I am looking for any advice and assistance in the diagnosis minimally tethered cord. That is to say the conus is normally positioned but the cord is the tethered and the patient is symptomatic. One of my neurosurgery colleagues is interested in evaluating patients for the presence or absence of normal motion of the conus via a MR cine technique. Thus far my literature search has not been too helpful, both with respect to validity of diminished conus motion correlating with a clinical tethered cord syndrome, what would constitute normal vs. abnormal in an adult and as to specific pulse sequence details. I have tried a few phase contrast and cardiac motion pulse sequences that have either not worked out or that did not show conus movement in individuals not suspected to have a clinical tethered cord syndrome. Any input would be appreciated.
Tethered Cord in Adult Patients
My experience with Cine MRI of the conus has been disappointing. To me, the conus always appears to move even if tethered as the end/start of the cine loop causes the image to ‘jump’. But as you mention in your blog, the normal conal movement may be too subtle for us to clearly see. This is similar to what I seen when US of the potentially tethered cord is done. The lack of pulsation is very subjective and difficult to assess. When a tethered cord is suspected, I have tried obtaining supine and prone MR images and have seen the normal conus displaced anteriorly in the latter when normal and the opposite when tethered. No doubt, the confirmation of a tethered conus is difficult. Patients with symptoms of tethering and a thickened filum terminale despite a normal conal position may benefit from surgery. Rather than a true anatomical untethering (as the nerve roots that developed at the same time must also be shortened) this may improve the metabolism of the distal cord. But even of the conus is low, do not expect to see it return to a normal position after surgery. What measures the success of surgery is improvement or lack of symptom progression.