Distractibility after acquired brain injury: advancing diagnosis and identifying biomarkers

Acquired brain injury patients frequently report an increased sensitivity to sensory stimuli following their brain injury compared to their pre-injury state (i.e., post-injury sensory hypersensitivity). Since post-injury sensory hypersensitivity can negatively impact quality of life, it is crucial to have appropriate assessment and treatment methods. However, adequate assessment and treatment is hindered by a lack of appropriate diagnostic tools as well as limited knowledge about the underlying mechanisms of self-reported post-injury sensory hypersensitivity (Chapter 2).

To address these issues, we developed the Multi-Modal Evaluation of Sensory Sensitivity (MESSY), a patient-friendly questionnaire that assesses sensory sensitivity across multiple sensory modalities (Chapter 3). Moreover, we demonstrated that the MESSY has adequate psychometric properties in neurotypical adults and is sensitive to sensory hypersensitivity in chronic stroke, traumatic brain injury, and brain tumour patients. After contributing to the improvement of the assessment of self-reported post-injury sensory sensitivity, we were able to start examining its underlying behavioural and neural mechanisms. In Chapter 4 we present evidence supporting a relationship between sensory sensitivity and selective attention. This is supported by Chapter 5 in which we demonstrated a potential relationship between post-stroke visual hypersensitivity and impaired selective attention and lowered sensory thresholds. To explore the neural basis of post-injury sensory hypersensitivity, we conducted a systematic literature review (Chapter 6), a multiple case study (Chapter 6), and a lesion-symptom mapping study (Chapter 7). Our studies revealed an involvement of the insula, thalamus, basal ganglia, as well as two white matter tracts (fronto-insular tract 3, uncinate fasciculus) in post-stroke sensory hypersensitivity. The relationship between post-stroke sensory hypersensitivity and these brain structures can be understood through their role in selective attention, sensory appraisal, and auditory processing.

Overall, the findings of this thesis provide first-hand evidence for a relationship between self-reported sensory hypersensitivity after acquired brain injury and specific behavioural (selective attention, sensory thresholds) and neural mechanisms (damage to sensory processing regions in the grey or white matter). Moreover, this thesis demonstrates that sensory hypersensitivity is present after different types of brain injury, across different sensory modalities, and in the (sub)acute and chronic stages after injury. By contributing to scientific advancement and providing a patient-friendly diagnostic tool, this thesis has the potential to improve patient care and in turn the quality of life of acquired brain injury patients with post-injury sensory hypersensitivity.