目前,，一項(xiàng)發(fā)表在Bipolar Disord雜志上的研究"White matter microstructure in untreated first episode bipolar disorder with psychosis: comparison with schizophrenia"指出,，與精神分裂癥患者相比,，雙相障礙患者的腦白質(zhì)微結(jié)構(gòu)異?？赡苌婕安煌牟±砩韺W(xué)機(jī)制,。
Lisa Lu（Roosevelt University, Chicago, Illinois）和她的同事們指出,，先前的,、有關(guān)雙相障礙患者腦白質(zhì)微結(jié)構(gòu)異常的彌散張量成像（DTI）研究有多種不同的試驗(yàn)結(jié)果,，一些研究發(fā)現(xiàn)各向異性分?jǐn)?shù)（FA）值降低,，而另有一些研究指出FA值增加或無(wú)結(jié)果。導(dǎo)致結(jié)果不一致的可能的原因是樣本的異質(zhì)性,。大多數(shù)受試者在納入研究前,，已有多年的疾病史和異質(zhì)性藥物治療史。此外,，很少有研究對(duì)雙相障礙和精神分裂癥患者的腦白質(zhì)微結(jié)構(gòu)異常進(jìn)行對(duì)照評(píng)估,。
本研究采用DTI技術(shù)，對(duì)13例未治療,、首次精神病性發(fā)作的雙相障礙患者,、21例未治療、首次精神分裂癥發(fā)作患者以及18例健康對(duì)照者的腦白質(zhì)完整性進(jìn)行了評(píng)估,。三組在年齡,、性別、受教育程度以及智能方面無(wú)差異,。
基于體素的形態(tài)學(xué)研究指出,，與對(duì)照組相比,，雙相障礙患者腦部多個(gè)聯(lián)合、投射和相關(guān)部位的FA值降低,；相反地,，精神分裂癥患者與健康對(duì)照組在FA值方面的差異無(wú)統(tǒng)計(jì)學(xué)意義。
與精神分裂癥患者相比,，雙相障礙患者在扣帶回,、內(nèi)囊、后腦部區(qū)域（后胼胝體,、腦毯以及枕葉白質(zhì)包括后丘腦輻射區(qū),、下縱束以及下額枕束）等部位FA值降低。
與健康對(duì)照者相比,，雙相障礙和精神分裂癥患者在以下腦部區(qū)域的的平均擴(kuò)散率（水分子的擴(kuò)散大?。┚黾樱蹘Щ?、內(nèi)囊,、腦毯、枕葉白質(zhì)（包括后丘腦輻射區(qū),、下縱束以及下額枕束）,。雙相障礙和精神分裂癥患者在平均擴(kuò)散率方面無(wú)統(tǒng)計(jì)學(xué)差異。
研究指出,，雙相障礙和精神分裂癥患者腦部區(qū)域的FA值存在差異,，與對(duì)照組相比，精神分裂癥患者軸向和徑向擴(kuò)散率均增加,；FA值降低的雙相障礙患者,，沿著纖維束方向，其徑向擴(kuò)散率增加（而非軸向擴(kuò)散率）,。
研究者們指出,，精神分裂癥患者的腦內(nèi)軸向和徑向擴(kuò)散率均增加，這可能能夠解釋為何精神分裂癥患者與對(duì)照組在FA值方面無(wú)差異,。原因是軸向和徑向擴(kuò)散率同時(shí)增加可能不會(huì)導(dǎo)致FA值變化,。
Lisa Lu和她的同事們總結(jié)到：“雙相障礙患者選擇性的軸向擴(kuò)散率增加，提示纖維束結(jié)構(gòu)異常與髓鞘神經(jīng)發(fā)育或改變相一致,。相反地,，精神分裂癥患者軸向和徑向擴(kuò)散率均增加，提示軸突外空間內(nèi)的水內(nèi)容物增多,。”
本項(xiàng)研究提示雙相障礙和精神分裂癥患者腦白質(zhì)微結(jié)構(gòu)異?？赡艽嬖诓煌纳聿±韺W(xué)機(jī)制。（生物谷Bioon.com）
doi:10.1111/j.1399-5618.2011.00958.x
PMC:
PMID:
White matter microstructure in untreated first episode bipolar disorder with psychosis: comparison with schizophrenia
Lisa H Lu1,2, Xiaohong Joe Zhou3, Sarah K Keedy2, James L Reilly2, John A Sweeney2
Objectives:White matter abnormalities have been reported in bipolar disorder. The present study aimed to investigate white matter integrity in untreated first episode patients with psychotic bipolar disorder using diffusion tensor imaging, and to compare observations with those from untreated first episode schizophrenia patients.
Methods:Fractional anisotropy and mean diffusivity were measured in first episode psychotic patients with bipolar disorder (n = 13) or schizophrenia (n = 21) and healthy individuals (n = 18). Group differences were evaluated using voxel-based morphometry. Axial and radial diffusivity were examined in regions with altered fractional anisotropy in post-hoc analyses.
Results:Patients with bipolar disorder showed lower fractional anisotropy than healthy controls in several white matter tracts. Compared with schizophrenia patients, bipolar disorder patients showed lower fractional anisotropy in the cingulum, internal capsule, posterior corpus callosum, tapetum, and occipital white matter including posterior thalamic radiation and inferior longitudinal fasciculus/inferior fronto-occipital fasciculus. Lower fractional anisotropy in bipolar disorder was characterized by increased radial diffusion rather than axial diffusion along the orientation of fiber tracts. Across several white matter tracts, both patient groups showed greater mean diffusivity than healthy individuals.
Conclusions:Selectively increased radial diffusivity in bipolar disorder patients suggests structural disorganization in fiber tract coherence of neurodevelopmental origin or alterations in myelin sheaths along fiber tracts. In contrast, increased isotropic diffusion along white matter tracts in schizophrenia patients with alterations in both radial and axial diffusivity suggests increased water content outside the axonal space. Thus, the present results suggest that different pathophysiological mechanisms may underlie white matter microstructural abnormalities in bipolar disorder and schizophrenia.
