Mental impairment in unilateral frontal tumours: role of the laterality of the lesion.

Seventy-two patients with left frontal lobe tumours and 68 patients with right frontal lobe tumours were studied clinically and experimentally. Left frontal lobe tumours were consistent with poorer motor and mimical activity, speech disturbances, manifested as efferent motor or dynamic aphasia, slowing down of the tempo of mental processes, deterioration of verbal memory, reduced generalization ability, difficulties in attention shifting and stereotyped thinking. In mild cases, the above impairments were associated with depressed feelings, in advanced cases with apathico-abulic syndrome. Right frontal lobe tumours were found to raise spirits and led to euphoria, underestimation of one's disorder and full anosognosia, loss of critical faculty, attention instability and distractibility. Development of mental disorders in left-sided frontal tumours mainly depends on tumour localization, while in right-sided ones tumour size and malignancy are the determining factors.