Demyelinating and neuroimmunologic disorders
Demyelinating and neuroimmunologic disorders
The exam tests MRI dissemination criteria, antibody syndromes, acute immunotherapy, and maintenance choices in MS, NMOSD, MOGAD, and autoimmune encephalitis. MS requires dissemination in space and time, supported by CSF oligoclonal bands and typical lesions. Neuromyelitis optica spectrum disorder is associated with AQP4-IgG and causes optic neuritis, longitudinally extensive myelitis, and area postrema syndrome. MOGAD often causes optic neuritis, ADEM-like presentations, and MOG-IgG positivity. Autoimmune encephalitis, especially anti-NMDAR, presents with psychiatric symptoms, seizures, dyskinesias, and autonomic instability. Acute attacks use high-dose steroids and sometimes plasma exchange.
Worked example
A 30-year-old has bilateral optic neuritis and intractable vomiting. MRI shows a longitudinally extensive cord lesion; AQP4-IgG is positive. Reasoning: NMOSD, not MS. Treat the attack with IV methylprednisolone and consider plasma exchange; avoid MS disease-modifying drugs that can worsen NMOSD.
Traps
Do not diagnose MS from a single attack without DIS/DIT; do not miss area postrema syndrome; do not use MS therapies in AQP4-positive NMOSD; remember that early HSV encephalitis can mimic autoimmune encephalitis and requires acyclovir until excluded.