Effects of graded load of artificial gravity on vestibule-spinal and vestibulo-ocular functions

To clarify the trajectory of the hypothalamo-spinal pathway involved with thermal sweating (TS), I made a qualitative study of 38 patients with lateral medullary syndrome, 37 infarctions and one probable inflammation. Five patients showed “normal” thermal sweating and 33 an “abnormal” thermal sweating; ipsilateral hypohidrosis was present chiefly in the upper body. Relative hypohidrosis in the side of the body opposite to the side of the brain lesionwas seen in 4 cases. Contralateral facial sweating before heating was seen in 4 cases. Quantitative data (mg/cm/min) from 13 subjects in the “abnormal” thermal sweating group were compared to those in age-matched control subjects with “normal” thermal sweating. Sweat volume (SV) at the forehead on the side contralateral to the lesion in the patient group was significantly larger than on the ipsilateral side (p=0.0007) and also larger than in the control group (p=0.0442). In contrast, sweat volume at the ipsilateral forearm in the patient group was significantly lesser than on the contralateral side (p=0.0012), and also lesser than in the control group. Sweat volume at the ipsilateral side of the forehead, at the contralateral forearm, and at both legs showed no significant difference between patients and control subjects. The results indicated that the hypothalamo-spinal pathway does not evenly innervate the entire body, but has some regional predominance. The hypohidrosis at the ipsilateral forearm suggests that the hypothalamo-spinal pathway may exert a facilitatory influence on sweating of the upper body. The absence of any apparent reduction of thermal sweating at the legs suggests that there might be crossing fibers in the hypothalamo-spinal pathway involved in the thermal sweating of the lower body; another possibility is that there are cross-communicating fibers in more peripheral parts of the pathway, as suggested on morphological grounds by Cowley & Yeager (1964) and Webber (1956). Furthermore, excessive sweating at the forehead on the side contralateral to the lesion may be due mainly to a damage to the inhibitory pathway, and the pathway may be related predominantly to sweating of the upper body, particularly of the face and neck. (The Autonomic Nervous System, 47: 479–484, 2010)