The Brainstem Under Siege

A 28-year-old man presents to the emergency department of a hospital in Ho Chi Minh City with three days of fever, sore throat, and painful oral ulcers. His five-year-old nephew recovered from hand-foot-and-mouth disease two weeks ago, and the patient recalls similar small vesicles on his palms that have since faded. He was diagnosed with granulomatosis with polyangiitis eight months ago, currently in remission on rituximab maintenance therapy (last infusion six weeks ago, CD19-positive B cells undetectable) and prednisone 5 mg daily. He has no other medical history.

This morning he developed intermittent jerking of his arms and legs that woke him from sleep. His wife noticed his eyes were "not moving properly" and that he was stumbling when walking. Over the next several hours he became progressively dysarthric and began drooling, unable to swallow his saliva. On arrival to the emergency department he is tachycardic to 142 bpm, blood pressure 178/104 mmHg, respiratory rate 32, temperature 38.6°C. He is alert but dysarthric, with bilateral sixth nerve palsies, left facial weakness, and absent gag reflex. He has frequent myoclonic jerks involving all four extremities and is ataxic when attempting to sit. Plantar responses are flexor. There is no meningismus. His palms show faint resolving macular lesions; no active vesicles are present.

Laboratory studies reveal a white blood cell count of 11,200/μL (neutrophils 82%, lymphocytes 11%), hemoglobin 12.8 g/dL, and platelet count 198,000/μL. Serum sodium is 139 mEq/L, creatinine 0.9 mg/dL. CRP is 4.2 mg/dL. A lumbar puncture reveals an opening pressure of 240 mmH₂O, CSF white blood cell count 52/μL (78% lymphocytes), protein 71 mg/dL, and glucose 62 mg/dL (serum glucose 108 mg/dL). CSF Gram stain shows no organisms.

MRI of the brain with and without gadolinium is performed.