Neuromyelitis is a rare, chronic autoimmune disorder that primarily affects the central nervous system. This condition involves the body’s immune system mistakenly attacking its own healthy cells, particularly within the optic nerves and spinal cord. These attacks can lead to significant inflammation and damage, which may result in severe vision loss and paralysis. The disorder is also known as neuromyelitis optica spectrum disorder (NMOSD) or Devic disease.
Understanding Neuromyelitis
Neuromyelitis involves the immune system attacking central nervous system tissues. This often includes antibodies against aquaporin-4 (AQP4) water channels on astrocytes, or against myelin oligodendrocyte glycoprotein (MOG) on oligodendrocytes and myelin sheaths. The binding of these antibodies triggers inflammation and damage to nerve cells, particularly in the optic nerves, spinal cord, and sometimes parts of the brain or brainstem.
The disease primarily impacts the optic nerves, which transmit visual information, and the spinal cord, responsible for transmitting signals between the brain and body. Damage to these areas disrupts nerve signaling, leading to various neurological impairments. While neuromyelitis shares symptoms with multiple sclerosis (MS), it is a distinct condition with different underlying mechanisms and treatment approaches. Unlike MS, which often involves widespread demyelination, neuromyelitis typically causes more localized and severe inflammation in the optic nerves and spinal cord.
A key difference from MS is the presence of specific antibodies like AQP4-IgG or MOG-IgG in neuromyelitis. Neuromyelitis attacks also tend to be more severe, with a higher potential for cumulative disability from each episode. Brain lesions in neuromyelitis are less common and follow different patterns than those observed in MS.
Common Symptoms
Symptoms of neuromyelitis emerge during distinct attacks. Optic neuritis, or inflammation of the optic nerve, is a frequent manifestation. This can cause sudden, often severe vision loss in one or both eyes, eye pain, and a decrease in color perception. Vision changes usually worsen over a few days or weeks before reaching their peak.
Transverse myelitis, inflammation across the spinal cord, leads to symptoms below the affected spinal segment. Individuals may experience weakness or paralysis in the limbs, numbness, and tingling sensations. Bladder and bowel dysfunction, such as incontinence or difficulty emptying, are also common. Muscle spasms, stiffness, and sharp, shooting pains in the back or limbs may also occur.
Involvement of the brainstem or brain can lead to other specific symptoms. Persistent hiccups and severe nausea and vomiting, sometimes without an obvious gastrointestinal cause, indicate brainstem lesions. In rare cases, widespread brain involvement can result in confusion, seizures, or breathing difficulties. These attacks can recur over time, ranging from weeks to years apart, and each new attack can potentially lead to further neurological impairment.
Diagnosis Steps
Diagnosing neuromyelitis involves a thorough evaluation, combining clinical assessment with specific laboratory and imaging tests. Healthcare professionals consider a patient’s medical history and current symptoms, followed by a neurological examination to assess movement, sensation, coordination, and vision. This initial evaluation helps guide further diagnostic steps and distinguish neuromyelitis from other conditions.
Blood tests are a key part of diagnosis, detecting specific autoantibodies. The aquaporin-4 immunoglobulin G (AQP4-IgG) antibody is a biomarker present in about 70-75% of neuromyelitis cases. A myelin oligodendrocyte glycoprotein immunoglobulin G (MOG-IgG) antibody test may also be used to identify a related inflammatory disorder that mimics neuromyelitis. The presence of these antibodies helps confirm the diagnosis.
Magnetic resonance imaging (MRI) of the brain, optic nerves, and spinal cord provides detailed views of the central nervous system. MRI scans can reveal characteristic lesions or areas of inflammation and damage. For instance, spinal cord lesions often extend over three or more vertebral segments, a pattern distinct from many other conditions. A lumbar puncture, or spinal tap, involves collecting cerebrospinal fluid (CSF) from the lower back. Analysis of the CSF can show elevated white blood cell counts or immune system proteins, which further support a neuromyelitis diagnosis and help distinguish it from other neurological disorders.
Treatment Approaches
Treating neuromyelitis involves two main strategies: managing acute attacks and preventing future relapses. High-dose corticosteroids, often administered intravenously, are the primary treatment for acute attacks to reduce inflammation rapidly. These medications help calm the immune system’s overactivity and limit damage during an episode. For severe attacks that do not respond adequately to corticosteroids, plasma exchange (PLEX) is often employed.
Plasma exchange is a procedure where a portion of the patient’s blood plasma, containing harmful antibodies and inflammatory substances, is removed and replaced with a substitute solution or donor plasma. This process aims to clear circulating autoantibodies and other inflammatory mediators that contribute to the attack. Early initiation of plasma exchange in severe attacks is associated with improved outcomes.
Long-term management focuses on preventing future attacks, which can lead to cumulative disability. Various immunosuppressive therapies are used for this purpose, aiming to suppress the immune system’s attacks. Medications include azathioprine, which reduces immune cell activity, and rituximab, which targets B cells involved in antibody production. Newer biologic therapies, such as eculizumab, satralizumab, and inebilizumab, have received approval specifically for neuromyelitis. Eculizumab blocks complement, satralizumab interferes with interleukin-6 signaling, and inebilizumab depletes CD19-expressing B cells.
In addition to disease-modifying treatments, symptomatic management addresses ongoing issues like pain, muscle stiffness, or fatigue. Physical and occupational therapy can help with muscle weakness and mobility problems, while specific medications may be prescribed for nerve pain or spasms. These supportive therapies aim to improve daily function and quality of life for individuals living with neuromyelitis.