Anatomy Pelvis Head Neck · Year 1 · from Anatomy Pelvis Head Neck
Case 2: Acoustic Neuroma (Vestibular Schwannoma)
Patient Demographics
- Age: 52 years old
- Sex: Male
- Occupation: Accountant
Chief Complaint
Progressive hearing loss in the left ear and persistent tinnitus for 1 year.
History of Present Illness
The patient has noticed progressive difficulty hearing from his left ear over the past year, particularly noticeable when using the telephone. He describes constant high-pitched ringing (tinnitus) in the left ear. More recently, he has experienced occasional episodes of unsteadiness and mild vertigo, though no true spinning sensation. He has noticed intermittent numbness over his left cheek. He denies headache, facial weakness, or visual changes. He has no family history of hearing loss or brain tumors.
Physical Examination
- Vitals: Within normal limits
- Neurological examination:
- Cranial nerve VII: Normal facial symmetry and movement
- Cranial nerve VIII:
- Rinne test (left): Negative (bone conduction > air conduction, abnormal)
- Weber test: Lateralizes to the right (normal ear)
- Finger rub: Decreased on left
- Cranial nerve V: Decreased sensation to light touch over left cheek (V2 distribution)
- Gait: Slightly wide-based; mild unsteadiness with tandem walking
- Eyes: Normal extraocular movements; no nystagmus at rest; gaze-evoked nystagmus to left
Imaging Workup
- Audiogram: Left-sided sensorineural hearing loss, worse at high frequencies; speech discrimination disproportionately poor
- MRI brain with gadolinium: 2.5 cm enhancing mass in the left cerebellopontine angle, extending into and expanding the internal acoustic meatus, consistent with vestibular schwannoma
Diagnosis
Vestibular schwannoma (acoustic neuroma) in the left cerebellopontine angle.
Anatomical Correlation
The vestibulocochlear nerve (CN VIII) passes through the internal acoustic meatus along with the facial nerve (CN VII), the nervus intermedius, and the labyrinthine artery. Vestibular schwannomas arise from Schwann cells of the vestibular portion of CN VIII, typically within the internal acoustic meatus, and grow into the cerebellopontine angle (CPA). The CPA is bounded by the pons medially, cerebellum posteriorly, and petrous temporal bone anterolaterally. As the tumor grows, it compresses adjacent structures in predictable sequence: first CN VIII (hearing loss, tinnitus, vestibular dysfunction), then CN VII (facial weakness is a late finding due to the nerve's resilience), then CN V (facial numbness from trigeminal compression), and eventually the cerebellum (ataxia) and brainstem. The sensorineural hearing loss is confirmed by the Rinne test showing bone conduction better than air conduction (negative Rinne) on the affected side, with Weber lateralizing to the normal ear. The poor speech discrimination despite modest pure-tone loss is characteristic of retrocochlear lesions.
Treatment
- Observation: For small tumors in older patients; serial MRI monitoring
- Stereotactic radiosurgery (Gamma Knife): For tumors <3 cm; tumor control >90%
- Microsurgical resection: For larger tumors or those with significant mass effect
- Hearing preservation: May be possible with small tumors and good preoperative hearing
- Facial nerve monitoring: Intraoperative monitoring to preserve function during surgery