Coma
In medicine, a coma is a profound state of unconsciousness. A person in a coma cannot be awakened, fails to respond normally to pain, light or sound, does not have sleep-wake cycles, and does not take voluntary actions. A person in a state of coma can be described as comatose.
Understanding the condition
Coma is a sleeplike state in which the patient makes no purposeful response to the environment and from which he or she cannot be aroused. The eyes are closed and do not open spontaneously. The patient does not speak, and there is no purposeful movement of the face or limbs or non-purposeful reflex movements mediated through spinal cord or brainstem pathways.
Underlying causes
Coma results from a disturbance in the function of either the brainstem reticular activating system above the midpons or of both cerebral hemispheres, since these are the brain regions that maintain consciousness.
The severity and mode of onset of coma depends on the underlying cause. For instance, deepening hypoglycemia (low blood sugar) or hypercapnia (increased carbon dioxide levels in the blood) initially cause mild agitation and confusion, then progress to obtundation, stupor and finally complete unconsciousness. In contrast, coma resulting from a severe traumatic brain injury or subarachnoid hemorrhage can be instantaneous. The mode of onset may therefore be indicative of the underlying cause.
The most crucial aspect of the history is the time over which coma develops. In the absence of precise details about the mode of onset, information about when the patient was last seen in an apparently normal state may assist in establishing the time course of the disease process.
1. A sudden onset of coma suggests a vascular origin, especially a brainstem stroke or subarachnoid hemorrhage.
2. Rapid progression from hemispheric signs, such as hemiparesis, hemisensory deficit, or aphasia, to coma within minutes to hours is characteristic of intracerebral hemorrhage.
3. A more protracted course leading to coma (days to a week or more) is seen with tumor, abscess, or chronic subdural hematoma.
4. Coma preceded by a confusional state or agitated delirium, without lateralizing signs or symptoms, is probably due to a metabolic derangement.
Glasgow Coma Scale
The Glasgow Coma Scale or GCS, sometimes also known as the Glasgow Coma Score is a neurological scale which aims to give a reliable, objective way of recording the conscious state of a person, for initial as well as continuing assessment. The scale was published in 1974 by Graham Teasdale and Bryan J. Jennett, professors of neurosurgery at the University of Glasgow. The scale comprises three tests: eye, verbal and motor responses. GCS is used as part of several ICU scoring systems to assess the status of the central nervous system.
Progress
Outcomes range from recovery to death. Comas generally last a few days to a few weeks, rarely more than 2 to 5 weeks but it can last as long as several years. Rarely it lasts longer but it is possible.
According to the Guinness Book of Records, the longest period spent in coma was by Elaine Esposito. She did not wake up after being anaesthetized for an appendectomy on August 6, 1941, at age 6. She died on November 25 1978 at age 43 years 357 days, having been in a coma for 37 years 111 days.
People may emerge from a coma with a combination of physical, intellectual and psychological difficulties that need special attention. Recovery usually occurs gradually patients acquire more and more ability to respond. Some patients never progress beyond very basic responses, but many recover full awareness. Regaining consciousness is not instant: in the first days, patients are only awake for a few minutes, and duration of time awake gradually increases.
References
Medical Encyclopedia from Mobile Reference
Clinical Neurology, 7e, Roger P. Simson, MD, David A. Greenberg, MD, PHD
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