Individual recovery of cognitive defects after stroke

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Stroke is the leading cause of major disability throughout the developed world with many individuals suffering from long term deficits in speech, perception, motor control and memory. Some of the first questions of acute stroke patients and their families are: 'What is the likelihood for a full recovery? What is a realistic recovery in my case?' So far, there is no individual response to this urgent question. Currently our advice regarding long-term recovery is only informed by very general observations. About two-thirds of the cognitive deficits evoked by an acute stroke will recover; one-third of the patients will experience chronic impairments. We propose that brain imaging can be combined with acute behaviour to provide an important biomarker for individual long-term prognosis. Improved prognosis could not only provide realistic expectations, but would also guide individually tailored treatment (e.g. rehabilitation versus compensation). As a showcase for the general principle we will concentrate on the consequences of stroke to the right hemisphere, namely the disorders of spatial orientation and attention. These deficits are strong predictors for poor recovery on a wide range of everyday tasks including poor motor recovery, general cognitive dysfunction and resistance to rehabilitation. Based on our previous work, we now have clear predictions regarding the anatomical underpinnings of common right hemisphere disorders. Specifically, injury to perisylvian regions leads to passive biases in posture and gaze, as well as body-centered biases during active perceptual neglect tasks (which we refer to as egocentric neglect). On the other hand, more posterior injury appears to lead to spatial biases within individual objects (allocentric neglect). In contrast, injury to the temporoparietal junction results in extinction (a bias when confronted by multiple objects that share a simultaneous onset). Our objective is to conduct the first prospective longitudinal study informed by these recent findings in order to understand individual long-term recovery. We assert that the combination of acute structural and functional brain imaging, as well as a carefully designed set of acute and outcome behavioral measures, will allow us to understand the underlying physiology and help us determine which measures are required for accurate prognosis.