Neuromyelitis optica is an autoimmune disease of the central nervous system that predominantly affects the optic nerve and the spinal cord. Neuromyelitis optica is now known as neuromyelitis optica spectrum disorder after the seropositivity of AQP4-IgG (aquaporin 4 immunoglobulin G) antibodies. Earlier to that it was considered to be a variant of multiple sclerosis. Neuromyelitis optica spectrum disorder comprises approximately 20% of all demyelinating disorders in India with a prevalence of 2.6 per 100,000 populations. The age of onset of the disease is in the third and fourth decade of life and is more prevalent in females than in males, especially in the relapsing disease.(1)
Approximately 70-80% of all cases are strongly linked to anti-AQP4-IgG that are produced by plasma cells by an unknown mechanism. It is worth noting that anti-AQP4-IgG 33% of attacks occur after a vaccination or a fever. Genetic studies have shown that neuromyelitis optica is associated with an aberration in HLA-DRB1(03) gene in Indian population. Although most of the cases of neuromyelitis optics are sporadic, a few familial cases have also been noted.(1)
How Dangerous Is Neuromyelitis Optica & Is It Contagious?
Neuromyelitis optica progressively causes vision, motor, sensory and bladder impairment due to recurrent attacks. Most of the attacks worsen over days and recovery takes place in several weeks to months with significant impairment left by each attack. The worse outcome is noted people with a greater number of relapses within the first two years of the disease, severity of the first attack, disease onset at an older age, seropositivity with AQP4-IgG autoantibody, and when it is associated with other autoimmune diseases.(2)
Neuromyelitis optica is associated with higher mortality rates due to neurogenic respiratory failure that occurs when cervical lesions extend into the brainstem or when primary brainstem lesions extend further. The deaths associated with neuromyelitis optica ranges from 25-50 % in North American, Brazilian and French West Indies people.(2)
The greater awareness of the disease in the recent years, access to anti-AQP4-IgG testing and long term treatment with immunosuppressants has greatly improved the mortality rates of the disease that has improved from 30% at 5 years to 9% at 6 years.(1)
The AQP4-IgG autoantibody may be considered a marker for the course of the disease and its prognosis. Retrospective studies have linked seropositivity of the antibody to the poor visual outcome and disease development. Some studies have suggested the antibody seropositivity to greater relapse within one year and some studies with no long term sequelae associated with the seropositivity.(1)
However, the disease is not contagious as it is an autoimmune disease.
Presentation Of Neuromyelitis Optica
The most common features of neuromyelitis optica include acute severe optic neuritis and longitudinally extensive transverse myelitis (LETM). Longitudinally extensive transverse myelitis is defined as longitudinal cord lesions present in more than 3 vertebral segments. Mostly the first attack is either of optic neuritis or transverse myelitis; both the symptoms of optic neuritis and transverse myelitis are seen in about 15-40% cases. Although it is difficult to differentiate between optic neuritis in neuromyelitis optica and multiple sclerosis, the optic neuritis associated with neuromyelitis optica is severer with impaired vision, concurrent bilateral involvement of eyes in rapid succession.
Spinal cord lesions lead to total paralysis of all the four extremities or of two extremities along with sensory involvement and bladder dysfunction.(1)
Other presenting symptoms include neuropathic pain, tonic spasms, Lhermitte’s sign, seizures, hyposmia, meningoencephalitis, posterior reversible encephalopathy syndrome, cognitive dysfunction, myeloradiculopathy, ophthalmoplegia, myocarditis, and muscular edema. Brainstem involvement includes hiccups, vomiting, narcolepsy, increased daytime somnolence, hypothermia, and even respiratory failure. Non-neurological manifestations of neuromyelitis optica include placentitis with the risk of abortion, internal otitis, and gastritis. Approximately 30-40% of patients with neuromyelitis optica have associated autoimmune disorders including Sjogren’s syndrome, systemic lupus erythematosus, myasthenia gravis, autoimmune thyroid disease, autoimmune encephalitis, autoimmune-mediated vitamin B12 deficiency, and others.(1)
- Neuromyelitis Optica (NMO) or Devic’s Syndrome: Causes, Symptoms, Treatment, Prognosis
- Can Neuromyelitis Optica Be Cured?
- Difference Between Neuromyelitis Optica and Multiple Sclerosis
- Is Neuromyelitis Optica An Inherited Disorder?