Clemens M. Schirmer

Decompressive Hemicraniectomy for the Treatment of Intractable Intracranial Hypertension After Aneurysmal Subarachnoid Hemorrhage

Background and Purpose— Decompressive hemicraniectomy and duroplasty (DHCD) can improve survival in patients with severe cerebral edema. We present our clinical experience with DHCD for the treatment of refractory elevated intracranial pressure (ICP) in patients with aneurysmal subarachnoid hemorrhage (aSAH). Methods— DHCD was performed in 16 patients (11 female; median age, 49.5 years) with aSAH (11 Hunt-Hess grade 4 to 5) for sustained ICP >250 mm H2O refractory to maximal medical treatment and cerebrospinal fluid drainage at a median of 2 days from admission. Half of the patients were treated with endovascular coiling and the other half with surgical clipping. Results— DHCD (mean flap size, 8536 mm2) reduced ICP from 350±157 to 147±124 mm H2O. Eleven patients survived (69%), and at latest follow-up (median, 450 days), 7 (64%) had a modified Rankin score of 0 to 3 and 4 (36%) a score of 4 to 5. Peak herniated brain volume was inversely associated with good outcome (P<0.005). Early craniectomy performed within 48 hours after the aSAH was associated with better outcome: 6 of 8 patients had good outcomes (75%) compared with 1 of 8 patients in whom late decompression was performed (P<0.01). Midline shift, Hunt-Hess grade, presence of hemorrhage, hematoma volume, craniectomy area, peak ICP, and relative ICP reduction were not associated with outcome in this patient population. Conclusions— DHCD is a useful adjunct modality for management of refractory intracranial hypertension in patients with high-grade aSAH, even in the absence of large intraparenchymal hemorrhage. In our series, long-term outcome was better in patients who underwent early intervention.

Aneurysm Inflow-Angle as a Discriminant for Rupture in Sidewall Cerebral Aneurysms Morphometric and Computational Fluid Dynamic Analysis

Background and Purpose— The ability to discriminate between ruptured and unruptured cerebral aneurysms on a morphological basis may be useful in clinical risk stratification. The objective was to evaluate the importance of inflow-angle (IA), the angle separating parent vessel and aneurysm dome main axes. Methods— IA, maximal dimension, height–width ratio, and dome–neck aspect ratio were evaluated in sidewall-type aneurysms with respect to rupture status in a cohort of 116 aneurysms in 102 patients. Computational fluid dynamic analysis was performed in an idealized model with variational analysis of the effect of IA on intra-aneurysmal hemodynamics. Results— Univariate analysis identified IA as significantly more obtuse in the ruptured subset (124.9°±26.5° versus 105.8°±18.5°, P=0.0001); similarly, maximal dimension, height–width ratio, and dome–neck aspect ratio were significantly greater in the ruptured subset; multivariate logistic regression identified only IA (P=0.0158) and height–width ratio (P=0.0017), but not maximal dimension or dome–neck aspect ratio, as independent discriminants of rupture status. Computational fluid dynamic analysis showed increasing IA leading to deeper migration of the flow recirculation zone into the aneurysm with higher peak flow velocities and a greater transmission of kinetic energy into the distal portion of the dome. Increasing IA resulted in higher inflow velocity and greater wall shear stress magnitude and spatial gradients in both the inflow zone and dome. Conclusions— Inflow-angle is a significant discriminant of rupture status in sidewall-type aneurysms and is associated with higher energy transmission to the dome. These results support inclusion of IA in future prospective aneurysm rupture risk assessment trials.

