Stenting for Traumatic Pseudoaneurysms of the Cervical Internal Carotid Artery: Case Report and Systematic Review

BACKGROUND

The optimal stenting approach for traumatic pseudoaneurysms (PSA) of the extracranial internal carotid artery (ICA) remains underinvestigated. We present a case of a traumatic pseudoaneurysm of the extracranial ICA managed with stenting and review of prior published similar cases.

METHODS

The systematic review followed PRISMA-S guidelines and included studies that investigated traumatic pseudoaneurysms of the extracranial ICA managed by stent placement. Statistical analysis assessed the association between the type of injury and stent type, dual antiplatelet therapy (DAPT) duration, and clinical presentation, and the association between stent type and DAPT duration.

RESULTS

Our search yielded 82 publications with 135 patients with extracranial ICA PSA treated with stenting. The odds of neck hematoma presentation was 12.2 times greater for patients with penetrating rather than blunt injuries (P = 0.000002). Covered stents had 2.02 times higher odds of use for penetrating rather than blunt injuries compared to bare metal stents. (P = 0.0029). Shorter duration DAPT was seen with bare metal stents having 1.25 higher odds of DAPT duration less than one month compared to covered (P = 0.001).

CONCLUSIONS

In traumatic extracranial ICA pseudoaneurysms, covered stents are used more commonly for penetrating injuries compared to blunt injuries. Penetrating injuries are more strongly associated with the presentation of a hematoma compared to blunt injuries. Stent type may influence the recommended DAPT duration. Surgeons should consider these findings when selecting stent type and DAPT duration with patients presenting with traumatic extracranial ICA pseudoaneurysm.

Arteriovenous malformation presenting as complex regional pain syndrome: illustrative case

BACKGROUND

Complex regional pain syndrome (CRPS) is typically described as a peripheral nerve disorder in which exaggerated allodynia and hyperalgesia follow a minor injury. Some researchers propose a central mechanism, although current evidence is lacking.

OBSERVATIONS

A 14-year-old female presented with classic CRPS symptoms of left upper-extremity weakness and hyperalgesia after a bout of sharp pain in her thumb while shoveling snow. A possible seizure prompted magnetic resonance imaging, revealing a right frontal Spetzler-Martin grade II arteriovenous malformation (AVM) adjacent to the primary motor cortex. Brodmann areas 1, 3a, and 3b, which are responsible for localizing and processing burning and painful sensations, were also involved. The patient underwent transarterial Onyx embolization in two sessions and microsurgical resection, after which her CRPS symptoms completely resolved.

LESSONS

To our knowledge, this is the first reported case of a cerebral AVM presenting as CRPS, which supports a central mechanism. The authors propose that rapid growth of the AVM led to a vascular steal phenomenon of surrounding parenchyma, which disrupted the patient's normal motor function and nociceptive processing. Further validation in other series is needed.

Cerebral arterial vasospasm complicating supratentorial meningioma resection: illustrative cases

BACKGROUND

Cerebral arterial vasospasm is a rare complication after supratentorial meningioma resection. The pathophysiology of this condition may be similar to vasospasm after aneurysmal subarachnoid hemorrhage, and treatment options may be similar.

OBSERVATIONS

The authors present two cases of cerebral vasospasm after supratentorial meningioma resection and perform a systematic literature review of similar cases.

LESSONS

Cerebral arterial vasospasm after supratentorial meningioma resection may be associated with significant morbidity due to cerebral ischemia if not addressed in a timely manner. Treatment paradigms may be adopted from the management of arterial vasospasm associated with subarachnoid hemorrhage.

Effect of Stent Porosity, Platelet Function Test Usage, and Dual Antiplatelet Therapy Duration on Clinical and Radiographic Outcomes After Stenting for Cerebral Aneurysms: A Meta-Analysis

BACKGROUND

The use of stents with various porosities for treating cerebral aneurysms requires dual antiplatelet therapy (DAPT) without clear guidelines on the utility of platelet function tests (PFTs) and the duration of DAPT. We sought to determine the effects of stent porosity, PFT usage, and DAPT duration on the radiographic and clinical outcomes after stenting of cerebral aneurysms.

METHODS

PubMed was searched on March 29, 2021 for studies of cerebral aneurysm stenting that had specified the stent type and DAPT duration. A random effects meta-analysis was used to measure the prevalence of nonprocedural thrombotic and hemorrhagic events, clinical outcomes, aneurysm occlusion, and in-stent stenosis stratified by stent porosity, PFT usage, and DAPT duration.

