Module 6 GQ's

• Categories of peripheral vestibular disorders

  • Unilateral vestibular hypofunction
  • Bilateral vestibular hypofunction
  • Recurrent pathological excitation or inhibition of the peripheral vestibular system
• Unilateral vestibular hypofunction


  Symptom: acute onset rotary vertigo and includes vestibular neuritis, labyrinthitis & acoustic neuroma
• Bilateral vestibular hypofunction


  Symptom: postural imbalance
• Recurrent pathological excitation or inhibition of the peripheral vestibular system


  Symptom: recurrent attacks of vertigo
• Causes of unilateral vestibular hypofunction

  • Viral or bacterial infections (ex. Vestibular neuritis, labyrinthitis)
  • Head trauma
  • Vascular occlusion
  • Unilateral vestibulopathy
  • Following surgical procedures (ex. Labyrinthectomy & acoustic neuroma resection)
• Symptoms of unilateral vestibular hypofunction

  • Acute onset of severe rotational vertigo
  • Spontaneous horizontal-rotatory nystagmus
  • Beating toward the unaffected side
  • Slight oscillopsia
  • Postural instability when turning head quickly to affected side
  • Nausea and vomiting
• Underlying mechanism for symptoms of unilateral vestibular hypofunction

  • Imbalance of the tonic firing rates of the left and right sides of the vestibular system
  • Damage to the vestibular system that decreases unilateral function creates an imbalance between both sides and results in the brain's misperception that head movement has occurred. Triggers VOR as a corrective response
• Typical pattern of recovery in patients with unilateral vestibular hypofunction

  1. Resolution of vertigo, spontaneous nystagmus, dynamic VOR, and postural instability within 3-7 days

  2. Patient able to suppress nystagmus with visual fixation

  3. Spontaneous nystagmus may always be present in the dark

  4. Resolution of dynamic VOR and postural instability is usually slower to recover and may take up to one year
• Vestibular neuritis


  • Infection of the vestibular nerve results in nerve degeneration that is usually unilateral but can be bilateral
  • Onset is preceded by a viral infection of the upper respiratory or gastrointestinal tracts
• Populations more prone to vestibular neuritis


  • Persons between 30-60 years
  • Peak incidence for women in 4th decade and men in 6th decade
• Symptoms and signs of vestibular neuritis

  • Sudden prolonged severe vertigo that is worsened by head movements
  • Spontaneous horizontal-rotatory nystagmus
  • Beating toward good ear
  • Postural imbalance to affected side
  • Nausea
  • Hearing remain intact
• Labyrinthitis


  Inflammatory disorder of the membranous labyrinth
• Causes of labyrinthitis


  Viral or bacterial infections
• Populations more prone to labyrinthitis

  • Affects all individuals
  • Viral labyrinthitis occurs in adults in their 4th-7th decades of life
• Symptoms and signs of labyrinthitis

  • Vertigo
  • Nystagmus
  • Postural imbalance
  • Nausea
  • Tinnitus and/or hearing loss
• Acoustic neuroma or vestibular schwannoma


  Intracranial tumors that produce vestibular symptoms
• Causes of acoustic neuromas


  Slow-growing benign tumors that originate from Schwann cells, lining the vestibular portion of the 8th cranial nerve within the internal auditory canal
• Symptoms and signs of acoustic neuromas early in the disease

  • Vertigo
  • Disequilibrium
  • Tinnitus
  • Asymmetric hearing loss due to compression of the vestibulocochlear nerve
• Symptoms and signs if the acoustic neuroma arises in the internal auditory canal and how they may change with growth of the tumor

  • Arises in internal auditory canal: tinnitus and hearing loss
  • Continued growth: compress facial nerve or trigeminal nerve at its root or ganglion causing facial weakness and numbness
• Vestibular impairment with resection of acoustic neuroma

  Loss of unilateral vestibular afferences causing the brain to perceive asymmetrical vestibular input
• Most common causes of bilateral vestibular hypofunction

