Combined central and peripheral nervous system involvement in acute disseminated encephalomyelitis in a young male: A case report.

RATIONALE: Acute disseminated encephalomyelitis (ADEM) is an autoimmune demyelinating disorder of the central nervous system, typically presenting after infection or vaccination. Rarely, ADEM may involve the peripheral nervous system, presenting with pure motor axonal neuropathy, which poses a diagnostic and therapeutic challenge. PATIENT CONCERNS: We report a 22-year-old Asian male with no prior medical history who initially experienced a mild upper respiratory infection followed by headache and a single generalized tonic-clonic seizure. He subsequently developed altered consciousness and flaccid paraplegia. DIAGNOSES: Brain magnetic resonance imaging demonstrated asymmetric, poorly marginated supratentorial white-matter hyperintensities on T2-weighted and fluid-attenuated inversion recovery sequences. Cerebrospinal fluid analysis revealed mild lymphocytic pleocytosis and elevated protein, while autoimmune encephalitis panels and infectious studies were negative. Nerve conduction studies revealed predominantly motor axonal neuropathy affecting the lower limbs, with sensory sparing. INTERVENTIONS: The patient received high-dose intravenous methylprednisolone followed by therapeutic plasma exchange due to incomplete motor recovery. OUTCOMES: After 2 weeks, he regained the ability to stand and ambulate with support, and repeat magnetic resonance imaging at 3 months demonstrated complete resolution of the lesions. LESSONS: This case highlights a rare presentation of ADEM with peripheral nervous system involvement in a young adult, distinguished by predominant motor axonal neuropathy and a favorable response to plasma exchange. Recognition of peripheral involvement in ADEM is essential, particularly in younger patients with persistent weakness despite corticosteroid therapy, as timely diagnosis and intervention can significantly improve functional outcomes.