Spinal intradural lipoma not associated with spinal dysraphism

A 40-year female patient presented with chronic diffuse low back pain with new onset numbness and paresthesia of bilateral lower limbs. On examination, spastic weakness of B/L lower limbs was also seen.

MRI of lumbar spine was done which showed an oval-shaped intradural intradullary lesion in intimate relation to the conus medullaris. It is causing scalloping of the conus which itself is ending normally at L1 level. The lesion is extending from L1 to L4 level causing encasement of the filum terminale and lateral displacement of some of the nerve roots. It shows high signal on T1 and T2WI(Fig 1, 2 and 3) with complete suppression of signal on fat-saturated images(Fig 4).

There were associated spondylotic changes in the form of Modic changes, anterolisthesis of L5 over S1(Fig 5). B/L pars interarticularis defect was also seen(not shown). No associated spinal dysraphism was seen.

Background

Intramedullary lipomas are rare tumours contituting only 2% of intramedullary tumours [1].and are mostly seen in patients with spinal dysraphism. Isolated lipomas which are unassociated with spinal dysraphism are seen in only 1% of patients [2].

The pathogenesis of intramedullary lipomas are mainly attributed to maldevelopment process. The most popular opinion is embryologic inclusion of misplaced cell types during neural tube closure. Histologically, intramedullary lipomas consist of mature fat cells with intervening collagen fibers, and admixed nerve bundles are often located at the periphery, suggestive of secondary entrapment of adjacent nerve roots [3].

Clinical Perspective

Patients with intramedullary lipomas usually present with insiduous onset of neurologic dysfunction. Spastic paralysis is the most frequent presenting symptom. Sensory symptoms in the form of non-radiating pain, urinary incontinence, ataxia can be present. Dorsal column involvement is also a common feature [3].

Imaging Perspective

On CT, lipomas appear as hypodense (negative attenuation) well-defined lesion within the spinal canal. MR is the imaging modality of choice to delineate extent of the lesion, involvment of cord or filum terminale and associated other spinal dysraphism. Lipomas are hyperintense on T1 and T2 -weighted images. Benign lipomas have signal character similar to those of subcutaneous fat. Liposarcomas and other fat-related tumours are less hyperintense than subcutaneous fat due to longer T1 relaxation time. CT and MR imaging show characteristic imaging features and often obviate biopsy [1]. Cord lipomas commonly occur as single, well-defined loculi.

Outcome

For symptomatic lipomas, surgical decompression is indicated [1]. In order to reduce intra-operative damage of cord, CO2 laser and sonographic aspiration are used. Surgical intervention after onset of symptoms is unfavorable because of significant postoperative residual disability. Motor improvement is seen in 40% of symptomatic patients after surgery, and bladder control is achieved in only a minority of these patients [5].

Take Home Message / Teaching Points

Intradural lipomas without associated spinal dysraphism are rare. Surgical intervention is necessary when they present with neurological involvement.