Overlapping Miller Fisher Syndrome, Bickerstaff Brainstem Encephalitis, and Guillain-Barré Syndrome without glycolipid antibodies-a case report and literature review.

We present a rare case of a 56-year-old female presenting with overlapping features of Miller Fisher syndrome (MFS), Bickerstaff's brainstem encephalitis (BBE) and Guillain-Barré syndrome (GBS), despite seronegativity for anti-GQ1b, GM1, GD1b, GT1a, and GT1b IgG antibodies. The patient developed sequential neurological deficits (ophthalmoplegia, ataxia, tetraparesis, and altered consciousness) following an upper respiratory infection. Electrophysiological studies confirmed acute motor-sensory axonal neuropathy, while cerebrospinal fluid analysis showed albuminocytological dissociation. Dual intravenous immunoglobulin (IVIG) courses and methylprednisolone therapy led to partial recovery, with independent ambulation achieved by day 76. This case underscores the complexity of overlapping anti-GQ1b antibody syndromes and highlights the need for alternative diagnostic biomarkers in seronegative patients.