MRI diagnosis of peripheral neurofibroma and schwannoma

Objective: To investigate the MRI features of peripheral neurofibroma and schwannoma. Methods: MRI of 18 patients with pathologically proven neurofibromas (7) and schwannomas (11) was retrospectively analyzed. Results: All 18 tumors were solitary and located in the limbs, abdominal wall, supraclavicular muscles or fascia, and in the carotid sheath. The lesions were fusiform or round parallel to the neural trunk. Of 18 tumors, 4 were T₁ isointense and T₂ hyperintense peripherally with T₁ and T₂ iso-hypointense centers and heterogeneous contrast enhancement. Eight lesions were T₁ isointense and T₂ hyperintense intermixed with patchy areas of T₁ and T₂ hypointensities and heterogeneous enhancement. Three schwannomas were cystic or cystic-solid with T₁ hypointensity and T₂ hyperintensity and homogeneous enhancement of cyst wall and septa. The remaining 3 tumors were T₁ hypo-isointense and slightly T₂ hyperintense with homogeneous enhancement. All 7 neurofibromas were not capsulated and located superficially in close relationship with nerves whereas all 11 schwannomas had complete or partial capsules and located deeper. Conclusion: MRI characteristics can aid in differentiating neurofibromas from schwannomas. Neurofibromas are superficial, non-encapsulated and slightly T₂ hyperintense. Schwannomas are located deeper, encapsulated and T₂ hyperintense with necrosis and cystic degeneration. (authors)