目前，一項發(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)異常可能涉及不同的病理生理學機制,。
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結(jié)果,，一些研究發(fā)現(xiàn)各向異性分數(shù)（FA）值降低,，而另有一些研究指出FA值增加或無結(jié)果。導致結(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)異常進行對照評估,。
本研究采用DTI技術(shù)，對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例健康對照者的腦白質(zhì)完整性進行了評估,。三組在年齡,、性別、受教育程度以及智能方面無差異,。
基于體素的形態(tài)學研究指出,，與對照組相比，雙相障礙患者腦部多個聯(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照組在FA值方面的差異無統(tǒng)計學意義,。
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)域的的平均擴散率（水分子的擴散大?。┚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散率方面無統(tǒng)計學差異。
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,，與對照組相比，精神分裂癥患者軸向和徑向擴散率均增加,；FA值降低的雙相障礙患者,，沿著纖維束方向，其徑向擴散率增加（而非軸向擴散率）,。
研究者們指出,，精神分裂癥患者的腦內(nèi)軸向和徑向擴散率均增加，這可能能夠解釋為何精神分裂癥患者與對照組在FA值方面無差異,。原因是軸向和徑向擴散率同時增加可能不會導致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散率均增加，提示軸突外空間內(nèi)的水內(nèi)容物增多,。”
本項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機制。（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.
