Category: Vascular

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The A1-A2 Diameter Ratio May Influence Formation and Rupture Potential of Anterior Communicating Artery Aneurysms

AComAA

Neurosurgery 73:845–853, 2013

Specific morphological factors contribute to the hemodynamics of the anterior communicating artery (AComA). No study has examined the role of the A2 segment on AComA aneurysm presence and rupture.

OBJECTIVE: To examine the possibility that the ratio between A1 and A2 segments (A1-2 ratio) represents an independent risk factor for presence and rupture of AComA aneurysms (AComAAs).

METHODS: A retrospective review of an institutional aneurysm database was performed; patients with ruptured and unruptured AComAAs were identified. Two control groups were selected: group A (posterior circulation aneurysms) and group B (patients without intracranial aneurysms or other vascular malformations). Measurements of A1 and A2 diameters were obtained from digital subtraction angiography (64.1% of 3-D rotational digital subtraction angiography), and the A1-2 ratio calculated.

RESULTS: From January 2009 to April 2011, 156 patients were identified (52 AComAAs, 54 control group A, and 50 control group B). Mean age at the time of presentation was 56.09 years. Compared with both control groups, patients with AComAAs had greater A1 diameter (P < .01) and A1-2 ratio (P < .001) and smaller A2 diameter (P < .01). The A1-2 ratio correlated positively with the presence of AComAAs (P < .001). Ruptured AComAAs were smaller than unruptured ones (5.91 mm vs 9.25 mm, P = .02) and associated with a higher A1-2 Ratio (P = .02). The presence of a dominant A1 did not predict AComAA rupture (P = .15). The A1-2 ratio correlated positively with the presence of ruptured AComAAs (P = .04).

CONCLUSION: A1-2 ratio correlates positively with the presence and rupture of AComAAs and may facilitate treatment decision in cases of small, unruptured AComAAs.

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Temporal Lobe Arteriovenous Malformations: Surgical Outcomes With a Focus on Visual Field Defects and Epilepsy

Temporal lobe AVM

Neurosurgery 73:854–862, 2013

Temporal lobe arteriovenous malformations (AVMs) represent a subgroup of intracranial AVMs with particular characteristics and management issues.

OBJECTIVE: To characterize the surgical outcomes of temporal lobe AVMs with emphasis on visual field deficits (VFDs) and seizures.

METHODS: Between 1992 and 2008, 29 patients were operated on for temporal lobe AVMs. Patient data were retrospectively collected and analyzed.

RESULTS: Twelve of 29 patients (41.4%) presented with seizures and 4 (13.7%) presented with VFDs. Postoperatively, 6 patients (24%) showed new VFDs and 2 improved, with a rate of preservation of full visual fields of 84%. Larger AVMs (.3 cm) were significantly associated with postoperative VFD (P = .008). Epilepsy outcomes assessed by the Engel scale were as follows: 9 patients (75%) were in class I (seizure free), 1 patient (8.3%) was in class III, and 2 patients (16.6%) were in class IV (no change or worsening). Postoperative modified Rankin Scale outcomes were excellent (grade 0-1) in 18 patients, good (grade 2) in 7, and poor (grade 3-4) in 4. Older age at diagnosis correlated with a worse functional outcome (Spearman r = 0.369; P = .049). AVMs were totally removed in 27 of 29 patients (93.1%). Complete surgical excision was confirmed with angiography. Two patients needed reoperation for AVM remnant. Three patients had persistent hemiparesis (10.3% permanent morbidity). There was no mortality.

CONCLUSION: Seizure control is usually underappreciated in the surgical management of AVMs. However, in temporal lobe AVMs, good outcomes with low morbidity and good visual field preservation can be accomplished.

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Spinal extradural arteriovenous fistulas

Spinal extradural arteriovenous fistulas

J Neurosurg Spine 19:582–590, 2013

Our understanding of spinal extradural arteriovenous fistulas (eAVFs) is relatively limited. In this study the authors aimed to provide the demographics, natural history, and treatment results of these rare lesions.

Methods. The authors performed a pooled analysis of data in the PubMed database through December 2012. Individualized patient data were extracted to elucidate demographic, clinical, and angioarchitectural features of spinal eAVFs as well as outcomes following different treatment strategies.

