Basically, disorders of cerebral blood flow, such as occur in brain injury or stroke due to hemorrhage or a clogged blood vessel, can be distinguished from metabolic disorders, which can occur in poisoning by drugs or medications, but also in diabetes, massive liver weakness, or thyroid disease.
As further causes, disorders of brain function play an important role. For example, an inflammation of the brain, a seizure disorder, a brain tumor or a brain injury after an accident can be responsible for unconsciousness. In this case, the excitation processes in the brain are so disturbed that only more primitive functions can be performed.
Disturbances of cerebral blood flow
It is particularly common for brief fainting spells to be caused by a short-term disturbance in cerebral blood flow when one of the nerve centers that control cardiac function and are located at the heart and carotid arteries malfunctions. Among other things, these centers control the level of blood pressure in the body’s periphery – if there is a sharp drop in blood pressure for a short time, the brain is not supplied with sufficient blood and virtually switches to “emergency power.”
These brief unconsciousnesses are called syncope – depending on the affected nerve center, there are, for example, vagovasal syncope, micturition syncope (when unconsciousness occurs during urination), cough syncope, orthostatic syncope (when unconsciousness occurs as soon as the affected person moves from horizontal to vertical), or the Adam Stokes seizure, in which our biological pacemaker in the heart briefly stops.
What are the manifestations of unconsciousness?
As the disorder progresses, all mental processes slow down until consciousness is so impaired that sensory perception is no longer possible, and conscious control over various bodily functions also becomes limp: for example, the muscles become slack – the affected person falls from a standing position – and sometimes control over urination or defecation is impaired.
In the clinic, a distinction is readily made in cases of unconsciousness as to whether the affected person fell in the process or whether the unconsciousness was so brief and did not affect all levels of experience that a fall could be avoided. Especially in syncope, generalized seizures in epilepsy, but also hypoglycemia in diabetes or an increase in intracranial pressure, as can wrap up after a hemorrhage in an accident, a fall is typical.
Unconsciousness without a fall
Other forms of unconsciousness occur without a fall: These include so-called abscensory and complex-focal seizures, forms of epilepsy in which there is no generalized seizure but only a brief disturbance of consciousness, or a short-term disturbance of blood flow in the brain caused by a small blood clot, a so-called TIA (transient ischemic attack), which can be a harbinger of a stroke, just like a migraine attack, which first announces itself with an aura, in which the affected person only perceives everything as if through a veil.
After a short period of unconsciousness, the affected person can often remember feeling black or nauseous; migraine patients, for example, describe the symptoms of an aura with flickering at the edge of the visual field or a kind of tunnel vision. In cases of prolonged unconsciousness, however, the shutdown of brain functions over an extended period of time often results in amnesia, or a gap in memory, which can span many days, depending on the cause of the unconsciousness.
