J Clin Neurol.  2015 Jul;11(3):279-282. 10.3988/jcn.2015.11.3.279.

Abnormal Head Impulse Test in a Unilateral Cerebellar Lesion

• Baek SH
• Choi JY
• Jung JM
• Kwon DY
• Park MH
• Choi J
• Kim JS

• KMID: 1894570
• DOI: http://doi.org/10.3988/jcn.2015.11.3.279

Abstract

BACKGROUND
The findings of head impulse tests (HIT) are usually normal in cerebellar lesions.
CASE REPORT
A 46-year-old male presented with progressive dizziness and imbalance of 3 weeks duration. The patient exhibited catch-up saccades during bedside horizontal HIT to either side, which was more evident during the rightward HIT. However, results of bithermal caloric tests and rotatory chair test were normal. MRI revealed a lesion in the inferior cerebellum near the flocculus.
CONCLUSIONS
This case provides additional evidence that damage to the flocculus or its connections may impair the vestibulo-ocular reflex only during high-speed stimuli, especially when the stimuli are applied to the contralesional side. By observing accompanying cerebellar signs, the abnormal HIT findings caused by a cerebellar disorder can be distinguished from those produced by peripheral vestibular disorders.

Keyword

vertigo; flocculus; head impulse test; vestibulo-ocular reflex

MeSH Terms

Caloric Tests
Cerebellar Diseases
Cerebellum
Dizziness
Head Impulse Test*
Humans
Magnetic Resonance Imaging
Male
Middle Aged
Reflex, Vestibulo-Ocular
Saccades
Vertigo

Figure

• 

  Fig. 1 T2-weighted (A and C) and gadolinium-enhanced T1-weighted (B and D) MRIs show a round cystic lesion located in the left inferior cerebellum. The lesion is bordered by the flocculus anterolaterally, paraflocculus (tonsil) medially, and inferior and middle cerebellar peduncles anteromedially.

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