Brain Diffusion Changes in Obstructive Sleep Apnoea Syndrome

Abstract

Background: Obstructive sleep apnoea syndrome (OSAS) is a disorder characterized by repeated apnoeic episodes during sleep. Neurocognitive changes secondary to OSAS are likely to occur due to hypoxia in certain brain locations. Advances in magnetic resonance imaging technology, such as diffusion-weighted imaging (DWI), enable non-invasive and accurate identification of OSAS-induced changes. Objective: We aimed to use DWI to investigate changes in the brain secondary to hypoxia in OSAS. Methods: Eighty-eight patients underwent polysomnography and were classified as non-OSAS, mild-moderate OSAS and severe OSAS sufferers. DWI was used to evaluate 14 areas of the brain, and apparent diffusion coefficients (ADCs) were calculated. We investigated whether there were differences in the ADC values in specific areas of the brain between the non-OSAS and OSAS patients. Results: We measured the ADC values of the 68 newly diagnosed OSAS patients (21 mild, 15 moderate and 32 severe) and of 20 healthy controls. There were significant increases in the ADC values in the hippocampus, amygdala and putamen in OSAS patients. Compared to the non-OSAS subjects, the ADC values of the putamen in severe OSAS patients, those of the hippocampus in moderate or severe OSAS patients and those of the amygdala in moderate OSAS patients were significantly increased. A negative correlation between the lowest oxygen saturation during sleep and the ADC values of the hippocampus and amygdala was found. Conclusions: Increased ADC levels in the hippocampus, amygdala and putamen in OSAS patients indicate hypoxia and likely cause vasogenic oedema in specific regions of the brain.

Vasogenic cerebral edema associated with the disability in activities of daily living in patients with chronic obstructive pulmonary disease

“…Consistent with previous findings in patients with COPD, widespread increases in ADC values have also been observed in patients with stroke (Schlaug et al., 1997; Yang & Rosenberg, 2011) and in patients with obstructive sleep apnea syndrome (Emin Akkoyunlu et al., 2013). In a previous study, a decrease in FA values in patients with COPD was observed (Zhang et al., 2012b).…”

Accelerated Echo Planer J-resolved Spectroscopic Imaging of Putamen and Thalamus in Obstructive Sleep Apnea

“…A number of processes, possibly including intermittent cerebral ischemia, marked blood pressure swings, and CO 2 changes accompanying repeated apnea episodes during sleep in OSAS patients cause structural injury and dysfunction367. Although atrophy and neuronal loss in the thalamus and putamen of OSAS patients have been reported earlier15161718, the underlying pathophysiology underlying the injury is complex, with the putamen also showing regions of volume increase suggestive of inflammation or glial activation, as opposed to cell death or reduced myelin integrity. We found significantly lower tCho/Cr ratios in the bilateral thalamus and right putamen, tNAA/Cr and NAA/Cr in left thalamus, GABA/Cr in bilateral putamen, PE/Cr in left putamen and GPC/Cr in the right thalamus in the OSAS patients, as compared to healthy controls.…”

“…Both structural and functional neuroimaging studies show brain injury in the putamen91516, and thalamus in OSAS patients1718, but information on metabolite levels in damaged areas is sparse1920. Magnetic resonance spectroscopy (MRS) is a noninvasive neuroimaging tool that allows assessment of cerebral metabolite changes, providing information on neuronal cellular viability, cellular energetics, and cellular membrane status20, and may assist understanding of the nature of the altered thalamic and putamen structures in OSAS.…”

Assessment of neural alterations in obstructive sleep apnoea syndrome: can apparent diffusion coefficient measurements be useful?

“…Routine magnetic resonance imaging (MRI) examinations may not show cerebral damage in OSAS patients, but advanced MRI techniques can reveal neurochemical and structural changes in various regions of the brain (4,5). In the literature, many studies using non-invasive and quantitative methods such as diffusion-weighted imaging (DWI), MR spectroscopy (MRS) and T2 relaxometry have been used to identify alterations in the brains of OSAS patients (3)(4)(5)(6)(7)(8). DWI is a non-invasive technique, which can demonstrate cerebral damage resulting from some disease processes (9)(10)(11).…”

“…The diffusion of water molecules is affected by microenvironmental architecture, and the rate of diffusion, referred to as the apparent diffusion coefficient (ADC), can be measured quantitatively (12). Although DWI and ADC measurement are commonly used for differentiating a variety of brain lesions, to our knowledge, there are only two studies evaluating the efficacy of these methods in defining the structural changes in OSAS (6,8).…”