  • Ototoxicity
  • Inner-ear autoimmune disorders
  • Bilateral Meniere's disease
  • Bilateral tumors
  • Bilateral vestibulopathy due to aging
  • Infections (ex. Meningitis or bilateral sequential vestibular neuritis
• Primary symptoms and signs of bilateral vestibular hypofunction

  • Disequilibrium
  • Severe postural instability with resultant gait ataxia
  • Oscillopsia with head movement due to bilaterally impaired or absent vestibulospinal and vestibulo-ocular reflexes
• Bilateral vestibular hypofunction symptoms/signs are permanent but people can return to high function levels
• Populations more prone to benign paroxysmal positional vertigo

  • Women in their 4th & 5th decades of life
• Underlying mechanism for BPPV

  • Otoconia detaching from the otolithic membrane in the utricle and migrating into one of the semicircular canals
  • Due to rapid head position changes the free-floating otoconia create convection waves on endolymph that deflect the cupula of the affected semicircular canal
• BPPV categorization


  By the particular semicircular canals involved and whether the detached otoconia are free-floating within the affected canal (canalithiasis) or attached to the cupula (cupulolithiasis)
• Differences between posterior and horizontal canal BPPV

  • Posterior canal: more common because of its relationship to the otoliths when the person is in the recumbent position
  • Horizontal canal: less common but can have more intense symptoms; dizziness is more persistent and easily triggered with typical head movements of daily living
• Differences between canalithiasis and cupulolithiasis

  • Canalithiasis: free-floating within affected canal
  • Cupulolithiasis: attached to the cupula causes direct pull on hair cells and is not dependent on the drag of the endolymph, more commonly in horizontal semicircular canals
• Most common causes of BPPV in persons less than 50 years old and greater than or equal to 50 years old


  • Less than 50 years old: Head injury due to concussive force that displaces otoconia
  • Greater or equal to 50 years old: Associated with age-related degeneration of the otolithic membrane
• Meniere's disease


  • Disorder of the inner ear that is also known as idiopathic endolymphatic hydrops
  • Pathophysiology: increased endolymphatic pressure within the inner ear possibly caused by malabsorption of the endolymph in the endolymphatic duct and sac leading to inappropriate nerve excitation
• Populations more prone to Meniere's disease

  • Women in their 4th and 5th decades of life
• Symptoms and signs of a typical Meniere's disease attack

  • Pressure
  • Discomfort
  • Fullness sensation in the ears
  • Reduction in hearing
  • Tinnitus
  • Rotational vertigo
  • Postural imbalance
  • Nystagmus
  • Nausea and vomiting
• Hearing may recover after a Meniere's disease attack but there may be residual permanent sensorineural hearing loss (low frequencies)
• In advanced Meniere's disease, hearing doesn't return after the attack and symptoms of vertigo lessen in frequency and severity
• Perilymphatic fistula


  • Caused by a tear or defect in the oval and/or round windows that separate the air-filled middle ear and the fluid perilymphatic space of the inner ear
  • Small opening allows for perilymph to leak into the middle ear
• Causes of perilymphatic fistula


  • Head trauma which if often minor
  • Excessive intracranial or atmospheric pressure changes
• Symptoms and signs of perilymphatic fistula

  • 'pop' in the fear followed by onset of sudden vertigo, hearing loss, and loud tinnitus
  • Postural imbalance
  • Nystagmus
  • Nausea
  • Vomiting
  • Pressure sensitivity (sometimes experienced)
• Superior semicircular canal dehiscence

  Occurs when a portion of the temporal bone that normally covers the superior semicircular canal is thin or missing exposing the membranous semicircular canal to stimuli that it normally does not receive (ex. Sound changes, changes in ICP, or vibrations)
• Tullio's phenomenon


  Vestibular symptoms are induced by auditory stimuli
• Causes of central vestibular disorders

  • Verterbrobasilar ischemia disease (ex. Vertebrobasilar insufficiency & stroke)
  • Traumatic head injury
  • Migrane-associated dizziness
  • Conditions that affect the brainstem and cerebellum (ex. Cerebellar degeneration, multiple sclerosis, tumors)