A new automatic skull stripping method for fluid attenuated inversion recovery (FLAIR) MR images is proposed for the quantification of brain volume in multiple sclerosis (MS) patients. The proposed method is based on the use of local moment of inertia structure tensor and morphological operators. The local moment of inertia structure tensor is used to determine the boundary of the brain, instead of the conventional edge detection algorithms. Data from 30 MS patients were processed by the proposed method and the Brain Extraction Tool (BET); the results of which were also compared with manual segmentation. It was shown that the proposed method was able to produce more accurate results.