Somatosensory and visual evoked potentials in children with cerebral palsy: Correlations and discrepancies with MRI findings and clinical picture

Youth with Cerebral Palsy Display Abnormal Somatosensory Cortical Activity During a Haptic Exploration Task

There are numerous clinical reports that youth with cerebral palsy (CP) have proprioceptive, stereognosis and tactile discrimination deficits. The growing consensus is that the altered perceptions in this population are attributable to aberrant somatosensory cortical activity seen during stimulus processing. It has been inferred from these results that youth with CP likely do not adequately process ongoing sensory feedback during motor performance. However, this conjecture has not been tested. Herein, we address this knowledge gap using magnetoencephalographic (MEG) brain imaging by applying electrical stimulation to the median nerve of youth with CP (N = 15, Age = 15.8 ± 0.83 yrs, Males = 12, MACS levels I-III) and neurotypical (NT) controls (N = 18, Age = 14.1 ± 2.4 yrs, Males = 9) while at rest (i.e., passive) and during a haptic exploration task. The results illustrated that the somatosensory cortical activity was reduced in the group with CP compared to controls during the passive and haptic conditions. Furthermore, the strength of the somatosensory cortical responses during the passive condition were positively associated with the strength of somatosensory cortical responses during the haptic condition (r = 0.75, P = 0.004). This indicates that the aberrant somatosensory cortical responses seen in youth with CP during rest are a good predictor of the extent of somatosensory cortical dysfunction during the performance of motor actions. These data provide novel evidence that aberrations in somatosensory cortical function in youth with CP likely contribute to the difficulties in sensorimotor integration and the ability to effectively plan and execute motor actions.

Aberrant movement-related somatosensory cortical activity mediates the extent of the mobility impairments in persons with cerebral palsy

KEY POINTS

Persons with cerebral palsy (CP) have reduced somatosensory cortical responses at rest and during movement. The somatosensory cortical responses during movement mediate the relationship between the somatosensory cortical responses at rest and mobility. Persons with CP may have altered sensorimotor feedback that ultimately contributes to impaired mobility.

ABSTRACT

There are numerous clinical reports that persons with cerebral palsy (CP) have proprioceptive, stereognosis and tactile discrimination deficits. The current consensus is that these altered perceptions are attributable to aberrant somatosensory cortical activity. It has been inferred from these data that persons with CP do not adequately process ongoing sensory feedback during motor actions, which accentuates the extent of their mobility impairments. However, this hypothesis has yet to be directly tested. We used magnetoencephalographic (MEG) brain imaging to address this knowledge gap by quantifying the somatosensory dynamics evoked by applying electrical stimulation to the tibial nerve in 22 persons with CP and 25 neurotypical (NT) controls while at rest and during an ankle plantarflexion isometric force motor task. We also quantified the spatiotemporal gait biomechanics of participants outside the scanner. Consistent with the literature, our results confirmed that the strength of somatosensory cortical activity was weaker in the persons with CP compared to the NT controls. Our results also showed that the strength of the somatosensory cortical responses were significantly weaker during the isometric ankle force task than at rest. Most importantly, our results showed that the strength of somatosensory cortical activity during the ankle plantarflexion force production task mediated the relationship between somatosensory cortical activity at rest and both walking velocity and step length. These results suggest that youth with CP have aberrant somatosensory cortical activity during isometric force generation, which ultimately contributes to the extent of mobility impairments seen in this patient population. Abstract figure legend Magnetoencephalographic brain imaging was used to determine the effect of sensory feedback during movement on mobility in persons with cerebral palsy. Persons with cerebral palsy had reduced somatosensory cortical activity at rest and during movement compared with their neurotypical peers. Further, the somatosensory cortical activity during movement mediated the relationship between somatosensory cortical activity at rest and mobility. These results indicate that difficulties in sensorimotor integration may contribute to the mobility impairments seen in this patient population. This article is protected by copyright. All rights reserved.

Somatosensory deficits and neural correlates in cerebral palsy: a scoping review

AIM

To synthetize studies assessing somatosensory deficits and alterations in cerebral responses evoked by somatosensory stimulation in individuals with cerebral palsy (CP) compared to typically developing individuals.

METHOD

A scoping review of the literature was performed in the MEDLINE, Embase, PsycInfo, CINAHL, Evidence-Based Medicine Reviews, and Web of Science databases (last search carried out on 6th and 7th August 2020) with a combination of keywords related to CP and somatosensory functions. Somatosensory deficits were measured with clinical tests and alterations in cerebral responses were measured with functional magnetic resonance imaging, electroencephalography, and magnetoencephalography.

