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In hospital and emergency neurology, the clinical analysis of unresponsive and comatose patients is an urgent practical necessity. The underlying disease and the direction in which it is evolving must be determined rapidly in order to protect the brain against irreversible damage. When called upon, the physician must therefore be prepared to implement prompt action that allows little time for deliberate, leisurely investigation.
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Some idea of the dimensions of the problem of coma, and how little it has changed over time, can be obtained from published statistics. Almost ninety years ago, in two large municipal hospitals, it was estimated that 3 percent of all emergency admissions were for diseases that had caused coma. Alcoholism, cerebral trauma, and cerebrovascular diseases were the most common, accounting for 82 percent of the comatose patients admitted to the Boston City Hospital (Solomon and Aring). Epilepsy, drug intoxication, diabetes, and severe infections were the other major causes. It is perhaps surprising to learn that contemporary figures from large city hospitals differ only slightly, with intoxication, stroke, and cranial trauma still standing as the “big three” of coma-producing conditions. For example, in a series described in the 1980s (Plum and Posner) (Table 16-1), a majority was the result of exogenous (drug overdose) and endogenous (metabolic) intoxications and hypoxia, 25 percent of cases proved to have cerebrovascular disease, and intracranial masses—such as tumors, abscesses, and hemorrhages—made up about one-third of cases. Subarachnoid hemorrhage, meningitis, and encephalitis accounted for another 5 percent. Perhaps the proportions of the main causes have changed but in a more contemporary review of 14 studies of coma etiology, excluding trauma, the main causes were stroke (including intracerebral and subarachnoid hemorrhage), postanoxic coma, poisoning (including intoxication), and metabolic encephalopathy (Horsting et al). Common in many series, although obvious and often transient, is coma that follows seizures or resuscitation from cardiac arrest.
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