Myxoid intraneural cysts of external popliteal ischiadic nerve. Report of 2 cases studied with ultrasound, computed tomography and magnetic resonance imaging.

Peripheral neuropathy of the external popliteal ischiadic nerve caused by intraneural cysts is a very rare and peculiar pathological phenomenon compared with diseases associated with extraneural cysts or colliquative phenomena of solid nervous lesions. Two cases of peripheral neuropathy of the external popliteal ischiadic nerve caused by intraneural cysts and evaluated with ultrasound, computed tomography and magnetic resonance are described. The diagnostic efficacy of these imaging modalities is also evaluated with particular reference to MR capability to define the morphology of such lesions and their relationships to the surrounding structures. It is not yet possible to obtain a correct diagnosis about histopathologic features by means of the imaging techniques currently available. Nevertheless, they do provide information about the involvement of the neighboring areas, which are useful indications for possible surgical treatment of the disease.