RESULTS

The review yielded 105 studies (89 retrospective and 16 prospective) with 117 stenting cohorts (50 high porosity, 17 intermediate porosity, and 50 low porosity). In the high-, intermediate-, and low-porosity stenting cohorts, PFT usage was 26.0%, 47.1%, and 62.0% and the mean DAPT duration was 3.51 ± 2.33, 3.97 ± 1.92, and 5.18 ± 2.27 months, respectively. The intermediate-porosity stents showed a reduced incidence of hemorrhagic events (π = 0.32%) compared with low-porosity stents (π = 1.36%; P = 0.01) and improved aneurysm occlusion (π = 6.18%) compared with high-porosity stents (π = 14.42%; P = 0.001) and low-porosity stents (π = 11.71%; P = 0.04). The prevalence of in-stent stenosis was lower for the intermediate-porosity (π = 0.57%) and high-porosity (π = 1.51%) stents than for the low-porosity stents (π = 3.30%; P < 0.05). PFT use had resulted in fewer poor clinical outcomes (π = 3.54%) compared with those without PFT use (π = 5.94%; P = 0.04). The DAPT duration had no effect on the outcomes.

CONCLUSIONS

In the present meta-analysis, which had selected for studies of cerebral aneurysm stenting that had reported the DAPT duration, intermediate-porosity stents and PFT use had resulted significantly improved outcomes. No effect of DAPT duration could be detected.

Destructive strategies in treating cerebrovascular pathology: Review and treatment algorithm

The goal of cerebrovascular pathology treatment is most often to angiographically eradicate a lesion with the lowest probability of morbidity. Destructive strategies using parent vessel occlusion are less commonly considered in the modern era. We review principles of parent vessel occlusion for treatment of cerebrovascular pathology and select cases to demonstrate these principles. Many common cerebrovascular conditions have been safely and effectively treated with destructive strategies including intracranial aneurysms, traumatic craniocervical vascular injuries, and oncologic indications such as carotid blowout. Avoiding procedural morbidity in these procedures involves assessment of collaterals distal to a planned parent vessel occlusion, determination of this arterial segment's eloquence, prevention of distal migration of endovascular devices or thrombus, and prevention of stump emboli. An algorithm for case selection and method of destructive technique versus a reconstructive approach can be used. Destructive strategies for treating cerebrovascular pathology are still relevant and can be applied safely in appropriately selected cases.

Comparison of transarterial n-BCA and Onyx embolization of brain arteriovenous malformations: A single-center 18-year retrospective analysis

OBJECTIVE

Brain arteriovenous malformations (AVM) are commonly treated with endovascular embolization. Due to the rapid evolution of endovascular technology and lack of consistent practice guidelines regarding AVM embolization, further study of AVM embolization outcomes is warranted.

METHODS

We conducted a retrospective review of AVMs embolized at a single center from 2002-2019. Patient demographics, AVM characteristics, intention of embolization, and angiographic and clinical outcome after embolization were recorded. We compared the embolization results of those treated with n-butyl cyanoacrylate (n-BCA) and Onyx.

RESULTS

Over an 18-year period at our institution, 30 (33%) of 92 AVMs were treated with embolization. n-BCA was used in 12 cases and Onyx in 18 cases. Eighty-seven pedicles were embolized over 47 embolization sessions. Fifty percent of AVMs treated with n-BCA underwent more than one embolization session compared to 22% when Onyx was used. The median total percent volume reduction in the n-BCA AVMs was 52% compared to 51% in Onyx AVMs. There were 2 periprocedural complications in the n-BCA cohort and none in the Onyx cohort.

CONCLUSIONS

In this small retrospective series, Onyx and n-BCA achieved similar occlusion results, although n-BCA required more sessions and pedicles embolized to do so.

Angioarchitectural features amongst patients with unruptured brain arteriovenous malformations presenting with headache: findings from a single center retrospective review of 76 patients

Background

Brain arteriovenous malformations (AVMs) consist of abnormal connections between arteries and veins via an interposing nidus. While hemorrhage is the most common presentation, unruptured AVMs can present with headaches, seizures, neurological deficits, or be found incidentally. It remains unclear as to what AVM characteristics contribute to pain generation amongst unruptured AVM patients with headaches.

