Teaching Case

50-year-old man with lower back pain. MRI ordered to investigate suspected lumbar disc herniation.

MRI of the lumbar spine shows multiple intradural extramedullary masses in the lumbosacral spine. The largest is at L2-L3, sausage-shaped, and measures 11x16x45 mm. Smaller ovoid masses are at L4, L4-L5, and S1. They are heterogeneously hyperintense on T2WI, isointense on T1WI, and intensely enhancing on T1WI C+. They do not protrude into the neural foramina. There are no associated cysts, and there is no associated haemorrhage or scalloping of the vertebral bodies. MRI of the head and complete spine excluded the presence of additional lesions.

Myxopapillary ependymoma (ME) is a slow-growing glioma almost exclusively found in the region of the conus medullaris, filum terminale, and cauda equina [1]. Little is known about its aetiology [2], as it is very rare--227 intradural spinal ependymomas occur in the US annually [3]. The average age at diagnosis is 36.4 years, although the range is 6 to 82 [4], and it is twice as common in men as in women [1]. This neoplasm arises from the ependymal glia of the filum terminale [3] and is highly vascular [2]. It is typically intradural and extramedullary [5] and is grossly ovoid [1], lobular or sausage-shaped, and encapsulated [3]. It is regarded as relatively benign and slow-growing [6], WHO grade I [4], and rarely spreads distantly, although this can happen, particularly if its capsule is perforated [7]. Multiple lesions can be found in 14-43% of cases [8].

Clinically, ME mimics discogenic pathology by manifesting as lower back pain [5]--diagnosis is often delayed until 2 years after onset [1]. Radiculopathy [5], sciatica, saddle sensory loss, and bowel dysfunction have been seen in some cases [8]. MRI is the best modality for intraspinal disease [9], and is essential to identifying additional lesions and planning treatment [8].

On MRI, the ME is well-circumscribed and generally spans 2-4 vertebral segments [1]. It is T1 isointense and T2 hyperintense [1], although it can be hyperintense on both due to accumulated mucin or haemorrhage [8]. It is intensely enhancing with contrast [1]. It compresses, rather than infiltrates, adjacent structures [10]. 50% of cases are associated with cysts, which contrast helps delineate, and 19% involve haemosiderin deposits suggestive of haemorrhage [11]. Hence, appearance may be heterogeneous. 63% demonstrate osseous changes, such as scalloping of the vertebral bodies or erosion of medial pedicles [11]. It is responsible for 83% of neoplasms involving the filum terminale [8].

Complete surgical resection is the optimal treatment [4] and results in excellent prognosis [1]. In subtotal resections or nonsurgical candidates, adjuvant radiotherapy to the primary site is recommended to prevent recurrence [12]. After radiotherapy, patients should be followed yearly for 6-8 years [13]. In this patient, the largest lesion was excised, and the others were irradiated. At 8 year follow-up, the irradiated lesions remain but are smaller, and there is no recurrence of the largest lesion.

ME is a rare cause of back pain, detectable on MRI, that is the most likely neoplasm in the filum terminale.