Both Uhthoff syndrome and fatigue syndrome can occur as part of multiple sclerosis. This article explains what is behind it and what the side effects differ.

The Uhthoff phenomenon

According to studies, around 80% of MS patients are affected by Uhthoff's phenomenon. Symptomatically, the Uhthoff phenomenon manifests itself in transient, short-term neurological symptoms such as vision problems, impaired motor function or loss of strength. In the Uhthoff phenomenon, these symptoms are associated with an increase in body temperature (e.g. due to hot outdoor temperatures, hot bath/shower, sauna, exercise).

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Multiple sclerosis results in nerve damage caused by the body's own cells (demyelination). This creates scarred areas on the nerves. In the Uhthoff phenomenon, the nerve conduction velocity is presumably reduced precisely in these areas due to heat or elevated temperature, which leads to a reversible worsening of neurological symptoms. In this case, this is also referred to as a pseudo-rush, as the symptoms are triggered by physical influences and not by inflammatory activities in the body.
Studies on peripheral nerves have shown that even an increase in body temperature of 0.5 °C can slow or block the transmission of stimuli in demyelinated nerve fibers. As demyelination progresses, the sensitivity of nerve fibers to changes in temperature increases.

The Uhthoff phenomenon also occurs in other diseases that involve nerve demyelination. Diseases include Guillain-Barré syndrome, acute disseminated encephalomyelitis (ADEM) or chronic inflammatory demyelinating polyneuropathy.

The fatigue syndrome

Fatigue syndrome describes a persistent state of exhaustion that does not subside even through periods of rest and sleep. Typical symptoms include persistent tiredness, reduced physical performance, difficulty concentrating and an unsatisfactory need for sleep.

According to studies, up to 90% of MS patients suffer from fatigue. Due to unspecific symptoms and lack of biomarkers, diagnosis is difficult and requires ruling out other conditions such as diabetes, hypothyroidism, and anemia. So far, it is unclear why fatigue syndrome occurs. This is referred to as a “multifactorial (i.e. influenced by many factors) process.” Fatigue may be affected by nerve cell damage, but also by other influencing factors such as the psyche, diet and the use of medications.

Fatigue syndrome also does not only occur in MS patients. Fatigue can also occur in patients who suffer from other chronic illnesses. For example, up to 90% of cancer patients who are undergoing chemotherapy or radiotherapy are affected. Fatigue can also occur in rheumatological diseases, long Covid, diabetes.

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Uhthoff phenomenon vs. fatigue syndrome

The Uhthoff phenomenon is manifested by temporary, short-term neurological symptoms such as vision problems, impaired motor function or loss of strength caused by an increase in body temperature.

In general, it is important to avoid hot showers and sauna sessions, intense heat and direct sunlight, as these directly influence the body temperature. Airy summer clothing or even cooling clothing such as cooling vests are very useful. Since high fluid loss can make symptoms even worse, it is important to drink plenty and enough. Ice cubes, ice and chilled drinks in particular can cool the body from the inside.
Arms and feet can also be held in a bowl of cool water to cool down quickly. In midsummer, cold washcloths can be placed on the body, especially at night, so that the body is slightly cooled.
Anyone suffering from the Uhthoff phenomenon should therefore prepare well, especially in summer. Because preparation is half the battle; if it is foreseeable that the next few days will be very hot, then prepare yourself accordingly. Put ice cubes cold, have enough cold drinks in the fridge or get your garden shower out of the garage.

Fatigue syndrome is less specific and has a wider range of symptoms. Common symptoms include a general feeling of exhaustion and weakness, difficulty concentrating, disturbed sleep, loss of motivation and loss of physical resilience. According to the current state of science, fatigue is also not directly related to external influences, but is influenced by behavior such as physical activity, sleep, stress and more.

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In our YouTube video, we also explain the exact differences between these two syndromes. Have a look.