Methods

To assess this relationship, the current study evaluates angiographic and clinical features amongst patients with unruptured brain AVMs presenting with headache. Loyola University Medical Center medical records were queried for diagnostic codes corresponding to AVMs. In patients with unruptured AVMs, we analyzed the correlation between the presenting symptom of headache and various demographic and angiographic features.

Results

Of the 144 AVMs treated at our institution between 1980 and 2017, 76 were unruptured and had sufficient clinical data available. Twenty-three presented with headaches, while 53 patients had other presenting symptoms. Patients presenting with headache were less likely to have venous stenosis compared to those with a non-headache presentation (13 % vs. 36 %, p = 0.044).

Conclusions

Our study suggests that the absence of venous stenosis may contribute to headache symptomatology. This serves as a basis for further study of correlations between AVM angioarchitecture and symptomatology to direct headache management in AVM patients.

Endovascular catheter manometry reliability: a benchtop validation study

OBJECTIVE

Catheter manometry is used frequently in neuroendovascular surgery for assessing cerebrovascular pathology. The accuracy of pressure data with different catheter setups requires further validation.

METHODS

In a silicone human vascular model with a pulsatile pump, pressure measurements were taken through multiple arrangements of 2 guide catheters and 6 microcatheters. The systolic pressure, diastolic pressure, mean pressure, pulse pressure, and area under the curve of the waveform were recorded through catheters with controls at arterial blood pressure ranges. Linear regression modeling was performed, correlating transduction area and relative pulse pressure. Thresholds for acceptable accuracy were ≥ 90%.

RESULTS

Mean pressure demonstrated < 4% variation between all 24 catheter setups and respective controls. A strong linear correlation (r2 = 0.843, p < 0.0005) between microcatheter transduction area and relative pulse pressure with a threshold of 0.50 mm2 was seen (i.e., 0.031-inch inner diameter [ID]). For guide catheters with indwelling microcatheters, there was also a strong linear correlation (r2 = 0.840, p < 0.0005) of transduction area to pulse pressure. The guide catheters with obstructing microcatheters required a transduction area over fourfold higher compared with unobstructed microcatheters (2.21 mm2 vs 0.50 mm2).

CONCLUSIONS

Mean pressure measurements are accurate through microcatheters as small as 0.013-inch ID. Pulse pressure and waveform morphology may require a microcatheter ≥ 0.031-inch ID to achieve 90% accuracy, although the 0.027-inch ID microcatheter reached 85% accuracy. A 0.070-inch guide catheter with a microcatheter ≤ 0.042-inch outer diameter (e.g., Marksman 0.027-inch ID or smaller) allows accurate transduction of pulse pressure. Further validation of these benchtop findings is necessary before application in a clinical setting.

Machine learning models improve prediction of large vessel occlusion and mechanical thrombectomy candidacy in acute ischemic stroke

BACKGROUND AND PURPOSE

Early identification of large vessel occlusions (LVO) and timely recanalization are paramount to improved clinical outcomes in acute ischemic stroke. A stroke assessment that maximizes sensitivity and specificity for LVOs is needed to identify these cases and not overburden the health system with unnecessary transfers. Machine learning techniques are being used for predictive modeling in many aspects of stroke care and may have potential in predicting LVO presence and mechanical thrombectomy (MT) candidacy.

METHODS

Ischemic stroke patients treated at Loyola University Medical Center from July 2018 to June 2019 (N = 286) were included. Thirty-five clinical and demographic variables were analyzed using machine learning algorithms, including logistic regression, extreme gradient boosting, random forest (RF), and decision trees to build models predictive of LVO presence and MT candidacy by area of the curve (AUC) analysis. The best performing model was compared with prior stroke scales.

RESULTS

When using all 35 variables, RF best predicted LVO presence (AUC = 0.907 ± 0.856-0.957) while logistic regression best predicted MT candidacy (AUC = 0.930 ± 0.886-0.974). When compact models were evaluated, a 10-feature RF model best predicted LVO (AUC = 0.841 ± 0.778-0.904) and an 8-feature RF model best predicted MT candidacy (AUC = 0.862 ± 0.782-0.942). The compact RF models had sensitivity, specificity, negative predictive value and positive predictive value of 0.81, 0.87, 0.92, 0.72 for LVO and 0.87, 0.97, 0.97, 0.86 for MT, respectively. The 10-feature RF model was superior at predicting LVO to all previous stroke scales (AUC 0.944 vs 0.759-0.878) and the 8-feature RF model was superior at predicting MT (AUC 0.970 vs 0.746-0.834).

