Neuromyelitis Optica

What is neuromyelitis optica?

Neuromyelitis optica (NMO), also known as Devic’s disease, is a rare inflammatory and demyelinating disorder of the central nervous system (CNS) that primarily affects the spinal cord and optic nerves. It was first described by Eugène Devic in 1894. NMO is an autoimmune condition in which the immune system mistakenly attacks healthy tissue, specifically targeting the myelin sheath, the protective covering of the optic nerve and spinal cord. in 1894. 

Types of Neuromyelitis Optica

There are two main types of NMO:

1. Relapsing Neuromyelitis Optica:
- This form is characterized by an initial attack of optic neuritis and transverse myelitis, followed by multiple relapses over several years.
- Each attack can cause cumulative damage, sometimes leading to permanent disability due to damage to the optic nerve and/or spinal cord.
- This type affects females more frequently than males, with a ratio greater than 4:1.

2. Monophasic Neuromyelitis Optica:
- In this form, patients experience one or more attacks over a short period (days or weeks) without future relapses.
- This type affects both sexes equally.

Who is affected?

NMO can develop at any age, with two peak onset periods: one in childhood and another in adults in their 40s. Women are more commonly affected than men, with a ratio of over 4:1.

Symptoms of NMO?\

The most common symptoms of NMO include:

1. Optic neuritis:
- Inflammation and demyelination of the optic nerve, leading to vision impairment, eye pain, and sometimes complete vision loss in one or both eyes. movement pain. 

2. Transverse Myelitis:
- Inflammation of the spinal cord, causing weakness, numbness, and sensory disturbances in the limbs.
- Possible bladder and bowel dysfunction.
- The severity of symptoms depends on the extent and location of spinal cord inflammation.he spinal cord. 

Diagnosing NMO

Diagnosis of Optic Neuritis:
- A comprehensive medical evaluation, including blood tests, to rule out related conditions.
- Colour vision tests, such as the Ishihara colour chart and Farnsworth-Munsell hue tests, to assess colour blindness.
- Visual evoked potentials (VEP) to measure the speed of nerve signal transmission.

Diagnosis of Transverse Myelitis:
- Magnetic Resonance Imaging (MRI): Used to identify spinal cord lesions affecting three or more segments.
- Lumbar Puncture (Spinal Tap): A sample of cerebrospinal fluid is tested for elevated white blood cell levels and the presence of specific proteins associated with NMO.
- NMO-IgG Antibody Test: The presence of NMO-IgG (anti-Aquaporin-4 antibody) supports the diagnosis but is not mandatory.

Causes of NMO
NMO is an autoimmune disorder where the immune system mistakenly attacks healthy tissue. Researchers believe that NMO-IgG, an antibody found in over two-thirds of NMO patients, damages Aquaporin-4, a protein that regulates water balance in CNS cells. The exact cause of NMO remains unknown, but it may be triggered by infections or other environmental factors in genetically predisposed individuals.

Treatment for NMO

Although there is no cure for NMO, treatments focus on managing symptoms, stopping attacks, and preventing relapses.

Acute Treatment:
- High-dose corticosteroids (e.g., methylprednisolone) are used to reduce inflammation during an attack.
- Plasma exchange (plasmapheresis) may be used for severe cases that do not respond to steroids.

Long-Term Treatment:
- Immunosuppressive drugs (e.g., rituximab, azathioprine, mycophenolate mofetil) help prevent future attacks.
- Some patients may require long-term low-dose steroids if relapses occur frequently.

Symptom Management:
- Neuropathic pain, muscle spasms, stiffness, and bladder/bowel issues can be managed with medications and physical therapy.

What is the prognosis for individuals with NMO?

The course of NMO is unpredictable. Many individuals experience relapses that progressively damage the nervous system, leading to cumulative disability. Permanent limb weakness is common, and in severe cases, patients may lose vision in both eyes and mobility in their arms and legs. Respiratory failure due to spinal cord damage can be life-threatening.

Early diagnosis and treatment are crucial in preventing severe disability and improving the quality of life for those with NMO.