Carotid Stenosis and Stroke: Historical Perspectives Leading to Current Challenges.

The carotid artery is unique; it is the only vessel to bifurcate into a bulb larger than itself. The history of its anatomic description, understanding of its pathophysiology and evolution of its imaging are relevant to current controversies regarding measurement of stenosis, surgical/endovascular therapies and medical management of carotid stenosis in stroke prevention. Treatment decisions on millions of symptomatic and asymptomatic patients are routinely based on information from clinical trials from over 30 years ago. This article briefly summarizes the highlights of past research in key areas and discuss how they led to current challenges of diagnosis and treatment.

Safety Evaluation of Primary Carotid Stenting: Transcranial Doppler and MRI.

BACKGROUND AND PURPOSE: Cerebral emboli are generated by every step of standard carotid angioplasty and stenting. Primary carotid stenting (PCS) is a technique in which the use of balloon angioplasty (BA) is minimized to decrease the embolic load. The primary aim of this study is to establish the number of emboli generated by each step of primary stenting and determine the relationship to new diffusion (DWI) lesions on subsequent magnetic resonance imaging (MRI). METHODS: Eighty-five patients with severe, symptomatic carotid stenosis were prospectively recruited and underwent carotid stenting. Intraoperative transcranial Doppler was performed in 77 patients. The number and size of microemboli for each of seven procedural steps were recorded. Correlation was made with the number and location of new DWI lesions. RESULTS: PCS was performed in 73 patients. BA was required in 12 patients. The mean number of microemboli was 114, and most microemboli were generated by stent deployment, followed by BA. Balloon techniques generated significantly more emboli than primary stenting (p = 0.017). There was a significant relationship between total microemboli and new DWI lesions (p = 0.009), and between new DWI lesions in multiple territories and the severity of pretreatment stenosis (p = 0.002). CONCLUSIONS: During PCS, more emboli are generated by stent deployment than during any other stage of the procedure. When BA is necessary, more malignant emboli are generated but total emboli are unchanged and there is no difference in new diffusion lesions on MRI. PCS is safe and is not inferior to historical controls for the generation of new DWI lesions.

Neuroprotection in Acute Ischemic Stroke: A Brief Review.

The goal of effective neuroprotection in acute ischemic stroke remains elusive. Despite decades of experimental preclinical and clinical experience with innumerable agents, no strategy has proven to be beneficial in humans. As endovascular therapies mature and approach the limits of speed and efficacy, neuroprotection will become the next frontier of acute stroke care. This review will briefly summarize the history, preclinical and clinical triumphs and failures, and future directions of cerebral neuroprotection.

Investigating the Association between Aortic Arch Variants and Intracranial Aneurysms.

BACKGROUND: There is an association between anterior cerebral artery vessel asymmetry and anterior communicating artery aneurysm, presumably based on flow dynamics. The purpose of this study is to investigate the potential relationship between aortic arch branching patterns and incidence of intracranial aneurysm. METHODS: This study included patients scanned over 1 year at our tertiary care center who underwent high-resolution imaging (computed tomography angiography or digital subtracted angiogram) of the head and neck arteries, aortic arch, and superior mediastinum. Exclusion criteria included patients with suboptimal images. Patient age, gender, aortic arch branching pattern, and the presence, location, and number of aneurysms were documented. RESULTS: Among the 1082 patients analyzed, 250 (23%) patients had a variant aortic arch branching pattern, 22 (8.8%) of whom had aneurysms. There were 104 patients with 126 aneurysms, with majority of patients with normal aortic arch branching pattern (n = 82, 79%). The most common variant was a common origin of the left common carotid artery and brachiocephalic trunk with or without direct origin of the left vertebral artery. Twenty-two patients with aneurysms had an aberrant aortic arch (21%), compared to 232 patients without an aneurysm (24%). Fischer exact test showed no statistically significant difference between the incidence of aneurysm with different aortic arch variant groups (two-tailed p-value = 0.715). CONCLUSION: To our knowledge, this is the first study to examine the association between aortic arch branching patterns and incidence of intracranial aneurysm. No significant association was found between aortic arch branching pattern and the incidence of intracranial aneurysm.

Interventional Neuroradiology: A Review.

Interventional neuroradiology (INR) has evolved from a hybrid mixture of daring radiologists and iconoclastic neurosurgeons into a multidisciplinary specialty, which has become indispensable for cerebrovascular and neurological centers worldwide. This manuscript traces the origins of INR and describes its evolution to the present day. The focus will be on cerebrovascular disorders including aneurysms, stroke, brain arteriovenous malformations, dural arteriovenous fistulae, and atherosclerotic disease, both intra- and extracranial. Also discussed are cerebral vasospasm, venolymphatic malformations of the head and neck, tumor embolization, idiopathic intracranial hypertension, inferior petrosal venous sinus sampling for Cushing's disease, and spinal interventions. Pediatric INR has not been included and deserves a separate, dedicated review.

