Background~Children with SNI may experience nociceptive-inflammatory pain as a result of their specific medical condition or procedures. Often, however, it is not clear what underlies the pain behavior as there is no clear inciting noxious event. The investigators define this entity of pain without an obvious source as Pain and Irritability of Unknown Origin (PIUO).~The investigators' work to date has developed an efficient, focused clinical pathway to evaluate children with SNI for all potential sources of nociceptive-inflammatory pain. Using this approach the unknown element of pain in these children is reduced and a source of PIUO may be found in individual cases, increasing the potential for treatment. Nevertheless there are children, who at the end of a thorough evaluation guided by a clinical pathway, will still have PIUO. These children may benefit from adjuvant analgesics such as gabapentin.~The evidence base supporting the use of gabapentin for pain and irritability in infants and children with neurological impairment rests on case series publications describing a limited number of retrospective cases. The lack of prospective, randomized studies, even for this commonly used medication, underpins the rationale for this trial.~Objectives~The primary objective of the pilot trial is to evaluate the clinically significant difference of gabapentin to decrease pain and irritability in children with SNI, when the source of pain and irritability is attributed to neurological dysregulation (nociplastic pain), as measured by parent-reported pain scores.~The investigators will compare the gabapentin versus placebo along an escalating dose range for both individual subjects and for the group. The investigators will aggregate the results of the completed N-of-1 trials across all subjects to estimate the group level comparative effectiveness of gabapentin in reducing pain and irritability.~Outcomes from this study will help with designing larger randomized control trials, especially with sample size and power calculations. It will also provide prospective information on drug effect.~Trial Design~This trial uses a single randomized multiple-measures cross-over design (N-of-1), with results aggregated over several subjects. This design is well-suited to outcomes that are highly specific to each individual and not amenable to precise measurement across a large cohort. The heterogenous nature of pain and irritability responses in children are more likely to be personally specific and characteristic, rather than generalizable.~Subjects will switch between gabapentin (G) and placebo (P) in a randomized order. The sequence of whether G precedes P (GP) or P precedes G (PG) will be randomized by the study pharmacist, and neither the clinician nor the subject (parent/caregiver) will know the sequence. Each subject will serve as their own control and experiment, allowing for a finer assessment of the treatment efficacy within each patient.~The primary variable assessed is the child's pain score. Pain and irritability will be measured using the Non-Communicating Children's Pain Checklist - Revised (NCCPC-R) at specified intervals throughout the randomized sequence of G : P. Additional measures of parent/caregiver burden and impact on their daily function will be undertaken weekly with the PROMIS-57, a tool adapted to measure the impact of the child's pain and irritability on parental functioning. Other measures will be of usual, known side effects (e.g., sedation) and of any unexpected adverse events.
Children born with severe brain-based developmental disabilities frequently experience persistent unexplained periods of pain and irritability, often compounded by a limited capacity to communicate their distress. The investigators call this entity Pain and Irritability of Unknown Origin (PIUO). The rationale of this trial is to identify the clinical effect size of gabapentin in reducing and resolving pain in children with developmental brain disorders, specifically those with severe neurological impairment (SNI).