Effect of A Clinician-Delivered Chewing Program on Masticatory Function in Children with Cerebral Palsy

Introduction

Mastication or chewing is defined as a rhythmic oral motor activity that aids in grinding and softening solid food [1]. Chewing function has two main stages, viz. food transportation and food processing. Food transportation begins with biting the food and continues with transporting the food from the front part of the mouth to the molars by tongue. The food processing involves a series of masticatory cycles to comminute and soften the food for swallowing [2].

The development of chewing is the result of a complex interface between the developing nervous system, various physiological systems, and the environmental factors that begin in embryologic and fetal periods and continue through infancy and early childhood [3]. Chewing emerges only during the second half of the first year of life and continues to develop during childhood [4, 5]. After around 7-9 months, with the development of teeth, munching begins which involves the up and down movements of the jaw. This is followed by rotary chewing, which begins to emerge by around 12-14 months, during which the horizontal movements of the jaw appear and children learn to rotate the jaw. During this stage, children learn to handle solid foods and different textures [6].

Most children negotiate the necessary developmental sequence of chewing without significant difficulties, however, some children end up with chewing difficulties which can affect swallowing. Chewing difficulties occurring due to developmental delays are usually associated with prematurity, learning disabilities, or various neurological conditions. Cerebral palsy (CP) is one such disorder in which feeding, and specifically chewing could be impaired. Children with CP are chronically classified as malnourished due to their oral motor dysfunction, chewing deficits, and postural abnormalities [7]. Globally, the incidence of CP is estimated to be 2 per 1000 live births [8]. A study reported that in India, the incidence of CP is up to 2 to 2.5 cases per 1000 live births, making it the most common cause of disability according to the Indian Academy of Cerebral Palsy (IACP) [9].

The prevalence of chewing deficits in quadriplegic children with CP was reported to be 41% and around 26% of children with CP had deficits in chewing solid food textures [10]. A recent study found that 76% of children with spastic CP had some degree of chewing deficits [11]. In the Indian context, authors have reported that 81% of parents reported chewing difficulties in children with CP [12]. Another recent study carried out in India, reported that in 70% of the children with CP, the inability to chew food was the most persisting deficit [13]. These difficulties can affect the nutritional status, growth, general health, and quality of life of the child as well as the entire family. Therefore, it is important to treat chewing deficits in children with CP as this will have a positive impact on the physiological and emotional well-being of the child.

A few strategies have been used in the past to treat chewing deficits in children with CP, which have revealed positive outcomes such as behavioral training and oral sensorimotor training [14, 15, 16, 17, 18, 19]. However, these approaches primarily focus on the underlying impairment and do not include training the chewing function. They focus on individual oromotor skills such as tongue lateralization, lip control, and jaw strengthening, which are only prerequisites for chewing.

A relatively recent program called functional chewing training (FCT) was proposed by Arslan and colleagues for children with CP [20]. They believed in a functional approach to improve chewing, which involves training the oromotor structures for the targeted function and generalizing those functions to everyday activities. The protocol includes two domains viz., impairment-based (positioning for feeding and food placement, orosensory stimulation, and chewing exercises) and adaptive components (adjustments made to the food textures). This protocol was carried out as a home training program by them and the parents were trained about the procedure and standardized brochures related to the same were provided. The authors reported that the proposed chewing training was found to be effective in comparison to traditional oral-motor exercises.

In sum, though various strategies have been used to improve chewing, the most recent among them is FCT, which not only lays emphasis on the underlying impairment, but also focuses on generalization of the chewing behavior using food of different consistencies, thus incorporating both impairment-based and adaptive-based components. Though Arslan and colleagues have assessed the efficacy of the FCT through a randomized controlled trial, they have done it as a home program by training the parents of children with CP. During a home-based program, there could be various uncontrolled variables, like not adhering to the protocol for the recommended days or duration, lack of cooperation from the child, and other environmental and personal factors, leading to a dilution of the program at the execution level.

Hence, there is a need to assess its efficacy through a clinician-delivered program. Further, the existing studies have not studied the maintenance effect of FCT, after it is withdrawn. Studies in the field of pediatric feeding therapy and chewing therapy in particular are also essential in the Indian context as the feeding practices and foods consumed vary in comparison to the other countries. Therefore, the present study was planned to assess the effects of a clinician- delivered FCT on children with CP.

Methods

A time series design was employed to study the treatment effects within the group.

Results

Friedman’s Test was used to compare MOE parameters such as jaw, lip, tongue, and overall mastication scores across pre-, post-treatment and follow-up conditions. The median values clearly indicated that there was an improvement in all the parameters across timelines. Pairwise comparisons using Wilcoxon Signed Rank test with adjusted alpha revealed that there was a significant difference in the jaw, lip, and tongue scores in the pre- versus post-therapy and pre- versus follow- up conditions. However, in the overall mastication scores there was a significant difference between all three timelines at 0.05 level of significance. The results have been depicted in Table 1 below.

Note: I – Pre-treatment; II – Post-treatment; III – Follow-up after 1 month. *Significant at 0.05 level of significance with adjusted alpha (p<0.017). Table 1: Median, Inter Quartile Range (IQR), Friedman Test Statistic And |Z| Value Across Treatment Timelines for Mastication Observation Evaluation.