Effect of Self-Expanding Carotid Stents on Plaque Thickness and Vessel Diameter.

BACKGROUND: In vitro models have suggested that stents affect atherosclerotic plaques symmetrically because of their outward radial forces. We evaluated the effects of stents on carotid plaque and the arterial wall using carotid ultrasound in carotid stenting patients to see whether these effects were borne out in vivo. METHODS: From a carotid stent database, 30 consecutive patients were selected. All had carotid Doppler ultrasound performed pre- and poststenting. The diameters of the lumen at the level of stenotic plaque pre- and poststenting, the dorsal and ventral plaque thickness, and of the outer arterial wall diameter were measured. Plaque thickness was measured at the level of maximal stenosis. Nonparametric tests were used to determine whether the stent effect and luminal enlargement were based on wall remodeling or on total arterial expansion. RESULTS: The patients were followed for an average of 22 months. Eighteen patients were male, with an average age of 70 years. A total of 87% of patients were symptomatic ipsilateral to the side of stenosis. Nine patients had angioplasty intraprocedurally. The luminal diameter increased poststenting in the region of severe stenosis. Plaque thickness, both ventrally and dorsally, decreased poststenting, with no significant difference between the ventral and dorsal plaque effects. The outer arterial wall diameters did not change. The measured lumen in the stent increased over time poststenting. CONCLUSIONS: Self-expanding nitinol stents alter the baseline ventral and dorsal plaque to a significant degree and do not significantly affect the native arterial wall and the overall arterial diameter.

Micro-CT-compatible technique for measuring self-expanding stent forces.

PURPOSE: To develop and evaluate a technique for measuring the radial resistive force, chronic outward force, and dimensions of self-expanding stents. MATERIALS AND METHODS: A Mylar film was looped around the stent, threaded through two carbon fiber rods, and immersed in a 37 degrees C oil bath. A force gauge mounted on a micro-positioning stage was used to measure the applied forces. The apparatus containing the self-expanding nitinol stent (diameter, 40 mm; length, 80 mm) was placed inside a micro-computed tomographic (CT) scanner. At each stent deformation, the load was manually recorded from the force gauge and a micro-CT volume (isotropic voxel spacing, 0.15 mm) obtained. Stent diameter and length were measured from the images, and radial resistive force and chronic outward force were calculated for each deformation. RESULTS: The stress-strain curves indicate that the stents exert much smaller maximum outward forces (1.2 N/cm) than the force that is required to compress them (3.6 N/cm). The forces were measured with a precision of +/-3.3% (standard deviation of five repeated measurements). The stent's diameter was measured with precision better than 0.3% and accuracy of +/-0.1 mm. CONCLUSIONS: The authors have developed a radiographic technique that enables precise measurements of radial resistive force, chronic outward force, and the dimensions of self-expanding stents during deformation.

Cervical spine motion: a fluoroscopic comparison of the AirTraq Laryngoscope versus the Macintosh laryngoscope.

BACKGROUND: The optimal technique to intubate the trachea in patients presenting with a potential or documented cervical spine (C-spine) injury remains unresolved. Using continuous fluoroscopic video assessment, C-spine motion during laryngoscopy with an AirTraq Laryngoscope (King Medical Systems, Newark, DE) was compared to that with intubation using a Macintosh blade. METHODS: Twenty-four healthy surgical patients gave written consent to participate in a crossover randomized controlled trial; all patients were subjected to both Macintosh and AirTraq laryngoscopy with manual inline stabilization after induction of anesthesia. The C-spine motion was examined at four areas: the occiput-C1 junction, C1-C2 junction, C2-C5 motion segment, and C5-thoracic motion segment. The time required for laryngoscopy was also measured. RESULTS: C-spine motion using the AirTraq was less than that during Macintosh laryngoscopy, averaging 66% less (P < 0.01) at three of the motion segments studied, occiput-C1, C2-C5, and C5-thoracic. There was no difference at the C1-C2 segment. There was no significant difference in the time to accomplish laryngoscopy between the two devices. CONCLUSIONS: For patients in whom C-spine movement is undesirable, use of the AirTraq Laryngoscope may be useful to limit movement without an increase in the duration of intubation.

Hemodynamic instability during carotid artery stenting: the relative contribution of stent deployment versus balloon dilation.

