Osmotic Demyelination Syndrome: A New Mime in the Circus of Neurology

Abstract

A 34-year-old man with end-stage kidney disease presented with new onset blood pressure lability, acute gait difficulties, bilateral leg weakness, hypersomnia, fecal incontinence, and urinary retention within 2 weeks of starting dialysis. His maximum urea was 40 mmol/L, and he was gently dialyzed with three short runs, leading to a 50% reduction in his urea over 3 days. His initial mild hyponatremia (132 mmol/L) was slowly corrected.Examination revealed proximal hip flexor weakness (4/5), mild vibration loss distally, 1 + Achilles and patellar reflexes, and equivocal plantar reflexes with no saddle anesthesia. Upper extremities and coordination were normal. A computed tomography (CT) of the brain was unremarkable (Figure 1A). Full spinal magnetic resonance imaging (MRI) was performed, revealing mild radicular involvement in L4-L5 (Figure 1B), inconsistent with cauda equina syndrome (CES).Given his proximal-predominant weakness, blood pressure lability, and urinary/bowel involvement, differential diagnosis