Atypical Overlap Presentation in Guillain-Barré Syndrome: Lessons From a Case Report.

Guillain-Barré syndrome (GBS) is an acute, immune-mediated polyradiculoneuropathy characterized by rapidly progressive limb weakness and areflexia. While the classical form is well-recognized, variants such as Miller Fisher syndrome (MFS) and Bickerstaff brainstem encephalitis (BBE) also exist, each with distinct clinical features. Rarely, these syndromes may present in combination, forming GBS-MFS-BBE overlap syndromes. These atypical presentations pose significant diagnostic challenges that may delay the initiation of appropriate treatment. We report the case of a 60-year-old male who initially presented with pain and weakness of the left upper limb, which progressed rapidly over 72 hours to symmetrical quadriplegia, bulbar dysfunction (including dysphagia and dysarthria), complete ophthalmoplegia, and altered sensorium suggestive of encephalopathy. Neurological examination revealed areflexia and bilateral facial weakness. Initial nerve conduction studies (NCSs) indicated a possible axonal plexopathy; however, follow-up NCSs performed on day 5 showed findings consistent with acute inflammatory demyelinating polyneuropathy. Given the combination of ophthalmoplegia, ataxia, encephalopathy, and demyelinating features, the diagnosis of a GBS-MFS-BBE overlap syndrome was made. The patient was treated with intravenous immunoglobulin (IVIG) at a total dose of 2 g/kg administered over five days. Due to progressive respiratory failure, he required mechanical ventilation. Supportive care included intensive monitoring and physiotherapy. Neurological recovery was gradual, with successful weaning from the ventilator by day 25. At discharge on day 30, the patient had improved to a Medical Research Council (MRC) grade of 3/5 in all four limbs. This case illustrates the clinical complexity and diagnostic uncertainty associated with GBS-MFS-BBE overlap syndromes. Early recognition and prompt initiation of immunotherapy, such as IVIG, are essential to improving outcomes and reducing long-term morbidity. Clinicians should maintain a high index of suspicion for atypical features, particularly in rapidly evolving neuromuscular presentations.