Microstructural characterization of corticospinal tract in subacute and chronic stroke patients with distal lesions by means of advanced diffusion MRI.

PURPOSE: The aim of the paper is to evaluate if advanced dMRI techniques, including diffusion kurtosis imaging (DKI) and neurite orientation dispersion and density imaging (NODDI), could provide novel insights into the subtle microarchitectural modifications occurring in the corticospinal tract (CST) of stroke patients in subacute and chronic phases. METHODS: Seventeen subjects (age 68 ± 11 years) in the subacute phase (14 ± 3 days post-stroke), 10 of whom rescanned in the chronic phase (231 ± 36 days post-stroke), were enrolled. Images were acquired using a 3-T MRI scanner with a two-shell EPI protocol (20 gradient directions, b = 700 s/mm2, 3 b = 0; 64 gradient directions, b = 2000 s/mm2, 9 b = 0). DTI-, DKI-, and NODDI-derived parameters were calculated in the posterior limb of the internal capsule (PLIC) and in the cerebral peduncle (CP). RESULTS: In the subacute phase, a reduction of FA, AD, and KA values was correlated with an increase of ODI, RD, and AK parameters, in both the ipsilesional PLIC and CP, suggesting that increased fiber dispersion can be the main structural factor. In the chronic phase, a reduction of FA and an increase of ODI persisted in the ipsilesional areas. This was associated with reduced Fic and increased MD, with a concomitant reduction of MK and increase of RD, suggesting that fiber reduction, possibly due to nerve degeneration, could play an important role. CONCLUSIONS: This study shows that advanced dMRI approaches can help elucidate the underpinning architectural modifications occurring in the CST after stroke. Further follow-up studies on bigger cohorts are needed to evaluate if DKI- and NODDI-derived parameters might be proposed as complementary biomarkers of brain microstructural alterations.

A multicenter prospective study validated a nomogram to predict individual risk of dependence in ambulation after rehabilitation.

OBJECTIVES: To develop the Functional Risk Index for Dependence in Ambulation (FRIDA) score, a nomogram to predict individual risk of dependence in ambulation at discharge from postacute rehabilitation and validate its performance temporally and spatially. STUDY DESIGN AND SETTING: We analyzed the database of a multicenter prospective observational quality cohort study conducted from January 2012 to March 2016, including data from 8,796 consecutive inpatients who underwent rehabilitation after stroke, hip fracture, lower limb joint replacement, debility, and other neurologic, orthopedic, or miscellaneous conditions. RESULTS: A total of 3,026 patients (34.4%) were discharged dependent in ambulation. In the training set of 5,162 patients (58.7%), Lasso-regression selected advanced age, premorbid disability, and eight indicators of medical and functional adverse syndromes at baseline to establish the FRIDA score. At the temporal validation obtained on an external set of 3,234 patients (41.3%), meta-analyses showed that the FRIDA score had good and homogeneous discrimination (summary area under the curve 0.841, 95% confidence interval = 0.826-0.855, I2 = 0.00%) combined with accurate calibration (summary Log O/E ratio 0.017, 95% confidence interval -0.155 to 0.190). These performances remained stable at spatial validation obtained on 3,626 patients, with substantial heterogeneity of estimates across nine facilities. Decision curve analyses showed that a FRIDA score-supported strategy far outperformed the usual "treat all" approach in each impairment categories. CONCLUSION: The FRIDA score is a new clinically useful tool to predict an individual risk for dependence in ambulation at rehabilitation discharge in many different disabilities, and may also reflect well the case-mix composition of the rehabilitation facilities.