The size and echogenicity of the tibialis anterior muscle is preserved in both limbs in young children with unilateral spastic cerebral palsy

Abstract

Purpose

The primary of this study was to compare the volume, length, echo intensity, and growth rate of the medial gastrocnemius (MG) and tibialis anterior (TA) muscle of both limbs (more-involved and less-involved) in children with unilateral spastic cerebral palsy (USCP), with those of an age-matched typically developing (TD) group. A secondary aim in the USCP group was to explore the associations between these muscle parameters and discrete ankle positions during phase of gait.

Methods

Muscle parameters were assessed using 3D ultrasound. Maximal ankle dorsiflexion in stance and swing during walking were determined from 2D video analysis. Group differences in muscle size and echo intensity were assessed using a two-way analysis of covariance (age-by-group), with the interaction term used to compare muscle growth rates. Associations between muscle parameters and maximal ankle dorsiflexion in stance and swing were assessed using backwards multiple linear regression analyses.

Results

The MG of both limbs in children with USCP had signs of impaired muscle development (smaller volume and length, higher echo intensity and lower growth rate). There was no evidence of impaired muscle development of TA between limbs or compared the TD children. Tibialis anterior volume, length, echo intensity and MG volume explained 66% and 83% of the variance in maximal ankle dorsiflexion position in the stance and swing phases of walking, respectively.

Conclusions

Unlike the MG, the TA volume and growth rate in children with USCP are equivalent between limbs and compared to TD children. For the more-involved limb only, TA volume, length, and echo intensity appear associated with maximal ankle dorsiflexion during walking and represent important muscle parameters that could be targeted in with early exercise therapy.

Implications for rehabilitation

• Tibialis anterior (TA) size and echogenicity appear normal in both limbs in young children with unilateral spastic cerebral palsy (USCP); findings that could indicate sufficient mechanical stimulus and muscle anabolism to maintain normal muscle growth.

• Tibialis anterior size and echogenicity are associated with maximal ankle dorsiflexion in both stance and swing phase of walking in young children with USCP; though such relations appear isolated to the more-involved limb.

• Early therapeutic interventions that target TA are likely to be successful in maintaining muscle size and may offset the negative effects of medial gastrocnemius atrophy in the development of fixed ankle equinus of the more-involved limb and improve ankle positioning during gait.

Keywords:

• Gastrocnemius
• muscle quality
• echo intensity
• ultrasonography
• muscle growth

Acknowledgements

The authors acknowledge the staff of the Queensland Children’s Motion Analysis Service and the Queensland Paediatric Rehabilitation Service, Children’s Health Queensland Hospital and Health Service for their assistance with participant recruitment and patience throughout the study.

Disclosure statement

The authors report no conflicts of interest.

Additional information

Funding

This work was supported by a National Health and Medical Research Centre Partnership Grant and Centre for Research Excellence; a Cerebral Palsy Alliance Research Foundation AVANT Innovative Research Grant; and a CQUniversity New Staff Research Grant. Lee Barber is supported by a National Health and Medical Research Council Early Career Fellowships and Physiotherapy Research Fellowship, Health and Medical Research, Preventive Health Unit, Department of Health, Queensland. Felicity Read is supported by a National Health and Medical Research Council Researcher Fellowship. Reuben Bickell and Kaysie Florance were supported by a CQUniversity Summer Research Scholarship.