Acoustic neuroma

• Vestibular schwannoma
• Acoustic schwannoma
• Cerebellopontine angle tumor

• 225.1 Benign neoplasm of cranial nerves

• D33.3 Benign neoplasm of cranial nerves

• Pattern 5A: Primary Prevention/Risk Reduction for Loss of Balance and Falling
• Pattern 5F: Impaired Peripheral Nerve Integrity and Muscle Performance Associated with Peripheral Nerve Injury

Description

• Disorder of the vestibulocochlear nerve (8th cranial nerve) that carries vestibular and auditory input from the inner ear to the central nervous system
• Slow-growing (usually 1 to 2 mm/year), benign tumor of the myelin-forming Schwann cells that surround the vestibular portion of the 8th cranial nerve
• Tumor most commonly originates from the inferior vestibular branch
• Tumor forms in the internal auditory canal and can extend into the cerebellopontine angle
• Typically results in a gradual onset of high-frequency sensorineural hearing loss, tinnitus, sense of ear fullness, unsteadiness, dizziness, or vertigo
• As tumor grows, there may be facial nerve involvement (resulting in facial numbness or weakness), headache, hydrocephalus, incoordination, diplopia, hoarseness, difficulty swallowing, brainstem compression, or death

Essentials of Diagnosis

• Physical exam normal unless the cerebellum or brainstem is compromised
• Audiogram abnormal
• Imaging studies abnormal
• Neurotologic exam abnormal
• Thorough and detailed history is essential to distinguish acoustic neuroma from other vestibular disorders and central pathology

General Considerations

• Patients typically present with complaints of progressive hearing loss and loss of balance worsening gradually over several months
• Other typical symptoms include tinnitus (ringing or noises in the ear) and sense of ear fullness
• Patients occasionally present with complaints of vertigo or vague report of dizziness
• May complain of blurred vision due to oscillopsia (perceived movement of the environment)
• If tumor growth progresses, may present with other cranial nerve (especially V and VII), brainstem, or cerebellar signs and symptoms

Demographics

• Uncommon in general population, but most common cerebellopontine angle tumor (80% of these tumors)
• Unknown etiology
• Typically occurs in 5th or 6th decade of life
• Mortality has been nearly eliminated; morbidity rates have been significantly reduced due to improved techniques for early diagnosis and improved treatment approaches

Signs and Symptoms

• Unexplained unilateral sensorineural hearing loss with high-frequency loss on audiogram
• Imbalance, as manifested by difficulty standing and walking
• Increased risk of falling
• Vague sense of dizziness; may be constant or increasingly severe with head movement
• Abnormal auditory brainstem response
• Hypoactive or absent caloric response
• Abnormal MRI
• May observe nystagmus in room light or with fixation removed
• Abnormal neurotologic exam (impulse test, headshake test, dynamic visual acuity test, caloric test, VEMP test, or SVV test)
• May present with central symptoms, such as diplopia, dysarthria, dysphagia, dysmetria, numbness, or weakness if tumor has compressed brainstem or cerebellum

Functional Implications

• Impedes balance and contribute to falls
• Provokes dizziness with rapid head movements, such as ...