Denervation supersensitivity in Horner's Syndrome.

The mechanism of denervation supersensitivity was investigated, using the pupillary system as an experimental model. A pharmacological study was carried out in six patients with Horner's syndrome due to postganglionic lesions. Administration of cocaine 4 percent resulted in dilatation of the normal pupil, while subsequent instillation of phenylephrine (2.5-5 percent) produced equal dilatation in both eyes. The results of the study indicate that denervation supersensitivity of the pupil can be explained solely by impaired reabsorption of catecholamines.