The cognitive profile of children treated with radiation for acute lymphoblastic leukaemia

Abstract

Background. Cranial radiation is part of a treatment protocol for childhood acute lymphoblastic leukaemia (ALL) in South Africa. Radiation is known to disrupt the myelination and integrity of white matter tracts in the brain. Associated cognitive impairment has been well documented in other countries, but not to the same extent in the multicultural and multilingual South African context.

Objectives. The current study focused on the assessment of memory and learning, two imperative cognitive functions. A quantitative evaluation of verbal and visuospatial memory performance in a cohort of ALL patients was done in order to establish whether there was a difference in performance between verbal and visuospatial tasks.

Methods. Eight patients with a low socio-economic background and being educated in their second language were included in the cognitive evaluation. All had received 18 Gy of radiation as part of their treatment protocol and were on maintenance treatment at the time of the study.

Results. In all the patients, primary cognitive impairment was demonstrated in ostensibly right hemisphere visuospatial tasks in comparison with ostensibly left hemisphere verbal tasks. Because deficits in visuospatial attention and working memory were identified, qualitative analysis of the results suggested that the white matter tracts in the right frontoparietal region and prefrontal cortex may be particularly vulnerable to radiation injury.

Conclusion. The study findings support vulnerability of the right hemisphere, particularly the right frontoparietal region and prefrontal cortex, to radiation injury. The decline in visuospatial cognitive abilities has major implications for second-language learners, as visuospatial learning is particularly important for them.