Oreo, a 7-month-old male Boston Terrier dog presented to a neurologist with a history of episodic back pain. MRI was unremarkable. Inflammatory CSF.
CSF cell counts provided by the clinic.
Cytospin preparation of csf collected from the lumbar cistern is submitted.
Fluid preparation is dependent on the sample collected, but in general includes evaluation of concentrated preparations and direct preparations. In the case of cerebrospinal fluid, processing may not be possible if a special cytocentrifuge is not available for use, however abdominal, pleural, pericardial, and synovial fluids are readily accommodated by direct preparations. Direct preparations allow the clinical pathologist to microscopically evaluate how cellular the sample is when cell counts are not available. A variant on the direct preparation that will concentrate cellularity in one location is the â€œline prep,â€ where the sample is prepared similarly to a blood smear, but by stopping abruptly before the feathered edge is reached, creating a line of concentrated fluid.
For best interpretation, always include fluid characteristics such as color, clarity, total protein, and cell counts, when available
Interpretation: Marked eosinophilic pleocytosis.
Clinical Pathology Interpretive Considerations: At first glance, these are not the most convincing eosino-phils. Could they be neutrophils? In fluids, specifically, eosinophils can appear less distinctly granulated and neutrophils may have a pinkish cytoplasmic appearance. A good rule of thumb for interpretation is to find a cell that represents the normal expected appearance. Unfortunately, there was not a perfect neutrophil to be found for comparison in this sample! But overall these appear consistent with eosinophils. All of the granulocytes present are morphologically similar, there is more distinct pink granules in many of them, and the bilobed â€œMickey Mouse earsâ€ nuclear morphology is more commonly present in eosinophils, specifical-ly. Eosinophilic pleocytosis is rare!
Differential diagnoses for eosinophilic pleocytosis in dogs: Broad categories include non-specific acute inflammatory (SRMA, idiopathic), parasitic, allergic, & neoplastic. Specific infectious causes reported in-clude protozoa (toxoplasmosis, neosporosis), Protothecosis, Cryptococcosis, viral (distemper, rabies), cu-terebriasis, as well as aberrant migration of internal parasites.
Reference & Suggested Clinic Resource: De Lorenzi D, Mandara MT. The Central Nervous System. In: Raskin R, Meyer DJ. Canine and Feline Cytology: A Color Atlas and Interpretation Guide. 3rd ed. St. Louis, MO: Elsevier; 2016.