110. Intra-laminar Mini-laminotomy for Infra-conus Selective Dorsal Rhizotomy Approach for Minimally-Invasive Management of Spasticity

Authors: Neena Ishwari Marupudi, MD, FAANS

Selective dorsal rhizotomy (SDR) for treating spasticity in children with cerebral palsy is an effective, well-validated surgical approach. Conventional techniques include multi-level-laminectomy, single-level-laminectomy at conus, and infra-conus single-level-laminectomy. We present a novel modification of the infra-conus technique: an intra-laminar, mini-laminotomy (ILML) approach for minimally-invasive SDR with limited or no bone removal. This technique may minimize pain, deformity, and allow earlier patient mobility/therapy.Methods: Patients undergoing SDR with ILML approach at Children’s Hospital of Michigan (2018-August 2021) were included in the study (n=33, follow-up: 3-months to 3.5-years). Twenty-eight patients with spastic diplegia underwent preoperative and serial postoperative assessment of gross-motor-function-measures (GMFM), strength, endurance, and tone. Linear mixed model with random-intercept was used to analyze recovery/improvements of function/endurance. Surgical technique entails a 3-cm midline incision spanning the intra-laminar junction just below the conus. Ligamentum flavum is removed in the intra-laminar space, and if necessary, a limited mini-laminotomy is performed. Thecal sac is opened, and using intraoperative electromyography, motor and sensory nerve roots are distinguished. Abnormal sensory nerve rootlets are partially cut. Target muscle groups are determined based on preoperative assessments.
No patients who underwent SDR with ILML approach developed CSF leak, intractable pain, infection, spinal deformity/kyphosis, or bowel/bladder dysfunction. In patients with spastic diplegia, GMFM surpassed preoperative levels between 3 and 6-months after surgery. The postoperative rate of improvement in GMFM score was 2.03 per month (p < 0.0001). The patients surpassed preoperative endurance measures (6-minute-walk-test) between 12 and 15-months after surgery. The postoperative rate of improvement in 6-minute-walk-test was 62 steps per month (p=0.0006). All patients tolerated initiation of inpatient rehabilitation therapies on postoperative day 3.
This modified minimally-invasive surgical technique for SDR is feasible, safe, and produces expected clinical outcomes in this patient population. The technique minimizes risk of spinal deformity/kyphosis and intractable pain, while optimizing early participation in inpatient rehabilitation program.