Magnetic resonance imaging findings of vascular malformations of the lower extremity.

Vascular malformations are congenital lesions resulting from a defect during embryogenesis. Magnetic resonance imaging (MRI) is a very effective method for demonstrating detailed information regarding involved structures, extent, and flow characteristics of vascular malformations. In previous MRI studies, most of the emphasis is laid on the difference between high- and low-flow lesions, whereas little detailed information is available about the extent of local tissue involvement. These additional characteristics may influence the approach in treating these malformations and improve understanding of the pathogenesis. We retrospectively reviewed MRI scans of 40 patients with vascular malformations of the lower extremity. Thirty-four patients had low-flow lesions, and six had high-flow lesions. Of the low-flow lesions, 23 patients (67.6 percent) had muscle infiltration, with four of the six high-flow lesions having muscle infiltration. Nine of the 11 male patients (81.8 percent) with low-flow lesions had associated muscle infiltration, in comparison with 14 of the 23 female patients (60.9 percent) with low-flow lesions (p = 0.206). Eighty percent of the vascular malformations located on the thigh with muscle involvement had involvement of the anterior muscle group, whereas 86.6 percent of the patients with a vascular malformation located on the leg and with associated muscle involvement had at least the posterior muscle group involved (p = 0.0049). Ten patients (25 percent) of the whole group had bone infiltration. Low-flow lesions often had multifocal lesions (20.6 percent), whereas associated muscle atrophy was visible in 10 low-flow lesions and in two high-flow lesions. In low-flow lesions with muscle infiltration (n = 23), 43 percent (n = 10) had associated surrounding muscle atrophy (p = 0.009). Hypertrophy of the subcutaneous tissue was visible in 11 low-flow patients (32.4 percent). The high amount of muscle and bone involvement in vascular malformations of the lower extremity is emphasized with this study. Of particular interest was the difference in affected muscle groups. The angiosome concept is used to explain this preponderance, and we feel the angiosome concept could also be used when assessing possible intervention. The surrounding muscle atrophy and multifocal nature of these anomalies are further important considerations when assessing the possibility of intervention.