Results. Information on 101 patients was extracted from 63 eligible studies. The mean patient age was 45.9 years, and there was no significant overall sex predilection. Only 3% of the lesions were incidental, whereas 10% occurred in patients who had presented with hemorrhage. None of the 64 patients with at least 1 month of untreated follow-up sustained a hemorrhage over a total of 83.8 patient-years. Patients with lumbosacral eAVFs were significantly older (mean age 58.7 years, p < 0.0001), were significantly more often male (70% male, p = 0.02), had significantly worse presenting Aminoff-Logue motor and bladder scores (p = 0.0008 and < 0.0001, respectively), and had the greatest prevalence of lesions with intradural venous drainage (62% of cases, p < 0.0001). Neurofibromatosis Type 1 (30% of cases, p < 0.0001) and subarachnoid hemorrhage (9% of cases, p = 0.06) were associated with and exclusively found in patients with cervical eAVFs. The overall complete obliteration rate was 91%. After a mean follow-up of 1.7 years, the clinical condition was improved in 89% of patients, the same in 9%, and worse in 2%. Obliteration rates and outcome at follow-up did not significantly differ between surgical and endovascular treatment modalities.

Conclusions. Spinal eAVFs are rare lesions with a low risk of hemorrhage; they cause neurological morbidity as a result of mass effect and/or venous hypertension. Their treatment is associated with a high rate of complete obliteration and improvement in preoperative symptoms.

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Intraoperative angiography reloaded: a new hybrid operating theater for combined endovascular and surgical treatment of cerebral arteriovenous malformations

Intraoperative angiography reloaded

Acta Neurochir (2013) 155:2071–2078

Multimodality treatment suites for patients with cerebral arteriovenous malformations (AVM) have recently become available. This study was designed to evaluate feasibility, safety and impact on treatment of a new intraoperative flat-panel (FP) based integrated surgical and imaging suite for combined endovascular and surgical treatment of cerebral AVM.

Methods Twenty-five patients with AVMs to treat with combined endovascular and surgical interventions were prospectively enrolled in this consecutive case series. The hybrid suite allows combined endovascular and surgical approaches with intraoperative scanner-like imaging (XperCT®) and intraoperative 3D rotational angiography (3D-RA). The impact of intraoperative multimodal imaging on feasibility, workflow of combined interventions, surgery, and unexpected imaging findings were analyzed.

Results Twenty-five patients (mean age 38±18.6 year) with a median Spetzler-Martin grade 2 AVM (range 1–4) underwent combined endovascular and surgical procedures. Sixteen patients presented with a ruptured AVM and nine with an unruptured AVM. In 16 % (n=4) of cases, intraoperative imaging visualized AVM remnants ≤3 mm and allowed for completion of the resections in the same sessions. Complete resection was confirmed in all n =16 patients who had follow-up angiography one year after surgery so far. All diagnostic and therapeutical steps, including angiographic control, were performed without having to move the patients

Conclusion The hybrid neurointerventional suite was shown to be a safe and useful setup which allowed for unconstrained combined microsurgical and neuroradiological workflow. It reduces the need for extraoperative angiographic controls and subsequent potential surgical revisions a second time, as small AVM remnants can be detected with high security.

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Anatomic Risk Factors for Middle Cerebral Artery Aneurysm Rupture

Anatomic Risk Factors for Middle Cerebral Artery Aneurysm Rupture-1

Neurosurgery 73:825–837, 2013

The middle cerebral artery (MCA) is the most frequent location for unruptured intracranial aneurysms. Controversy remains as to which unruptured MCA aneurysms should be treated prophylactically.

OBJECTIVE: To identify independent topographical and morphological variables that could predict increased rupture risk of MCA aneurysms.

METHODS: A retrospective analysis of computed tomography angiography data of 1009 consecutive patients with 1309 MCA aneurysms, referred between 2000 and 2009 to Helsinki University Hospital, was carried out. Morphological and topographical parameters examined for MCA aneurysms comprised aneurysm wall regularity, size, neck width, aspect ratio, bottleneck factor, height-width ratio, location along the MCA, side, distance from the internal carotid artery bifurcation, and dome projection in axial and coronal computed tomography angiography views. Univariate and multivariate logistic regression analyses were performed to determine independent risk factors for rupture.

RESULTS: Of the 1309 MCA aneurysms, 69% were unruptured and 31% were ruptured. Most unruptured MCA aneurysms were smaller than 7 mm (78%), with a smooth wall (80%) and a height-width ratio of 1 (47%) and were located at the main bifurcation (57%). Ruptured MCA aneurysms, mostly 7 to 14 mm in size (55%), had an irregular wall (78%) and a height-width ratio greater than 1 (72%) and were located at the main bifurcation (77%). Thirty-eight percent of MCA bifurcation aneurysms, 74% of large aneurysms, 64% of aneurysms with an irregular wall, and 49% of aneurysms with a height-width ratio greater than 1 were ruptured.

