Disinhibition of somatosensory evoked potential recovery in alcoholics

The pathogenesis of cognitive impairment in alcoholics remains unclear. Previous studies suggested that diffuse white matter atrophy is associated with cognitive impairment in alcoholics. To elucidate this issue, the present study evaluated alcoholics with cognitive impairment using the somatosensory evoked potential (SEP) recovery method, which is suitable for detecting subtle dysfunction at the cortical level. Subjects comprised 12 alcoholics with mild cognitive impairment [Mild group: Mini Mental State Examination Score (MMSE), > or =24; mean, 27.9 +/- 1.6], 12 alcoholics with moderate to severe cognitive impairment (Moderate group: MMSE score, < 24; mean, 21.0 +/- 2.5) and 12 normal subjects (Control group). SEP was recorded from the hand sensory area contralateral to the median nerve stimulated at the wrist. Single-pulse or paired-pulse stimuli at various interstimulus intervals (10-300 ms) were administered. Recovery functions of N9 (a peripheral nerve component), N20, N20-P25 and P25-N33 (cortical components) were studied. N20 recovery curves of both alcoholic groups were less suppressive than those of Controls, and P25-N33 recovery curves of the Moderate group were more excitatory than those of the Mild or Control groups. A disinhibited recovery pattern of N20 indicates subcortical dysfunction, and a disinhibited pattern of P25-N33 would be induced by cortical dysfunction. Therefore, subcortical dysfunction indicated by an abnormal N20 recovery pattern may contribute to the early cognitive impairment of alcoholics, whilst the cortical dysfunction indicated by an abnormal P25-N33 recovery pattern may contribute to the later cognitive impairment of alcoholics.