RESULTS

Forty-eight articles were included. Overall, 1463 participants with CP (mean [SD] age 13y 1mo [4y 11mo], range 1-55y; 416 males, 319 females, sex not identified for the remaining participants) and 1478 controls (mean [SD] age 13y 1mo [5y 8mo], range 1-42y; 362 males, 334 females, sex not identified for the remaining participants) were included in the scoping review. For tactile function, most studies reported registration (8 out of 13) or perception (21 out of 21) deficits in participants with CP. For proprioception, most studies also reported registration (6 out of 8) or perception (10 out of 15) deficits. Pain function has not been studied as much, but most studies reported registration (2 out of 3) or perception (3 out of 3) alterations. Neuroimaging findings (18 studies) showed alterations in the somatotopy, morphology, latency, or amplitude of cortical responses evoked by somatosensory stimuli.

INTERPRETATION

Despite the heterogeneity in the methods employed, most studies reported somatosensory deficits. The focus has been mainly on tactile and proprioceptive function, whereas pain has received little attention. Future research should rigorously define the methods employed and include a sample that is more representative of the population with CP. What this paper adds Most of the papers reviewed found tactile registration and perception deficits in the upper limbs. Proprioceptive deficits were generally observed in cerebral palsy but results were heterogeneous. Pain has received little attention compared to tactile and proprioceptive functions. Neuroimaging studies supported behavioral observations. Alterations were observed for both the most and least affected limb.

Pattern-Reversal Visual Evoked Potential in Children With Congenital Zika Syndrome

PURPOSE

To objectively evaluate the visual function in children with congenital Zika syndrome using pattern-reversal visual evoked potential (PR-VEP).

METHODS

This was a cross-sectional study composed of two patient groups: children aged between 18 and 24 months who were positive for the Zika virus (congenital Zika syndrome group) and age-matched healthy children (control group). All patients underwent a comprehensive ophthalmologic examination and PR-VEP was performed binocularly in a room with constant dim illumination. The P100 peak time in the 60' arc stimuli was used, and the results were correlated with visual acuity, cephalic perimeter at birth, and funduscopic findings.

RESULTS

Thirty-seven children were included in the congenital Zika syndrome group and 15 in the control group. The mean age was 18.5 ± 0.9 months (range: 17 to 20 months) in the congenital Zika syndrome group and 24.3 ± 1.6 months (range: 21 to 28 months) in the control group. The P100 response was normal in 7 patients (18.9%) with congenital Zika syndrome, borderline in 2 (5.4%), abnormal with prolonged latency in 18 (48.6%), and abnormal with no response in 10 (27.0%). A significant correlation between the visual acuity and P100 peak time was observed (P < .001). The P100 values were not correlated significantly with the cephalic perimeter at birth (P = .412) or the funduscopic findings (P = .510). PR-VEP in children with congenital Zika syndrome and no funduscopic findings was significantly worse than in the control group (P = .001).

CONCLUSIONS

Children with congenital Zika syndrome have characteristically abnormal PR-VEPs regardless of the funduscopic findings and severe microcephaly. The PR-VEP findings supported the diagnosis of cortical visual impairment in these children. [J Pediatr Ophthalmol Strabismus. 2021;58(2):78-83.].

Children with Cerebral Palsy Hyper-Gate Somatosensory Stimulations of the Foot

We currently have a substantial knowledge gap in our understanding of the neurophysiological underpinnings of the sensory perception deficits often reported in the clinic for children with cerebral palsy (CP). In this investigation, we have begun to address this knowledge gap by using magnetoencephalography (MEG) brain imaging to evaluate the sensory gating of neural oscillations in the somatosensory cortices. A cohort of children with CP (Gross Motor Function Classification System II-III) and typically developing children underwent paired-pulse electrical stimulation of the tibial nerve during MEG. Advanced beamforming methods were used to image significant oscillatory responses, and subsequently the time series of neural activity was extracted from peak voxels. Our experimental results showed that somatosensory cortical oscillations (10-75 Hz) were weaker in the children with CP for both stimulations. Despite this reduction, the children with CP actually exhibited a hyper-gating response to the second, redundant peripheral stimulation applied to the foot. These results have further established the nexus of the cortical somatosensory processing deficits that are likely responsible for the degraded sensory perceptions reported in the clinic for children with CP.

