Introduction: White matter hyperintensities (WMHs) are attributed mainly to degenerative small-vessel disease,3 and it might show dynamic changes over time.1 Additionally, previously we first reported improved WMHs following extracranial (EC)-intracranial (IC) bonnet bypass.2 Fluid-attenuated inversion recovery (FLAIR) T2-MRI is considered as a marker for ischemic lesions, thus, WMHs are frequently observed on it.3 Herein, a retrospective study was performed to investigate WMHs-course in patients who underwent EC-IC bypass in correlation to the clinical outcome.
Methods: Perioperative FLAIR-MRIs of 12 patients with WMHs, who underwent successful EC-IC bypass surgeries, were enrolled in this study. Correlation between WMHs and cerebral blood flow was confirmed by perioperative 123I-iodoamphetamine single photon emission computed tomography (SPECT) and diffusion-weighted image MRI. Sufficient brain revascularizations were confirmed by postoperative SPECT. Following determining the regions of interest on a slice-by-slice basis, meticulous volumetric grading and visual assessment of WMHs were done by three experienced raters independently. One of them was blinded to the clinical data. WMHs-course was determined to be improved, fluctuating, worsened or unchanged. Statistical analysis was done.
In order to avoid subjective errors, volumetric thresholds for each grade were determined, hyperintensities or changes below 0.25 mL were excluded, scaling evaluation table was designed and the MRI protocol was defined.
Results: WMHs-course over time were: improved (41.7%), fluctuated (33.3%), unchanged (16.7%) or worsened (8.3%). Bilaterally improved-WMH was seen in 80% of patients. Good clinical outcome was not always accompanied with improved WMHs.
Conclusions: Improvement of WMHs might occur following sufficient brain revascularization. However, improved-WMH is not an indispensable prerequisite for good clinical outcome. Also, we are aware that the retrospective nature and the relatively small number of cases are limitations of our study. Further prospective studies are required to validate our results and make more solid conclusions.
Patient Care: Alarm for brain revascularaization efficiency. Expectation of the patient's clinical outcome.
Learning Objectives: Improvement of ischemic WMHs could be considered a marker for sufficient brain revascularization.
References: 1. Cho A, Kim H, Kim W, Yang D. White Matter Hyperintensity in Ischemic Stroke Patients: It May Regress Over Time. J Stroke. 2015; 17(1):60-66.
2. Nagm A, Horiuchi T, Hasegawa T, Hongo K. Intraoperative evaluation of reverse bypass using a naturally formed "bonnet" superficial temporal artery: Technical note. World Neurosurg. 2015; DOI: 10.1016/j.wneu.2015.10.087. [Epub ahead of print]
3. Ostwaldt A, Galinovic I, Hotter B, Grittner U, Nolte C, Audebert H, Villringer K, Fiebach J. Relative FLAIR signal intensities over time in acute ischemic stroke: comparison of two methods. J Neuroimaging. 2015; 00:1-5.