CONCLUSION

Random forest machine learning models utilizing clinical and demographic variables predicts LVO presence and MT candidacy with a high degree of accuracy in an ischemic stroke cohort. Further validation of this strategy for triage of stroke patients requires prospective and external validation.

Coaxial Access for Microcatheter Stabilization During Aneurysm Coiling: 2-Dimensional Operative Video

Coaxial support is a fundamental technique utilized by neurointerventionalists to optimize distal catheter control within the intracranial circulation. Here we present a 41-yr-old woman with a previously coiled ruptured anterior communicating artery aneurysm with progressive recurrence harboring tortuous internal carotid anatomy to demonstrate the utility of coaxial support. Raymond-Roy classification of initial aneurysm coiling of class 1 resulted as class 3b over the 21 mo from initial treatment.1 The patient consented to stent-assisted coiling for retreatment of this aneurysm. Coaxial support was advanced as distally as possible in the proximal vasculature to improve catheter control, reducing dead space within which the microcatheter could move, decreasing angulations within proximal vasculature, limiting the movement of the native vessels, and providing a surface of lower friction than the endothelium. As the risk of recurrent subarachnoid hemorrhage in previously treated coiled aneurysms approaches 3%, retreatment occurs in 16.4% within 6 yr2 and in 17.4% of patients within 10 yr.3 Rerupture is slightly higher in patients who underwent coiling vs clipping, with the rerupture risk inversely proportional to the degree of aneurysm occlusion,4 further substantiating that coaxial support provides technical advantage in selected patients where additional microcatheter control is necessary for optimal occlusion. Pitfalls of this technique include vasospasm and vascular injury, which can be ameliorated by pretreatment of the circulation with vasodilators to prevent catheter-induced vasospasm. This case and model demonstration illustrates the technique of coaxial access in the stent-assisted coiling of a recurrent anterior communicating artery aneurysm and identification and management of catheter-induced vasospasm.

Reliability of the Modified TICI Score among Endovascular Neurosurgeons

BACKGROUND AND PURPOSE

The modified TICI score is the benchmark for quantifying reperfusion after mechanical thrombectomy. There has been limited investigation into the reliability of this score. We aim to identify intra-rater and inter-rater reliability of the mTICI score among endovascular neurosurgeons.

MATERIALS AND METHODS

Four independent endovascular neurosurgeons (raters) reviewed angiograms of 67 patients at 2 time points. κ statistics assessed inter- and intrarater reliability and compared raters'-versus-proceduralists' scores. Reliability was also assessed for occlusion location and by dichotomizing modified TICI scores (0-2a versus 2b-3).

RESULTS

Interrater reliability was moderate-to-substantial, weighted κ = 0.417-0.703, overall κ = 0.374 (P < .001). The dichotomized modified TICI score had moderate-to-substantial interrater agreement, κ statistics = 0.468-0.715, overall κ = 0.582 (P < .001). Intrarater reliability was moderate-to-almost perfect, weighted κ = 0.594-0.81. The dichotomized modified TICI score had substantial-to-almost perfect reliability, κ = 0.632-0.82. Proceduralists had fair-to-moderate agreement with raters, weighted κ = 0.348-0.574, and the dichotomized modified TICI score had fair-to-moderate agreement, κ = 0.365-0.544. When proceduralists and raters disagreed, proceduralists' scores were higher in 79.6% of cases. M1 followed by ICA occlusions had the highest agreement.

CONCLUSIONS

The modified TICI score is a practical metric for assessing reperfusion after mechanical thrombectomy, though not without limitations. Agreement improved when scores were dichotomized around the clinically relevant threshold of successful revascularization. Interrater reliability improved with time, suggesting that formal training of interventionalists may improve reporting reliability. Agreement of the modified TICI scale is best with M1 and ICA occlusion and becomes less reliable with more distal or posterior circulation occlusions. These findings should be considered when developing research trials.

'Railroad switch' technique for stent-assisted coil embolization of a wide-neck bifurcation intracranial aneurysm: technical note

Preservation of the posterior cerebral arteries during endovascular treatment of wide-neck basilar bifurcation aneurysms remains a technical challenge despite recent device innovations. We present a novel stent deployment technique, the 'railroad switch', to protect both posterior cerebral arteries during treatment of a recurrent basilar bifurcation aneurysm. Following asymmetric basilar-posterior cerebral artery stent deployment, favoring distal placement in a posterior cerebral artery, advancement of a jailed microcatheter will advance the proximal stent into the aneurysm, protecting both posterior cerebral arteries and the native basilar terminus. This novel maneuver offers interventionalists another application of commonly used intracranial stents for endovascular management of complex basilar bifurcation aneurysms.

