Volume of the amygdala is reduced in patients with narcolepsy - a structural MRI study

Based on the clinical observation that patients suffering from narcolepsy with cataplexy (NC) have cataplectic attacks when they experience positive emotions, it is therefore hypothesised that the abnormal processing of external emotional input through the limbic system, or motor dysregulation induced by emotions, takes place during these episodes. To date, imaging studies have failed to reveal consistent brain abnormalities in NC patients.

Considering the discrepancies in reported structural or functional abnormalities of the hypothalamus, amygdala, and nucleus accumbens, we used the MRI volumetry to determine the volumes of the amygdala and nucleus accumbens in a group of eleven patients with NC (5 males and 6 females, mean age 41.7 years ± 17.7). This data was compared to an equal number of examinations in healthy volunteers matched for age and gender.

We found a decrease in the amygdalar volume of NC patients in both raw (p<0.001) and relative (p<0.01) data sets. The difference in amygdalar volume between healthy volunteers and NC patients was about 17%. In contrast to the amygdala, we did not find any differences in the volumes of nucleus accumbens.

In the present MRI volumetric study, we found bilateral gray matter loss in the amygdala only.