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Show PHOTO ESSAY False Negative Hydroxyamphetamine Test In Horner Syndrome Caused by Acute Internal Carotid Artery Dissection Mark L. Moster, MD, David Galiani, MD, and William Garfinkle, MD FIG. 1. Axial T2 magnetic resonance imaging through the skull shows hemorrhage ( white ring) in the wall of the left internal carotid artery ( arrow). Abstract: A patient with Homer syndrome from internal carotid artery dissection initially had a false negative hydroxyamphetamine test. Two months later, the ophthalmic Department of Neurosensory Sciences ( MLM, DG), and Radiology ( WG), Albert Einstein Medical Center, Philadelphia, Pennsylvania, Department of Neurology ( MLM), Thomas Jefferson University School of Medicine, Philadelphia, Pennsylvania Address correspondence to Mark L. Moster, MD, Chairman, Department of Neurosensory Sciences, Albert Einstein Medical Center, Klein Professional Building, Suite 300, 5501 Old York Road, Philadelphia, PA 19141, USA; E- mail: mmoster@ aol. com signs had disappeared but the hydroxyamphetamine test was positive. This case illustrates that hydroxyamphetamine testing may be falsely negative in acute Horner syndrome because norepinephrine stores in oculosympathetic postganglionic terminals have not yet been depleted. However, the hydroxyamphetamine test may be positive even after the ophthalmic signs of Horner syndrome have disappeared. ( JNeuro- Ophthalmol 2003; 23: 22- 23) A 43- year- old man felt dizzy after a vigorous morning exercise workout. He noticed transient blurring of vision that Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 22 J Neuro- Ophthalmol, Vol. 23, No. 1, 2003 PHOTO ESSAY JNeuro- Ophthalmol, Vol. 23, No. 1, 2003 FIG. 2. Hydroxyamphetamine testing. There is no anisocoria or ptosis at baseline ( left). After topical instillation of hy-droxyamphetamine 1 % in OU ( right), there is an anisocoria of 2.5 mm and slight left upper lid ptosis has appeared. Findings are consistent with a postganglionic Horner syndrome. he could not further characterize, and mild left suboccipital and eye pain. Later that day, colleagues noted a droopy eyelid and a small left pupil. The following day, he underwent chiropractic manipulation. Two days later, neuro-ophthalmologic consultation revealed normal afferent visual function, ocular motility, and fundus examination. Left upper lid ptosis of 2 mm was present. The right pupil measured 3.25 mm in light and 4.5 mm in darkness; the left pupil measured 2.5 mm in light and 3 mm in darkness. There were no other focal neurologic deficits. Following topical instillation of hydroxyamphetamine 1% in both eyes, the pupils dilated symmetrically to 8 mm in darkness. Given the negative hydroxyamphetamine test, cervical internal carotid artery ( ICA) dissection was considered unlikely. But the history was compelling and magnetic resonance imaging ( MRI)/ magnetic resonance angiography ( MRA) was performed, revealing an ICA dissection ( Fig. 1). The patient was anticoagulated with warfarin. Two months later, the Horner syndrome was no longer present. However, following topical instillation of hydroxyamphetamine 1 %, he had 2.5 mm of anisocoria in darkness ( Fig. 2). Within 6 months after onset, the MRI/ MRA had returned to normal and warfarin was discontinued. Horner syndrome results from a lesion involving one of the three neurons of the sympathetic pathway. Topical instillation of hydroxyamphetamine is used to determine whether the postganglionic neuron is the site of damage ( 1). With postganglionic lesions, as occur in ICA dissections, the pupil will dilate poorly following topical instillation of hydroxyamphetamine 1%. False negative hydroxyamphetamine tests can occur within 1 week of onset of ophthalmic manifestations ( 2). In addition, ICA dissection can result in a transient Horner syndrome and a positive hydroxyamphetamine test after the resolution of manifestations ( 3). Our patient had a Horner syndrome caused by ICA dissection with a false negative hydroxyamphetamine test at presentation and a positive hydroxyamphetamine test after resolution of the ophthalmic findings. This case demonstrates two important clinical points. First, hydroxyamphetamine testing of Horner syndrome early in the course of ICA dissection may be negative and thereby falsely reassure the clinician that there is a normal postganglionic sympathetic neuron. Second, pharmacologic testing may help diagnose a postganglionic Horner syndrome even after ophthalmic manifestations have resolved. Hydroxyamphetamine releases norepinephrine stores from postganglionic nerve endings, producing mydriasis. In postganglionic Horner syndrome, norepinephrine stores are diminished, with decreased mydriatic response. However, it may take a week for the stores to be depleted ( 2). With a history consistent with ICA dissection, one must not be misled by a negative hydroxyamphetamine test, particularly because of the high risk of stroke in such patients ( 4). In ICA dissection, Horner syndrome may be transient or completely absent, yet hydroxyamphetamine testing may confirm the diagnosis, as in our patient and as reported by Leira et al ( 3). Therefore, with a history consistent with ICA dissection, hydroxyamphetamine testing should be performed even if no Horner syndrome is seen on examination. REFERENCES Cremer SA, Thompson HS, Digre KB, et al. Hydroxyamphetamine mydriasis in Horner's syndrome. Am J Ophthalmol 1990; 110: 71- 6. Donahue SP, Lavin PJ, Digre KB. False- negative hydroxyamphetamine ( Paredrine) test in acute Horner's syndrome. Am J Ophthalmol 1996; 122: 900- 1. Leira EC, Bendixen BH, Kardon RH, et al. Brief, transient Horner's syndrome can be the hallmark of a carotid artery dissection. Neurology 1998; 50: 289- 90. Biousse V, Touboul PJ, D'Aglejan- Chatillon J, et al. Ophthalmologic manifestations of internal carotid artery dissection. Am J Ophthalmol 1998; 126: 565- 77. Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 23 |
