Introduction

Manual therapy, an umbrella term used to describe a variety of force applications ranging from light touch to manipulation, has been described within literature for the treatment of multiple paediatric conditions, ranging from infant colic to headaches to enuresis, with varied outcomes.1 One differentiating feature apparent between the sources of these data appears to be the method of manual therapy used, which in turn may be responsible for the variations in outcome observed.

Parents often seek input and management from healthcare professionals for infants with developmental delay, with manual therapy often utilised as a modality aimed to improve neurological function.2,3 There are, however, limitations to this approach based on the neurophysiological responses of neurons to afferentive input. Two major pathways involved in cortical afferentation are nociception and proprioception. In terms of outcome, in pain-based conditions, a reduction of nociception will result in decreased cortical pain response, but in conditions requiring greater cortical stimulation proprioceptive input, specifically from the upper cervical spine, provides significant amounts of cortical afferentation.4 The source for this afferentation is derived from muscle spindle evoked responses; stretching of tissue triggering activation of these specialised cells. Duration of input and rate of force production are 2 key variables involved in eliciting a neurophysiological response in adults and animals.5,6 Although these data derive from adult and animal studies, similarities exist regarding neurophysiological activation,7,8; however, the limited amount of data specifically for infants limits our capacity to make statements with certainty. Beyond neurophysiology, musculoskeletal or articular restrictions may not only alter the afferentation received, but also produce nociceptive input that may promote aversion to a particular task, creating an unexpected aetiology behind neurodevelopmental delay.9

This case discusses the case of an infant exhibiting gross motor developmental delay who experienced minimal improvement from 1 practitioner and who them demonstrated improvement in gross motor development after receiving manual therapy from a second practitioner. There are likely many factors involved in the changes observed with this particular case: natural history, time, parental interaction or other unknown factors. However, the rate of change after the change of practitioner suggests these factors to be less likely to be responsible for development improvement. We hypothesize the reason for this is 1 of 2 possibilities; first, an increased neurophysiological response the result of different manual therapy technique, and second, appropriate assessment and management of all musculoskeletal regions involved in this infant. This case was prepared following CARE guidelines.10

CASE REPORT

This case discusses a male infant born at 37 + 4 weeks gestation to a first-time (P1G1) mother. The mother encountered moderate stress during pregnancy; testing positive for COVID-19 at 33 weeks gestation as well as requiring antibiotics for suspected pneumonia with associated rib fracture. Labor was spontaneous; however, she required oxytocin for progression. Ventouse/vacuum extraction was required. The infant was fully breastfed; however, the mother experienced some difficulty with this process, including poor attachment, poor suck strength, and prolonged feed durations.

Timeline

This baby was seen by Practitioner 1 at 7 days of age for assessment and management of “reflux” and positional preference. The “reflux” was described to be occurring within 20 minutes of feeding and involved regurgitation or vomiting of a milky or yellow-tinged fluid. While normative cervical spine passive range of motion has been previously described, using goniometry as a part of routine assessment is impractical, leading to the use of measure points as listed by Van Vlimmeren. Full rotation is considered reached if the chin rotates to above the acromion (rotation), and the ear can reach the shoulder (lateral flexion).11 Using these determinations of normative movement, we found restriction in left cervical spine rotation and right lateral flexion, with the majority of this limitation being noticed in the left upper cervical region (C0/1). Extremity assessment revealed restrictions of passive joint play in both left and right glenohumeral joints in anterior-posterior (A-P) joint play. A truncated hip assessment for age was normal bilaterally. Cranial assessment showed an open anterior fontanelle of 2.5cm in diameter, a closed posterior fontanelle and a head circumference of 31cm. A slight right occipital deformational plagiocephaly was observed, classified as Grade 1 on the Argenta classification of plagiocephaly. Pull-to-sit test showed full lag with a left tilt and alternating rotation. Primitive reflex test for Galants, Perez, Moro, Placing and Walking were all normal.

Treatment consisted of manual therapy to the glenohumeral joint and C0/1 articulation using a Thuli-branded portable drop piece (Thuli Extremity Drop Piece (EDP), Thuli Tables, Inc., Dodgeville, WI, USA).

Three treatments were performed over a 3-week period (once per week), with improvements in both cervical range of motion and vomiting frequency. At this point the trial of treatment ceased prematurely due to family personal circumstance.

