Cerebral blood flow and metabolism in complete apallic syndromes, in states of severe dementia, and in akinetic mutism.

Abstract

In complete apallic syndromes with (almost total) loss of the telencephalic grey matter, the supratentorial blood flow and oxygen uptake were found to be only about 20 per cent of the normal. Such cases show no signs of higher functions and they have an isoelectric EEG. Due to the retention of brain stem structures they may, however, show clear-cut signs of arousability with lively brain stem reflexes and primitive motor reactions. In a permanently comatose case—also without higher functions—due to a selective reticular brain stem infarction, but with retained telencephalic morphology on the whole, extremely low values (about 20 per cent of normal) for the supratentorial oxygen uptake and blood flow were also demonstrated. Other states with a severe reduction, but not a complete loss of higher functions, due to posttraumatic stupor and advanced Alzheimer's disease showed higher cerebral blood flow and metabolic values than those related above. Such cases also showed a retention of an often pathological EEG. Two patients with akinetic mutism showed relatively high flow values and by and large a normal relative weight of the cortical grey matter, as well as a normal EEG. Both cases showed slight but definite signs of remaining higher functions. It is concluded that measurements of the supratentorial cerebral oxygen uptake and blood flow may be used to quantitate the functional state of the brain in patients with a loss of, or with a severe reduction of higher functions (signs of conscious awareness, voluntary motor activity, speech, and memory). It is emphasized that a complete loss of such functions may be caused by a total loss of the cortical grey matter (the complete apallic state), or by a selective lesion of the reticular system of the brain stem.