Abnormal Head Impulse Test in a Unilateral Cerebellar Lesion.
BACKGROUND
The findings of head impulse tests (HIT) are usually normal in cerebellar lesions.


METHODS
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.
Department of Neurology, Korea University Anam Hospital, Korea University College of Medicine, Seoul, Korea.
Seol Hee
SH
Baek
Department of Neurology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea. a-yeong@hanmail.net.
Jeong Yoon
JY
Choi
Department of Neurology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
Jin Man
JM
Jung
Department of Neurology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
Do Young
DY
Kwon
Department of Neurology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
Moon Ho
MH
Park
Department of Otorhinolaryngology-Head and Neck Surgery, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
June
J
Choi
Department of Neurology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
Ji Soo
JS
Kim
flocculus; head impulse test; vertigo; vestibulo-ocular reflex