Spinal cord tethering after selective dorsal rhizotomy below the conus medullaris

Two techniques for selective dorsal rhizotomy (SDR) involve stimulating and sectioning nerve rootlets either below the conus medullaris or above the entrances to their respective dural root sleeves. In general, both techniques lead to sustained improvements in lower extremity spasticity with low complication rates. To our knowledge, spinal cord tethering has not been previously reported as a complication of SDR using either technique.

We review the presentation, treatment, and outcome of two patients who developed symptomatic spinal cord tethering after SDR below the conus.

A 4-year-old male and a 6-year-old female each with a history of spastic diparetic cerebral palsy underwent L1-L2 osteoplastic laminectomy and SDR below the conus. Both surgeries went well with no known complications. Both patients initially did well, with marked improvement in their tone and gait. There were no significant immediate postoperative bowel or bladder problems. The male patient presented 10 months after surgery with new-onset urinary incontinence. A urological evaluation was performed but no imaging was performed. He re-presented 8 months later with worsened urinary incontinence, new fecal incontinence, and worsened gait. An MRI showed signs of tethering, including a holocord syrinx. He underwent two untethering surgeries as well syrinx fenestration, and although his gait improved, it remained worse than it had been several months after surgery. The incontinence did not improve. The second patient also developed urinary incontinence a year after SDR. Due to our experience with the first patient, we obtained an MRI immediately and found evidence of tethering. She underwent untethering and her incontinence improved.

We report two cases of spinal cord tethering after SDR below the conus, a previously unreported complication. It is important to realize that this complication can occur after SDR.