In psychogenic coma there is an active resistance to eyelidopening and the eyes will tend to avoid looking at the examiner. Persistent vegetative state resembles coma. This condition occurs fromsevere injury to higher cortical structures resulting in a total lack ofresponse to the external environment, however the patient may still have sleep and wake cycles and spontaneous eye opening. Akinetic mutism resultsfrom damage to specific areas of the frontal or limbic cortex, resulting in aloss of interest in the environment, even though the patient may appearotherwise neurologically normal. Brain dead may also mimic coma.
Structural lesions involve thesupratentorial or infratentorial area.
A pertinent history includes history of drug abuse, headache, fever, or previous medicalconditions. As the patient may not be able to provide a history, much of the evaluation will depend on the examination. The general physical examination should include the vital signs. Breath may reveal alcohol, acetone, or the smell of hepaticfailure or uremia. Hypothermia may be due to exposure, overwhelming sepsis, drug effect, hypoglycemia,hypothyroidism, or Wernicke's encephalopathy.