PERIOSTEAL GANGLIA - CT AND MR-IMAGING FEATURES

The imaging features of four cases of periosteal ganglia were studied. Three lesions were located over the proximal shaft of the tibia, in p roximity to the pes anserinus. The fourth lesion involved the distal s haft of the ulna. Three lesions had different degrees of external cort ical erosion, scalloping, and thick spicules of periosteal bone on pla in radiographs. The bone adjacent to the fourth lesion was not involve d. Computed tomography (CT) showed these lesions to be sharply defined soft-tissue masses abutting the periosteum. All of the lesions had th e same attenuation as fluid. Magnetic resonance (MR) imaging revealed the ganglia to be sharply defined masses that were isointense compared with neighboring muscles on T1-weighted images. There was markedly in creased signal intensity compared with that of fat on T2-weighted imag es. The signal intensity on both types of images was homogeneous. The MR imaging features were consistent with the fluid nature of the lesio ns. Under the appropriate clinical circumstances, the MR imaging and C T features of periosteal ganglia are diagnostic.