Uhthoff Phenomenon

By | June 10, 2022

The Uhthoff phenomenon is a transient worsening of neurological symptoms in demyelinating diseases caused by temperature increase. The phenomenon was first observed in multiple sclerosis. However, the Uhthoff phenomenon must be diagnostically distinguished from a real flare-up of MS.

What is the Uhthoff phenomenon?

In 1890, the ophthalmologist Wilhelm Uhthoff (1853-1927) first described a strange phenomenon in patients with multiple sclerosis. This was a temporary weakening of vision during physical exertion. He realized that the symptom was related to an increase in body temperature. For what does the abbreviation kidd syndrome stand for, please visit usvsukenglish.com.

The deterioration of visual acuity due to an increase in temperature is considered to be the Uhthoff phenomenon in the narrower sense. In a broader sense, the worsening of other neurological symptoms in all demyelinating diseases due to an increase in body temperature is also referred to as the Uhthoff phenomenon.

Symptoms are similar to those of a real flare-up. However, this is a so-called pseudo thrust because no demyelination processes take place. The conductivity in the affected nerve fibers is only reduced by the heat effect.


The cause of the Uhthoff phenomenon lies in the deterioration of electrical conductivity in the damaged nerves as a result of body heating in the context of demyelinating diseases. Normally, nerve fibers are electrically isolated from each other by a layer of myelin sheaths. In multiple sclerosis and other demyelinating diseases, however, the myelin sheath is attacked by inflammatory processes.

This leads to their destruction. External influences can reduce the conductivity in the exposed nerve fibers. This reduces, among other things, when the body heats up. The body temperature can increase due to physical exertion, fever or external heat influences. The risk of the Uhthoff phenomenon is increased in hot summer temperatures or when visiting the sauna.

When the temperature drops, the neurological deficits usually disappear. In individual cases, however, the destruction of the myelin sheath is so serious that the symptoms are no longer reversible after a temperature increase or physical exertion. The symptoms of the Uhthoff phenomenon cannot be distinguished externally from those of a real flare-up.

With a real attack, however, autoimmune processes always destroy myelin sheaths at certain points in the nervous system, while in the Uhthoff phenomenon, as mentioned, an increase in body temperature at the damaged points only reduces the conductivity of the nerve fibers. Because temperature fluctuations can never be ruled out, the Uhthoff phenomenon occurs in around 85 percent of all patients with MS.

Symptoms, Ailments & Signs

The Uhthoff phenomenon is shown by various temporary deficits in the context of multiple sclerosis or another demyelinating disease. It was originally described by the ophthalmologist Wilhelm Uhthoff as a weakening of the eyesight during physical exertion.

However, other neurological deficits can also occur. These depend on which sections of the nervous system are damaged. The Uhthoff phenomenon manifests itself in the same way as a real thrust. In addition to visual disturbances and eye pain, abnormal sensations (paraesthesia), pain and numbness in the hands or legs can also occur.

Facial pain can also occur if the trigeminal nerve is affected. Muscle cramps and signs of paralysis are also observed. Depending on the affected area, there are also double vision, dizzy spells, speech disorders or swallowing disorders.

Intestinal, bladder and sexual functions can be disturbed. Overall, the Uhthoff phenomenon is also characterized by increasing tiredness (fatigue) and exhaustion during physical exertion. Cognitive disorders and psychological abnormalities are also possible. As a rule, the symptoms of this phenomenon subside quickly when the body temperature drops.

Diagnosis & course of disease

Since the Uhthoff phenomenon occurs as a manifestation of MS or other demyelinating diseases, these diseases must be diagnosed as a matter of priority. Within the underlying disease, however, a differential diagnosis is necessary to distinguish it from real flare-ups in order to be able to take the right treatment measures.

It is therefore important to clarify the question of what causes the symptoms to occur. If the symptoms appear after physical exertion, after fever, after visiting the sauna, hot baths or very high summer temperatures, it can usually be assumed that it is a Uhthoff phenomenon. In the last century, a so-called hot bath test was even carried out to diagnose the Uhthoff phenomenon.

However, since in rare individual cases there was no regression of the symptoms, this test may no longer be used. When the symptoms are observed for the first time under the conditions of body temperature increase, the underlying disease must be determined by imaging methods such as MRI examinations of the brain and spinal cord, blood tests, CSF tests and neurophysiological examinations.


The symptoms of the Uhthoff phenomenon can be very different, so that the diagnosis and treatment of this disease is often delayed. Those affected suffer from severe eye pain and also from visual disturbances. If the Uhthoff phenomenon is not treated, these visual problems can also occur permanently.

