Joseph C. Serrone

Venous thromboembolism in subarachnoid hemorrhage.

OBJECTIVE Venous thrombembolism is a significant cause of mortality in patients after subarachnoid hemorrhage (SAH). After screening a cohort of SAH for this complication, we proposed a refinement for risk stratification of venous thromboembolism. METHODS Our retrospective study included patients admitted to our academic medical center (2005-2007) for SAH from ruptured aneurysm and having survived beyond 72 hours. The 196 patients then underwent screening (i.e., duplex scans of the lower extremities) for deep vein thrombosis (DVT). Ultrasound scans were obtained when there was a clinical suspicion of DVT. Patient demographics and clinical variables were assessed as risk factors for DVT by logistic regression analysis. RESULTS Among 196 patients, the incidence of DVT was 9.7% and pulmonary embolism was 2%. In univariate analysis, factors significantly associated with DVT were absence of tobacco smoking, black race, male gender, poor admission Glasgow Coma Scale or World Federation of Neurological Surgeons grading scale for SAH, tall height, long hospital stay, and heavier body weight (P< 0.05). In multivariate analysis, only smoking, race, and length of stay were significant independent predictors of DVT. Aneurysm securing method and hypertension had no association with DVT. CONCLUSIONS Finding our SAH patients to be the largest group screened for DVT on the basis of our literature review, we confirmed many known risk factors for DVT and observed that smokers who abruptly quit lowered their risk of DVT. Our findings may be used for risk stratification when determining DVT chemoprophylaxis after SAH.

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.

The potential applications of high-intensity focused ultrasound (HIFU) in vascular neurosurgery.

This review assesses the feasibilty of high-intensity focused ultrasound (HIFU) in neurosurgical applications, specifically occlusion of intact blood vessels. Fourteen articles were examined. In summary, MRI was effective for HIFU guidance whereas MR angiography assessed vessel occlusion. Several studies noted immediate occlusion of blood vessels with HIFU. Long-term data, though scarce, indicated a trend of vessel recanalization and return to pre-treatment diameters. Effective parameters for extracranial vascular occlusion included intensity ranges of 1,690-8,800 W/cm(2), duration <15 seconds, and 0.68-3.3 MHz frequency. A threshold frequency-intensity product of 8,250 MHzW/cm(2) was needed for vascular occlusion with a sensitivity of 70% and a specificity of 86%. Complications include skin burns, hemorrhage, and damage to surrounding structures. With evidence that HIFU can successfully occlude extracranial blood vessels, refinement in applications and demonstrable intracranial occlusion are needed.

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.

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

BackgroundOcclusion 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.MethodsHIFU 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.ResultsSubharmonic 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).ConclusionsThese 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.

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.

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.

Vertebrobasilar fusiform aneurysms.

Unlike saccular or berry aneurysms, which present more often with subarachnoid hemorrhage, fusiform aneurysms present more often with ischemic stroke or mass effect. The most time-tested treatment of fusiform vertebrobasilar aneurysms consists of flow reduction or flow reversal. Recently, flow diversion has been attempted with mixed results in the posterior circulation. Given the described pathophysiologic processes of fusiform aneurysms that may be altered with modern medical therapies, future investigators may look to medical treatment of these lesions, especially in cases of poor surgical candidates.

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.

Endovascular Management of Posthemorrhagic Cerebral Vasospasm: Indications, Technical Nuances, and Results

Posthemorrhagic cerebral vasospasm (PHCV) is a common problem and a significant cause of mortality and permanent disability following aneurysmal subarachnoid hemorrhage. While medical therapy remains the mainstay of prevention against PHCV and the first-line treatment for symptomatic patients, endovascular options should not be delayed in medically refractory cases. Although both transluminal balloon angioplasty (TBA) and intra-arterial vasodilator therapy (IAVT) can be effective in relieving proximal symptomatic PHCV, only IAVT is a viable treatment option for distal vasospasm. The main advantage of TBA is its long-lasting therapeutic effect and the very low rate of retreatment. However, its use has been associated with a significant risk of serious complications, particularly vessel rupture and reperfusion hemorrhage. Conversely, IAVT is generally considered an effective and low-risk procedure, despite the transient nature of its therapeutic effects and the risk of intracranial hypertension associated with its use. Moreover, newer vasodilator agents appear to have a longer duration of action and a much better safety profile than papaverine, which is rarely used in current clinical practice. Although endovascular treatment of PHCV has been reported to be effective in clinical series, whether it ultimately improves patient outcomes has yet to be demonstrated in a randomized controlled trial.