CONCLUSION: Location at the main MCA bifurcation, wall irregularity, and less spherical geometry were independently associated with rupture of MCA aneurysms with a correlation with aneurysm size.

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Surgery of brainstem cavernous malformations

Brainstem cavernoma

Acta Neurochir (2013) 155:2079–2083

Cavernomas are vascular hamartomas made up of thin-walled, grossly dilated blood vessels lined with endothelium. Between 4 and 35 % (mean 15 %) of cerebral cavernomas are located in the brainstem making resection of these lesions one of the most challenging tasks in neurosurgery.

Methods Patients with cavernomas within the brainstem or deep supratentorial structures were chosen from our prospectively collected database of operated patients with brain cavernomas. The timespan of treatment was between January 1998 and June 2012. Primary outcome was defined as percentage of patients with favourable outcome (Glasgow Outcome Scale (GOS) 4 or 5) at 1 year. Secondary outcome was defined as operation-related morbidity and mortality (drop at least 1 point on GOS at 1 year).

Results A total of 37 patients underwent surgery. The mean age was 34.7±11.7 years. The male to female ratio was 19:16. Thirty-two patients had a solitary lesion and 12 patients harboured multiple lesions. The Glasgow outcome score 4 or 5 was achieved after 34 operations (89.5 %). The mean follow-up was 39 months.We experienced two early post-operative deaths (5.3 %) and decrease in the Glasgow outcome scale postoperatively in 4 patients (10.5 %).

Conclusions • Favourable outcome was achieved in 89.5 % of cases. • Although M&M appears to be relatively high, surgery is method of choice for surgically accessible lesion which has bled for the first time due to reported high rebleed rate and high probability of poor outcome after cavernoma rebleed. • Radiosurgery should be reserved for those lesions which are deemed unresectable and where surgical intervention is considered favourable to observation alone.

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Impact on Seizure Control of Surgical Resection or Radiosurgery for Cerebral Arteriovenous Malformations

AVM

Neurosurgery 73:648–656, 2013

Seizures are a common presenting symptom of arteriovenous malformations (AVMs). However, the impact of treatment modality on seizure control remains unclear.

OBJECTIVE: To compare seizure control after surgical resection or radiosurgery for AVMs.

METHODS: We analyzed retrospectively collected information for 378 patients with cerebral AVMs treated at our institution from 1990 to 2010. The application of strict inclusion criteria resulted in a study population of 164 patients.

RESULTS: In our cohort, 31 patients (20.7%) had Spetzler-Martin grade I AVMs, 51 (34.0%) grade II, 47 (31.3%) grade III, 20 (13.3%) grade IV, and 1 (0.7%) grade V. Of the 49 patients (30%) presenting with seizures, 60.4% experienced seizure persistence after treatment. For these patients, radiosurgery was associated with seizure recurrence (odds ratio: 4.32, 95% confidence interval: 1.24-15.02, P = .021). AVM obliteration was predictive of seizure freedom at last follow-up (P = .002). In contrast, for patients presenting without seizures, 18.4% experienced de novo seizures after treatment, for which surgical resection was identified as an independent risk factor (hazard ratio: 8.65, 95% confidence interval: 3.05-24.5, P < .001).

CONCLUSION: Although our data suggest that achieving seizure freedom should not be the primary goal of AVM treatment, surgical resection may result in improved seizure control compared with radiosurgery for patients who present with seizures. Conversely, in patients without presenting seizures, surgical resection increases the risk of newonset seizures compared with radiosurgery, but primarily within the early posttreatment period. Surgical resection and radiosurgery result in divergent seizure control rates depending on seizure presentation.

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De Novo Formation of a Cavernoma in a Thrombosed Developmental Venous Anomaly

Magnetic Resonance Evolution of De Novo Formation of a Cavernoma in a Thrombosed Developmental Venous Anomaly

Neurosurgery 73:E739–E745, 2013

Mechanisms that lead to de novo formations of nonfamilial-type cavernomas are not well understood. One of the interesting hypotheses is the causative relationship between developmental venous anomaly (DVA) and cavernoma formation. We report a unique case in which serial imaging demonstrated the evolution of de novo formation of a cavernoma in association with a thrombosed DVA. A detailed review of the causal hypothesis between a DVA and cavernoma is also provided.

