Diagnostic Insights in a Case of Canine Primary Central Nervous System Lymphoma

The case of a 9-year-old neutered male mixed-breed dog with progressive neurological symptoms including altered gait, behaviorial changes, and difficulty swallowing was presented to the Emergency Unit at the University of Veterinary Medicine, Vienna. Due to the clinical findings the patient was initially referred to intensive care for stabilization and further examination, which included a neurologic examination, magnetic resonance imaging of the head, and laboratory tests. A follow-up neurological examination revealed episodes of nystagmus (alternating from horizontal to torsional), slow pupillary light reflexes and reduced oculocephalic reflexes, anisocoria, and ultimately tetra paresis. Magnetic resonance imaging of the brain was unremarkable; however, cerebrospinal fluid analysis showed distinct cytological features of malignancy with high cellularity and pleomorphic cells. According to these results and the poor prognosis, the owners decided against further treatment and chose euthanasia. As part of the subsequent autopsy, histopathological examination revealed lymphoid infiltration primarily of the meninges, thereby confirming the suspected diagnosis of primary central nervous system lymphoma. Thus, unremarkable magnetic resonance imaging findings do not rule out central nervous system lymphoma and should be validated and supplemented by cerebrospinal fluid analysis.