We evaluated the feasibility of using a portable infrared thermal camera to quantify the degree of thermal dysregulation (cold hands/feet) and test for naturally occurring within-patient skin temperature asymmetry in Rett syndrome.

Infrared thermal images were acquired passively from 15 patients (mean age = 13.7 years, range 4-47) with clinical diagnoses of Rett. Images were acquired using a FLIR T400 infrared thermal camera (still images recorded at 5 Hz, resolution of 320 × 240 pixels, thermal sensitivity = 0.05°C; capture session lasted approximately 3 minutes). The infrared thermal camera was orthogonal to the body part (hands, feet) and positioned approximately 1 meter from the skin's surface.

There were large intraindividual left/right differences in temperature. Seven (47%) and eight (53%) patients had statistically significant (P <0.05) left/right asymmetries between hands (mean difference = 0.87°C, standard deviation = 1.21) and feet (mean difference = 1.73°C, standard deviation = 3.03), respectively. Coders were reliable (intraclass correlations 0.97-0.99) on temperatures and selection of anatomical regions of interest.

The degree of thermal asymmetry may reflect prolonged activity of the sympathetic nervous system and individual differences in sympathetic regulation. As clinical trials emerge and endpoints are considered, portable infrared thermal camera may provide one noninvasive means of evaluating changes in sympathetic regulation.