A Pilot Study of Sensation, Allodynia, and Pain in Children with Brachial Plexus Birth Injury
Kristen M Davidge, MD, MSc, FRCS(C)1, Emily S Ho, PhD2 and Howard M. Clarke, MD, PhD, FRCS(C)3, 1The Hospital for Sick Children, Toronto, ON, Canada, 2Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada, 3Division of Plastic and Reconstructive Surgery, Hospital for Sick Children, Toronto, ON, Canada
Introduction: The etiology of pain in children with brachial plexus birth injury (BPBI) is unknown. The objectives of this study were to: 1) determine whether clinical signs of neuropathic pain (allodynia, hyperalgesia) are present in children with BPBI; 2) define sensory recovery proximal to the wrist; and, 3) explore whether a relationship exists between signs of neuropathic pain, sensory recovery, and subjective pain descriptors.
Methods: A cross-sectional pilot study was performed of children with unilateral BPBI, aged 8 to 19 years, reporting pain in their affected upper limb on the Adolescent Pediatric Pain Tool. Participants completed a clinical assessment of sensation (Weinstein Enhanced Sensory Test), allodynia (soft brush), and hyperalgesia (pinprick) in 14 peripheral nerve dermatomes of both upper limbs. Data were analyzed descriptively.
Results: Fourteen children with BPBI (9-19y, 10 right-affected, 7 operated) participated. All but one child used their unaffected upper limb as their dominant hand. Pain was most frequently located in the shoulder, elbow, and hand, with intensity ranging from 13-79. Proximal to the wrist, sensory thresholds were variable in both unaffected and affected extremities. Discordant sensory thresholds between limbs were found in 80 of 196 paired dermatomes, 58 of which had the higher threshold on the affected upper limb. Allodynia was present in 10 children and 43 of 196 paired dermatomes (17 bilateral). More children with total plexus palsies reported allodynia than those with upper plexus palsies. In 45% of dermatomes with allodynia, sensory thresholds > 2.83 were present. Presence of allodynia did correlate with selection of neuropathic pain descriptors, but no consistent pattern was found between areas of pain, allodynia, and sensory loss. Pinprick hypersensitivity was found in all children and dermatomes, with no discernable pattern.
Conclusions: 1) Clinical signs of neuropathic pain (allodynia) were present in children with BPBI, and appeared more common and severe in children with total plexus palsies. 2) Pinprick hypersensitivity was not a reliable test in the study population. 3) The relationship between allodynia, sensation, and self-report descriptors needs further study. 4) Normative sensory data proximal to the wrist is needed.
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