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Neuroradiology Case of
the Week
Case 242
Jeremy Duda, BA, Jerry Lee, MD, and P-L Westesson, MD, PhD, DDS
Clinical
Presentation: A
64-year-old female with progressive bilateral lower extremity weakness and decreased sensation.
Imaging Findings: Axial and sagittal sections demonstrate an intradural extramedullary lesion measuring 1.1 x 1.3 x 1.5 cm posterior and to the right of spinal cord at the level of T5-T6 vertebrae. There is no invasion of adjacent soft tissue or bone. The mass is isointense to spinal cord on T1 and T2 weighted imaging and brightly enhances with gadolinium on T1 fat saturation images.
Diagnosis: Benign thoracic meningioma
Differential Diagnosis: The differential diagnosis for an intradural extramedullary spinal tumor includes meningioma, schwannoma, and neurofibroma.
Discussion: Meningiomas arise from the arachnoid cap cells of meninges and are benign 90% of the time. By definition they do not involve the parenchyma of the CNS although they may cause symptoms by compression. They are more often located intracranially (90% of the time), but account for as much as 25% of all primary spinal tumors. Three quarters of spinal meningiomas are found at thoracic vertebral levels, usually in the posterior spinal canal.
The tumors are found in women about 80% of the time with a mean age of 53. A role for endogenous steroids has been proposed in the development and proliferation of these tumors. Meningiomas have been found to increase in size with pregnancy and hormone therapy, and have a higher incidence in obese individuals and breast cancer patients.
Cells of these lesions often exhibit mutations on chromosome 22 where the NF2 gene is located – indeed, meningiomas have an increased incidence in patients with neurofibromatosis type II. Ionizing radiation as given during therapy for cancers is also noted to be a risk factor for developing a meningioma.
Clinical symptoms can be due to cord or nerve root compression, with localized back pain more commonly reported (56%) than radicular symptoms (21%) in one study. Weakness, paresthesias, and bowel or bladder dysfunction are common complaints, and patients often are found to have a range of neurological deficits on exam. The clinical picture is often vague with insidious onset owing to the slow growth of the tumor: retrospective studies have reported rates of initial misdiagnosis from 24-32%.
Radiographs are ineffective for detecting meningiomas, as abnormalities are only detected 21% of the time in patients with the disease. Myelography, which was the test of choice to define spinal lesions before routine use of cross sectional imaging was available, will demonstrate an intradural extramedullary lesion that expands the thecal sac, with a plane of contrast separating the tumor from the spinal cord. Today, MR can define the tumor’s location, whether it compresses or invades local structures, and may help differentiate it from other intradural extramedullary lesions. Meningiomas, which are isointense to spinal cord on T1 and T2 weighted imaging and enhance with gadolinium, can be distinguished from neurinomas which demonstrate a hyperintense signal on T2. Meningiomas may be associated with peritumoral edema and bony erosion or hyperostosis. Calcifications may be found within the tumor but are rarely visualized on imaging.
The treatment of choice for intraspinal meningiomas is total resection, or adjunctive radiation in cases of subtotal resection. The prognosis is excellent for patients undergoing surgery: 85% of patients from one study had clinically stable or improved neurological function after surgery. Recurrence rates in spinal disease are low (6% in one series) compared with intracranial lesions (30%). As above, the disease is typically benign, and patients often die of other causes in follow-up studies. Overall survival at 5 years from is estimated at 70% for benign meningiomas and 55% for malignant tumors.
References:
- Levy WJ Jr, Bay J, Dohn D. Spinal cord meningioma. J Neurosurg. 1982 Dec;57(6):804-12. [Medline]
- Solero CL, Fornari M, Giombini S, et al. Spinal meningiomas: review of 174 operated cases. Neurosurgery. 1989 Aug;25(2):153-60. [Medline]
- Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed., Chapter 102.
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