Makindo Medical Notes

Related Subjects: |Neurological History taking |Motor Neuron Disease (MND-ALS) |Miller-Fisher syndrome |Guillain Barre Syndrome |Multifocal Motor Neuropathy with Conduction block | Multiple Sclerosis (MS) Demyelination | Transverse myelitis | Acute Disseminated Encephalomyelitis | Inclusion Body Myositis |Cervical spondylosis |Anterior Spinal Cord syndrome |Central Spinal Cord syndrome |Brown-Sequard Spinal Cord syndrome |Spinal Cord Compression |Spinal Cord Haematoma |Spinal Cord Infarction

Neuromyelitis optica (NMO) differs from multiple sclerosis (MS) as it primarily targets astrocytes rather than myelin sheaths.

About

• Relapsing CNS demyelinating disease distinct from MS.
• NMO is an autoimmune, inflammatory disorder affecting the CNS, primarily impacting the optic nerves and spinal cord.
• Most common in young females.

Aetiology

• The disease is an astrocytopathy where autoantibodies target astrocytes in the CNS.
• Associated with autoimmune conditions like Sjogren's syndrome and systemic lupus erythematosus (SLE).

Key Features

• Severe myelopathy with MRI showing longitudinally extensive spinal cord lesions.
• Bilateral optic neuritis, often severe, sometimes with optic nerve swelling or chiasm involvement.
• Intractable hiccups, nausea, or vomiting lasting over 2 days, often linked to medullary lesions on MRI.

Clinical Presentation

• Upper motor neuron (UMN) weakness below the lesion level.
• Sensory level and UMN sphincter weakness based on lesion location.
• Visual loss (may be bilateral) and afferent pupillary defect.
• Intractable nausea and vomiting.
• Positive Romberg's sign and Lhermitte's phenomenon.

Affected Areas

• Optic nerve, spinal cord, area postrema of the dorsal medulla.
• Brainstem, diencephalon, periependymal areas, corpus callosum, internal capsule, and subcortical white matter.

Investigations

• Hyponatremia may be observed due to SIADH.
• Serum aquaporin-4 (AQP4) autoantibodies are common; seropositive patients tend to have a relapsing disease course.
• Anti-MOG antibodies in around 20% of cases.
• MRI: lesions often span over 3 spinal segments, are centrally located, and may enhance with contrast.
• Visually evoked potential (VEP) may indicate optic neuropathy.
• CSF: absence of oligoclonal IgG bands, differentiating from MS.

Comparing MS and NMO

• NMO typically has a monophasic course, unlike the relapsing-remitting nature of MS.
• NMO attacks are often more severe with lasting disability, and MRI of the brain may appear normal.
• CSF oligoclonal bands are typically absent in NMO.
• MS treatments, including interferon-ß, can exacerbate NMO.
• NMO often features detectable antibodies targeting AQP4.

Wingerchuk Diagnostic Criteria

• Required Criteria:
  • Optic neuritis
  • Acute transverse myelitis
• Supportive Criteria: (two out of three)
  • Longitudinal spinal cord involvement of more than three vertebral segments
  • MRI brain not meeting criteria for MS
  • Aquaporin-4 seropositivity

Management

• Acute Management: Prompt intervention with corticosteroids, often starting with 1g of IV methylprednisolone for 5 days, followed by a tapering course of oral prednisone.
• Plasma Exchange (PLEX): Considered for aggressive attacks, typically 5-7 exchanges over two weeks.
• Immunosuppressants: Azathioprine or Rituximab (anti-CD20) may help in relapse prevention.
• Supportive Care: Rehabilitation for residual neurological deficits. Pain, fatigue, and muscle spasticity require tailored treatments, such as carbamazepine for tonic spasms.

References

• Current concept of neuromyelitis optica (NMO) and NMO spectrum disorders