图1 男性，53岁，因左侧面部麻木1 d就诊。MRI提示半球间（胼周）脂肪瘤，胼胝体发育不良1a 正中矢状位T1WI显示，不规则管结节样病变位于大脑半球间裂，呈高信号，边界锐利（箭头所示），胼胝体发育不良 1b 横断面T2WI显示，病变呈均匀高信号，延伸于双侧侧脑室之间（箭头所示） 1c 矢状位抑脂T1WI显示，病灶内高信号消失，提示为脂肪成分（箭头所示）；病变上方与粗大的不规则辐射样脑回相邻 图2 女性，39岁，因头晕3 d就诊。MRI提示胼胝体上方和后方半球间脂肪瘤 2a 矢状位T1WI显示，胼胝体上方弧线样高信号影（箭头所示），胼胝体形态完整 2b 矢状位抑脂T1WI显示，病灶内高信号消失，提示为脂肪成分（箭头所示）Figure 1 A 53⁃year⁃old male had suffered left facial numbness for one day and came to clinic.MRI showed interhemispheric(pericallosal)lipoma and hypoplasia of corpus callosum.Median sagittal T1WI showed an irregular tubulonodular hyperintense mass with clear rim located in interhemispheric fissure(arrow indicates).Hypoplasia of corpus callosum could be seen(Panel 1a).Axial T2WI showed heterogeneous high intensity of lesion extending into bilateral ventricles(arrow indicates,Panel 1b).Sagittal fat⁃suppression T1WI showed hyperintense signal disappeared,which proved fatty content(arrow indicates).The lesion was adjacent to thick,irregular bumpy cortices(Panel 1c). Figure 2 A 39⁃year⁃old female had suffered dizziness for 3 d and came to clinic.MRI showed an lipoma in the upper and rear corpus callosum.Sagittal T1WI showed a curvilinear high⁃intensity signal in the upper corpus callosum(arrow indicates)with intact corpus callosum(Panel 2a).Sagittal fat⁃suppression T1WI showed hyperintense signal disappeared,which proved fatty content(arrow indicates,Panel 2b).

颅内脂肪瘤是少见的包含脂肪成分的良性病变，占全部颅内肿瘤的0.1%～0.5%，源自胚胎期原始脑膜残留和异常分化，好发于胼胝体、四叠体池、环池和鞍上池等中线结构，大脑凸面和侧裂少见，多合并不同程度脑发育畸形，尤以胼胝体缺如和（或）发育不良多见，其他还包括透明隔缺如、小脑蚓部发育不良、颅裂畸形、动脉瘤等，通常无临床症状。典型征象为CT呈现特征性脂肪低密度影，边界清晰，病灶周围可见钙化；增强扫描无强化。MRI可以鉴别病变内脂肪成分，具有一定特异性，T1WI呈高信号（图1a），T2WI呈稍高和高信号（图1b），抑脂序列呈极低信号，提示病变内脂肪成分（图1c）；增强扫描无强化，应注意采用抑脂序列以区分脂肪成分与异常强化导致的短T1信号。半球间（胼周）脂肪瘤是颅内脂肪瘤的最常见类型，通常有管结节样和弧线样两种形态，前者多位于胼胝体前部，体积较大，呈不规则长管状或分叶状，常伴胼胝体缺如和（或）发育不全（图1）；后者多位于胼胝体后上部，病变细长，呈“C”形包绕胼胝体压部，合并胼胝体异常概率和严重程度较前者低（图2）。应注意与其他含脂肪成分的颅内病变（如皮样囊肿、畸胎瘤等）和T1WI呈高信号的颅内病变（如颅咽管瘤、胶样囊肿、内胚层囊肿、合并出血的蛛网膜囊肿、含黑色素细胞的肿瘤和亚急性或慢性血肿等）相鉴别。

（天津市环湖医院神经放射科韩彤供稿）