This young male presented with chronic but progressive low back pain and lower extremity weakness.  MR imaging of the lumbar spine with contrast showed a lesion, intradural/extramedullary, extending from T12 to L4.  The lesion “expanded” the spinal canal and produced significant remodeling (scalloping) of the posterior vertebral bodies.  The mass had mostly low T1 signal pre contrast, mostly high T2 signal and enhanced after gadolinium.  Is it a large myxopapillary ependymoma?

Analysis of axial images showed that the mass involved the spinal canal but extended out into the paraspinal regions, including the right psoas muscle, via several neural foramina.  The diagnosis was reconsidered to include giant invasive spinal schwannoma (histologically confirmed later).

Schwannomas are the most common primary spinal tumor occurring predominantly in the cervical and thoracic regions.  Tumors of the cauda equina region represent only 6% of all spinal masses; most are schwannomas. “Giant” schwannomas are rare, long lesions that expand, remodel or destroy adjacent bones.  When they extend to extra-spinal myofascial planes, they are considered “invasive”.  Symptoms vary from severe to mild. Total excision is advocated but not always feasible.  Spinal fusion after tumor resection is needed in most patients.  Perhaps, fewer than 20 cases of giant schwannomas are found in the modern literature nearly all of them in the lumbosacral region. They are not associated with NF-2. The main differential diagnosis is that of myxopapillary ependymoma. Giant ependymomas are more common in younger individuals and despite attaining large size they do not tend to produce the focal bone scalloping and paraspinal involvement that giant schwannomas typically show (see illustration below). Mutiple schwannomas, as seen in NF-2 could also have a similar appearance.

References:

Sridhar K, Ramamurthi R, Vasudevan MC, Ramamurthi B. Giant invasive spinal schwannomas: definiation and surgical management. J Neurosurg (Spine) 2001; 94: 210-215

Hung CH, Tsai TH, Lin CL et al. Giant invasive schwannoma of the cauda equina with minimal neurologic deficit: a case report and literature review. Kaohsiung J Med Sci 2008; 24: 212-217

Guyotat J, Fishcer G, Remond J et al. Giant ependymoma of the cauda equine. Long-term development apropos of 7 cases. Neurochirurgie 1993; 39: 85-91