Cerebral spinal fluid (CSF) is a fluid that is produced within the ventricles of the brain by the choroid plexus. The CSF flows within and around both the brain and the spinal cord. When there is pathology of the central nervous system, the white blood cell count and/or the protein level of the CSF may be affected. For example, the white blood cell count and protein level are oftentimes elevated when there is inflammation of the central nervous system (CNS) and we call this meningoencephalitis. Certain neoplastic (cancerous) disorders of the CNS exfoliate abnormal cells into the CNS that can be visualized during microscopic review of the CSF. Certain infectious diseases of the CNS, such as fungal disease, can be diagnosed by visualization of fungal spores in the CSF.
CSF may be collected in the dog and cat while under general anesthesia. This procedure is often performed immediately after performing magnetic resonance imaging (MRI) studies of the brain and spinal cord; CSF collection can be done alone as well. CSF is collected from the cerebellar medullary cistern in both dogs and cats but can also be collected from the L5-L6 interarcuate space (L4-L5 in larger dogs).
CSF collection is typically considered a very safe procedure when performed by a trained professional such as a boarded veterinary neurologist. Situations where CSF collection would be dangerous include when the intracranial pressure is increased or when there is a coagulopathy (thrombocytopenia, bleeding disorder, etc.). Physical examination and bloodwork are performed prior to performing a CSF tap in order to ensure that there is no evidence of a coagulopathy, and MRI is typically performed prior to CSF collection in order to rule out signs of elevated intracranial pressure (herniation).
