Neurosurgery Blog


Daily bibliographic review of the Neurosurgery Department. La Fe University Hospital. Valencia, Spain

Ventriculostomy-associated hemorrhage: a risk assessment by radiographic simulation

J Neurosurg 127:532–536, 2017

Ventriculostomy entry sites are commonly selected by freehand estimation of Kocher’s point or approximations from skull landmarks and a trajectory toward the ipsilateral frontal horn of the lateral ventricles. A recognized ventriculostomy complication is intracranial hemorrhage from cortical vessel damage; reported rates range from 1% to 41%. In this report, the authors assess hemorrhagic risk by simulating traditional ventriculostomy trajectories and using CT angiography (CTA) with venography (CTV) data to identify potential complications, specifically from cortical draining veins.

METHODS Radiographic analysis was completed on 50 consecutive dynamic CTA/CTV studies obtained at a tertiarycare academic neurosurgery department. Image sections were 0.5 mm thick, and analysis was performed on a venous phase that demonstrated high-quality opacification of the cortical veins and sagittal sinus. Virtual ventriculostomy trajectories were determined for right and left sides using medical diagnostic imaging software. Entry points were measured along the skull surface, 10 cm posteriorly from the nasion, and 3 cm laterally for both left and right sides. Cannulation was simulated perpendicular to the skull surface. Distances between the software-traced cortical vessels and the virtual catheter were measured. To approximate vessel injury by twist drill and ventricular catheter placement, veins within a 3-mm radius were considered a hemorrhage risk.

RESULTS In 100 virtual lines through Kocher’s point toward the ipsilateral ventricle, 19% were predicted to cause cortical vein injury and suspected hemorrhage (radius ≤ 3 mm). Little difference existed between cerebral hemispheres (right 18%, left 20%). The average (± SD) distance from the trajectory line and a cortical vein was 7.23 ± 4.52 mm. In all 19 images that predicted vessel injury, a site of entry for an avascular zone near Kocher’s point could be achieved by moving the trajectory less than 1.0 cm laterally and less than 1.0 cm along the anterior/posterior axis, suggesting that empirical measures are suboptimal, and that patient-specific coordinates based on preprocedural CTA/CVA imaging may optimize ventriculostomy in the future.

CONCLUSIONS In this institutional radiographic imaging analysis, traditional methods of ventriculostomy site selection predicted significant rates of cortical vein injury, matching described rates in the literature. CTA/CTV imaging potentiates identification of patient-specific cannulation sites and custom trajectories that avoid cortical vessels, which may lessen the risk of intracranial hemorrhage during ventriculostomy placement. Further development of this software is underway to facilitate stereotactic ventriculostomy and improve outcomes.

Stereotactic radiosurgery for cerebellar arteriovenous malformations: an international multicenter study

J Neurosurg 127:512–521, 2017

Cerebellar arteriovenous malformations (AVMs) represent the majority of infratentorial AVMs and frequently have a hemorrhagic presentation. In this multicenter study, the authors review outcomes of cerebellar AVMs after stereotactic radiosurgery (SRS).

METHODS: Eight medical centers contributed data from 162 patients with cerebellar AVMs managed with SRS. Of these patients, 65% presented with hemorrhage. The median maximal nidus diameter was 2 cm. Favorable outcome was defined as AVM obliteration and no posttreatment hemorrhage or permanent radiation-induced complications (RICs). Patients were followed clinically and radiographically, with a median follow-up of 60 months (range 7–325 months).

RESULTS: The overall actuarial rates of obliteration at 3, 5, 7, and 10 years were 38.3%, 74.2%, 81.4%, and 86.1%, respectively, after single-session SRS. Obliteration and a favorable outcome were more likely to be achieved in patients treated with a margin dose greater than 18 Gy (p < 0.001 for both), demonstrating significantly better rates (83.3% and 79%, respectively). The rate of latency preobliteration hemorrhage was 0.85%/year. Symptomatic post-SRS RICs developed in 4.5% of patients (n = 7). Predictors of a favorable outcome were a smaller nidus (p = 0.0001), no pre-SRS embolization (p = 0.003), no prior hemorrhage (p = 0.0001), a higher margin dose (p = 0.0001), and a higher maximal dose (p = 0.009). The Spetzler-Martin grade was not found to be predictive of outcome. The Virginia Radiosurgery AVM Scale score (p = 0.0001) and the Radiosurgery-Based AVM Scale score (p = 0.0001) were predictive of a favorable outcome.

