Alcoholic dementia

Chronic alcoholism in the absence of Wernicke-Korsakoff syndrome and cirrhosis does not result in the loss of serotonergic neurons from the median raphe nucleus

Previous studies have identified alcohol, thiamine deficiency and liver disease as contributing to the neuropathology of alcohol-related brain damage. In order to examine the effects of alcohol toxicity and thiamine deficiency on serotonergic neurons in the median raphe nucleus (MnR), alcoholic and previously published Wernicke-Korsakoff syndrome (WKS) cases without liver disease, were compared with age-matched non-alcoholic controls. While there was no difference between the estimated number of serotonergic neurons in either controls or alcoholics without WKS (means of 63,010 +/- 8,900 and 59,560 +/- 8,010 respectively), a substantial loss of serotonergic neurons was previously found in WKS cases (mean of 19,050 +/- 13,140). Further analysis revealed a significant difference in the maximum daily alcohol consumption between these groups. However, analysis of covariance showed that the number or serotonergic neurons in the MnR did not correlate with the amount of alcohol consumed. Therefore, our results suggest that cell loss in the MnR can be attributed to thiamine deficiency rather than alcohol per se.

Chronic alcoholics without Wernicke-Korsakoff syndrome or cirrhosis do not lose serotonergic neurons in the dorsal raphe nucleus

Despite the considerable evidence that alcoholics have perturbation of serotonergic function, there is little pathological evidence for alcohol directly affecting the nervous system. The present study aims to assess neuronal loss that occurs as a consequence of alcohol neurotoxicity in the serotonergic dorsal raphe nucleus (DRN). To that end, the brains of eight alcoholics and eight age-matched control cases were carefully screened to eliminate serious liver disease, the sequela of thiamine deficiency, Wernicke-Korsakoff syndrome (WKS), and other pathological abnormalities. Brains were formalin-fixed for 2 weeks, cut, and then immunohistochemically stained using a monoclonal PH8 antibody specific for the rate-limiting enzyme of serotonin synthesis, tryptophan hydroxylase. The morphology of the serotonin-synthesizing neurons and their average size was similar in all cases. However, there was a reduction in the staining intensity of the reaction product in the DRN serotonergic neurons of most alcoholics. Neuronal counts on spaced serial sections revealed that there were an estimated average total of 106,100 +/- 19,500 serotonergic neurons in the DRN of alcoholics and 108,300 +/- 11,800 in the DRN of controls, indicating that in most alcoholics there is no reduction in the number of these neurons. Therefore, the effect of chronic alcohol consumption on the serotonergic system, in the absence of WKS or liver disease, seems to be functional rather than neuropathological.