Pneumocephalus: Case Illustrations and Review

BackgroundPneumocephalus is commonly encountered after neurosurgical procedures but can also be caused by craniofacial trauma and tumors of the skull base and rarely, can occur spontaneously. Contributing factors for the development of pneumocephalus include head position, duration of surgery, nitrous oxide (N2O) anesthesia, hydrocephalus, intraoperative osmotherapy, hyperventilation, spinal anesthesia, barotauma, continuous CSF drainage via lumbar drain, epidural anesthesia, infections, and neoplasms. Clinical presentation includes headaches, nausea and vomiting, seizures, dizziness, and depressed neurological status. In this article, we review the incidence, mechanisms, precipitating factors, diagnosis, and management of pneumocephalus. Search of Medline, databases, and manual review of article bibliographies. Considering four case illustrations that typify pneumocephalus in clinical practice, we discuss the common etiologies, and confirm the diagnosis with neuroimaging and management strategies. Avoidance of contributing factors, high index of suspicion, and confirmation with neuroimaging are important in attenuating mortality and morbidity. A significant amount of pneumocephalus can simulate a space-occupying lesion. Supplemental oxygen increases the rate of absorption of pneumocephalus.

Virtual Reality-Based Simulation Training for Ventriculostomy: An Evidence-Based Approach

BACKGROUND:Virtual reality (VR) simulation-based technologies play an important role in neurosurgical resident training. The Congress of Neurological Surgeons (CNS) Simulation Committee developed a simulation-based curriculum incorporating VR simulators to train residents in the management of commonBACKGROUND Virtual reality (VR) simulation-based technologies play an important role in neurosurgical resident training. The Congress of Neurological Surgeons (CNS) Simulation Committee developed a simulation-based curriculum incorporating VR simulators to train residents in the management of common neurosurgical disorders. OBJECTIVE To enhance neurosurgical resident training for ventriculostomy placement using simulation-based training. METHODS A course-based neurosurgical simulation curriculum was introduced at the Neurosurgical Simulation Symposium at the 2011 and 2012 CNS annual meetings. A trauma module was developed to teach ventriculostomy placement as one of the neurosurgical procedures commonly performed in the management of traumatic brain injury. The course offered both didactic and simulator-based instruction, incorporating written and practical pretests and posttests and questionnaires to assess improvement in skill level and to validate the simulators as teaching tools. RESULTS Fourteen trainees participated in the didactic component of the trauma module. Written scores improved significantly from pretest (75%) to posttest (87.5%; P < .05). Seven participants completed the ventriculostomy simulation. Significant improvements were observed in anatomy (P < .04), burr hole placement (P < .03), final location of the catheter (P = .05), and procedure completion time (P < .004). Senior residents planned a significantly better trajectory (P < .01); junior participants improved most in terms of identifying the relevant anatomy (P < .03) and the time required to complete the procedure (P < .04). CONCLUSION VR ventriculostomy placement as part of the CNS simulation trauma module complements standard training techniques for residents in the management of neurosurgical trauma. Improvement in didactic and hands-on knowledge by course participants demonstrates the usefulness of the VR simulator as a training tool.

WALL SHEAR STRESS GRADIENT ANALYSIS WITHIN AN IDEALIZED STENOSIS USING NON-NEWTONIAN FLOW

OBJECTIVEThe endothelium is functionally regulated by the magnitude and spatiotemporal gradients of wall shear stress (WSS). Although flow separation and reversal occur beyond high-grade stenoses, little is known of the WSS pattern within clinically relevant mild to moderate stenoses. METHODSAn axisymmetric geometry with 25, 50, and 75% stenosis criteria (quantified in accordance with the North American Symptomatic Carotid Endarterectomy Trial) was used to generate a high-resolution, hybrid, tetrahedral-hexahedral computational mesh with boundary-layer enrichment to improve near-wall shear stress gradient (WSSG) computation. Time-dependent computational fluid dynamic analysis was performed using a non-Newtonian Carreau-Yasuda model of blood to yield the shear-dependent viscosity. RESULTSTransition to secondary flow patterns was demonstrated in stenoses of 25, 50, and 75%. A focal region with near-wall flow reversal and retrograde WSS was identified within the stenosis itself and was found to migrate cyclically during the cardiac pulse. A zone of zero WSS and divergent WSSG that shifts in toward the throat with increasing stenotic severity was identified. Focal zones of high WSSG with converging and/or diverging direction were uncovered within the stenosis itself, as were expected changes in the distal poststenotic region. These zones of divergent WSSG shift over a substantial length of the stenosis during the course of the cardiac cycle. CONCLUSIONLuminal WSS demonstrates dynamic direction reversal and high spatial gradients within the distal stenosis throat of even clinically moderate lesions. These findings shed light on the complex vessel wall hemodynamics within clinical stenoses and reveal a mechanical microenvironment that is conducive to perpetual endothelial functional dysregulation and stenosis progression.

