Despite the importance of somatosensation during motor development, a comprehensive characterization of the typical development of somatosensory function in children does not exist. This is largely due to a lack of objective measures with appropriate resolution. Mapping trajectories of typical development of proprioceptive and haptic function is necessary in order to identify sensory deficits in pediatric patient populations with known or suspected proprioceptive and/or haptic deficits. One such population is children treated with chemotherapy for pediatric cancers. Chemotherapeutic agents used to treat cancer generate unwanted side effects including peripheral nerve damage called chemotherapy-induced peripheral neuropathy (CIPN). To date, the magnitude and timeline of somatosensory impairments due to CIPN are not well understood. We have updated a methodology of measuring proprioceptive acuity and developed a novel measure of haptic acuity and sensitivity that are appropriate for use in both adult and pediatric populations. The aims of this study were to apply these two assessment tools to characterize 1) proprioceptive and 2) haptic function during typical development, 3) measure somatosensory-related impairment in individuals treated with chemotherapy for pediatric cancer, and 4) identify relationships between chemotherapy-related somatosensory impairment and therapeutic markers such as cumulative dosage of chemotherapeutic agents. Methods: To map the development of proprioceptive acuity, 308 typically developing (TD) children (ages 5-17 years) and 26 adults (ages 18-25 years) performed a forearm position matching task with a bimanual manipulandum. Haptic acuity (discrimination) or sensitivity (detection) was measured using curvature perception assessments in 59 and 56 children respectively (ages 9-12 years). Healthy adults completed both haptic assessments (n = 27, ages 19-25 years). These proprioceptive and haptic assessments were utilized to characterize somatosensory impairment in 15 individuals treated with chemotherapy for pediatric cancers (ages 6-25 years). Results: First, proprioceptive development is characterized by a reduction in random limb position matching error, not a change in systematic limb position error. Second, haptic acuity and sensitivity does not change significantly after the age of 9 years. Third, these somatosensory assessments were able to characterize proprioceptive and haptic impairment in individuals treated with chemotherapy for pediatric cancer. 7 of 15 cancer survivors exhibited proprioceptive precision measures above the 75th percentile and 11 of 15 exhibited at least one haptic function measure above the 75th percentile of their age-matched cohort. Fourth, a multiple linear regression model of cumulative dosage of chemotherapeutic agent types predicted 80% of the variability in the haptic discrimination thresholds (adjusted R2 = 0.80). Conclusion: This work generated a complete characterization of the development of proprioceptive acuity in TD children and established haptic function is adult-like by the age of 9 years. This study also demonstrated proof-of-concept for identifying somatosensory deficits in individuals treated with chemotherapy for pediatric cancers. These objective, clinically appropriate, somatosensory assessments and the necessary normative development data established here can identify or monitor somatosensory deficits in pediatric populations with known or suspected deficits.
University of Minnesota Ph.D. dissertation. August 2018. Major: Kinesiology. Advisor: Juergen Konczak. 1 computer file (PDF); x, 57 pages.
Characterizing proprioceptive and haptic function in typically developing children and individuals with chemotherapy-related somatosensory impairment.
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