Demyelinating and Neuroimmunological Disorders
The central skill here is separating multiple sclerosis from the antibody-mediated disorders, because treatment errors in neuromyelitis optica are dangerous.
Multiple sclerosis (McDonald 2017)
Dissemination in space needs T2 lesions in at least two of four regions: periventricular, cortical or juxtacortical, infratentorial, and spinal cord. Dissemination in time needs a new lesion on follow-up imaging, simultaneous enhancing and non-enhancing lesions, or CSF-specific oligoclonal bands substituting for time. Typical patients are women aged 20 to 40 with optic neuritis, sensory symptoms or brainstem syndromes. MRI shows ovoid periventricular lesions (Dawson fingers).
Acute relapse: intravenous methylprednisolone 1 g daily for three to five days, which hastens recovery but does not change long-term outcome. Disease-modifying therapy includes interferons, glatiramer, teriflunomide, dimethyl fumarate, natalizumab, ocrelizumab and alemtuzumab.
Neuromyelitis optica spectrum disorder
Aquaporin-4 antibodies, severe optic neuritis, longitudinally extensive transverse myelitis of three or more segments, area postrema syndrome with intractable vomiting and hiccups, and brainstem syndromes. Interferon-beta and fingolimod can worsen the disease; use azathioprine, rituximab, eculizumab or inebilizumab. MOG antibody disease often causes optic neuritis with disc swelling and tends to relapse less.
Worked example
A 32-year-old woman has four days of intractable vomiting and hiccups, then paraparesis. MRI shows an area postrema lesion and a five-segment cord lesion, and aquaporin-4 antibodies are positive. The diagnosis is neuromyelitis optica spectrum disorder: treat the attack with intravenous steroids and consider plasma exchange, then start rituximab and avoid interferon-beta.
Traps
Diagnosing MS after a single attack without dissemination; overlooking oligoclonal bands as a time criterion; giving interferon or fingolimod to an aquaporin-4 positive patient.