At 2 months of age, the baby was seen by Practitioner 2. There were continued concerns over neck range of motion, reflux, and colicky behaviour. Examination revealed “reduced right arm and leg body movements, +2 bilateral muscle stretch reflexes, Moro +3, Fear Paralysis reflex at cervical and occipital levels, right extensor plantar response (Babinski), asymmetric tonic neck reflex (ATNR) +2 to the left with the right unable to test due to restriction. He was flushed with body torque to the left and a left low ear. A left sided palate strain was observed, with a flattening of the left occiput and bulging of the right frontal bone. Ortolani/Barlow testing was performed with no indication of hip dysplasia. Restrictions of motion were felt at S4, S2, T12/L1, left T5, left occiput and C1”. 13 treatments were administered over a duration of 25 weeks using Sacro Occipital Technique (SOT) consisting of light pressure hold, cranial adjustments and oral fascial release. Cervical range of motion and right upper limb movement were described as being improved based on pre-appointment subjective commentary; however, no post-treatment results were recorded.

At 8 months of age (7M28D), he resumed management with Practitioner 1. The parents expressing ongoing concerns of limited cervical range of motion, developmental delay, and decreased right arm and leg activity. There was a delay and asymmetry in rolling front to back at 6 months of age, and back to front at 7 months of age both only over the left, and an inability to sit unsupported. Crawling had not commenced. We found reduced bilateral upper cervical passive range of motion, as well as bilateral glenohumeral joint anteroposterior joint play. Pull-to-sit testing demonstrated moderate head lag without any tilting or rotation present. Normal muscle stretch reflexes for an infant were diminished at L4 nerve root on the left (+2, +3 on right) and absent at S1 nerve root (0 bilaterally). Treatment was administered to the C0/1 articulation using a Thuli EDP drop piece. Therapy was also directed to both glenohumeral joints and coccyx. At his review appointment 1 week later at 8M2D, his mother reported he was rolling in both directions without restriction the day after treatment. At 8M9D after a repeated treatment to the cervical spine and shoulders, there was continued rolling activity in both directions, independent sitting, symmetrical and full arm and leg use, improved propping, and development of babbling. After a 10-week period of treatment, the child had caught up on developmental milestones, including cross crawling, pulling to stand, and cruising along furniture. No adverse events were reported during the manual therapy.

Discussion

The baby showed improvements in gross motor development after initiating a trial of manual therapy involving greater force than light touch. At 8 months of age (MOA), the baby demonstrated gross motor developmental delay with head lag being present on pull to sit (normally achieved by 4MOA), being unable to roll from front to back or vice versa (normally achieved by 4-5MOA), and not being able to sit without support (normally achieved by 7MOA).12 By 10MOA, he was demonstrating flexion on the pull to sit test (4MOA), pulling to stand (9MOA), and cruising along furniture (normally achieved by 11MOA).12 While natural history may play a key component to the rapid progression observed between 8 and 10MOA, there must be consideration of the impact of cortical afferentation from spinal manual therapy.2,3

Previous literature found light touch to be in the range of 2-4N, with a proposed model of force thresholds to be around 20N.13,14 In comparison, Triano and Koch both demonstrate forces greater than 20N when used for the cervical spine.15,16 Of note, the force data included by Marchand13 from Koch16 has been incorrectly interpreted, with thrust force (measured as a change in force from pretension to peak force; 50N) being misinterpreted as peak force (measured as range of force from application to peak force; 83-135N) without taking into consideration pretension force.16 This deficit of 33-85N is clinically significant within the context of this case; below 20N the application of force may not have been adequate to generate neurophysiological activation.

