Neurology · Year 3 · from Neurology

Case 2: Vestibular Schwannoma (Acoustic Neuroma)

Patient Demographics

  • Age: 52 years
  • Sex: Male
  • Occupation: High school band teacher

Chief Complaint

"I've been having trouble hearing in my right ear for the past year, and now my ear is ringing."

History of Present Illness

The patient, a music teacher, first noticed difficulty hearing in his right ear about 18 months ago - he had trouble hearing students on his right side and began favoring his left ear on phone calls. The hearing loss has been gradually progressive. About 6 months ago, he developed constant high-pitched ringing (tinnitus) in his right ear. Over the past 3 months, he has noticed occasional mild imbalance, particularly when turning quickly, though no true spinning vertigo. He denies any facial weakness, numbness, or taste changes. He denies headache, nausea, or vomiting. He has no history of noise exposure beyond normal teaching environment, no ear infections, and no family history of hearing loss or tumors.

Neurological Examination Findings

Mental Status:

  • Alert, oriented, normal mood

Cranial Nerves:

CN VIII (Vestibulocochlear):

  • Right ear: Decreased hearing to finger rub
  • Left ear: Intact hearing
  • Weber test: Lateralizes to LEFT (away from affected ear - sensorineural loss)
  • Rinne test:
  • Right: Air conduction > bone conduction (positive Rinne, but both reduced)
  • Left: Air conduction > bone conduction (normal)
  • Confirms: Right sensorineural hearing loss (AC>BC but both decreased)

CN VII (Facial):

  • Facial strength symmetric at rest and with movement
  • No synkinesis
  • Eye closure complete bilaterally
  • House-Brackmann Grade I (normal)

CN V (Trigeminal):

  • Facial sensation intact to light touch and pinprick
  • Corneal reflex present bilaterally
  • Masseter strength normal

Other Cranial Nerves:

  • II: Visual acuity 20/25 OU, visual fields full, no papilledema
  • III, IV, VI: Extraocular movements full, no nystagmus
  • IX, X: Palate symmetric, gag intact
  • XI, XII: Normal

Cerebellar/Vestibular:

  • Finger-to-nose: Normal
  • Heel-to-shin: Normal
  • Gait: Normal, tandem gait intact
  • Romberg: Negative (no significant imbalance)
  • Head impulse test: Normal

Motor, Sensory, Reflexes:

  • All within normal limits

Neuro Workup

Audiometry:

  • Right ear: Asymmetric sensorineural hearing loss
  • Moderate-to-severe high-frequency loss (4000-8000 Hz)
  • Word recognition score: 60% (reduced)
  • Left ear: Normal hearing thresholds

MRI Brain with Contrast (IAC Protocol):

  • 2.2 cm enhancing mass in right cerebellopontine angle
  • Extends into and expands the right internal auditory canal ("ice cream cone" appearance)
  • Displaces but does not invade brainstem
  • No hydrocephalus
  • No other lesions
  • Characteristic appearance of vestibular schwannoma

Brainstem Auditory Evoked Responses (BAER):

  • Prolonged latency waves I-III on right (retrocochlear pathology)
  • Normal on left

Diagnosis

Right Vestibular Schwannoma (Acoustic Neuroma)

  • Koos Grade II (extends into CPA, <2.5 cm)
  • Sporadic (unilateral)

Differential Diagnosis Considered

  1. Vestibular schwannoma - most likely given imaging
  2. Meningioma - typically dural-based, different enhancement pattern
  3. Epidermoid cyst - non-enhancing, different signal characteristics
  4. Facial nerve schwannoma - rare

Rule Out NF2

  • Unilateral tumor - most likely sporadic
  • No cafe-au-lait spots
  • No other tumors on imaging
  • No family history
  • If bilateral schwannomas were present, would diagnose Neurofibromatosis Type 2

Management Options Discussed

1. Observation with Serial Imaging:

  • Appropriate for small tumors (<1.5 cm)
  • Patient preference for less invasive approach
  • MRI every 6-12 months
  • Risk: Tumor may grow, hearing may decline

2. Stereotactic Radiosurgery (Gamma Knife):

  • Single high-dose focused radiation
  • 90-95% tumor control rate
  • Preserves serviceable hearing in 50-70%
  • Facial nerve preservation >95%
  • Lower immediate risk than surgery
  • Long-term radiation risks (rare)

3. Microsurgical Resection:

  • Definitive tumor removal
  • Approaches: Retrosigmoid, middle fossa, translabyrinthine
  • Hearing preservation possible with smaller tumors
  • Facial nerve at risk (97% preservation at experienced centers)
  • Recommended for: Large tumors, young patients, growing tumors

Treatment Decision

  • After multidisciplinary discussion (neurosurgery, radiation oncology, audiology)
  • Patient elected stereotactic radiosurgery given:
  • Medium-sized tumor
  • Desire to minimize surgical risks
  • Some serviceable hearing remains
  • No facial weakness currently

Follow-up Plan

  1. Pre-treatment audiogram documented
  2. Gamma Knife radiosurgery performed
  3. MRI in 6 months, then annually
  4. Audiometry annually
  5. Monitor for: Facial weakness, hearing changes, trigeminal symptoms
  6. Hearing aid evaluation for right ear

Prognosis

  • Tumor control with radiosurgery: >90% at 10 years
  • Hearing preservation: 50-60% maintain serviceable hearing
  • Facial nerve function: >95% maintain normal function
  • May require surgery if tumor grows despite radiation

Clinical Image

Image Description: Axial T1-weighted MRI with contrast showing an enhancing mass in the right cerebellopontine angle extending into the internal auditory canal, characteristic of vestibular schwannoma (acoustic neuroma).

Attribution: Image from Wikimedia Commons. Licensed under CC BY-SA 3.0. Source: https://commons.wikimedia.org/wiki/File:Acoustic_neuroma.jpg

Key Teaching Points

Bell's Palsy

  1. Peripheral = entire hemiface (including forehead); Central = forehead spared
  2. Most common cause of acute facial paralysis
  3. Start prednisone within 72 hours - improves outcomes
  4. Eye protection is critical - prevent corneal injury
  5. 85% recover fully; poor prognostic factors include complete paralysis, age >60, diabetes
  6. Always examine ear for vesicles (Ramsay Hunt) and consider Lyme disease

Vestibular Schwannoma

  1. Classic triad: Unilateral hearing loss, tinnitus, imbalance
  2. Hearing loss is sensorineural - Weber lateralizes to normal ear
  3. MRI with contrast (IAC protocol) is diagnostic imaging
  4. Bilateral schwannomas = Neurofibromatosis Type 2
  5. Treatment options: Observation, radiosurgery, microsurgery
  6. Facial nerve preservation is a key surgical consideration

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