Background
Acquired brain injury (ABI) is the term used to describe traumatic and non-traumatic brain injuries that occur after birth and a period of typical development.1 In the UK, ABI accounts for 35,000 childhood presentations to emergency departments annually. Of these, 5% have moderate to severe brain injury.2 Children with severe ABI will often have movement difficulties caused by weakness, abnormal muscle tone, poor motor control, poor concentration, fatigue and other comorbidities.3 They may also have difficulties with speech, swallowing and cognitive impairment. A subgroup of children with ABI present with a stroke like presentation limiting their activity, balance, gait and fine motor skills. They are likely to develop tightness and contractures in both the upper and lower limbs.4 This impairment leads to functional difficulties including self-care, playing with and manipulating toys, socialising with and academic activities.4 During the acute phase, children with moderate to severe ABI frequently require a period of demanding medical and rehabilitative care to optimise their long-term capabilities and quality of life through neuroplasticity.5 This acute care can last up to 12 months following the initial brain injury which often requires a wide range of neurorehabilitation measures from a multidisciplinary team.6
Early and effective neurorehabilitation provision promotes a good long-term functional outcome for children with ABI.7 Active rehabilitation begins as soon as they are medically stable. The typical rehabilitation includes facilitation of movements, postural control, postural care management, constraint-induced movement therapy (CIMT), strength training, dysphagia and communication management; and tone medications to improve motor and functional skills through neuroplasticity.6 Recent advances in technology enable clinicians to use functional electrical stimulation, virtual reality (VR)4 and transcranial magnetic stimulation (TMS) to improve motor skills for children with central nervous system-related movement disorders.8 9
TMS is a non-invasive treatment technique.10 It is safe to use for children and adolescents with neurological conditions.11 It delivers repetitive magnetic pulses directly to specifically targeted brain areas through electromagnetic induction. TMS is applied over the scalp either on the same or opposite side to modulate cortical excitability through electromagnetic induction. In TMS, an electric charge is applied to a small coil and this produces a magnetic field perpendicular to the coil. This magnetic field creates an electrical current in the brain tissue parallel to the coil. This activates the localised neurons through cortical excitation.12 Low frequency TMS reduces cortical excitability but the high frequency increases it, thereby producing the desired therapeutic effect.13 Navigated repetitive TMS is delivered to a targeted brain area to change polarisation and it has been shown to influence cortical excitability many minutes after initial stimulation.14 This will help to facilitate, inhibit or interrupt the cortical network depending on the frequency and intensity of the stimulus, thus promoting a cortical function change through neuroplasticity.15
TMS has been widely used in adult stroke rehabilitation to facilitate cortical excitability and to promote neuroplasticity.16 Early application of TMS (from 2 weeks to 2 months, 5–15 sessions; 1–10 Hz) coupled with other rehabilitation therapy intervention has been shown to result in decreased motor impairment, improved activity and participation level in the stroke population.14 TMS has been used to treat children with neuropsychiatric disorders including children on the autistic spectrum, those with attention deficit hyperactivity disorder, obsessive–compulsive disorder and also tics.8 A systematic review investigated the effectiveness of non-invasive brain stimulation for rehabilitation of children with cerebral palsy (CP).17 This review identified 4 studies that used repetitive TMS (5–10 sessions, with each session lasting between 10 and 20 min). Three studies used inhibitory low frequency repetitive TMS over the contralateral motor cortex and one study used both high and low frequency repetitive TMS over the primary motor area. A meta-analysis of the outcome measure indicated improved upper limb function following repetitive TMS.17
It is worth noting that some literature includes children with CP as ABI. An injury to the brain occurs in very early life in CP, whereas in ABI the injury is sustained after a period of normal development.18 It could be argued that the description and presentation of CP is markedly different from those who sustained moderate to severe ABI at a later time in their childhood. Enhanced neuroplasticity in the developing brain may prove to be advantageous in rehabilitation following ABI. Structural and functional neural plasticity is attributed to change in regional volumes in brain cells or formation of neural pathways through synaptogenesis, axonal or dendritic sprouting and the creation of new neurons.19 Synaptic and intrinsic mechanism regulates neural excitability which influences neural plasticity.20 Metaplasticity, an activity-dependent modulation of synaptic plasticity was induced by TMS in adult neurological disorders such as stroke and Parkinson’s disease. TMS can be an effective tool to treat brain disorders through inducing metaplasticity.21 TMS coupled with regular rehabilitation could provide improved outcomes through neural plasticity22 and metaplasticity. If this is the case, TMS combined with intensive rehabilitation appears to be a promising new intervention approach with wider future applications for children with ABI. There is, however, limited material supporting its use in children with ABI who have a motor disorder.
The intervention effect in rehabilitation research has been widely reported using the International Classification of Functioning, Disability and Health for Children and Youth (ICF-CY) framework.23 The ICF-CY domain consists of body structures and function, activity, participation and contextual factors (environment and personal) which can be used to classify the level of functioning in childhood.6 This model can be applied to report the functional outcome of children and young people (CYP) with ABI who have impaired physical, cognitive and emotional difficulties and the impact on activity limitation and participation restriction following an intervention.6
The overall objective of this scoping review will be to examine the literature relating to the therapeutic effect of TMS in children with ABI. The outcome of this review will be categorised according to the ICF-CY dimensions. This review will help to summarise the existing knowledge base and to identify areas requiring further research.
