Background & Aims
Quantitative sensory testing (QST) is a standardized approach assessing sensory function, with studies demonstrating individual sensory profiles within neuropathic pain groups.1 Conventional QST is not feasible for many individuals with developmental disabilities (DD), however, due to limited self-report. Investigations into the relation between pain and sensory function in cerebral palsy, a DD with known chronic pain burden,2 is limited. We previously demonstrated the feasibility of a modified QST (mQST) that does not rely on self-report by applying calibrate tactile stimuli for consistent durations and scoring observable behavioral reactivity (e.g. brow furrow) during application in CP.3 The purpose of this study was to extend the use of this mQST to explore potential relations between behavioral reactivity to the sensory stimuli and individual factors, such as chronic pain status, in a pediatric sample of individuals with CP.
Methods
Participants with a diagnosis of CP and aged 5-21 years were identified from clinic visits at Gillette Children’s and recruited using stratified random sampling on CP type. This sample included 117 participants with scored mQSTs. Health history and pain status were collected via medical records and proxy-report. Tactile stimuli were applied to the calves: sham, light touch, pin, cool, pressure, repeated von Frey (60g), and heat.3 Behavioral reactivity (BR) of the face, limb of application, whole body, and vocals during application times was scored using a modified FLACC.4 BR scores on each calf were averaged by stimulus. We conducted a linear mixed model with sex, age, gross motor function, seizures, chronic pain status, and number of previous surgeries as predictors of BR for each stimulus using backwards elimination and AIC comparisons. A k means cluster analysis was also conducted using z-scored BR to assess preliminary sensory profiles.1
Results
Participants’ mean age was 12.0 (SD= 4.9), 46.6% were female, and 79.4% were White/Caucasian. Eighty-eight (75%) of caregivers reported chronic pain in their child. The final model included main effects for stimulus type on average BR and interaction effects for stimulus by gross motor function, sex, and age, particularly for the repeated von Frey application. BR was higher for all stimuli compared to sham. Chronic pain and surgical history were not significant but contributed to lower model AIC. Cluster analyses resulted in a hyporeactive, hyperreactive, and a thermal hyperactive group.
Conclusions
This study identified several individual factors that may impact sensory experiences in CP and that those factors may have differential impacts based on the stimulus type. The inclusion of chronic pain contributed to lower model AIC, indicating pain is predicting some aspect of the sensory experiences to the mQST. Initial clusters also indicated distinct response profiles across stimuli, similar to the profiles seen in other studies in chronic pain populations.1 While mQST does establish thresholds of sensory gain/loss as does conventional QST, this direct sensory assessment tool may still advance our understanding of towards stratified treatment approaches to improve quality of life in CP. This work was supported by NIH grant no. HD102552.
References
1Baron F, Förster M, Binder A. Subgrouping of patients with neuropathic pain according to pain-related sensory abnormalities: a first step to a stratified treatment approach. Lancet Neurol 2012;11: 999–1005.
2.Brunton L, Hall S, Passingham A, Wulff J, Delitala R. The prevalence, location, severity, and daily impact of pain reported by youth and young adults with cerebral palsy. J Pediatr Rehabil Med 2016;9(3):177–83.
3.Barney (Burkitt) C, Merbler A, Simone D, Walk D, Symons F. Investigating the Feasibility of a Modified Quantitative Sensory Testing Approach to Profile Sensory Function and Predict Pain Outcomes Following Intrathecal Baclofen Implant Surgery in Cerebral Palsy. Pain Med 2020;21(1):109-17.
4Voepel-Lewis T, Shayevitz J, Malviya S. The FLACC: a behavioral scale for scoring postoperative pain in young children. Pediatr Nurs 1997;23(3): 293-297.