Mammillothalamic functional connectivity and memory function in Wernickes encephalopathy

There is still debate over the neural mechanisms underlying pathogenic and even recovery processes of Wernickes encephalopathy. Therefore, we attempted to validate the usefulness of resting-state functional connectivity analysis in assessing memory function and its neural correlation with the mammillothalamic tract in patients recovering from Wernickes encephalopathy. Seven chronic alcoholics recovering from Wernickes encephalopathy, 14 alcoholic comparisons without Wernickes encephalopathy, and 14 healthy comparisons underwent functional connectivity MRI scans, as well as verbal and non-verbal memory tests after at least a 1 month abstinence from alcohol. Resting-state functional connectivity strength between the anterior thalamus and the mammillary bodies was investigated by calculating temporal correlations in magnetic resonance signal levels between the two regions during a 5-min passive viewing task. The mean values of the functional connectivity strength between the left anterior thalamus and the ipsilateral mammillary body differed significantly between Wernickes encephalopathy patients and healthy comparisons (P 0.014). This connectivity strength in alcoholic comparisons fell between those of the former two groups, with a significant difference from that of healthy comparisons (P 0.038). In addition, the strength of this left-sided functional connectivity significantly correlated with delayed verbal recall scores (r 0.771, P 0.042) and verbal recognition score (r 0.825, P 0.022) in patients with Wernickes encephalopathy. Our findings indicate that memory function in patients recovering from Wernickes encephalopathy parallels the level of the mammillothalamic functional connectivity; this supports the usefulness of resting-state functional connectivity analysis as a practical alternative to pathological examination of the mammillothalamic tract in living patients with Wernickes encephalopathy.