Reduced cerebral blood flow during wakefulness in obstructive sleep apnea-hypopnea syndrome

Abstract

Study objectives: To investigate changes in regional cerebral blood flow (rCBF) in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS).

Design: We compared the 99mTc-ethylcysteinate dimer (ECD) single photon emission computed tomography (SPECT) images of patients with OSAHS with those of age- and sex-matched healthy volunteers.

Setting: University hospital.

Patients and participants: Twenty-seven patients with severe OSAHS and 27 healthy volunteers underwent 99mTc-ECD brain SPECT studies.

Intervention: For statistical parametric mapping analysis, all SPECT images were spatially normalized to the standard SPECT template and then smoothed using a 14-mm full-width at half-maximum Gaussian kernel. The Student t test was used for the statistical analysis.

Measurements and results: The mean age of patients and subjects was 44.3 years (range 31-58). All patients underwent overnight polysomnography. The mean apnea-hypopnea index of patients was 60.4 +/- 17.6 per hour (range 33 -104), indicating severe OSAHS. All patients snored heavily and had daytime sleepiness (mean Epworth Sleepiness Scale score, 10.7 +/- 3.7, range 6-12). Statistical parametric mapping analysis showed that rCBF in patients with OSAHS was significantly reduced in bilateral parahippocampal gyri and in the right lingual gyrus, as compared with that of healthy volunteers (P < 0.05 with false discovery rate correction). Moreover, apnea-hypopnea indexes of patients were negatively correlated with rCBF in the right pericentral gyrus and right cuneus at uncorrected P < 0.001.

Conclusions: Our results show the altered rCBF pattern in bilateral parahippocampal gyri, right lingual gyrus, pericentral gyrus, and cuneus in patients with severe OSAHS. These findings may partly explain the deficit in memory, spatial learning, executive function, and attention, which are frequently found in patients with OSAHS.

Figures

Figure 1

Results of statistical parametric mapping (SPM) analysis. (A) A statistical brain map showing a decrease in regional cerebral blood flow (rCBF) during wakefulness in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). rCBF was reduced in bilateral parahippocampal gyri (upper row) and left lingual gyrus (lower row) in patients with OSAHS compared with normal volunteers (at the false discovery rate corrected P < 0.05, independent t test) in coronal T1 magnetic resonance imaging overlaid view. (B) A statistical map generated by statistical parametric mapping (SPM)2 correlation analysis. Correlation analysis between rCBF and apnea-hypopnea indexes (AHI) shows that rCBFs in right pericentral gyrus (upper row) and right cuneus (lower row) were negatively correlated with AHI at the level of uncorrected P < 0.001. This finding means that if AHI is higher, rCBFs over those regions are more decreased. The results are superimposed on the 2-dimensional planes of a single subject magnetic resonance imaging (MRI) template of the SPM2. Left-hand sides of images represent the left hemisphere of brain.