Question

Describe the clinical features, diagnostic criteria, differential diagnosis, and management of neuromyelitis optica spectrum disorders.

Hint:

Early diagnosis and prompt treatment of acute attacks are essential to prevent long-term disability in patients with NMOSD.

Answer 1

Neuromyelitis optica spectrum disorders (NMOSD) are a group of autoimmune demyelinating disorders primarily affecting the optic nerves and spinal cord. They are characterized by the presence of autoantibodies targeting aquaporin-4 (AQP4).
Step 1: Clinical Features:
1. Optic Neuritis: Acute vision loss in one or both eyes, often accompanied by pain on eye movement.
2. Transverse Myelitis: Sudden onset of weakness, sensory disturbances, and bowel or bladder dysfunction due to inflammation of the spinal cord.
3. Other Symptoms: Patients may also experience nausea, vomiting, respiratory failure, or seizures in severe cases.
Step 2: Diagnostic Criteria:
1. Serological Testing: Detection of anti-AQP4 antibodies is a hallmark of NMOSD, although a small percentage of patients may be seronegative.
2. MRI of the Brain and Spinal Cord: MRI typically shows lesions in the optic nerves, spinal cord, and sometimes the brain. Lesions are often longitudinally extensive.
3. Clinical Manifestations: Two or more episodes of optic neuritis or transverse myelitis, along with the presence of anti-AQP4 antibodies, confirm the diagnosis.
Step 3: Differential Diagnosis:
1. Multiple Sclerosis (MS): MS also presents with optic neuritis and myelitis, but it typically involves multiple areas of the CNS and does not involve AQP4 antibodies.
2. Systemic Lupus Erythematosus (SLE): SLE can present with neurologic symptoms, but it often involves a more diffuse pattern of CNS involvement.
3. Infections and Vascular Causes: These may mimic NMOSD, especially when there is transverse myelitis or optic neuritis.
Step 4: Management:
1. Acute Attack Treatment: High-dose corticosteroids (e.g., methylprednisolone) are used for acute attacks to reduce inflammation.
2. Plasmapheresis or IVIG: In cases of refractory disease, plasmapheresis or intravenous immunoglobulin (IVIG) may be used.
3. Chronic Management: Long-term immunosuppressive therapy, including azathioprine, mycophenolate mofetil, rituximab, or eculizumab, is used to prevent relapses.