Pain in adults with cerebral palsy: measuring the contribution of spasticity JONATHAN M C SMITH | THALIA S FIELD Vancouver Stroke Program, Division of Neurology, University of British Columbia, Vancouver, British Columbia, Canada. doi: 10.1111/dmcn.14396 This commentary is on the original article by Flanigan et al. on pages 379–385 of this issue. Pain is highly prevalent in cerebral palsy (CP), 1 and as more individuals with the disorder are surviving into adulthood, the contributions to pain may become more complex. All individuals, including those with CP, face an increased likeli- hood of degenerative musculoskeletal issues with age. CP is also associated with an increased prevalence in adulthood of other chronic health conditions that can be associated with pain, including diabetes and cardiovascular disease. 2 In adults with CP, pain influences both function and health- related quality of life. 3 Thus, elucidating targets for interven- tion is of particular value in this population. In their study, Flanigan et al. 4 aimed to characterize the association between spasticity and pain measures in a cohort of adults with CP. The authors examined correlations between self- or care- giver-rated pain (using the Brief Pain Inventory and the Patient-Reported Outcome Measure Information Sys- tem [PROMIS] pain interference measures) and spasticity (evaluated using the self-rated Penn Spasm Frequency Scale [PSFS]; a physician-rated composite score of the Modified Ashworth Scale for hypertonia at elbow and wrist flexors and knee extensors; and the Tardieu scale for velocity-dependent tone for the same muscle groups). Spasm frequency, and not the clinical scales, were most highly correlated with pain sever- ity and interference. Interestingly, there were no significant differences in pain measures by Gross Motor Function Classi- fication System (GMFCS) level, nor did pain interference scores differ from historical rates for the general population. This study should be considered as hypothesis-generat- ing. The cohort of 47 is small, and there is responder bias: data were collected from individuals participating in a lar- ger study on nutrition and activity in adults with CP, and not as part of a routine medical record. Participants were linked with structured, multidisciplinary care and, thus, issues related to pain interference and social isolation, which can further compound these problems, were likely to have been optimized. Further, 15% of responses were from caregiver proxies. Finally, correlation does not equate to causation. The directionality of the relationship may modulate, and multiple other comorbid issues that can contribute to both pain and spasticity will need to be iden- tified to better understand the nature of the relationship. Still, the work provides a framework for considering future research examining spasticity and pain in adults with CP. The study highlights both the value of patient-reported measures in characterizing spasticity and pain in this popula- tion, and considerations for interpreting these measures. First, individuals with CP, including the majority of the study cohort, are likely to have surgical histories or are using phar- macological treatments that may affect or confound tradi- tional clinical measures of spasticity. Thus, a measure such as the PSFS may be more telling of whether spasticity is truly well-controlled. Next, pain interference was consistent across functional levels representing wide degrees of objective dis- ability, which underscores the different ways in which pain may affect individuals across all GMFCS levels. Another study examining pain in young adults with CP found no over- all differences in the magnitude of pain or pain interference among GMFCS levels. 5 However, the ways in which pain interfered with function differed between functional levels. Ambulation was most affected in individuals in GMFCS levels I and II; sleep was most impacted for individuals in GMFCS levels III to V. Finally, given the heterogeneity of the adult population with CP, spasticity may need to be classified along multiple dimensions that characterize both true spasticity and hypertonicity, in addition to spasm frequency. Pain is common and affects the quality of life of adults with CP. Improved characterization of spasticity and other components that may contribute to pain will be key in developing individualized treatment strategies for this patient group and effectively measuring their impact. REFERENCES 1. McKinnon CT, Meehan EM, Harvey AR, Antolovich GC, Morgan PE. Prevalence and characteristics of pain in children and young adults with cerebral palsy: a sys- tematic review. Dev Med Child Neurol 2019; 61: 305–14. 2. Peterson MD, Ryan JM, Hurvitz EA, Mahmoudi E. Chronic conditions in adults with cerebral palsy. JAMA 2015; 314: 2303–5. 3. Jarl J, Alriksson-Schmidt A, Rodby-Bousquet E. Health-related quality of life in adults with cerebral palsy living in Sweden and relation to demographic and disability-specific factors. Disabil Health J 2019; 12: 460–6. 4. Flanigan M, Gaebler-Spira D, Kocherginsky M, Garrett A, Marciniak C. Spasticity and pain in adults with cerebral palsy. Dev Med Child Neurol 2020; 62: 379–85. 5. Sienko SE. An exploratory study investigating the multi- dimensional factors impacting the health and well-being of young adults with cerebral palsy. Disabil Rehabil 2018; 40: 660–6. Commentaries 271