A 25-year-old woman develops bilateral lower limb weakness, urinary retention, and a sensory level at T6 over 48 hours. MRI spine shows a longitudinally extensive transverse myelitis (LETM) spanning 3 vertebral segments. MRI brain is normal. Serum AQP4-IgG (NMO-IgG) is positive. Which diagnosis is most likely?

• A Multiple sclerosis
• B MOG antibody-associated disease
• C Acute disseminated encephalomyelitis (ADEM)
• D Neuromyelitis optica spectrum disorder (NMOSD) ✓

Explanation

Longitudinally extensive transverse myelitis (≥3 vertebral segments) with positive AQP4-IgG (NMO-IgG) is diagnostic of neuromyelitis optica spectrum disorder (NMOSD). MS lesions are typically short (<2 segments), asymmetric, and peripherally located. MOG antibody disease can also cause LETM but is AQP4-IgG negative. ADEM typically follows infection or vaccination, affects brain predominantly, and occurs in children.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.