Case Report: Presumptive subdural hemorrhage as a rare neurological manifestation of primary immune-mediated thrombocytopenia in a dog

A 10-year-old female spayed mixed-breed dog was presented with a history of seizures and acute progressive intracranial signs. The neurological examination was consistent with multifocal brain disease. Clinical examination revealed ecchymoses, petechiae, and bilateral retinal hemorrhage. Clinicopathological evaluation identified severe thrombocytopenia [a platelet count of 9 × 103/μL without clumps on manual smear evaluation] with an increased mean platelet volume. Coagulation testing (activated partial thromboplastin time and prothrombin time) and fibrinolysis markers (D-dimers, quantitative fibrinogen), infectious disease screening, and thoracic and abdominal imaging were within normal limits, establishing a diagnosis of primary immune-mediated thrombocytopenia (ITP). Magnetic resonance imaging (MRI) of the brain showed minimally expanded, bilateral crescent-shaped, extra-axial fluid accumulations overlying both cerebral hemispheres. Based on T1-weighted and T2-weighted hyperintensities and peripheral susceptibility artifact on T2*-weighted gradient-recalled echo (GRE) imaging, a late subacute subdural intracranial hemorrhage was diagnosed. Despite initial uneventful anesthesia and recovery, the dog experienced acute neurological deterioration and suffered cardiopulmonary arrest, suspected due to ongoing hemorrhage or brain herniation. This report describes a rare neurological manifestation of primary ITP in a dog. While canine ITP generally carries a favorable prognosis, life-threatening secondary intracranial hemorrhage can occur. Primary ITP should be considered as a differential diagnosis for an acute, progressive neurological presentation until a normal platelet count is confirmed.