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Neural Plasticity
Volume 2013, Article ID 832473, 10 pages
http://dx.doi.org/10.1155/2013/832473
Clinical Study

Ipsilateral and Contralateral Auditory Brainstem Response Reorganization in Hemispherectomized Patients

1Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, China
2Department of Neuroelectrophysiology, Beijing Neurosurgical Institute, Beijing 100050, China
3Department of Neurosurgery, Xuzhou Medical College Affiliated Hospital, Xuzhou Medical College, Jiangsu 221000, China
4Medical Experiments and Testing Center, Capital Medical University, Beijing 100069, China
5Department of Neurosurgery, Beijing Jishuitan Hospital, Beijing 100035, China
6Department of Neurosurgery, The First Teaching Hospital of Xinjiang Medical University, Xinjiang Medical University, Xinjiang 830000, China

Received 7 August 2013; Revised 6 November 2013; Accepted 20 November 2013

Academic Editor: Robert Adamec

Copyright © 2013 Ning Yao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background. Cortical hemispherectomy leads to degeneration of ipsilateral subcortical structures, which can be observed long term after the operation. Therefore, reorganization of the brainstem auditory pathway might occur. The aim of this study was to assess reorganization of brainstem auditory pathways by measuring the auditory brainstem response (ABR) in long-term hemispherectomized patients. Methods. We performed bilateral monaural stimulation and measured bilateral ABR in 8 patients ~20 years after hemispherectomy and 10 control subjects. Magnetic resonance imaging (MRI) was performed in patients to assess structural degeneration. Results. All patients showed degenerated ipsilateral brainstem structures by MRI but no significant differences in bilateral recording ABR wave latencies. However, nonsurgical-side stimulation elicited significantly longer wave V latencies compared to surgical-side stimulation. Differences in bilateral ABR were observed between hemispherectomized patients and control subjects. Waves III and V latencies elicited by nonsurgical-side stimulation were significantly longer than those in control subjects; surgical-side stimulation showed no significant differences. Conclusions. (1) Differences in ABR latency elicited by unilateral stimulation are predominantly due to bilateral brainstem auditory pathway activity rather than to changes in brainstem volume; (2) ABR Waves III and V originate predominantly in the contralateral brainstem; and (3) subcortical auditory pathways appear to reorganize after long term hemispherectomy.