Altered cortical and subcortical local coherence in obstructive sleep apnea: a functional magnetic resonance imaging study

Abstract

SUMMARYObstructive sleep apnea (OSA) syndrome is the most common sleeprelated breathing disorder, characterized by excessive snoring and repetitive apneas and arousals, which leads to fragmented sleep and, most importantly, to intermittent nocturnal hypoxaemia during apneas. Considering previous studies about morphovolumetric alterations in sleep apnea, in this study we aimed to investigate for the first time the functional connectivity profile of OSA patients and age-gender-matched healthy controls, using resting-state functional magnetic resonance imaging (fMRI). Twenty severe OSA patients (mean age 43.2 ± 8 years; mean apnea-hypopnea index, 36.3 h À1 ) and 20 non-apneic age-gender-body mass index (BMI)-matched controls underwent fMRI and polysomnographic (PSG) registration, as well as mood and sleepiness evaluation. Cerebro-cerebellar regional homogeneity (ReHo) values were calculated from fMRI acquisition, in order to identify pathology-related alterations in the local coherence of low-frequency signal (<0.1 Hz). Multivariate pattern classification was also performed using ReHo values as features. We found a significant pattern of cortical and subcortical abnormal local connectivity in OSA patients, suggesting an overall rearrangement of hemispheric connectivity balance, with a decrease of local coherence observed in right temporal, parietal and frontal lobe regions. Moreover, an increase in bilateral thalamic and somatosensory/motor cortices coherence have been found, a finding due possibly to an aberrant adaptation to incomplete sleep-wake transitions during nocturnal apneic episodes, induced by repetitive choke sensation and physical efforts attempting to restore breathing. Different hemispheric roles into sleep processes and a possible thalamus key role in OSA neurophysiopathology are intriguing issues that future studies should attempt to clarify. IN TROD UCTI ONObstructive sleep apnea syndrome (OSA) is a very common sleep disorder, the neuropathophysiology of which remains controversial (Horner, 2008) . It is characterized by excessive snoring and repetitive nocturnal apneas and arousals, which leads to fragmented sleep and, most importantly, intermittent nocturnal hypoxaemia during apneas. These result in a complex and disabling condition composed by daytime sleepiness, neurocognitive problems such as deficits in memory, attention and visuoconstructive abilities (Bruin and Bagnato, 2010), reduced work performance and a worsening of overall quality of life (Bulcun et al., 2012). During the last 15 years several brain alterations have also been documented. The majority of studies, performed through voxel-based morphometry (VBM) or surface-based parcellation approaches, have highlighted grey matter concentration differences in both cortical and subcortical brain regions, with hippocampus,

Disrupted functional brain network organization in patients with obstructive sleep apnea

“…Previous studies on brain resting‐state FC in OSA subjects found local FC alterations in the middle and dorsal prefrontal cortex, left precentral gyrus, and PCC, decreased local FC in the frontal, temporal, and parietal, and increased FC in the sensorimotor, thalamic, and cerebellum regions (Santarnecchi et al. ; Zhang et al. ; Peng et al.…”

“…), and compromised resting‐state regional activity using regional homogeneity (Santarnecchi et al. ; Peng et al. ).…”

Structural and functional neural adaptations in obstructive sleep apnea: An activation likelihood estimation meta-analysis

“…Fifteen publications that recruited 290 OSA patients and 290 healthy controls were included (Ayalon et al, 2009a, Ayalon et al, 2006, Fatouleh et al, 2014, Harper et al, 2003, Henderson et al, 2003, Joo et al, 2010, Li et al, 2015, Macey et al, 2006, Macey et al, 2003, Morrell et al, 2010, Prilipko et al, 2011, Santarnecchi et al, 2013, Torelli et al, 2011, Yaouhi et al, 2009, Zhang et al, 2013) (Table 1, Fig. 1).…”

Functional disconnection of the right anterior insula in obstructive sleep apnea

“…Recent rs-fMRI studies also demonstrate functional disconnection in brain areas of the CEN and DMN in OSA patients [6,51]. These findings suggest that the functional impairment of the CEN and DMN may contribute to cognitive deficits in these patients.…”