Acute Isolated Abducens Nerve Palsy Associated with Anti-GM1 IgM: A Rare Guillain-Barré Syndrome (GBS) Variant

Acute ophthalmoparesis may occur in variants of Guillain-Barré Syndrome (GBS) associated with anti-GQ1b antibodies. Miller Fisher Syndrome, the most common ocular variant, is characterized by a triad of ophthalmoplegia, ataxia, and areflexia. In contrast, isolated ophthalmoparesis without ataxia is rare. Here, we report a case of a 56 year old man with a post-infectious acute unilateral isolated abducens nerve palsy without ataxia associated with elevated anti-GM1 IgM and normal anti-GQ1b antibodies. The patient initially presented with septic arthritis of his left knee 1 month after ACL repair and subsequently developed blurry vision upon left gaze. Neurological exam identified an abducens nerve palsy without other motor or sensory deficits. Imaging was unremarkable. Cerebrospinal fluid analysis revealed albuminocytologic dissociation with elevated protein (100 mg/dL) and normal cell counts. Serum ganglioside (GM1) antibody titers revealed increased anti-GM1 IgM (1:1600) and anti-asialo-GM1 IgM (1:3200). The patient declined immunotherapy and was discharged with neuro-ophthalmology follow-up and antibiotic therapy for septic arthritis. This case highlights a rare GBS variant of acute ophthalmoparesis without ataxia associated with anti-GM1 antibodies. Recognition of atypical presentations supports earlier use of ganglioside antibody testing and further investigation into the role of anti-GM1 antibodies with immune-mediated ophthalmoparesis.