Lesion distribution pattern of parenchymal Neuro-Behçet's disease using probability mapping

Behçet's disease (BD) is an inflammatory disorder with multisystemic involvement. The most disabling aspect of BD is Neuro-Behçet's disease (NBD). In NBD, parenchymal lesions tend to occur in the mesodiencephalic region and brainstem, as reported in large series of NBD. Our study aimed to generate probability maps of parenchymal lesions to compare patient subgroups with different clinical and laboratory features.

We included 66 non-standardized acute relapse MRIs of 55 patients with parenchymal NBD (p-NBD). We used T2-weighted axial images to digitalize the lesions using the CAD software. Boundaries of lesions were determined as polygons and converted into high-definition raster datasets. Then, digitalized lesion maps were transferred into the ICBM-152 brain template to perform spatial analyses. Finally, we created subtraction maps to compare the patient subgroups.

We used a total of 66 MRIs of 55 patients to generate the probability maps. The most frequently affected parenchymal structures were the rostral pons, mesencephalon, and diencephalic region. Interestingly, the brainstem was more commonly affected in females than males (p<0.01). In the late-onset disease, lesions were localized in the corticospinal tracts and caudal brainstem (p<0.01). Progressive disease and severe disability at the end of the follow-up period were associated with corticospinal tract lesions during relapses (p<0.01). Patients with positive pathergy tests were more likely to present right hemisphere involvement (p<0.01). Additionally, cyclosporine-induced lesions tend to be in atypical locations such as hemispheric white matter.

In the published studies, lesions in NBD were localized according to coarse anatomical regions. Our study uses visual maps to offer accurate lesion localizations using non-standardized brain MRIs, allowing comparisons across different NBD subgroups. By using this technique, we investigated the relationship of the clinical and laboratory features with the lesion locations. We found that the late age of onset was associated with a poor prognosis. Additionally, corticospinal lesions may predict severe and progressive disease course, requiring aggressive treatment. Interestingly, females had more brainstem lesions and lesion lateralization might be influenced by the pathergy test status.