Somatosensory Cortical Activity is related to the Aberrant Motor Performance of Children with Cerebral Palsy.

Research Report
Population: Pediatric

Max J Kurz, PhD, Associate Professor, Physical Therapy Department

Tony Wilson, PhD, Associate Professor, Center for Magnetoencephalography, University of Nebraska Medical Center

Elizabeth Heinrichs-Graham, PhD, Assistant Professor, Center for Magnetoencephalography, University of Nebraska Medical Center

Keywords: Plasticity, Cerebral palsy, Somatosensory, Brain Imaging

PURPOSE: The current definition of cerebral palsy (CP) recognizes that the motor impairments are partially a product of aberrant sensations and an inability to interpret sensory information. This definition is supported by the numerous clinical reports of proprioception, stereognosis and tactile discrimination deficits seen in these children. Despite this definition, the connection between a child’s motor impairments and information processing in the somatosensory cortices remains almost entirely unknown. In this investigation, we explored the relationship between the magnitude of neural activity within the somatosensory cortices, and the motor performance of a group of children with CP.

SUBJECTS: Children with a diagnosis of either spastic diplegic or hemiplegia CP (N=11; Age = 14.5 +/- 0.7 yrs.) and a GMFCS level between I-III. A cohort of age-matched typically-developing (TD) children (N=11; Age = 14.1 +/- 0.7 yrs.) served as a control group.

MATERIALS/METHODS: An isokinetic dynamometer was used to measure the maximum isometric torque generated by the ankle plantar flexors. Spatiotemporal kinematics were quantified by having the children walk as fast–as-possible across a GaitRite mat. High-density magnetoencephalography (MEG) and advanced beamforming methods were used to quantify the 4-14 Hz somatosensory cortical oscillations that were evoked after a tactile stimulation was applied by a small airbladder on the bottom of the foot.

RESULTS: Neural populations within the somatosensory cortices of children with CP were desynchronized by the tactile stimulus, while those of the TD children were clearly synchronized. These brain imaging results suggest that the children with CP were unable to fully integrate the external stimulus into ongoing sensorimotor computations. Our results also revealed that the magnitude of somatosensory cortical activity for the children with CP had a strong positive relationship with the ankle strength (rho= 0.62; p=0.02), step length (rho=0.63; p=0.02) and walking speed (rho=0.68; p=0.01). These correlations suggest that stronger activity within the somatosensory cortices was related to enhanced ankle plantarflexor strength and improved mobility.

CONCLUSIONS: The somatosensory cortices of these children with CP had an abnormal response to tactile stimulation applied to the foot mechanoreceptors. The aberrant somatosensory cortical activity likely plays a significant role in the mobility and strength impairments seen in children with CP.

CLINICAL RELEVANCE: Our results imply that uncharacteristic somatosensory processing should receive greater attention when evaluating and treating the motor impairments seen in children with CP. This is especially true for children who have been previously classified as non-responders to current treatment paradigms. We suspect that these children may not demonstrate clinically relevant changes in their motor performance because the somatosensory cortices may not properly process the somato-sensations received from the foot mechanoreceptors.

Kurz, Max J, PhD; Wilson, Tony W, PhD; Heinrichs-Graham, Elizabeth , PhD. Somatosensory Cortical Activity is related to the Aberrant Motor Performance of Children with Cerebral Palsy.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online.