Pharmacologic testing can help target subsequent imaging for Horner's syndrome, but can it delay a full evaluation? Two ophthalmologists engage in a friendly debate.
The presence of Horner's syndrome, which has three presenting signs-ptosis, pupillary mio-sis, and anhydrosis, which does not occur in all cases-is caused by interruption of the lengthy sympathetic pathway, said Peter A. Quiros, MD, assistant professor of ophthalmology, Doheny Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles. He was assigned to argue the position in favor of pharmacologic testing in the debate.
Pharmacologic testing using cocaine or hydroxyamphetamine drops can serve to direct imaging as necessary, he said.
Cocaine drops, which inhibit the reuptake of norepinephrine at the nerve terminal, result in pupil dilation in the normal pupil but do not produce a reaction in an eye with Horner's syndrome, he said, adding that these drops often are used to confirm subtle cases.
"The drawback to using the cocaine test is that its effects can last for about 24 hours, so you will have to have that patient come back if you need to do anything further in terms of drop testing," Dr. Quiros said.
Hydroxyamphetamine drops force the release of norepinephrine from the nerve terminal and can be helpful in differentiating a post-ganglionic, third-order lesion from a pre-ganglionic, second-order lesion or a central, first-order lesion, he continued.
"A normal pupil will dilate, and a third-order [lesion] pupil will not dilate," Dr. Quiros said. "A positive hydroxyamphetamine test means you will end up with very uneven pupils."
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 explained.
If the hydroxyamphetamine test is negative for a post-ganglionic Horner's syndrome (third-order), then magnetic resonance imaging (MRI) of the brain stem can confirm the presence of central lesions, he continued. If brain stem signs are not present, then computed tomography or MRI of the neck and chest should be ordered to evaluate the second-order neuron.
When the hydroxyamphetamine test is positive for Horner's syndrome, Dr. Quiros added, "if you have a good history of trauma, you can pretty much do nothing because it's due to the trauma. If, however, you have no history of trauma, then you should get MRI and a magnetic resonance angiogram of the head and neck.
"By targeting your MRI to pre-and post-ganglionic locales, you can improve the sensitivity of lesion detection, and this will help you pick up more subtle lesions such as a carotid dissection, a small tumor, or even spinal cord lesions," he added.