the abolition of sweating from the upper body as well as the axillae and both upper limbs may have significantly reduced the capacity of the patient to lose heat through sweating during exercise. Anhidrosis in the head and neck after sympathectomy affects a proportion of patients, but is often neglected in most reports of post-sympathectomy complications [3]. The loss of head and neck sweating in this patient may have further impaired overall heat loss. However we would also note that the degree of heat loss impairment after sympathectomy has never been quantified, and its effect on body temperature during exercise remains to be established.
http://ats.ctsnetjournals.org/cgi/content/full/84/3/1025