The BRAIN is the organ of the mind. Normal conscious alertness depends upon its continuous adequate supply with oxygen and glucose, both of which are essential for the brain cells to function normally. If either or both of these are interrupted, altered consciousness results. Interruption may be caused by three broad types of process affecting the brain stem: the reticular formation (a network of nerve pathways and nuclei-connecting sensory and motor nerves to and from the cerebrum, cerebellum, SPINAL CORD and cranial nerves) and the cerebral cortex. The three types are di?use brain dysfunction – for example, generalised metabolic disorders such as URAEMIA or toxic disorders such as SEPTICAEMIA; direct effects on the brain stem as a result of infective, cancerous or traumatic lesions; and indirect effects on the brain stem such as a tumour or OEDEMA in the cerebrum creating pressure within the skull. Within these three divisions are a large number of speci?c causes of unconsciousness.
Unconsciousness may be temporary, prolonged or inde?nite (see PERSISTENT VEGETATIVE STATE (PVS)), depending upon the severity of the initiating incident. The patient’s recovery depends upon the cause and success of treatment, where given. MEMORY may be affected, as may motor and sensory functions; but short periods of unconsciousness as a result, say, of trauma have little obvious e?ect on brain function. Repeated bouts of unconsciousness (which can happen in boxing) may, however, have a cumulatively damaging e?ect, as can be seen on CT (COMPUTED TOMOGRAPHY) scans of the brain.
POISONS such as CARBON MONOXIDE (CO), drug overdose, a fall in the oxygen content of blood (HYPOXIA) in lung or heart disease, or liver or kidney failure harm the normal chemical working or metabolism of nerve cells. Severe blood loss will cause ANOXIA of the brain. Any of these can result in altered brain function in which impairment of consciousness is a vital sign.
Sudden altered consciousness will also result from fainting attacks (syncope) in which the blood pressure falls and the circulation of oxygen is thereby reduced. Similarly an epileptic ?t causes partial or complete loss of consciousness by causing an abrupt but temporary disruption of the electrical activity in the nerve cells in the brain (see EPILEPSY).
In these events, as the brain’s function progressively fails, drowsiness, stupor and ?nally COMA ensue. If the cause is removed (or when the patient spontaneously recovers from a ?t or faint), normal consciousness is usually quickly regained. Strokes (see STROKE) are sometimes accompanied by a loss of consciousness; this may be immediate or come on slowly, depending upon the cause or site of the strokes.
Comatose patients are graded according to agreed test scales – for example, the GLASGOW COMA SCALE – in which the patient’s response to a series of tests indicate numerically the level of coma.
Treatment of unconscious patients depends upon the cause, and range from ?rst-aid care for someone who has fainted to hospital intensive-care treatment for a victim of a severe head injury or massive stroke.... unconsciousness
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