Optical coherence tomography as an adjunct during carotid artery stenting for carotid web

PRACTICAL IMPLICATIONS

Consider optical coherence tomography as an adjunct to visualize the membrane of a carotid web, the extent of the web, and aid in placement of a carotid stent.

A 48-year-old woman with migraines and tobacco use presented with left-sided paresthesias and left hand clumsiness. On further questioning, she had experienced multiple previous transient ischemic attacks (TIAs) including left face and arm numbness (3 events), left hand clumsiness, and weakness of the left arm, which were suggestive of recurrent right carotid artery embolization. The neurologic examination was unremarkable aside from subjective decrease sensation to pin-prick on the left side. Furthermore, her MRI showed a clinically silent acute right frontal opercular stroke (figure 1). CT angiography showed a thin smooth linear filling defect within the right proximal internal carotid artery (ICA) on axial sequences and a shelf-like defect on the oblique sagittal views consistent with carotid artery bulb web.¹ This was confirmed with cerebral angiography, which showed retrograde delayed filling of the carotid bulb web and stasis within the pouch. Although there was no flow-limiting stenosis, given the ICA stasis and current right middle cerebral artery territory stroke with previous TIAs, it was felt that the patient was at an increased risk of thromboembolic events and will need either lifelong anticoagulation or surgical intervention. After discussion with the patient and stroke neurologist, it was decided to proceed with carotid artery stenting (CAS) to treat the symptomatic carotid web.

Figure 1. Diagnostic imaging—acute stroke and carotid web.

Diagnostic imaging confirms the presence of acute stroke and carotid web. (A) MR DWI sequences demonstrate right frontal opercular infarct (white arrow). (B) Axial CT angiography shows smooth filling defect (white arrow). (C) Oblique sagittal CT angiography shows shelf-like filling defect due to thick membrane band (white arrow). (D) Cerebral angiogram shows retrograde delayed filling (white arrow) into the pouch created by the web membrane. (E) Delayed cerebral angiogram showing eventual filling of the pouch and shelf-like filling defect of the web (white arrow). (F) Illustration of the carotid web pouch with a thick band at the base. The delayed contrast filling is due to clot/blood already present within the pouch.

The CAS procedure was performed under light sedation and local anesthetic. A 10⁻⁷ × 30 tapered Protege stent (Medtronic, Minneapolis, MN) was placed. Intravascular optical coherence tomography (iOCT) images were acquired using the C7-XR (Dragonfly; LightLab, Westford, MA) catheter both before and after stent deployment (figure 2). Using iOCT, the thin membrane-like septum of the carotid web was visualized and confirmed acceptable stent-strut apposition after stent deployment.

Figure 2. Intravascular optical coherence tomography.

iOCT imaging performed before/after carotid web stenting. (A) Axial iOCT showing a bulge in the vessel wall at the base of the web, which can be seen on the sagittal angiogram (white arrow). The green line indicates the axial reference for B to D. (B–D) Oblique iOCT images moving sequentially cephalad from the green reference line shown in A. The white arrow depicts the carotid web membrane, and the yellow arrow shows the pouch formed by the membrane. The blue arrow is an artifact from the iOCT catheter. (E) iOCT showing good stent-strut apposition over the wall of the carotid web (white arrow shows 1 stent strut). (F) Angiogram confirming no retrograde flow into the web and no flow-limiting stenosis. iOCT = intravascular optical coherence tomography.

At the 12-month follow-up, the patient remained neurologically intact with no further stroke-like symptoms. She was continued on dual antiplatelet (acetylsalicylic acid + clopidogrel) agents after stenting for 12 months, at which point clopidogrel was discontinued.

Discussion

Carotid webs have increasingly become recognized as an etiology of recurrent ischemic stroke, especially in young patients without traditional atherosclerotic risk factors.^1,2 Our current understanding of the carotid web is that of an intimal variant of fibromuscular dysplasia.³ There is no consensus in the literature regarding the optimal management plan for these patients, as there are approximately 50 cases reported. Options include medical management (anticoagulant or antiplatelet medication) and carotid revascularization with CAS or endarterectomy. Rates of recurrent stroke/TIA on antiplatelet or anticoagulant medication can be as high as 30%.^2,4,5 This should be interpreted cautiously because of the small number of study subjects. Haussen et al.² published a series of 16 patients undergoing CAS for carotid web with no periprocedural complications, recurrent stroke/TIA, or stent restenosis at 12 months.

iOCT has been used as an adjunct during CAS for carotid stenosis.⁶ We report a case of iOCT-assisted CAS for carotid web. Briefly, the cross-sectional image formed using iOCT uses backscattered light from the vessel wall structure. Different tissue layers within the vessel wall reflect light at different amplitudes, and interferometry techniques are used to analyze this backscattered light. Near-infrared light with a wavelength of approximately 1300 nm is used, and exceptional vessel wall spatial resolution of 10–15 μm is achievable. The carotid web membrane was readily visible using iOCT (figure 2). The thickness of the membrane was approximately 0.8 mm. It is also apparent that the membrane creates a pouch against the vessel wall. The pouch is filled with blood/clot, and contrast media fill the pouch in a retrograde delayed fashion.

It is possible that a portion of patients with cryptogenic stroke have webs that cannot be visualized using CT angiography because of inadequate spatial resolution, confounded by significant ambiguity diagnosing carotid webs, as not all webs appear the same. Carotid webs may be a little recognized cause of stroke and might be more common than previously reported. Beyond confirming the presence of a web, iOCT is able to visualize the exact location and extent of the web. With iOCT, we can also better understand the pathophysiology of ischemic stroke secondary to carotid web, as one could see how emboli could develop in the pouch and be dislodged due to high velocity blood hitting the outer membrane. Finally, iOCT can confirm acceptable stent-strut apposition after stent deployment and show the obliteration of the thrombogenic pouch created by the web.

Author contributions

C.R. Pasarikovski: study concept and design; acquisition, analysis, or interpretation of data; and drafting the article. J. Ramjist: acquisition, analysis, or interpretation of data and drafting the article. L. da Costa: study concept and design; acquisition, analysis, or interpretation of data; and drafting the article. V.X.D. Yang: study concept and design; acquisition, analysis, or interpretation of data; drafting the article; and study supervision.

Study funding

No targeted funding reported.

Disclosure

The authors report no disclosures relevant to the manuscript. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/cp.