Executive functioning and functional connectivity differences persist four years after a minor stroke or transient ischaemic attack: the effect of ageing and cerebrovascular disease processes

While a minor cerebrovascular event (CVE), including a minor stroke or transient ischaemic attack (TIA) is typically characterised by no persistent functional impairments, there is increasing evidence of sustained subtle cognitive impairment following such events. However, reports of cognitive impairment differ significantly across studies due to a range of methodological and clinical differences. This thesis aimed to further develop our knowledge of the cognitive profile following a minor CVE, including which domains, if any, are affected following the event, the severity of these disturbances, whether the presence or absence of neural damage affects these domains and whether these disturbances are associated with ageing and cerebrovascular disease processes. In the first third of this thesis, we extended our knowledge of the cognitive profile of a minor CVE. After controlling for the effects of age and vascular risk factors, we found no differences between minor stroke, TIA and mimic-CVE event types on a global cognitive screening tool and a verbal fluency task over the first year post-event. However, we found the presence of vascular risk factors independently affected cognitive ability which indicates that reports of cognitive impairment in minor CVE patients may be attributed to the high prevalence of chronic vascular risk factors in such patient groups. In the second two thirds of this thesis, we further investigated the cognitive profile following a minor CVE using a neuropsychological battery, cued-trials task switching paradigm and magnetic resonance imaging using a resting-state functional connectivity (rsFC) analysis. Minor stroke and TIA patients did not differ on the task-switching or neuropsychological measures, however, increased connectivity in the frontoparietal network was associated with faster performance on a measure of executive functioning in the minor stroke group but not the TIA group. Controls displayed a different pattern of rsFC to minor CVE patients. Finally, we found persistent executive dysfunction in one-quarter of minor CVE patients, irrespective of the presence or absence of neural infarction. Together, these findings suggest that transient or relatively minor cerebrovascular events are associated with persistent disruption of functional connectivity of neural networks and cognitive performance. These findings suggest a need for novel interventions beyond secondary prevention to reduce the risk of persistent cognitive deficits.