The analysis of CSF may further aid in determining the mechanism of a CNS disorder (especially inflammation). The technique of collection is simple and safe with practice. Analysis of CSF requires minimal special equipment. Cell counts and identification should be performed within 30 min after collection, because cells begin to degenerate after that time. Several techniques are available to concentrate or stabilize cells so that a differential cell count can be obtained at a later time.
CSF is collected from the cerebellomedullary cistern or the subarachnoid space in the lumbar region. An increase in protein is often associated with encephalitis, meningitis, neoplasia, or spinal cord compression. Cellular content increases most frequently with inflammation of the CNS. Neutrophils are indicative of bacterial infections, subarachnoid hemorrhage (RBCs are also present), brain abscess or a steroid-responsive suppurative meningoencephalitis, or in some cases, necrosis within a tumor. Increased numbers of lymphocytes, monocytes, and neutrophils are most common in steroid-responsive nonsuppurative meningoencephalitis, meningoencephalitis of unknown etiology (MUE) , fungal infections, toxoplasmosis, and neosporosis. Cultures of CSF may demonstrate the causative agent in bacterial and fungal infections. Paired serum and CSF immunoassays for canine distemper virus, cryptococcosis, toxoplasmosis, neosporosis, Rocky Mountain spotted fever, ehrlichiosis, and borreliosis can assist in diagnosis of these infections.