Clinical application of event related potentials in patients with brain tumours and traumatic head injuries.

Event related potential recording and psychometric evaluation of cognitive impairment were carried out on 21 patients with brain tumours, 21 patients with severe head injuries and 24 controls. The tumour and trauma patients who met the psychometric inclusion criteria for dementia, but not the non-demented patients, had significantly longer N2 and P3 latencies than the controls. In assessing individual patients P3 latency correctly differentiated between demented and non-demented patients in 81% of cases (for N2 latency 77%). Particularly P3 latency may provide a practical and objective measure of mental impairment in neurosurgical disorders producing dementia. Marked asymmetry in N2 and P3 amplitudes between hemispheres was observed in a number of cases. No significant relationship was found between diminution of N2 and P3 components and side of lesion.