Relapses and pseudo-episodes of demyelinating diseases
Recently, many places in the world, including China, have been experiencing extreme heat, and some “healthy people” have passed away due to heat. It is not difficult to imagine that the high temperature, which is unbearable for healthy people, can be devastating for patients with certain diseases. For example, in patients with demyelinating diseases of the central nervous system, it is extremely common for clinical symptoms to fluctuate during the summer season, often triggering anxiety in patients who fear a relapse of the disease and ask if they need treatment.
1. What is a relapse (seizure)?
Neuroimmunologists believe that autoimmune reactions destroy myelin sheaths and fibers in the central nervous system, resulting in damage to myelin sheaths wrapped around nerve fibers, followed by interruption of bioelectrical signals conducted by myelin sheaths, resulting in different clinical manifestations, medically known as relapses or acute attacks. In multiple sclerosis and optic neuromyelitis optica, 85% of patients begin with a relapsing-remitting clinical pattern. In other words, patients feel worse during one period of time and tend to have less severe symptoms during another.
It was found that in 20% of relapses, new lesions appeared in the brain and new symptoms appeared clinically. In 80% of relapses, the old lesions are aggravated, the original manifestations are aggravated, the duration of symptoms exceeds 48 hours, and the patient needs to exclude fever, infection, excessive fatigue, and endocrine hormonal imbalance (menstrual period), among others. As can be seen, the diagnosis of relapse requires 3 conditions.
(1) The appearance of new symptoms or aggravation of old ones.
(2) Duration of symptoms not shorter than 48 hours (also 24 hours).
(3) Exclusion of other factors.
The specific symptoms of a relapse depend on the location of the lesion in the nervous system; for example, if the lesion is in the optic nerve, the patient will have vision problems. For example, if the lesion is in the spinal cord, the patient may have problems with urination and defecation, or weakness in limb movement and increased numbness and pain.
A relapse goes through roughly 3 stages.
(1) New symptoms appear or old symptoms worsen.
(2) Stable condition with no further changes.
(3) As the lesion is repaired, the symptoms are reduced or disappear. The whole process takes about 8 weeks on average, and as soon as the symptoms improve, it indicates that the remission period has been entered. If the symptoms worsen again within the same month, it should be considered as the same attack and not counted as another relapse. The timing, intensity, duration, and recovery time of each relapse can be completely different. Because individuals are different, with each relapse, it is impossible for the patient and physician to predict the duration and degree of the attack, as well as the accompanying symptoms.
It should be noted that even in remission, some symptoms persist. The length of time from symptom improvement to remission is variable. It can be as short as a few weeks or as long as several months or even years. Recovery of symptoms depends on the size of the lesion and the extent of the lesion, and can be complete or partial. Generally speaking, symptoms may remain permanently for more than 18 weeks. This is the main reason why there are patients who are not part of the primary progressive type and believe that they have not experienced remission from the onset of the disease.
During remission, the damaged myelin sheath can be completely or partially repaired. However, even if the symptoms disappear completely, there is a “scar” in the nerve tissue that can be seen with the help of an MRI. If the myelin sheath is not completely repaired, or if the nerve fibers are completely destroyed, the recovery is definitely incomplete.
2.Triggering factors for relapse
Stressful stresses such as marital changes and the death of a loved one can produce transient worsening of symptoms, while influenza can trigger a true relapse. In multiple sclerosis, pregnancy can reduce maternal immune function and put the disease into remission. Postpartum immune function is enhanced and the chances of relapse are increased. Because of the different mechanisms of optic neuromyelitis optica, both postpartum and pregnancy may increase the chance of relapse.
3. Pseudo-relapse (Uhthoffu phenomenon)
When the patient is in an environment such as summer, fever, hot bath, strenuous activity or infection, premenstrual period, menstrual period, etc., along with an increase in body temperature, the patient feels an increase in symptoms for a short period of time, and once the external conditions improve (such as environmental changes), the symptoms may disappear completely. This clinical manifestation, which appears to be a relapse but is not a real relapse, is known as the Uhthoffu phenomenon, also known as “pseudo-episodes”. For example, when taking a hot shower, the numbness of the patient’s body becomes worse, and after returning to a normal environment or resting, the symptoms return to their previous level. When taking a bath, the vision is blurred, but after resting, the vision returns to normal. It has been suggested that an increase of 0.5 degrees Celsius in the patient’s basal body temperature is enough to cause the Uhthoffu phenomenon.
4. How to understand pseudo-relapse?
In healthy individuals, when the temperature of the external environment rises, the thermoregulatory center in the brain controls body temperature at a relatively constant level through peripheral neurological activity, dilating blood vessels, and sweating to dissipate heat. In patients with multiple sclerosis and optic neuromyelitis optica, because of impaired neurological conduction due to demyelination, thermoregulation fails to expand blood vessels to dissipate heat, or local sweating cannot meet the body’s heat dissipation needs, thus causing an increase in body temperature. And the elevated body temperature is accompanied by blocked nerve electrical signal conduction, and patients feel the increase of clinical symptoms. Therefore, during the hot season, when the temperature is high, the patient should be in a relatively cool environment. Because this phenomenon is caused by blocked neuroelectrical signaling and is not a substantial re-injury to the central nervous system, pseudo-relapses do not require treatment.
Once the triggers of pseudo-relapses are known, care should be taken to avoid them. However, if a true relapse cannot be excluded, then the patient should consult his or her primary care physician to obtain timely treatment to avoid delaying the condition.