title: The effects of botulinum toxin injection frequency on calf muscle growth in young children with spastic cerebral palsy: a 12-month prospective study.
abstract: OBJECTIVE
  This study was a 12-month prospective investigation of changes in the medial gastrocnemius (MG) muscle morphology in children aged 2-5 years with spastic cerebral palsy (CP) who had received no previous intramuscular injections of botulinum neurotoxin type-A (BoNT-A) and were randomised to receive either single or multiple (three) BoNT-A injections to the gastrocsoleus. MG morphological changes were compared to age-matched typically developing (TD) peers.
  
  
  METHODS
  Thirteen children with spastic CP with a mean age of 45 (15) months and 18 TD children with a mean age of 48 (14) months participated in the study. The principal outcome measures were MG muscle volume, fascicle length, pennation angle and physiological cross-sectional area (PCSA), which were obtained using 2D and 3D ultrasound.
  
  
  RESULTS
  The single and multiple injection frequency groups significantly increased MG muscle volume at 12 months relative to the baseline by 13 and 15 %, respectively. There were no significant differences in the MG muscle volume 28.5 (12.3) versus 30.3 (3.8) ml, fascicle length 48.0 (10.4) versus 44.8 (1.2) mm or PCSA 7.0 (1.2) versus 6.6 (1.7) cm(2) between the single and multiple injection groups, respectively, at 12 months follow-up. The change in MG muscle volume in the single and multiple injection groups was significantly lower than the TD peers by 66 and 60 %, respectively.
  
  
  CONCLUSIONS
  In young children with spastic CP, naive to BoNT-A treatment, MG muscle growth over 12 months does not appear to be influenced by intramuscular BoNT-A injection frequency. However, MG muscle growth in the spastic CP groups was significantly lower than the age-matched TD peers. It is unclear whether this is an effect of intramuscular BoNT-A injections or reduced growth rates in children with spastic CP in general. Controlled investigations and longitudinal studies with multiple measurement time points are required in order to determine the influence of BoNT-A treatment on muscle physiological and mechanical growth factors in young children with spastic CP.
authors.affiliation: Queensland Cerebral Palsy and Rehabilitation Research Centre, School of Medicine, The University of Queensland, Herston, QLD 4029 Australia.
authors.forename: Lee
authors.initials: L
authors.lastname: Barber
authors.affiliation: Hugh Williamson Gait Laboratory, The Royal Children's Hospital, Melbourne, VIC 3052 Australia ; Murdoch Childrens Research Institute, The Royal Children's Hospital, Melbourne, VIC 3052 Australia.
authors.forename: Tandy
authors.initials: T
authors.lastname: Hastings-Ison
authors.affiliation: Centre for Health, Sport and Rehabilitation Sciences Research, School of Health Sciences, University of Salford, Manchester, M5 4WT UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Baker
authors.affiliation: Hugh Williamson Gait Laboratory, The Royal Children's Hospital, Melbourne, VIC 3052 Australia ; Murdoch Childrens Research Institute, The Royal Children's Hospital, Melbourne, VIC 3052 Australia ; The University of Melbourne, Melbourne, VIC 3010 Australia.
authors.forename: H
authors.initials: H
authors.lastname: Kerr Graham
authors.affiliation: Centre for Musculoskeletal Research, Griffith Health Institute and School of Rehabilitation Sciences, Griffith University, Southport, QLD 4222 Australia.
authors.forename: Rod
authors.initials: R
authors.lastname: Barrett
authors.affiliation: The School of Human Movement Studies, The University of Queensland, St Lucia, QLD 4072 Australia.
authors.forename: Glen
authors.initials: G
authors.lastname: Lichtwark
keywords: Botulinum neurotoxin type-A; Cerebral palsy; Medial gastrocnemius; Muscle volume; Physiological cross-sectional area; Ultrasound