Loss of catecholaminergic neurons in the medullary reticular formation in myotonic dystrophy

Objective: To clarify the possible relation between the extent of involvement of catecholaminergic neurons and the presence of alveolar hypoventilation in patients with myotonic dystrophy (MyD). Background: Respiratory insufficiency has been reported frequently in MyD patients. Recent data support the hypothesis that this respiratory failure results from a primary dysfunction of the CNS. Methods: The authors performed a quantitative immunoreactive study of tyrosine hydroxylase immunoreactive (TH+) neurons linked to hypoventilation in the dorsal central medullary nucleus (DCMN), the ventral central medullary nucleus (VCMN), and the subtrigeminal medullary nucleus (SMN)-where the autonomic respiratory center is thought to be located-in eight MyD patients and in 10 age-matched control subjects. Alveolar hypoventilation of the central type was present in three of the MyD patients but not in the remaining MyD patients or the control subjects. Results: The densities of TH+ neurons of the DCMN, the VCMN, and the SMN in MyD patients with hypoventilation were significantly lower than in those without hypoventilation (p < 0.02, p < 0.01, and p < 0.01, respectively) and control subjects (p < 0.01, p < 0.01, and p < 0.01, respectively). Conclusions: These data suggest that the loss of TH+ neurons of the DCMN, the VCMN, and the SMN is associated with the presence of hypoventilation in MyD and may be an important feature of MyD.