CONCLUSIONS: SRS results in successful obliteration and a favorable outcome in the majority of patients with cerebellar AVMs. Most patients will require a nidus dose of higher than 18 Gy to achieve these goals. Radiosurgical and not microsurgical scales were predictive of clinical outcome after SRS.

Quantitative anatomical analysis and clinical experience with mini-pterional and mini-orbitozygomatic approaches for intracranial aneurysm surgery

J Neurosurg 127:646–659, 2017

The aim of this investigation was to modify the mini-pterional and mini-orbitozygomatic (mini-OZ) approaches in order to reduce the amount of tissue traumatization caused and to compare the use of the 2 approaches in the removal of circle of Willis aneurysms based on the authors’ clinical experience and quantitative analysis.

METHODS Three formalin-fixed adult cadaveric heads injected with colored silicone were examined. Surgical freedom and angle of attack of the mini-pterional and mini-OZ approaches were measured at 9 anatomical points, and the measurements were compared. The authors also retrospectively reviewed the cases of 396 patients with ruptured and unruptured single aneurysms in the circle of Willis treated by microsurgical techniques at their institution between January 2006 and November 2014.

RESULTS A significant difference in surgical freedom was found in favor of the mini-pterional approach for access to the ipsilateral internal carotid artery (ICA) and middle cerebral artery (MCA) bifurcations, the most distal point of the ipsilateral posterior cerebral artery (PCA), and the basilar artery (BA) tip. No statistically significant differences were found between the mini-pterional and mini-OZ approaches for access to the posterior clinoid process, the most distal point of the superior cerebellar artery (SCA), the anterior communicating artery (ACoA), the contralateral ICA bifurcation, and the most distal point of the contralateral MCA. A trend toward increasing surgical freedom was found for the mini-OZ approach to the ACoA and the contralateral ICA bifurcation. The lengths exposed through the mini-OZ approach were longer than those exposed by the mini-pterional approach for the ipsilateral PCA segment (11.5 ± 1.9 mm) between the BA and the most distal point of the P2 segment of the PCA, for the ipsilateral SCA (10.5 ± 1.1 mm) between the BA and the most distal point of the SCA, and for the contralateral anterior cerebral artery (ACA) (21 ± 6.1 mm) between the ICA bifurcation and the most distal point of the A2 segment of the ACA. The exposed length of the contralateral MCA (24.2 ± 8.6 mm) between the contralateral ICA bifurcation and the most distal point of the MCA segment was longer through the mini-pterional approach. The vertical angle of attack (anteroposterior direction) was significantly greater with the minipterional approach than with the mini-OZ approach, except in the ACoA and contralateral ICA bifurcation. The horizontal angle of attack (mediolateral direction) was similar with both approaches, except in the ACoA, contralateral ICA bifurcation, and contralateral MCA bifurcation, where the angle was significantly increased in the mini-OZ approach.

CONCLUSIONS The mini-pterional and mini-OZ approaches, as currently performed in select patients, provide less tissue traumatization (i.e., less temporal muscle manipulation, less brain parenchyma retraction) from the skin to the aneurysm than standard approaches. Anatomical quantitative analysis showed that the mini-OZ approach provides better exposure to the contralateral side for controlling the contralateral parent arteries and multiple aneurysms. The mini-pterional approach has greater surgical freedom (maneuverability) for ipsilateral circle of Willis aneurysms.


Multimodality Treatment of Skull Base Chondrosarcomas

Neurosurgery 81:520–530, 2017

Limited data exist to guide the multimodality management of chondrosarcomas (CSAs) arising in the skull base.

OBJECTIVE : To determine the impact of histological subtype/grade on progression-free survival (PFS) and the indications for surgery, radiation, and chemotherapy based on histology.

METHODS: A retrospective review was performed of 37 patients (conventional type: 81%, mesenchymal: 16.2%, dedifferentiated: 2.7%) treated at The University of Texas M.D. Anderson Cancer Center. Of the conventional subtype, 23% were grade 1, 63% were grade 2, and 14% were grade 3. In addition to surgery, mesenchymal/dedifferentiated CSAs (18% of the cohort) underwent neoadjuvant chemotherapy and 48.6% of the overall cohort received adjuvant radiotherapy. Histological grade/subtype and treatment factors were assessed for impact on median PFS (primary outcome).

