Does Chronic Pain Change Over Time in Children With Duchenne Muscular Dystrophy?

ssessed using the 7-item Pain Interference Scale of the Brief Pain Inventory (BPI). It evaluates how much pain interferes with 7 daily life domains (general activity, mood, walking ability, normal work, relations with others, sleep, and enjoyment of life) over the past 24 hours. Each item is rated on an 11-point numeric scale from 0 (does not interfere) to 10 (completely interferes). The total score ranges from 0 to 70, with higher scores indicating greater pain interference in daily functioning.

Assessed using the pediatric body diagram of the Adolescent Pediatric Pain Tool (APPT). Participants mark all anatomical regions where they experience pain. The total number of painful body areas is quantified, with higher numbers indicating more widespread pain.

Assessed using the word descriptor component of the Adolescent Pediatric Pain Tool (APPT), which evaluates 4 dimensions of pain quality: sensory, affective, evaluative, and temporal across a total of 15 words. Scores are calculated as percentages of selected words relative to the total number of words within each dimension (0% to 100%). Higher percentage scores indicate greater endorsement of that specific pain dimension.

Assessed using the Pediatric Pain Coping Inventory (PPCI, adolescent and parent-proxy versions). It measures coping strategies across 5 subscales: cognitive self-instruction, problem solving, distraction, seeking social support, and catastrophizing/helplessness. Items are scored on a 3-point Likert scale (0 = never, 1 = sometimes, 2 = often). Higher scores in each subscale indicate more frequent utilization of that specific coping strategy.

Assessed using the North Star Ambulatory Assessment (NSAA) in ambulatory participants. It evaluates 17 motor activities (such as standing, walking, rising from a chair, jumping, and running). Each item is scored on a 3-point scale: 0 (unable to achieve independently), 1 (achieves with modifications), and 2 (normal performance). Total raw scores range from 0 to 34, with higher scores reflecting better motor and functional capability.

Evaluated using the modified 6-Minute Walk Test (6MWT) according to standard DMD protocols in ambulatory participants capable of walking at least 75 meters. Total distance walked in 6 minutes is recorded in meters. A greater distance indicates better functional exercise tolerance.

Lower extremity function is evaluated using the Vignos Scale (grades 1 to 10, ranging from 1 = walks and climbs stairs without assistance to 10 = bedridden). Upper extremity function is evaluated using the Brooke Scale (grades 1 to 6, ranging from 1 = arms abducted in a full circle to touch above head to 6 = no useful hand function). For both scales, higher numerical scores indicate more severe functional disability.

Handgrip strength is measured bilaterally using an electronic hand dynamometer in kilograms (kg), recording the average and maximum of 3 trials. Proximal and distal muscle strength is assessed bilaterally using Manual Muscle Testing (MMT) with the Medical Research Council (MRC) scale (0 = no movement to 5 = normal strength). Total muscle strength is calculated as a composite percentage score (%MRC) using the standard formula: (Total score × 100) / (Number of tested muscles × 5). Higher values indicate greater muscle strength.

Timed performance to ascend and descend a standard 4-step flight of stairs is measured in seconds using a digital stopwatch. Shorter completion times indicate superior functional mobility and lower extremity motor velocity.

Passive joint range of motion (ROM) is measured in degrees using a standard goniometer across cervical, shoulder, elbow, wrist, metacarpophalangeal, hip, knee, and ankle joints. Contracture is defined as passive loss of full normal joint ROM compared to age-matched reference standards. Lower degrees of passive ROM indicate greater joint contracture severity.