Causes and pathogenesis of impaired consciousness

The causes of mental disorders are extremely diverse. By pathogenesis, all disorders of consciousness are divided into organic, metabolic and psychogenic.

• Organic brain damage, capable of leading to a breakdown of consciousness down to a coma, includes almost all known primary and secondary diseases and pathological conditions of the central nervous system, both focal and diffuse. First of all, they include acute brain lesions that lead to its destruction and compression: craniocerebral trauma, ischemic stroke, intracranial hemorrhages of various etiologies (intracerebral, subdural and epidural hematomas, intraventricular, subarachnoid hemorrhages). Especially dangerous are acute processes with primary damage to the brainstem (hemorrhages and infarcts of the trunk), as well as processes accompanied by extensive one- or two-side lesions of the large hemispheres or subtentorial structures, since they can quickly lead to the development of brain dislocation with secondary damage to the trunk. The development of comatose states can result in timely not diagnosed volume formations of supra- and subtentorial structures (tumors, brain abscesses). Disturbances of consciousness can be caused by diseases that lead to diffuse damage to the substance and membranes of the brain: demyelinating diseases, specific and nonspecific encephalitis, encephalomyelitis, leptomeningitis, vasculitis. Almost all disorders of consciousness caused by organic pathology of the central nervous system can detect certain focal symptoms that indicate the localization of the primary or secondary lesion: shell symptoms, cranial nerve lesions, pyramidal, extrapyramidal, stem symptoms.
• Metabolic factors leading to disorders of consciousness, constitute a large group. In general, they can be divided into internal and external, or endo- and exotoxic. In some situations, such a division is very conditional. The causes of endogenous intoxications are:
  • - pathology of internal organs, leading to such conditions as hepatic and renal insufficiency (uremia), eclampsia of pregnant women;
  • disruption of endocrine glands functions: diabetes mellitus (hypo- and hyperglycemic coma), adrenal insufficiency, thyrotoxicosis, hyperparathyroidism;
  • severe vitamin deficiency (thiamine, folic acid, B ₁₂, etc.);
  • disturbances of water-electrolyte balance (hypo- and hyperosmolar coma), including pituitary damage (pituitary coma), acid-base balance disturbance (respiratory or metabolic acidosis or alkalosis), anemia, severe bacterial and viral infections, cancer intoxication, anaphylactic shock, etc.

A special place among metabolic disorders is occupied by states leading to hypoxia and anoxia of the brain: anoxic anoxia (oxygen for some reason does not enter the blood in the required quantities), anemic anoxia (reduced hemoglobin content), ischemic anoxia (conditions leading to a rapid overall reduction of cerebral blood flow: a decrease in cardiac output with myocardial infarction, arrhythmia, asystole, vasodepressor reactions in shock states, etc.). To external influences, various drugs (barbiturates, tranquilizers, narcotic substances, antidepressants, salicylates, etc.), toxic substances (alcohol, methyl alcohol, natural and industrial poisons, carbon monoxide), alimentary factors (alimentary-dystrophic coma ), hypo- and hyperthermia (heat stroke). The common property of all metabolic disorders of consciousness is the comparative poverty of focal neurological symptoms, even in patients with coma.

• In a rare case, psychogenic disorders can manifest themselves as complete areactivity. This condition can occur with hysteria, severe depression, schizophrenia. For psychogenic isaktivnosti normal somatic and neurological status with preservation of all physiological reflexes, absence of changes in laboratory analyzes and practically normal EEG are typical.

The speed of development and the duration of the disorders of consciousness are varied. The disease can begin with sudden complete loss of consciousness (hemorrhage into the trunk, ventricular hemorrhage) or it may be preceded by a period of prolonged, often wavy change in consciousness as a type of darkening or confusion (endogenous intoxications), an episode of psychomotor agitation (hypoxia, craniocerebral trauma), epileptic seizure (epilepsy, cerebral circulation disorders), development of focal symptoms (stroke, swelling). Disorders of consciousness can be short-lived (fainting, absences) and indefinitely long. The latter refers mainly to deep oppression of consciousness. Long-term disorders of consciousness are called chronic. Chronic disorders, as a rule, are the outcome of a coma. Criterion for the transition of acute disturbance of consciousness into chronic is suggested to be a period of 2-4 weeks.

[1], [2], [3], [4], [5], [6], [7], [8], [9]