MR-IMAGING OF BENIGN PERIPHERAL-NERVE SHEATH TUMORS

In a retrospective, nonblind review of MR imaging of 15 benign periphe ral nerve neoplasms in 13 patients, the signal pattern of the tumors ( including contrast-enhanced images) and stage were assessed. One lesio n was subcutaneous, 9 intramuscular, 2 intermuscular and 3 extracompar tmental. One lesion was located to the trunk, 5 to the upper extremity and 9 to the lower. The signal on T1-weighted spin-echo images was ho mogeneous isointense compared to adjacent muscle in 11 lesions and in 2 slightly hyper- and in 2 slightly hypointense. T2-weighted spin-echo images, acquired in all but one examination, showed a hyperintense si gnal, homogeneous in 8 and centrally inhomogeneous in 6 lesions. Postc ontrast T1-weighted images of 11 lesions showed a strong signal, with an inhomogeneous enhancement in the center of the lesion similar to th at obtained in T2-weighted images. In 2 cases there were signal charac teristics indicating bleeding in the tumor. In one lesion both the non enhanced and contrast-enhanced T1-weighted images showed a hypointense signal in the tumor center suggestive of intramuscular myxoma. All le sions were well delineated without reactive edema. In all cases, anato mic tumor location was correctly assessed. Although the findings were not pathognomonic for neurinoma, MR imaging provided valuable informat ion confirming the clinical and cytologic assessments.