Dr Terry Quinn (Joint Stroke Association / CSO Senior Clinical Lecturer) has a clinical and research interest in post stroke cognitive decline. Supported by a Stroke Association Priority Program Grant he is pursuing a portfolio of work themed around how to assess cognition and mood in the Acute Stroke Unit. Terry will be sharing some of the findings from this and other work at the BGS Spring Meeting in Newcastle as part of a themed session on dementia. Terry tweets about all things cognitive @DrTerryQuinn and in his role as Coordinating editor of the Cochrane Dementia Group @cochraneDCIG
Specialist societies, clinical guidelines and audit standards all encourage us to assess cognition when patients present with stroke. Intuitively this seems like a sensible idea. We know that patients fear problems with memory and thinking more than they fear physical disability and we know that cognitive problems are extremely common in the post stroke period. What is less clear is how we should assess cognition in stroke.
We have an ever increasing number of cognitive screening tools available to us. However, most were designed to assess healthy older adults and may not be suitable for use in the stroke unit. The stroke and non-stroke related impairments seen in acute stroke patients can complicate assessment with a standard cognitive test. For example, how should we perform a diagnostic interview with a person who has aphasia? Similarly, completing a pencil and paper based memory task will be difficult for the person unable to hold a pen due to hemiparesis. Common non-stroke impairments such as hearing and visual loss, can further compromise performance on cognitive tests.
Current guidelines favour early cognitive testing, but how early is ‘early’? Trying to perform a cognitive assessment in the first hours after stroke should allow prompt treatment and ensure that all admissions have some form of testing. However, in the messy world of acute stroke care, very early assessment presents many difficulties. We must remember that stroke is a major medical illness. Lengthy neuropsychological assessments may be neither feasible nor acceptable to the patient. Repeated assessment of cognition following stroke has shown that almost all people have a degree of cognitive impairment in the first days following a stroke event. Thankfully, in many patients this improves over the next few weeks. If we assign a label of post stroke cognitive impairment based on very early testing we risk over diagnosis and possibly causing unnecessary stress and investigation.
If we are able to complete some form of cognitive screen following stroke, interpreting the results presents further difficulties. A ‘positive’ screening test could represent cognitive problems specific to the stroke event. Equally, the abnormal cognitive test may also be an indication of (undiagnosed) pre-stroke cognitive problems; a delirium process or an underlying mood disorder. In stroke assessment we often speak of the ‘four Ds’: dementia, delirium, dysphasia and depression and we need to be mindful of all of these when interpreting cognitive tests.
So should we abandon cognitive assessment in stroke? This would be throwing the baby out with the bath water. Stroke is a brain disease and as such, testing memory and thinking should be part of the initial work-up. However, clinicians must be aware of the limitations of standard cognitive tests in the context of stroke and appreciate the dynamic nature of cognitive change in the acute stroke period. Accepting these caveats, what should we do when we detect cognitive issues in a person with recent stroke? That…..should be the subject of another blog.