Spinal myxopapillary ependymoma
Spinal myxopapillary ependymomas are a variant type of spinal ependymoma that occur almost exclusively in the conus medullaris and filum terminale. They represent 13% of all spinal ependymomas, and are by far the most common tumours of the conus medullaris and filum terminale.
They tend to have an earlier clinical presentation than other spinal ependymomas, with a mean age of presentation of 35 years. There is a slight male predominance.
The most common presenting symptoms are low back, leg or sacral pain. Up to 25% of patients may present with leg weakness or sphincter dysfunction.
They may occasionally present as a subarachnoid haemorrhage 8.
They are thought to arise from the ependymal glia of the filum terminale or conus medullaris. The vast majority are intradural and extramedullary, however, rarely they occur in the extradural space. They are generally classified as WHO grade I lesions, however, occasionally CSF dissemination occurs and multiple lesions are seen in 14-43% cases 4. In children, these tumours may have more aggressive behaviour 9.
They are typically multilobulated and encapsulated. They often have associated haemorrhage and may calcify or undergo cystic degeneration 9.
Histologically, they contain papillary elements arranged radially around a hyalinized fibrovascular core, forming perivascular pseudorosettes, with myxoid material between the blood vessel and tumour cells 9. "Balloons" - rounded eosinophilic PAS positive structures - are sometimes encountered 9.
Plain radiograph / CT
If they become large, myxopapillary ependymomas may expand the spinal canal, cause scalloping of the vertebral bodies and extend out of the neural exit foramina.
Smaller tumours tend to displace the nerve roots of the cauda equina; larger tumours often compress or encase them 8.
- usually isointense
- prominent mucinous component occasionally results in T1 hyperintensity
- haemorrhage and calcification can also lead to regions of hyper- or hypointensity
- overall high intensity
- low intensity may be seen at the tumour margins because of haemorrhage (myxopapillary ependymomas are the subtype of ependymomas that are most prone to haemorrhage 8)
- calcification may also lead to regions of low T2 signal
T1 C+ (Gd)
- enhancement is virtually always seen
- the enhancement pattern is typically homogeneous. However, they can have a variable enhancement pattern that, in part, depends on the amount of haemorrhage present
Treatment and prognosis
Myxopapillary ependymomas are generally slow-growing, although some sacral and presacral lesions behave aggressively and metastasise to lymph nodes, lung and bone. This is particularly the case in children 9.
They can often be excised completely. In these cases, the prognosis is excellent, with 5-year-survival over 98% 9.
If the tumour has extended into the subarachnoid space and surrounded the roots of the cauda equina, resection is often incomplete and local recurrence is likely.
Differential diagnosis of a small conus and filum terminale myxopapillary ependymoma includes:
Differential diagnosis of a large myxopapillary ependymoma that causes sacral destruction:
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