Search

Background. Prognosis of long-term motor outcome of acute stroke patients with severe motor impairment is difficult to determine. Objective. Our primary goal was to evaluate the prognostic value of corticospinal tract (CST) injury on motor outcome of the upper limb compared with motor impairment level and lesion volume. Methods. In all, 10 acute stroke patients with moderately severe to severe motor impairment of the upper limb underwent diffusion tensor imaging (DTI) and testing of upper limb strength and dexterity at acute, subacute, and chronic poststroke time points. A density-weighted CST atlas was constructed using DTI tractography data from normal participants. This CST atlas was applied, using a largely automated process, to DTI data from patients to quantify CST injury at each time point. Differences in axial diffusivity (AD), radial diffusivity (RD), and fractional anisotropy (FA) of the ipsilesional CST relative to the contralesional CST were measured. Results. Acute loss in CST AD correlated most strongly and significantly with subacute and chronic strength and dexterity and remained significant after adjusting for acute motor impairment or lesion volume. Subacute loss in CST FA correlated most strongly with chronic dexterity, whereas subacute behavioral measures of limb strength correlated most strongly with chronic strength measures. Conclusions. Loss in acute CST AD and subacute CST FA are strong prognostic indicators of future motor functions of the upper limb for stroke patients with substantial initial motor impairment. DTI-derived measure of CST injury early after stroke may have utility in health care planning and in design of acute stroke clinical trials.

Background. Somatosensory input to the motor cortex may play a critical role in motor relearning after hemiparetic stroke. Objective. The authors tested the hypothesis that motor recovery after hemiparetic stroke relates to changes in responsiveness of the sensorimotor cortex (SMC) to somatosensory input. Methods. A total of 10 hemiparetic stroke patients underwent serial functional magnetic resonance imaging (fMRI) during tactile stimulation and testing of sensorimotor function over 1 year—at early subacute, late subacute, and chronic poststroke time points. Results. Over the subacute poststroke period, increased responsiveness of the ipsilesional SMC to tactile stimulation of a stroke-affected digit correlated strongly with concurrent gains in motor function. Increased responsiveness of the ipsilesional and contralesional SMC over the subacute period also correlated strongly with motor recovery experienced over the first year poststroke. Conclusions. These findings suggest that increased responsiveness of the SMC to somatosensory stimulation over the subacute poststroke period may contribute to motor recovery.

Functional brain imaging studies have provided insights into the processes related to motor recovery after stroke. The comparative value of different motor activation tasks for probing these processes has received limited study. We hypothesized that dif ferent hand motor tasks would activate the brain differently in controls, and that this would affect control-patient comparisons. Functional magnetic resonance imaging (MRI) was used to evaluate nine control subjects and seven patients with good recov ery after a left hemisphere hemiparetic stroke. The volume of activated brain in bilat eral sensorimotor cortex and four other motor regions was compared during each of three tasks performed by the right hand: index finger tapping, four-finger tapping, and squeezing. In control subjects, activation in left sensorimotor cortex was found to be significantly larger during squeezing as compared with index-finger tapping. When com paring control subjects with stroke patients, patients showed a larger volume of acti vation in right sensorimotor cortex during index-finger tapping but not with four-fin ger tapping or squeezing. In addition, patients also showed a trend toward larger activation volume than controls within left supplementary motor area during index- finger tapping but not during the other tasks. Motion artifact was more common with squeezing than with the tapping tasks. The choice of hand motor tasks used during brain mapping can influence findings in control subjects as well as the differences identified between controls and stroke patients. The results may be useful for future studies of motor recovery after stroke. Key Words: Stroke—Motor recovery—Functional MRI.