How I do it: simplified craniotomy for acute subdural hematoma in the elderly.

CONTEXT: Acute subdural hematoma (ASH) is responsible for significant morbidity and mortality in the elderly. As military neurosurgeons, we perform a simplified technique using a linear skin incision and a small craniotomy bone flap in order to ease perioperative tolerance. METHODS: The patient lies supine, a pad under the shoulder ipsilateral to the ASH, the head completely rotated on the other side and placed on a circular pad, without head clamp. The linear frontotemporal skin incision should be twice the size of the bone flap's diameter, allowing to access the whole subdural space. Care is taken to obtain complete decompression of the temporal fossa in order to alleviate uncal herniation. A subdural drain can be placed, and the subdural space is filled with warm saline solution in order to create a closed drainage system. CONCLUSION: The patient is allowed to sit at postoperative day 1 and to walk at postoperative day 2. Simplified craniotomy for ASH allows to reduce operative time and provides faster functional recovery.

Reducing morbidity associated with subdural drain placement after burr-hole drainage of unilateral chronic subdural hematomas: a retrospective series comparing conventional and modified Nelaton catheter techniques.

PURPOSE: Placement of a subdural drain after burr-hole drainage of chronic subdural hematoma (cSDH) significantly reduces risk of its recurrence and lowers mortality at 6 months. Nonetheless, measures to reduce morbidity related to drain placement are rarely addressed in the literature. Toward reducing drain-related morbidity, we compare outcomes achieved by conventional insertion and our proposed modification. METHODS: In this retrospective series from two institutions, 362 patients underwent burr-hole drainage of unilateral cSDH with subsequent subdural drain insertion by conventional technique or modified Nelaton catheter (NC) technique. Primary endpoints were iatrogenic brain contusion or new neurological deficit. Secondary endpoints were drain misplacement, indication for computed tomography (CT) scan, re-operation for hematoma recurrence, and favorable Glasgow Outcome Scale (GOS) score (≥ 4) at final follow-up. RESULTS: The 362 patients (63.8% male) in our final analysis included drains inserted in 56 patients by NC and 306 patients by conventional technique. Brain contusions or new neurological deficits occurred significantly less often in the NC (1.8%) than conventional group (10.5%) (P = .041). Compared with the conventional group, the NC group had no drain misplacement (3.6% versus 0%; P = .23) and significantly fewer non-routine CT imaging related to symptoms (36.5% versus 5.4%; P < .001). Re-operation rates and favorable GOS scores were comparable between groups. CONCLUSION: We propose the NC technique as an easy-to-use measure for accurate drain positioning within the subdural space that may yield meaningful benefits for patients undergoing treatment for cSDH and vulnerable to complication risks.

Subdural open drains as an effective and low-cost modality for the treatment of chronic subdural hematomas.

PURPOSE: We present a series that describes the presenting features and clinical outcomes in patients with CSDH treated with a standardised technique and an open-drain placement. METHODS: We reviewed the medical records of 155 consecutive patients at a single centre who underwent CSDH evacuation by placing burr holes, accompanied by intraoperative irrigation and a subdural Penrose drain between 2014 and 2018. RESULTS: The mean age was 65.9 years, 81.9% were males. The most common clinical characteristics were an altered mental state (21.9%) and headache (12.9%). It was necessary to perform a second surgical intervention due to the evidence in the postoperative tomography of a residual hematoma in 10.3% of the cases; there were 2 cases of recurrence in 6 months (1.3%). Pneumonia (6.5%) and seizures (5.8%) were the most frequent medical complications. Intracranial infections accounted for 1.9%, and the mortality rate was 6.4% of cases. CONCLUSIONS: We provided our experience with a low-cost and less-commonly used technique in the management of CSDH. This technique showed similar recurrence, mortality and intracranial infection rates to those reported in the literature for closed drainage systems. Additional studies will be required to assess this technique.

Epidural and subdural interdural approach to the lateral wall of the cavernous sinus for preserving the laterocavernous sinus in trigeminal schwannoma.

