Does Motor Tract Integrity at 1 Month Predict Gait and Balance Outcomes at 6 Months in Stroke Patients?

Short-term and long-term predictors of balance function in stroke patients: a 6-month follow-up study

We aimed to determine early predictors of balance function (Berg Balance Scale, BBS) at 3 and 6 months after stroke using clinical, neurophysiological, and neuroimaging variables. Seventy-nine patients with hemiparesis after a stroke were included. Demographics, stroke characteristics, and clinical variables [Mini-Mental State Examination, BBS, strength in the hemiparetic hip, knee, and ankle muscles, and Fugl-Meyer Assessment Lower Extremity (FMA-LE)] were evaluated 2 weeks post-stroke, on average. Somatosensory-evoked potentials (SEP) from both tibial nerves and diffusion tensor imaging data were collected respectively within 3 weeks and 4 weeks post-onset to calculate the SEP amplitude ratio and the laterality index of fractional anisotropy of the corticospinal tract. In multiple linear regression analysis, younger age, higher FMA-LE score, and stronger hemiparetic hip extensors were independent predictors of higher BBS at 3 months post-stroke (adjusted R2  = 0.563, P  < 0.001). At 6 months post-stroke, significant predictors of higher BBS were younger age, higher FMA-LE, stronger hemiparetic hip extensors, and larger SEP amplitude ratio (adjusted R2  = 0.552, P  < 0.001), although the incremental contribution of the latter was rather small ( R2  = 0.019). We conclude that age and the initial motor impairment of the affected lower limb can inform the state of balance function at 3 and 6 months after stroke.

Prediction of the gait function using the nigrostriatal and corticoreticulospinal tracts of the affected hemisphere in a cerebral infarct: A diffusion tensor imaging study

Prognosis predictability of the nigrostriatal tract (NST) and corticoreticulospinal tract (CRT) of affected hemisphere at early stage for gait function at chronic stage were investigated using diffusion tensor tractography (DTT) in patients with a cerebral infarction. Thirty consecutive patients with middle cerebral artery (MCA) territory infarction were recruited. Functional ambulation category (FAC) was used to evaluate the gait function at chronic stage. Fractional anisotropy (FA) and tract volume (TV) of ipsilesional NST and ipsilesional CRT were determined to be DTT parameters at early stage. FAC score at chronic stage showed strong positive correlations with TVs of ipsilesional NST and ipsilesional CRT at early stage (ipsilesional NST R = 0.786; ipsilesional CRT R = 0.821; P < .05). According to regression model, FAC score at chronic stage was positively related to TVs of ipsilesional NST and ipsilesional CRT at early stage (Adjusted R2 = 0.700, F = 34.905, P < .05). FAC score at chronic stage was associated more positively with TV of ipsilesional CRT (β = 0.532) than that of ipsilesional NST (β = 0.362). Ipsilesional NST and ipsilesional CRT at early stage had prognosis predictability for gait function at chronic stage in patients with an MCA infarction. Moreover, ipsilesional CRT had stronger predictability than ipsilesional NST.

Changes in the Brain in Temporal Lobe Epilepsy with Unilateral Hippocampal Sclerosis: An Initial Case Series

Temporal lobe epilepsy (TLE) is a network disorder of the brain. Network disorders predominately involve dysregulation of hippocampal function caused by neuronal hyperexcitability. However, the relationship between the macro- and microscopic changes in specific brain regions is uncertain. In this study, the pattern of brain atrophy in patients with TLE and hippocampal sclerosis (HS) was investigated using volumetry, and microscopic changes in specific lesions were observed to examine the anatomical correspondence with specific target lesions using diffusion tensor imaging (DTI) with statistical parametric mapping (SPM). This retrospective cross-sectional study enrolled 17 patients with TLE and HS. We manually measured the volumes of the hippocampus (HC), amygdala (AMG), entorhinal cortex, fornix, and thalamus (TH) bilaterally. The mean diffusivity and fractional anisotropy of each patient were then quantified and analyzed by a voxel-based statistical correlation method using SPM8. In right TLE with HS, there was no evidence of any abnormal diffusion properties associated with the volume reduction in specific brain regions. In left TLE with HS, there were significant changes in the volumes of the AMG, HC, and TH. Despite the small sample size, these differences in conditions were considered meaningful. Chronic left TLE with HS might cause structural changes in the AMG, HC, and TH, unlike right TLE with HS.

