11.8\ Filum Terminale Sectioning

11.8.1\ Discussion

Detethering of a tethered spinal cord by transecting or resecting a fatty filum terminale is performed to alleviate associated neurological symptoms. Postoperative MRI of the lumbar spine following detethering is generally performed if patients develop new symptoms suggestive of retethering or to assess associated conditions in patients with dysraphism that could

a

otherwise explain the clinical deterioration. Discontinuity, along with thickening of the upper and lower remnants of the sectioned filum, constitutes evidence of a detethered filum (Fig. 11.123). The presence of conus relaxation, indicated by elevation or a more ventral position, is also reassuring, but is not consistently observed. Obtaining prone and supine imaging during the MRI exam can also be useful, in which no appreciable translation of the conus medullaris is observed when rethethering has occurred (Fig. 11.124).

b

Fig. 11.123  Filum terminale sectioning. Preoperative sagittal T1-weighted MRI (a) shows a low-lying conus medullaris and fibrofatty filum terminate. Postoperative

sagittal T1-weighted MRI (b) shows a wide gap in of the fibrofatty filum with retraction and slight thickening of both remaining segments (arrows)

Fig. 11.124  Rethethering. Supine (a) and prone (b) sagittal T2-weighted MR images show findings related to prior detethering surgery, but no shift in the position of the

conus medullaris, which is low-lying and posteriorly deviated alongside the dura