Vestibular Schwannoma (Acoustic Neuroma)

Key Features

• Eighth nerve schwannomas are among the most common of intracranial tumors

• The lesions arise within the internal auditory canal and gradually grow to involve the cerebellopontine angle, eventually compressing the pons and resulting in hydrocephalus

• Most are unilateral

• About 5% are associated with hereditary syndrome, neurofibromatosis type 2

• Any individual with a unilateral or asymmetric sensorineural hearing loss should be evaluated for an intracranial mass lesion

• Other lesions of the cerebellopontine angle, such as meningioma and epidermoids, may have similar audiovestibular manifestations

Clinical Findings

• Typical auditory symptoms are unilateral hearing loss with deterioration of speech discrimination exceeding that predicted by the degree of pure-tone loss

• Nonclassic presentations, such as sudden unilateral hearing loss, are fairly common

• Vestibular dysfunction more often takes the form of continuous dysequilibrium than episodic vertigo

Diagnosis

• Diagnosis is made by enhanced MRI

Treatment

• Depends on such factors as patient age, underlying health, and size of the tumor

• Consists of

  • Observation

  • Microsurgical excision

  • Stereotactic radiotherapy

• Bevacizumab (vascular endothelial growth factor blocker) has shown promise in treating neurofibromatosis type 2