To identify brain regions and networks underlying acquired-brain-injury-induced chronic insomnia.

In patients of tertiary-level mental healthcare facilities, symptoms of chronic insomnia are prevalent in 78.2% of the population. Additionally, among those who suffer from acquired brain injury, few symptoms are as generally pervasive as that of chronic insomnia. Meta-analyses of insomnia patients with fMRI data have failed to identify consistently affected brain regions. Individual studies have suggested several brain regions are involved in insomnia, including the anterior cingulum, orbitofrontal cortex, the insula, caudate nucleus, and the anterior capsula interna. However, few regions have consistently been implicated in the pathophysiology of insomnia. Moreover, little is known regarding the collective brain networks involving insomnia. 

We performed a systematic literature review for case studies of patients presenting with acquired-brain-injury-induced insomnia (N=57). Lesion network mapping analysis (Fox, 2018) was performed, using lesion tracings from the 57 patients as seed regions to extract functional lesion network data from a large cohort of healthy control resting-state fMRI scans (N=1000).  

Upon completion of lesion network mapping analysis, 42/57 patients with acquired brain injury induced insomnia had brain lesions functionally connected to the left amygdala and left anterior insula. 39/57 patient lesion networks also included the bilateral anterior insula as well as the hypothalamus. In comparing analyzed lesions to a normative database of stroke lesions, acquired-brain-injury-induced insomnia patients lesion networks show a significant difference in functional connectivity to the middle cingulate gyrus, anterior cingulate gyrus, ventrolateral orbitofrontal cortex, and head of the caudate nucleus.

Our data establish previously implicated neuroanatomical structures in insomnia symptoms, including the middle cingulate gyrus, anterior cingulate gyrus, orbitofrontal cortex, and caudate nucleus, demonstrated in an interconnected sleep-initiation/maintenance network. Further work may consider exploring therapeutic utility through deep brain stimulation of identified neuroanatomical structures.