Multiple Sclerosis (MS) is a chronic condition where the immune system attacks the protective covering of nerve fibers in the central nervous system (brain and spinal cord). This damage disrupts nerve signal flow, leading to a wide variety of symptoms that are often unpredictable. MS symptoms frequently change in severity and presence over a 24-hour period. This daily variability is a common experience and reflects the temporary sensitivity of already-damaged nerve pathways, not necessarily a worsening of the disease itself.
Understanding Daily Symptom Changes
The phenomenon of MS symptoms changing within a single day is known as diurnal variation. This daily fluctuation occurs because the efficiency of nerve signal transmission changes depending on the body’s internal state. Symptoms like fatigue, muscle stiffness, or cognitive issues may be mild upon waking but become more pronounced later in the day.
This temporary worsening of existing symptoms is often termed a pseudo-exacerbation. Pseudo-exacerbations involve a temporary slowing of nerve signals through areas that have already lost their myelin protection. Since this is a functional rather than structural change, it is not caused by new inflammation or demyelination. Symptoms often peak in the late afternoon or evening as the body has accumulated activity and energy reserves are depleted.
Common Factors That Worsen Symptoms
Daily symptom fluctuations are typically triggered by specific internal and external factors that place temporary stress on the nervous system. A common external factor is an increase in body temperature, which can happen due to hot weather, a warm bath, or intense exercise. Even a slight rise in core body temperature can impair the ability of demyelinated nerves to conduct electrical signals, leading to a temporary worsening of symptoms like vision blurriness or weakness.
Physical exertion and general fatigue are powerful internal triggers, often causing symptoms to worsen as the day progresses and energy stores are used up. Emotional stress, whether chronic or acute, can likewise contribute to an increase in symptom severity. The body’s inflammatory response to an existing infection, such as a cold, flu, or urinary tract infection, is another major factor. Infections trigger an immune response that temporarily stresses the nervous system, leading to a pseudo-exacerbation until the underlying illness is resolved.
Fluctuations Versus Relapses
It is important to distinguish a temporary daily fluctuation (pseudo-exacerbation) from a true MS relapse (exacerbation), as they have different causes and require different management approaches. A daily fluctuation is a short-lived event, usually resolving within 24 hours once the trigger, such such as heat or fatigue, is removed. The worsening of symptoms in a pseudo-exacerbation is not caused by new damage to the nervous system but rather by a temporary impairment of already-damaged pathways.
In contrast, a true MS relapse involves the appearance of new neurological symptoms or the significant worsening of old ones that lasts for a minimum of 24 to 48 hours. A relapse is caused by a new area of inflammation and demyelination, resulting in new damage to the central nervous system. This type of event occurs in the absence of fever or infection, and the symptoms typically take days or weeks to slowly resolve, often requiring medical intervention. Understanding this duration difference is key for individuals to know when a change in symptoms requires contacting their healthcare team.