Muscle tone and pain in children with spastic cerebral palsy

AIM: To investigate associations between muscle tone measured using the Modified Ashworth Scale (MAS) and pain in children with spastic cerebral palsy (CP). METHOD: Children (aged 0-17 years; mean age 10 years 2 months) in the Norwegian Quality and Surveillance Registry for Cerebral Palsy with physical therapy assessments between 2018 and 2021 were included (n = 1188; 42.3% female) in this population-based cross-sectional study. Logistic regression analyses were used to examine the association between MAS scores and pain. Odds ratios (ORs) with 95% confidence intervals (CIs) were reported. RESULTS: Pain was experienced by 41.4% (n = 492). Risk of pain was highest in children classified in Gross Motor Function Classification System level V (OR = 1.81, 95% CI = 1.21-2.70) and Manual Ability Classification System level V (OR = 2.00, 95% CI = 1.25-3.16), children with bilateral spastic CP (OR = 1.34, 95% CI = 1.06-1.68) and increasing age (OR = 1.12, 95% CI = 1.09-1.15). Pain interfered with sleep in 24.8% (n = 122) of children and activities of daily living (ADLs) in 53.0% (n = 261) of children. An MAS score of 2 or greater was recorded in 42.3% (n = 502), most often in the ankle plantar flexors. Adjusted analyses showed that the highest MAS score was associated with pain interfering with ADLs (adjusted OR = 1.40, 95% CI = 1.00-1.96), and an MAS score of 2 or greater with higher pain intensity (adjusted OR = 1.2, 95% CI = 1.01-1.42). INTERPRETATION: Pain is common in children with spastic CP, frequently disrupting sleep and ADLs. Higher MAS scores are modestly associated with increased pain intensity and interference, highlighting the need for targeted pain screening strategies.