中文摘要：

目的明确首发轻度抑郁患者海马结构的细微病变。方法对自2013年5月至2016年5月在江苏大学附属医院神经科门诊的20例首发轻度抑郁患者（患者组）及20例正常人（对照组1行头颅海马MRI T1扫描，以灰度差分法对海马各结构MRI信号灰度值行对比分析。结果2组受试者海马头、体、尾部均可清晰辨认。与对照组相比，患者组双侧海马头部MRI信号灰度值的最大值、最小值及平均值均显著减低，差异均有统计学意义（P＜0．05）；但双侧海马体部及尾部MRI信号灰度值的最大值、最小值及平均值未见明显改变，差异均无统计学意义（P＞0．05）。患者组双侧海马头部MRI信号欠均匀，信号灰度曲线波形形态异常，局部呈现由海马头部外侧向内侧（与杏仁核交界处）逐渐递减的征象；但双侧海马体部及尾部MRI信号灰度曲线波形未见明显改变。结论首发轻度抑郁患者海马结构存在细微病变，其MRI信号表现为海马头部灰度值呈递减式降低。

英文摘要：

Objective To identify the minor pathological changes of the hippocampal formation in patients with mild onset depression. Methods The hippocampi of 20 patients with mild onset depression and 20 normal control subjects, collected in our hospital from May 2013 to May 2015, were scanned with magnetic resonance T1 imaging. The gray scale difference method was performed to compare the gray levels of magnetic resonance signal in each part of the hippocampus. Results The hippocampal head, body and tail of two groups could be clearly identified. As compared with those in the normal control group, the maximum value, minimum value and average gray value of magnetic resonance signal in the bilateral hippocampal head of patients with mild onset depression were significantly decreased （/9〈0.05）. The maximum value, minimum value and average gray value of bilateral hippocampal body and tail did not changed obviously, without significant difference between the two groups （P〉0.05）. Bilateral hippocampal head magnetic resonance signal was not heterogeneous in patients with mild onset depression and the shapes of gray wave curve were abnormal; the local part signal from lateral direction of the hippocampus to the medial （the junction of the amygdala） exhibited a decreased tendency; bilateral hippocampus body and tail magnetic resonance signal gray level curves were not drastically changed. Conclusion There are subtle lesions in hippocampal structure of patients with mild onset depression, which could be exhibited as gray level decreasing in hippocampal head gradually on magnetic resonance images.