Acoustic Neuroma (Vestibular Schwannoma)
Definition
Schwannoma of the vestibular portion of CN VIII
NOTE: Most common intracranial tumour causing SNHL
NOTE: Most common cerebellopontine angle tumour
Pathogenesis
Clinical Features
NOTE: In elderly, unilateral tinnitus or SNHL is acoustic neuroma until proven otherwise
Diagnosis
Treatment
Source
Toronto Notes 2012
Schwannoma of the vestibular portion of CN VIII
NOTE: Most common intracranial tumour causing SNHL
NOTE: Most common cerebellopontine angle tumour
Pathogenesis
- Starts in the internal auditory canal and expands into cerebellopontine angle (CPA), compressing cerebellum and brainstem
- When associated with type 2 neurofibromatosis (NF2): bilateral acoustic neuromas, cafe-au-lait skin lesions and multiple intracranial lesions
Clinical Features
- Usually presents with unilateral SNHL or tinnitus
- Dizziness and unsteadiness may be present, but true vertigo is rare as tumour growth occurs slowly and thus compensation occurs
- Facial nerve palsy and trigeminal (V1) sensory deficit (corneal reflex) are late complications
NOTE: In elderly, unilateral tinnitus or SNHL is acoustic neuroma until proven otherwise
Diagnosis
- MRI with gadolinium contrast is the gold standard
- Audiogram (to assess SNHL)
- Poor speech discrimination relative to the hearing loss
- Stapedial reflex absent or significant reflex decay
- ABR - increase in latency of the 5th wave
- Vestibular tests: normal or asymmetric caloric weakness (an early sign)
Treatment
- Expectant management if tumour is very small, or in elderly
- Definitive management is surgical excision
- Other options: gamma knife, radiation
Source
Toronto Notes 2012