Neuromyelitis Optica Spectrum Disorder (NMOSD): Diagnosis, Treatment & Prognosis

Neuromyelitis optica spectrum disorder (NMOSD, formerly Devic disease) is an autoimmune astrocytopathy targeting aquaporin‑4 (AQP4) water channels on astrocytes. It primarily affects the optic nerves and spinal cord, with variable brain involvement.

Core Clinical Features

• Optic neuritis: unilateral/bilateral vision loss, pain with eye movement.
• Acute transverse myelitis: flaccid weakness, sensory level, bladder/bowel dysfunction; often longitudinally extensive (≥3 vertebral segments).
• Area postrema syndrome: intractable nausea, vomiting, hiccups.
• Brainstem syndrome: dysphagia, facial palsy, nystagmus, respiratory failure.
• Narcolepsy / diencephalic syndrome: hypothalamic lesions.

Diagnostic Criteria (2015 IPND)

• AQP4‑IgG positive: one core characteristic + positive serology (cell‑based assay).
• AQP4‑IgG negative / unknown: two core characteristics (one must be optic neuritis, myelitis, or area postrema syndrome) + MRI requirements (e.g., longitudinal extensive transverse myelitis lesion).
• Exclusion of alternative diagnoses (MS, MOGAD, infections, etc.).

Treatment

Acute Attack

• High‑dose IV methylprednisolone 1 g/day × 3–5 days.
• Plasma exchange (PLEX) if incomplete response; early PLEX improves recovery.

Relapse Prevention (Long‑Term Immunosuppression)

• FDA‑approved: eculizumab (anti‑C5), satralizumab (anti‑IL‑6R), inebilizumab (anti‑CD19).
• Off‑label mainstays: rituximab (anti‑CD20), mycophenolate mofetil, azathioprine, tocilizumab.
• Monitor: CBC, LFTs, immunoglobulins, infection screening.

Symptomatic & Rehabilitative

• Neuropathic pain: gabapentinoids, SNRIs.
• Spasticity: baclofen, tizanidine, botulinum toxin.
• Bladder/bowel: anticholinergics, CIC, bowel program.
• Physical/occupational therapy, low‑vision aids.

Prognosis

• Relapsing course in >90% (if untreated).
• Disability accrues with each attack; early effective immunosuppression preserves function.
• AQP4‑IgG positivity, older onset, and myelitis severity predict worse outcome.