Murphey's teat: history and insight into an enigmatic cerebrovascular eponym

Dr. Francis Murphey of the Semmes-Murphey Clinic in Memphis recognized that a focal sacculation on the dome of an aneurysm may be angiographic evidence of a culpable aneurysm in the setting of subarachnoid hemorrhage with multiple intracranial aneurysms present. This has been referred to as a Murphey's "teat," "tit," or "excrescence." With variability in terminology, misspellings in the literature, and the fact that Dr. Murphey did not formally publish this important work, the authors sought to clarify the meaning and investigate the origins of this enigmatic cerebrovascular eponym.

Extracranial-to-Intracranial Bypass for Pressor Dependent Cerebrovascular Insufficiency: Modified Classification and Representative Case

BACKGROUND

While some randomized clinical trials have reduced the indications for cerebral revascularization in the secondary prevention of ischemic stroke, a distinct subset of patients with blood pressure augmentation dependent cerebrovascular insufficiency due to large vessel occlusions remains unaddressed. With the recent paradigm shifts in acute ischemic stroke care, the role of extracranial to intracranial (EC-IC) bypass must be re-addressed when endovascular intervention is not a feasible option. We submit a refined classification of cerebrovascular insufficiency with a category called Pressor-Dependent Cerebrovascular Insufficiency (PD-CVI) for whom EC-IC bypass may be indicated.

CLINICAL PRESENTATION

A 61-year-old female former smoker presented with one day of intermittent left faciobrachial weakness and was found to have middle cerebral artery and cervical internal carotid artery occlusions. On admission to the intensive care unit, she was found to have PD-CVI with an intravenous pressor dependent blood pressure threshold over which she had near resolution of her neurological deficits. With endovascular intervention precluded given the ICA occlusion, she underwent an urgent right sided EC-IC bypass. The procedure was without complication, with careful attention to maintaining hypertension perioperatively. She required no pressors postoperatively and was neurologically intact at three months post-operatively.

CONCLUSION

With recent advances in acute ischemic stroke care, there remains a need for careful consideration of cerebral revascularization surgery in patients with evidence of PD-CVI who may be precluded from or failed endovascular intervention.

Abstract TP217: Intra-arterial Verapamil Can Help Differentiate Reversible From Non-reversible Vasculopathy

Introduction: Cerebral angiography (DSA) is commonly used to characterize small vessel vasculopathy, yet it is difficult to establish etiology by angiographic patterns alone.

Hypothesis: Responsiveness to intra-arterial verapamil (IA-V) can help differentiate etiology of small vessel vasculopathy by characterizing it as reversible or non-reversible.

Methods: We performed a retrospective analysis from 2013-15 of patients referred for DSA to evaluate cerebral vasculopathy. We characterized symptoms, radiographic findings, angiographic pattern and responsiveness to IA-V, if given, as well as biopsy and follow-up angiography.

Results: Thirty-three patients were identified (70% female; mean age 47.7). Presenting symptoms were headache (48%), focal neurologic deficit (45%), cognitive impairment (30%) and seizure (18%). Three patients presented in the post-partum period. Radiographic findings included infarct (42%), cortical subarachnoid hemorrhage (33%) and cerebral edema (3%). Arteriopathy was present on DSA in 19 of 33 patients (58%). Twelve patients had smooth segmental narrowing, 6 had irregular narrowing, 1 had diffuse narrowing. IA-V was administered in 12 of the 19 patients with arteriopathy (63%), including 9 of 12 with smooth segmental, 2 of 6 with irregular, and the patient with diffuse narrowing. Of 9 patients with smooth segment narrowing that received IA-V, 8 exhibited a vasodilatory response (89%). In 1 of these patients, superficial temporal artery biopsy was normal. Follow-up DSA was performed in 4 of the 8 patients with verapamil-responsive arteriopathy at a median time of 86 days. All 4 had angiographic resolution of their arteriopathy, consistent with reversible cerebral vasoconstriction syndrome. The 3 patients with irregular or diffuse narrowing who received IA-V did not exhibit vasodilatory response or have follow-up angiography. In 3 patients with irregular narrowing, brain biopsy was performed; 1 revealed CNS vasculitis, 2 were normal, consistent with atherosclerosis.

