A 65-year-old woman comes to the office due to progressively worsening weakness of the legs for 5 months. Examination shows increased muscle tone, brisk deep tendon reflexes, and decreased muscle strength in the lower extremities. The Babinski sign is positive in both legs. Upper extremities are normal. MRI of the spine reveals a 2-cm, round lesion with homogeneous, intense contrast enhancement compressing the spinal cord at the T12 level; the lesion is extramedullary but is surrounded by cerebrospinal fluid, as shown in the exhibit. Which of the following is the most likely cell of origin of the lesion?
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This patient has spinal cord compression due to a contrast-enhancing tumor located in the intradural (surrounded by cerebrospinal fluid) extramedullary space. This is most likely a meningioma, a slow-growing, benign tumor that arises from the meningothelial cells of the arachnoid.
Spinal cord tumors can often be differentiated by their specific location:
Intramedullary space: space inside the spinal cord itself. Examples include primary spinal tumors (eg, ependymoma, astrocytoma).
Intradural extramedullary space: space within the meninges (ie, inside the dura but outside the spinal cord). Examples include nerve sheath tumors (eg, schwannoma, neurofibroma) and tumors that originate from the meninges (eg, meningiomas).
Extradural space: everything outside the dura, which includes the epidural space and the osseous vertebral body. Examples include vertebral metastases.
(Choice A) An ependymoma in the spinal cord arises from the ependymal lining of the central canal and, therefore, would be located in the intramedullary space.
(Choice C) Neoplastic spinal cord compression due to metastatic tumor cells most commonly results from local extension of neoplastic cells from the vertebral body into the epidural space. Therefore, metastases are located in the extradural space.
(Choice D) Osteoblasts are located in the periosteum and endosteum of the bone of the vertebral bodies. Tumors arising from osteoblasts would be extradural.
(Choice E) Hemangiomas are vascular malformations formed by the proliferation of vascular endothelial cells. These most often occur in the vertebral body (extradural space).
Educational objective:
Meningiomas arise from the meningothelial cells of the arachnoid. Therefore, when they form in the spinal cord, they are located within the meninges in the intradural extramedullary space.