Prediction of complex flow patterns in intracranial atherosclerotic disease using computational fluid dynamics.

OBJECTIVEAlthough carotid and vertebral intracranial atherosclerotic disease (ICAD) can lead to both hemodynamic insufficiency and thromboembolism, its fluid dynamic properties remain undefined because of its intricate features and complex three-dimensional geometry. We used computational fluid dynamic (CFD) analysis to model the hemodynamics of symptomatic ICAD lesions. METHODSNine ICAD lesions (six carotid, two vertebral, one middle cerebral) underwent high-resolution catheter-based digital rotational angiography. The reconstructed three-dimensional volumes of the target lesions were segmented and used to generate hybrid computational meshes. Dynamic pulsatile CFD analysis was performed using a non-Newtonian shear-dependent model of bloods viscosity. RESULTSCFD results revealed complex flow patterns within ICAD lesions with midstenotic shear rates of greater than 19,000/s, sufficiently high to induce high-shear platelet activation. Vorticity and helicity within the stenoses were followed by sudden deceleration with formation of vortex cores. Pressure gradients were significant mostly at greater than 75% stenosis with a mean time-averaged drop of 27.2 ±17.8 mmHg. Unlike the smoothly-varying helicity imparted by the three-dimensional anatomy of the intracranial circulation, poststenotic regions of ICAD lesions showed significant and rapidly fluctuating helicity and vorticity patterns, which may contribute to the propagation of platelets activated by the high shear region within the stenosis throat. Stent angioplasty restored the hemodynamic profile of ICAD lesions to within contralateral controls. CONCLUSIONPatient-based symptomatic ICAD lesions studied using CFD analysis appear to harbor a hemodynamically pathological environment that favors the activation, aggregation and distal embolization of platelets and is reversed by endovascular stent angioplasty.

Successful bilateral deep brain stimulation of the globus pallidus internus for persistent status dystonicus and generalized chorea

The authors report the cases of 2 young male patients (aged 16 and 26 years) with dystonic cerebral palsy of unknown origin, who developed status dystonicus, an acute and persistent combination of generalized dystonia and chorea. Both patients developed status dystonicus after undergoing general anesthesia, and in 1 case, after administration of metoclopramide. In attempting to control this acute hyperkinetic movement disorder, multiple medication trials failed in both cases and patients required prolonged intubation and sedation with propofol. Bilateral deep brain stimulation of the globus pallidus internus (4 and 2 months after the onset of symptoms in the first and second case, respectively) produced immediate resolution of the hyperkinetic movement disorder in each case. Deep brain stimulation provided persistent suppression of the dystonic movement potential after a follow-up of 30 and 34 months, respectively, as demonstrated by the reemergence of severe dystonia during the end of battery life of the implantable pulse generators that was readily controlled by exchange of the generators in each case.

Preoperative embolization of hypervascular spinal metastases using percutaneous direct injection with n-butyl cyanoacrylate: technical case report.