RESULTS: Conventional subtype vs mesenchymal/dedifferentiated was positively associated with median PFS (166 vs 24 months, P < .05). Increasing conventional grade inversely correlated with median PFS (P < .05). Gross total resection positively impacted PFS in conventionalCSAs (111.8 vs 42.9months, P=.201) and mesenchymal/dedifferentiated CSAs (58.2 vs 1.0 month, P < .05). Adjuvant radiotherapy significantly impacted PFS in conventional grades 2 and 3 (182 vs 79 months, P < .05) and a positive trend with mesenchymal/dedifferentiated CSAs (43.5 vs 22.0 months). Chemotherapy improved PFS for mesenchymal/dedifferentiated CSAs (50 vs 9 months, P = .089).

CONCLUSION: There is a potential need for histological subtype/grade specific treatment protocols. For conventional CSAs, surgery alone provides optimal results grade 1 CSAs, while resection with adjuvant radiotherapy yields the best outcomefor grade 2 and 3 CSAs. Improvements in PFS seen with neoadjuvant therapy in mesenchymal/dedifferentiated CSAs indicate a potential role for systemic therapies. Larger studies are necessary to confirm the proposed treatment protocols.

Frontal Sinus Breach During Routine Frontal Craniotomy

Neurosurgery 81:504–511, 2017

Frontotemporal craniotomies are commonly performed for a variety of neurosurgical pathologies. Infections related to craniotomies cause significant morbidity. We hypothesized that the risk of cranial surgical site infections (SSIs) may be increased in patients whose frontal sinuses are breached during craniotomy.

OBJECTIVE: To compare the rate of cranial SSIs in patients undergoing frontotemporal craniotomies with and without frontal sinus breach (FSB).

METHODS: We performed a retrospective analysis of all patients undergoing frontotemporal craniotomies for the management of cerebral aneurysms from 2005 to 2014. This study included 862 patients undergoing 910 craniotomies. Primary outcomeof interest was occurrence of a cranial SSI. Standard statistical methods were utilized to explore associations between a variety of variables including FSB, cranial SSI, and infections requiring reoperation.

RESULTS: Of the 910 craniotomies, 141 (15.5%) involved FSB. Of those involving FSB, 22 (15.6%) developed a cranial SSI, compared to only 56 of the 769 without FSB (7.3%; P = .001). Cranial SSI requiring reoperation wasmuch more likely in patients with FSB compared to those without a breach (7.8% vs 1.6%; P < .001). In those presenting with cranial SSIs, epidural abscess formation was more common with FSB compared to no FSB (27.3% vs 5.4%; P = .006). In multivariate analysis, breach of the frontal sinus was significantly associated with cranial SSI (OR 2.16; 95% CI 1.24-3.78; P = .01) and reoperation (OR 4.20; 95% CI 1.66-10.65; P = .003).

CONCLUSION: Patients undergoing frontotemporal craniotomies are at significantly greater risk of serious cranial SSIs if the frontal sinus has been breached.

Nerve atrophy in trigeminal neuralgia due to neurovascular compression and its association with surgical outcomes after microvascular decompression

Acta Neurochir (2017) 159:1699–1705

Idiopathic trigeminal neuralgia (TN) is caused by neurovascular compression and is often related to morphological changes in the trigeminal nerve. The aim of this study was to quantitatively measure atrophic changes of trigeminal nerves in patients with TN, and to further investigate whether nerve atrophy affected the efficacy of microvascular decompression (MVD).

Methods We conducted a prospective case-control study of 60 consecutive patients with TN and 30 sex- and age-matched healthy controls. All subjects underwent high-resolution three-dimensional MRI. The volume of the cisternal segment of trigeminal nerves was measured and compared using 3D Slicer software. Patients with TN underwent primary MVD and regular follow-up for at least 2 years. Associations of nerve atrophy with patient characteristics and operative outcomes were analyzed.

Results The mean volume of the affected trigeminal nerve was significantly reduced in comparison to that of the nonaffected side (65.8 ± 21.1 versus 77.9 ± 19.3 mm3, P = 0.001) and controls (65.8 ± 21.1 versus 74.7 ± 16.5 mm3, P = 0.003). Fifty-two patients (86.7%) achieved complete pain relief without medication immediately after surgery, and 77.6% of patients were complete pain relief at the 2-year follow-up. The Spearman correlation test showed that there was a positive correlation (r=0.46, P = 0.018) between the degree of trigeminal nerve indentation and nerve atrophy. In multivariate logistic regression analysis, two factors, indentation on nerve root (OR = 2.968, P = 0.022) and degree of nerve atrophy (OR = 1.18, P = 0.035), were associated with the long-term outcome.

