Many toxic encephalopathies are iatrogenic in origin.
The CNS is affected by many drugs in a variety of different ways, but the resultant disturbances of CNS function generally reverse with withdrawal of the offending medication. Attention here is directed at those medications that cause diffuse disturbances of cerebral function manifested particularly by alterations in the level of consciousness. Coma is a common sequel to overdosage with various drugs, including hypnotics, sedatives, neuroleptics, antidepressants, anticonvulsants, and analgesics. Spontaneous and reflex ocular movements are typically impaired, even at an early stage, in barbiturate and phenytoin intoxication. Depending on the depth of coma, the corneal reflex may be lost, and painful stimuli to the trunk or extremities may lead to purposive movements, decorticate or decerebrate posturing, or absence of motor response.