Loss of serotonin-containing neurons in the raphe of patients with myotonic dystrophy: a quantitative immunohistochemical study and relation to hypersomnia

Hypersomnia occurs frequently in patients with myotonic dystrophy (MyD). We performed a quantitative immunohistochemical study of serotonin (5-HT)-containing neurons linked to hypersomnia in the dorsal raphe nucleus (DRN) and the superior central nucleus (SCN) in 8 patients with MyD, 5 of whom showed hypersomnia, and in 12 age-matched controls. The densities of 5-HT neurons in the DRN and the SCN were significantly lower in MyD patients with hypersomnia than in MyD patients without hypersomnia and controls. These data suggest that the loss of 5-HT neurons of the DRN and the SCN is associated with the presence of hypersomnia in MyD.