Spinal Cord Tethering and Other Post-Operative Complications After Selective Dorsal Rhizotomy Using Two Surgical Techniques Katherine Belanger BS1, William McKay MD2, Corbett Wilkinson MD2, 3 1. University of Colorado School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA 2. Department of Neurosurgery, University of Colorado School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA, 3. Department of Neurosurgery, Children’s Hospital Colorado, University of Colorado Anschutz Medical Campus, Aurora, CO, USA v Introduction Table 1. Results Characteristics of 60 Patients • Selective Dorsal Rhizotomy (SDR) permanently alleviates lower limb spasticity by A B Patient Demographics: Characteristic n (%) reducing the aberrant spinal myotatic reflex impulses 1. • No statistical difference between the surgical Female:Male 18:42 2 • SDR is a proven efficacious neurosurgical procedure for the permanent improvement Age at SDR groups by gender (c (1, N=60)=0.004, p=0.95), of lower limb spasticity with a minor complication profile Mean 8.42 years age (t(58)=1.079, p=0.285), length of follow- • 2 surgical approaches that are predominantly used: Median 6.85 years up period (t(58)=1.95, p=0.056), etiology of • Peacock et al 3: multilevel laminectomy with nerve rootlets transected at multiple Range 4.1-24.9 years spasticity (p=1.00) or type of spasticity levels, each just before they exit into their respective dural root sleeves. Duration of Follow-up (p=0.329). • Park et al 2: 1-or-2 level laminectomy with nerve rootlets transected at a single Mean 2.88 years level, usually just below the conus medullaris. C Median 1.9D years Function and Spasticity: Range 0.1-9.8 years • • There is no evidence of difference in functional outcomes or complication rates Etiology of Spasticity No statistical difference pre-operatively between these surgical techniques. Cerebral Palsy 51 (85%) (p=0.734) or post-operatively (p=0.174) in • Often left to surgeon preference and patient’s clinical picture as to which is Brain Malformation 5 (8.3%) GMFCS levels between surgical techniques. performed 4. Abusive Head Injury 1 (1.7%) • Post-operative GMFCS level was statistically • At our institution both procedures are performed by a single surgeon (CCW) with Other 3 (5%) lower than pre-operative GMFCS level (Z=- choice of approach dependent on patient characteristics and family preference. We Pre-operative GMFCS Level 2.11, p=0.035). The degree of change did not analyzed differences in functional outcomes and complications between these surgical I 10 (16.7%) statistically differ between surgical techniques II 15 (25%) techniques and report on two cases of spinal cord tethering after SDR as a never III 18 (30%) (t(52)=1.325, p=0.191). reported complication of this procedure. IV 3 (5%) • Statistically significant reduction in MAS post- V 11 (18.3%) operatively from pre-operative MAS for all Methods Type of Surgery muscle groups other than peroneals (left Z=- At Exit Foramina 43 (71.7%) 1.725, p=0.084 and right Z=-1.802, p=0.072) • IRB approved retrospective chart review was performed of all patients who underwent Conus Medullaris 17 (28.3%) and hip flexors (left Z=-1.342, p=0.18 and right SDR at Children’s Hospital of Colorado from November 2009 through November Z=-1.604, p=0.109). 2020 Table 3. Complication Rates by Surgical Procedure after Selective Dorsal Rhizotomy At Conus Medullaris At Exit Foramina Complication n (%) n (%) Neuropathic Pain 8 (47%) 4 (9.3%) Spinal Cord Tethering 2 (11.7%) 0 (0%) Infection 2 (11.7%) 4 (6.9%) CSF Leak 0 (0%) 3 (6.9%) Lower Extremity Weakness 2 (11.7%) 6 (13.9%) Numbness 0 (0%) 3 (6.9%) Other 3 (17.6%) 11 (25.5%) Spinal Deformity 2 (11.7%) 11 (25.5%)

Case Reports Complications: • Statistical association between surgical technique and postoperative neuropathic pain Figure 1 after sectioning below the conus (8/17 patients) versus by the root sleeves (4/43 patients, p=0.002). • No statistical association between surgical technique and urinary retention (p=1.00), urinary incontinence (p=0.652), constipation (p=0.725), fecal incontinence (p=0.069) or aggregated complications (p=0.712). • Ten patients had new minor spinal deformity while 3 patients had mild worsening of their pre-operative deformity. • No significant association between surgical procedure and infection (p=0.616), CSF leak (p=0.551), lower extremity weakness (p=1.00), numbness (p=0.551), spinal cord tethering (p=0.077), spinal deformities (p=0.614), or other complications (p=0.737).

Conclusions • SDR does improve GMFCS level and MAS functional outcomes in patients. Yet, there is no increased efficacy in spasticity reduction or functional improvement for one surgical technique over the other. • Minimal and often transient bowel and bladder complications post-operatively with no significant association to a particular surgical technique. • Post-operative complications of infection, CSF leak, lower extremity weakness, numbness, spinal cord tethering and ‘other’ demonstrated no difference between surgical technique. • The only complication that demonstrated a significant association with a surgical technique was neuropathic pain, which was more frequent with rootlet dissection just below the conus medullaris. This may be due to increased spinal cord manipulation intra- operatively. References • As far as we can tell this is the first time clinical spinal cord tethering has been reported 1. Mittal S, Farmer J-P, Al-Atassi B, Gibis J, Kennedy E, Galli C, Courchesnes G, Poulin C, Cantin M-A, Benaroch TE (2002) Long-term functional outcome after selective posterior rhizotomy. Journal of Neurosurgery 97: 315 as a complication of SDR 2. Park TS, Gaffney P, Kaufman B, Molleston MC. Selective lumbosacral dorsal rhizotomy immediately caudal to the conus medullaris for cerebral palsy spasticity. Neurosurgery 33:929-934, 1993. 3. Peacock WJ, Arens LJ. Selective posterior rhizotomy for the relief of spasticity in cerebral palsy. S Afr Med J 62:119-124, 1982. 4. Duffy EA, Hornung AL, Chen BP-J, Munger ME, Aldahondo N, Krach LE, Novacheck TF, Schwartz MH (2021) Comparing short-term outcomes between conus medullaris and cauda equina surgical techniques of selective dorsal rhizotomy. Developmental Medicine & Child Neurology 63: 336-342