Neuropathic pain in children: Viva

Branch 1: Defining and grading the pain

The candidate should open by defining neuropathic pain as pain caused by a lesion or disease of the somatosensory nervous system, distinct from nociceptive pain (actual or threatened tissue damage) and nociplastic pain (altered nociception without a clear lesion). The distinction matters because neuropathic pain responds poorly to opioids and non-steroidal anti-inflammatory drugs and better to drugs that quieten nerve firing, such as gabapentinoids and tricyclic antidepressants, and because recognising the mechanism unlocks the rehabilitation and function-focused plan. The candidate should then apply the NeuPSIG grading system: this girl's pain has a plausible neuroanatomic distribution in the affected limb and a plausible injury, so it is at least possible neuropathic pain, and the clinical signs of allodynia, hyperalgesia, and sensory change support that grade. [1]

If the examiner presses on the grading steps, the candidate should name all three levels: possible neuropathic pain with a neuroanatomic distribution and a relevant history; probable neuropathic pain when a confirmatory test, such as neurophysiology or imaging, demonstrates the lesion; and confirmed neuropathic pain when a diagnostic test shows that the lesion explains the pain. The candidate should note that most paediatric consultations end at probable, and that this is sufficient to begin the neuropathic plan. A strong candidate adds that the bedside signatures are allodynia, hyperalgesia, and sensory loss, and that a child who flinches from the bedclothes is showing allodynia through behaviour. [1]

Branch 2: The diagnosis and excluding dangerous alternatives

If asked for the diagnosis, the candidate should state complex regional pain syndrome of the right lower limb and justify it: severe regional pain disproportionate to a minor injury that has healed, with allodynia, hyperalgesia, colour and temperature change, swelling, and the cool, pale limb of autonomic dysregulation. The candidate should cite the Mesaroli five-year review, which establishes that complex regional pain syndrome predominates in adolescent girls and affects the lower limb, and should note that a movement disorder such as dystonia is present in a significant minority. [9]

The examiner will press on what else it could be, and the candidate must name and exclude the dangerous alternatives. The first is infection: a warm, swollen, painful limb in a febrile or unwell child is septic arthritis or osteomyelitis until proven otherwise, and complex regional pain syndrome is a diagnosis of exclusion that must never be made in the face of fever or systemic illness. This girl is afebrile and well with normal inflammatory markers, which makes infection unlikely, but the candidate should document the exclusion actively. The second is a structural lesion of the nervous system: a tumour compressing a nerve or the spinal cord, an occult syrinx, or a compressive lesion can present as neuropathic pain before other signs, and the red-flag screen, progressive pain, focal deficit, sphincter disturbance, and systemic features, must be negative. This girl's screen is negative and her examination is normal, so urgent imaging is not required. The cool, pale limb is the autonomic change of complex regional pain syndrome, not vascular insufficiency. [9]

A strong candidate distinguishes complex regional pain syndrome from a straightforward peripheral nerve injury and from central neuropathic pain, and notes that nerve conduction studies are reserved for confirming a peripheral nerve lesion rather than for diagnosing complex regional pain syndrome, which remains a clinical diagnosis. [1]

Branch 3: Building the rehabilitation-first plan

If asked how to manage this girl, the candidate should build the plan in a stepped sequence that begins with what is not a drug. The foundation is an intensive, function-focused exercise-based rehabilitation programme, and the candidate should cite the Sherry series, which demonstrated excellent short- and long-term outcomes for children with complex regional pain syndrome treated with exercise therapy. The candidate should state that immobilisation is avoided because it deepens the disuse and sensitisation, and that graded desensitisation, weight-bearing, and functional exercise retrain the nervous system. A clear, mechanism-based explanation, that the nerve is misfiring and the brain has turned up the gain, is itself therapeutic. [6]

The candidate should add cognitive behavioural therapy and psychological support as core treatments, because complex regional pain syndrome is accompanied by anxiety, low mood, sleep disturbance, and school absence, and these amplify the nervous system's gain. The goal is a return to function and school rather than the abolition of pain, and a validated paediatric pain and quality-of-life measure tracks the response. The candidate should state that a child with significant disability, school refusal, or a movement disorder is referred early to a tertiary paediatric pain service for intensive multidisciplinary input. [9]

A strong candidate confronts the harmful reflex directly: the single most damaging response to complex regional pain syndrome is to escalate opioids, because neuropathic pain responds poorly to opioids and the doses required carry a high risk of dependence, sedation, and opioid-induced hyperalgesia. The candidate should state that opioids have no place in the routine management of this girl and that the rehabilitation plan is built instead. [9]

Branch 4: The role of gabapentin and amitriptyline

If asked about the role of pharmacotherapy, the candidate should position drugs as adjuncts to the rehabilitation and psychological plan, used when the pain is severe enough to limit participation in the exercise programme. Gabapentin is the gabapentinoid most often used first, and the candidate should give the dosing: start low at about 10 mg per kg per day in divided doses, titrate over one to two weeks from once to twice to three times daily toward a usual effective range of 25 to 35 mg per kg per day in three divided doses, reduce in renal impairment, and never stop abruptly, tapering over at least a week because abrupt withdrawal can cause seizures. Monitoring is for sedation, dizziness, ataxia, and behavioural change. [3]

The candidate should give the amitriptyline dosing if asked: start at 0.1 to 0.2 mg per kg at night, titrate over two to three weeks to a maximum of about 0.5 to 1 mg per kg per day, with a baseline electrocardiogram because tricyclics prolong the QT interval, withholding and consulting cardiology if the QTc is prolonged, and repeating the ECG after dose increases or if palpitations or syncope occur. The anticholinergic effects and morning sedation are the dose-limiting effects. [4]

A fellowship-level candidate must confront the evidence base directly. The 2017 Cochrane review by Cooper and colleagues found insufficient evidence to determine the efficacy and safety of antiepileptic drugs, including gabapentin, for chronic non-cancer pain in children, and a parallel review found the same paucity of evidence for antidepressants. The GABA-1 trial by Kaguelidou and colleagues was established precisely because gabapentin was used off-label without reliable evidence. The realistic position is that gabapentin and amitriptyline are plausible adjuncts borrowed from the stronger adult evidence, used cautiously with monitoring, off-label, and judged on function rather than pain intensity alone. The candidate should close by reaffirming that the goal is a return to function and school, that the prognosis with early intensive rehabilitation is excellent, and that any drug is weaned once that goal is met. [3]