Abstract Details

Title The Caudal Vermis and the Dentate Nucleus are Critical Structures for Determining the Directional Asymmetry in Gaze-Evoked Nystagmus in Unilateral Cerebellar Lesions

Topic Neuro-ophthalmology/Neuro-otology

Presentation(s) S28 - Neuro-ophthalmology/Neuro-otology (4:03 PM-4:14 PM)

Poster/Presentation
Number 004

Background Stabilizing the eyes in space when looking at a target is provided by a brainstem/cerebellar gaze-holding network. While lesion studies in non-human primates pointed to a key role of the flocculus/paraflocculus complex in gaze holding, observations in humans indicated an involvement of the caudal vermis, the biventer lobule and the inferior semilunar lobule. Previous research suggested that acute lateralized cerebellar lesions preferentially lead to GEN on ipsilesional gaze.

Objective To further characterize gaze-evoked nystagmus (GEN) asymmetry in unilateral cerebellar stroke and hypothesized that the direction of gaze-holding impairment depends on the location of the lateralized lesions.

Design/Methods Nine patients (aged 31-62y, 2 females) with acute/subacute ( £10d old) MRI-confirmed unilateral cerebellar stroke were included. Horizontal gaze holding was quantified (range=±40° gaze) while a flashing target was slowly (0.5°/s) moving. Asymmetry in eye-drift velocity was calculated and compared to the different patterns in cerebellar lesions.

Results Individual peak eye drift velocities ranged from 3.9°/s to 17.4°/s and occurred at the most eccentric eye positions (30-40° of lateral gaze). We found significantly asymmetric GEN in 7/9 patients, which increased progressively with increasing eccentricity of eye position, indicating a non-linear behavior similar to the one observed in patients with degenerative cerebellar disease. Those patients with MRI-confirmed involvement of the caudal vermis and the dentate nucleus all presented with predominantly ipsilesional GEN (n=4), while in those with lesions restricted to the cerebellar hemisphere GEN was stronger on contralesional gaze in three out of four patients.

Conclusions Involvement of the caudal vermis (uvula, nodulus) and the dentate nucleus is critical for determining the directional asymmetry in GEN in unilateral cerebellar lesions, while the flocculus played a minor role only in human gaze-holding in our study. Specifically, the asymmetry in GEN in relation to the side of the lesion predicted which cerebellar structures have been damaged.

Authors/Disclosures
Alexander A. Tarnutzer, MD (Kantonsspital Baden AG) PRESENTER	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file

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