P 325
Acquired segmental iris dilator muscle synkinesis due to deglutition
B. I. Böhme
Background: The case of a ten-year-old boy with Horners syndrome and an extraordinary misinnervation of the iris dilator muscle is reported.
Patient/Methods: The syndrome occured after surgical removement of a neuroblastoma from the right side of the neck at the age of three days. Later on a distortion of the right pupil has been observed. The pupil dilated segmentally during drinking. We instilled cocaine hydrochloride and pholedrine formate and observed the pupil during the act of swollowing.
Results: The diagnosis of Horners syndrome and a lesion of the postganglionic (third order) sympathetic neuron was proved. During drinking the right pupil distorted at 7:30- and 1:30-o`clock positions.
Discussion: The described symptomes can be explained by a misinnervation of the right m. sphincter pupillae. Considering the early damage, transsynaptic degeneration secondary to a lesion of the 2nd sympathetic neuron is possible.
We assume a vagal origin of the misinnervation, because the segmental pupillary dilatation occured solely in combination with drinking, i.e. if oesophageal peristaltic was required over a longer period of time to transport a larger volume. The synkinesis of the pupil could not be elicited by the voluntary part of the swollowing act which requires activity of the hypoglossal and glossopharyngeal nerves. Anyway, some axons of the third neuron must be intact, because the synkinesis requires an adrenergic innervation of the iris dilator muscle.
As an alternative to synaptic transfer of neuronal activity, ephaptic transmission (neuronal cross-talk) has to be discussed.
Augenklinik für Schielbehandlung und Neuroophthalmologie der Justus-Liebig-Universität Gießen, Friedrichstr. 18, 35385 Gießen