[Contingent negative variation in patients with severe closed head injury--its diagnostic value as a quantitative...

CNVs were studied in 48 subjects with closed head injury followed by posttraumatic amnesia over than 7 days. Electrical motor-threshold stimulation of the median nerve or subjectively painful stimulation of the fingertip was used for imperative stimulus. An amplitude of CNV and its enhancement by painful imperative stimulus were measured and compared with those obtained from 34 normal subjects. In subacute stage within 3 months after the head injury, correlation between CNV abnormalities and an existence of some noticeable psychiatric disorders was found. In many of the subjects with CNV abnormalities, diffuse slow wave activities were observed in the background EEG, so that it was supposed that CNV abnormalities in subacute stage might reflect diffuse cerebral dysfunction and decreased vigilance. Any statistically significant correlation of CNV abnormalities to an existence of psychiatric disabilities, low score in WAIS and background EEG patterns could not be found in chronic stage 12 months after head injury. However, suppressed CNV was observed in all of 4 subjects who presented generalized epileptic patterns in the background EEG. Many of the subjects with suppressed CNV also showed a small effect of painful imperative stimulus on its amplitude. Statistically significant correlation between CNV abnormalities and work capacity was found. From these findings, together with previous observations (Tsubokawa et al. 19,36,40,44)), it is concluded that the measurement of the CNV is inimitable examination to evaluate certain psychiatric disability which is apt to be overlooked but, in fact, concerned intimately to the work capacity.