Conclusions TN is associated with atrophy on the affected nerve. Furthermore, greater nerve atrophy is associated with more severe trigeminal nerve indentation and better long-term outcome following MVD.

Clinical course of untreated thalamic cavernous malformations: hemorrhage risk and neurological outcomes

J Neurosurg 127:480–491, 2017

The natural history of cerebral cavernous malformations (CMs) has been widely studied, but the clinical course of untreated thalamic CMs is largely unknown. Hemorrhage of these lesions can be devastating. The authors undertook this study to obtain a prospective hemorrhage rate and provide a better understanding of the prognosis of untreated thalamic CMs.

METHODS This longitudinal cohort study included patients with thalamic CMs who were diagnosed between 2000 and 2015. Clinical data were recorded, radiological studies were extensively reviewed, and follow-up evaluations were performed.

RESULTS A total of 121 patients were included in the study (56.2% female), with a mean follow-up duration of 3.6 years. The overall annual hemorrhage rate (subsequent to the initial presentation) was calculated to be 9.7% based on the occurrence of 42 hemorrhages over 433.1 patient-years. This rate was highest in patients (n = 87) who initially presented with hemorrhage and focal neurological deficits (FNDs) (14.1%) (c2 = 15.358, p < 0.001), followed by patients (n = 19) with hemorrhage but without FND (4.5%) and patients (n = 15) without hemorrhage regardless of symptoms (1.2%). The initial patient presentations of hemorrhage with FND (hazard ratio [HR] 2.767, 95% CI 1.336–5.731, p = 0.006) and associated developmental venous anomaly (DVA) (HR 2.510, 95% CI 1.275–4.942, p = 0.008) were identified as independent hemorrhage risk factors. The annual hemorrhage rate was significantly higher in patients with hemorrhagic presentation at diagnosis (11.7%, p = 0.004) or DVA (15.7%, p = 0.002). Compared with the modified Rankin Scale (mRS) score at diagnosis (mean 2.2), the final mRS score (mean 2.0) was improved in 37 patients (30.6%), stable in 59 patients (48.8%), and worse in 25 patients (20.7%). Lesion size (odds ratio [OR] per 0.1 cm increase 3.410, 95% CI 1.272–9.146, p = 0.015) and mRS score at diagnosis (OR per 1 point increase 3.548, 95% CI 1.815–6.937, p < 0.001) were independent adverse risk factors for poor neurological outcome (mRS score ≥ 2). Patients experiencing hemorrhage after the initial ictus (OR per 1 ictus increase 6.923, 95% CI 3.023–15.855, p < 0.001) had a greater chance of worsened neurological status.

CONCLUSIONS This study verified the adverse predictors for hemorrhage and functional outcomes of thalamic CMs and demonstrated an overall annual symptomatic hemorrhage rate of 9.7% after the initial presentation. These findings and the mode of initial presentation are useful for clinicians and patients when selecting an appropriate treatment, although the tertiary referral bias of the series should be taken into account.

Which Cerebral Cavernous Malformations are Most Difficult to Dissect From Surrounding Eloquent Brain Tissue?

Neurosurgery 81:498–503, 2017

Cerebral cavernous malformations (CCM) may lead to repetitive intracerebral hemorrhage. In selected cases, a surgical resection is indicated.

OBJECTIVE: To identify magnetic resonance imaging (MRI) features of CCM that correlate with the difficulty of dissection and postoperative outcome.

METHODS: This study prospectively analyzed pre- and postoperative MRI features, intraoperative findings (surgical questionnaire), and postoperative outcome of 41 patients with eloquent CCM. Based on the results of the surgeon’s questionnaire and postoperative MRI findings, all surgical procedureswere dichotomized in a “difficult”(groupA) or “not difficult” (group B) lesion dissection. Based on the correlation of preoperative MRI features with groups A and B, a 3-tiered classification was established and tested for sensitivity and specificity.

RESULTS: In 22 patients, dissection of the lesion was rated difficult. This was significantly correlated with amount of postoperative diffusion restriction on MRI (P=.001) and postoperative outcome(P=.05). Various preoperative MRI featureswere tested for correlation and combined in a 3-tiered classification. Receiver operating characteristics revealed excellent and good results for predicting difficulty of dissection for the different classification types.

CONCLUSION: We provide a meticulous analysis and new classification of preoperative MRI features that seem to be involved in the microsurgical resection of CCM.

