~1H Magnetic Resonance Spectroscopy Study Of Auditory Cortex Metabolism In Obstructive Sleep Apnoea Syndrome

Objective: Obstructive sleep apnea-hypopnea syndrome（OSAHS）andsensorineural hearing loss are the common diseases of E.N.T. department,Recent study show that: The patients with OSAHS have a higher incidencerate in sensorineural hearing loss. The mechanism is unclear. Through clinicaltesting for hearing, you can make evaluation of their hearing status, there is alack of accurate and reliable early warning indicators. Recently, studies showthat the cerebral metabolism in patients with OSAHS have abnormal changes,so we want to investigate the characteristic changes of the metabolismproducts in auditory cortex (transverse temporal gyrus) in OSAHS combinedwith nerve deafness. Now early metabolic changes in the auditory cortex iscurrently no effective means of detection, proton magnetic resonacespectroscopy (MRS) is used in the medical profession from1973. In vivoMRS can noninvasively measure metabolite concentrations of the tissue, andits detection is highly sensitivity. It determines the levels of specific chemicalsubstances through the different frequency peaks of coordinate，then providingreference information for the clinical determination including brain tumorsand other neurological diseases. Now nuclei31P,1H,23NA,13C,19F are used inthe medical field, because hydrogen has a high natural abundance proton andMagnetic induction than the other atomic nucleus, it is used in protonmagnetic resonance spectroscopy study usually than other atomic nucleus.1H-proton magnetic resonace spectroscopy (1H-MRS) can be used to detect avariety of trace metabolites in the body, such as N-acetyl aspartate (NAA),choline (Cho), creatine (Cr), lactate (Lac) and lipids (Lip), myo-inositol (mI),glutamate (Glu) and glutamine (Gln), etc. so we want to investigate thecharacteristic changes of the metabolism products in auditory cortex(transverse temporal gyrus) in OSAHS combined with nerve deafness using 1H magnetic resonance spectroscopy (1H-MRS), and to discovery the earlywarning indicator of nerve deafness in OSAHS.Methods: dBHL and ABR was performed in112patients withOSAHS(diagnosed by PSG), and15healthy control subjects, the patientswere classified into seven groups: the group of OSAHS (mild to moderate),the group of OSAHS (severe), the groups of OSAHS（mild to moderate andsevere）with unilateral and bilateral deafness and the normal control group.Cerebral metabolism was studied by assessing the ratios of nitro-acetylaspartate contrast to choline (NAA／Cho) as well as to creatine (NAA／Cr),myo-inositol to creatine（mI／Cr）and choline to creatine (Cho／Cr) ratios inthe auditory cortical separately in these groups. Determine the correlationbetween the metabolism products ratio and the AHI index. ROC curves weremade for those metabolism markers to find the best diagnositic threshold.Results：1The incidence of hearing loss in OSAHS patients was significantly higherthan in normal healthy people, when increasing in AHI index it shows anincreasing trendSensorineural deafness incidence of the OSAHS group is47.4%bydBHL and it is higher than the normal population.2The correlation between the metabolism products ratio and the AHI indexmake linear correlation analysis between the metabolism products ratiowith the AHI index,we find that there is a negative correlation between AHIand NAA／Cho, NAA／Cr. A positive correlation between AHI and Cho／Cr.3Compare the nerve metabolites between the OSAHS (mild to moderate)group, OSAHS (severe) group and the control group in right and left earsNAA／Cho and NAA／Cr are in a descending order between the control,OSAHS (mild to moderate) group and the OSAHS (severe) group, thedifference was statistically significant(P<0.05). mI／Cr and Cho／Cr are in aincreasing order, but there is no statistically significant difference between theOSAHS (mild to moderate) group and the OSAHS (severe) group (P>0.05). 4Compare the nerve metabolites between the control group, the OSAHSgroup, the OSAHS(mild to moderate)group with deafness and the OSAHS（severe）group with deafness.NAA／Cho and NAA／Cr are in a descending order in these four groups.Cho／Cr and mI／Cr are in a increasing order in these five groups.NAA／Cho has a statistically significant difference between the four groups.5Compare the normal of auditory cortex and injured of auditory cortex ofthe nerve metabolites in unilateral ear of deafnessrNAA／Cho and NAA／Cr of the injured of auditory cortex of are lowerthan the control group, and there is statistically significant difference betweenthem(P<0.05).6Use the ROC curves to measure Warning value of metabolites betweenlOSAHS without deafness and OSAHS with sensorineural deafnessThe study found that when the ratio of NAA and Cho both at1.93, thearea under the ROC curve was73%, the diagnostic sensitivity is92%and thespecificity is78%. This suggests that when NAA／Cho is less than1.93,OSAHS patients may be complicated by sensorineural deafness, which can beused as a specific marker to screen sensorineural deafness from the OSAHSgroup. Cho／Cr and NAA／Cr of the area of curve <50%, its diagnosticaccuracy is not high, so it is not considered.Conclusion:1The incidence of hearing loss in OSAHS patients was significantly higherthan in normal healthy people, when increasing in AHI index it shows anincreasing trend.2The study finds that OSAHS without sensorineural hearing loss appearesearly auditory cortex neurons signs of metabolic dysfunction, but it is moreserious in the OSAHS group with sensorineural hearing loss.3It show that NAA／Cho may be used as early warning indicators todetermine the population of sensorineural hearing loss combining with neural metabolites changes and curve of ROC.