Isolated Ophthalmoplegia as an Atypical Manifestation of Miller Fisher Syndrome Post-viral Conjunctivitis.

Miller Fisher syndrome (MFS) is an uncommon variant of Guillain-Barré syndrome, typically identified by the presence of ophthalmoplegia, ataxia, and areflexia. While most cases follow this clinical pattern, atypical presentations lacking one or more components can complicate diagnosis. We report the case of an 81-year-old male with well-controlled hypertension who presented with acute-onset horizontal diplopia two weeks after a self-limiting episode of viral conjunctivitis. Neurological examination revealed complete bilateral ophthalmoplegia with preserved pupillary reflexes and no other focal deficits. Brain imaging and CSF analysis were unremarkable, with no evidence of albuminocytologic dissociation. A comprehensive serologic and autoimmune workup was negative, except for markedly elevated anti-GQ1b IgG titers (>1:12,800). The patient was diagnosed with an atypical form of MFS and received a five-day course of IVIG, which led to complete symptom resolution within one week. This case underscores the importance of considering MFS even in the absence of its full clinical triad. Anti-GQ1b IgG seropositivity remains a key diagnostic marker, and early treatment with IVIG can result in rapid and complete recovery. Clinicians should maintain a high index of suspicion for atypical MFS presentations, especially in patients presenting with isolated cranial nerve findings following a viral illness.