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DISEASES OF THE SPINE
CEREBROSPINAL FLUID ANALYSIS Cheryl L. Chrisman, DVM, MS, EdS
Once the history of a dog or cat with neurologic dysfunction can be accurately assessed, the neurologic examination competently performed and interpreted, and a logical differential diagnosis list developed, veterinary practitioners are ready to add the analysis of cerebrospinal fluid (CSF) to their diagnostic repertoire. Accurate information from the signalment, history, and physical and neurologic examinations and other clinicopathologic and ancillary diagnostic tests is essential for the proper interpretation of CSF changes in the context of an individual case. The use of information from the CSF analysis can enable practitioners to improve their diagnostic capabilities for neurologic disorders, especially those produced by inflammatory, degenerative, and neoplastic mechanisms of disease. With the advent of metrizimide, iopamidol, and iohexol, veterinary practitioners can safely perform myelography on dogs and cats to evaluate compressive and expansive spinal cord lesions better. 76 CSF analysis should be performed before myelography in most cases. When the dog or cat is anesthetized for plain radiographs of the vertebral column and if a myelogram is deemed necessary, a CSF collection and initial cell count can be performed in 5 to 10 minutes. If meningitis or meningomyelitis is suspected from the initial CSF cell count, the myelogram should not be performed in many cases. Metrizimide~ iopamidol, and to a lesser extent, iohexol, produce transient aseptic meningitis in normal dogs. 12, 63, 71, 77 Most of the dogs and cats with inflammatory spinal cord disease will have a normal myelogram, and their neurologic signs may be transiently worse after the myelogram.~ The routine techniques for analysis of CSF are simple and can be From the Department of Small Animal Clinical Sciences, University of Florida College of Veterinary Medicine, Gainesville, Florida
VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 22 • NUMBER 4 • JULY 1992
performed without expensive equipment. Prior training of a hospital technician is necessary because analysis must be performed within 30 minutes of collection for accurate cell counts and cytology. Often this must be performed in each practice setting. In-depth descriptions of CSF analysis techniques are described elsewhere. 13, 15, 17,37,41,46 Parameters evaluated on CSF and normal values are found in Table 1. The focus of this article is the interpretation of CSF analysis results to help differentiate mechanisms of central nervous system (CNS) disorders in general and in some cases to diagnose specific diseases. Both interpretation of routine and special CSF parameters are discussed as well as some directions for future studies.
Table 1. OVERVIEW OF CEREBROSPINAL FLUID ANALYSIS PARAMETERS EVALUATED AND NORMAL FINDINGS
Pressure Color Clarity Specific gravity Refractive index