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Acquired Segmental Iris Dilator Muscle Synkinesis Due to Deglutition
Arch Ophthalmol. 1998;116:248-249.
Congenital ocular "misdirection dyskinesis" typically involves multiple cranial nerves. Acquired peripheral misdirection usually occurs in the same nerve; less frequently, more than one nerve are involved. We describe an unusual synkinesis of the iris dilator muscle due to deglutition, presumably caused by posttraumatic aberrant outgrowth of vagal nerve fibers to the cervical sympathetic chain.
Report of a Case
We describe an unusual synkinesis in a 10-year-old boy. On the sixth day of life a neuroblastoma was removed from the right side of his neck. A right-sided Horner syndrome and paresis of the recurrent laryngeal nerve occurred postoperatively, as well as a flacidity of the right soft palate, a deviation of the tongue to the right side, and an atony of the esophagus and the stomach that regressed within 2 weeks. When the child was 2 years old, the parents recognized that his right pupil became distorted when he was drinking and afterward regained its round shape within a few seconds. The iris appeared to tighten radially at the 7:30- and 1:30-o'clock positions. When we examined the patient at 10 years of age we confirmed these findings. A right-sided ptosis, facial vasodysregulation (flushed left side of the face, pale right side of the face after exercise), and anhidrosis (from forehead to larynx region; iodine starch reaction) were present, but not iris heterochromia. The right pupil dilated poorly on instillation of 4% cocaine hydrochloride and 5% pholedrine formate (equivalent to 1% hydroxyamphetamine hydrobromide; Figure 1).
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Figure 1. Right-sided Horner syndrome, without swallowing (A), with pupillary distortion due to swallowing (B), 30 minutes after instilling 5% pholedrine formate in both eyes (an identical anisocoria was present after instilling 4% cocaine hydrochloride in both eyes) (C), and 15 minutes after instilling 5% phenylephrine hydrochloride in both eyes (D). Pupillary diameter expressed in millimeters for the right eye/left eye is as follows: (A) 4.5/5.2, (B) 7.3x4.1/5.2, (C) 4.5/7.4, and (D) 7.4/7.4.
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Comment
The findings indicated a lesion of the postganglionic (third order) sympathetic neuron, either primary or by transsynaptic degeneration. Some axons of the postganglionic neuron must have been intact, because the synkinesis requires adrenergic innervation of the iris dilator muscle. There is a close topographic relationship among the sympathetic superior cervical ganglion, the inferior ganglion of the vagus nerve, the hypoglossal nerve, and the glossopharyngeal nerve.1 The esophagus and stomach atony and the recurrent laryngeal nerve paresis indicate an injury to vagal fibers. The swallowing disorder, the flacidity of the soft palate, and the remaining deviation of the extended tongue indicate involvement of hypoglossal and glossopharyngeal fibers. We assume that the origin of the misinnervation was vagal, because the pupillary distortion could be elicited only by drinking, when permanent, significant esophageal peristalsis is required; but not by lower swallowing frequency (eating) and low volume load (saliva) at the same swallowing frequency as when the child was drinking. That is, the pupillary distortion was elicited mainly by the voluntary sequence of the swallowing act, which requires activity of the hypoglossal and glossopharyngeal nerves.
Descending vagal fibers in the neck are adjacent to the fibers of the ascending sympathetic chain (Figure 2). If these fibers are injured at the same time, aberrant vagal sprouts can grow into the cervical sympathetic path.2 Since the vagal sprouts are cholinergic, some of them may be lost owing to pharmacological incompatibility. But, if they reach sympathetic ganglion cells in the superior cervical ganglion, they may make a permanent—albeit inappropriate—cholinergic connection. If these sprouting fibers are to survive, they must still be connected to their original vagal ganglion cells.
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Figure 2. Topographic relationship of the 7th, 9th, 10th, and 12th cranial nerves, the inferior ganglion of the 10th nerve (IGV), and the superior cervical ganglion (SCG) in the retropharyngeal space.3 IC and EC indicate internal and external carotid arteries, respectively.
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AUTHOR INFORMATION
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Brigitte I. Boehme, MD;
Michael H. Graef, MD
Giessen Germany
Reprints: Michael H. Graef, MD, University of Giessen, Department of Strabismology and Neuroophthalmology, Friedrichstrasse 18, D-35385 Giessen, Germany.
REFERENCES
1. Miller NR. Walsh and Hoyth's Clinical Neuro-ophthalmology. Baltimore, Md: Williams & Wilkins; 1985;2:425.
2. Loewenfeld IE. The Pupil: Anatomy, Physiology, and Clinical Applications. Detroit, Mich: Wayne State University Press; 1993:520-627.
3. Platzer W. Taschenatlas der Anatomie. Stuttgart, Germany: Georg Thieme Verlag; 1979;1:343.
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