Vestibular schwannoma/ acoustic neuroma

Overview:

• Benign lesion arising from Schwann cells
• Majority of lesions arise from the vestibular branch of CN VIII

Epidemiology:

• Represents 8% of all brain tumors
• Neurofibromatosis type 2 comprises 5% (bilateral vestibular schwannomas highly suggestive of neurofibromatosis type 2)
• 95% are sporadic

Symptoms:

1. General Symptoms:
   • Occipital pain on the side of the tumor
   • VIII nerve damage
2. Hearing and Balance:
   • Unilateral sensorineural deafness (gradual onset in ~90% of patients)
   • Sudden hearing loss (~5% of patients)
   • Vertigo (mild and non-pulsatile)
   • Tinnitus (~70%)
   • Caloric paresis
3. V Nerve Damage:
   • Early depression of corneal reflex
   • Facial pain, paraesthesia, numbness
4. VII Nerve Damage:
   • Facial weakness (unusual)
5. IX, X, XI Nerve Damage:
   • Rare; dysphagia, change in voice, palatal weakness
6. Mass Effect Symptoms:
   • On cerebellum: Ataxia, loss of coordination on ipsilateral side, nystagmus
   • On pons: Contralateral hemiparesis
   • On aqueduct and 4th ventricle: Raised intracranial pressure (e.g., headache)

Imaging:

1. CT Scan:
   • Limited ability to distinguish between soft tissues
   • Small tumors located in the internal auditory canal (a bony structure)
   • Does not provide necessary contrast for clear depiction within soft tissue
2. MRI:
   • Very sensitive, can demonstrate lesions of 1-2 mm diameter within the auditory canal
   • Preferred imaging modality

Referral:

• Urgent ENT referral essential for patients with sudden sensorineural hearing loss
• Less urgent for patients with conductive hearing loss

Additional Notes:

• Reason for imaging patients with sudden onset hearing loss (SOHL) is largely to exclude vestibular schwannoma