Early retreatment after surgical clipping of ruptured intracranial aneurysms

Acta Neurochir (2017) 159:1627–1632

Although a rerupture after surgical clipping of ruptured intracranial aneurysms is rare, it is associated with high morbidity and mortality. The causes for retreatment and rupture after surgical clipping are not clearly defined.

Methods From a prospectively maintained database of 244 patients who had undergone surgical clipping of ruptured intracranial aneurysms, we selected patients who experienced retreatment or rerupture within 30 days after surgical clipping. Aneurysm occlusions were examined by microvascular Doppler ultrasonography and indocyanine green video-angiography. Indications for retreatment included rerupture and partial occlusion. We analyzed the characteristics and causes of early retreatment.

Results Six patients (2.5%, 95% CI 0.9 to 5.3%) were retreated within 30 days after surgical clipping, including two patients (0.8%, 95% CI 0.1 to 2.9%) who experienced a rerupture. The retreated aneurysms were found in the anterior communicating artery (AcomA) (n = 5) and basilar artery (n = 1). Retreatment of the AcomA (7.5%) was performed significantly more frequently than that of other arteries (0.56%) (p < 0.01). A laterally projected AcomA aneurysm (17.4%) was more frequently retreated than were other aneurysm types (2.3%). Cases of laterally projecting AcomA aneurysms tended to result from an incomplete clip placed using a pterional approach from the opposite side of the aneurysm projection.

Conclusions Despite developments, the rates of retreatment and rerupture after surgical clipping remain similar to those reported previously. Retreatment of the AcomA was significantly more frequent than was retreatment of other arteries. Patients underwent retreatment more frequently when they were originally treated for lateral type aneurysms using a pterional approach from the opposite side of the aneurysm projection. The treatment method and evaluation modalities should be considered carefully for AcomA aneurysms in particular.

Exploring the brain through posterior hypothalamus surgery for aggressive behavior

Neurosurg Focus 43 (3):E14, 2017

Neurological surgery offers an opportunity to study brain functions, through either resection or implanted neuromodulation devices. Pathological aggressive behavior in patients with intellectual disability is a frequent condition that is difficult to treat using either supportive care or pharmacological therapy.

The bulk of the laboratory studies performed throughout the 19th century enabled the formulation of hypotheses on brain circuits involved in the generation of emotions.

Aggressive behavior was also studied extensively. Lesional radiofrequency surgery of the posterior hypothalamus, which peaked in the 1970s, was shown to be an effective therapy in many reported series. As with other surgical procedures for the treatment of psychiatric disorders, however, this therapy was abandoned for many reasons, including the risk of its misuse.

Deep brain stimulation (DBS) offers the possibility of treating neurological and psychoaffective disorders through relatively reversible and adaptable therapy. Deep brain stimulation of the posterior hypothalamus was proposed and performed successfully in 2005 as a treatment for aggressive behavior. Other groups reported positive outcomes using target and parameter settings similar to those of the original study. Both the lesional and DBS approaches enabled researchers to explore the role of the posterior hypothalamus (or posterior hypothalamic area) in the autonomic and emotional systems.


Endoscopic endonasal transclival resection of a ventral pontine cavernous malformation

J Neurosurg 127:553–558, 2017

Brainstem cavernous malformations are challenging due to the critical anatomy and potential surgical risks. Anterolateral, lateral, and dorsal surgical approaches provide limited ventral exposure of the brainstem.

The authors present a case of a midline ventral pontine cavernous malformation resected through an endoscopic endonasal transclival approach based on minimal brainstem transection, negligible cranial nerve manipulation, and a straightforward trajectory.

Technical and reconstruction technique advances in endoscopic endonasal skull base surgery provide a direct, safe, and effective corridor to the brainstem.

Surgical management of spinal osteoblastomas

J Neurosurg Spine 27:321–327, 2017

Osteoblastoma is a rare primary benign bone tumor with a predilection for the spinal column. Although of benign origin, osteoblastomas tend to behave more aggressively clinically than other benign tumors. Because of the low incidence of osteoblastomas, evidence-based treatment guidelines and high-quality research are lacking, which has resulted in inconsistent treatment. The goal of this study was to determine whether application of the Enneking classification in the management of spinal osteoblastomas influences local recurrence and survival time.

