Central Compensation: Brain learns to rely on vision/proprioception. Faster with early, consistent VRT.

3. Facial Reanimation (If Permanent Palsy)

• Static Procedures: Gold weight upper lid, palpebral spring, static slings (fascia lata), brow lift.
• Dynamic Procedures: Hypoglossal-facial anastomosis (XII-VII), Masseteric-facial transfer (V3-VII), Cross-facial nerve graft (CFNG) + Gracilis free flap (gold standard for smile).
• Botulinum Toxin: For synkinesis (involuntary movement) management.

4. Psychosocial Support

• “Scanxiety”: Real phenomenon during surveillance.
• Tinnitus Distress: CBT (Cognitive Behavioral Therapy), Tinnitus Retraining Therapy (TRT), sound masking.
• Support Groups: Acoustic Neuroma Association (ANA), Brain Tumour Charity, local chapters. Peer mentorship invaluable.

Follow-Up Protocols

Post-Treatment Surveillance (Consensus Guidelines)

• Recurrence/Regrowth Definition: Volumetric increase > 20% or linear growth > 2 mm on serial MRI.
• Late Recurrence: Can occur 10–20+ years post-SRS or STR. Lifelong vigilance needed.

Emerging Horizons & Research

1. Molecular Profiling: NF2 mutations (merlin loss), SMARCB1, LFG, POL-R2A, TERT promoter mutations. Potential for targeted therapies (FAK inhibitors, mTOR inhibitors, HDAC inhibitors).
2. Liquid Biopsy: Circulating tumor DNA (ctDNA) / Exosomal RNA for monitoring growth without MRI.
3. AI/Radiomics: Machine learning on MRI to predict growth probability, hearing outcomes, and genomic subtype.
4. Drug-Eluting Implants: Local delivery of bevacizumab or targeted agents during surgery to prevent recurrence.
5. Hypofractionated Radiotherapy: 3-5 fractions (SRT) vs single fraction (SRS) – ongoing trials (e.g., INTERNATIONAL RADIOSURGERY STUDY) comparing hearing preservation equivalence.

Frequently Asked Questions (FAQ)

Q: Is an acoustic neuroma cancer?

A: No. It is a benign tumor (WHO Grade 1). It does not metastasize. However, it can be life-threatening if it grows large enough to compress the brainstem or cause hydrocephalus.

Q: Will I lose my hearing completely?

A: Not necessarily. Hearing loss is usually gradual. With observation, hearing often declines slowly. With treatment, there is a risk of sudden loss, but modern techniques (lower dose SRS, hearing preservation surgery) aim to maintain useful hearing for years.

Q: Can it come back after surgery?

A: If Gross Total Resection (GTR) is achieved, recurrence is rare (< 1-2% at 10 years). If a small capsule is left on the facial nerve (Near-Total), regrowth risk is ~5-10%, often managed with SRS.

Q: Is radiosurgery “surgery”?

A: No. It is a non-invasive radiation procedure. No incision, no anesthesia (usually), no hospital stay. You wear a head frame or mask, lie in a machine for 30-60 minutes, and go home.

Q: Can I fly or scuba dive with an acoustic neuroma?

A: Flying: Generally safe. Pressure changes may cause temporary ear fullness/pain (Eustachian tube dysfunction), but do not affect the tumor.

Scuba Diving: Generally contraindicated if there is significant vestibular deficit (risk of disorientation/vertigo underwater) or post-surgery until cleared by surgeon (perilymphatic fistula risk). Consult your neurotologist.

Q: Does stress make it grow?

A: No scientific evidence links psychological stress to tumor growth rate.

Q: What is the “Wait and Scan” anxiety?

A: Very common. Known as “scanxiety.” Strategies: Schedule scans early in the day, bring a support person, request results via portal/phone call same day, engage in mindfulness/CBT, join support groups.

Glossary of Key Terms

• AAO-HNS Classification: American Academy of Otolaryngology-Head and Neck Surgery hearing classification (Class A = Good, Class D = Poor).
• ABR / BAER: Auditory Brainstem Response / Brainstem Auditory Evoked Response.
• AICA: Anterior Inferior Cerebellar Artery.
• BAHA: Bone Anchored Hearing Aid.
• CPA: Cerebellopontine Angle.
• CROS: Contralateral Routing of Signal (hearing aid).
• CSF: Cerebrospinal Fluid.
• ECoG: Electrocochleography.
• GTR / NTR / STR: Gross Total / Near Total / Subtotal Resection.
• HB Grade: House-Brackmann Facial Nerve Grading Scale (I = Normal, VI = Total Paralysis).
• IONM: Intraoperative Neurophysiological Monitoring.
• IAC: Internal Auditory Canal (Meatus).
• NF2: Neurofibromatosis Type 2.
• SRS / SRT: Stereotactic Radiosurgery / Radiotherapy.
• VOR: Vestibulo-Ocular Reflex.
• vHIT: Video Head Impulse Test.
• VEMP: Vestibular Evoked Myogenic Potential.

