Ayala Soriano, S;
(2016)
Characterisation of the optic radiations in children in health and disease.
Doctoral thesis , UCL (University College London).
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Abstract
The normal and abnormal development of the optic radiations through childhood was examined in terms of their anatomical development, using MRI tractography, and their functional development, using visual evoked potentials (VEPs). Neurosurgical applications of these imaging techniques were assessed. Control cohorts of 74 children and 13 adults were recruited from Great Ormond Street Hospital. The anatomical development of the optic radiations in children from birth was described using tractography. A novel method to improve tractography analysis using VEP data was developed. VEP-enhanced tractography showed a more defined optic radiation in the gathering of the visual cortex, which caused a significant reduction in the mean FA in the adult cohort. Paediatric patients diagnosed with optic nerve hypoplasia (ONH) were recruited and 23 were compared with a matched control cohort using tractography. ONH patients presented reduced mean FA in the left optic radiation. TBSS analysis of the DTI scans showed that white matter FA was also lower in other areas of the brain outside of the visual system. Two paediatric seizure patient cohorts were recruited: 21 patients with a single episode of prolonged febrile convulsions and 20 regular users of anti-epileptic medicines. Both cohorts were compared with matched control cohorts using DTI tractography. The anti-epileptic user cohort presented lower mean FA at the front of both optic radiations, but the prolonged febrile convulsions cohort had no statistically-significant differences in mean FA, compared to controls. Two brain tumour case studies demonstrated that tractography is a valuable surgical tool in complicated paediatric neurosurgical cases where detailed description of white matter tracts can improve the surgical outcome and assist with counselling patients. Two hydrocephalus case studies demonstrated that VEP-enhanced tractography offers a novel method to identify white matter tracts in cases where conventional imaging techniques provide very limited information due to highly-distorted anatomies.
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