Unusual intramedullary vascular lesion: Report of two cases

OBJECTIVE AND IMPORTANCE: Spinal arteriovenous malformations have been divided by location into dural (Type I), intramedullary glomus (Type II), juvenile (Type III), and perimedullary direct arteriovenous fistulae (Type IV). We report two cases of an unusual intramedullary proliferation of hyalinized capillaries that do not fit into any of these categories. CLINICAL PRESENTATION: A 27-year-old woman and a 62-year-old man presented with subacute progressive caudal myelopathy. Magnetic resonance imaging revealed focal spinal cord enlargement, high signal on T2-weighted images, and patchy enhancement with gadolinium consistent with tumor. No serpentine flow voids were visualized on the surface of the spinal cord. Spinal angiography revealed nothing abnormal. No abnormal vasculature was grossly visible on open biopsy. Histological examination of the tissue specimens revealed a proliferation of capillary-sized vessels with varying degrees of vascular wall changes ranging from endothelial hyperplasia to concentric hyalinization, suggesting ongoing evolution of the lesion. Surrounding neural tissue demonstrated ischemic changes characterized by myelin and axonal loss and astrocytosis but no necrosis. INTERVENTION: Patients were treated with chronic anticoagulation, which seemed to slow, but not halt, symptomatic disease progression. CONCLUSION: Although the pathological substrate seems to be an acquired intramedullary vascular lesion characterized primarily by capillary proliferation, the cause of this lesion is unknown. This disease differs from Foix-Alajouanine syndrome and subacute necrotizing myelopathy by an absence of abnormal surface vessels and a lack of intramedullary necrosis. The histological findings are reminiscent of the process that occurs in the kidney and various end organs from long-standing mild to moderate elevations in blood pressure or chronic diabetes. Tissue ischemia may result from luminal obstruction by severe hyalinization and thrombosis. Because the natural history of this disease is unknown, it is unclear whether anticoagulation slowed disease progression.