Case Report: Guillain-Barré syndrome mimicking acute brainstem stroke with severe autonomic dysfunction-complete recovery after early plasma exchange.

Acute onset of bilateral ptosis, bulbar palsy, and quadriparesis typically raises suspicion for brainstem infarction. However, when neuroimaging is unrevealing, immune-mediated neuropathies such as Guillain-Barré syndrome (GBS) should be considered. This case highlights the diagnostic challenge and therapeutic response in a seronegative, rapidly progressive GBS variant with severe autonomic involvement. We report a 57-year-old previously healthy man who presented with acute right-sided weakness and dysarthria, progressing over 36 hours to bilateral ptosis, complete ophthalmoplegia, dilated pupils, bulbar palsy, flaccid quadriparesis, urinary retention, and paralytic ileus. Initial brain MRI-DWI was negative. CSF showed no albuminocytologic dissociation. Anti-ganglioside antibodies and neuromuscular junction antibodies were negative. Electromyography revealed motor-predominant polyneuropathy with sympathetic skin response abnormalities. A diagnosis of atypical GBS with severe autonomic involvement was made. Plasma exchange was initiated at 40 hours after onset, followed by a second session on day 5. The patient improved dramatically, walked independently by day 8, was discharged on day 15, and achieved complete recovery at 1 month. This case demonstrates that GBS can present as an acute brainstem stroke mimic with severe ileus and urinary retention, even in the absence of CSF abnormalities or detectable autoantibodies. Early plasma exchange may result in complete neurological recovery. Therefore, clinicians should maintain a high clinical suspicion for immune-mediated neuropathies in patients presenting with rapidly progressive stroke mimics accompanied by autonomic dysfunction.