Diagnostic value of anti-GQ1b antibodies in a patient with relapsing dysarthria and ataxia.

Serum antibodies to the ganglioside GQ1b are associated with immune-mediated ophthalmoplegia and ataxia in patients with Miller-Fisher syndrome (MFS) and Guillain-Barré syndrome. A patient with two clinically similar episodes of progressive bulbar signs, ophthalmoplegia and ataxia is reported here. During both episodes the patient required artificial ventilation. Serum anti-GQ1b antibodies were detected during the first episode compatible with MFS, but were absent during the second. Neuroradiological investigations during the second episode showed brain stem ischaemia and obstruction of the left posterior inferior cerebral artery. These findings illustrate that anti-GQ1b serology is a reliable and robust method that helped to distinguish between different causes of relapsing dysarthria and ataxia.