Cerebrospinal fluid (CSF) is fluid found in the subarachnoid space, surrounding the brain and spinal cord. The subarachnoid space is the area between the tough outermost membrane layer (called the dura mater) and the softer innermost layer (the pia mater) that covers the brain and spinal column.
In a procedure called a spinal tap, a needle is inserted into the subarachnoid space and CSF is withdrawn. General anesthesia is administered in order to keep veterinary patients still during the procedure and skilled technicians monitor the patient closely throughout the procedure.
The analysis of cerebrospinal fluid (CSF) has been described as the central nervous system equivalent of the complete blood count (CBC), and the comparison is appropriate. A CSF analysis provides a general index of neurologic health and often provides evidence of the presence of disease.
CSF collection is typically performed to diagnose the cause of abnormal neurological signs such as seizures, altered mental status, and other abnormalities. It is often performed after advanced imaging techniques, such as computed tomography (CT scan) and magnetic resonance imaging (MRI) uncovers some abnormality in the central nervous system. Abnormalities may include inflammation, viral or bacterial infection, bleeding, or suspected tumors.
The CSF is analyzed by determining the morphology (type & appearance) of cells, protein level and overall white (and red) cell count. Abnormal findings may provide clues to the cause of a neurological problem. Further testing of the blood serum and/or CSF by an off-site laboratory may offer additional information to help diagnose the problem.
There are two different types of spinal taps: a cisternal tap and a lumbar tap. To perform a cisternal tap, the back top of the neck is shaved and sterilized. A spinal needle is inserted at the base of the skull, and into the spinal column, penetrating the dura mater and arachnoid membranes to the subarachnoid space. The fluid can be allowed to drip into a collection tube.
A lumbar tap (also called lumbar puncture) is performed in the lower back of a patient. The area is shaved and sterilized, and a spinal needle is inserted. A syringe is attached to the needle and fluid is withdrawn or the fluid is allowed to drip into a collection tube.