Is the Brain's Microstructure Important in AN?

One study examined the role of the subcalloseal cingulate cortex. 

Reprinted from Eating Disorders Review
November/December Volume 26, Number 6
©2015 IAEDP

Increasingly researchers are exploring the brain to find clues to the development of anorexia nervosa (AN). Within the brain the subcallosal cingulate cortex (SCC) regulates affect, and thus may play a role in the pathophysiology of AN. 

Recently developed magnetic resonance imaging techniques such as diffusion tensor imaging allow researchers to assess whether white matter connections are intact or disrupted. A group of neuroscientists and psychologists at the University of Toronto recently used diffusion magnetic resonance imaging (dMRI) and multi-tensor tractography to compare the anatomic connections and microcircuits among 8 women with treatment-resistant AN and 8 sex- and age-marched healthy controls. The women with AN were also clinically assessed before and after deep brain stimulation (Brain Stimulation. 2015; 8:758). All subjects underwent implantation of bilateral electrodes in the SCC followed by MRI.

Different patterns in healthy subjects and patients

As the authors reported, subcalloseal connectivity was different between AN patients and controls. The most marked differences were increased connectivity to the ipsilateral parietal cortex and decreased connectivity to the thalamus bilaterally in the AN patients. The scans also showed many equally connected regions in both groups of subjects. 

The main relationships between clinical affective measures and dMRI were seen in the left fornix crus, inferior frontal occipital fascius (IFO), and right internal capsule, or the anterior limb of the internal capsule, or ALIC, among the AN patients. The abnormalities were consistent with a central role for dysfunctional affective processing and broad clinical changes, particularly changes in processing of affective stimuli, self-perception, and interoception, according to Dr. Dave J. Hayes and colleagues.

The findings should be viewed as preliminary and the sample was small — but among those with AN differences in connectivity and intact circuits were seen. Furthermore, dMRI metrics predicted a deep brain stimulation response. The authors are correct in noting that such preliminary findings may point the way toward the development of sophisticated predictors of treatment response.