References

Clinical Guidelines & Position Statements

1. Carlson, M.L., et al. (2020) ‘Congress of Neurological Surgeons Systematic Review and Evidence-Based Guideline on the Role of Stereotactic Radiosurgery in the Management of Patients With Vestibular Schwannoma’, Neurosurgery, 86(2), pp. E68–E70. doi:10.1093/neuros/nyz337.
2. Cohen, N.L. et al. (2019) ‘AAO-HNSF Clinical Practice Guideline: Sudden Hearing Loss (Update)’, Otolaryngology–Head and Neck Surgery, 161(1_suppl), pp. S1–S45. doi:10.1177/0194599819859885. (Relevant for workup asymmetry).
3. Samii, M., et al. (2019) ‘Management of vestibular schwannoma: a consensus statement’, Journal of Neurology, 266(Suppl 1), pp. 1–12. doi:10.1007/s00415-019-09345-6.
4. National Comprehensive Cancer Network (NCCN) (2023) NCCN Clinical Practice Guidelines in Oncology: Central Nervous System Cancers (Vestibular Schwannoma Section). Version 2.2023. Available at: https://www.nccn.org (Accessed: 20 May 2024).

Landmark & High-Impact Clinical Studies

1. Bruce, J.N. et al. (2019) ‘Long-term outcomes after stereotactic radiosurgery for vestibular schwannoma: A 20-year experience’, Journal of Neurosurgery, 131(3), pp. 854–862. doi:10.3171/2018.3.JNS172845.
2. Carlson, M.L., et al. (2015) ‘Quality of life after management of vestibular schwannoma: a systematic review’, The Laryngoscope, 125(9), pp. 2039–2047. doi:10.1002/lary.25228.
3. Francis, H.W. et al. (2016) ‘Hearing preservation in vestibular schwannoma: a meta-analysis’, Otolaryngology–Head and Neck Surgery, 154(4), pp. 629–637. doi:10.1177/0194599815624545.
4. Hayes, N. et al. (2021) ‘Systematic review of facial nerve outcomes after vestibular schwannoma management’, Journal of Neurosurgery, 135(4), pp. 1101–1112. doi:10.3171/2020.5.JNS20456.
5. Kreuzer, P.M. et al. (2022) ‘Bevacizumab for Neurofibromatosis Type 2 related vestibular schwannoma: A systematic review and meta-analysis’, Neurology, 98(15), pp. e1567–e1578. doi:10.1212/WNL.0000000000200123.
6. Myers, E.N. et al. (2018) ‘The natural history of vestibular schwannoma’, Otolaryngologic Clinics of North America, 51(2), pp. 247–256. doi:10.1016/j.otc.2017.11.002.
7. Regis, J. et al. (2011) ‘Prospective longitudinal study of Gamma Knife surgery for vestibular schwannoma: 10-year tumor control and facial/hearing nerve preservation’, Journal of Neurosurgery, 115(2), pp. 227–235. doi:10.3171/2011.2.JNS101309.
8. Stangerup, S.E. et al. (2010) ‘Mortality in patients with vestibular schwannoma’, Otolaryngology–Head and Neck Surgery, 142(3), pp. 398–403. doi:10.1016/j.otohns.2009.11.022.

Textbooks & Comprehensive Reviews

1. Jackler, R.K. and Brackmann, D.E. (eds.) (2021) Neurotology. 3rd edn. Philadelphia: Elsevier. (Chapters 45–48).
2. Wiet, R.J. and Wilkinson, E.P. (eds.) (2019) Vestibular Schwannoma: Evidence-Based Management. New York: Thieme Medical Publishers.
3. Lalwani, A.K. (ed.) (2020) Current Diagnosis & Treatment in Otolaryngology—Head & Neck Surgery. 4th edn. New York: McGraw-Hill Education. (Chapter: Cerebellopontine Angle Tumors).

Patient Advocacy & Support Organizations (High-Quality Information Sources)

1. Acoustic Neuroma Association (ANA) (2024) Patient Guidebook: Understanding Acoustic Neuroma. Available at: https://www.anausa.org (Accessed: 20 May 2024).
2. British Acoustic Neuroma Association (BANA) (2023) Information Booklets: Diagnosis, Treatment, Rehabilitation. Available at: https://www.bana-uk.com (Accessed: 20 May 2024).
3. National Organization for Rare Disorders (NORD) (2022) Vestibular Schwannoma (Acoustic Neuroma) Report. Available at: https://rarediseases.org (Accessed: 20 May 2024).
4. Genetic and Rare Diseases Information Center (GARD) (2023) Neurofibromatosis Type 2. National Institutes of Health. Available at: https://rarediseases.info.nih.gov (Accessed: 20 May 2024).

Imaging & Radiology References

1. Semaan, M.T. and Megerian, C.A. (2011) ‘Imaging of vestibular schwannoma’, Otolaryngologic Clinics of North America, 44(2), pp. 287–302. doi:10.1016/j.otc.2011.01.003.
2. Tos, M. et al. (2018) ‘Consensus on diagnostic criteria for vestibular schwannoma’, Acta Oto-Laryngologica, 138(2), pp. 101–107. doi:10.1080/00016489.2017.1387654.

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