II. Indications

  1. Acute Vestibular Syndrome (AVS) evaluation
  2. Distinguishes Acute Peripheral Vestibulopathy (APV) from posterior CVA
    1. Catch-up saccades are present in APV but absent in cerebellar stroke

III. Mechanism

  1. Vestibulo-ocular reflex function test
  2. Peripheral Vertigo disrupts the Medial Longitudinal Fasciculus
    1. Medial Longitudinal Fasciculus is the communication between the vestibular system and Oculomotor Nucleus
    2. Catch-up saccade is present due to a delay in the eyes needing to correct for the head position change
    3. In a posterior CVA, the defect is at a higher level and the eye correction is immediate (no saccade is seen)

IV. Technique

  1. Examiner asks the patient to focus on the examiners nose throughout the procedure
    1. Examiner rapidly rotates a patients head 20-40 degrees to the right or left
    2. Patients eyes are observed for Nystagmus
    3. Observe for one eye that lags in response to maintain forward gaze
      1. Makes quick saccade movement to catch-up or correct
    4. Procedure is repeated several times on each side
  2. Avoiding habituation
    1. In between rapid movements, examiner gently and slowly rotates the patient's head from side to side
    2. Procedure is repeated multiple times, randomly selecting one side or the other
      1. Prevents the patient from anticipating which side will be tested next

V. Interpretation

  1. Vertigo with a "normal" test (no saccade correction)
    1. Strongly suggests central Vertigo (e.g. cerebellar infarction)
  2. Vertigo with an "abnormal" test (saccade corrections are present)
    1. Weakly suggests Acute Peripheral Vestibulopathy (APV)

VI. Efficacy

  1. High Test Specificity for central Vertigo (low False Positive Rate)
    1. Strongly suggests central Vertigo (e.g. posterior CVA)
    2. Test is most valuable when "normal" (no saccade/correction) suggesting an Acute Vestibular Syndrome (AVS)
  2. Test Sensitivity for central Vertigo: 85%
    1. Saccade present despite central Vertigo in 15% of cases (False Negative Rate)
    2. Presence of a saccade does not exclude central Vertigo

VII. Resources

  1. Video of a Head Impulse Test with saccades present
    1. https://www.youtube.com/watch?v=4EBwtckFfTo

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