Cognitive and intellectual functioning in leukodystrophy patients: a systematic review

'Leukodystrophies' encompass a group of genetic disorders affecting brain white matter, mostly characterized by neurological deterioration. Manifestations include mood changes, cognitive decline, motor dysfunction, and often early death. Underestimation of the cognitive decline may result in a lack of suitable interventions and adequate guidance. This systematic review aims to gain insight into available information on the cognitive and intellectual profile of leukodystrophy patients, providing a basis for further research.

MEDLINE, EMBASE and PsychINFO were searched for studies examining processing speed, attention, memory, language, social cognition, visuospatial functioning and construction, and intelligence in patients with any type of confirmed leukodystrophy utilizing standardized neuropsychological tests. The included studies were analyzed to determine whether there are similarities among the various types of leukodystrophies and their associated cognitive and intellectual profiles. Due to significant variability in neuropsychological assessments, data synthesis was performed narratively rather than via meta-analysis.

Thirteen group studies and twenty case studies were included, with most group studies rated as moderate to high quality. On group level, cognitive and intellectual functioning varied widely between different leukodystrophy types. Intelligence and information processing speed were most frequently affected. A consistent finding was that the age of onset significantly influenced cognitive outcomes, with childhood-onset leukodystrophies generally associated with earlier and greater cognitive and intellectual impairments than adult-onset leukodystrophies.

Although intelligence and cognition are obviously affected in the course of leukodystrophies, information processing speed being impaired relatively frequently, the specific profiles of cognitive and intellectual impairment are currently unclear, while such insight is crucial for proper guidance. Well-designed future studies are needed to establish a clearer cognitive and intellectual profile in leukodystrophies, their subtypes and during their disease course. Results will be the basis for suitable guidelines for testing and set the foundation for development of appropriate outcome measurements for therapy trials.