Myxopapillary Ependymoma

Myxopapillary ependymoma is a slow growing ependymal tumour of the conus medullaris, cauda equina and filum terminale, with a mucin rich papillary architecture. It is graded 2 and can be cured by complete en bloc resection, but it recurs locally and can spread through the cerebrospinal fluid.

It forms about 25% to 30% of spinal ependymomas and has an incidence of about 1 case in 1,000,000 people each year. Median age at diagnosis is 35 to 40, and it occurs in children, where it is more aggressive. There is a slight male predominance.

No risk factor is established. Associations with neurofibromatosis type 2 are described but uncommon.

Pathophysiology. The tumour arises from ependymal glia of the filum terminale. Cells show papillary growth around vascularised mucoid cores and express GFAP, S100 and often cytokeratin. Chromosomal gains are frequent, and the genetic profile differs from other spinal ependymomas.

Behaviour. Local recurrence after subtotal resection or capsule rupture is common. Leptomeningeal dissemination occurs in about 10% to 20%, more often in children. Distant metastasis (lung, bone) is rare. Survival at 10 years is over 90% with complete resection.

• Chronic low back pain, worse at night or when lying flat, often present for months to years.
• Sciatica, lower limb weakness and sensory change, gait difficulty.
• Bladder, bowel and sexual dysfunction (conus and cauda equina involvement).
• Rarely subarachnoid haemorrhage, and hydrocephalus with papilloedema from raised CSF protein.
• Children may present with scoliosis, torticollis and gait delay.

Red flags.

• New sphincter disturbance, saddle anaesthesia or rapidly progressive weakness (cauda equina syndrome).
• Sudden thunderclap headache (subarachnoid haemorrhage).

• MRI of the whole spine and brain with gadolinium: well defined enhancing mass at the conus or filum, often sausage shaped with cysts, haemorrhage or a hyperintense T1 signal from mucin. Spinal MRI is needed to exclude drop metastases.
• Lumbar puncture for CSF cytology 2 or more weeks after surgery when the tumour is resected, to avoid false positives.
• Histology: papillary pattern, perivascular mucin and hyalinised fibrovascular cores. Immunohistochemistry: GFAP and S100 positive, cytokeratin often positive, with low proliferation.
• Neurophysiological and urodynamic assessment of sphincter function before and after surgery.

Differential diagnosis.

• Schwannoma and meningioma of the cauda equina
• Paraganglioma of the filum terminale
• Subependymoma and other spinal ependymoma
• Metastasis, chordoma and sacral extradural tumours
• Lumbar disc disease (common alternative explanation of low back pain)

Surgery. En bloc gross total resection through laminectomy or laminoplasty with intraoperative neuromonitoring, without breaking the capsule, is the primary treatment. Piecemeal resection raises recurrence and CSF seeding.

Radiotherapy. Adjuvant focal radiotherapy (50.4 Gy in 28 fractions) after subtotal resection, capsule rupture or recurrence, to lower local recurrence. Craniospinal radiotherapy is used for CSF dissemination. Some centres give radiotherapy after gross total resection in children.

Systemic therapy. No chemotherapy has proven benefit. Referral to a study is reasonable for progressive disease that cannot be resected or irradiated.

Neuropathic pain.

• Gabapentin: gabapentin 300 mg orally at night on day 1, 300 mg twice daily on day 2 and 300 mg three times daily on day 3, then titrated every 3 to 7 days to 900 to 1800 mg daily in 3 divided doses; maximum 3600 mg daily; monitoring: sedation, dizziness, oedema, mood, falls, respiratory depression with opioids; adjustment: creatinine clearance 30 to 59 mL/min 400 to 1400 mg daily in 2 divided doses, 15 to 29 mL/min 200 to 700 mg once daily, under 15 mL/min 100 to 300 mg once daily, taper over at least 1 week when stopping

Perioperative oedema.

• Corticosteroid for symptomatic oedema or cord compression: dexamethasone 4 mg orally or IV once or twice daily for mild symptoms and up to 4 mg four times daily for marked oedema or raised intracranial pressure, for the shortest period, tapered over 1 to 2 weeks once symptoms settle; maximum 16 mg daily; monitoring: glucose, blood pressure, mood and sleep, gastric symptoms (gastric protection when combined with other risk factors), opportunistic infection, myopathy; adjustment: use the lowest effective dose, avoid prolonged courses because of myopathy, osteoporosis and infection, use lower doses in hepatic impairment

Monitoring. MRI of the whole spine 3 months after surgery, then every 6 months for 2 years, then yearly for at least 10 years because late recurrence is frequent. Neurological, bladder and bowel review.

Referral and escalation.

• Referral to a spinal neurosurgery and neuro oncology team on suspicion.
• Same day neurosurgical assessment for cauda equina syndrome.

Special groups.

• Children: more extensive disease and higher dissemination risk, so full neuraxis imaging and combined therapy are used.
• Pregnancy: surgery is possible when needed, with radiotherapy deferred.
• Patients with scoliosis or instability after laminectomy: spinal surgical review.