MRI of intradural neurinoma

Clinical History

A 41-year-old female patient presented with a six-month history of pain in her lower limbs that was more pronounced during the night. The X-ray scan of dorsal vertebral column was found to be normal.

Imaging Findings

A 41-year-old female patient presented with a six-month history of pain in her lower limbs that was more pronounced during the night. The X-ray scan of the vertebral column was found to be normal. Therefore an MRI examination of the dorsal vertebral column was performed using axial, sagittal and coronal images on T1-weighted sequences, before and after gadolinium administration and completed with sagittal T2-weighted sequences, which showed the presence of an extramedullary intradural mass that had a low signal intensity on T1-weighted images, high signal intensity on T2 images, with a target pattern sign and a marked signal hyperintensity after contrast administration.

Discussion

`Extramedullary intradural tumors can be classified as meningiomas and nerve sheath tumors which represent about 90% of spinal cord tumors. Different types of spinal nerve sheath tumors have been recognized. Schwannomas, also known as neuromas or neurilemomas, usually appear as solitary tumors and occur mostly frequently. A third type of neurogenic spinal tumor, the ganglioneuroma, is very rarely found. The peak incidence of spinal nerve sheath tumors is in the fourth decade of one's life. There is no sexual predilection. These tumors are most often seen in the cervical or lumbar region, followed by the thoracic region. Typically, they are found on the dorsal sensory roots. More than half of all these lesions are found to be extramedullary intradural, about 25% are completely extradural, (15%) are both intra and extradural, and very rarely are seen intramedullary (<1%). The majority (>90%) of spinal nerve sheath tumors are known to be benign ^{( 3 )}. Sarcomatous degeneration is especially seen in patients with neurofibromatosis. Neurofibromas encase the nerve roots, whereas neurinomas more frequently develop asymmetrically and displace the nerve root. Neurinomas are composed of Schwann cells associated with fibrous material and often exhibit cystic degeneration and hemorrhage, but no calcification. It is also observed that nerve fibers do not run through the tumor. Neurofibromas are composed of Schwann cells, fibroblasts and nerve fibers in a matrix contaning mucopolysaccharides, fluid and fibrous material. Cyst formation is rarely known. Nerve sheath tumors are isointense as seen on T1-weighted images, and have a typically marked high signal intensity on T2-weighted images and sometimes show a target pattern. Their enhancement is variable and can be intense and homogeneous in some lesions, while other lesions may only show a faint peripheral enhancement. On imaging, differentiation of neurinomas and neurofibromas has been found to be unreliable. Inhomogeneity can be seen in both benign and malignant nerve sheath tumors. Malignant lesions tend to have more irregular and invading margins compared to benign lesions, and are seen to be usually larger at the time of diagnosis. It is also known that multiple spinal root tumors typically represent neurofibromatosis 1 (NF1). They are isointense to hyperintense on T2-weighted images, isointense on T1-weighted images and show a strong homogeneous enhancement and therefore a complete MRI investigation is mandatory in the workup of these patients. Spinal neurinomas can be very small and be located on the intraspinal nerve roots or may be larger and have a typical dumbbell shape with an intra or extraspinal localization. Besides this typical location, they also have a characteristically high signal intensity on T2-weighted images. Because they are slow growing lesions, bone erosion and remodeling is not uncommon. Spinal meningiomas which occur in younger patients may be more aggressive, with a worse prognosis. Spinal meningiomas frequently have calcifications (75%) and show a strong and homogeneous enhancement, except for the calcified areas. These tumors are usually solitary in their appearance, having a broad attachment to the dura and are usually located posterolaterally in the thoracic region and anteriorly in the cervical region. They are well circumscribed and clearly delineated from the spinal cord. Our patient underwent a surgical excision of the lesion, and a histological diagnosis was made.

Differential Diagnosis List

Final Diagnosis

Intradural neurinoma.

URL:	https://www.eurorad.org/case/3165
DOI:	10.1594/EURORAD/CASE.3165
ISSN:	1563-4086