What is the recommended treatment for filum fibrolipoma?

Filum Fibrolipoma: Recommended Treatment

Surgical untethering by sectioning the filum fibrolipoma is the definitive treatment, particularly when symptomatic or when tethered cord syndrome is present, with surgery being both safe and effective in preventing neurological deterioration. 1, 2

Initial Assessment and Diagnosis

• MRI of the spine with contrast is the gold standard imaging modality to confirm the diagnosis and assess for tethered cord syndrome 3
• Look specifically for: low-lying conus medullaris (below L2-L3), thickened fatty filum terminale (>2mm), and associated spinal dysraphism 2, 4
• Electromyography (EMG) of lower limbs should be performed preoperatively to document baseline neurological function 3
• Urodynamic studies are appropriate even in asymptomatic patients to assess bladder function 3

Indications for Surgical Intervention

Surgery should be performed early, even in asymptomatic patients, to prevent development of neurological deficits. 3

Absolute indications for surgery:

• Progressive neurological symptoms including motor weakness, sensory deficits, or sphincter dysfunction 2, 4
• Clinical or radiological evidence of tethered cord syndrome 5
• Pain related to cord tethering 4

Relative indications:

• Asymptomatic patients with confirmed filum lipoma to prevent future deterioration 3
• The natural history of untreated filum lipomas appears to be progressive neurological deterioration with loss of bladder control 2

Surgical Technique

The interlaminar approach (ILA) is the preferred minimally invasive technique for filum lipoma sectioning 1

Key surgical steps:

• Minimal skin incision to expose unilateral ligamentum flavum in the lower lumbar region 1
• Ligamentum flavum incision to expose the dural sac 1
• Dural incision followed by identification and sectioning of the filum 1, 3
• Subtotal excision of lipoma with spinal cord untethering is the primary goal 2, 3
• Suturing of the spinal pia mater is of extreme importance in preventing postoperative retethering 3

Surgical outcomes:

• Filum lipoma untethering carries significantly lower risk than lipomas of the conus medullaris 2
• Neurological morbidity in filum lipoma untethering is extremely low 5
• No postoperative bed rest is required with the minimally invasive approach 1

Role of Intraoperative Neuromonitoring

Intraoperative neuromonitoring (IONM) may not be required for all filum lipomas and should be used judiciously 5

• Filum lipoma untethering is an inherently low-risk microsurgery in experienced hands with rarely reported neurological morbidity 5
• IONM did not alter surgical course or prevent complications in a cohort of 80 children 5
• Thorough microscopic inspection is more reliable than IONM responses for identifying the filum 5

Postoperative Management and Follow-up

• Postoperative MRI should be performed to confirm cord untethering 3
• Long-term follow-up with neurological examination, EMG, and MRI is recommended 3
• Mean follow-up duration should extend to at least 2 years 3

Expected outcomes:

• Asymptomatic patients remain symptom-free in the vast majority of cases (20/20 in one series) 3
• Symptoms can disappear completely or improve in patients with preoperative deficits (60% improvement rate) 3
• No retethering or additional neurological symptoms should occur with proper surgical technique 1

Common Pitfalls and Caveats

• Do not confuse filum lipomas with lipomas of the conus medullaris - they are entirely different lesions with different surgical risks and outcomes 4
• Lipomas of the filum have excellent surgical results with no complications, while conus lipomas carry 20% local and 3.9% neurological complication rates 4
• Avoid excessive delay in surgery - the risk of pathology increases with time, and recovery from established deficits is rare 4
• Temporary neurological deterioration (slight leg weakness or urinary retention) may occur postoperatively but typically recovers completely within days 3
• Reoperation rates are low (5.5%) but may be necessary for retethering 4