Clinicians debate pros, cons of pharmacologic testing for Horner's syndrome

Should pharmacologic testing be performed before imaging with suspected Horner's syndrome? That topic was the focus of a friendly debate held during a symposium on current and emerging controversies in neuro-ophthalmology.

Should pharmacologic testing be performed before imaging with suspected Horner's syndrome? That topic was the focus of a friendly debate held during a symposium on current and emerging controversies in neuro-ophthalmology.

Many clinicians take a "shot-gun approach" in their efforts to diagnose Horner's syndrome, skipping pharmacologic testing and instead ordering imaging of the entire Horner's pathway for fear of missing something, said Peter A. Quiros, MD, assistant professor of ophthalmology, Doheny Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, United States. He took the position in favor of pharmacologic testing in the debate.

This approach is not in a patient's best interest, however, Dr. Quiros said.

"Even the most experienced film reader can often miss a lesion when [his or her] attention is spread out over too great an area," he said. Images can be misleading, too, he said.

Pharmacologic testing using cocaine or hydroxyamphetamine drops can serve to direct imaging as necessary, Dr. Quiros said, adding that because drop testing is less expensive than imaging and could reduce the amount of imaging needed, its use will reduce imaging-related costs associated with testing,

"By targeting your MRI scans to pre- and postglanglionic locales, you can improve the sensitivity of lesion detection, and this will help you to pick up more subtle things like a carotid dissection, small tumor, or even spinal cord lesions," he said.

The overall false negative rate with pharmacologic testing is 2% to 3%, Dr. Quiros said. Central orders comprise 3% of Horner's cases, and they are related to stroke; pregranglionic Horner's make up about 41% of cases and usually are related to neoplasms; and the overwhelming percentage of cases are postganglionic, and lesions in about 80% of these cases are benign, he added.

The results of pharmacologic testing and history will help determine whether and how to proceed with imaging, as well as the frequency of follow-up, Dr. Quiros said.

Undertaking pharmacologic testing before imaging may delay the full evaluation of Horner's syndrome, however, countered Lynn K. Gordon, MD, PhD, associate professor, Jules Stein Eye Institute, University of California, Los Angeles, United States. She took the position in favor of imaging for the debate.

"Cocaine is the most commonly used test to identify whether or not a subtle Horner's is actually a Horner's," she said, but "we can only do the cocaine test if there was no antecedent topical anesthetic."

Otherwise, Dr. Gordon added, a second office visit will be required for a confirmatory test.

Another delay is the 24 hours needed between dilation and localization, she said.

In the time needed to accommodate the multiple visits necessary for pharmacologic testing, "there might have been something very important that we're missing," Dr. Gordon said. "Maybe waiting and waiting and waiting, we're gong to wind up getting into trouble, as opposed to immediately imaging."Because of the amount of waiting required, increased patient anxiety can be associated with drop testing, she said.

"Do we waste time and heighten anxiety by pharmacologic testing?" Dr. Gordon asked.

Two other issues with pharmacologic testing, she added, are that it is "almost impossible to wrestle cocaine out of the pharmacist" and the fact that remnants of testing agents will show up in patients' urine, so patients subject to random drug testing at their workplaces will have to provide an explanation to their employers if an agent appears in their drug-test results.

"Is pharmacologic testing always correct? We know that it's not. Are postganglionic Horner's always benign? We know that they're not. And in these days of neuro-imaging, can we afford to be wrong, and can we afford to delay?" Dr. Gordon concluded.

Wrapping up the debate, Carlos Filipe C.C. Chicani, MD, of the Federal University of São Paulo, Brazil, said that treatment must be individualized.

"Medicine often has rules, but [there are] no absolutes," he added.

History is key, he said, and the patient has a choice of whether to pursue pharmacologic testing, especially in the United States.