OBJECT: Hemodynamic instability may complicate carotid angioplasty and stenting in up to 40% of patients. The authors have previously demonstrated that primary self-expanding stent placement alone can gradually dilate severely stenosed carotid arteries without the use of balloons. The authors hypothesized that eliminating the balloon would reduce carotid baroreceptor stimulation, thereby decreasing the incidence of hemodynamic instability. METHODS: Ninety-seven high surgical risk patients with symptomatic, severely stenosed carotid arteries were treated with the intention of using a self-expanding stent alone. Seventy-seven arteries (79%) were treated with stenting alone, and 20 required angioplasty (21%). RESULTS: Intraprocedural bradycardia (heart rate < 60 bpm) developed in 29 patients (38%) and hypotension (systolic blood pressure < 90 mm Hg) occurred in 1 patient (1%) treated with stenting alone. Fourteen patients (70%) who underwent angioplasty and stenting had bradycardia, and hypotension developed in 4 (20%). Atropine, glycopyrrolate, or vasopressors were required in 8% of patients who received stenting alone, compared to 30% of patients who underwent angioplasty. In the first 24 hours after treatment, hypotension or bradycardia developed in 25 patients (32%) who had undergone stent placement alone, and in 15 patients (75%) after stent placement and balloon angioplasty. There was no difference in the occurrence of intra- or postprocedural hypertension (systolic blood pressure > 160 mm Hg) between patients treated with stenting alone or stenting and balloons. Factors independently associated with hemodynamic depression included baseline heart rate and balloon use. CONCLUSIONS: Hemodynamic instability during and after carotid artery stenting was observed more frequently when balloon angioplasty was required than when stent placement was performed without concurrent balloon angioplasty.

Primary stenting for recurrent stenosis following carotid endarterectomy.

BACKGROUND: Carotid angioplasty and stenting is an accepted alternative treatment for severe restenosis following carotid endarterectomy. Balloons may not be required to effectively treat these lesions, given their altered histopathology compared to primary atherosclerotic plaque and tendency to be less calcified. Primary stenting using self-expanding stents alone may, therefore, be a safe and effective treatment for restenosis post-carotid endarterectomy. METHODS: We review our experience in the treatment of 12 patients with symptomatic severe restenosis following carotid endarterectomy with primary stent placement alone. RESULTS: Self-expanding stent placement alone reduced the mean internal carotid artery stenosis from 85% to 29%. Average peak systolic velocity determined at the time of ultrasonography decreased from 480 cm/s at initial presentation to 154 cm/s post-stent deployment and further decreased to 104 cm/s at one year follow-up. The stented arteries remained widely patent with no evidence of restenosis. A single peri-procedural ipsilateral transient ischemic event occurred. There were no cerebral or cardiac ischemic events recorded at one year of follow-up. CONCLUSIONS: In this series, primary stent placement without use of angioplasty balloons was a safe and effective treatment for symptomatic restenosis following carotid endarterectomy.

Direct carotid-cavernous fistula causing brainstem venous congestion.

A 39-year-old man who presented with unilateral proptosis and periocular pain rapidly developed reduced consciousness, facial numbness, dysarthria, and gait ataxia from a direct carotid-cavernous fistula (CCF) with drainage into posterior fossa veins. Brain MRI revealed abnormal signal throughout the brainstem, indicative of venous hypertension and edema. Closure of the fistula by detachable balloon eliminated the clinical and imaging abnormalities. This is the fifth reported case of brainstem complications of a direct CCF. It highlights potentially serious complications of this condition and their reversibility with prompt treatment.

Results using a self-expanding stent alone in the treatment of severe symptomatic carotid bifurcation stenosis.

OBJECT: Conventional endovascular therapy for carotid stenosis involves placement of an embolic protection device followed by stent insertion and angioplasty. A simpler approach may be placement of a stent alone. The authors determined how often this approach could be used to treat patients with carotid stenosis, and assessed which factors would preclude this approach. METHODS: Over a period of 6 years, 97 patients with symptomatic carotid stenosis were treated with the intention of using a "stent-only" approach. Arteries in 77 patients (79%) were treated with stents alone, 13 required preinsertion balloon dilation, 6 postinsertion dilation, and 1 both pre- and postinsertion dilation. RESULTS: The mean stenosis according to North American Symptomatic Carotid Endarterectomy Trial criteria was reduced from 82 to 40% in the stent-only group and from 89 to 37% in the stent and balloon angioplasty group. The 30-day stroke and death rate was 7.2%. Patients were followed for a mean of 15 months. In the stent-alone group, the mean preoperative Doppler peak systolic velocity (PSV) was 409 cm/second, with an internal carotid artery/common carotid artery (ICA/CCA) ratio of 7.2. At follow-up review, the PSV decreased to 153 cm/second and the ICA/CCA ratio to 2.1. In the angioplasty group the mean preoperative PSV was 496 cm/second and the ICA/CCA ratio was 9.2, decreasing to 163 cm/second and 2, respectfully, at follow-up evaluation. Restenosis occurred in 12.8% of patients at 6 months and in 15.9% at 1 year. One stroke occurred during the follow-up period in each group. Using multivariable analysis, factors precluding the "stent-only" approach were as follows: severity of stenosis, circumferential calcification, and no history of hyperlipidemia. CONCLUSIONS: Balloons may not be required to treat all patients with carotid stenosis. A stent alone was feasible in 79% of patients, and 79% of patients were alive and free from ipsilateral stroke or restenosis at 1 year. Restenosis rates with this approach are higher than with conventional angioplasty and stent insertion. Carotid arteries with very severe stenoses (> 90%) and circumferential calcification may be more successfully treated with angioplasty combined with stent placement.