Anti-GAD antibodies and periodic alternating nystagmus.

BACKGROUND

Autoantibodies directed against glutamic acid decarboxylase (GAD-Ab) have recently been described in a few patients with progressive cerebellar ataxia, suggesting an autoimmune physiopathologic mechanism.

OBJECTIVE

To determine the exact role of GAD-Ab and gamma-aminobutyric acid (GABA)-ergic neurotransmission in the pathogenesis of cerebellar ataxia.

DESIGN

Case report.

SETTING

University neurological hospital.

PATIENT

We report the case of a patient with subacute cerebellar ataxia associated with GAD-Ab showing periodic alternating nystagmus (PAN).

INTERVENTION

Baclofen, a GABAergic medication, was given to the patient.

MAIN OUTCOME MEASURES

Eye movement recording of spontaneous nystagmus and postrotatory vestibular responses.

RESULTS

Baclofen was effective in suppressing PAN and improving postrotatory vestibular responses but not for improving cerebellar ataxia.

CONCLUSION

The presence of PAN and the response to baclofen provide a unique opportunity to suggest a direct role of GAD-Ab in cerebellar dysfunction in this patient.