Conclusion: Our series is consistent with reports of patients with reversible vasculopathy exhibiting a response to IA vasodilators. Response to IA-V may better characterize small vessel vasculopathy than angiographic pattern alone.

Aneurysm growth and de novo aneurysms during aneurysm surveillance

OBJECTIVE Many low-risk unruptured intracranial aneurysms (UIAs) are followed for growth with surveillance imaging. Growth of UIAs likely increases the risk of rupture. The incidence and risk factors of UIA growth or de novo aneurysm formation require further research. The authors retrospectively identify risk factors and annual risk for UIA growth or de novo aneurysm formation in an aneurysm surveillance protocol. METHODS Over an 11.5-year period, the authors recommended surveillance imaging to 192 patients with 234 UIAs. The incidence of UIA growth and de novo aneurysm formation was assessed. With logistic regression, risk factors for UIA growth or de novo aneurysm formation and patient compliance with the surveillance protocol was assessed. RESULTS During 621 patient-years of follow-up, the incidence of aneurysm growth or de novo aneurysm formation was 5.0%/patient-year. At the 6-month examination, 5.2% of patients had aneurysm growth and 4.3% of aneurysms had grown. Four de novo aneurysms formed (0.64%/patient-year). Over 793 aneurysm-years of follow-up, the annual risk of aneurysm growth was 3.7%. Only initial aneurysm size predicted aneurysm growth (UIA < 5 mm = 1.6% vs UIA ≥ 5 mm = 8.7%, p = 0.002). Patients with growing UIAs were more likely to also have de novo aneurysms (p = 0.01). Patient compliance with this protocol was 65%, with younger age predictive of better compliance (p = 0.01). CONCLUSIONS Observation of low-risk UIAs with surveillance imaging can be implemented safely with good adherence. Aneurysm size is the only predictor of future growth. More frequent (semiannual) surveillance imaging for newly diagnosed UIAs and UIAs ≥ 5 mm is warranted.

Factors Determining Surgical Approaches to Basilar Bifurcation Aneurysms and Its Surgical Outcomes

BACKGROUND:

The basilar bifurcation aneurysm (BBA) is still considered to be one of the most challenging aneurysms for micro- and endovascular surgery. Classic surgical approaches, such as subtemporal, lateral supraorbital (LSO), and modified presigmoid, are still reliable and effective.

OBJECTIVE:

To analyze the clinical and radiological factors that affect the selection of these classic surgical approaches and their outcomes.

METHODS:

A retrospective analysis was conducted on the clinical and radiological data from computed tomographic angiography of BBA that have been clipped in the Department of Neurosurgery of Helsinki University Central Hospital between 2004 and 2014. Statistical analyses were performed using parametric and nonparametric tests where values were considered significant below P = .05.

RESULTS:

One hundred four patients with BBA underwent surgical clipping in our department between 2004 and 2014. Eight patients were excluded from the study because of incomplete preoperative radiological evaluations, leaving 96 patients for further analysis. Multiple aneurysm clipping, mean basilar bifurcation angle, and aneurysm neck distance from posterior clinoid process were shown to be factors that determine the surgical approach. Unfavorable outcome is strongly associated with poor Hunt-Hess grade on admission, distance from aneurysm neck (the posterior clinoid process), thrombosis, and dome size.

CONCLUSION:

Microsurgery for BBA clipping can be performed safely with simple surgical approaches: subtemporal and LSO. There are several factors determining the approach selected. Poor patient outcome in BBA was highly associated with poor preoperative clinical grade and large size of aneurysm dome.

Aneurysmal subarachnoid hemorrhage: pathobiology, current treatment and future directions

Aneurysmal subarachnoid hemorrhage is the most devastating form of stroke. Many pathological mechanisms ensue after cerebral aneurysm rupture, including hydrocephalus, apoptosis of endothelial cells and neurons, cerebral edema, loss of blood-brain barrier, abnormal cerebral autoregulation, microthrombosis, cortical spreading depolarization and macrovascular vasospasm. Although studied extensively through experimental and clinical trials, current treatment guidelines to prevent delayed cerebral ischemia is limited to oral nimodipine, maintenance of euvolemia, induction of hypertension if ischemic signs occur and endovascular therapy for patients with continued ischemia after induced hypertension. Future investigations will involve agents targeting vasodilation, anticoagulation, inhibition of apoptosis pathways, free radical neutralization, suppression of cortical spreading depolarization and attenuation of inflammation.

