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Postoperative Increase in Cerebral White Matter Fractional Anisotropy on Diffusion Tensor Magnetic Resonance Imaging Is Associated With Cognitive Improvement After Uncomplicated Carotid Endarterectomy: Tract-based Spatial Statistics Analysis

Sato, Yuiko MD*; Ito, Kenji PhD; Ogasawara, Kuniaki MD*; Sasaki, Makoto MD; Kudo, Kohsuke MD; Murakami, Toshiyuki MD*; Nanba, Takamasa MD*; Nishimoto, Hideaki MD*; Yoshida, Kenji MD*; Kobayashi, Masakazu MD*; Kubo, Yoshitaka MD*; Mase, Tomohiko MD§; Ogawa, Akira MD*

doi: 10.1227/NEU.0000000000000013
Research-Human-Clinical Studies

BACKGROUND: Carotid endarterectomy (CEA) might improve cognitive function. Fractional anisotropy (FA) values in the cerebral white matter derived from diffusion tensor magnetic resonance imaging (DTI) correlate with cognitive function in patients with various central nervous system diseases.

OBJECTIVE: To use tract-based spatial statistics to determine whether postoperative changes of FA values in the cerebral white matter derived from DTI are associated with cognitive improvement after uncomplicated CEA.

METHODS: In 80 patients undergoing CEA for ipsilateral internal carotid artery stenosis (≥70%), FA values in the cerebral white matter were derived from DTI before and 1 month after surgery and were analyzed by using tract-based spatial statistics. Neuropsychological testing, consisting of the Wechsler Adult Intelligence Scale Revised, the Wechsler Memory Scale and the Rey-Osterreith Complex Figure test, was also performed preoperatively and after the first postoperative month.

RESULTS: Based on the neuropsychological assessments, 11 (14%) patients were defined as having postoperatively improved cognition. The difference between the 2 mean FA values (postoperative values minus preoperative values) in the cerebral hemisphere ipsilateral to surgery was significantly associated with postoperative cognitive improvement (95% confidence intervals, 2.632-9.877; P = .008). White matter FA values in patients with postoperative cognitive improvement were significantly increased after surgery in the whole ipsilateral cerebral hemisphere, in the contralateral anterior cerebral artery territory, and in the watershed zone between the contralateral anterior and middle cerebral arteries.

CONCLUSION: Postoperative increase in cerebral white matter FA on DTI is associated with cognitive improvement after uncomplicated CEA.

ABBREVIATIONS: CEA, carotid endarterectomy

DTI, diffusion tensor magnetic resonance imaging

FA, fractional anisotropy

FLAIR, fluid-attenuated inversion recovery

ICA, internal carotid artery

IQ, intelligence quotient

ROI, region-of-interest

SD, standard deviation

TBSS, tract-based spatial statistics

WAIS-R, Wechsler Adult Intelligence Scale Revised

*Department of Neurosurgery, Iwate Medical University School of Medicine, Morioka, Japan;

Division of Ultra-High Field MRI and Department of Radiology, Iwate Medical University School of Medicine, Morioka, Japan;

§Department of Disaster Medicine, Iwate Medical University School of Medicine, Morioka, Japan

Correspondence: Kuniaki Ogasawara, MD, Department of Neurosurgery, Iwate Medical University, 19-1 Uchimaru, Morioka, Japan 020-8505. E-mail: kuogasa@iwate-med.ac.jp

Received January 15, 2013

Accepted May 30, 2013

Copyright © by the Congress of Neurological Surgeons