Neuromyelitis optica (NMO)

Neuromyelitis optica is a subacute demyelinating disease affecting the optic nerves and spinal cord. Bilateral optic neuritis and a spinal cord lesion present within the space of two to three months, with a variable subsequent course (1)

• became known as Devic disease following a seminal 1894 report
• Neuromyelitis optica was considered a monophasic disorder consisting of simultaneous bilateral optic neuritis and transverse myelitis
  • however relapsing cases were described in the 20th century

Neuromyelitis optica (NMO) is distinct from multiple sclerosis (MS) and is associated with serum aquaporin-4 immunoglobulin G antibodies (AQP4-IgG) (2)

• approximately 75% of patients have serum aquaporin-4 immunoglobulin G antibodies (3)
• nomenclature defines the unifying term NMO spectrum disorders (NMOSD)

Epidemiology:

• reported incidence and prevalence of NMOSD are dependent on geographical location and ethnicity
  • Asians and those of African ancestry are at increased risk, with high mortality rates reported in the latter (3)
  • incidence and prevalence of NMOSD ranges from 0.05-0.40 and 0.52-4.4 per 100,000 people respectively (3)

Diagnosis of neuromyelitis optica should be made by an appropriate specialist based on established up-to-date criteria (1).

• NMOSD is stratified further by serologic testing (NMOSD with or without AQP4-IgG)
  • core clinical characteristics required for patients with NMOSD with AQP4-IgG include clinical syndromes or MRI findings related to optic nerve, spinal cord, area postrema, other brainstem, diencephalic, or cerebral presentations
  • more stringent clinical criteria, with additional neuroimaging findings, are required for diagnosis of NMOSD without AQP4-IgG or when serologic testing is unavailable

Untreated, approximately 50% of NMOSD patients will be wheelchair users and blind, and a third will have died within 5 years of their first attack (3)

Unlike multiple sclerosis, a progressive clinical course is very unusual and the accrual of disability is related to relapses.

Management (3):

• relapses are treated aggressively to prevent residual disability with high-dose steroids and often plasma exchange
• relapse prevention is achieved with long-term immunosuppression.

Reference:

• NICE (October 2014). Multiple sclerosis management of multiple sclerosis in primary and secondary care.
• Wingerchuk DM et al. International consensus diagnostic criteria for neuromyelitis optica spectrum disorders.Neurology. 2015 Jul 14; 85(2): 177-189.
• Huda S et al. Neuromyelitis optica spectrum disorders.Clin Med (Lond). 2019 Mar; 19(2): 169176.