OBJECTIVE:Intraoperative blood loss constitutes a major cause of perioperative morbidity in surgical decompression and reconstruction of highly vascular spinal metastatic tumors. We propose a technique for embolization of highly vascular vertebral metastases using percutaneous direct injection using n-butyl cyanoacrylate (NBCA) instead of polymethylmethacrylate to complement preoperative transarterial embolization and to minimize operative blood loss. METHODS:Five patients with renal cell carcinoma metastases to the spine (one cervical, one thoracic, and three lumbar) underwent embolization by percutaneous direct injection of the affected vertebrae with a mixture of NBCA and iodized oil to supplement transarterial embolization with polyvinyl alcohol particles and fibered platinum coils. This was achieved via a transpedicular approach in four cases and by direct vertebral body puncture in one case. RESULTS:The percutaneous NBCA direct injection procedure was technically successful in all cases and was not associated with neurological or medical complications. All patients underwent subsequent vertebrectomy and spinal instrumentation. Surgical resection was performed with lower than expected blood loss and with a subjective improvement in tumor tissue handling and dissection. CONCLUSION:The extent of tumor devascularization can be improved by supplementing transarterial embolization with NBCA direct injection to decrease operative blood loss and increase the safety of surgical resection and stabilization of highly vascular spinal metastases.

Angiographic detection of carotid and vertebral arterial injury in the high-energy blunt trauma patient.

Background and Objective Injury to the carotid and vertebral arteries is an identified risk to patients after blunt high-energy cranio-cervical trauma with an associated risk of thromboembolic stroke. We sought to determine the incidence, features, and risk factors of arterial injury using selective cerebral angiography in a high-risk trauma patient subset. Methods Blunt trauma patients with a high-energy mechanism were selected to undergo screening cerebral angiography if they met one of the following criteria: (1) cervical spine hyperextension/hyperflexion injury, (2) skull-base or facial fracture, (3) lateralizing neurologic deficit, ischemic deficit, or cerebral infarction, or (4) hemorrhage of arterial origin. Results Of 69 screened patients 20 were found to have a vascular injury (28.9%), including 13 carotid and 15 vertebral; 9 of the 20 patients with vascular injury were symptomatic (45%). The most frequent injuries were intimal dissections (8/28), pseudoaneurysms (6/28), and vessel occlusions (5/28); 8 lesions were intracranial and 20 cervical. Displaced facial fractures (P<0.02) but not skull-base fracture were predictive of carotid injury; multilevel cervical spine fractures (P<0.001) and transverse foraminal fractures (P<0.02) were associated with vertebral injury. Conclusions Cerebral angiography in a selected group of trauma patients was found to yield a significant rate of carotid and vertebral arterial injury, a finding that had implications to subsequent clinical management.

Use of the Amplatzer vascular plug as an anchoring scaffold for coil-mediated parent vessel occlusion: technical case report.

OBJECTIVE: Parent vessel sacrifice is a useful treatment strategy for fusiform intracranial aneurysms. Originally performed using the detachable silicone balloon, endovascular arterial occlusion is currently achieved using coils, a process which can be limited by coil mass migration. METHODS: We demonstrate the use of the Amplatzer vascular plug as a fixed anchor within the target parent vessel to facilitate coil-mediated occlusion, especially in vascular segments not encased by a bony canal. The technique was used successfully in two patients: a 90-year-old woman presenting with IIIrd and VIth cranial nerve palsy from a fusiform left cavernous internal carotid aneurysm and a 44-year-old man with distal thromboemboli from a fusiform dissecting-type right vertebral artery involving the origin of the posterior inferior cerebellar artery. RESULTS: Both patients were treated successfully with proximal parent vessel occlusion using coils after deployment of an Amplatzer vascular plug proximal to the target lesion. With the Amplatzer device acting as a fixed anchor in the parent vessel, coils were deployed proximally in a compact configuration. After deployment of the vascular plugs and coils, hermetic occlusion of the parent vessel was documented angiographically. CONCLUSION: The Amplatzer vascular plug can facilitate coil occlusion of large cervical vessels by acting as a focal coil and embolic material immobilizer, which can prevent coil mass migration and lead to improved packing density.