Autonomic dysfunction in the early stage of ALS with bulbar involvement

Our objective was to assess the autonomic function of ALS patients with and without bulbar signs to characterize dysautonomia in ALS disease. Standard autonomic tests and spectral analysis of heart rate variability (HRV), reflecting changes in the sympathovagal balance, were examined in 33 ALS patients (14 with bulbar signs) and 30 controls. Results showed that in the supine position, ALS patients had significantly lower total power and absolute values of high-frequency power indicating a depressed sinus arrhythmia. Patients with bulbar signs showed more marked autonomic alterations at rest. Tilting did not induce the expected increase in low-frequency and decrease in high-frequency power of HRV in all patients. No correlation was found between autonomic tests and clinical parameters. Our findings suggest an early subclinical involvement of the autonomic system in ALS, particularly affecting parasympathetic cardiac control. Patients with prominent bulbar signs show a more severe autonomic dysfunction under resting conditions.