Miller-Fisher syndrome (MFS) is a rare variant of Guillain- Barré syndrome (GBS) and is characterized by the clinical triad of ataxia, ophthalmoplegia, and areflexia. The incidence rate in Thailand has not been established but it occurred approximately 1-5% that of GBS. Here, the authors report a Thai patient diagnosed as MFS that had a positive test of antibodies against the ganglioside GQ1b. These antibodies have diagnostic and pathogenic importance to MFS because of high sensitivity and specificity. All other investigations, such as cerebrospinal fluid analysis, electrophysiological studies, and imaging studies had no significant abnormalities. The patient was successfully treated with intravenous immunoglobulin and fully recovered within one month. After eighteen months follow-up, he is still healthy and has had no recurrent symptoms.

Keywords: Miller Fisher syndrome, Guillain- Barré syndrome, Anti-ganglioside, GQ1b, Immunoglobulin