Acute Pure Motor Cranial Polyneuropathy: A Rare Form of Guillain-Barré Syndrome

Guillain-Barré syndrome (GBS) typically presents with ascending flaccid paralysis, but variants with exclusive cranial nerve involvement are rare. We report an atypical case of GBS with isolated motor cranial nerve involvement. A 19-year-old female with no significant medical history presented with bilateral ptosis and diplopia, which progressed over 10 days to bilateral facial paresis, lingual and masseter weakness, and severe dysphagia. Neurological examination revealed symmetric involvement of cranial nerves III, IV, VI, VII, IX, and XII, without sensory or tendon reflex abnormalities. Nerve conduction studies showed absent motor responses in the facial nerve and blink reflex, along with repetitive distal compound muscle action potentials, initially suggestive of congenital myasthenia. These findings normalized after the discontinuation of acetylcholinesterase inhibitors. Assessment of the neuromuscular junction was normal. Electromyography revealed neurogenic changes in the masseters and genioglossus. Brain MRI and cerebrospinal fluid analysis were normal, and infectious serologies and autoimmune screening were negative. The patient was diagnosed with the oculo-pharyngeal variant of GBS. Despite treatment with intravenous immunoglobulin and five sessions of plasmapheresis, no significant improvement was observed in the short term. At six months, the patient continued to experience persistent ophthalmoparesis, dysphagia, and facial amyotrophy, requiring gastrostomy placement. This case highlights the rare oculo-pharyngeal variant of GBS, characterized by exclusive cranial nerve involvement, which poses diagnostic challenges and often leads to poor functional outcomes. Early recognition and prompt treatment are crucial to improving prognosis.