Children with unilateral spastic cerebral palsy (USCP) have impairments affecting upper limb function, particularly in grasping abilities. Specifically, children with USCP may display precision grip impairments, which can lead to activity limitations. The interplay between feedforward and feedback control is essential for successful grasping, requiring somatosensory information to be integrated with the motor output. This integration occurs through the transmission of somatosensory information through the dorsal column medial lemniscus (DCML) pathway, while independent finger movement to grasp an object is controlled by the motor cortex via the corticospinal tract (CST).
While previous studies demonstrated the CST relates to anticipatory control of grasping, this may not explain all the variance of grasp impairments in children with USCP. Although studies have highlighted the importance of sensory information in grasping in typically developing (TD) adults, there are no studies examining the relationship between brain structure and function in terms of precision grip impairments in children with USCP. Additionally, sensorimotor integration plays an important role in precision grip. In some children with USCP, the lesion that occurs in the brain can cause the CST to reorganize to the contralesional hemisphere. This results in the sensory and motor tracts in different hemispheres, impacting motor impairments. When this sensory-motor dissociation occurs or when there are successive lifts of an object with each hand, it is thought that the information is transferred through the corpus callosum (CC). However, damage to the CC can restrict somatosensory processing, which can further impair grasping abilities. Previous studies have only looked at precision grip impairments in relation to the CST. Therefore, an integrative approach is necessary to fully understand the mechanisms of precision grip impairments in children with USCP. In this study our aim was to examine the neural basis of precision grip in children with USCP.
Twenty-seven children participated in an MRI assessment. This included the acquisition of structural and diffusion-weighted images (DWI) to extract diffusion metrics of the CST, DCML pathway, and CC. Children also participated in clinical sensory measures, including the stereognosis test, grating orientation task, and the two-point discrimination task. Additionally, children performed precision grip lifts using a custom-made object. All children were asked to grasp an object with interchangeable surfaces (i.e., sandpaper and rayon) to measure adaptation of grip force (GF) to object texture. They were also asked to grasp the same object, hold it in the air and slowly release their grip so that the object gradually slips from their fingertips. Twenty-seven children performed these tasks with their less affected hand, and 16 with their more affected hand. Additionally, 17 participants grasped an object with various weights with each lifting sequence consisting of lifting an object in succession with the same hand and then one lift with the contralateral hand.
The results demonstrate the greater reduction of integrity (more damage) of the DCML pathway, the poorer the grasp task performance, as indicated through the safety margin (the difference between the minimum amount of force needed to prevent slipping and the applied grip force). Regression analyses and cluster analyses display that CST integrity and organization may also contribute to safety margin. This suggests that diffusion metrics of multiple pathways and CST organization when considered together contribute to grasping impairments in children with USCP. To assess this further, we examined the relative difference in the peak rate of force between objects with various weights during successive lifts with each hand. Children with USCP did demonstrate anticipatory control within hands and a generalization of anticipatory control between hands. However, a loss of the transfer information was shown when first grasping the object with their less affected hand and then their more affected hand, in children with an absent contralateral CST. Therefore, the results suggest precision grip impairments may not exclusively be due to sensory impairments, but instead how the sensory information is integrated with the motor output of the same hand.
| Identifer | oai:union.ndltd.org:columbia.edu/oai:academiccommons.columbia.edu:10.7916/gwcy-ek91 |
| Date | January 2024 |
| Creators | Gutterman, Jennifer |
| Source Sets | Columbia University |
| Language | English |
| Detected Language | English |
| Type | Theses |
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