Facial sweating in Horner's syndrome.

The distribution of sweating on the face was studied in 31 patients with Horner's syndrome. In patients whose lesion was known to be distal to the bifurcation of the common carotid artery impairment of sweating was confined to the medial aspect of the forehead and side of the nose. In more proximal lesions loss of sweating involved the whole of one side of the face. Facial sweating was normal in 6 patients with avulsion injuries of the brachial plexus and in 2 patients with a lateral medullary syndrome. These findings suggest that the pattern of sweating in Horner's syndrome may be useful in some patients in localizing the site of the lesion.