Fig. 1
![Fig. 1](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs41016-019-0164-9/MediaObjects/41016_2019_164_Fig1_HTML.png)
CT image-based classification and grading system: I no obvious abnormality (grade I); II simple vein infarction without hemorrhage (grade II); III cerebral venous infarction with subarachnoid hemorrhage (grade III); IV cerebral vein infarction with hematoma (grade IV)