Differentiating  brain abscesses from cystic or necrotic neoplasm is difficult.  Recent research has demonstrated that the accuracy of ADC(apparent diffusion coefficient) ratios in discriminating  brain abscesses from cystic or necrotic neoplasm is improved with the use of diffusion-weighted MRI.  Diffusion-weighted MRI has been found effective in discriminating and evaluating cerebral ischemia.    Fertikth, et. al reports on a study in which 53 patients with rim-enhancing brain masses were evaluated with T1-weighted MR images.  The accuracy of diagnosis was improved significantly with diffusion-weighted MRI.  The studies were performed with a GE 1.5-tesla MR unite in which  a 2D echo planar imaging sequence was used. 

Researchers found statistically significant differences in ADC ratios across lesion sub-groups.  Accuracy of diagnosis was 87% for determining abscess vs. neoplasms and 100% specificity for discriminating neoplasms from nonneoplastic lesions. 

Brain abscess evolution is described in stages:  early cerebritis, late cerebritis, early capsule formation and late capsular formation.  The capsular stage usually starts at 2 weeks and can last weeks to months.  On MRI, during this stage, the lesion shows as a ring-enhancing lesion with edema.   Conventional MR is not always diagnostic in differentiating brain abscesses in the capsular stage from necrotic or neoplastic lesions.  Bacterial lesions are the most easily distinguished from neoplastic lesions using diffusion –weighted imaging.

Evaluating Weakness with Diffusion Tensor Imaging 

Diffusion tensor imaging is used to identify white matter tracts.  Kim, et. al. reported on a study, which looked at using diffusion tensor imaging in relation to functional analysis.  They found that motor weakness was related to low mean FA (fractional anisotrophies) in the pyramidal tract on the side with a lesion. MRI has been used to show anatomical relationships prior to tumor resection.  Currently, functional MR is used to localize brain functions in gray matter .  Researchers are finding that obtaining white matter information is helpful prior to surgical planning.  Integrating both anatomical and functional images for presurgical planning is helpful. Patients seeking this type of information can contact the neurologists for further information.  

For more information, contact the surgeons at the Neuroscience Group of NE Wisconsin.
summon.bhattacharjee@neurosciencegroup.com
randall.johnson@neurosciencegroup.com
philip.yazbak@neurosciencegroup.com