CLINICAL PRESENTATION: We report a 37-year-old female patient in whom a cavernoma-like lesion arose 1 year after the progressive thrombosis of a medullary (or caput medusa) vein of a DVA. The presence of an acute angulation in the draining vein may have prompted an intrinsic outflow restriction. Possible worsening of venous disequilibrium led to subsequent thrombus progression, venous congestion, and occlusion of the vein with venous dilation and signs of stasis on follow-up magnetic resonance imaging. Finally, this developed into a lobulated lesion with salt-and-pepper appearance at the converging region of medullary tributaries, which typified the classic features of a cavernoma.

CONCLUSION: Compared with other published cases of de novo cavernoma formation in relation to a DVA, our case, for the first time, allows us to witness the temporal evolution from a thrombosed DVA to the birth of a cavernoma around it. This supports the hypothesis that the cavernoma can be an acquired disease that arises from a DVA.

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Hypoglossal canal dural arteriovenous fistula

Hypoglossal canal dural arteriovenous fistula

J Neurosurg 119:955–960, 2013

The purpose of this study was to evaluate the incidence, radiographic findings, relationship between presenting symptoms for treatment and drainage pattern, and treatment outcomes of hypoglossal canal dural arteriovenous fistula (HC-dAVF).

Methods. During a 16-year period, 238 patients underwent endovascular treatment for cranial dAVF at a single center. The incidence, radiographic findings, relationship between presenting symptoms for treatment and drainage pattern, and treatment outcomes of HC-dAVF were retrospectively evaluated.

Results. The incidence of HC-dAVF was 4.2% (n = 10). Initial symptoms were tinnitus with headache (n = 6), tinnitus only (n = 1), ocular symptoms (n = 1), otalgia (n = 1), and congestive myelopathy (n = 1). Presenting symptoms requiring treatment included ocular symptoms (n = 4), hypoglossal nerve palsy (n = 4), aggravation of myelopathy (n = 1), and aggravation of tinnitus with headache (n = 1). While the affected HC was widened in 4 of 10 patients, hypersignal intensity on source images was conspicuous in all 7 patients who underwent MR angiography (MRA). All ocular symptoms and congestive myelopathy were associated with predominant drainage to superior ophthalmic or perimedullary veins due to antegrade drainage restriction. All patients who underwent transvenous coil embolization (n = 8) or transarterial N-butyl cyanoacrylate (NBCA) embolization (n = 1) improved without recurrence. One patient who underwent transarterial particle embolization had a recurrence 12 months posttreatment and was retreated with transvenous embolization.

Conclusions. The incidence of HC-dAVF was 4.2% of all cranial dAVF patients who underwent endovascular treatment. Source images of MRA helped to accurately diagnose HC-dAVF. More aggressive symptoms may develop as a result of a change in the predominant drainage route due to the development of venous stenosis or obstruction over time. Transvenous coil embolization appears to be the first treatment of choice.

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Hemorrhage risk, surgical management, and functional outcome of brainstem cavernous malformations

Cavernous_angioma_T2

J Neurosurg 119:996–1008, 2013

The aim of this study was to evaluate the pre- and postoperative rehemorrhage risk, neurological function outcome, and prognostic factors of surgically treated brainstem cavernous malformations (CMs) with long-term follow-up.

Methods. The authors conducted a retrospective review of the clinical data from 242 patients with brainstem CMs that were surgically treated between 1999 and 2010. Patient charts, imaging findings, and outcomes were examined.

Results. The study included 242 patients, with a male-to-female ratio of 1.3 and mean age of 32.6 years. The mean modified Rankin Scale scores on admission, at discharge, at 3 and 6 months after surgery, and at recent evaluation were 2.2, 2.6, 2.3, 1.8, and 1.5, respectively. The preoperative calculated annual hemorrhage and rehemorrhage rates were 5.0% and 60.9%, respectively. The complete resection rate was 95%. Surgical morbidity occurred in 112 patients (46.3%). Eighty-five patients (35.1%) demonstrated worsened condition immediately after surgery; 34 (41.0%) and 51 (61.4%) of these patients recovered to their baseline level within 3 and 6 months after surgery, respectively. At a mean follow-up of 89.4 months, the patients’ condition had improved in 147 cases (60.7%), was unchanged in 70 cases (28.9%), and had worsened in 25 cases (10.3%). A total of 8 hemorrhages occurred in 6 patients, and the postoperative annual hemorrhage rate was 0.4%. Permanent morbidity remained in 65 patients (26.9%). The adverse factors for preoperative rehemorrhage were age ≥ 50 years, size ≥ 2 cm, and perilesional edema. The risk factors for postoperative hemorrhage were developmental venous anomaly and incomplete resection. The independent adverse factors for long-term outcome were increased age, multiple hemorrhages, ventral-seated lesions, and poor preoperative status. Favorable, complete improvement in the postoperative deficits over time was correlated with good preoperative neurological function and continuing improvement thereafter.

