Exam

Oculovestibular Testing

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Oculovestibular Testing, Cold Calorics, Caloric Response, Vestibulo Ocular Reflex, Oculovestibular Reflex

  • Indications
  1. Comatose patient with suspected Brainstem injury
  • Technique
  1. Examine External Ear canals first to confirm no significant ear Trauma, or Tympanic Membrane Perforation
  2. Patient supine with head at 30 degrees elevation
    1. Isolates input of horizontal semicircular canals
  3. Instill 10-20 ml iced saline or water into auditory canal
    1. Use 20 cc syringe
    2. Use butterfly tubing with needle cut off
    3. Cools mastoid bone and alters endolymphatic flow
    4. Stimulates vestibular nuclei as if head turned rapidly to opposite side
  • Interpretation
  • Findings
  1. Nystagmus both eyes slow toward cold, fast to midline (away from cold)
    1. Not comatose
  2. Both eyes tonically deviate toward cold water
    1. Coma with injured cortex, but intact Brainstem
  3. No eye movement
    1. Brainstem injury
  4. Movement only of eye on side of stimulus
    1. Internuclear Ophthalmoplegia
    2. Suggests Brainstem structural lesion
  • Interpretation
  • By Condition
  1. Normal patient
    1. Nystagmus both eyes slow toward cold, fast to midline (away from cold)
  2. Deep coma (Tonic pupil response)
    1. Eyes will deviate toward the cold water infusion
    2. Rapid correction is slow or absent
  3. Brainstem lesion
    1. Eyes will not deviate on Cold Calorics (no slow or fast component)
  4. Lesion at CN 3 or 6 (or the Medial Longitudinal Fasciculus)
    1. Results in abnormal Cold Calorics depending on the lesion location