Papini, Chiara
(2020)
Visual and neuropsychological outcomes following paediatric optic pathway glioma.
PhD thesis, University of Nottingham.
Abstract
Survival rates for children with brain cancer have dramatically increased in the recent decades, but evidence demonstrates long-term physical impairments, academic difficulties and neuropsychological deficits even among children with non-aggressive tumours and treatments. Children with optic pathway glioma (OPG) are at risk of neuropsychological difficulties due to the resulting visual impairment, the neural damage of the tumour itself and its treatment, and the comorbid neurodevelopmental disorder called Neurofibromatosis Type 1 (NF1). Yet, the literature on the sequelae of OPG beyond vision is scarce. This thesis is a comprehensive evaluation of long-term visual and neuropsychological outcomes in a group of 12 children who were diagnosed with a glioma in optic pathway, who received either chemotherapy or no treatment for their tumour.
On the ophthalmic exam, children demonstrated a significant structural and functional damage to the optic pathway in terms of reduced thickness of the retinal nerve fiber layer and as well as poor visual acuity. Visuo-perceptual and visual-motor abilities, which reflect the ability to process of physical and asemantic stimuli, were significantly hindered and half of the sample performed below the level expected for their age in this domain (Chapter 3).
On the cognitive assessment, children had preserved reasoning abilities (both verbal and visuospatial), but mild difficulties in working memory and processing speed, similarly to other brain tumour survivors. Core scholastic abilities of reading and maths comprehension were intact, but children had mild problems in writing and oral language. Only a minority of children (mostly with NF1) showed severe problems in these domains (Chapter 4).
Significant associations were found among measures of vision and visual perception; cognitive and scholastic abilities were associated with each other, but not with visual perception. Among the risk factors, younger age at diagnosis was associated with poor visual outcomes in the best eye and poor binocular vision had a negative impact on visuoperceptual, cognitive and scholastic abilities that heavily relied on sight. In addition, children with NF1 tended to underperform, unlike children without NF1 (Chapter 5).
Finally, participants were examined on a series of abilities (i.e., fine motor control, attention, short-term and working memory, mathematics and English comprehension), using parallel tasks that rely on either visual or auditory input. In comparison to a large group of typically developing children (N = 96), OPG survivors performed overall in line with the level expected for their age in both visual and auditory domains, although some children with NF1 exhibited problems in maths and English comprehension. In addition, strong significant correlations between the two ophthalmic measures and neuropsychological skills indicated that more severe structural and functional damage in the best eye was associated with faster responses on the auditory attention task. This result, in combination with the mild working memory difficulties reported with the standardised assessment, suggests that a compensatory mechanism in the auditory modality might take place in children with OPG, but this does not enable them to develop superior auditory abilities (Chapter 6).
Overall, this study demonstrated that children with OPG experience significant visual and visuo-perceptual problems, as well as mild and specific cognitive and scholastic difficulties. About half of the children were at risk of great visuoperceptual problems, while only a minority was specifically at risk of severe underperformance in terms of intellectual and academic functioning. Children with OPG do not develop superior auditory skills to compensate for the loss of sight.
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