Differential Diagnosis for ADEM and MoGAD

When differentiating between Acute Disseminated Encephalomyelitis (ADEM) and Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MoGAD), it's crucial to consider various factors, including clinical presentation, imaging findings, and serological tests. Here's a structured approach to the differential diagnosis:

• Single Most Likely Diagnosis

  • ADEM: This is often considered in the context of a monophasic illness with multifocal neurological symptoms and signs, following a viral infection or vaccination, with characteristic MRI findings of widespread demyelination.
  • MoGAD: If the patient presents with optic neuritis, myelitis, or brainstem encephalitis, and is found to have MoG antibodies, MoGAD becomes the single most likely diagnosis due to its specific serological marker.

• Other Likely Diagnoses

  • Multiple Sclerosis (MS): Especially if the patient has a relapsing-remitting course or lesions disseminated in time and space on MRI, MS should be considered, although the presence of MoG antibodies would argue against this.
  • Neuromyelitis Optica Spectrum Disorder (NMOSD): If the patient has aquaporin-4 antibodies and presents with optic neuritis and/or myelitis, NMOSD is a strong consideration.
  • Clinically Isolated Syndrome (CIS): A first episode of neurologic symptoms that lasts at least 24 hours and is caused by inflammation or demyelination in the central nervous system, which could be a precursor to MS or another condition.

• Do Not Miss Diagnoses

  • Central Nervous System (CNS) Infections: Such as viral encephalitis or abscesses, which can present with similar symptoms and require urgent treatment.
  • CNS Vasculitis: Conditions like primary CNS vasculitis can mimic demyelinating diseases and require prompt diagnosis and treatment to prevent serious complications.
  • Leukodystrophies: Although rare, these genetic disorders affecting the growth or maintenance of the myelin sheath can present with progressive neurological decline.

• Rare Diagnoses

  • Balo’s Concentric Sclerosis: A rare form of MS characterized by concentric rings of demyelination on MRI.
  • Marburg Variant of MS: A rare, aggressive form of MS with rapid progression and severe symptoms.
  • Acute Hemorrhagic Leukoencephalitis (AHLE): A rare, often fatal condition characterized by hemorrhagic necrosis of the brain and is considered a variant of ADEM.

Each of these diagnoses has distinct clinical, radiological, and sometimes serological features that can guide the differential diagnosis. A thorough evaluation, including a detailed history, neurological examination, MRI, and appropriate laboratory tests (including antibody panels), is essential for accurate diagnosis and management.