Cine phase contrast magnetic resonance imaging of calf muscle contraction in pediatric patients with cerebral palsy and healthy children: comparison of voluntary motion and electrically evoked motion

The aim of this study is to investigate the feasibility of phase contrast imaging for assessment of muscle function in children with cerebral palsy. Time-resolved cine phase contrast MRI at 3T was synchronized with (a) electrical muscle stimulation (EMS) of the calf muscle and (b) voluntary plantarflexion following visual instructions. Fourteen ambulatory pediatric patients with equinus and 13 normally developing, healthy children were scanned. Ten patients were scanned pre and post botulinum toxin treatment. Four patients and four healthy children performed voluntary plantarflexion additionally to EMS. The achieved force was higher for the voluntary task for both patients and healthy controls, but its periodicity was worse compared to the stimulated contraction in patients. Therefore, it was possible to acquire contraction velocity time courses showing two distinct velocity peaks – the first for voluntary muscle contraction and the second for release – in four out of four healthy controls but in none of the patients. During EMS, two distinct velocity peaks could be resolved if the tolerated current was high enough to evoke sufficient contraction. That was achieved in 21% of the scans in patients (15 out of 72 scans during EMS in total) compared to 82% (14 out of 17) in healthy children. Then, the data quality was sufficient to generate strain maps. However, it was not possible to detect an effect of botulinum toxin in these patients since we did not succeed in acquiring data with sufficient quality both pre- and post-treatment. In conclusion, both EMS and voluntary motion worked well in healthy, normally developing children. Compliance was higher for the voluntary task for both patients and healthy controls. In conclusion, it was necessary to use EMS for a successful measurement of contraction/release velocity and strain in CP patients and although in this cohort the results were inconclusive, in the future optimization of the stimulation protocol could increase the acceptance and improve the output. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by the Swiss National Science Foundation (http://www.snf.ch/; grant number 173292). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Ethikkommission Nordwest- und Zentralschweiz gave ethical approval for this work (EKNZ BASEC 2016-01408). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All relevant data are within the manuscript and its Supporting Information files.