Demyelination
Demyelination is incorrectly often equated to multiple sclerosis, whereas in reality it is a generic pathological term simply describing, as the word suggests, the loss of normal myelin around axons in the central nervous system. This should be distinguished from dysmyelination where the formation of normal myelin is absent.
Primary
Primary demyelinating disorders include:
- clinically isolated syndrome (CIS)
- first symptomatic episode which may or may not progress to MS
- multiple sclerosis (aka clinically definite multiple sclerosis (CDMS))
- can only be diagnosed if McDonald diagnostic Criteria for MS (or other similar criteria) are met.
- variants include
- tumefactive multiple sclerosis
- acute malignant Marburg type
- Devic disease (aka Devic opticomyelitis)
- Schilder type (diffuse cerebral sclerosis)
- Balo concentric sclerosis (BCS)
- acute disseminated encephalomyelitis (ADEM)
- monophasic usually post viral acute demyelination
- often considered a secondary form of demyelination
- transverse myelitis
- chronic inflammatory demyelinating polyneuropathy (CIDP)
- Guillain-Barre Syndrome
Infective
- progressive multifocal leukoencephalopathy (PML)
- HIV encephalitis / HIV dementia complex / HIV associated myelopathy
- progressive rubella panencephalitis
In most cases toxic and metabolic disease which affect the white matter are considered separately but for the sake of completeness they are listed below.
Toxic
- central pontine myelinolysis (CPM)
- posterior reversible encephalopathy syndrome (PRES) : related to hypertension predominantly
- chemotherapy
Metabolic / genetic
- leukodystrophies
- sometimes classified as leukodystrohpies 2
Ischaemia
Although not referred to as demyelination many processes which cause iscahemia lead to demyelination:
- deep white matter ischaemia
- radiotherapy changes
