Correlation of MR Imaging Meningeal Enhancement or CSF Flair-Suppression with CSF Analysis in Dogs
To determine if a correlation exists between meningeal enhancement or CSF FLAIR-suppression present on MR imaging and results of CSF analysis, a retrospective assessment of dogs with intracranial signs who had both intracranial MR imaging and CSF analysis were reviewed. Inclusion criteria for cases were the following: clinical signs consistent with an intracranial neurolocalization, a complete MR brain study and CSF analysis. Recorded historical parameters included signalment, duration of clinical signs, medications administered, neuro-localization and diagnosis at time of discharge. MR studies were evaluated by a single radiologist independent of the knowledge of CSF analysis results. The presence of meningeal enhancement on T1 weighted imaging after administration of a paramagnetic contrast agent (gadolinium) and incomplete suppression of the CSF signal in the lateral ventricles on FLAIR sequences was subjectively evaluated. Meningeal enhancement was subjectively graded as absent, mild, moderate or severe. Quantitatively, intensity comparisons were made between 5 points in the lateral ventricles, the temporal muscles and the surrounding air. Both atlanto-occipital and lumbar puncture sites were accepted in the study and analysis included nucleated cell count, protein, glucose, creatinine kinase concentrations, and cytologic description. Patients with spinal causes of CSF alterations on lumbar puncture or marked blood contamination in their CSF tap (>2000 RBC/ul) were excluded from the study.
Twenty-five of 78 (32%) dogs had detectable contrast enhancement of the meninges. 3/3 dogs with severe enhancement and 11/12 dogs with moderate enhancement had abnormal CSF protein and/or cell counts, while 6/10 patients with mild enhancement had similar CSF changes. Of the remaining 53 dogs without detectable contrast enhancement of the meninges, 26 (49%) had abnormalities on CSF analysis.
Thirty-seven of 78 dogs (47%) had incomplete suppression of CSF signal on FLAIR studies. Of these 37 dogs, however, there was no obvious correlation between incomplete FLAIR suppression and CSF analysis.
This initial retrospective evaluation suggests that moderate to marked meningeal enhancement seen with MR imaging is commonly associated with CSF alterations, however, mild enhancement (subjectively identified) is incompletely associated with CSF alterations in naturally affected animals with intracranial signs. Also, importantly, not all dogs with CSF abnormalities have meningeal enhancement present on MR imaging as close to 50% of dogs in this study had no meningeal enhancement in the presence of CSF abnormalities.