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  • Vestibular schwannoma
  • Acoustic schwannoma
  • Cerebellopontine angle tumor

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  • 225.1 Benign neoplasm of cranial nerves

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  • D33.3 Benign neoplasm of cranial nerves

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Description

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  • 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

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Essentials of Diagnosis

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  • 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

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General Considerations

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  • 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

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Demographics

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  • 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

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Signs and Symptoms

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  • 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

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Functional Implications

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

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