METHODS A multicenter database of patients who underwent surgical intervention for spinal osteoblastoma was developed by the AOSpine Knowledge Forum Tumor. Patient data pertaining to demographics, diagnosis, treatment, crosssectional survival, and local recurrence were collected. Patients in 2 cohorts, based on the Enneking classification of the tumor (Enneking appropriate [EA] and Enneking inappropriate [EI]), were analyzed. If the final pathology margin matched the Enneking-recommended surgical margin, the tumor was classified as EA; if not, it was classified as EI.

RESULTS A total of 102 patients diagnosed with a spinal osteoblastoma were identified between November 1991 and June 2012. Twenty-nine patients were omitted from the analysis because of short follow-up time, incomplete survival data, or invalid staging, which left 73 patients for the final analysis. Thirteen (18%) patients suffered a local recurrence, and 6 (8%) patients died during the study period. Local recurrence was strongly associated with mortality (relative risk 9.2; p = 0.008). When adjusted for Enneking appropriateness, this result was not altered significantly. No significant differences were found between the EA and EI groups in regard to local recurrence and mortality.

CONCLUSIONS In this evaluation of the largest multicenter cohort of spinal osteoblastomas, local recurrence was found to be strongly associated with mortality. Application of the Enneking classification as a treatment guide for preventing local recurrence was not validated.

Preservation of hearing following awake surgery via the retrosigmoid approach for vestibular schwannomas in eight consecutive patients

Acta Neurochir (2017) 159:1579–1585

Hearing preservation in patients with vestibular schwannomas remains difficult by microsurgery or radiosurgery.

Method: In this study, awake surgery via the retrosigmoid approach was performed for vestibular schwannomas (volume, 11.6 ± 11.2 ml; range, 1.3–26.4 ml) in eight consecutive patients with preoperative quartering of pure tone audiometry (PTA) of 53 ± 27 dB.

:Results After surgery, hearing was preserved in seven patients and improved in one patient. The postoperative quartering PTA was 51 ± 21 dB. Serviceable hearing (class A + B + C) using the American Association of Otolaryngology-Head and Neck Surgery (AAO-HNS) classification was preserved in all patients. Preoperative useful hearing (AAO-HNS class A + B) was observed in three patients, and useful hearing was preserved in all three of these patients after surgery. In addition, useful facial nerve function (House-Blackmann Grade 1) was preserved in all patients.

:Conclusions These results suggest that awake surgery for vestibular schwannomas is associated with low patient morbidity, including with respect to hearing and facial nerve function.

Cystic Vestibular Schwannomas Respond Best to Radiosurgery

Neurosurgery 81:490–497, 2017

Vestibular schwannomas (VS) have a well-documented response to Gamma Knife R  (Elekta AB, Stockholm, Sweden) Stereotactic radiosurgery (SRS). However, there are limited data available regarding the volumetric response of cystic tumors.

OBJECTIVE: This report correlates the radiographic appearance of VS before radiosurgery with the delayed volumetric response.

METHODS: This study reviewed our SRS experience with 219 VS patients between 2003 and 2013. Patients were treatment naïve and had a significant extracanalicular tumor volume. Magnetic resonance imaging at the time of SRS identified 42 contrast-enhancing macrocystic tumors, 45 contrast-enhancing microcystic tumors, and 132 homogeneously enhancing tumors with no intratumoral cyst formation. The median follow-up was 49.1 months. The median tumor volume was 2.6 cm3 (0.70-16.1 cm3) and the median dose was 12.5 Gy (11-13 Gy).

RESULTS: The actuarial tumor control rate was 99.4% at 2 years and 96.4% at 5 years. A volumetric reduction of >20% occurred in 85.4% of macrocystic tumors, 76.1% of microcystic tumors, and 62.8% of homogeneously enhancing VS. The median volume decrease per year for macrocystic, microcystic, and homogenous tumors was 17.2%, 7.5%, and 7.9% per year respectively (P < .001). A 2:1 blinded volumetric case match showed a significant size reduction in macrocystic tumors compared to noncystic tumors (P = .007). Serviceable hearing was maintained in 61.5% of patients that had Gardner-Robertson grade I-II hearing before treatment. Surgical resection or repeat radiosurgery was performed in 8 patients (3.6%) who had sustained tumor progression.

CONCLUSION: SRS provided VS tumor control in >95% of patients, regardless of radiographic characteristics. Tumor volume regression was most evident in patients with cystic tumors.