Prediction and suppression of HIFU-induced vessel rupture using passive cavitation detection in an ex vivo model

Background

Occlusion of blood vessels using high-intensity focused ultrasound (HIFU) is a potential treatment for arteriovenous malformations and other neurovascular disorders. However, attempting HIFU-induced vessel occlusion can also cause vessel rupture, resulting in hemorrhage. Possible rupture mechanisms include mechanical effects of acoustic cavitation and heating of the vessel wall.

Methods

HIFU exposures were performed on 18 ex vivo porcine femoral arteries with simultaneous passive cavitation detection. Vessels were insonified by a 3.3-MHz focused source with spatial-peak, temporal-peak focal intensity of 15,690–24,430 W/cm² (peak negative-pressure range 10.92–12.52 MPa) and a 50% duty cycle for durations up to 5 min. Time-dependent acoustic emissions were recorded by an unfocused passive cavitation detector and quantified within low-frequency (10–30 kHz), broadband (0.3–1.1 MHz), and subharmonic (1.65 MHz) bands. Vessel rupture was detected by inline metering of saline flow, recorded throughout each treatment. Recorded emissions were grouped into ‘pre-rupture’ (0–10 s prior to measured point of vessel rupture) and ‘intact-vessel’ (>10 s prior to measured point of vessel rupture) emissions. Receiver operating characteristic curve analysis was used to assess the ability of emissions within each frequency band to predict vessel rupture.

Based on these measurements associating acoustic emissions with vessel rupture, a real-time feedback control module was implemented to monitor acoustic emissions during HIFU treatment and adjust the ultrasound intensity, with the goal of maximizing acoustic power delivered to the vessel while avoiding rupture. This feedback control approach was tested on 10 paired HIFU exposures of porcine femoral and subclavian arteries, in which the focal intensity was stepwise increased from 9,117 W/cm² spatial-peak temporal-peak (SPTP) to a maximum of 21,980 W/cm², with power modulated based on the measured subharmonic emission amplitude. Time to rupture was compared between these feedback-controlled trials and paired controller-inactive trials using a paired Wilcoxon signed-rank test.

Results

Subharmonic emissions were found to be the most predictive of vessel rupture (areas under the receiver operating characteristic curve (AUROC) = 0.757, p < 10^-16) compared to low-frequency (AUROC = 0.657, p < 10^-11) and broadband (AUROC = 0.729, p < 10^-16) emissions. An independent-sample t test comparing pre-rupture to intact-vessel emissions revealed a statistically significant difference between the two groups for broadband and subharmonic emissions (p < 10^-3), but not for low-frequency emissions (p = 0.058).

In a one-sided paired Wilcoxon signed-rank test, activation of the control module was shown to increase the time to vessel rupture (T_- = 8, p = 0.0244, N = 10). In one-sided paired t tests, activation of the control module was shown to cause no significant difference in time-averaged focal intensity (t = 0.362, p = 0.363, N = 10), but was shown to cause delivery of significantly greater total acoustic energy (t = 2.037, p = 0.0361, N = 10).

Conclusions

These results suggest that acoustic cavitation plays an important role in HIFU-induced vessel rupture. In HIFU treatments for vessel occlusion, passive monitoring of acoustic emissions may be useful in avoiding hemorrhage due to vessel rupture, as shown in the rupture suppression experiments.

Changes in computed tomography perfusion parameters after superficial temporal artery to middle cerebral artery bypass: an analysis of 29 cases

Introduction Analysis of computed tomography perfusion (CTP) studies before and after superficial temporal artery to middle cerebral artery (STA-MCA) bypass is warranted to better understand cerebral steno-occlusive pathology. Methods Retrospective review was performed of STA-MCA bypass patients with steno-occlusive disease with CTP before and after surgery. CTP parameters were evaluated for change after STA-MCA bypass. Results A total of 29 hemispheres were bypassed in 23 patients. After STA-MCA bypass, mean transit time (MTT) and time to peak (TTP) improved. When analyzed as a ratio to the contralateral hemisphere, MTT, TTP, and cerebral blood flow (CBF) improved. There was no effect of gender, double vessel versus single vessel bypass, or time until postoperative CTP study to changes in CTP parameters after bypass. Conclusions Blood flow augmentation after STA-MCA bypass may best be assessed by CTP using baseline MTT or TTP and ratios of MTT, TTP, or CBF to the contralateral hemisphere. The failure of cerebrovascular reserve to improve after cerebral bypass may indicate irreversible loss of autoregulation with chronic cerebral vasodilation or the inability of CTP to detect these improvements.

