NIRS-based in vivo assessment of skeletal muscle metabolism in young adults with cerebral palsy: an exploratory pilot study
Authors: Adami Alessandra , Porcelli Simone , Kfoury Mary Joy , Neri Marianna , Bertucco Matteo 
Published: May 2023

Individuals with mild cerebral palsy (CP) have ~32% higher energy cost of walking compared to typically developing (TD) peers ( Nardon et al., 2021). In CP, the ability to walk is limited by poor body movement coordination and an early onset of neuromuscular fatigue. Analyzes of gracilis muscle biopsy in children with CP demonstrated a preserved mitochondria content but a 50-80% reduced maximal muscle mitochondrial complexes activity compared to TD ( Dayanidhi et al., 2021), suggesting the latter being an additional factor explaining the early onset of fatigue during ambulation. A novel near-infrared spectroscopy (NIRS) based approach, validated against muscle biopsy (r2=0.46; Ryan et al., 2014), allows non-invasive, in vivo determination of the skeletal muscle mitochondrial oxidative capacity ( k). We therefore aimed to evaluate the use of the NIRS-based protocol in young adults with CP; and to compare CP with TD peers. Methods: Four young men with CP (age: 24.4 ±2.6 yrs, BMI: 24.1 ±2.8 kg/m2) and four age- and sex-matched TD (age: 24.3 ±3.2 yrs, BMI: 23.8 ±1.5 kg/m2) took part in this ongoing study. Moderately active (IPAQ questionnaire) CP participants with stable motor function impairment level II-III of the Gross Motor Function Classification System were included. Exclusion criteria: epilepsy episode and/or botulinum toxin injection in the past 6mo; surgery in the past 36mo. Medial gastrocnemius muscle (chosen as representative locomotor muscle) k was measured twice by NIRS combined with intermittent arterial occlusions, after 10-15s of muscle activation. Reproducibility was determined by coefficient of variation (CV) and interclass correlation coefficient (ICC). Paired t test was used to compare groups (CP vs TD). Results: Test-retest CV (and ICC) was 9.5±7.5% (ICC=0.66) in CP and 6.2±3.5% (ICC=0.94) in TD. In the CP group, the within-subject reproducibility was large (CV range 0.4-17.0%). Resting muscle tissue saturation was within normal ranges in both groups (CP: 70.8±2.2%, CON: 66.1±6.9; p=0.35). Young adults with CP had ~37% lower k compared to TD (CP: 1.03±0.06 min-1, CON: 1.64±0.54 min-1) but this study is yet underpowered to draw solid conclusions (p=0.09). Discussion: Test-retest reliability of k in people with CP was lower than previously reported in other populations (CV ~10%; Adami & Rossiter, 2018). Adding a third repeat for measuring k is recommended to improve sensitivity. Our pilot data showed ~37% lower k in the calf muscle in young adults with CP compared to TD peers, a similar loss seen in middle-age COPD (GOLD class 3-4) and multiple sclerosis patients, who also report easy fatigability during walking. Further studies in a larger group of individuals are needed to confirm NIRS-based muscle oxidative capacity as a potential clinical marker in CP, and to assess its feasibility to correlate with different severity levels. Supported by Rhode Island Foundation 2801_20190604 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.