The connection between sleep and stroke

A comprehensive night sleep study in patients diagnosed with cerebral stroke is not only of pure academic interest, but it is also considered to be very helpful for practical purposes, such as helping to determine prognosis and provide therapeutic and rehabilitation facilities for patients. It has already been discovered that sleep disorders are one of the risk factors of cerebral stroke. Minor, almost undetectable clinical changes in the hemodynamics of the brain towards deterioration or improvement affect the sleep in patients with cerebral stroke. If elements of sleep, namely, periods of desynchronization accompanied by rapid eye movements combined with a decrease in muscle tone, are detected in patients in a coma, it is considered to be evidence that the stem functions of the brain have been preserved. This is a prognostically favorable factor.

In general, different periods of sleep and wakefulness when cerebral stroke occurs is a vivid illustration and proof that sleep is a remedy. According to statistics, the frequency of cerebral stroke occurrence is distributed over the periods of the day as follows:

• 0-6 h - about 17%;
• 6-12 hours - about 46%;
• 12-18 hours - about 20%;
• 18-24 hours - approximately 17%.

According to a 1995 study , provided by Pressman and co-authors, 25-45% of all cerebral stroke cases occur at night. According to researchers, the distribution is as follows:

• Morning time - 45%;
• Day time - 32%;
• Night time is 17%.

Special attention is paid to the time when the night sleep ends and the morning begins. The first few hours after awakening are especially dangerous as this is the time when cerebral stroke develops. Nevertheless, despite the obvious connection between sleep and the early postsomnic period, this connection is still poorly studied in the science of cerebrovascular pathology.

Most of the performed studies are actual clinical observations. Along with the neurological changes that is characteristic of a cerebral stroke, these studies also researched disorders in the sleep-wake cycle. Thankfully, subsequent development of polygraph research methods in neurology gave specialists an opportunity to objectively record night sleep features in patients with cerebral stroke diagnosis. Sleep medicine, a brand new branch of medicine developed by Professor A.M.Veyn, gave a push towards the development of sleep science.

Severe disorders are common for all stages and forms of cerebral stroke. Not only sleep-generating mechanisms are disrupted, but also those mechanisms that are responsible for controlling the sleep. As a result, duration of sleep is shortened, periods of drowsiness and wakefulness in the middle of the night are prolonged, awakenings are frequent and there is imbalance between individual sleep stages. Scientists think that the reason for all these disruptions is not only damage and death of brain tissue on a local level, but also a dysfunction of both local and general hemodynamics, edema and displacement of the substances located within the brainstem. Factors that impact the sleep the most are presumably the severity, nature, stage of the disease and its localization. For example, compared to hemorrhagic stroke ischemic stroke does not lead to such severe sleep disorders, however, with a favorable outcome, sleep recovery occurs much faster in hemorrhagic stroke rather than ischemic stroke. This can be explained by the fact that ischemic stroke leads to a necrosis of the brain tissue and hemorrhagic stroke leads to damage of tissues due to the stratification of brain structures caused by the hemorrhage. Hence recovery of both night sleep and general health condition passes relatively better and faster.

Development of neuroimaging methods made it possible to determine more accurately the severity of the damage and its size. The size of the damage affects the sleep a lot. A large damage causes edema of the cerebral hemisphere - in some cases even the opposite hemisphere is affected - and it also causes processes of trunk compression. The larger the damage, the more serious are the sleep disorders. This conclusion is logical and it has been confirmed by a number of studies. These studies also showed that the medial location of the damage (maximum proximity of the focus to the liquor-bearing pathways and median structures) leads to the most severe sleep disorders. Both quantitative and qualitative changes are taking place in the sleep structure. If there is medial damage which affected thalamic structures, the disappearance of "sleeping spindles" - electroencephalographic signs of the 2nd stage of sleep - are common on the side of the damage. The laterally located processes are accompanied by relatively mild sleep disorders.

The most acute stroke stage (1 week) is characterized by a number of polysomnographic and clinical features. Clinical features include severe hemodynamic, local and general cerebral neurological processes, which are very difficult to control. Depending on the direction of pathology`s development, polysomnography results in different images. Severe problems with consciousness (coma, sopor), as a rule, are accompanied by slow-wave diffuse activity, which excludes the possibility for doctors to isolate individual sleep stages of the patient. Nevertheless, as noted above, appearance of individual stages of sleep in a patient is a favorable sign for prognosis considering that there is cerebral diffuse electric activity.

During the most acute period, if the consciousness of the patient is preserved, doctors encounter both inversion and polyphase of the sleep-wake cycle. This can be explained by circadian disorders. In the first case, patients fall asleep several times during the day, whereas in the second case there is a shift in the cycle characterized by night wakefulness and daytime sleep. Characteristic signs of this period, accompanied by cerebral symptoms, include frequent awakenings, a decrease of d-sleep and an absence of rapid eye movement sleep.

The location of damage to the brainstem or to the hemispheres affects structures of sleep differently. Damage to the right hemisphere is characterized by a more serious disorder, which include decrease in the duration of the fast sleep and d-sleep phase, increase in the duration of the wakefulness, increase of the first stage of sleep, increase in the number of awakenings, the duration of sleep. This damage is also characterized by low coefficient of sleep efficiency. In patients with right hemisphere damages, the cause of severe sleep disorders lies in the deep connection between the hypnogenic structures of the brain and the right hemisphere. Additionally to sleep disorders, these patients also develop changes in the regulations of vegetative nervous system. These changes are manifested by tachycardia, various types of cardiac arrhythmias and high blood pressure.

The left hemisphere is closely linked to the activating systems of the brain. Some researchers think that this link is the reason for frequent consciousness disorders typical for left hemispheric strokes.

Strokes with different stem localization are of a particular interest for the researches. When a stroke occurs in the area of the variolium bridge, fast sleep phase decreases drastically while its latent period increases. There is also a decrease in the duration of d-sleep.

Night sleep structure was studied in patients suffering from cerebral stroke in groups with initially bad and good sleep. The study showed that patients who had previously been having certain sleep problems, such as frequent awakenings, long falling asleep time, dissatisfaction with sleep,and early awakening had worse indicators of sleep quality regardless of other factors. This fact proves that, apart from stroke, structural changes in sleep are also influenced by the initial regulation of the sleeping-awakening cycle.

The sleep structure in patients with stroke varies depending on what time of the day the stroke occurred. A characteristic feature of cerebral stroke, which happened during sleep, is a very active rapid eye movement sleep. Together with the "vegetative storm" that accompanies this phase, rapid eye movement sleep can be one of the causes why cerebral stroke occurred at this time of day. According to statistics, patients with a "morning stroke" compared to "daylight" and "night" stroke, has the shortest period of rapid eye movement sleep.

Thus, studying the structure of the night sleep is an essential element in treatment of both stroke patients and people with the so-called pre-stroke diseases. Modern life rhythm increasingly affects the harmony of sleep-wakefulness biorhythms and natural rhythms of a person, which leads to the so-called desynchronosis syndrome. This is a term used to describe mismatched dynamics of the internal environment of a person. This can be a potential cause of various vascular pathologies. To prevent and treat stroke, it is recommended to restore and maintain a natural sleep-wakefulness biorhythm by using physical (phototherapy) or conservative(sleep drugs) treatment methods.

Also see other articles on this topic:

• Radon therapy of stroke
• Mediterranean diet reduces the risk of stroke
• Snoring can be a forbearer of a stroke

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