Preservation of Cerebellar Afferent Pathway May Be Related to Good Hand Function in Patients with Stroke

Many chronic stroke patients suffer from worsened hand function, and functional recovery of the hand does not occur well after six months of stroke. Therefore, predicting final hand function after stroke through acute phase imaging would be an important issue in counseling with the patients or their family. Thus, we investigated the remaining white matter integrity in the corticospinal tract (CST) and cortico-ponto-cerebellar tract (CPCT) at the acute stage of stroke and chronic hand function after stroke, and present the cut-off value of fiber number (FN) and fractional anisotropy (FA) of CST and CPCT at the acute stage for predicting final hand function after the recovery period. This retrospective case-control study included 18 stroke patients who were classified into two groups: poor hand function with stroke (n = 11) and good hand function with stroke (n = 7). DTI was done within two months ± 15 days after onset, and the Jebson's Hand Function test was conducted 6-12 months after onset. The investigation of white matter was focused on the values of FN and FA for CST and CPCT, which were measured separately. The normalized (affected/non-affected) FA and FN values in the CPCT in the good hand function group were higher than those in the poor hand function group. The normalized FN and FA values in the CST were not significantly different between the poor hand function group and the good hand function group. The normalized cut-off value that distinguished the good hand function group from the poor hand function group was 0.8889 for FA in the CPCT. The integrity of the CPCT in the acute stage was associated with hand function in the chronic stage after a stroke. Ultimately, the integrity of the CPCT in the early stage after onset can be used to predict chronic hand function. Based on these results, cerebellar afferent fiber measurements may be a useful addition to predict hand function and plan specific rehabilitation strategies in stroke patients.

Mapping the human corticoreticular pathway with multimodal delineation of the gigantocellular reticular nucleus and high-resolution diffusion tractography

The corticoreticular pathway (CRP) is a major motor tract that transmits cortical input to the reticular formation motor nuclei and may be an important mediator of motor recovery after central nervous system damage. However, its cortical origins, trajectory and laterality are incompletely understood in humans. This study aimed to map the human CRP and generate an average CRP template in standard MRI space. Following recently established guidelines, we manually delineated the primary reticular formation motor nucleus (gigantocellular reticular nucleus [GRN]) using several group-mean MRI contrasts from the Human Connectome Project (HCP). CRP tractography was then performed with HCP diffusion-weighted MRI data (N = 1065) by selecting diffusion streamlines that reached both the cortex and GRN. Corticospinal tract (CST) tractography was also performed for comparison. Results suggest that the human CRP has widespread origins, which overlap with the CST across most of the motor cortex and include additional exclusive inputs from the medial and anterior prefrontal cortices. The estimated CRP projected through the anterior and posterior limbs of the internal capsule before partially decussating in the midbrain tegmentum and converging bilaterally on the pontomedullary reticular formation. Thus, the CRP trajectory appears to partially overlap the CST, while being more distributed and anteromedial to the CST in the cerebrum before moving posterior to the CST in the brainstem. These findings have important implications for neurophysiologic testing, cortical stimulation and movement recovery after brain lesions. We expect that our GRN and tract maps will also facilitate future CRP research.

Corticoreticular Pathway in Post-Stroke Spasticity: A Diffusion Tensor Imaging Study

One of the pathophysiologies of post-stroke spasticity (PSS) is the imbalance of the reticulospinal tract (RST) caused by injury to the corticoreticular pathway (CRP) after stroke. We investigated the relationship between injuries of the CRP and PSS using MR diffusion tensor imaging (DTI). The subjects were divided into spasticity and control groups. We measured the ipsilesional fractional anisotropy (iFA) and contralesional fractional anisotropy (cFA) values on the reticular formation (RF) of the CRP were on the DTI images. We carried out a retrospective analysis of 70 patients with ischemic stroke. The cFA values of CRP in the spasticity group were lower than those in the control group (p = 0.04). In the sub-ROI analysis of CRP, the iFA values of pontine RF were lower than the cFA values in both groups (p < 0.05). The cFA values of medullary RF in the spasticity group were lower than the iFA values within groups, and also lower than the cFA values in the control group (p < 0.05). This results showed the CRP injury and that imbalance of RST caused by CRP injury was associated with PSS. DTI analysis of CRP could provide imaging evidence for the pathophysiology of PSS.