Reduced wrist flexor H-reflex excitability is linked with increased wrist proprioceptive error in adults with cerebral palsy

Abstract

Although most neurophysiological studies of persons with cerebral palsy (CP) have been focused on supraspinal networks, recent evidence points toward the spinal cord as a central contributor to their motor impairments. However, it is unclear if alterations in the spinal pathways are also linked to deficits in the sensory processing observed clinically. This investigation aimed to begin to address this knowledge gap by evaluating the flexor carpi radialis (FCR) H-reflex in adults with CP and neurotypical (NT) controls while at rest and during an isometric wrist flexion task. The maximal H-wave (Hmax) and M-wave (Mmax) at rest were calculated and utilized to compute Hmax/Mmax ratios (H:M ratios). Secondarily, the facilitation of the H-wave was measured while producing an isometric, voluntary wrist flexion contraction (i.e., active condition). Finally, a wrist position sense test was used to quantify the level of joint position sense. These results revealed that the adults with CP had a lower H:M ratio compared with the NT controls while at rest. The adults with CP were also unable to facilitate their H-reflexes with voluntary contraction and had greater position sense errors compared with the controls. Further, these results showed that the adults with CP that had greater wrist position sense errors tended to have a lower H:M ratio at rest. Overall, these findings highlight that aberration in the spinal cord pathways of adults with CP might play a role in the sensory processing deficiencies observed in adults with CP.

Proprioception, Emotion and Social Responsiveness in Children with Developmental Disorders: An Exploratory Study in Autism Spectrum Disorder, Cerebral Palsy and Different Neurodevelopmental Situations

“…These clinical findings have been corroborated by studies showing alterations in neural networks processing proprioception, such as the inferior parietal lobe, in children with ASD [69]. The present findings confirmed poorer proprioception acuity and proprioceptive reactive behaviors in children with CP, which can be explained by the influence of spasticity on muscle lengthening (which are characteristic of the CP condition), as well as the abnormalities in neural tracts and afferent cortical perception [35,64]. Surprisingly, our results do not show abnormal proprioception in children with ASD, when compared to TDPs.…”

“…Extensive research has reported proprioceptive impairments in children with CP [ 21 , 22 , 23 , 64 , 65 ], impacting activity, participation and functional performance [ 22 , 23 ]. Proprioceptive deficits in children with CP have been associated with motor function impairment and spasticity [ 25 , 64 , 66 ] and have been attributed to abnormalities of spino- and thalamo-cortical neural tracts, abnormal cortical activity and lower muscle H-reflex excitability [ 35 , 66 , 67 ]. On the other hand, previous research in children with ASD has reported diminished proprioceptive performance, in the form of poor perception of joint position and altered speed-based proprioception [ 19 , 63 , 68 ].…”

“…The sum of the errors in each of the four wrist positions was regarded as the joint position error, with higher values indicating worse proprioception. This method for assessing proprioception has previously been used in individuals with cerebral palsy [ 35 ].…”

Adults with cerebral palsy exhibit uncharacteristic cortical oscillations during an adaptive sensorimotor control task

“…Altogether, these combined results suggest that the altered PMBR seen for the persons with CP might indicate greater uncertainty about the sensory feedback after the completion of the motor task 23 , 24 . We speculate that this uncertainty is likely related to the altered sensory processing noted across the behavioral 1 , 69 – 72 and neurophysiology literature for persons with CP 13 , 62 , 73 – 78 . As such, the altered sensory processing at both the cortical and spinal cord level likely has cascading effects on the sensorimotor system and affects the fidelity assessment of adjusted motor outcomes.…”

“…Lastly, the participants completed the wrist position test, which quantifies the ability of the participant to correctly identify the joint’s position following a movement performed by the examiner 61 , 62 . The test consists of 20 predetermined wrist flexion and extension angles, where the examiner passively moved the wrist to the endpoint angular position as the participant’s vision of the wrist position was occluded.…”