= partially encapsulated mass of fat + connective tissue in continuity with leptomeninges / spinal cord
- skin-coated subcutaneous back mass, occasionally associated with hemangiomatous / hairy lesion
- sensory deficiency, paresis, neurogenic bladder
Types:
- lipomyelomeningocele (84%)
- fibrolipoma of filum terminale (12%)
- intradural lipoma (4%)
Location: lumbosacral region
◊Intradural lipomas + lipomyelomeningoceles represent 35% of skin-covered lumbosacral masses + 20–50% of occult spinal dysraphism!
= subpial juxtamedullary mass totally enclosed in intact dural sac
Prevalence:<1% of primary intraspinal tumors
Etiology: abnormal embryonic neurulation
Age peaks: first 5 years of life (24%), 2nd + 3rd decade (55%), 5th decade (16%)
- slow ascending mono- / paraparesis, spasticity, cutaneous sensory loss, defective deep sensation (with cervical + thoracic intradural lipoma)
- flaccid paralysis of legs, sphincter dysfunction (with lumbosacral intradural lipoma)
- overlying skin most often normal
- elevation of protein in CSF (30%)
Location: thoracic (30%) / cervicothoracic (24%) / cervical (12%)
Site: dorsal aspect of cord (75%), lateral / anterolateral (25%)
- spinal cord open in midline dorsally
- lipoma in opening between lips of placode
- exophytic component at upper / lower pole of lipoma
- syringohydromyelia (2%)
- focal enlargement of spinal canal ± adjacent neural foramina
- narrow localized spina bifida
= lipoma tightly attached to exposed dorsal surface of neural placode blending with subcutaneous fat
Prevalence: 20% of skin-covered lumbosacral masses; in up to 50% of occult spinal dysraphism
Age: typically <6 months of age; M <F
- semifluctuant lumbosacral mass with overlying skin intact
- sensory loss in sacral dermatomes, motor loss, bladder dysfunction; foot deformities, leg pain
Location: lumbosacral; longitudinal extension over entire length of spinal canal (in 7%)
Site:
- lipoma dorsally continuous with subcutaneous fat
- lipoma may extend upward within spinal canal external to dura (= “epidural lipoma”)
- lipoma may enter central canal and extend rostrally (= “intradural intramedullary lipoma”)
- deformed undulating spinal cord with dorsal cleft
- tethered cord
- ventral + dorsal nerve roots leave neural placode ventrally
- dilated subarachnoid space
US:
- echogenic intraspinal mass adjacent to deformed spinal cord + continuous with slightly hypoechoic subcutaneous fat
- Vertebral changes
- large spinal canal
- erosion of vertebral body + pedicles
- posterior scalloping of vertebral bodies (50%)
- focal spina bifida
- segmental anomalies / butterfly vertebra (up to 43%)
- confluent sacral foramina / partial sacral agenesis (up to 50%)
Fibrolipoma of Filum Terminale
Prevalence: 6% of autopsies
- asymptomatic
Location: intradural filum, extradural filum, involvement of both portions
- thin linear fat-containing mass of filum terminale
Prognosis: potential for development of symptoms of tethered cord