Magnetic Resonance Imaging Features of Spontaneous Subdural Hematoma Secondary to Necrotizing Encephalitis in a Dog

A 4‐year‐old castrated male Pomeranian dog with a 2‐year history of necrotizing encephalitis (NE) presented for acute neurological deterioration without trauma. Magnetic resonance imaging (MRI) revealed a broad crescent‐shaped lesion with mixed signal intensities on T1‐ and T2‐weighted images, hypointense areas on T2* images, contrast enhancement in the outer membrane, and a mass‐like lesion with fluid–fluid layers. The lesion was diagnosed as a chronic subdural hematoma secondary to spontaneous hemorrhage in a dog with NE. A direct causal relationship remains uncertain; however, NE could have contributed to the increased vulnerability of bridging veins. Serial MRI evaluations revealed progression of the lesion. This is the first report describing the MRI features of chronic subdural hematoma in a dog with NE.