Chapter 4 Intradural Extramedullary Benign Tumors
In the intradural extramedullary space, tumors from various origins can be found. Most of them are benign. Meningiomas are dural-based neoplastic proliferations of meningothelial cells. Their histologic grading is based on histologic subtype, necrosis, and mitotic rate. Their histologic variation includes meningothelial, fibrous, transitional, psammomatous, clear, chordoid, atypical, papillary, and rhabdoid subtypes.
Schwannomas are the most common spinal tumor. They are proliferations of neoplastic Schwann cells, which may have variable appearances (e.g., spindled, epithelioid, or melanotic). Schwannomas may be found throughout all levels of the spinal cord and involve the sensory nerve roots.
Neurofibromas are the proliferation of all components of a nerve, including Schwann cells, collagen, and perineurial cells. They are typically extradural lesions that may extend proximally to an intradural location.
Ganglioneuromas are one type of neuronal tumors in which the neoplastic cells express a mature neuronal phenotype. Most spinal ganglioneuromas involve the paraspinal region with intraspinal extension.
Fig. 4-1 Histologic subtypes with grade I morphology. A, An otherwise low-grade meningothelial meningioma with a small focus of brain invasion. B, Fibrous meningioma composed of fascicles of spindle-shaped cells. C, Transitional meningioma with components of meningothelial (upper half) and fibrous (lower half) subtypes. D, Psammomatous meningioma composed of near confluent psammoma bodies with few intervening meningothelial cells (A-D, hematoxylin–eosin stain, ×100).
Fig. 4-2 Atypical features in meningiomas. A, Patternless or sheet-like growth pattern. B, Focus of spontaneous necrosis. C, A hypercellular area containing cells with prominent nucleoli and mitotic figures. D, Glial fibrillary acidic protein immunohistochemical stain of tumor in Fig. 4-1, A highlighting brain parenchyma between the infiltrating tumor nests (×100). (A-C, hematoxylin–eosin stain; A and B, ×100; C, ×400.)
Fig. 4-4 Sagittal MRI of intradural meningioma. On T2WI, a small, round mass is seen in the intradural space at the T7 level (left). The mass signal is isointense to the spinal cord. It is located in the subarachnoid space posterior to spinal cord. On T1WI, the mass signal also is isointense to the spinal cord (middle). With contrast, a homogeneous enhancement pattern is shown (right).
Fig. 4-5 MRI axial images of intradural meningioma. On T1WI, a large iso-signal round mass is located at the posterolateral side of the intradural space (left image) with a homogeneous enhancement pattern (middle image). The spinal cord is compressed and displaced to the right anterior side. On T2 axial image adjacent caudal level to the tumor mass, a widened subarachnoid space is seen as bright high signal area (right image).
Fig. 4-6 Intraoperative view of spinal cord meningioma. After dural opening, the arachnoid membrane is seen to cover the tumor mass. Arachnoid dissection is done. A gray to white mass of slightly hard consistency is adhered to the pial membrane of the spinal cord (left image). After resection is completed from dural attachment, en bloc removal of the tumor mass is achieved (right image).