Canine cerebrospinal fluid total nucleated cell counts and cytology associations with the prevalence of magnetic resonance imaging abnormalities

INTRODUCTION: The combination of cerebrospinal fluid (CSF) analysis and magnetic resonance imaging (MRI) are often used to investigate intracranial disease in dogs. The aim of this retrospective study was to determine if the total nucleated cell count (TNCC) or cytology findings in abnormal CSF are associated with the prevalence of MRI abnormalities. MATERIALS AND METHODS: For each case, the TNCC was categorized into one of three groups: A (<25×10(6)/L); B (25–100×10(6)/L); and C (>100×10(6)/L). Cytology findings were categorized by the predominant cell type as lymphocytic, monocytoid, neutrophilic, or eosinopilic. MRI descriptions were classified as either normal or abnormal, and abnormal studies were further evaluated for the presence of specific characteristics (multifocal or diffuse disease versus focal disease, positive T2-weighted hyperintensity, positive FLAIR hyperintensity, contrast enhancement, mass effect, and the presence of poorly or well-defined lesion margins). RESULTS: Forty-five dogs met the inclusion criteria and MRI abnormalities were found in 29/45 (64%) dogs. TNCCs were not associated with the prevalence of MRI abnormalities or specific characteristics. Cytology categories were significantly associated with the prevalence of MRI abnormalities (P<0.001). Specifically, monocytoid cytology was 22.8 times more likely to have an abnormal MRI than lymphocytic cytology. CSF cytology was not significantly associated with specific abnormal MRI characteristics. CONCLUSION: There are minimal associations between CSF abnormalities and the prevalence of MRI abnormalities. These results support the continued importance of utilizing both tests when investigating intracranial disease. When CSF analysis must be performed initially, this study has demonstrated that an abnormal CSF with a monocytoid cytology supports the value of performing a brain MRI in dogs with evidence of intracranial neurological disease.