Brain structural investigation and hippocampal tractography in medication overuse headache: a native space analysis
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Behavioral and Brain Functions Open Access
RESEARCH
Brain structural investigation and hippocampal tractography in medication overuse headache: a native space analysis M. Meyer1,2* , G. Di Scala1, M. Edde1, B. Dilharreguy1, F. Radat3, M. Allard1,2,4 and S. Chanraud1,4
Abstract Background: Spatial normalization of brain images, a prerequisite for voxel based morphometry analysis, may account for the large variability of the volumetric data in medication overuse headache (MOH); possibly because this disease concerns patients differing on both sex and age, and hence with different brain size and shape. Methods: The present study aimed at providing a subject-based analysis of macrostructure using a native space volumes segmentation (Freesurfer), and microstructure using a region of interest (ROI: i.e. hippocampus) tractography approach in MOH patients. Results: The results show that MOH patients had decreased volumes of left hemisphere temporal gyri (temporal superior, fusiform) and occipital middle gyrus, together with an increased volume of the left inferior (temporal) lateral ventricle. The left temporal volume was negatively correlated with depression score and medication dependence parameters. Seed-based tractography of the hippocampus revealed a decreased number of reconstructed fibers passing through the left hippocampus. Conclusion: To our knowledge, these alterations have not been described with methods involving brain normalization, and they indicate that left hemisphere temporal areas, including the hippocampus, may play a role in MOH pathophysiology. Trial registration number NCT00833209. Registered 29 January 2009 Keywords: Migraine, Pain, Macrostructure, Freesurfer, Hippocampus, Asymmetry Background Medication overuse headache (MOH) is a form of chronic headache [1] resulting from overuse of headache medications (simple analgesics, opioids and derivates, triptans). Neuroimaging techniques have provided important insight into the brain mechanisms supporting or, related to MOH; but discordance among published studies questions the significance and clinical relevance of these data. As a matter of fact, alterations of volumetric grey [2] and white matter [3] were described, but these findings have been challenged by other studies failing to find any *Correspondence: marie.meyer@chu‑bordeaux.fr 2 Nuclear Medicine Department, Pellegrin Hospital, CHU Pellegrin, CHU of Bordeaux, Place Amélie Raba‑Léon, 33000 Bordeaux Cedex, France Full list of author information is available at the end of the article
structural alteration [4, 5]. The reasons for these discrepancies are still unknown, and can hardly be attributed to the methods used, as they were quite similar. In particular, most studies were based on whole brain exploration, such as voxel-based morphometry, a fully automated, hypothesis-free method, which provides a voxel-wise assessment of regional cerebral matter. Despite this intrinsic quality, these methods necessitate a normalization step. Spatial normalization is the conventional method for warp
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