A Blood Flow Technique for Determining the Cause of Dementia

Dr Chris Levi (Chief Investigator) (John Hunter Hospital), Dr G Bateman, Dr C Selmes (Co-Investigators, John Hunter Hospital); Dr P Schofield (Co-Investigator, James Fletcher Hospital)

Dr Chris Levi, chief investigator of this research project, when awarded a Brain Foundation grant for this project, noted that, “Brain Foundation funding will allow us to conduct a pilot study titled ‘Assessment of cerebrovascular compliance in cognitively impaired patients’.  This study examines a newly developed technique aimed at differentiating patients with probable Alzheimer's disease, vascular dementia, and cognitive impairment without dementia. The more accurate differential diagnosis of these diseases will permit the formulation of a more appropriate strategy in the medical treatment of the patient, as well as provide more accurate information to patients, family members, and/or carers.

Dr Levi’s previous project, “Brain Impairment after Cardiac Surgery” attracted funding of $15,000 from the Brain Foundation in 1999. Preliminary results were presented at the Stroke Society of Australasia’s Annual Scientific Meeting in New Zealand in September 2001. The abstracts from these presentations are to be published in the Journal of Clinical Neuroscience. An abstract was also accepted for the American Stroke Association’s 27th International Stroke Conference held in February 2002, and will be published in Stroke.

The background to the study is that coronary artery bypass grafting (CABG) results in stroke in up to 5% of cases, and long-term cognitive deficits in up to 30% of cases, with cerebral embolism being a common cause. Emboli can be detected in the basal cerebral arteries using Transcranial Doppler (TCD). Microembolism at the cerebral arterial boundary zones, or “watersheds”, is a common cause of cerebral ischaemia. It is also known that the processing of complex visual information is localised in the parieto-occipital cortex – a “watershed” area. Dr Levi and his team hypothesised that visual processing will be particularly vulnerable to ischaemic brain insult resulting from microembolism.

Patients undergoing CABG were assessed pre- and three month post-operatively by means of neurological examination (including visual testing) and neuropsychological assessment (including tests of attention, memory, calculation, semantic language, visuo-construction and visual perception). Aortic arch atheroma was measured during surgery. Cardiac history and risk factors were collected from each patient.

Preliminary analysis of data from 16 patients reveals significant deterioration pre- to post- CABG on a measure of visual perception. Additionally, 56% of patients show decline on at least one (of three) tests of visual function compared with 50% showing decline on at least one (of seven) measures of memory and attention. Recruitment into the study is continuing.

One conclusion of the preliminary study is that the visual test of letter recognition is sensitive to insult resulting from microembolism. The assessment tool may provide a non-invasive, simple, and cost-effective means of measuring post-operative brain ischaemia.