Children with cerebral palsy have uncharacteristic somatosensory cortical oscillations after stimulation of the hand mechanoreceptors

Numerous clinical investigations have reported that children with cerebral palsy (CP) have tactile discrimination deficits that likely limit their ability to plan and manipulate objects. Despite this clinical awareness, we still have a substantial knowledge gap in our understanding of the neurological basis for these tactile discrimination deficits. Previously, we have shown that children with CP have aberrant theta-alpha (4-14 Hz) oscillations in the somatosensory cortices following tactile stimulation of the foot. In this investigation, we evaluated if these aberrant theta-alpha oscillations also extend to the hand. Magnetoencephalography was used to evaluate event-related changes in the theta-alpha and beta (18-34 Hz) somatosensory cortical oscillations in groups of children with CP and typically developing (TD) children following tactile stimulation of their hands. Our results showed that the somatosensory theta-alpha oscillations were relatively intact in children with CP, which is in contrast to our previous results for foot tactile stimulations. We suspect that these inter-study differences may be related to the higher probability that the neural tracts serving the lower extremities are damaged in children with CP, compared to those serving the upper extremities. This inference is plausible since the participating children with CP had Manual Ability Classification System (MACS) levels between I and II. In contrast to the theta-alpha results, children with CP did exhibit a sharp increase in beta activity during the same time period, which was not observed in TD children. This suggests that children with CP still have deficits in the computational aspect of somatosensory processing.

The magnitude of the somatosensory cortical activity is related to the mobility and strength impairments seen in children with cerebral palsy

The noted disruption of thalamocortical connections and abnormalities in tactile sensory function has resulted in a new definition of cerebral palsy (CP) that recognizes the sensorimotor integration process as central to the motor impairments seen in these children. Despite this updated definition, the connection between a child's motor impairments and somatosensory processing remains almost entirely unknown. In this investigation, we explored the relationship between the magnitude of neural activity within the somatosensory cortices, the strength of the ankle plantarflexors, and the gait spatiotemporal kinematics of a group of children with CP and a typically developing matched cohort. Our results revealed that the magnitude of somatosensory cortical activity in children with CP had a strong positive relationship with the ankle strength, step length, and walking speed. These results suggest that stronger activity within the somatosensory cortices in response to foot somatosensations was related to enhanced ankle plantarflexor strength and improved mobility in the children with CP. These results provide further support for the notion that children with CP exhibit, not only musculoskeletal deficits, but also somatosensory deficits that potentially contribute to their overall functional mobility and strength limitations.

Aberrant synchrony in the somatosensory cortices predicts motor performance errors in children with cerebral palsy

Cerebral palsy (CP) results from a perinatal brain injury that often results in sensory impairments and greater errors in motor performance. Although these impairments have been well catalogued, the relationship between sensory processing networks and errors in motor performance has not been well explored. Children with CP and typically developing age-matched controls participated in this investigation. We used high-density magnetoencephalography to measure event-related oscillatory changes in the somatosensory cortices following tactile stimulation to the bottom of the foot. In addition, we quantified the amount of variability or errors in the isometric ankle joint torques as these children attempted to match a target. Our results showed that neural populations in the somatosensory cortices of children with CP were desynchronized by the tactile stimulus, whereas those of typically developing children were clearly synchronized. Such desynchronization suggests that children with CP were unable to fully integrate the external stimulus into ongoing sensorimotor computations. Our results also indicated that children with CP had a greater amount of errors in their motor output when they attempted to match the target force, and this amount of error was negatively correlated with the degree of synchronization present in the somatosensory cortices. These results are the first to show that the motor performance errors of children with CP are linked with neural synchronization within the somatosensory cortices.

Somatosensory evoked potentials in children with bilateral spastic cerebral palsy

Alterations were monitored of somatosensory evoked potentials in children with bilateral spastic cerebral palsy and these findings correlated with relevant clinical and laboratory parameters. Fifty-one children with bilateral spastic cerebral palsy (31 boys, 20 girls; age range 24-168 months) participated in the study. Abnormal somatosensory evoked potentials latencies were recorded in 23 of 34 (67.6%) cortical recordings of the median nerve and in 38 of 51 (74.5%) cortical recordings of the tibial nerve. Abnormal tibial nerve somatosensory evoked potentials were strongly correlated with abnormal electroencephalogram (P=0.014), while impaired median nerve recordings were correlated with abnormal visual evoked potentials (P = 0.02) and a history of perinatal or neonatal infection (P=0.016). Furthermore, perinatal/neonatal infection adversely effected the recordings in both tibial and medial nerves in quadriplegic patients (P=0.023). Sensory impairment is strongly related with abnormal visual evoked potentials, abnormal electroencephalogram, and a history of perinatal or neonatal infection.