Spinal navigation for posterior instrumentation of C1–2 instability using a mobile intraoperative CT scanner

J Neurosurg Spine 27:268–275, 2017

Spinal navigation techniques for surgical fixation of unstable C1–2 pathologies are challenged by complex osseous and neurovascular anatomy, instability of the pathology, and unreliable preoperative registration techniques. An intraoperative CT scanner with autoregistration of C-1 and C-2 promises sufficient accuracy of spinal navigation without the need for further registration procedures. The aim of this study was to analyze the accuracy and reliability of posterior C1–2 fixation using intraoperative mobile CT scanner–guided navigation.

METHODS In the period from July 2014 to February 2016, 10 consecutive patients with instability of C1–2 underwent posterior fixation using C-2 pedicle screws and C-1 lateral mass screws, and 2 patients underwent posterior fixation from C-1 to C-3. Spinal navigation was performed using intraoperative mobile CT. Following navigated screw insertion in C-1 and C-2, intraoperative CT was repeated to check for the accuracy of screw placement. In this study, the accuracy of screw positioning was retrospectively analyzed and graded by an independent observer.

RESULTS The authors retrospectively analyzed the records of 10 females and 2 males, with a mean age of 80.7 ± 4.95 years (range 42–90 years). Unstable pathologies, which were verified by fracture dislocation or by flexion/extension radiographs, included 8 Anderson Type II fractures, 1 unstable Anderson Type III fracture, 1 hangman fracture Levine Effendi Ia, 1 complex hangman-Anderson Type III fracture, and 1 destructive rheumatoid arthritis of C1–2. In 4 patients, critical anatomy was observed: high-riding vertebral artery (3 patients) and arthritis-induced partial osseous destruction of the C-1 lateral mass (1 patient). A total of 48 navigated screws were placed. Correct screw positioning was observed in 47 screws (97.9%). Minor pedicle breach was observed in 1 screw (2.1%). No screw displacement occurred (accuracy rate 97.9%).

CONCLUSION Spinal navigation using intraoperative mobile CT scanning was reliable and safe for posterior fixation in unstable C1–2 pathologies with high accuracy in this patient series.

Awake Craniotomy vs Craniotomy Under General Anesthesia for Perirolandic Gliomas

Neurosurgery 81:481–489, 2017

A craniotomy with direct cortical/subcortical stimulation either awake or under general anesthesia (GA) present 2 approaches for removing eloquent region tumors. With a reported higher prevalence of intraoperative seizures occurring during awake resections of perirolandic lesions, oftentimes, surgery under GA is chosen for these lesions.

OBJECTIVE: To evaluate a single-surgeon’s experience with awake craniotomies (AC) vs surgery under GA for resecting perirolandic, eloquent, motor-region gliomas.

METHODS: Between 2005 and 2015, a retrospective analysis of 27 patients with perirolandic, eloquent, motor-area gliomas that underwent an AC were case-control matched with 31 patients who underwent surgery under GA for gliomas in the same location. All patients underwent direct brain stimulation with neuromonitoring and perioperative risk factors, extent of resection, complications, and discharge status were assessed.

RESULTS: The postoperative Karnofsky Performance Score (KPS) was significantly lower for theGApatients at 81.1 compared to theACpatients at 93.3 (P=.040). The extent of resection for GA patients was 79.6% while the AC patients had an 86.3% resection (P = .136). There were significantly more 100% total resections in the AC patients 25.9% compared to the GA group (6.5%; P=.041). Patients in theGAgroup had a longer mean length of hospitalization of 7.9 days compared to the AC group at 4.2 days (P = .049).

CONCLUSION: We show that AC can be performed with more frequent total resections, better postoperative KPS, shorter hospitalizations, as well as similar perioperative complication rates compared to surgery under GA for perirolandic, eloquent motor-region glioma.

Image-guided endoscopic surgery for spontaneous supratentorial intracerebral hematoma

J Neurosurg 127:537–542, 2017

Endoscopic removal of intracerebral hematomas is becoming increasingly common, but there is no standard technique. The authors explored the use of a simple image-guided endoscopic method for removal of spontaneous supratentorial hematomas.

METHODS Virtual reality technology based on a hospital picture archiving and communications systems (PACS) was used in 3D hematoma visualization and surgical planning. Augmented reality based on an Android smartphone app, Sina neurosurgical assist, allowed a projection of the hematoma to be seen on the patient’s scalp to facilitate selection of the best trajectory to the center of the hematoma. A obturator and transparent sheath were used to establish a working channel, and an endoscope and a metal suction apparatus were used to remove the hematoma.