Light-touch manual therapy has evidence of benefit for some paediatric conditions and presentations such as colic and plagiocephaly,1,17; however, data showing benefit are lower level of evidence or inconclusive.18,19 We have to then question as to why some studies indicate benefit of manual therapy when compared to others. We hypothesized this is likely due to the difference in neurophysiological response to the force impulses applied in the different forms of manual therapy received by this child. In the case described, there are different methods of force application involved. Practitioner 1 used manual therapy incorporating a shorter duration/higher velocity compared to Practitioner 2, who used a touch-and-hold approach. When aiming to generate a neuromusculoskeletal response, the stretch of target tissue and activation of muscle spindle cells and/or Golgi tendon organ benefits from specific force parameters. Research has demonstrated 2 key components in initiating a neurophysiological response during high-velocity/low-amplitude (HVLA) manipulation: duration of thrust input of less than 100ms, and a rate of force production exceeding 300N/s.5,6 In order to reach the target of 300N/s and thrust duration of less than 100ms, the proposed force of 7N for neonates would be inadequate to elicit a neurophysiological response unless performed within 24 milliseconds. In the case of Holm,18 the light-touch therapy involved may not have been adequate to cross the threshold of neurological response, thus being unable to create cortical changes required for changes in behavioural presentation.18 Future research may benefit from further identifying differences in outcome based upon the method of manual therapy used, forces applied, and whether they would have crossed this threshold for neurophysiological activation.

An additional factor to be considered is the change in neural afference from cranial dural systems over time; data indicates that after five months of age a decline in synaptic density occurs in dural innervation.19,20 Prior to 5 months of age there is strong synaptic density of trigeminal afferent neurons from cranial dural systems, most prominently at the time of birth, as a part of adaptation to extrauterine life. With a reduction in synaptic density occurring at the point of mechanical stimulation, this may impact on the effectiveness of manual therapy when applied to the cranial region. This case commenced treatment prior to 5 months of age but the duration of treatment continued beyond this age which may have impacted on treatment effectiveness of Practitioner 2 using therapy focussed on restoration of cranial motion when compared to Practitioner 1’s use of a mechanical device and restoration of cervical spine motion; a region of greater synaptic density and mechanoreception.4

There are 2 potential mechanisms for the changes that we observed: local musculoskeletal effects and improved neurological stimulation. This infant had been identified as having decreased general movements of the right arm, raising suspicion of a cortical lesion or pathology. Upon his second review with Practitioner 1, asymmetry of passive range of motion was observed between the left and right sides, with pain-based behaviour present upon provocation of the right shoulder joint. Previous literature has indicated adverse experiences, such as pain or discomfort, may impact on infant brain development,9 which may contribute to the gross motor delays observed with this case.

Evidence-based practice takes into consideration 3 key tenets: best available evidence, practitioner experience, and patient values. With conflicting evidence available supporting the role of light touch therapy, and a lack of response that questions the effectiveness of the treatment provided by Practitioner 2, a discussion should have occurred with the patient’s caregivers with the recommendation of obtaining treatment from an alternative practitioner or health care professional. We do have to be mindful of the limitations of drawing outcome conclusions from a single case study. In this instance, natural history cannot be excluded, regardless of how the timeline reads.

There are limitations within case studies, and in this case study in particular, as there are many variables that could influence the outcome observed. We cannot determine if the changes observed are the result of natural history, practitioner bias, variation in technique application or variation in force application. The variation of force application itself has limitations as neither practitioner recorded their forces during treatment, and data indicates practitioner estimation typically to be incorrect by a factor of 3-fold.15 However, the variation in response between 2 practitioners in this case may provide a direction for future research studies: the inclusion and recording of force data. By incorporating force data, future studies may be able to identify conditions that respond better with inputs that reach neurophysiological threshold compared to those that do not.

Conclusion

Various treatment modalities may influence the outcome of treatment via a mechanism of normalising afferentation to the brain from head, spine and extremity inputs. The amount of force being used as a part of manual therapy is one contributor to the afferentation that may be sufficient enough to evoke corrective neurophysiological reflexes beneficial to normalizing aberrant infant reflexes. Here we propose that the increased threshold of a mechanical manipulation device as a part of a multimodal treatment approach may be better than light touch or light mobilisations and may promote improved treatment responses. Future research on the afferent bursts associated with different manual therapy treatment modalities in adults and specifically infants will provide important information in selecting therapy for infants. At this time, it is not known if increased forces used in different forms of manual therapy provide different afferent bursts and whether these bursts stimulate a normalisation of neurophysiological functioning.

Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.

Written informed consent was obtained from the minor(s)’ legal guardian/next of kin for the publication of any potentially identifiable images and data included in this article.

Authors’ contributions

All authors were involved in the synthesis and development of the manuscript. CF collated case data and prepared case presentation. All authors contributed to writing the manuscript. All authors read and approved the final manuscript.