Evaluation of Horner Syndrome in the MRI Era

To identify the etiologies of adult Horner syndrome (HS) in the MRI era using a targeted evaluation approach and to assess the value and yield of targeted imaging. A retrospective chart review was performed of 200 adult outpatients with HS, confirmed with cocaine eyedrop testing. Patients were divided into subgroups based on the presence or absence of symptoms and those who did or did not receive additional testing with hydroxyamphetamine drops. Imaging was obtained based on pharmacologic localization and/or clinical evaluation. The etiology of HS and the yield of imaging were determined in all subgroups. Imaging showed causative lesions in 24 of 179 (12.84%) imaged patients with HS, and 13 (69.0%) were determined 'idiopathic.' Of the patients who underwent testing with hydroxyamphetamine drops (132 patients), 86 had a postganglionic localization with an imaging yield of 8.1%, and 46 had preganglionic cause with an imaging yield of 21.7%. Fifty-three patients (26.5%) never noticed ptosis/anisocoria before examination, and the imaging yield in this subgroup was 2.8%. Eighteen of the 200 patients (9.0%) had serious pathology, including carotid artery dissection, brain, or neck mass, and 6 of these (31.6%) had acute symptoms and/or pain. HS is most often idiopathic with serious pathology being relatively infrequent. When determining etiology, the absence of symptoms is not predictive of the pathology. However, acute onset of symptoms and/or pain are possible indicators for serious pathology. Localizing the lesion using hydroxyamphetamine drops whenever obtainable and available is still an efficient way to target imaging evaluation.