RESULTS A total of 25 patients were included in the study, including 18 with putamen hemorrhages and 7 with lobar cerebral hemorrhages. Virtual reality combined with augmented reality helped in achieving the desired position with the obturator and sheath. The median time from the initial surgical incision to completion of closure was 50 minutes (range 40–70 minutes). The actual endoscopic operating time was 30 (range 15–50) minutes. The median blood loss was 80 (range 40–150) ml. No patient experienced postoperative rebleeding. The average hematoma evacuation rate was 97%. The mean (± SD) preoperative Glasgow Coma Scale (GCS) score was 6.7 ± 3.2; 1 week after hematoma evacuation the mean GCS score had improved to 11.9 ± 3.1 (p < 0.01).

CONCLUSIONS Virtual reality using hospital PACS and augmented reality with a smartphone app helped precisely localize hematomas and plan the appropriate endoscopic approach. A transparent sheath helped establish a surgical channel, and an endoscope enabled observation of the hematoma’s location to achieve satisfactory hematoma removal.

The midline suboccipital subtonsillar approach to the cerebellomedullary cistern

Acta Neurochir (2017) 159:1613–1617

Lesions lateral to the lower brainstem in an area extending from the foraminae of Luschka to the foramen magnum are rare and include different pathologies. There is no consensus on an ideal surgical approach.

Method: To gain access to this area, we use the midline suboccipital subtonsillar approach (STA). This midline approach with unilateral retraction of the cerebellar tonsil enables entry into the cerebellomedullary cistern.

Conclusions: The STA offers excellent access with a panoramic view of the cerebellomedullary cistern and its structures and therefore can be useful for a number of different pathologies in the lower petroclival area.

Tractography guides the approach for resection of thalamopeduncular tumors

Acta Neurochir (2017) 159:1597–1601

Thalamopeduncular tumors arise at the junction of the inferior thalamus and cerebral peduncle, and present with a common clinical syndrome of progressive spastic hemiparesis.

Method Formal preoperative magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) were performed. Postoperative MRI was obtained to evaluate the extent of tumor resection. A prospective analysis of clinical outcomes was then conducted by the senior author.

Conclusions Preoperative tractography is a useful adjunct to surgical planning in tumors that displace motor pathways. Gross total resection of pilocytic astrocytomas usually results in cure, and therefore should be entertained when developing treatment strategies for thalamopeduncular tumors of childhood.

Bypass surgery for complex middle cerebral artery aneurysms: an algorithmic approach to revascularization

J Neurosurg 127:463–479, 2017

Management of complex aneurysms of the middle cerebral artery (MCA) can be challenging. Lesions not amenable to endovascular techniques or direct clipping might require a bypass procedure with aneurysm obliteration. Various bypass techniques are available, but an algorithmic approach to classifying these lesions and determining the optimal bypass strategy has not been developed. The objective of this study was to propose a comprehensive and flexible algorithm based on MCA aneurysm location for selecting the best of multiple bypass options.

METHODS Aneurysms of the MCA that required bypass as part of treatment were identified from a large prospectively maintained database of vascular neurosurgeries. According to its location relative to the bifurcation, each aneurysm was classified as a prebifurcation, bifurcation, or postbifurcation aneurysm.

RESULTS Between 1998 and 2015, 30 patients were treated for 30 complex MCA aneurysms in 8 (27%) prebifurcation, 5 (17%) bifurcation, and 17 (56%) postbifurcation locations. Bypasses included 8 superficial temporal artery–MCA bypasses, 4 high-flow extracranial-to-intracranial (EC-IC) bypasses, 13 IC-IC bypasses (6 reanastomoses, 3 reimplantations, 3 interpositional grafts, and 1 in situ bypass), and 5 combination bypasses. The bypass strategy for prebifurcation aneurysms was determined by the involvement of lenticulostriate arteries, whereas the bypass strategy for bifurcation aneurysms was determined by rupture status. The location of the MCA aneurysm in the candelabra (Sylvian, insular, or opercular) determined the bypass strategy for postbifurcation aneurysms. No deaths that resulted from surgery were found, bypass patency was 90%, and the condition of 90% of the patients was improved or unchanged at the most recent follow-up.

CONCLUSIONS The bypass strategy used for an MCA aneurysm depends on the aneurysm location, lenticulostriate anatomy, and rupture status. A uniform bypass strategy for all MCA aneurysms does not exist, but the algorithm proposed here might guide selection of the optimal EC-IC or IC-IC bypass technique.

Neurosurgery Department. “La Fe” University Hospital. Valencia, Spain


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