Background: Cerebrospinal fluid (CSF) analysis aids in categorizing underlying disease processes in patients with neurologic disease. Convention suggests that CSF should be collected caudal to the lesion. However, little evidence exists to justify this assertion. Hypothesis/Objectives: Evaluate the clinicopathologic differences between CSF collected from the cerebellomedullary (CM) and lumbar cisterns in dogs presented for evaluation of neurologic disease. Animals: Fifty-one client-owned dogs undergoing magnetic resonance imaging (MRI) and CSF collection for investigation of neurologic disease. Methods: Cerebrospinal fluid was prospectively collected from the CM and lumbar cisterns in all patients. The total protein (TP) concentration, red blood cell (RBC) count, and total nucleated cell count (TNCC) were analyzed within 30 minutes of collection. Results and cytology findings were interpreted by a single pathologist. Results: Fifty-one paired samples were collected. The TNCC (P <.001), RBC (P <.001), and TP (P <.001) were different between collection sites. When grouped by neurolocalization, TP (intracranial, P <.001; cervical, P <.001; thoracolumbar, P <.001) and RBC (intracranial, P <.001; cervical, P ≤.002; thoracolumbar, P =.006) counts were significantly different. The TNCC was significantly different in the cervical (P =.04) and thoracolumbar localizations (P =.004) but not for intracranial (P =.30) localizations. The pathologist's interpretation differed between sites in 66.7% of the cases (34/51). Conclusions: In dogs with lesions that neurolocalized to the brain or cervical spinal cord, there may be clinical benefit in collecting fluid from both the CM and lumbar cisterns. In dogs with thoracolumbar myelopathy, CSF collected from the CM cistern may not be representative of the underlying disease process.
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