Cold face test demonstrates parasympathetic cardiac dysfunction in familial dysautonomia

In familial dysautonomia (FD), i.e., Riley-Day syndrome, parasympathetic dy sfunction has not been sufficiently evaluated. The cold face test is a noni nvasive method of activating trigeminal brain stem cardiovagal and sympathe tic pathways and can be performed in patients with limited cooperation. We performed cold face tests in 11 FD patients and 15 controls. For 60 s, cold compresses (0-1 degrees C) were applied to the cheeks and forehead while w e monitored heart rate, respiration, beat-to-beat radial artery blood press ure, and laser-Doppler skin blood flow at the first toe pulp. From these me asurements heart rate variability parameters were calculated: root mean squ are of successive differences (RMSSD), coefficient of variation (CV), low- and high-frequency (LF and HF, respectively) power spectra of the electroca rdiogram and the LF transfer function gain between blood pressure and heart rate. All patients perceived cold stimulation and acknowledged discomfort. In controls, heart rate and skin blood flow decreased significantly during cold face test; in patients, both parameters decreased only briefly and no t significantly. In controls, blood pressure, RMSSD, CV, and heart rate HF- power spectra increased but remained unchanged in patients. Respiration, as well as heart rate LF power spectra, did not change in either group. In co ntrols, LF transfer function gain between blood pressure and heart rate ind icated that bradycardia was not secondary to blood pressure increase. We co nclude that the cold face test demonstrated that patients with FD have a re duced cardiac parasympathetic response, which implies efferent parasympathe tic dysfunction.