New Method for Collecting Equine Cerebrospinal Fluid Samples

New Method for Collecting Equine Cerebrospinal Fluid Samples

"The hope of this procedure is to provide horse owners and veterinarians with a rapid and safe method to collect CSF in horses with neurologic signs," Pease explained.

Photo: Anthony Pease, DVM, MS, Dipl. ACVR

One of the most important tests performed in horses with neurologic disease, such as equine protozoal myeloencephalitis (EPM), is a cerebrospinal fluid (CSF) tap. Unfortunately, many owners and some veterinarians are not particularly comfortable with some of the challenges that accompany this technique, thereby limiting its practical use. But veterinarians at Michigan State University (MSU) have recently developed an alternative technique to make collecting a CSF sample more convenient for all involved.

"The two most common methods for collecting CSF samples from horses is either at the base of the spine near the tailhead or from the base of the skull," explained Anthony Pease, DVM, MS, Dipl. ACVR, assistant professor of radiology and section chief of diagnostic imaging at MSU's College of Veterinary Medicine.

The problem with the former technique is the probability that blood will contaminate the CSF sample. The problem with the latter technique is that the horse needs to be anesthetized and laid down to retrieve the sample. While not a major issue for healthy horses, neurologic horses recovering from anesthesia can be extremely dangerous to themselves and others.

Because CSF testing is important in diagnosing EPM (or ruling it out in horses suffering from a different neurologic disease), Pease and colleagues devised an ultrasound-guided method of collecting CSF.

"We sedated 17 horses and inserted a needle through the skin on the side of the neck, just behind the left ear," described Pease. "The needle was advanced into the spinal canal between the first and second cervical vertebrae using ultrasound guidance to obtain a sample without damaging the spinal cord.

"This procedure uses equipment available to most veterinarians and, because we approached the spinal canal from the side rather than the top, if the horse moves its head, the needle won't inadvertently damage the spinal cord or injure the horse."

Pease performed the procedure 13 times (using 11 healthy and two neurologic horses) in the study, all of which were successful in collecting usable CSF samples.

"The last procedure performed on a neurologic horse had (blood contamination of) four red blood cells per microliter--well below any level considered to be detrimental to EPM testing," relayed Pease, who has since performed five additional successful procedures.

Further, no procedural-related complications occurred, and the total time to acquire the sample was less than two minutes per sample.

Although Pease first used healthy horses to determine if the procedure could be performed, he is now performing the procedure in more neurologic cases: "The hope of this procedure is to provide horse owners and veterinarians with a rapid and safe method to collect CSF in horses with neurologic signs, especially in cases where lumbar centesis cannot be performed."

The study, "Ultrasound-guided cervical centesis to obtain cerebrospinal fluid in the standing horse," scheduled to be published in an upcoming edition of Veterinary Radiology & Ultrasound. The abstract is available on PubMed.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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