Spinal lipoma is a congenital benign lesion consisting of mature fat tissue in the spinal canal. It develops as a result of neural tube closure defect and is usually associated with dysraphic anomalies. Three main types are defined: filum terminale lipoma (most common — fat infiltration with >2mm filum thickening), lipomyelomeningocele (cord-fat-skin continuity with posterior defect), and intradural lipoma (subpial location, fat tissue intermixed with cord). Frequently associated with tethered cord syndrome — conus medullaris located below L2-L3 with potential traction injury during growth. MRI is the gold standard: T1 hyperintense fat signal and signal loss on fat suppression sequences (STIR/fat-sat) is pathognomonic. Fat density on CT (-40 to -120 HU) is confirmatory. Shows no enhancement — enhancing fat-containing lesion should raise suspicion for liposarcoma or dermoid. Evaluable with neonatal spinal US. Surgical untethering in symptomatic cases.
Age Range
0-30
Peak Age
5
Gender
Female predominant
Prevalence
Uncommon
The embryological basis of spinal lipomas is neural tube closure defect. During neural tube closure at gestational weeks 3-4, normal separation between cutaneous ectoderm and neural ectoderm is disrupted — mesenchyme (fat precursor tissue) migrates into or onto the neural tube and differentiates into mature fat tissue. In filum terminale lipoma, fat cells infiltrate within the connective tissue of the filum terminale — the filum thickens (>2mm) and loses elasticity. This thickened filum holds the conus low (tethered cord). In lipomyelomeningocele, the neural placode (open neural tissue) continues directly with fat tissue extending subcutaneously — posterior bony elements are defective (spina bifida). In intradural lipoma, fat tissue is intermixed with cord in the subpial space — no clear boundary between neural tissue and fat. T1 hyperintense signal on MRI reflects the short T1 relaxation time of methylene (-CH₂-) protons in fat tissue — fat protons resonate at low chemical shift frequency and appear bright on T1. In fat-sat sequences, frequency-selective saturation (chemical shift-selective fat saturation) eliminates fat proton signal — lipoma darkens and diagnosis is confirmed. Absence of enhancement indicates the lesion consists of avascular, mature fat tissue — no neovascularization.
Bright signal isointense to subcutaneous fat on T1 + complete signal loss on fat-sat/STIR. This two-sequence combination confirms fat content and is the pathognomonic diagnostic criterion for spinal lipoma. All fat-containing lesions show this pattern but spinal location and congenital presentation are specific to lipoma.
Lesion shows homogeneous hyperintense signal isointense to subcutaneous fat on T1-weighted sequences. Linear fat stripe along the filum is seen in filum terminale lipoma. Cord-fat continuity is visible in lipomyelomeningocele. Fat mass within or on the cord surface in intradural lipoma. Signal homogeneity reflects the uniform structure of mature fat tissue.
Report Sentence
Hyperintense lesion isointense to subcutaneous fat in filum terminale/intradural space on T1-weighted sequence, consistent with spinal lipoma.
Lesion that is bright on T1 becomes completely dark (signal loss) on fat-sat or STIR sequences. This finding confirms the lesion consists of true fat tissue. If complete signal loss does not occur on fat-sat, mixed lesion (dermoid, teratoma) or artifact should be considered. Chemical shift artifact (fat-water interface) may be seen at edges of large lipomas.
Report Sentence
Complete signal loss of the T1-bright lesion on fat suppression sequences (STIR/fat-sat), confirming fat content.
Lesion is observed at fat density on CT: measurement between -40 and -120 HU. Homogeneous low density. No enhancement. Posterior bony elements may be defective (spina bifida). Fat infiltration in filum can be detected on thin-section CT.
Report Sentence
Fat-density lesion ([X] HU) in filum terminale/intradural space on CT, consistent with spinal lipoma.
In neonatal period, posterior elements are not yet ossified — spinal US can evaluate cord, conus, filum terminale, and lipoma. Lipoma appears as a hyperechoic (fat = high echo) mass. Conus position is measured — below L2-L3 suggests tethered cord. Filum thickness is assessed — >2mm thickening is abnormal.
Report Sentence
Hyperechoic mass in filum terminale region on neonatal spinal US consistent with spinal lipoma; conus at L[X] level, tethered cord should be assessed.
Lipoma shows no enhancement on post-gadolinium T1 — same signal intensity as pre-contrast T1. On fat-sat contrast sequence, darkening of lipoma with no enhancement is clearly visible. This finding confirms the avascular nature of mature fat tissue. Enhancing fat-containing lesion should suggest liposarcoma, dermoid, or teratoma.
Report Sentence
No enhancement is observed in the lipoma on post-contrast series, consistent with avascular nature of mature fat tissue; no findings of malignant transformation.
Criteria
Filum terminale >2mm thickening. T1 hyperintense fat along filum. Spina bifida may or may not be present.
Distinct Features
Most common type. Usually incidental. Untethering with filum section if tethered cord present.
Criteria
Cord-fat-skin continuity. Posterior bone defect (spina bifida). Subcutaneous lipoma connected to cord.
Distinct Features
Noticed as subcutaneous mass at birth. Requires surgical correction and untethering. High risk of developing neurological deficit.
Criteria
Subpial location. Fat tissue intermixed with cord. Bone defect may be absent.
Distinct Features
Rare type. Complete surgical resection difficult (intermixed with cord). Debulking may be performed.
Distinguishing Feature
Schwannoma appears as isointense-hypointense on T1, hyperintense on T2 solid mass with marked enhancement. Lipoma is T1 hyperintense (fat signal), loses signal on fat-sat, and shows no enhancement. These two-sequence differences provide definitive differentiation.
Distinguishing Feature
Tethered cord syndrome is a clinical condition not a diagnosis — conus located below L2-L3. Lipoma is the most common cause of tethered cord but other causes exist (tight filum, dermal sinus, diastematomyelia). Lipoma is identified by T1 fat signal; in tight filum, only filum thickening without fat signal is seen.
Distinguishing Feature
Arachnoid cyst shows CSF signal (T1 hypointense, T2 hyperintense) — lipoma shows T1 hyperintense fat signal. Arachnoid cyst retains signal on fat-sat while lipoma loses signal. This fundamental signal difference is sufficient for differentiation. Arachnoid cyst is thin-walled; lipoma is homogeneous solid fat mass.
Urgency
routineManagement
surveillanceBiopsy
Not NeededFollow-up
6-monthSpinal lipoma is a benign congenital lesion — malignant transformation is not expected. Clinical significance depends on tethered cord syndrome association. Asymptomatic filum terminale lipoma can be followed as an incidental finding — annual MRI monitoring of conus position and neurological status. Surgical untethering is indicated for symptomatic tethered cord (foot deformities, bladder dysfunction, lower extremity weakness, scoliosis): filum section for filum terminale lipoma (simple and low-risk), lipoma debulking + cord untethering for lipomyelomeningocele (complex), partial debulking for intradural lipoma. Surgical timing is controversial — some centers recommend prophylactic untethering while others prefer waiting until symptoms develop. Prenatal MRI or US diagnosis is possible — family counseling and birth planning can be done.
Spinal lipoma is frequently associated with tethered cord syndrome — neurological deterioration (foot deformities, bladder dysfunction, lower extremity weakness) may develop with growth. Surgical untethering (filum section or lipoma debulking) is performed in symptomatic patients. Incidental filum terminale lipoma may remain asymptomatic — follow-up recommended. Prenatal diagnosis is possible.