The prevalence of blunt carotid artery injury is as high as 0.50% in all patients with blunt trauma.[3–8] Motor vehicle accidents are the most common cause of blunt carotid artery trauma, with studies showing a prevalence of 0.67% in victims of motor vehicle accidents.[9] Our study describes the two trauma patients were diagnosed with acute ischemic stroke delayed after hospitalization. All these two patients were suffered acute ischemic stroke after motor vehicle accidents, but the reason of cerebral infarction may be different in the two patients. The reason of the first patient is traumatic internal carotid artery dissection and the reason of the second patient may be plaque shedding due to blunt injury.
Crissey described four possible mechanisms that can lead to a blunt carotid injury, including direct blow to the neck, neck hyperextension associated with rotation, blunt intra–oral trauma and basilar skull fracture involving the carotid canal.[10] Although direct blow to the neck are the most common cause at 50%, it is hyperextension with rotation that is the direct cause of carotid artery injury in most motor vehicle accidents. The compression of the internal carotid artery by the mandible and upper cervical vertebrae during hyperextension with rotation in a traffic accident may have contributed to the development of carotid artery dissection (CAD) and plaque shedding.[11, 12]
Studies have shown that factors significantly associated with carotid artery injuries include closed head injury, basilar skull fracture, facial fracture, spinal (especially cervical spine) fracture and thoracic injury, with closed head injury being the most common single associated injury.[13] It has also been suggested that combined injuries to the head, face and cervical spine and combined head and chest injuries significantly increase the risk of carotid artery injury.[3, 14] Unlike previously reported carotid artery injuries, our patient's carotid artery injury was not combined with other injuries.
Although headache and neck pain are the most common clinical manifestations of traumatic carotid injury, the diagnosis of blunt cerebrovascular injuries is frequently delayed due to the absence of initial signs and symptoms.[15] Besides, two studies have shown that over 40% of patients develop signs and symptoms sometimes after the initial normal neurological examination.[4, 16] Koleitat et al. reported that a delayed diagnosis greater than 48 hours significantly worsens outcomes after blunt cerebrovascular injuries.[17] Biffl et al. recommended aggressive screening to reduce delayed diagnosis and missed diagnoses in patients with severe cervical hyperextension/rotation or hyperflexion compatible trauma mechanisms, evidence of cerebral infarction on CT, or unexplained neurological deficits, TIA or Horner's syndrome.[18]
CT angiography (CTA) and MRI/Magnetic Resonance Angiography (MRA) are currently the preferred imaging tests for suspected blunt cerebrovascular injuries. CTA allows rapid diagnosis of blunt cerebrovascular injuries and is particularly useful for early detection in the emergency room for severely injured patients, but some patients are unable to undergo CTA due to allergic reactions to the contrast medium. MRI/MRA can provide a comprehensive assessment of blunt cerebrovascular injuries, but is usually slower than CTA and some trauma patients are unable to cooperate with the completion of an MRI/MRA. Ultrasound is a non-invasive, bedside, real-time diagnostic tool that is an effective method for diagnosing blunt cerebrovascular injuries. Although ultrasound relies on operator experience and is poorly visualised for intracranial vascular ultrasound, it is useful for the progression or recanalisation of blunt cerebrovascular injuries. Although our patient was asymptomatic, if we had screened this patient with ultrasound, we might have detected his blunt cerebrovascular injuries much earlier.
Although there are several treatment options for cerebrovascular dissection, including observation with expectant management, antiplatelet agents, anticoagulation, thrombolysis, stenting and surgery.[19] Patients with blunt cerebrovascular injuries are prone to thrombosis leading to stroke, so anticoagulation and antiplatelet therapy are the cornerstone treatment when contraindications are ruled out. In our cases, thrombolysis and therapeutic anticoagulation were not started as because this was a massive stroke with a high risk of haemorrhagic transformation; instead, he was initially started on antiplatelet agents.
In summary, car accident injuries may lead to traumatic blunt cerebrovascular injuries, especially in those who present with severe headaches and neck pain. Delayed clinical symptoms may occur in such a condition of traumatic blunt cerebrovascular injuries. Ultrasound, CTA and MRI are very important for the early diagnosis of blunt cerebrovascular injuries. Therefore, clinicians should be cautious in treating traumatic blunt cerebrovascular injuries patients with severe headaches and neck pain.