Filar Cyst Etiology: congenital Imaging: cyst in filum terminale Treatment: no followup needed Clinical: common normal variant, no followup needed in asymptomatic neonates / infants Radiology Cases of Filar Cyst Sagittal US of the spine (above) shows the conus medullaris to terminate normally at the L1-L2 level. A hypoechoic cystic structure is seen just inferior to the conus and is better seen on the zoomed image (below).