Temporal but Not Spatial Variability during Gait Is Reduced after Selective Dorsal Rhizotomy in Children with Cerebral Palsy

Introduction Variability in task output is a ubiquitous characteristic that results from non-continuous motor neuron firing during muscular force generation. However, variability can also be attributed to errors in control and coordination of the motor neurons themselves in diseases such as cerebral palsy (CP). Selective dorsal rhizotomy (SDR), a neurosurgical approach to sever sensory nerve roots, is thought to decrease redundant or excessive afferent signalling to intramedullary neurons. In addition to its demonstrated ability to reduce muscular spasticity, we hypothesised that SDR is able to decrease variability during gait, the most frequent functional motor activity of daily living. Methods Twelve CP children (aged 6.1±1.3yrs), who underwent SDR and performed gait analysis pre- and 12 months postoperatively, were compared to a control group of eleven typically developing (TD) children. Coefficients of variability as well as mean values were analysed for: temporal variables of gait, spatial parameters and velocity. Results Gait parameters of cadence (p = 0.006) and foot progression angle at mid-stance (p = 0.041) changed significantly from pre- to post-SDR. The variability of every temporal parameter was significantly reduced after SDR (p = 0.003–0.049), while it remained generally unchanged for the spatial parameters. Only a small change in gait velocity was observed, but variability in cadence was significantly reduced after SDR (p = 0.015). Almost all parameters changed with a tendency towards normal, but differences between TD and CP children remained in all parameters. Discussion The results confirm that SDR improves functional gait performance in children with CP. However, almost exclusively, parameters of temporal variability were significantly improved, leading to the conjecture that temporal variability and spatial variability may be governed independently by the motor cortex. As a result, temporal parameters of task performance may be more vulnerable to disruption, but also more responsive to treatment success of interventions such as SDR.ISSN:1932-620

Correction: The Effects of Selective Dorsal Rhizotomy on Balance and Symmetry of Gait in Children with Cerebral Palsy.

[This corrects the article DOI: 10.1371/journal.pone.0152930.]

The Effects of Selective Dorsal Rhizotomy on Balance and Symmetry of Gait in Children with Cerebral Palsy.

AIM:Cerebral palsy (CP) is associated with dysfunction of the upper motor neuron and results in balance problems and asymmetry during locomotion. Selective dorsal rhizotomy (SDR) is a surgical procedure that results in reduced afferent neuromotor signals from the lower extremities with the aim of improving gait. Its influence on balance and symmetry has not been assessed. The aim of this prospective cohort study was to evaluate the impact of SDR on balance and symmetry during walking. METHODS:18 children (10 girls, 8 boys; age 6 years (y) 3 months (m), SD 1y 8m) with bilateral spastic CP and Gross Motor Function Classification System levels I to II underwent gait analysis before and 6 to 12 months after SDR. Results were compared to 11 typically developing children (TDC; 6 girls, 5 boys; age 6y 6m, SD 1y 11m). To analyse balance, sway velocity, radial displacement and frequency were calculated. Symmetry ratios were calculated for balance measures and spatio-temporal parameters during walking. RESULTS:Most spatio-temporal parameters of gait, as well as all parameters of balance, improved significantly after SDR. Preoperative values of symmetry did not vary considerably between CP and TDC group and significant postoperative improvement did not occur. INTERPRETATION:The reduction of afferent signalling through SDR improves gait by reducing balance problems rather than enhancing movement symmetry

Participants’ demographic, anthropometric and clinical data.

<p>Legend: Due to normally distributed values, all parameters were presented as a mean (±standard deviation); pre = preoperative, post = 12 months postoperative, TDC = typically developing children; yrs = years, m = male, f = female; GMFCS = Gross Motor Function Classification System; GMFM = Gross Motor Function Measure; MAS = Modified Ashworth Scale; Strength: measured on a 5 point scale.</p

CV of temporal parameters pre- and post-SDR compared to typically developing children (TDC).

<p>Levels of significance are shown for the children with CP between the preoperative and 12 months post-SDR therapy time points. All values are presented as medians, shown together with interquartile ranges as well as minimum and maximum values.</p

Marker set used throughout gait analyses.

<p>Written, informed permission was expressly provided by the legal guardian of the child shown to publication of their photograph, as outlined in the PLOS consent form.</p

Spatio-temporal parameters of kinematics, shown preoperatively and 12 months postoperatively.

<p>Legend: Due to partially non-normally distributed values, all general spatio-temporal parameters concerning SDR related changes are presented as a median together with interquartile range; TDC = typically developing children, pre = preoperative, post = 12 months postoperative; [%] = percentage of stride time or percentage of related gait cycle phase (swing phase), [°] = degree; [norm] = normalised; FPA = Foot progression angle: positive values represent externally rotated feet;</p>*<p> = significance with p<0.05 between pre and post SDR.</p

CV of spatial parameters pre- and post-SDR compared to typically developing children (TDC).

<p>Levels of significance are shown for the CP children between the preoperative and 12 months post-SDR therapy time points. All values are presented as medians, shown together with interquartile ranges as well as minimum and maximum values.</p

Changes of velocity related balance parameters.

<p>Paired samples t-test for normally distributed data; TDC = typically developing children, CP = cerebral palsy, SDR = selective dorsal rhizotomy, BL = bilateral, UL = unilateral, R = right, L = left, * p = 0.000, † p = 0.001, ‡ p = 0.002, # p = 0.004, £ p = 0.006, ¥ p = 0.007.</p