MS types^2,4,5,6

Clinically isolated syndrome (CIS) is a first neurological episode with a single or multiple symptoms lasting at least 24 hours. Not everyone who experiences a CIS will develop MS.

Relapsing remitting MS (RRMS or relapsing MS) is the most common type of MS, accounting for up to 85% of cases, with symptoms flaring and subsiding/disappearing. Symptoms may be new or may be exacerbated in an attack, while a relapse can last days or months; the disease can become inactive for months or years. Attacks and relapses are unpredictable but a typical patient with RRMS may see one or two attacks every year, albeit with less recovery each time.

Rapidly evolving severe relapsing remitting MS (RESMS) is less common and describes RRMS with two or more disabling relapses over 12 months, and two consecutive MRI scans showing an increase in lesions.

Secondary-progressive MS (SPMS) describes the secondary phase of MS after RRMS has progressed after years or decades, and disability worsens with no definite remission periods. Most people with RRMS will transition to SPMS.

Primary progressive MS (PPMS) accounts for 10-15% of MS diagnoses. Symptoms gradually worsen from the outset with no remission, but generally without sudden attacks.

Progressive-relapsing MS (PRMS), an old term, occurs in around 5% of MS cases. There is a progressive neurological decline with increasing disability, with periods of symptom intensification and reduction.

Benign MS, another old term, is sometimes used for a version of RRMS with very mild attacks and long symptom-free periods. It occurs in 5%-20% of diagnoses.

MS can be further categorised as active (where successive MRI scans show an increase in lesions) or not active, worsening and not worsening.