Multiple sclerosis (MS), originally described in the 1800s, is a chronic neurological disease affecting the central nervous system. The central nervous system includes the brain and spinal cord. Multiple Sclerosis is an autoimmune disease, which means that our immune system is activated to react against our own nervous system. In multiple sclerosis, the main target of this immune attack is the myelin covering over an axon. The axons are part of a neuron (nerve cell) and are used to transmit information to other nerve cells. Efficient transmission is maintained with the presence of myelin, analogous to rubber insulation over an electrical wire. Neurological signs typical for multiple sclerosis occur when there has been myelin breakdown.
There are typical patterns for the disease course and patients can be categorized within one of these groups:
Relapse: A new neurological deficit which lasts for more than 24 hours. Attack or exacerbation are other names for a relapse.
Pseudorelapse (Pseudoexacerbation): Occasionally, pre-existing symptoms may worsen, mimicking a relapse. This is usually associated with the onset of a fever, infection, or extreme fatigue. The treatment for a pseudorelapse is treatment of the underlying infection.
Secondary Progressive MS: Is a form of MS that generally occurs in relapsing-remitting patients 10-15 years into the course of disease. In this form of MS, neurological deficits do not remit, but persist and cause chronic symptoms.
Primary Progressive MS: Approximately 10% of patients experience primary progressive MS, in which progression occurs from the onset of disease. Primary progressive MS often begins after age 40 years, which differs from the typical age of onset of RRMS (20s-30s). An increased proportion of men experience primary progressive MS compared to other forms of MS.
Progressive relapsing MS: A minority of patients experience a course of disease in which relapses and progression are superimposed from the onset of disease.
Neuromyelitis Optica (NMO): A rare autoimmune disorder that affects the optic nerves and spinal cord almost exclusively. An antibody marker in the serum is present in approximately 75% of patients. Click here to learn more about NMO.