Teaching Case

A young male was brought to the emergency room in a state of shock following a road traffic accident. The clinician ordered a non-contrast Brain CT and MDCT angiogram of the body to rule out intracranial bleed and vascular pathology, respectively.

64 slice MDCT angiogram coronal and axial Maximum Intensity Projection(MIP) images (Fig1) show a fairly defined linear intimal flap with double lumen consistent with acute dissection in the first part of right subclavian artery (RSCA). The flap appears to extend a few centimeters distal to the origin of the right common carotid artery. A focal bulbous sac like outpouching indicating pseudoaneurysm is seen projecting anteriorly and superiorly (Fig2). The pseudoaneurysm appears to involve the right vertebral artery origin, which is better appreciated on volume rendered image (Fig.3). The distal part of the subclavian appears patent, and there is no evidence of vascular occlusion. The rest of the branches of the right sublavian artery and remaining aortic arch are normal. Bones also appear intact.

Background

Subclavian artery dissection with pseudoaneursym is rarely reported in the medical literature. It is potentially life-threatening, particularly when it leads to arterial occlusion, causing limb ischemia, and cerebral infarction within hours after injury. Common causes of subclavian artery dissection include iatrogenic (catheterization), an anomalous aortic arch, or trauma.
Subclavian artery injuries are rare, representing less than 5% of all vascular lesions [1] and less than 1% of all arterial injuries or thoracic traumatic injuries [2-4].

Clinical Perspective

Subclavian artery injuries are caused by shearing/stretching, transection, explaining the vascular injury without rib or clavicular lesions, or if there is an associated clavicle/rib fracture, the broken bone can cause compression of the subclavian artery [5]. Dissection is suspected when there are signs of brachial plexus deficits, distal pulselessness, neurovascular symptoms or progressive swelling due to hematoma [6]. In such cases, imaging should be performed as early as possible to confirm the diagnosis.

Possible complications of subclavian artery dissection include a pseudoaneurysm rupture, thrombus associated with upper extremity ischemia, massive haemorrhage due to transection of the subclavian artery or cerebral infarction due to occlusion of the subclavian artery highlighting the significance of the condition, and thus the importance of imaging in suspected cases and the need for urgent therapeutic management [5].

Imaging Perspective

MDCT angiogram is the imaging modality of choice. CT can also depict associated bone injuries clearly. Findings of dissection include intimal flap with double lumen appearance. Pseudoaneurysm is contained rupture of the arterial wall, in which true blood collects without walls, is still in contact with the artery through a channel, seen as an outpouching communicating with the artery, and should be looked for any signs of rupture. The vessel should be carefully evaluated in its entire extent to rule out any small lesions.

Outcome

Management: Therapeutic options include endovascular stenting / surgical repair.

Prognosis: The condition is potentially catastrophic and the leading causes of death are massive bleeding and traumatic brain injury [7].

Take Home Message

Traumatic Subclavian artery acute dissection with pseudoaneurysm is a rare emergency with grave complications. Prompt, accurate diagnosis is crucial for timely management, and lack of awareness of the condition may lead to missed diagnosis, jeopardizing limb and life of the patient.