Department of Anaesthesia, Intensive Care Medicine and Neurosurgery, Beaumont Hospital, Beaumont Road, Dublin 9, Ireland
Accepted for publication: April 14, 2000
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Abstract |
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Br J Anaesth 2000; 85: 4768
Keywords: complications, accidents; complications, trauma; complications, fibromuscular dysplasia; arteries, carotid
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Introduction |
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Case report |
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The patient was transferred to the neurosurgical intensive care unit for invasive arterial pressure monitoring and neurological observations. Supplemental oxygen was administered by facemask. Aspirin 300 mg once daily by mouth was prescribed for its antiplatelet effect. A second brain CT on hospital day 2 demonstrated haemorrhagic transformation of the right parietal lobe infarct. Duplex scan and magnetic resonance angiogram of the carotid arteries was inconclusive. Contrast angiography revealed bilateral internal carotid artery dissection, fibromuscular dysplasia of the internal carotid arteries and thrombus in the right internal carotid artery (Fig. 1). Heparin was commenced with a target activated partial thromboplastin time of 60 s. Warfarin was commenced with a target prothrombin time of 26 s.
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Discussion |
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Fibromuscular dysplasia is an arterial developmental abnormality of unknown aetiology affecting medium-sized arteries.4 5 The incidence of the disorder based on a series of 20 244 post-mortems is two per 1000 population.4 There are four known subtypes, each with its own unique histological appearance (intimal fibroplasia, medial fibroplasia, medial hyperplasia and perimedial dysplasia).5 Affected vessels are elongated, kinked and punctuated with stenoses and microaneurysms.5 These abnormalities produce unique angiographic features which radiologists call the string of beads appearance (Fig. 1). The presence of fibromuscular dysplasia may compromise the structural integrity of the affected vessels, including the carotid artery, and therefore predispose to vessel dissection after traumatic injury.
Patients with fibromuscular dysplasia are asymptomatic until they sustain a vessel dissection. They then present with ischaemia of the organs supplied by the affected vessel, for example cerebrovascular accident. Fibromuscular dysplasia is found in 15% of cases of spontaneous carotid dissection.2 6 A report of bilateral internal carotid and vertebral artery dissection in a patient with fibromuscular dysplasia after a road traffic accident has been described.7 Arteriography is the gold standard diagnostic test for both fibromuscular dysplasia and blunt carotid injury.5 8
The management of carotid artery dissection is controversial. Heparinization was associated with an improved outcome in the largest series of blunt carotid injuries.3 However, the safety and efficacy of anticoagulation in the management of stroke following carotid injury has not been demonstrated.9 In our patient, the apparent benefit of heparinization had to be balanced against the risks of a worsening stroke.
Airbag usage is increasing worldwide and is now mandatory in new cars in some countries.1 Airbags function by preventing traumatic impact between the vehicle occupant and the vehicle interior. During a road traffic accident, sensors in the vehicle body detect deceleration and trigger airbag deployment.1 To protect against injury, airbags must be fully expanded before the vehicle occupant is propelled forward by the deceleration of the accident. An airbag expansion speed of 200 mph is necessary. This rapid forceful expansion causes airbag-associated injury in 43% of deployments. In addition, fatal rupture of the ventral ligaments of the cervical spine and brain stem has been described secondary to forced neck extension.10
An increase in the incidence of airbag-associated injury is predicted.1 Drivers of short stature, as in this case, are at increased risk of these injuries.8 9 Their short stature makes it necessary to move the vehicle seat forward in order to reach the foot pedals, thereby bringing the upper body into the path of the expanding airbag. In the USA it is now recommended that airbags should be decommissioned if drivers cannot keep a wheelchest distance of 10 inches.1
The evidence for airbag-mediated blunt carotid injury by means of forced neck extension is compelling in this case. A less likely explanation is that the patient initially sustained spontaneous carotid artery dissection because of fibromuscular dysplasia and then crashed. However, spontaneous dissections of the carotid artery typically present initially with minor clinical manifestations (e.g. headache),10 and only develop neurological signs after several days.11 12
In summary, this is the first case report of bilateral internal carotid artery dissection, in a patient with fibromuscular dysplasia, associated with airbag deployment. The report suggests that clinicians should consider the possibility of carotid injury when neurological deterioration occurs after a road traffic accident with airbag deployment. Associated conditions, such as fibromuscular dysplasia, may increase the risk of carotid artery injury in this setting. Early carotid angiography is warranted to make the diagnosis.
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Footnotes |
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References |
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