Isolated acquired external ophthalmoplegia without presence of anti-GQ1b IgG antibody: a case report of Miller Fisher syndrome (MFS)

Background: MFS is a rare differential diagnosis of acquired ophthalmoplegia and ptosis. Classified as a variant of Guillain-Barré syndrome, MFS comprises the clinical triad of ataxia, areflexia, and ophthalmoplegia. Pathogenetic aspects of MFS continue to be a matter of debate.

Case report: We report on a 17-year old Turkish male patient (non-consanguineous parents) presented with acute onset of diplopia due to an isolated paralysis of the rectus inferior muscle of the left eye. Extensive work-up including MRI, EEG, CSF and blood analysis as well as ophthalmological examination was performed. Due to thickening and signal enhancement of the rectus inferior extraocular muscles found by MRI endocrine orbitopathy was suspected, initially. Within two weeks our patient showed clinical progression developing paralysis of the right abducens nerve and ptosis on both sides. Repeated examination of CSF showed albuminocytological dissociation with a significant elevation of CSF protein. The patient received intravenous immunoglobulins 400mg/kg body weight/day for 5d. Within several days he responded to treatment and showed complete clinical remission within 3 weeks.

Conclusion: Clinical and CSF findings as well as response to treatment led to the final diagnosis of MFS. Interestingly, our patient had no significant elevation of CSF protein or detectable anti-GQ1b IgG antibodies at onset of ophthalmoplegia. Our case report supports that MSF associated with variable clinical presentation should be considered in the differential diagnosis of acquired isolated external ophthalmoplegia even if characteristic CSF finding is not present at the time of initial manifestation.