Diseases That Cause Demyelination
Multiple sclerosis (MS) is the most common inflammatory demyelinating disease of the central nervous system, but numerous other conditions cause demyelination including neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), acute disseminated encephalomyelitis (ADEM), progressive multifocal leukoencephalopathy (PML), and various genetic leukodystrophies.
Primary Demyelinating Diseases
Autoimmune/Inflammatory Demyelinating Disorders
Multiple Sclerosis (MS) is the prototypic inflammatory demyelinating CNS disease affecting approximately one million adults and represents the leading cause of nontraumatic neurological disability in young adults 1. The diagnosis requires dissemination of lesions in time and space, with typical periventricular, juxtacortical, infratentorial, and spinal cord involvement 2, 3.
Neuromyelitis Optica Spectrum Disorder (NMOSD) predominantly targets the spinal cord, optic nerves, and brainstem 4. In 60-80% of cases, optic neuritis and/or longitudinally extensive transverse myelitis (LETM) result in blindness and paralysis 4. This condition is associated with aquaporin-4 (AQP4) antibodies detectable in peripheral blood 4.
Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD) is a distinct entity associated with antibodies against MOG, a glycoprotein on the outer membrane of myelin 4. About 42% of NMOSD patients who test seronegative for AQP4 antibody test positive for MOG antibodies 4. MOGAD shows predilection for relapses of optic neuritis and transverse myelitis, with ADEM being a well-recognized phenotype in children 4.
Acute Disseminated Encephalomyelitis (ADEM) is a monophasic demyelinating disease that presents particular diagnostic difficulties 3. A diagnosis should not be made unless new symptoms and signs or imaging abnormalities appear more than three months after clinical onset 3.
MS Variants
- Marburg variant of acute MS represents a fulminant form of demyelination 1
- Balo's concentric sclerosis shows characteristic concentric patterns of demyelination 1
- Tumefactive MS presents with large, tumor-like demyelinating lesions 1
Infectious Causes of Demyelination
Viral Demyelination
Progressive Multifocal Leukoencephalopathy (PML) is caused by JC papovirus destruction of oligodendrocytes and represents the most prominent viral demyelinating disease in humans 5.
Subacute Sclerosing Panencephalitis is an invariably fatal childhood disease caused by persistent measles virus 5.
COVID-19-related demyelination has been reported, though the rate of CNS demyelinating events occurring with SARS-CoV-2 infection is relatively low 6. The median duration between COVID-19 infection and demyelinating event onset varies: 11.5 days for NMOSD, 6 days for MOGAD, and 13.5 days for MS 6.
Other viral causes include HTLV-1 infection, which can present striking similarities to MS 3. Virus-induced demyelination can occur through direct cytolysis with or without immune response participation 5, 7.
Vascular and Autoimmune Mimics
Several conditions can mimic MS through demyelination or white matter changes 3:
- Phospholipid antibody syndrome causes multifocal cerebral ischemia or infarction in young adults 3
- Systemic lupus erythematosus can produce demyelinating lesions 3
- Behçet disease may cause inflammatory demyelination 4
- CADASIL is an autosomal dominant disorder with specific genetic markers causing extensive white matter lesions 4
- Susac syndrome can mimic MS 4
- CLIPPERS (chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids) is a rare inflammatory condition 4
Genetic Disorders
Leukodystrophies are genetic disorders of myelin that should be considered, particularly among children and teenagers 3. The ready availability of genetic testing, including whole exome sequencing, has expanded the phenotypic spectrum of leukodystrophies, and some cases of atypical MS are being revised to leukodystrophy diagnoses 4.
Key Diagnostic Considerations
Critical Differentiating Features
When evaluating demyelinating diseases, consider:
- Age at presentation: MS criteria best apply to individuals between 10 and 59 years of age 3
- Atypical presentations (dementia, epilepsy, aphasia) require additional CSF and VEP analysis 3
- Serological testing: AQP4 antibodies for NMOSD and MOG antibodies for MOGAD are essential diagnostic tools 4
- Imaging patterns: ≥3 periventricular lesions help distinguish MS from other conditions 2
- CSF analysis: Oligoclonal bands and kappa free light chains support MS diagnosis 4
Common Pitfalls
Lyme disease can present striking similarities to MS and must be excluded 3. Monophasic demyelinating diseases require careful follow-up, as diagnosis should not be made unless new symptoms appear more than three months after clinical onset 3. Incidental periventricular lesions can be detected in healthy individuals and up to 30% of patients with migraine 2.