Positive VHIT in pt with Cerebellar Ataxia

We interpret positive HIT to be due to peripheral vestibular deficit. But it can be seen in patients with cerebellar ataxia also.
False-Positive Head-Impulse Test in Cerebellar Ataxia
Abnormal Head Impulse Test in a Unilateral Cerebellar Lesion

It’s explained by deficit in floccular function.
Isolated floccular infarction: impaired vestibular responses to horizontal head impulse

Here’s a femail patient 59yr; her instability had started 2yr ago very progressively so she can’t walk, even sit unsupported; appendicular ataxia and dysarthria are also obvious signs of cerebellar dysfunction. MRI document marked cerebellar atrophy.

  • gaze evoked Ny
  • smooth pursuit: saccadic
  • very reduced OKN
  • bilaterally positive HIT
  • positive VVOR test


Very reduced VOR gain
Cerebellar_Atrophy_VHIT Cerebellar_Atrophy_VHIT_L
BUT caloric test is normal
Cerebellar_Atrophy_Caloric_Test
Obviously, peripheral vestibular function is preserved. SPV is not elevated, meaning that nodular control of vestibular nuclei is preserved. Markedly reduced VOR gain could be explained by floccular dysfunction.

That means that in a regard of peripheral vestibular assessment in patients with cerebellar ataxia isn’t enough to perform just vhit, but also a caloric test.

Positive VVOR test was explained by three non-functioning compensatory mechanisams: smooth pursuit, OKR, VOR (first two as a sign of central vestibular dysfunction and third as peripheral vestibular dysfunction) and was considered as pathognomonic sign of CANVAS.

3 thoughts on “Positive VHIT in pt with Cerebellar Ataxia

  1. Ninoslava Mihajlović

    Pacijentkinja koja je pre više godina imala infarkt cerebeluma imala je veoma izraženu cerebelarnu ataksiju . Hod je bio naročito poremećen kad prelazi ulicu jer tada nije bilo barijera koje služe kao orijentir. Štap nije htela da nosi i teturala se tako da je okolina mislila da je pijana. Imala je povremeno i BPPV koji se na Head thrust manevar gubio. Dobijala je više meseci i Betaserc a 24 mg-1×1 tbl. Pre oko godinu dana je dobro osposobljen fizioterapeut počeo vežbe za poboljšanje ravnoteže koje izvodi sa pacijentkinjom 2x nedeljno. Rezultati su vidljivi, stabilno hoda na nešto široj osnovi ali nema više zanošenja u stranu i padanja. Horizontalni Ny pri pogledu u desno se konstantno održava. Romberg sa zatvorenim očima je i dalje pozitivan- leluja se levo desno ali nema tendenciju padanja- koncentriše se i održava voljno ravnotežu.. Tandem hod je nemoguć i dalje . Zaključak: vežbe za ravnotežu mogu uticati da se cerebelarna ataksija ublaži jer dolazi do uključivanja viših kortikalnih funkcija koje kompenzuju deficit.Kada se radi o bilo kom poremećaju ravnoteže vrlo je korisna saradnja neurologa ,radiologa ( treba mu naglasiti koji deo glave treba da fokusira prilikom snimanja) , ORL. specijaliste ,fizijatra i fizioterapeuta. Najbolje je da se napravi zajednički dogovor što je kod nas moguće uglavnom preko medicinske dokumentacije . Mr sci Nina Mihajlović-spec. neurologije, http://www.neuropsihomedika.com

    Reply
  2. Georgios Panagiotopoulos

    Dusan,
    how can we explain mean gain > 1 in the anterior canals?
    Best regards
    George

    Reply
    1. DrDusan Post author

      Dear Georgios,
      thanks for the comment.
      I’m not very confident with the results in vertical canals. So I take it with caution. Sometimes on the equipment that I use (synapsys) I can get 1,1 in horizontal canals also.

      Reply

Leave a Reply to Ninoslava Mihajlović Cancel reply

Your email address will not be published. Required fields are marked *