The “Blood Brain Barrier” separates the brain and the spinal cord from the rest of the body. This protects the brain from toxins and infections. For example, when you get the flu – or eat a bad oyster – you suffer from general body illness but your brain remains unaffected. While the Blood Brain Barrier safeguards the brain, it also prevents many diagnostic tests from revealing underlying problems in the nervous system. Thus, veterinary neurologists rely heavily on spinal fluid analysis for diagnosis.

What is Spinal Fluid?

The central nervous system is bathed in spinal fluid inside of a sac called the meninges. The spinal fluid provides a certain level of nutrition to the nervous tissues. And, together with the meninges, it creates a fluid barrier to act as a shock absorber. A clear liquid with very few cells, the spinal fluid consists of a low protein content. There are two large pools of fluid in the body: behind the skull (cisterna magna) and in the lower back (lumbar cistern). These pools are where spinal fluid is drawn.

Spinal Fluid Analysis

Veterinarians perform spinal fluid analysis on pets who have undergone anesthesia. Oftentimes, the pet has also just finished an MRI. Depending on the site of fluid acquisition, the veterinary team shaves a spot on the back of the head or over the rump. Though “lumbar punctures” are more common in humans, cisternal taps are more common in dogs. Why? Because they are technically less challenging and less prone to blood contamination.

“Spinal taps” are considered to be very safe procedures. The risk of infection or nervous tissue damage is exceptionally low. In veterinary medicine, we do not recognize the major side effects noted in humans such as:

  • Pain during the procedure: it is nullified as the patients are under anesthesia
  • Long term complications such as migraines: these do not occur in domestic animals

Vets’ primary concern of spinal taps in animals is the potential for brain shifting. This is caused by increased intracranial pressure from a mass and is one of the main reasons an MRI is performed beforehand.

Evaluation of Spinal Fluid

Evaluation of Spinal Fluid
When evaluating spinal fluid, the neurologist analyzes the amount of protein along with the number of and population of white blood cells. Elevated amounts of protein or concentration of white blood cells indicate (non-specifically) that the patient has central nervous system disease, usually inflammation. The types of white blood cells may also suggest a certain type of inflammation. Generally, spinal fluid analysis needs to be used alongside MRI and infectious disease antibody testing (titers) to be of more definitive value. That said, it is considered the mainstay diagnostic for meningitis.


If you have questions about spinal fluid analysis in your pet, please call 704.457.2300 to schedule an appointment with the CARE neurology department. You may also ask your primary vet for a referral.

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