Horner's syndrome. Sweat gland and pupillary responsiveness in two cases with a probable 3rd neurone dysfunction.

Two patients with a Horner's syndrome due to a probable 3rd neurone lesion were examined with regard to the pupillometric and evaporimetric patterns. The results are compared with those found in patients with a Horner's syndrome due to a 1st or 2nd neurone lesion, previously described by our group. Concurring with observations by others, the pupil on the symptomatic side did not dilate at all when stimulated with hydroxy-amphetamine eye drops. Postganglionic dysfunction may thus be distinguished from 1st and 2nd neurone dysfunction. Supersensitivity was present on the side of the Horner's syndrome, both on pupillometry (phenylephrine stimulation) and in the medial part of the forehead at evaporimetry (pilocarpine stimulation). The lateral part of the forehead, however, did not demonstrate deficient evaporation in these postganglionic sympathetic lesions.