Relationship between cardiac parasympathetic dysfunction and the anteroposterior diameter of the medulla oblongata in multiple system atrophy

Purpose Neurodegeneration of the nucleus ambiguus and the dorsal vagal motor nucleus has been implicated in cardiac parasympathetic dysfunction in multiple system atrophy (MSA). The nucleus ambiguus and the dorsal vagal motor nucleus, which are located in the medulla oblongata (MO), control the autonomic-specifically, the parasympathetic-functions of the body. The aim of our study was to investigate the relationship between cardiac parasympathetic dysfunction and the anteroposterior diameter of the MO in MSA by quantitatively analyzing magnetic resonance imaging (MRI) outcome measures. Methods We retrospectively assessed 40 consecutive patients with probable MSA and 25 age- and sex-matched controls. The anteroposterior diameter of the MO at two locations (MO diameter-A and -B) and the diameters of the midbrain and pons were measured by conventional MRI. A cardiac parasympathetic function score (CP-score) and cardiac sympathetic function score (CS-score) were generated by calculating the z-scores of multiple autonomic function tests. The relationship between the scores and the measured diameters of the brainstem was also investigated. Results The CP-score and CS-score were significantly lower in the patients with MSA than in the controls (CP-score: 0.61 +/- 0.75 vs. - 0.38 +/- 0.52, p < 0.001; CS-score: 0.91 +/- 1.06 vs. - 0.57 +/- 1.07, p < 0.001). Also, in the patients with MSA, the CP-score was significantly correlated with MO diameter-A (r = 0.40, p = 0.010), and the CS-score was significantly correlated with the diameter of the midbrain (r = 0.33, p = 0.038). Conclusion The anteroposterior diameter of the MO is a potential imaging marker of parasympathetic dysfunction in MSA.