Relapses of Multiple Sclerosis

Relapses are also often referred to as ‘acute attacks’. Medical professionals define a relapse as the occurrence of new or recurrence of old symptoms that last more than 24 hours in the absence of a change in body temperature or infection. Relapses usually begin gradually over hours or days. They can last for any length of time but average 4 to 6 weeks. Relapses can vary from mild to severe. At their worst, acute relapses may need hospital treatment.

Temporary worsening of symptoms may occur with increased body temperature, such as after a hot bath or on a hot day and these episodes are not considered to be true relapses but rather reflect poor conduction of nerve fibres with damaged myelin with increased heat. Infection might also be a cause of such ‘pseudo-relapses’.

The relapse rate on average is one relapse every other year; however, research has shown that relapses have only a marginal effect on the accumulation of irreversible neurological disability because MS can progress without relapses.

Most people will recover from relapses within several weeks to a few months.

In the relapsing-remitting pattern, relapses alternate with remissions, in which symptoms generally improve to reach a stable functional situation. Remissions may last months or years. Relapses can occur spontaneously or can be triggered by a range of factors, for example by an infection.

Attacks and partial recoveries may continue to occur. According to some natural history studies, of those people who start with relapsing-remitting disease, more than 50% will develop Secondary Progressive MS within 10 years and 90% within 25 years.

The Primary progressive form of the disease progresses gradually from onset, with no remissions, although there may be temporary plateaus in symptoms during which the disease does not progress.

About 10% of people with multiple sclerosis have only one or a few episodes or only mild episodes, after which the disease progresses little, if at all (‘Benign’ MS). Very rarely, multiple sclerosis progresses quickly resulting in severe disability or death soon after the symptoms develop.

However, most people with multiple sclerosis have periods of relatively good health (remissions), alternating with debilitating relapses. Later, their condition may worsen slowly.

Amended April 2008