Conclusions. Favorable long-term outcomes and significantly low postoperative annual hemorrhage rates were achieved via surgery. Total resection should be attempted with an aim of minimal injury to neurological function; however, postoperative deficits can improve during the postoperative course. Close follow-up with radiological examination is proposed for patients with adverse factors predictive of rehemorrhage.

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Fenestration of the lamina terminalis during aneurysm surgery

Lamina terminalis fenestration

J Neurosurg 119:629–633, 2013

Fenestration of the lamina terminalis (FLT) during aneurysm surgery for subarachnoid hemorrhage can, in theory, improve CSF circulation from the lateral and third ventricles to the cortical subarachnoid space, which may, in turn, decrease the incidence of hydrocephalus and vasospasm. However, the actual effects of FLT on CSF circulation have been difficult to determine, due to confounding factors. In addition, it is unclear whether the lamina terminalis remains functionally patent when the brain resumes its normal position. The goal of this study was to assess the functional patency of the fenestrated lamina terminalis in patients who underwent surgery for ruptured aneurysms.

Methods. This prospective study included 15 patients who underwent surgical clipping of ruptured anterior circulation aneurysms, with FLT performed during surgery. On postoperative Day 1, the external ventricular drain of each patient was closed, and 1 ml of Omnipaque 300, an iodine-based contrast agent, was injected intraventricularly, accompanied by cranial maneuvering designed to position the contrast agent adjacent to the lamina terminalis. Three to 5 minutes after cranial maneuvering, the flow of contrast agent into the basal cisterns was assessed with CT imaging. Flow was verified by an increase in Hounsfield units in a prespecified “region of interest” within the basal cisterns on the CT scan. This procedure was performed using a standardized protocol designed in consultation with the Department of Radiology and approved by the institutional review board. One patient who underwent endoscopic third ventriculostomy was recruited as a positive control to validate the technique, and 1 patient who underwent aneurysm clipping but not FLT was recruited as a negative control.

Results. Seventeen patients consented to study participation. In the 15 patients who underwent aneurysm clipping and FLT, and the negative control patient who underwent aneurysm clipping but not FLT, the contrast agent followed the normal ventricular pathway from the lateral ventricles into the fourth ventricle, and did not appear in the basal cisterns. In the positive control patient, the contrast agent robustly and immediately filled the basal cisterns.

Conclusions. Fenestration of the lamina terminalis did not result in functional patency of the lamina terminalis when performed as part of surgical clipping for ruptured aneurysms.

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Indocyanine Green Videoangiography “In Negative”: Definition and Usefulness in Intracranial Dural Arteriovenous Fistulae

Indocyanine Green Videoangiography “In Negative”- Definition and Usefulness in Intracranial Dural Arteriovenous Fistulae

Neurosurgery 73[ONS Suppl 1]:ons86–ons92, 2013

Indocyanine green videoangiography (IGV) raises important limitations when we use it in vascular pathology, especially in cases with arterialization of the venous system such as arteriovenous malformations and fistulae.

OBJECTIVE: Our objective was to provide a simple procedure that overcomes the limitations of conventional IGV. We define IGV in negative (IGV-IN), so-called because, in its first phase, the vessel to analyze is clipped, and we report 3 cases of intracranial dural arteriovenous fistulae treated with this procedure.

METHODS: In 2011, we applied IGV-IN to 3 patients at our center with Borden type III intracranial arteriovenous fistulae.

RESULTS: In all 3 cases, IGV-IN enabled both diagnosis and post-dural arteriovenous fistula exclusion control in 1 integrated procedure no longer than 1 minute, requiring only 1 visualization.

CONCLUSION: IGV-IN is an improvement over the conventional IGV method and is able to provide more information in a shorter period of time. It is an intuitive and highly visual procedure, and, more importantly, it is reversible. Studies with larger samples are necessary to determine whether IGV-IN can further reduce the need for postoperative digital subtraction angiography.

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Temporal lobe arteriovenous malformations: anatomical subtypes, surgical strategy, and outcomes

Temporal lobe AVM

J Neurosurg 119:616–628, 2013

Descriptions of temporal lobe arteriovenous malformations (AVMs) are inconsistent. To standardize reporting, the authors blended existing descriptions in the literature into an intuitive classification with 5 anatomical subtypes: lateral, medial, basal, sylvian, and ventricular. The authors’ surgical experience with temporal lobe AVMs was reviewed according to these subtypes.

