Case Report: Spinal arteriovenous fistula and vertebral angiomatosis in a cat-the role of imaging within the vascular malformation spectrum.

Spinal arteriovenous fistula (SAVF) and vertebral angiomatosis are rare vascular malformations reported in cats, and their clinical and imaging manifestations may partially overlap. This report describes a T11 vertebral lesion in a 2-year-old spayed female cat that presented with non-ambulatory paraparesis and difficulty in urination and defecation. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed an expansile osseous lesion centered on the left-sided lamina, pedicle, and vertebral body of T11, resulting in extradural spinal cord compression. Notably, the dilated venous structures or obvious arteriovenous shunts commonly described in previously reported feline SAVF cases were not identified on imaging. Following surgical decompression, two separate histopathological evaluations yielded different diagnoses: arteriovenous fistula with osseous proliferation and bone remodeling, and capillary-type vertebral angiomatosis. However, these findings may not be mutually exclusive; rather, they can be interpreted as emphasizing different aspects within a vascular malformation spectrum in which the two entities share a common vascular pathophysiology. This case demonstrates that a feline spinal vascular lesion presenting with vertebral osseous proliferation may show imaging features consistent with both vertebral angiomatosis and SAVF. It also suggests that imaging plays a crucial role in evaluating the predominant pathophysiologic mechanism responsible for neurological signs and in guiding therapeutic decision-making.