USE OF THE PRONE POSITION IN THE MRI EVALUATION OF SPINAL-CORD RETETHERING

In order to determine the impact of magnetic resonance imaging (MRI) i n the management of spinal cord retethering, we retrospectively review ed case and imaging records of 51 patients who underwent MRI examinati on in supine and prone positions. Group 1 included 8 control patients without cord tethering. They exhibited a normal level of the conus med ullaris with normal surrounding subarachnoid space, and consistent ant erior migration of the conus within the dural sac on MRI in prone posi tion. Group 2 included 17 patients with tethered cord secondary to occ ult spinal dysraphism (spinal cord lipoma in 6 patients, thick filum t erminale in 4, diastematomyelia in 4, myelomeningocele manque in 2, an d dermoid tumour in 1), Supine and prone MRI performed at a median per iod of time of 6 months after untethering showed resolution of posteri or tethering in 5 out of the 7 patients who exhibited pre-operatively dorsal attachment of the spinal cord to the dura. Anterior migration o f the conus or of the cord/filum complex in prone position was observe d in only 24% of the cases. Group 3 included 26 patients with secondar y tethered cord following prior myelomeningocele closure. Their MRI pe rformed at a median interval of time of 11 months following untetherin g demonstrated resolution of the posterior cord tethering in only 8 ou t of the 24 patients who exhibited this feature pre-operatively. Anter ior migration within the expanded dural sac was never noted in this gr oup. We conclude that spine MRI is of limited value and that prone-pos itioned MRI is of no additional use in the evaluation of spinal cord r etethering.