新生儿缺氧缺血性脑病磁共振诊断与损伤类型的分类建议

新生儿缺氧缺血性脑病(HIE)有比较统一的临床诊断与分度标准,但是符合相同诊断标准的窒息所致HIE的临床表现、神经病理损伤类型有很大差异。磁共振成像(MRI)能很好地呈现HIE损伤类型、损伤进程,且与其远期神经发育结局密切相关,但不同MRI检查序列所反映的损伤表现可能不尽相同。弥散加权序列适宜的检查时间为出生后2~4 d,常规序列为出生后的4~8 d。HIE的MRI主要损伤类型有丘脑基底节+内囊后肢损伤、分水岭样损伤累及皮层和皮层下白质、局灶-多灶性微小性白质损伤,以及广泛全脑性损伤。严重的急性产时窒息易导致深部灰质损伤(丘脑基底节),也可累及脑干,锥体束是最易受累的白质纤维束,而反复间断性缺氧缺血以及伴有感染、低血糖等易导致分水岭区和深部白质损伤。但上述损伤类型有时很难明确区分,而是以某一类型为主,并非所有HIE都有特征性的MRI表现。

Patterns of brain injury in neonatal hypoxic-ischemic encephalopathy on magnetic resonance imaging:recommendations on classification

Although there are unified criteria for the clinical diagnosis and grading of neonatal hypoxic-ischemic encephalopathy (HIE), clinical features and neuropathological patterns vary considerably among the neonates with HIE due to birth asphyxia in the same classification. The patterns and progression of brain injury in HIE, which is closely associated with long-term neurodevelopment outcomes, can be well shown on magnetic resonance imaging (MRI), but different sequences may lead to different MRI findings at the same time. It is suggested that diffusion-weighted imaging sequence be selected at 2-4 days after birth, and the conventional MRI sequence at 4-8 days. The major patterns of brain injury in HIE on MRI are as follows: injury of the thalamus and basal ganglia and posterior limbs of the internal capsules; watershed injury involving the cortical and subcortical white matter; focal or multifocal minimal white matter injury; extensive whole brain injury. Severe acute birth asphyxia often leads to deep grey matter injury (thalamus and basal ganglia), and the brain stem may also be involved; the pyramidal tract is the most susceptible white matter fiber tract; repetitive or intermittent hypoxic-ischemic insults, with inflammation or hypoglycemia, usually cause injuries in the watershed area and deep white matter. It is worth noting that sometimes the pattern of brain injury among those described above cannot be determined exactly, but rather a predominant one is identified; not all cases of HIE have characteristic MRI findings.