title: Covert anti-compensatory quick eye movements during head impulses.
abstract: BACKGROUND
  Catch-up saccades during passive head movements, which compensate for a deficient vestibulo-ocular reflex (VOR), are a well-known phenomenon. These quick eye movements are directed toward the target in the opposite direction of the head movement. Recently, quick eye movements in the direction of the head movement (covert anti-compensatory quick eye movements, CAQEM) were observed in older individuals. Here, we characterize these quick eye movements, their pathophysiology, and clinical relevance during head impulse testing (HIT).
  
  
  METHODS
  Video head impulse test data from 266 patients of a tertiary vertigo center were retrospectively analyzed. Forty-three of these patients had been diagnosed with vestibular migraine, and 35 with Menière's disease.
  
  
  RESULTS
  CAQEM occurred in 38% of the patients. The mean CAQEM occurrence rate (per HIT trial) was 11±10% (mean±SD). Latency was 83±30 ms. CAQEM followed the saccade main sequence characteristics and were compensated by catch-up saccades in the opposite direction. Compensatory saccades did not lead to more false pathological clinical head impulse test assessments (specificity with CAQEM: 87%, and without: 85%). CAQEM on one side were associated with a lower VOR gain on the contralateral side (p<0.004) and helped distinguish Menière's disease from vestibular migraine (p = 0.01).
  
  
  CONCLUSIONS
  CAQEM are a common phenomenon, most likely caused by a saccadic/quick phase mechanism due to gain asymmetries. They could help differentiate two of the most common causes of recurrent vertigo: vestibular migraine and Menière's disease.
authors.affiliation: German Center for Vertigo and Balance Disorders, Munich University Hospital, Munich, Germany; Department of Neurology, Munich University Hospital, Munich, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Heuberger
authors.affiliation: German Center for Vertigo and Balance Disorders, Munich University Hospital, Munich, Germany.
authors.forename: Murat
authors.initials: M
authors.lastname: Sağlam
authors.affiliation: German Center for Vertigo and Balance Disorders, Munich University Hospital, Munich, Germany.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Todd
authors.affiliation: German Center for Vertigo and Balance Disorders, Munich University Hospital, Munich, Germany; Department of Neurology, Munich University Hospital, Munich, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Jahn
authors.affiliation: German Center for Vertigo and Balance Disorders, Munich University Hospital, Munich, Germany; Institute for Clinical Neurosciences; Munich University Hospital, Munich, Germany; Brandenburg Institute of Technology, Cottbus - Senftenberg, Germany.
authors.forename: Erich
authors.initials: E
authors.lastname: Schneider
authors.affiliation: German Center for Vertigo and Balance Disorders, Munich University Hospital, Munich, Germany; Department of Neurology, Munich University Hospital, Munich, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Lehnen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005133:Eye Movements / Q000502:physiology*; D064087:Head Impulse Test; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008575:Meniere Disease / Q000503:physiopathology; D008875:Middle Aged; D008881:Migraine Disorders / Q000503:physiopathology; D012438:Saccades; D055815:Young Adult
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