Carotid Webs and Recurrent Ischemic Strokes in the Era of CT Angiography

Demographics

During a 12-month period, ipsilateral carotid webs were identified prospectively in 7 patients with acute ischemic stroke (On-line Table 1). The mean age of these patients was 50 years (range, 41–55 years); 5 of the 7 patients were women. Five of the 7 patients had recurrent stroke in the ipsilateral vascular territory; 1 of those 5 had 4 recurrent strokes in the same vascular territory. These patients, in total, experienced 14 ischemic strokes during 8.5 years with time to recurrence ranging from 1 to 97 months. In 2 patients, thrombus-like material was seen at the site of the carotid web, with changing morphology on serial CTAs, despite concurrent antiplatelet therapy. Four of 5 patients with recurrent strokes underwent carotid endarterectomy and remained stroke-free at last follow-up (range, 3–7 months). All our patients had no other identified cause of stroke after standard work-up. Patient characteristics and other details are described in On-line Table 1.

Prevalence

Estimating the period prevalence of the carotid web would need a population-based imaging study. This was not practical. We therefore attempted to study period prevalence in a hospital-based sample of convenience. CTAs from 576 patients who presented to our center from May 2012 to April 2013 with suspected stroke were reviewed. These patients had a brain MR imaging performed within 1–2 days of presenting symptoms. Seven carotid webs were identified in 576 individual patients: 4 on the left and 3 on the right (On-line Table 2). Thus, the prevalence of carotid webs in a hospital-based series is estimated at 1.2% (95% CI, 0.4%–2.5%). The mean age of these patients was 63 years (range, 47–78 years). Four of the 7 patients were women. Two of 7 patients had acute stroke in the vascular territory of the carotid web.

In our retrospective series, we also identified patients with single, small, protruding lesions in the proximal ICA. In contrast to carotid webs, these lesions were smaller and not seen on the axial sections (Fig 2). None of the patients in our prospective series had this appearance on CTA. These small protruding lesions were identified in 14/576 patients: 7 on the left and 7 on the right (On-line Table 2) for an estimated prevalence of 2.43% (95% CI, 1.3%–4.0%). The mean age of these patients was also 63 years (range, 39–90 years). Six of the 14 patients were woman. Three of 14 patients had acute stroke in the vascular territory of the small protruding lesion.

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Fig 2.

Small protruding lesions that are distinct from carotid webs in 3 different patients on sagittal and axial CTA (A–C, arrow). Axial CTA shows no septum with this lesion, unlike in carotid webs.

Pathology

Each of the endarterectomy specimens was characterized by foci of marked fibroelastic thickening of the intima. None contained the necrotic, cholesterol-rich core of a classic atheroma. In 1 specimen, there was a shelf of intimal fibrous tissue that projected into the lumen (Fig 3A). In 2 cases, the fibrous intimal cushion was split by a dissection: One showed an organizing hemorrhage within (Fig 3B), while another formed an open endothelial-lined cavity (Fig 3C). Specimens from another case contained a thick fibrous intimal cushion with a recent mural thrombus (Fig 3D). As is characteristic of endarterectomy specimens, each specimen had an attenuated rim of elastin-rich medial tissue, but in none was a full-thickness medial section available.

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Fig 3.

Figures show the histopathology of carotid webs. A, A shelf-like projection of abnormal intimal fibrous tissue. B, Focal hemorrhagic dissection with early organization. C, Fibrous intimal thickening with focal dissection into the fibrotic intima. D, Focal fibrous intimal thickening with adherent thrombus.

Below we describe the clinical history and imaging findings of 2 patients in detail.

Patient A

A 54-year-old man (patient 1, On-line Table 1) was found slumped on the sofa with left-sided hemiparesis. He was last seen healthy 45 minutes prior. Medical history was unremarkable apart from a remote episode of transient left-arm weakness and numbness. On arrival, he had moderate left hemiplegia, neglect, and sensory loss; the National Institutes of Health Stroke Scale score was 11. Noncontrast brain CT showed early ischemic changes in the lentiform nucleus and the lateral MCA territory (ASPECTS = 8). CT angiography showed a mid-M1 occlusion on the right. Intravenous tPA was given followed by intra-arterial tPA combined with primary thrombus angioplasty. At 4 hours poststroke, his NIHSS score was zero. A shelf-like narrowing at the proximal right internal carotid artery with no ulceration was noted both on CTA (Fig 1A) and at the time of the catheter angiography. Investigations were negative for diabetes or hyperlipidemia; 24-hour Holter monitoring and transthoracic echocardiogram findings were normal. The patient made a full recovery and was treated with dual antiplatelet therapy for 3 months, followed by acetylsalicylic acid (ASA) and simvastatin, 40 mg long term.

Eight years later, the patient woke up with acute mild left hemiparesis with an NIHSS score of 4. He had stopped ASA 7 days prior for excision of a basal cell carcinoma on his left ear and restarted ASA the night before his presentation. NCCT showed no new ischemic change; CTA showed a new proximal right M1 occlusion and the same shelf-like narrowing in the right ICA (Fig 1B). Because he was last seen healthy >12 hours prior, no thrombolysis was administered. He received a loading dose of clopidogrel. MR imaging showed a new striatocapsular infarct with persistent occlusion of the M1 MCA 2 days later. Repeat CTA 4 days later showed changing morphology of the right carotid web (shelf-like narrowing), suggestive of thrombus formation in the setting of dual antiplatelet therapy (Fig 1C). Transcranial Doppler studies on 2 occasions were negative for microembolic signals. Clopidogrel was stopped, and he was treated with intravenous unfractionated heparin and ASA for 3 days with resolution of the thrombus on repeat CTA 5 days later (Fig 1D). Carotid endarterectomy was performed 12 days poststroke. Pathology from carotid endarterectomy showed a focal shelf-like projection of the fibrotic intima into the lumen without any changes typical of atherosclerosis (Fig 3A).

Patient B

A 59-year-old woman (patient 2, On-line Table 1) presented with sudden onset of left hemiparesis. There was a history of recurrent right hemispheric strokes 2 and 7 years prior for which she was treated with ASA and had no residual symptoms. On arrival, she had an NIHSS score of 11. NCCT of the brain showed an old right basal ganglia infarct with early ischemic changes in the right insula and right M2 region; her ASPECTS was 8. CTA revealed a right M1 MCA occlusion and a carotid web just distal to the ICA bifurcation with probable thrombus-like material attached (Fig 1E). She received IV tPA followed by endovascular therapy. Recanalization (TICI 2b/3) was achieved postprocedure with an NIHSS score of 2. She was discharged on dual antiplatelet therapy.

One month later, the patient was found hemiplegic on the left side. On arrival, her NIHSS score was 12. NCCT showed early ischemic changes in the right temporal cortex; CTA again showed a right M1 occlusion. The carotid web in the right ICA was again noted (Fig 1F). She was treated with endovascular therapy, and the right MCA recanalized. Her NIHSS score was 1 postprocedure. This time, right carotid endarterectomy was performed 8 days poststroke, with pathology showing fibrous intimal thickening with focal hemorrhagic dissection (Fig 3B). There was no history to suggest medication noncompliance before her recent stroke.