Axial and coronal MR images show correlation between DMN FC and severity of late anxiety symptoms. Anxiety symptom severity measured at 3-month follow-up, A, correlates positively with FC index to DMN in left middle temporal cortex and, B, correlates negatively with posterior cingulate cortex. Source: Radiology (doi:10.1148/radiol.12111718)

Impairments to the functional connectivity in the network of the brain involved in emotional regulation have been shown to have a strong association with the severity of post-stroke depression (PSD), according to research published online June 5 in Radiology.

Lead researcher Igor Sibon, MD, PhD, professor of neurology at the University of Bordeaux in Bordeaux, France, explained that one-third of surviving stroke patients experience PSD. “However, studies have failed to identify a link between lesions in the brain caused by ischemia during a stroke and subsequent depression,” he said in a release.

Sibon and colleagues set out to investigate the accuracy of using rest functional connectivity (FC) in specific areas to predict severity of post-stroke depression by acquiring functional MRI (fMRI) images of 24 stroke patients. The focus was on the group of brain structures that make up the default-mode network (DMN), a functional network. The DMN is associated with internally generated thought processes and modifications to DMN connectivity have been observed in depressive patients.

fMRI was conducted 10 days after patients had a mild to moderate ischemic stroke. Hamilton Depression Rating Scale (HDRS) 17 and Hamilton Anxiety Rating Scale (HARS) were recorded at 10 days and three months post-stroke. A diagnosis of post-stroke depression based on DSM-IV criteria was made at three months.

A total of 10 patients had minor to moderate depression based on DSM-IV criteria, while 14 patients had no depression. Results of the fMRI exams demonstrated an association between modifications of connectivity in the DMN 10 days post-stroke and the severity of depression at three months, however, post-stroke depressive symptom severity at 10 days was not correlated.

Anxiety severity was correlated with FC in the middle temporal cortex (MTC) and the anterior midcingulate cortex at 10 days, while correlations with the MTC and the posterior cingulate cortex were present at three months.

“MTC is involved in the perception of negative emotional facial expressions and affective empathy and is considered part of a network involved in the comprehension of others’ mental states. MTC FC alteration observed in the present work supports the impairment in theory of mind reported in patients with post-stroke depression,” wrote the authors.

Sibon added that the results “support the theory that functional brain impairment following a stroke may be more critical than structural lesions.”

The authors noted that the results of this study may contribute to the clinical management of stroke patients by allowing an investigation of treatments for patients with fMRI results immediately post-stroke that indicated impaired connectivity in the DMN, but further studies would be needed to determine the mechanisms of this functional impairment.