Sweat gland and pupillary responsiveness in Horner's syndrome.

Eight patients with Horner's syndrome (five with a 1st neuron lesion and three with a 2nd neuron lesion) were examined for their pupillary responses to pharmacologic stimulation with tyramine (2%) and with phenylephrine (1%) eye drops. The same patients were also evaluated for their forehead sweating pattern on stimulation with body heating and pilocarpine injection, using the Evaporimeter. Five patients had a brain stem (1st sympathetic neuron) lesion, while three patients had had a traumatic C8-Th1 root avulsion and hence had a preganglionic neuron lesion. The average response with the phenylephrine eye test and the pilocarpine sweat test differed markedly between the two groups; only the central neuron lesion group had a supersensitivity reaction to both drugs. These procedures may be of diagnostic value in localizing the lesion in patients with a Horner's syndrome of unknown etiology. Patients with 3rd neuron lesion have not been examined with this combination of techniques.