Corticospinal Tract Displacement: A Novel Imaging Marker for Arm Recovery in Patients with Acute Hypertensive Intracerebral Hemorrhage.

Background and purpose: Brain parenchymal mass effect after acute intracerebral hemorrhage (ICH) causes neurologic deficits by displacing and or damaging the corticospinal tract (CST). The impact of corticospinal tract displacement (CSTD) on arm recovery and the influence of hematoma reversal on recovery are not well understood. We conducted a serial MRI study to explore these relationships.

Materials and methods: Eighteen patients with spontaneous subcortical ICH were scanned on days 2 (baseline) and 90 (90 days) of onset. We used 3D-anatomic and 2D-DTI MRI, segmenting hematoma volume (HV), perihematomal edema (PHE), and the posterior limbs of the internal capsule (PLIC) volume labeled as native space. Presegmented PLIC volumes labeled as standard PLIC were obtained by using DTI-atlas. All segmented volumes were registered on a standard T1-weighted image followed by inverse-matrix transformation. Centroid-coordinates in native and standard PLIC were determined and a change in Euclidean distance was used to assess CSTD. Additionally, we measured changes in corticospinal tract volume due to lesion load (LLCSTV). ICH severity and upper extremity impairment were assessed by using NIHSS and Fugl-Meyer Upper Extremity (FM-UE) scores. A generalized linear mixed-model was applied to analyze CSTD and volume changes. A Bayesian inference was used to determine the posterior probability (PP). The CSTD, LLCSTV, and HV were correlated with NIHSS and FM-UE scores.

Results: We enrolled 11 men and 7 women, with a mean age of 54.8 (standard deviation = 11.8). Analyses found strong support for temporal change in hematoma volume (14.8 ± 23.7 to 4.46 ± 4.99 mL) 75.5% decrease in log HV (b = -1.41, PP > 99.9%), a 64.3% decrease in NIHSS (b = -7.95, PP > 99.9%), and a 111.8% increase (25.9 ± 22.0 to 41.0 ± 22.1 mL) in FM-UE (b = 20.2, PP = 99.8%). The average ipsilesional (absolute = 10.1 ± 4.5 to 5.78 ± 2.26 mm) log CSTD decreased by 44.9% (b = -0.59, PP = 99.9%). The LLCSTV (27.8 ± 3.8 to 31.4 ± 2.8 mL) increased by 12.9% (b = 3.69, PP > 99.9%). Both ipsilesional log CSTD (b = -0.011, PP > 99.2%) and CST volume (b = 0.06, PP >99.8%), were strongly associated with arm recovery (FM-UE) substantiated by a strong association with stroke severity (NIHSS).

Conclusions: We present a quantitative surrogate imaging marker of CSTD and its association with arm recovery after ICH.