Neuropathic pain in children: Case

This girl has complex regional pain syndrome of the right lower limb, complicated by opioid escalation, functional decline, and a fixed dystonic posture. Her pain is disproportionate to a minor injury that has long since healed, and she has the full clinical picture: allodynia in the flinching from light touch and the provocation by the bedclothes and the shower water, hyperalgesia in the burning quality, vasomotor and sudomotor change in the cool, swollen, dark-red foot, and a motor change in the fixed dystonic posture of the toes. The Mesaroli five-year review establishes that complex regional pain syndrome predominates in adolescent girls, affects the lower limb, and is accompanied by a movement disorder such as dystonia in a significant minority, and this girl fits that picture exactly. Her management has gone wrong in the directions that most often cause harm: immobilisation through rest and a compression bandage, and opioid escalation. The task now is to reverse both and to build the rehabilitation plan that should have been the foundation from the outset. ^[9]

Confirming the diagnosis and excluding dangerous alternatives

The first task is to confirm the diagnosis and exclude the dangerous alternatives. The diagnosis of complex regional pain syndrome is clinical, built on regional pain disproportionate to an inciting event, accompanied by sensory, vasomotor, sudomotor, and motor changes, and this girl has each of these. On the NeuPSIG grading system her pain is at least possible neuropathic pain, with a neuroanatomic distribution in the affected limb and a plausible injury. ^[1]

The most important alternative to exclude is infection, because a warm, swollen, painful limb in a febrile or unwell child is septic arthritis or osteomyelitis until proven otherwise. This girl is afebrile and well, and her inflammatory markers and full blood count are normal, which makes infection unlikely, but the exclusion is documented actively rather than assumed. A structural lesion of the nervous system is excluded by the red-flag screen: there is no progressive pain, no focal deficit, no sphincter disturbance, and no systemic features, and the neurological examination is normal, so urgent magnetic resonance imaging is not required. The fixed dystonic posture is the movement disorder of complex regional pain syndrome rather than a primary neurological lesion, and the diagnosis is secure. ^[9]