MS is an inflammatory condition that affects the oligodendrocites of the CNS. Peripheral nerves are not affected.
Epidemiology & Aetiology
- More common the further away from the equator you are
- Some genetic factors involved
- Twice as common in women
- Mean age of onset 20-45
An autoimmune reaction against myelin and oligodendrocites (CNS equivalent of Schwann cells). There is destruction of myelin, and axonal loss. Antibodies to Myelin basic protein seen early on in the disease. Normally, macrophages cannot easily cross BBB, but in MS, they exhibit glycoprotein α4 β1, allowing them to adhere to and cross the endothelium.
Active lesions (plaques) are sites of inflammation, and show up on MRI as white blobs, roughly 2-10mm in size, and can occur anywhere in the CNS, although most commonly occur at the optic nerves, periventricular lesion, brainstem and cerebellar connections.
Conduction loss is probably to blame for most of the symptoms of MS.
Patterns of Disease progression
Progression is extremely variable. Some patients may only ever have one episode (benign MS), whilst other may rapidly get worse with no periods of remission.
Almost any neurological sign can be present in MS, but some are more common than others. Common examples are below. Usually for motor function, the signs are UMN signs, but there may also be LMN signs.