Teaching Case

28 year old femal patient. Hypostenia and hypoestesia localized at lower limbs and loss of sphincterial control. Lumbar spine MR pre- and post-surgery.

Hypostenia and hypoestesia localized in the lower limbs, loss of sphincteric control in a 28 year old patient. Lumbar spine MR pre- and post-surgery.

The patient presented with neurological symptoms and was referred to our institution for lumbar spine MRI examination. Sagittal T2, PD and T1 weighted images pre- and post- paramagnetic contrast medium i.v. administration, and axial T1 and T2 weighted images in the area of the suspected lesion were performed. The examination was repeated after the patient underwent surgery to remove the lesion. Images showed an irregularly oval contrast-enhancing mass at the level of the 3rd lumbar vertebra, with an intradural extramedullary location. Post surgical pathological diagnosis was neurinoma of the cauda. Tumors arising from the intradural extramedullary structures are mainly benign: nerve sheath tumors and meningiomas account for 80% to 90% of all. There are three types of nerve sheath tumors in the spine: schwannoma, neurofibroma and ganglioneuroma. Nerve sheath tumors represent the most common intradural extramedullary neoplasm, (25%-30%), schwannomas are slightly more common than neurofibromas, ganglioneuroma being the rarest type. Schwannoma, neurilemmoma and neurinoma are synonyms, while the neurofibroma is a distinct tumor. The gretest incidence of intradural extramedullary tumors is in the fourth decade of life. The most common localization of nerve sheath tumors is the cervical cord, followed by the thoracic and lumbar segments. Symptoms at presentation are pain and radiculopathy. Schwannomas consist generally of a single, lobulated, well defined, mainly encapsulated, rounded mass, not involving the dorsal sensory root, and arising from the periphery of the perve whose fibers are dislocated by the tumor. Multiple schwannomas are commonly associated with type 2 neurofibromatosis (NF-2). Malignant degeneration of schwannomas is very rare. MR imaging findings of nerve sheath tumors may vary: almost 75% of all nerve root tumors are isointense to cord on T1 weighted images, and 25% are hypointense. The vast majority are hyperintense on T2 weighted images (95%). Contrast enhancement is seen in virtually all tumors, with various degree of enhancement MR cannot distinguish between schwannomas and neurofibromas. The differential diagnosis is with other benign tumors, mainly meningioma, which is isointense both on T1 and T2, with moderate contrast enhancement, with a broad dural attachment, and a dural "tail" sign seen sometimes. Other tumors to be considered in the differential diagnosis are epidermoid and dermoid tumor, and ependymoma, with malignant nerve sheath tumors to be taken into consideration if necrosis or hemorrhage is present. Long term prognosis of neurinomas is favourable.