Is it an MS relapse or a pseudo-relapse?

What is an MS relapse?

In relapsing multiple sclerosis, the immune system attacks the protective coating around nerve fibres in the brain, spinal cord or optic nerves. A new area of inflammation can disrupt signals and cause symptoms such as blurred vision in one eye, numbness or tingling, weakness in a limb, loss of balance, double vision or bladder urgency.

A relapse is usually defined as new symptoms, or a clear worsening of existing ones, that last for more than 24 hours after a stable period of at least a month, when there is no infection or other cause 1. Symptoms typically build over days, stay for a period and then improve over weeks to months, although recovery is not always complete.

What is a pseudo-relapse?

A pseudo-relapse is a temporary worsening of symptoms from previous damage, triggered by something that makes damaged nerve fibres conduct signals less well. Common triggers are a raised body temperature from fever, hot weather, a hot bath or exercise, and infections, particularly urinary tract infections, as well as stress, poor sleep and exhaustion.

Heat affects demyelinated nerves in a specific way: as temperature rises, signals through damaged fibres slow or block, so old symptoms reappear. This is often called Uhthoff's phenomenon, and symptoms settle as the body cools 2. No new inflammation is involved, and the episode does not cause new damage.

How can you tell the difference?

Clues that point to a pseudo-relapse include symptoms that are the same as previous ones, that appear with heat, fever or an infection, and that improve within hours to a day once the trigger is removed. Clues that point to a true relapse include symptoms that are new, that last beyond 24 hours without an obvious trigger, and that keep progressing over several days 1.

The distinction is not always clear from symptoms alone. Checking temperature, testing urine for infection and looking for other infections are standard first steps. An MS team may arrange an examination and sometimes an MRI scan to look for new areas of inflammation.

How is a true relapse treated?

Not every relapse needs medicine. Mild relapses that do not affect daily function may be managed with rest, symptom control and support. For relapses that affect function, a short course of high-dose steroids can speed recovery, although it does not change the long-term outcome. UK guidance recommends excluding infection before starting steroids and discussing risks and benefits 1.

A relapse is also a reason to review disease-modifying treatment, because frequent relapses may indicate that current treatment is not controlling the disease well enough. Rehabilitation during and after a relapse helps recover strength, balance and daily skills.

How is a pseudo-relapse managed?

The trigger is treated: infections are treated with appropriate antibiotics, fever is reduced, and overheating is avoided with cooling measures such as fans, cool drinks, cooling vests and cooler water. Rest and good sleep help symptoms settle.

Steroids are not used for pseudo-relapses, because there is no new inflammation and steroids carry side effects. Recognising the pattern of one's own pseudo-relapses reduces anxiety and helps avoid unnecessary treatment.

How does rehabilitation help after a relapse?

Once the acute phase settles, physiotherapy and occupational therapy help rebuild strength, walking, balance and hand function, and address fatigue. Short-term goals, such as returning to work tasks or walking a certain distance, give structure to recovery.

Rehabilitation also looks for residual symptoms that need specific treatment, such as spasticity, bladder problems or pain. People who have had several relapses may benefit from a planned programme that includes exercise, energy management and adaptations at home or work.

When should you contact your MS team?

Contact your MS team if you notice new symptoms lasting more than 24 hours, if existing symptoms become significantly worse without a clear trigger, or if symptoms affect your ability to walk, see or manage daily tasks. Also get help promptly if you have signs of an infection, as treating it quickly can shorten a pseudo-relapse.

Seek urgent care for sudden severe symptoms such as rapid loss of vision, severe weakness, difficulty breathing or swallowing, or if you are unwell with a high fever.

Frequently asked questions