Objective To investigate the variation of multivoxel 1 H magnetic resonance spectroscopy(1 H-MRS)before and after continuous positive airway pressure(CPAP)treatment in obstructive sleep apnea hypopnea syndrome(OSAHS).Methods Brain multivoxel 1 H-MRS examinations were performed in 25 cases of moderate or severe OSAHS patients before and after CPAP treat-ment,and 25 cases of healthy.The ratios of brain metabolites of the frontal lobe were recorded and analyzed respectively.To observe whether the lactate(Lac)peak appeared or not.Results In the frontal lobe,the NAA/Cr,NAA/Cho of the patients before treatment (2.021 2±0.231 2 and 1.608 8±0.257 1,respectively)was decreased compared with the healthy (2.726 8±0.607 1 and 2.445 6± 0.437 5).The NAA/Cr,NAA/Cho of the patients after treatment (2.314 0±0.312 8 and 2.01 6 4±0.424 0,respectively)was in-creased compared with the patients before treatment (2.021 2±0.231 2 and 1.608 8±0.257 1).The NAA/Cr,NAA/Cho of the pa-tients after treatment (2.314 0±0.312 8 and 2.01 6 4±0.424 0,respectively)was decreased compared with the healthy (2.726 8± 0.607 1 and 2.445 6±0.437 5),and the difierences were statistically significant (P <0.01).The Cho/Cr of the patients before treatment (1.293 2±0.261 5)was increased compared with the healthy (1.129 2±0.157 7),the difference was statistically significant(P <0.05).Lac peak was not detected in all.Conclusion Multivoxel 1 H-MRS can demonstrate sensitively the changes of brain metabolism in pa-tients with OSAHS before and after CPAP treatment,and may provide imaging evidence for clinical therapeutic effect and prognostic evaluation.