Characterising and predicting apraxic deficits in patients with chronic aphasia caused by left hemisphere stroke

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This study will investigate apraxia after stroke, a condition which significantly affects the lives of 30- 40% stroke patients (some 25,000 people annually) making them unable to care for themselves. Apraxia causes problems with planning and executing everyday actions, such as brushing teeth, getting dressed, or making a cup of tea. It can occur both in the dominant and non-dominant hand and is not due to muscle weakness or sensory loss. Apraxia is often not recognised when patients are admitted into stroke units because identification requires detailed neuropsychology testing which is not standardised and is time-consuming. As a result, patients may miss the opportunity to get appropriate rehabilitation for this disabling condition. Studies investigating language impairments (aphasia) after stroke have faced similar challenges because of lengthy tests and difficulties targeting appropriate rehabilitation. Researchers at the University of Cambridge have recently implemented new analysis techniques on detailed language assessments. This has allowed identification of behavioural components causing aphasia that could distinguish specific language impairments from impairments caused by other cognitive problems following a stroke. These have been linked to the patient's brain scans to identify the brain regions causing the impairments. Further work has demonstrated the ability to predict impairments based on brain scans. The research group is currently working to validate these methods in a large cohort of patients over time to identify factors leading to recovery. This proposal aims to apply the same analysis techniques to identify apraxia in the same patient cohort studied for language deficits. Apraxia often co-occurs with aphasia after stroke, and some of the deficits in both disorders may be shared. Stroke patients who have participated in the aphasia studies outlined above will be invited to take part in the study. They will undergo detailed tasks of apraxia testing. A subgroup of patients with apraxia who have problems recognising gestures will undergo more detailed gesture recognition and imitation tasks during functional neuroimaging. This is to differentiate brain activity and connectivity changes in speech and action understanding. Any errors patients make on apraxia tasks will be grouped into simpler components. These, combined with brain imaging markers, will be used to create predictions to accurately distinguish problems and brain lesions relating to apraxia from those related to aphasia and from those caused by more generic cognitive impairments after stroke. This will enable us to identify simpler core factors associated with apraxia and the areas of brain damage associated with them, to predict patient apraxia problems and guide future rehabilitation needs. The key outcomes of the proposed studies will be the creation of accurate screens for predicting whether patients have apraxia after stroke, using simpler tasks than currently, and brain imaging. These will then allow for quicker, easier testing for this condition after stroke and will enable selection of patient-centred therapies for neuro-rehabilitation. Future studies arising from this work will aim to validate the new diagnostic and prediction models created in this study by testing them in a longitudinal cohort of patients, tested both at acute and chronic stages after stroke, to identify if they can accurately predict recovery from apraxia from the acute to the chronic stages after stroke.