A small number of patients have fibromuscular disease as discussed above. The Ehlers-Danlos and Marfan syndromes, osteogenesis imperfecta, Loeys-Dietz syndrome (transforming growth factor [TGF]-b receptor mutation), and α1-antitrypsin deficiency are also associated with an increased risk of vascular dissection. One of these conditions should be suspected if multiple extracranial vessels are involved in spontaneous dissections or if there is joint and skin laxity or widespread vascular tortuosity (neck and thoracic trauma or aortic arch dissection are more common causes of multiple extracranial dissections).
A few patients with carotid dissection have had preceding unilateral cranial or facial pain lasting days, followed by stroke in the territory of the internal carotid artery. The pain is aching, may fluctuate in severity, and is centered most often in and around the eye on the side of the dissection; less often, it is in the frontal or temporal regions, angle of the mandible, or high anterior neck over the carotid artery. Rapid and marked relief of the pain after the administration of corticosteroids in a young person may be a helpful diagnostic feature (see below). Neck pain over a site of dissection is usually present as well; however, it may be absent, particularly if the dissection originates near the base of the skull.
The ischemic manifestations consist of transient attacks in the territory of the internal carotid, followed frequently by the signs of hemispheral stroke, which may be abrupt or evolve smoothly over a period of minutes to hours or over several days in a fluctuating or stepwise fashion. A unilateral Horner syndrome is often present. A cervical bruit, sometimes audible to the patient, amaurosis fugax, faintness and syncope, and facial numbness are less common symptoms. Most of the patients described by Mokri and colleagues (1986) had one of two distinct syndromes: (1) unilateral headache associated with an ipsilateral Horner syndrome, essentially the Raeder syndrome, or (2) unilateral headache and delayed focal cerebral ischemic symptoms. One lesson is that a painful Horner syndrome is usually due to an underlying structural lesion. Some patients have evidence of involvement of one or more of the vagi, spinal accessory, or hypoglossal nerve on the side of a carotid dissection; these nerves lie in close proximity to the carotid artery and are nourished by small branches from it.
In most cases, dissection of the internal carotid artery can be detected by ultrasonography and confirmed by MRI and CTA, which show a double lumen (Fig. 33-20) within the vessel on axial MRI sections. Arteriography by any method, including by conventional angiography usually reveals an elongated, but variable length, irregular narrow column of dye, usually beginning 1.5 to 3 cm above the carotid bifurcation and extending to the base of the skull, a picture that has been called the string sign. There may be a characteristic tapered occlusion or an outpouching at the upper end of the string. It is the site and the shape of the occlusion that are helpful in identifying dissection. Less often the dissection is confined to the midcervical region, and occasionally it extends into the intracranial carotid or even the middle cerebral artery or involves the opposite carotid artery or the vertebral and basilar arteries. Axial images of the T-1 and of fat-saturated MRI shows the false lumen well and is often depended on for diagnosis of small dissections.