The non-parametric Friedman’s Test was also used to compare sEMG parameters such as amplitude, chew duration, and inter-chew duration across pre-, post- treatment and follow-up conditions. It can be noted from the median values that there was an increase in amplitude across sessions, whereas both the duration parameters decreased across sessions. The findings thus indicate that there was an improvement in all the three sEMG parameters. Further, pairwise comparisons using Wilcoxon Signed Rank test revealed that there was a significant difference in all the 3 sEMG parameters in both the left and right masseter muscles in the pre- versus post-therapy and pre- versus follow-up conditions at 0.05 level of significance. The results have been depicted in Table 2 below.

Note: I – Pre-treatment; II – Post-treatment; III – Follow-up after 1 month. Rt – Right masseter; Lt – Left masseter. *Significant at 0.05 level of significance with adjusted alpha (p<0.017). Table 2: Median, Inter Quartile Range (IQR), Friedman Test Statistic and |Z| Value Across Treatment Timelines for Semg Parameters.

Discussion

The findings of the study highlight the improvement in masticatory dynamics as evinced by the scores of both the subjective and objective assessment tools. There was a significant change in the different masticatory outcome measures after the intensive FCT program. This is in agreement with the findings of recent studies which have reported that FCT is effective in improving the chewing abilities in addition to reducing tongue thrust and drooling in children with CP [7, 20]. However, these studies employed a parent-delivered program and also compared the overall chewing performance and feeding behaviors by using only subjective tools.

The MOE is a reliable and valid tool that assesses the isolated oromotor movements involved in chewing. The results indicated enhanced functioning of the oral structures in chewing. There was an improvement in jaw, lip, tongue and overall masticatory coordination contributing to better masticatory performance. FCT facilitated better lip seal, jaw stability and tongue lateralization in the post-therapy and follow-up conditions, aiding in effective chewing and swallowing. As a result, all the participants were able to successfully transition from pureed or mashed consistencies to safely ingest easy-to-chew solid food.

The present study is one of the first to use an objective tool such as sEMG to assess masticatory efficiency across a chewing training program. Studies have shown that the weakness in the masticatory muscles in children with CP leads to increased muscle contraction duration and reduced amplitude [21, 22, 23, 24]. The sEMG results indicated an increase in jaw strength and masticatory control, exemplified by the changes both in terms of amplitude and duration measures of the right and left masseter muscles. The significant difference observed in the pre- versus post-therapy and follow-up conditions indicates an optimistic outcome with respect to the duration of therapy and the components involved in the intervention. The fact that 20 sessions of training could notably improve muscle strength and functioning is encouraging for SLPs, since a concise therapy plan for feeding is the need of the hour as there is a shortage of pediatric feeding therapists, whereas the demand for dysphagia therapy is huge.

It is interesting to note that both in MOE and sEMG, there was an improvement in pre- versus post-therapy and pre- versus follow-up conditions. This could indicate that the functional changes in oral structures occur in close association with neuromuscular changes across the 20 sessions of chewing training. The continued improvement after therapy shows that though the chewing exercises are not being performed overtly, better management and progression of food textures leads to inclusion of variety in the diet, which reflects improved muscle strength and masticatory performance and no detraining effect. The significant difference in the pre-post condition for both objective and subjective measures could indicate that the duration of the training program is sufficient to stabilize muscle strength and functioning.

No significant difference in all the MOE and sEMG parameters, except overall MOE scores between the post- therapy versus follow-up conditions, indicate that the improvements though present were small, suggesting a lack of detraining effect. However, these minor improvements cannot be considered insignificant as they signify the neurodevelopmental and oromotor changes which are occurring as a result of inclusion of various textures in the diet of the participants. As indicated previously, the cessation of chewing exercises and orosensory stimulation could have led to a deceleration in the oromotor movements associated with mastication. Interestingly, a significant change was seen across all the three timelines in the overall mastication scores on MOE, which is encouraging. The individual jaw, lip and tongue scores when added up showed a significant change, which could indicate the interactive relationship between parameters. Therefore, conducting the study on a larger population might provide more conclusive evidence regarding treatment effects and this will help in generalizing the results better.

Conclusions

The present study is a preliminary attempt in the Indian context and adds to the small body of research on mastication in pediatric feeding disorders, particularly those with cerebral palsy. The findings provide noteworthy evidence to elucidate the efficacy of the FCT program by illustrating the changes in jaw, lip, tongue abilities during chewing and in amplitude and durational parameters contributing to better masticatory performance. The present study is one of the first to use objective assessments such as sEMG to assess masticatory efficiency across a chewing training program. The limitation of the study is the small sample size.

Future studies need to include multiple functional outcome measures to document the impact of chewing training on the quality of life using a larger sample.

Acknowledgements: We would like to thank the University of Mysore for the support rendered. We also wish to thank the Director, AIISH, Mysuru for providing the infrastructure for the study. Lastly, we express our gratitude to all the participants and the parents. Contributors: KV and SN – conceived and designed the study; KV: collected the data; KV: analysis and interpretation of data; KV and SN: drafting the manuscript; Both the authors approved the final manuscript. Funding Agency: None. Conflicts of Interest: There are no conflicts of interest.