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This 6-year-old boy was born with a closed right eye that opened halfway by 5 months of age. His parents noticed that he had decreased sweating over the right side of his face and forehead above the hairline. He also had pupil asymmetry, with miosis of the right eye. At age 14 months, the ptosis had almost completely resolved, but the child was noted to have heterochromia of the irises (the right iris being much lighter). He was referred to a pediatric ophthalmologist who diagnosed idiopathic congenital right-sided Horner syndrome.
Horner syndrome is characterized by enophthalmos, narrowing of the palpebral fissure, anisocoria, and constriction of the pupil and by certain anomalies in vasomotor and sudorific activity of the neck and face. When Horner syndrome presents in the first year of life, it is usually benign. As in this case, no cause is generally identified. The most common causes include birth trauma and neuroblastoma. Other causes include congenital varicella, ganglioneuroma or neurilemmoma, and vascular lesions of the internal carotid or subclavian artery.
Although numerous researchers, including Bernard, contributed to our understanding of this rare nerve disorder, Horner provided the first scientifically supported explanation for the syndrome.1 A deficiency of sympathetic activity caused by a lesion anywhere along the oculosympathetic pathway from the hypothalamus to the orbit is responsible for the disorder. Horner syndrome is often associated with heterochromia iridis, which results from a unilateral lack of sympathetic stimulation; this interferes with melanin pigmentation of the melanocytes in the iris through disruptions in the pathways of tyrosinase induction.2
How aggressive the workup should be to investigate for a cause is a topic of much debate. In one study, no cause was identified in 16 (70%) of 23 patients who presented with Horner syndrome in the first year of life; however, the authors recommend that these infants be examined for cervical and abdominal masses and for cranial nerve pathology.3 Measurement of the urinary vanillylmandelic acid level and ongoing follow-up should identify any cases associated with neuroblastoma, without the need for MRI or CT scanning of the neck or chest.
For this child, neurosurgery consultation and MRI of the chest and neck to rule out tumors was provided at the time of diagnosis, and he was scheduled to follow-up with the pediatric ophthalmologist. The child has remained healthy otherwise. ■
1. Chaves C, Estol C, Esnaola MM, et al. Spontaneousintracranial internal carotid artery dissection:report of 10 patients. Arch Neurol. 2002;59:977-981.