Methods. Eighty-eight patients with temporal lobe AVMs were treated surgically.

Results. Lateral temporal lobe AVMs were the most common (58 AVMs, 66%). Thirteen AVMs (15%) were medial, 9 (10%) were basal, and 5 (6%) were sylvian. Ventricular AVMs were least common (3 AVMs, 3%). A temporal craniotomy based over the ear was used in 64%. Complete AVM resection was achieved in 82 patients (93%). Four patients (5%) died in the perioperative period (6 in all were lost to follow-up); 71 (87%) of the remaining 82 patients had good outcomes (modified Rankin Scale scores 0–2); and 68 (83%) were unchanged or improved after surgery.

Conclusions. Categorization of temporal AVMs into subtypes can assist with surgical planning and also standardize reporting. Lateral AVMs are the easiest to expose surgically, with circumferential access to feeding arteries and draining veins at the AVM margins. Basal AVMs require a subtemporal approach, often with some transcortical dissection through the inferior temporal gyrus. Medial AVMs are exposed tangentially with an orbitozygomatic craniotomy and transsylvian dissection of anterior choroidal artery and posterior cerebral artery feeders in the medial cisterns. Medial AVMs posterior to the cerebral peduncle require transcortical approaches through the temporooccipital gyrus. Sylvian AVMs require a wide sylvian fissure split and differentiation of normal arteries, terminal feeding arteries, and transit arteries. Ventricular AVMs require a transcortical approach through the inferior temporal gyrus that avoids the Meyer loop. Surgical results with temporal lobe AVMs are generally good, and classifying them does not offer any prediction of surgical risk.

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Intracranial Aneurysms Occur More Frequently at Bifurcation Sites That Typically Experience Higher Hemodynamic Stresses

ANEURYSM SUSCEPTIBILITY AND HEMODYNAMIC STRESS

Neurosurgery 73:497–505, 2013 

Intracranial aneurysms (IAs) occur more frequently at certain bifurcations than at others. Hemodynamic stress, which promotes aneurysm formation in animal models, also differs among bifurcations, depending on flow and vessel geometry.

OBJECTIVE: To determine whether locations that are more likely to develop IAs experience different hemodynamic stresses that might contribute to higher IA susceptibility.

METHODS: We characterized the hemodynamic microenvironment at 10 sites in or around the circle of Willis where IAs commonly occur and examined statistical relationships between hemodynamic factors and the tendency for a site to form IAs. The tendency for each site to develop IAs was quantified on the basis of the site distribution from systematic literature analysis of 19 reports including 26 418 aneurysms. Hemodynamic parameters for these sites were derived from image-based computational fluid dynamics of 114 cerebral bifurcations from 31 individuals. Wall shear stress and its spatial gradient were calculated in the impact zone surrounding the bifurcation apex. Linear and exponential regression analyses evaluated correlations between the tendency for IA formation and the typical hemodynamics of a site.

RESULTS: IA susceptibility significantly correlated with the magnitudes of wall shear stress and positive wall shear stress gradient within the hemodynamic impact zone calculated for each site.

CONCLUSION: IAs occur more frequently at cerebral bifurcations that typically experience higher hemodynamic shear stress and stronger flow acceleration, conditions previously shown to promote aneurysm initiation in animals.

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Deep Arteriovenous Malformations in the Basal Ganglia, Thalamus, and Insula: Microsurgical Management, Techniques, and Results

Surgery for Deep AVM-1

Neurosurgery 73:417–429, 2013

Arteriovenous malformations (AVMs) in the basal ganglia, thalamus, and insula are considered inoperable given their depth, eloquence, and limited surgical exposure. Although many neurosurgeons opt for radiosurgery or observation, others have challenged the belief that deep AVMs are inoperable. Further discussion of patient selection, technique, and multimodality management is needed.

OBJECTIVE: To describe and discuss the technical considerations of microsurgical resection for deep-seated AVMs.

METHODS: Patients with deep AVMs who underwent surgery during a 14-year period were reviewed through the use of a prospective AVM registry.

RESULTS: Microsurgery was performed in 48 patients with AVMs in the basal ganglia (n = 10), thalamus (n = 13), or insula (n = 25). The most common Spetzler-Martin grade was III2 (68%). Surgical approaches included transsylvian (67%), transcallosal (19%), and transcortical (15%). Complete resection was achieved in 34 patients (71%), and patients with incomplete resection were treated with radiosurgery. Forty-five patients (94%) were improved or unchanged (mean follow-up, 1.6 years).

