Grading scale for blunt cerebrovascular injury. adapted from Biffl et al22 31
| Grade | Definition | Natural history | Treatment |
| I | Arterial wall irregularity or dissection/intramural hematoma with less than 25% luminal stenosis | Typically heal spontaneously or with medical therapy alone; 4–14% will progress to a higher grade | Typically managed medically with IV heparin or antiplatelet therapy |
| II | Intraluminal thrombus, raised intimal flap, dissection/intramural hematoma with greater than 25% luminal stenosis, or small arteriovenous fistula* | Commonly progress; 29–70% will progress to grade III or grade IV on follow-up angiography | Medical treatment with IV heparin or antiplatelet therapy is recommended. Endovascular intervention, generally involving stent placement, should be considered if the lesion progresses or in patients remaining symptomatic despite medical therapy |
| III | Pseudoaneurysm | Typically persistent or progress; only 8% improve spontaneously | Medical treatment with IV heparin or antiplatelet therapy is recommended. Additional endovascular or surgical intervention should be considered in lesions that grow or exert mass effect |
| IV | Complete arterial occlusion | High risk of morbidity and mortality due to secondary infarction; spontaneous recanalization occurs in 14–25% of cases and is a source of distal thromboembolism | IV heparin is most effective at reducing the rate of ischemic stroke, though thrombectomy may be indicated in some cases. Parent vessel occlusion may be necessary in patients remaining symptomatic despite medical therapy |
| V | Complete arterial transection or hemodynamically significant arteriovenous fistula* | Mortality rate is as high as 50% | Prompt surgical hemostasis is the preferred treatment. Endovascular intervention is helpful for surgically inaccessible lesions |
*Reflects a 2002 classification by Biffl and colleagues.22 More recent literature has categorized all traumatic arteriovenous fistulas as grade V.60 61