Types of Multiple Sclerosis
Multiple sclerosis (MS) is a progressive neurological disorder characterized by demyelination, which is the loss of the insulating cover around nerve fibers called the myelin sheath. This loss leads to delayed or missing nerve signals.
MS is classified into four main types, based on the phase and severity of disease progression: clinically isolated syndrome; relapsing-remitting MS; secondary progressive MS, and primary progressive MS.
Below you will find more information on each of these types.
Clinically Isolated Syndrome
In clinically isolated syndrome (CIS), a patient first experiences MS-like symptoms resulting from nerve inflammation and demyelination lasting more than 24 hours, such as vision problems, difficulty walking, or numbness. Patients may never have another episode of symptoms, or they could progress to MS at a later date. Patients are considered to have CIS until a physician finds more evidence to confirm an MS diagnosis.
Primary Progressive MS
In primary progressive MS, the disease starts in the attack phase, and symptoms steadily worsen over time without relapses or remissions. The progression of symptoms in this form varies between patients. The disease is considered active when a patient experiences occasional relapses or there is evidence of new lesions on an MRI. Periods of remission may occur later in the disease.
Relapsing-remitting MS is characterized by periods of neurodegeneration where new symptoms occur or old symptoms worsen (relapsing), and periods of rest where some or all normal function is restored (remitting). While patients may recover during the remission periods, the disease generally progresses over time, and some symptoms are likely to persist even during remission periods.
Secondary Progressive MS
RRMS often continues to worsen and eventually may transition to secondary progressive MS, at which time the disease moves from relapse and remission phases into a steady progression of symptoms. It is not well-understood what factors influence the progression from RRMS to SPMS, and progression is difficult to predict. Active and inactive forms can both occur with or without progression.