Subtypes of Multiple Sclerosis
Four main subtypes of clinical course of multiple sclerosis (MS) have been described.
The first type, relapsing-remitting MS
, is characterized by unpredictable relapses of neurological deficits. The attacks develop within periods of days to weeks and can be followed by full or partial resolve of deficits, or absence of remission. Remission after attacks usually develops in a few weeks or months after the peak of the disease, although sometimes recovery can take two years and more. Patients with such course of the disease do not report neurological deficit progression between the attacks. In most patients, this describes the initial course of MS.
In the second subtype, secondary progressive MS
, the disease initially presents the picture of relapsing-remitting MS but progresses with the course of time. Period of progression can develop either just after the onset of the disease or in several years or decades. Secondary progressive subtype differs from relapsing-remitting MS by gradual progression of the deficits between the attacks or by the gradual progression of the deficits after the attacks become indistinguishable.
The third subtype, primary progressive MS
, is characterized by the gradual progression of disability from onset. Some individuals can present periods of clear stability but do not suffer severe attacks.
The primary progressive MS develops in about 15% of multiple sclerosis cases and is the most frequent form of late onset MS (after the age of 40). Sometimes, patients with clear primary progressive MS also suffer superimposed attacks. This non-standard clinical picture is referred to as progressive relapsing MS