Furthermore, various abnormal sensations or even paralysis occur, which have a negative effect on the patient’s quality of life. In many cases, those affected also suffer from pain in the legs or from disturbances in temperature perception. As a result, possible dangers can no longer be correctly assessed.

The Uhthoff phenomenon can also lead to disturbed sexual function or bladder problems. The patients themselves often feel tired and exhausted and are no longer able to carry out strenuous activities. In some cases, patients with this disease also suffer from mental disorders and depression and therefore also need psychological treatment.

Treatment of the Uhthoff phenomenon is carried out with the help of drugs. Complete healing cannot always be guaranteed. In most cases, those affected are always dependent on outside help. It cannot generally be predicted whether the Uhthoff phenomenon will lead to a reduced life expectancy.

When should you go to the doctor?

In the case of the Uhthoff phenomenon, treatment by a doctor must always be carried out. The earlier the disease is detected, the better the further course is, as a rule. The affected person should therefore consult a doctor as soon as the first symptoms and signs of the disease appear, so that further complications can be avoided. A doctor should be contacted if the person concerned suffers from severe pain in the eyes.

Abnormal sensations or numbness can also indicate the disease and should also be checked by a doctor. In many cases, the pain can also spread over the entire face. Muscle cramps or a disturbed sexual function can also indicate the Uhthoff phenomenon. It is not uncommon for those affected to suffer from swallowing difficulties or even speech disorders.

If these symptoms occur, the person concerned should consult a general practitioner. Further treatment depends heavily on the exact severity of the symptoms. No general prediction can be made about the further course of the disease.

Treatment & Therapy

The therapy mainly treats the underlying disease. Many neurological diseases such as multiple sclerosis cannot currently be treated causally. Only symptomatic treatment is possible. In the case of real flare-ups within MS, high-dose glucocorticoids are used to dampen the inflammatory processes.

Since these are immunosuppressants, side effects are also to be expected with this therapy. Pseudo flares in the form of a Uhthoff phenomenon do not require such drastic measures. Decisive here is the lowering of the body temperature. This can be achieved by wearing cooling hoods, cooling vests or cooling socks. Then the symptoms almost always go away on their own.


Preventative measures against the Uhthoff phenomenon are only ever possible within the context of the underlying diseases, because it never occurs in isolation. If a severe demyelinating disease such as multiple sclerosis has been diagnosed, anything that would cause an increase in body temperature should be avoided. These include physical exertion, hot baths, visits to the sauna and the influence of hot summer temperatures.


The Uhthoff phenomenon often occurs in the clinical picture of multiple sclerosis. Those affected can take preventive action to counteract this phenomenon. All external influences that increase the patient’s body temperature should be avoided as far as possible as a precaution. This includes great physical exertion as well as visits to the sauna or hot baths.

Wearing cooling vests and cooling hoods also has a preventive effect. These measures in particular are also used when the Uhthoff phenomenon has already occurred. Protection is the top priority: activities that require good eyesight, such as driving a car or working on machines, should be restricted as far as possible.

The Uhthoff phenomenon often causes severe motor impairments, comparable to a flare-up in multiple sclerosis. Those affected often need special help in everyday life and the support of family and friends. The eyes are often particularly affected by the Uthoff phenomenon. Strong light sources such as direct sunlight or bright screens should be avoided.

Sleep masks can help to protect and relieve sore eyes. Medical advice should be followed and prescribed medication should be taken so that the “pseudo thrust” in the form of the Uhthoff phenomenon can completely recede.

You can do that yourself

The Uhthoff phenomenon should be treated preventively. Patients suffering from multiple sclerosis should avoid strenuous physical activity and intense changes in body temperature, such as from saunas or hot baths. Wearing cooling vests and cooling hoods supports prevention. These measures promise to alleviate the symptoms even if the Uhthoff phenomenon has already occurred.

At the same time, the patients have to take care of themselves. Driving, working on machines and other activities that require good eyesight should be avoided. When the Uhthoff phenomenon occurs, patients require assistance with everyday tasks. That is why a support network of friends and family is important.

An adapted diet also supports the recovery of the eyes. The most important measure, however, is to protect your eyes. Since the eyes are already under a lot of strain during a flare-up and vision is reduced as a result, further exertion should be avoided. MS patients diagnosed with Uhthoff phenomenon should wear a sleep mask and avoid direct sunlight and bright screens. It is also important to comply with the medical requirements. In most cases, special medication must be taken so that the thrust can completely recede.

Uhthoff Phenomenon