Neurology：影像孤立综合征患者早期出现脑代谢水平异常

近来，在一些无症状患者中MRI会偶然发现符合多发性硬化Barkhof诊断标准的脑白质病灶，该类现象被称为影像孤立综合征(RIS)。该疾病需要更特异的研究从而对对该类患者进行危险分层。来自新西兰的Maria Laura Stromillo等医生使用磁共振氢质子波谱分析(1H-MRSI)评价了RIS患者人群的代谢变化，结果发表在2013年6月4日的neurology杂志上。研究结果显示：影像孤立综合征患者早期出现脑代谢水平异常。

研究纳入23例RIS患者，根据Okuda标准对大脑中央感兴趣区进行1H-MRSI检查，分别在病灶/病灶周围区域、正常脑白质区域和皮层灰质区(CGM)检测N-乙酰天门冬氨酸(NAA)和胆碱(Cho)与标准化肌酐(Cr)的比值。RIS患者的1H-MRSI数据与20例正常健康对照组患者(HC)进行对比。

RIS患者与健康对照组人群相比全脑区域NAA/Cr水平明显降低（p < 0.005），Cho/Cr水平没有明显不同。单因素分析显示44%的RIS患者脑白质表现正常区域及61%的RIS患者皮层灰质区域的NAA/Cr水平相比对照组至少低2个标准差。

RIS患者NAA/Cr水平降低显示脑代谢异常，预示着轴索的损伤，这可能在疾病的早期就很明显。该信息或可区分出有可能进展为多发性硬化高危RIS患者。

Brain metabolic changes suggestive of axonal damage in radiologically isolated syndrome.
BACKGROUND
The MRI incidental finding in asymptomatic subjects of brain white matter (WM) changes meeting the Barkhof criteria for the diagnosis of multiple sclerosis (MS) has been recently characterized as the radiologically isolated syndrome (RIS). This entity needs to be more specifically defined to allow risk stratification of these subjects. We used brain proton magnetic resonance spectroscopic imaging ((1)H-MRSI) to assess metabolic changes in an RIS population.
METHODS
Twenty-three RIS subjects who were classified according to the Okuda Criteria underwent (1)H-MRSI examination with a central brain (CB) volume of interest (VOI) to measure levels of N-acetylaspartate (NAA) and choline (Cho) normalized to creatine (Cr) in the whole CB-VOI, in lesional/perilesional and normal-appearing WM regions, and in the cortical gray matter (CGM). The (1)H-MRSI data were compared with those of 20 demographically matched healthy controls (HC).
RESULTS
NAA/Cr levels were significantly lower in RIS than in HC in all regions (p < 0.005 for all). No differences in Cho/Cr levels were found in either brain region. A single-subject analysis showed that NAA/Cr levels were at least 2 SDs below the HC mean in the 44% of RIS in the normal-appearing WM and in the 61% of RIS in the CGM.
CONCLUSION
Decreased brain NAA/Cr levels in a group of RIS subjects indicates that brain metabolic abnormalities suggestive of axonal damage can be significant even at this early disease stage. This information could be useful for stratifying RIS individuals with a high risk of progression to MS