The time course of stroke recovery as well as the impact of exercise therapy on the pattern of (motor) recovery is poorly understood. This lecture presents the current knowledge about the predictability of the time course of body functions and activities following a stroke. There is growing evidence that the natural logarithmic pattern of functional recovery can be modified by early started, intensive task-oriented practice. However, the impact of practice on learning-dependent and intrinsic, spontaneous mechanisms of neurological recovery is not well understood. Several, probably interrelated mechanisms, have been identified that affect recovery after stroke. These mechanisms underlying recovery are highly interactive and operate within different, sometimes limited, time-windows after stroke. In this invited lecture, a hypothetical phenomenological model for understanding skill reacquisition after stroke will be presented. Subsequently, the need for elucidating the longitudinal association between neurological recovery and regaining meaningful activities will be discussed in order to understand what and how patients learn when they show functional improvement post stroke. This statement will be discussed in light of measuring serial outcomes defined at different levels of ICF post stroke. There is growing evidence that the effects of neurorehabilitation are rather adaptive (substitution) rather than based on mechanisms of ‘true neurological repair’ (restitution). Restitution seems to be restricted to a time window of the first 8 weeks post stroke within which spontaneous neurological recovery occurs. After this critical time window, upper limb recovery is mainly the result of the most efficient optimization of the intact end-effectors to accomplish meaningful tasks.
Recent studies also showed that about two-third of all stroke patients show proportionally, the same amount of spontaneous neurological recovery in the first 6 months post stroke. Roughly, this spontaneous amount of improvement accounts about 70 to 80% of the maximal available improvement on a motor impairment scale such as Fugl-Meyer-Arm score. Recent prospective studies further show that this 70% recovery rule is also applicable for other modalities such as speech in patients with left hemispheric strokes and visuospatial neglect in right hemispheric strokes. More important, patients who fail to show the expected amount of spontaneous motor recovery also fail for the other affected modalities in the same hemisphere, suggesting a common underlying biological mechanism for spontaneous neurological recovery.
Identifying and subsequently, stratifying fitters and non-fitters of this 70% recovery rule, will have an important impact on designing trials early post stroke. In addition, these studies should focus on understanding stroke recovery by studying the distinction of restitution of neurological impairments from adaptive mechanisms of motor recovery. To do that, designs are needed based on intensive serial measurements applied at fixed moments post stroke in time in which the longitudinal relationship between kinematics and neuroplasticity is investigated early post stroke.