The Role of Endovascular Therapy in the Treatment of Acute Ischemic Stroke

Of the approximately 795 000 strokes in the United States annually, 87% are ischemic and result in significant morbidity and mortality. Improvements in acute ischemic stroke (AIS) outcomes have been achieved with intravenous thrombolytics (IVT) and intra-arterial thrombolytics vs supportive medical therapy. Given its ease of administration, noninvasiveness, and most validated efficacy, IVT is the standard of care in AIS patients without contraindications to systemic fibrinolysis. However, patients with large-vessel occlusions respond poorly to IVT. Recent trials designed to select this population for randomization to IVT vs IVT with adjunctive endovascular therapy have not shown improvement in clinical outcomes with endovascular therapy. This could be due to the lack of utilization of modern thrombectomy devices such as Penumbra aspiration devices, Solitaire stent-trievers, or Trevo stent-trievers, which have shown the best recanalization results. Continued improvement in the techniques with using these devices as well as randomized controlled trials using them is warranted. This article defines the goals of AIS revascularization, presents the evolution of treatment from the initial use of IVT to modern thrombectomy devices, and discusses current treatment and ongoing AIS trials.

Lumbar ligamentum flavum: spatial relationships to surrounding anatomical structures and technical description of en bloc resection

BACKGROUND

One structure, the ligamentum flavum, nearly always encountered in lumbar spinal operations, has not been examined as an important anatomical landmark. In this context, we describe its relevance in corridors of small surgical exposures created by minimally invasive spinal approaches.

MATERIAL AND METHODS

In cadaveric and intraoperative dissections, we introduce a systematic technique for resection of this ligament and clarify its anatomical relationships with the exiting nerve roots, pedicles, facet capsule, and midline epidural fat. Fixed human cadaveric spines were harvested en bloc to maintain the lower thoracic to sacral segments. A single coronal cut through the anterior portion of the pedicles ensured that the dorsal elements were intact. Viewed from the operative microscope, photographs depict the ligamentum flavum at various intraoperative steps.

RESULTS

The ligamentum flavum can undergo safe en bloc sequential resection that widely exposes the disc space for discectomy and interbody fusion. Its superolateral and inferolateral attachments are identifiable landmarks, effective in locating the exiting nerve roots. Corners of the L4-L5 ligamentum flavum mark the axillae of the exiting nerve roots (i.e., its superolateral corner marks the axilla of the L4 nerve roots, and its inferolateral corner marks the shoulder of the L5 nerve roots).

CONCLUSION

Our cadaveric and microscopic surgical dissections show the ligamentum flavum as seen in the new corridors of small surgical exposures during minimally invasive surgeries of the lumbar spine. Identifying this landmark, surgeons can envision the location of the nerve roots to help prevent their injury.

Systemic infusion and local irrigation with argatroban effective in preventing clot formation during carotid endarterectomy in a patient with heparin-induced thrombocytopenia

BACKGROUND

A therapeutic dilemma exists when patients with symptomatic carotid stenosis and concomitant heparin-induced thrombocytopenia (HIT) are advised to urgently undergo carotid endarterectomy (CEA) with heparin therapy.

METHODS

After a 63-year-old man with HIT and multiple medical comorbidities underwent emergent coronary artery bypass grafting, postoperative imaging revealed plaque at the origin of the left internal carotid artery with 80%-99% stenosis and minimal contralateral internal carotid artery disease. During the patient's evaluation to undergo CEA for symptomatic high-grade carotid stenosis, enzyme-linked immunosorbent assay revealed persistent platelet factor 4 antibodies.

RESULTS

The endarterectomy was successfully performed while the patient received argatroban, both as a continuous infusion and intermittent irrigation during dissection of the plaque. Postoperatively, the drip was continued for 24 hours, and the patient was discharged day 2 on a daily dose of 325 mg of aspirin. At the 6-month examination, Doppler ultrasound revealed normal anterograde velocities with no evidence of stenosis, and the patient noted no subsequent ischemic events.

CONCLUSIONS

We now recommend systemic intravenous and local argatroban irrigation to prevent thromboembolic complications in CEA cases with HIT and renal insufficiency. Bivalirudin for both systemic intravenous use and local irrigation may be safer in patients without renal insufficiency because of its shorter half-life.