Bickerstaff Brainstem Encephalitis Presenting With Negative Anti-GM1 and Anti-GQ1B Antibodies.

A woman in her 60s initially presented with rapid-onset left-sided hemiparesis with later development of slurred speech and left-sided facial droop. Despite ruling out common causes, her condition rapidly progressed with the development of bilateral proximal weakness, ophthalmoplegia, ataxia, and pyramidal signs eventually leading to a cardiorespiratory arrest. Extensive investigations, including computerised tomography (CT), magnetic resonance imaging (MRI), and lumbar puncture (LP), were negative for infectious or vascular aetiologies. Nerve conduction studies (NCS) revealed severe peripheral nerve damage, and despite a provisional diagnosis of Guillain-Barré Syndrome (GBS), the clinical picture aligned more with Bickerstaff Brainstem Encephalitis (BBE) given the central nervous system (CNS) involvement, despite negative anti-GM1 and anti-GQ1b autoantibodies. Treatment involved ventilatory support, immunoglobulins, and steroids. This case report describes a rare and challenging presentation of BBE and reminds clinicians to have a systematic approach to a patient presenting with rapid onset neurological symptoms and that BBE is a clinical diagnosis.