CONCLUSION: This experience advances the notion that select deep AVMs may be operable lesions. Patients were highly selected for small size, hemorrhagic presentation, young age, and compactness—factors embodied in the Spetzler-Martin and Supplementary grading systems. Overall, 10 different approaches were used, exploiting direct, transcortical corridors created by hemorrhage or maximizing anatomic corridors through subarachnoid spaces and ventricles that minimize brain transgression. The same cautious attitude exercised in selecting patients for surgery was also exercised in deciding extent of resection, opting for incomplete resection and radiosurgery more than with other AVMs to prioritize neurological outcomes.

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Cerebral microarteriovenous malformations

microAVM

J Neurosurg 119:594–602, 2013

Microarteriovenous malformations (micro-AVMs) are a rare subgroup of brain AVMs characterized by a nidus smaller than 1 cm. The authors’ purpose in this study was to assess the clinical presentation, radiological features, therapeutic management, and outcome of these lesions.

METHODS
All angiography studies performed at the authors’ institution since 2000 for the diagnosis of AVM were retrospectively reviewed. Clinicoradiological findings, therapeutic management, and outcome were evaluated.

RESULTS
Twenty-eight patients had presented with AVMs having a nidus diameter smaller than 1 cm or no clearly identifiable nidus but an early draining vein. All patients, except 2, presented with intracranial hemorrhage, and 12 patients had a focal deficit. Supratentorial hematomas were large (mean volume 25 ml), and in 8 patients hematomas were evacuated urgently. In 6 patients cerebral digital subtraction angiography studies were normal. Magnetic resonance imaging and dynamic MR angiography revealed an AVM in 4 of these 6 patients. Treatment of the AVM consisted of surgery in 16 cases, radiosurgery in 6, and endovascular embolization in 2, and there were no posttreatment deficits. Four patients received no treatment because of their poor condition. The AVM was occluded at the follow-up in all patients treated with surgery or embolization and in 4 of the 6 patients treated with radiosurgery. The Glasgow Outcome Scale (GOS) score was good (GOS 4–5) in 23 patients (82%) and poor (GOS 3–2) in 5 (18%).

CONCLUSIONS
Patients with micro-AVMs generally present with large intracranial hemorrhages and neurological deficits. If the initial angiography is negative, then delayed or superselective angiography is recommended. Magnetic resonance imaging may reveal the existence of these lesions. Surgery is the treatment of choice for superficial micro-AVMs, and radiosurgery or embolization can be considered for deep lesions.

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Nonsurgical treatment of chronic subdural hematoma with tranexamic acid

SDH

J Neurosurg 119:332–337, 2013

Chronic subdural hematoma (CSDH) is a common condition after head trauma. It can often be successfully treated surgically by inserting a bur hole and draining the liquefied hematoma. However, to the best of the authors’ knowledge, for nonemergency cases not requiring surgery, no reports have indicated the best approach for preventing hematoma enlargement or resolving it completely. The authors hypothesized that hyperfibrinolysis plays a major role in liquefaction of the hematoma. Therefore, they evaluated the ability of an antifibrinolytic drug, tranexamic acid, to completely resolve CSDH compared with bur hole surgery alone.

METHODS
From 2007 to 2011, a total of 21 patients with CSDH seen consecutively at Kuki General Hospital, Japan, were given 750 mg of tranexamic acid orally every day. Patients were identified by a retrospective records review, which collected data on the volume of the hematoma (based on radiographic measurements) and any complications. Follow-up for each patient consisted of CT or MRI every 21 days from diagnosis to resolution of the CSDH.

RESULTS
Of the 21 patients, 3 with early stages of CSDH were treated by bur hole surgery before receiving medical therapy. The median duration of clinical and radiographic follow-up was 58 days (range 28–137 days). Before tranexamic acid therapy was initiated, the median hematoma volume for the 21 patients was 58.5 ml (range 7.5–223.2 ml); for the 18 patients who had not undergone surgery, the median hematoma volume was 55.6 ml (range 7.5–140.5 ml). After therapy, the median volume for all 21 patients was 3.7 ml (range 0–22.1 ml). No hematomas recurred or progressed.

CONCLUSIONS
Chronic subdural hematoma can be treated with tranexamic acid without concomitant surgery. Tranexamic acid might simultaneously inhibit the fibrinolytic and inflammatory (kinin-kallikrein) systems, which might consequently resolve CSDH. This medical therapy could prevent the early stages of CSDH that can occur after head trauma and the recurrence of CSDH after surgery.

