Imaging of hypoxic ischaemic encephalopathy in the term neonate

PhD by publication. In 2000 an encephalopathic neonate who had been exposed to an episode (or episodes) of hypoxia/ischaemia (HIE) would probably have been imaged with a cranial ultrasound and may have received an MRI in selected teaching hospitals. MRI would probably not have been used in neonatal units without teaching hospital paediatric MR units. The cranial ultrasound would have allowed assessment for hydrocephalus, germinal matrix and intraventricular haemorrhages, parenchymal cysts, mass lesions and gross congenital brain malformations. MRI for neonates was in its infancy with early case reports and case series of patterns of injury and things to look for on imaging both in HIE and in clinical mimics such as hypoglycaemia. Imaging protocols were starting to be tailored to neonates and new technology and imaging sequences (such as MR spectroscopy and diffusion weighted imaging) were being applied to imaging of the neonatal brain. The clinical impact of HIE on subsequent developmental impairment and the anatomical substrate of cerebral palsy due to HIE was starting to be acknowledged and correlated. Neonatal care of the neonate with HIE was evolving and improving, particularly in terms of ventilation and prevention of hypocarbia due to overventilation. In 2020 any neonate who requires unexpected neonatal care, let alone an encephalopathic neonate, will be investigated with cranial ultrasound and MRI of the head. The cranial ultrasound will often be repeated regularly through the duration of their care on the neonatal unit. The MRI will often be performed at the local hospital and will involve the use of sequences such as DWI, susceptibility weighted imaging, diffusion tensor imaging and MR spectroscopy. The MR scanner may be on or near the neonatal unit and specific incubators may be used to transport the neonate to and from the scanner. MRI after myelination is complete (beyond two years of age) will provide exquisite anatomical information if the child goes on to develop cerebral palsy. The report of the MR scan will often include reference to clinical and radiological mimics of HIE, reference to specific anatomical substrates for subsequent neuro-disability and information regarding prognosis. Some of the information included in the report will reference new knowledge available to the reporting radiologists regarding in utero injury to the fetus. Providing an accurate estimation of the timing of the insult (or insults) is of increasing importance to the reporting radiologist and their hospital and earlier imaging (within the first days of life) with DWI to aid the reporter with the issue of timing and to exclude post-natal causes of brain injury and encephalopathy such as metabolic disorders, infection and/or cardio-respiratory dysfunction is required. It is now known that some pathologies thought only to affect term neonates may affect the preterm brain and also that pathology previously considered to only affect the preterm brain may affect the term neonate. The use of early MRI should now include statements from the radiologist regarding likely prognosis for the term neonate with HIE. There has been a huge expansion in the interventions available to the treating neonatal team and the impact on outcome from interventions such as therapeutic hypothermia has seen a dramatic improvement in neurological outcome for the term infant with HIE. The interventions have also raised doubts about the applicability of previously held dogma regarding the duration and nature of HIE at term. In the near future clearer guidelines should allow the reporting radiologist to better define the nature and timing of the insult causing HIE, to exclude mimics and to provide better prognostic information to the clinical teams, to focus interventions and reduce subsequent neuro-cognitive disability. This commentary will review the literature in brain MR imaging of the term neonate with HIE over the last 20 years with specific reference to my published papers which have contributed to advances in the field and which are included at the end of the thesis. Papers for inclusion in thesis Initial experience of an investigational 3T MR scanner designed for use on neonatal wards Involvement of the anterior lobe of the cerebellar vermis in perinatal profound hypoxia. Anatomic localisation of dyskinesia in children with ‘profound’ perinatal hypoxic-ischemic injury. Isolated superior cerebellar vermis injury: a consequence of hypoxic ischemic injury A review of fetal brain pathology acquired in utero Watershed stroke – an unexpected complication of respiratory syncytial virus bronchiolitis: a case report Perinatal Arterial Ischemic Stroke in term babies Aetiological investigation in early developmental impairment – are they worth it? ..