Research On Cognitive Function And Proton Magnetic Resonance Spectroscopy In Bipolar Remitted Patients

ObjectiveIn order to explore the characteristics of cognitive impairment and the abnormal brain metabolism in bipolar remitted(BPR) patients, we assessed the cognitive function in BPR patients by the neuropsychological tool and the brain metabolite levels by the1H-magnetic resonance spectroscopy(1H-MRS), and compared them with the drug-naive bipolar depressed(BPD) patients and the control group. Moreover, through the analysis of the correlation between the cognitive impairment and abnormal brain metabolism in patients of BPR, we supported the guidance on the mechanism of cognitive impairment and treatment of bipolar disorder(BD).MethodsAccording to the DSM-IV diagnostic criteria, we chose 30 BPR patients whose clinical symptoms had disappeared at least six months, 30 drug-naive BPD patients and 30 healthy controls to attend this study. Gender, age and education level of three groups were matched. We evaluated their cognitive function by the following 7 cognitive tests: 1. Symbol Digital Modalities Test(SDMT), 2. Trail Making Test(TMT), 3. Digital Span Test(DST), 4. Visual Reproduction Subtest(VRS), 5. Wisconisin Card Sorting Test-modified(WCST), 6. Verbal Fluency Test(VFT), 7. Stroop Color and Word Test(SCWT). After completing the assessment of cognitive function, we detected the N-acetylasparte(NAA), choline-containing compounds(Cho), myo-Inositol(mI) and creatine(Cr) levels in bilaterally frontal lobe white matter,thalamus, lenticular nucleus of basal ganglia of three groups by mean of1H-MRS technology.We compared cognitive function and brain metabolites levels of three-group by One-Way ANOVA analysis. Furthermore, associations between cognitive impairments and abnormal brain metabolites in BPR patients were analysed.Results1. Results of the assessment of cognitive function: the SDMT score of BPR patients and BPD patients was lower than healthy controls(P < 0.05). Moreover, the SDMT score of BPR patients was higher than BPD patients(P < 0.05). The DST(forward, backward, total) scores of BPR patients and BPD patients were lower than healthy controls(P < 0.05). The VRS score of BPRpatients and BPD patients was lower than the healthy controls(P < 0.05). The WCST(total errors, perseverative errors) of BPR patients were more than the control group(P < 0.05). The VFT score of BRP patients and BPD patients was lower than the control group(P < 0.05). BPD patients in SCWT 3 took longer than the control group(P < 0.05). There were no significant differences among groups for other cognitive function tests(P > 0.05).2. Results of 1H-MRS: NAA/Cr ration of bilaterally frontal lobe white matter in BPR patients and healthy controls was higher than BPD patients(P < 0.05). Cho/Cr ration of left thalamus in BPR patients was higher than BPD patients and healthy controls(P < 0.05). There were no significant differences among groups for other brain metabolites(P > 0.05).3. Results of correlation analyses in BPR patients group:① Correlation between cognitive impairment and clinical features: SDMT, DST(forward,backward, total) and VRS scores were negatively correlated with the age of onset. The WCST(total errors, perseverative errors) were positively correlated with the total duration of illness, the DST forward score was negatively correlated with total duration of illness. The WCST perseverative errors were positively correlated with progressive duration of illness, the DST forward score was negatively correlated with progressive duration of illness. The WCST(total errors, perseverative errors) were positively correlated with remitted duration of illness, the DST forward score was negatively correlated with remitted duration of illness.②Correlation between abnormal brain metabolites and cognitive impairment: Left frontal lobe white matter NAA/Cr ration were positively correlated with DST(backward, total), VRS and VFT scores, were significantly negatively correlated WCST(total errors, perseverative errors).Right frontal lobe white matter NAA/Cr ration were positively related the SDMT and VRS scores, were negatively correlated with WCST(total errors, perseverative errors).Conclusion1. Both BPR and BPD patients suffered cognitive impairments such as working memory,short-term and sustained attention and executive function. The damage of short-term attention and working memory was the characteristic cognitive impairments in BD.2. Structural integrity and functional activity of neural fiber of bilaterally frontal lobe white matter suffered damage in BPD patients. The left thalamus choline level was increased in BPR patients, which might be the compensatory reaction to protect patients.3. With later age of oneset, the damage of attention, short-term attention and executive function was more serious in BPR patients. With longer total, progressive and remitted duration of illness,the damage of short-term attention, working memory and executive function was more serious.4. The damage of nerve fiber structural integrity and decline of functional activity of bilaterally frontal lobe white matter in BPR patients may have relationship with impaired attention, memory and executive function.