Fibrolipoma of the Filum Terminale: A Rare Incidental Lesion

A 29-year-old woman presented with low backache of 6 months duration. Systemic and neurological findings were unremarkable. Sphincter dysfunction was absent. CT scan (Figure: (a) sagittal view; (b) coronal reconstruction; (c) axial image) revealed a linear fat density area of thikness 3 mm decreasing in diameter caudally within the filum terminale extending from L2 to L5 vertebral level, suggesting fibrolipoma of filum terminale. The position of the conus medullaris was seen at normal level. There was no other abnormality. Fibrolipomas of the filum terminale are embryonic in origin and frequently asymptomatic. They are seen on CT and MR images as areas of fatty tissue along the filum terminale. These lipomas may result from developmental malformation that occurs during the formation of the neural tube and leads to inclusion of embryonic crests of fat cells. A fibrolipoma “infiltrates” the filum and tends to be tubular. Fibrolipoma affecting the filum terminale are rare benign tumours usually discovered at imaging and rarely symptomatic, sometimes associated with radicular pain. Low position of the conus medullaris (below L2 vertebra) is a spectrum of associated congenital abnormality that may lead to neurological, musculoskeletal, urological, or gastrointestinal abnormalities. Split cord malformation (diastematomyelia) and a dermal sinus are also possible findings.