Our study provides the first standardised description of brain neuroimaging findings among children with CP in an LMIC using the MRICS. It demonstrates the utility of brain MRI in assessing children with CP and the value of the MRICS in generating standardised, thus comparable data. This study contributes significantly to the limited evidence on MRI patterns in children with CP. Our study provides some evidence on the aetiological underpinnings of CP and is an important first step towards the development of preventive strategies in LMICs.
Our findings confirm that white matter injury is the most common injury type seen on MRI among children with CP, and that MRI patterns are associated with the type and timing of the causal of CP. Nearly half the children had predominant white matter injury, which is consistent with findings from a large scale international study demonstrating the application of the MRICS on data from 20 European CP registers.[11] The proportion of children with predominant white matter injury in our study is also congruent with other CP cohorts.[12, 19]
Normal MRI findings were reported among a quarter of children with CP, a higher proportion than in other CP cohorts.[20] This suggests that causal pathways additional to maldevelopment and injury to the developing brain exist and indicates the potential for genetic or metabolic causes. Some studies indicate that genetics may play a role in the causation of CP.[21] Genetic aetiology remains unexplored in LMICs, where it is of particular importance due to the high rates of consanguinity in some countries, which increase the risk of recessively inherited diseases.[22] Studies exploring the genetic basis of CP may ultimately contribute to the establishment of causation among a proportion of children with CP, particularly those without a well-characterized risk factor and brain injury or maldevelopment, thus identifying further opportunities for prenatal screening and prevention. In our study however, the exact age of the children at the time of their MRI scan was not known and nearly half the children with normal MRI findings were under the recommended age (i.e. after 2 years) at which MRI should be performed for classification using MRICS.[12] Patterns such as mild periventricular or basal ganglia or thalamus lesions may have been missed in some of these children due to developing myelination in the first years.[12]
Among children with neonatal jaundice, kernicterus is implicated in brain injury leading to CP and is typically associated with grey matter injury.[23] In our cohort, a proportion of the children with neonatal jaundice had predominant white matter injury, suggesting additional aetiologic mechanisms and the likely interplay between different causal pathways of CP. The MRICS allows description of typical MRI patterns of CP associated with specific timing of vulnerability in different areas of the brain.[12] The predominance of white matter injury in our cohort indicates the timing of the lesions causing CP in the third trimester, which is commonly induced by hypoxic-ischaemic and/or infectious mechanisms.[12] Pre-perinatal maternal infection and suboptimal immunization rates in a proportion of our cohort support this finding.
Several studies report a strong link between maternal infection and white matter injury leading to CP, particularly in preterm births.[24] Intrauterine infections can cause cerebral hypoperfusion of the developing brain resulting in hypoxic-ischaemic injury and/or induce production of pro-inflammatory cytokines which can lead to damage of oligodendrocyte progenitors and thus induce white matter injury.[25] A systematic approach to prevention, identification and treatment of maternal infections is therefore vital to the prevention of CP. Antenatal care can facilitate greater awareness of infection control measures and ensure better understanding of warning signs during pregnancy and childbirth, access to micronutrient supplementation, and immunization, all of which can reduce risk of infections. Perinatal practices, such as interventions to prolong pregnancy, administration of antenatal steroids to mothers expected to deliver prematurely, and optimal delivery care, can also help avert premature birth and obstetric mishaps commonly leading to CP. This is observed in a proportion of our cohort with white matter injury, particularly those with reported birth asphyxia.[26]
Although MRI was not used as a diagnostic tool in this study, it is highly predictive in identification of CP with 86–89% sensitivity at as early as five months corrected age.[27] Diagnosis of CP is typically based on clinical presentation supported by parent reports on attainment of motor milestones. This applies particularly in LMICs where the use of best practice tools, such as the General Movements Assessment and Hammersmith Infant Neurological Examination, is limited and diagnosis is delayed,[26] which often leads to more severe impairment, poor quality of life and high mortality.[28–30] Early diagnosis allows early intervention, thus providing potential to harness neuroplasticity for enhanced function and participation of children with CP.[31]
International guidelines recommend investigation of all suspected cases of CP by neuroimaging.[27, 32] When safe and feasible, MRI can aid in early diagnosis and support counselling on prognosis, both of which can enhance caregiver wellbeing, an often overlooked consideration in planning interventions for CP.[33] Several studies report correlations between MRI patterns and type, severity, and associated impairments of CP, all of which are vital to guiding clinicians in predicting future functional outcomes of children with CP.[34–36] For example, GMFCS level V predominated in over half the children with brain maldevelopment, an MRI finding predictive of non-ambulant CP.[37] Furthermore, a prospective longitudinal cohort study of children with CP in the Netherlands reports that MRI patterns can support early identification of children at risk for impaired cognition.[38]
The principal contribution of neuroimaging are that it enables better understanding of the aetiopathogenesis of CP.[10] Advanced understanding of the specific MRI patterns of CP and their potential link to specific etiologic events may inform prevention. Our study demonstrating the applicability of the MRICS in a CP cohort is an important step towards the development and implementation of preventive strategies in an LMIC. There is an urgent global need for clinician training to promote evidence-based approach, including the use of the MRICS to ensure better understanding of the various MRI patterns observed in CP, and their implication for prevention and clinical practice. The MRICS and the relevant resources developed by the SCPE group can serve as a valuable training tool to support this.[12]
Study limitations
Our study has some limitations. Firstly, our study cohort, identified prospectively using hospital-based surveillance and strict diagnostic criteria, is not population representative. It includes all children presenting with CP over a six-month period and brain MRI scans were available for 34.5% of the children. These are the children for whom the Vietnamese clinicians requested an MRI. Although similar clinical characteristics are noted in children with and without MRI data in our study, the reason for requesting an MRI was not documented, thus raising the potential for bias in the cohort e.g. severity of impairments, cost of neuroimaging and overall access to MRI. Secondly, MRI reports were obtained from existing hospital records and classified retrospectively by investigators using the MRICS without access to the images or the radiologists who performed, interpreted, and reported the MRI. However, very good interrater reliability is reported with use of MRICS rating both images and reports.[12] Thirdly, data on the timing of the MRI scans were not available, and it is known that interpretation of brain MRI is age dependent.[39] Fourthly, data were not available on whether brain involvement was unilateral or bilateral; this is often crucial for predicting functional outcomes.[11] Finally, we relied on clinical history, assessment conducted by clinicians and existing hospital records for the assessment and documentation of associated impairments.