Extracranial and extraspinal neurilemoma: CT and MR findings

Neurilemoma or schwannoma is a benign tumor originating from the Schwann cell of the peripheral nerve sheath. Most frequently this nerve sheath tumor arises in cranial nerves, occasionally in extremity nerves and rarely in tetroperitoneum or mediastinum. We reviewed to determine CT and MR characteristics of extracranial and extraspinal neurilemoma. Eleven CT and 4 MR examinations in 12 patients were retrospectively reviewed. Extracranial and extraspinal neurilemoma were demonstrated as well-defined, round or voal inhomogeneously enhanced masses(11/12), located in the region of a known nerve ganglia or pathway, or perispinallyl. The densities of the tumors were lower than the adjacent muscles on the pre-enhanced CT scan and became more strongly enhanced than the tumors were similar to adjacent muscles on the T1WI and high signal intensities to that of adjacent muscles on the T2WI. Gd-enhanced MR shows inhomogenous peripheral or wall enhancement. The typical location as well as CT and MR imaging characteristics may be helpful in the preoperative diagnosis of the extracranial and extraspinal neurilemoma