Peri-hematoma corticospinal tract integrity in intracerebral hemorrhage patients: A diffusion-tensor imaging study

Background: The impact of perihematoma edema in Intracerebral Hemorrhage (ICH) on white matter integrity is uncertain. Fractional Anisotropy (FA), as measured with Diffusion Tensor Imaging (DTI), can be used to assess white matter microstructure. We tested the hypotheses that sections of the Corticospinal Tract (CST) passing through perihematoma edema would 1) have low FA relative to the contralateral CST and 2) would predict NIHSS motor score in ICH patients. Methods: Patients were prospectively imaged with DTI at 48 h and 7 days after onset. Edema volume/extent was measured on CT at baseline and 24 h. FA, mean, axial and radial diffusivity were measured in the perihematoma edema, contralateral CST and sections of CST passing through the edema ('edematous CST'). Results: Patients (n = 27, mean age 67 +/- 13) were scanned with DTI at a median (IQR) of 42.3 (24.5) hours and 7.7 (1.8) days from onset. Median acute ICH volume was 8.8 (22) ml. FA in edematous CST at 72 h was decreased (0.37 +/- 0.03) relative to contralateral CST (0.52 +/- 0.06; p < 0.0001). Day 7 FA in edematous CST (0.35 +/- 0.08) was also decreased compared to contralateral CST (0.54 +/- 0.06; p < 0.0001). FA remained stable between 72 h (0.37 +/- 0.03) and day 7 (0.35 +/- 0.07; p = 0.350). FA at 72 h (rho =-0.22, p = 0.420) and day 7 (rho =-0.14, p = 0.624) was unrelated to 90-day motor score. Conclusions: FA is decreased in the CST where it passes through the edema. Decreased FA in the edematous CST remained stable over time, was unrelated to motor score, and may represent water infiltration into the tracts rather than axonal injury.