Extracranial Internal Carotid Artery Dissection

KEY FACTS

TERMINOLOGY

• Internal carotid artery (ICA) dissection (ICAD)

• ICAD: Tear in ICA wall allows blood to enter & delaminate

wall layers

IMAGING

• Pathognomonic findings of dissection: Intimal flap or

double lumen (seen in < 10%)

• Aneurysmal dilatation seen in 30%

○ Commonly in distal subcranial segment of ICA

○ Focal pseudoaneurysm unusual

• Flame-shaped ICA occlusion (acute phase)

• ICAD most commonly originates in ICA 2-3 cm distal to

carotid bulb & variably involves distal ICA

• Stops before petrous ICA

• MR T1 with fat suppression best sequence for

hyperintense mural hematomas

TOP DIFFERENTIAL DIAGNOSES

• Fibromuscular dysplasia

• Carotid artery fenestration

• Traumatic ICA pseudoaneurysm

• Atheromatous plaque

• Glomus vagale paraganglioma

• Carotid space schwannoma

CLINICAL ISSUES

• Ipsilateral pain in face, jaw, head, or neck

• Oculosympathetic palsy (miosis and ptosis, partial Horner

syndrome)

• Ischemic symptoms (cerebral or retinal TIA or stroke)

• Bruit (40%)

• Lower cranial nerve palsies (especially CN10)

• Pulsatile tinnitus

(Left) Lateral graphic depicts

typical internal carotid artery

(ICA) dissection. Note

dissection begins above

bifurcation ſt & ends at skull

base ﬇. Cross section of

subintimal hematoma st is

also shown. (Right) Clinical

photograph of a patient with

an acute postganglionic

Horner syndrome shows ptosis

ſt, "upside-down" ptosis

(lower lid is up st), and

meiosis (constricted pupil ﬇).

(Left) Axial T1WI MR in a 47-

year-old man who fell skiing 3

weeks prior to developing left

frontotemporal headache

shows T1 shortening within

the crescentic subacute clot

﬇ in the false lumen of the

dissected left ICA. Note the

high signal thrombus ſt

within the true lumen of the

vessel, which was occluded.

(Right) Axial MRA source

image in the same patient

shows the high signal

thrombus in the false lumen

﬇ as well as the thrombosed

true lumen ſt. Compare to

normal flow signal of the right

ICA st.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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