Neuromyelitis Optica (NMO): When the Immune System Attacks the Eyes and Spinal Cord

Neuromyelitis Optica Spectrum Disorder (NMOSD), formerly Devic's disease, is an autoimmune inflammatory disease of the central nervous system that predominantly attacks the optic nerves (causing optic neuritis — vision loss in one or both eyes) and the spinal cord (causing transverse myelitis — limb weakness, sensory loss, and bladder dysfunction). Unlike MS, NMO attacks tend to be more severe, leave more residual disability, and are mediated by a specific antibody — anti-AQP4 (aquaporin-4) — that distinguishes NMO from MS.

Clinical Features

Optic neuritis in NMO: More severe than MS-associated optic neuritis — typically bilateral or sequential; severe vision loss; poor recovery. Transverse myelitis in NMO: Longitudinally extensive (involving 3 or more vertebral segments on MRI — LETM) — this length is a key distinguishing feature from MS. Produces severe bilateral leg weakness, sensory level, and severe bladder/bowel dysfunction. NMO attacks can cause permanent blindness or paraplegia — prevention of attacks is paramount.

Diagnosis

Anti-AQP4 antibody (serum or CSF): positive in 70–80% of NMOSD patients — highly specific. Anti-MOG antibody (AQP4-seronegative NMOSD is partially distinct — MOG antibody disease): positive in a significant proportion of seronegative cases. MRI brain (often normal or non-MS-like) and MRI spine (LETM). CSF: pleocytosis (white cells in the CSF — more so than typical MS).

Treatment

Acute attack: High-dose IV methylprednisolone (1g/day for 5 days); plasma exchange for severe attacks not responding to steroids. Maintenance prevention: Rituximab (anti-CD20 monoclonal antibody — depletes B cells that produce the AQP4 antibody) — most commonly used in India; azathioprine; mycophenolate mofetil; newer approved agents: eculizumab, inebilizumab, satralizumab. NOTE: MS immunomodulatory drugs (interferons, natalizumab, fingolimod) can worsen NMO — correct diagnosis before treatment is critical. Sri Anand CNC, Chanda Nagar, Hyderabad. Call +91 90633 66983.