# Unidirectional Palsy of Torsional Saccades in Ataxia Associated with Anti-GAD Antibody

## TL;DR

A man with anti-GAD antibody-related ataxia showed a unique eye movement disorder involving torsional saccades, pointing to specific brain areas affected.

## Contribution

This case presents a novel ocular motor abnormality in anti-GAD antibody-associated ataxia.

## Key findings

- The patient exhibited unidirectional palsy of torsional saccades during head tilting.
- Brain imaging showed cerebellar vermis atrophy and involvement of the riMLF.
- Other autoantibodies and spinocerebellar ataxia genes were negative.

## Abstract

Antibodies against glutamic acid decarboxylase (GAD) are associated with various neurological syndromes including cerebellar ataxia and ocular motor abnormalities. We report a 67-year-old man with progressive dizziness and imbalance, who exhibited spontaneous downbeat and torsional nystagmus, normal vertical saccades, and a unilateral loss of torsional saccades during head tilting. Serum anti-GAD antibody was elevated. Tests for other autoantibodies and genes responsible for spinocerebellar ataxia were negative. Brain MRI showed cerebellar vermis atrophy The selective deficit of ipsiversive torsional saccades, with preserved vertical saccades, implicates involvement of the unilateral rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) that generates torsional and vertical saccades. This case highlights a novel ocular motor finding in anti-GAD antibody-associated ataxia and expands the spectrum of eye movement abnormalities related to midbrain and cerebellar dysfunction.

The online version contains supplementary material available at 10.1007/s12311-026-01984-6.