Perineuriomas

Abstract

Perineurioma is a rare, benign tumor of the peripheral nerve sheath. The tumor grows very slowly over the years and occurs mainly in children and young adults. Motor deficits and muscular atrophy are typical, while sensory deficits are often absent. The high-resolution ultrasound shows a segmentally enlarged and hypoechogenic nerve. Magnetic resonance imaging (MRI) shows long segment enlargement of fascicles within the affected nerves and intense gadolinium enhancement. The identification of enlarged fascicles with intense contrast enhancement may help to distinguish intraneural perineurioma from neurological hypertrophic diseases (hereditary and inflammatory neuropathies) as the most important differential diagnosis. Affected fascicles appear isointense on T1- and hyperintense on T2-weighted images. Perineuriomas can be histologically divided into three subtypes. They are positive for endothelial membrane antigen (EMA) and negative for the Schwann cell marker S-100 in immunohistochemical staining. To diagnose perineuriomas, it is helpful to perform a biopsy of an enlarged fascicle, even though the correct diagnosis may be achieved by assessment of clinical presentation and of imaging and electrophysiological findings. The necessity for biopsy is thus controversial. In addition, a long-distance epineurotomy for decompression of the hypertrophic fascicles is useful. In order to preserve the residual function of the nerves, a complete resection is not recommended. Malignant transformation is not yet known, and tumor growth is stable for years.