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Early awareness of cerebrospinal fluid hypovolemia after craniotomy for microsurgical aneurysmal clipping

Early awareness of cerebrospinal fluid hypovolemia after craniotomy for microsurgical aneurysmal clipping

Acta Neurochir (2013) 155:1543–1548

Mild cerebrospinal fluid (CSF) hypovolemia is a well-known clinical entity, but critical CSF hypovolemia that can cause transtentorial herniation is an unusual and rare clinical entity that occurs after craniotomy. We investigated CSF hypovolemia after microsurgical aneurysmal clipping for subarachnoid hemorrhage (SAH).

Method This study included 144 consecutive patients with SAH. Lumbar drainage (LD) was inserted after general anesthesia or postoperatively as a standard perioperative protocol. CSF hypovolemia diagnosis was based on three criteria.

Results Eleven patients (7.6 %) were diagnosed with CSF hypovolemia according to diagnostic criteria in a postoperative range of 0–8 days. In all patients, signs or symptoms of CSF hypovolemia improved within 24 hours by clamping LD and using the Trendelenburg position.

Conclusions As a cause of acute clinical deterioration after aneurysmal clipping, CSF hypovolemia is likely underrecognized, and may actually be misdiagnosed as vasospasm or brain swelling. We should always take the etiology of CSF hypovolemia into consideration, and especially pay attention in patients with pneumocephalus and subdural fluid collection alongside brain sag on computed tomography. These patients are at higher risk developing of pressure gradients between their cranial and spinal compartments, and therefore, brain sagging after LD, than after ventricular drainage. We should be vigilant to strictly manage LD so as not to produce high pressure gradients.

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Emergency Noninvasive Angiography for Acute Intracerebral Hemorrhage

CTA

Am J Neuroradiol 34:1481– 87. 2013

Spontaneous ICH is a devastating condition and is associated with significant mortality in the acute phase due to ongoing hemorrhage and hematoma expansion. A growing body of evidence suggests that there may be considerable utility in performing noninvasive vascular imaging during the acute-to-early phase of ICH.

CTA has become widely available and is sensitive and specific for detecting vascular causes of secondary ICH such as aneurysms, arteriovenous malformations, dural arteriovenous fistulas, intracranial dissections, and neoplasm.

CT venography can also diagnose dural sinus thrombosis presenting as hemorrhagic infarction.

Recent data from stroke populations demonstrate a relatively low risk to patients when contrast is administered in the absence of a known serum creatinine. Detection of acute contrast extravasation within the hematoma (“spot sign”) with CT angiography is predictive of subsequent hematoma expansion and is associated with increased morbidity and mortality.

Risk stratification based on acute CTA can inform and expedite decision-making regarding intensive care unit admission, blood pressure control, correction of coagulopathy, and neurosurgical consultation. Noninvasive vascular imaging should be considered as an important component of the initial diagnostic work-up for patients presenting with acute ICH.

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Flow-Diverter Devices for Intracranial Aneurysms

Flow-Diverter Devices for Intracranial Aneurysms

Neurosurgery 73:193–200, 2013

Although the introduction of flow-diverter devices (FDDs) has aroused great enthusiasm, the level of evidence supporting their use has not been systematically evaluated.

OBJECTIVE: To report a systematic review of medical literature up to May 2012 on FDDs to assess the morbidity, case fatality rate, and efficacy of FDDs for intracranial aneurysms.

METHODS: The literature was searched by using MEDLINE, Embase, and all Evidence- Based Medicine in the OVID database. Eligibility criteria were studies including at least 10 patients, reporting duration of follow-up and number of patients lost to follow-up, and documenting the rate of aneurysm occlusion and death and neurological complications. The endpoints were angiographic success, early and late mortality, and neurological morbidity.

RESULTS: Fifteen studies were analyzed consisting of 897 patients with 1018 aneurysms. The mean value of methodological quality score was 14.4 using the STROBE score. The early mortality rate was 2.8% (95% confidence interval [CI]: 1.7-3.8; I2 = 93.4%) and the late mortality rate was 1.3% (95% CI: 0.2-2.3; I2 = 36.9%). The early neurological morbidity rate was 7.3% (95% CI: 5.7-9; I2 = 91.8%) and the late morbidity rate was 2.6% (95% CI: 1.1-4; I2 = 81.3%). The Egger test for early and late morbidity and aneurysm occlusion was ,0.001.

CONCLUSION: With the available data from the studies, both heterogeneity and publication biases imply that the current clinical use of FDDs is not supported by highquality evidence. In the absence of reliable evidence, the use of FDDs in patients eligible for more conventional treatments should be restricted to controlled clinical trials.

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