Overlapping Miller Fisher Syndrome and Pharyngeal–Cervical–Brachial Variant of Guillain–Barré Syndrome Following Seasonal Influenza Vaccination: A Case Report

Guillain-Barré syndrome (GBS) covers a broad spectrum of immune-mediated nerve disorders, including regional subtypes such as Miller Fisher syndrome (MFS) and the pharyngeal-cervical-brachial (PCB) variant.Overlapping features of these variants are recognized but remain uncommon.While it is established that flu vaccination carries a small increased GBS risk, post-vaccination MFS is rare, with overlap presentations being even less frequently reported.A 28-year-old man with no prior medical issues presented with neurological symptoms six days after receiving a seasonal influenza vaccine.His initial presentation included acute bulbar impairment with dysarthria and dysphagia, marked neck weakness causing head drop, binocular diplopia, and distal paresthesia.Examination revealed bilateral ptosis, facial diplegia, left abducens nerve palsy, hypoglossal weakness, limb and gait ataxia, and generalized areflexia.Limb power remained fully preserved.Brain magnetic resonance imaging showed no acute abnormalities.Cerebrospinal fluid analysis demonstrated albuminocytologic dissociation (protein 0.98 g/L).Nerve conduction studies and electromyography identified severe acute motor denervation involving the cranial, cervical, and proximal upper limb muscles, with preserved sensory responses.These findings supported the diagnosis of overlapping MFS and the PCB variant of GBS.Treatment consisted of intravenous immunoglobulin (2 g/kg administered over five days) together with nasogastric feeding because of severe bulbar dysfunction.He made a gradual but significant recovery, with only mild residual imbalance and lagophthalmos at the two-month follow-up.This case highlights a rare overlap of MFS and PCB variants presenting shortly after influenza vaccination, although causality cannot be established.This case highlights the need to think of GBS spectrum disorders in patients who have acute bulbar and oculomotor problems, even with preserved limb strength.Early diagnosis is paramount, as it allows for vigilant monitoring and proactive management of life-threatening sequelae, including respiratory insufficiency and aspiration pneumonia.