Evacuation of middle fossa trigeminal schwannomas (TS) warrants a subtemporal interdural approach through the lateral wall of the cavernous sinus (CS). The dura comprises the dura propria, which follows the trigeminal nerve and develops into the epineurium, and periosteal layer. The interdural approach involves peeling off the dura propria and exposing the epineural sheath. The venous route around the CS is often obstructed due to TS progression. The interdural approach based on venous route preservation remains to be discussed. The laterocavernous sinus (LCS) is formed in these layers, draining to either the medial or lateral route. In the lateral route, the LCS drains to the pterygoid plexus via the middle cranial fossa foramen. Exposure of the interdural space disturbs the lateral route's venous flow. We describe an operative strategy for venous route preservation in TS via the LCS lateral route. The venous route can be preserved by peeling off the dura propria from the posterior end of the foramen ovale short of the venous drainage route to the pterygoid plexus epidurally and then cutting from the middle cranial fossa dura posterior to the venous route subdurally to the exposed interdural space. This technique helps in avoiding postoperative venous complications.

Reducing meningo-cerebral adhesions by implanting an interpositional subdural polyesterurethane graft after high-grade glioma resection.

BACKGROUND: Meningo-cerebral adhesions are frequently encountered during recurrent high-grade glioma resections. Adhesiolysis not only lengthens operation times, but can also induce focal cortical tissue injury that could affect overall survival. METHODS: Immediately after the primary resection of a high-grade glioma, a polyesterurethane interpositional graft was implanted in the subdural space covering the entire exposed cortex as well as beneath the dural suture line. No postoperative complications were documented. All patients received adjuvant radiotherapy. Upon repeat resection for focal tumor recurrence, the graft was shown to effectively reduce meningo-cerebral adhesion development. CONCLUSION: The implantation of a synthetic subdural graft is a safe and effective method for preventing meningo-cerebral adhesions.

Subdural drainage techniques for single burr-hole evacuation of chronic subdural hematoma: two drains frontal-occipital position versus one drain frontal position.

OBJECTIVE: Burr-hole craniostomy with a closed drainage system is the most commonly used technique for chronic subdural hematoma(CSDH), but the reoperation rate for hematoma recurrence is still high. This retrospective study aimed to compare the complications and recurrence of two subdural drains placement with tips frontal-occipital position (TFOP) versus one subdural drain placement with tip frontal position(OFP) following single burr-hole evacuation for the treatment of chronic subdural hematoma(CSDH). METHODS: The authors analyzed data of all CSDH patients who underwent single burr-hole surgery with placement of subdural closed-drainage system(TFOP or OFP techniques) between January 2013 and December 2017. Data analysis included general patient data, complications, recurrence and clinical outcome. RESULTS: A total of 331 patients were included(85 TFOP and 246 OFP). The TFOP group and OFP group were statistically comparable with respect to baseline characteristics except for preoperative Markwalder score (p = 0.019). Midline shift and subdural fluid thickness on first postoperative day were greater in OFP group than the TFOP group (p = 0.028; and p = 0.007, respectively). In addition, patients with OFP had a lower percent of hematoma change after surgery and much more residual subdural air than those with TFOP (p = 0.001; and p < 0.001, respectively). Postoperative complications and clinical outcome between the two groups showed no significant differences. During the 3-month follow-up, the rate of hematoma recurrence was significantly lower among patients treated with TFOP than those treated with OFP (p = 0.039). CONCLUSIONS: The postoperative complications rate did not differ between TFOP group and OFP group for patients with CSDH. Considering the lower rate of recurrence, TFOP following single burr-hole evacuation might be a safe and promising option for CSDH treatment.

Further evidence for a continuous flux of bile acids into the brain: trapping of bile acids in subdural hematomas.

Bile acids are known to pass the blood-brain barrier and are present at low concentrations in the brain. In a previous work, it was shown that subdural hematomas are enriched with bile acids and that the levels in such hematomas are higher than in the peripheral circulation. The mechanism behind this enrichment was never elucidated. Bile acids have a high affinity to albumin, and subdural hematomas contain almost as high albumin levels as the peripheral circulation. A subdural hematoma is encapsulated by fibrin which may allow passage of small molecules like bile acids. We hypothesized that bile acids originating from the circulation may be 'trapped' in the albumin in subdural hematomas. In the present work, we measured the conjugated and unconjugated primary bile acids cholic acid and chenodeoxycholic acid in subdural hematomas and in peripheral circulation of 24 patients. In most patients, the levels of both conjugated and free bile acids were higher in the hematomas than in the circulation, but the enrichment of unconjugated bile acids was markedly higher than that of conjugated bile acids. In patients with a known time interval between the primary bleeding and the operation, there was a correlation between this time period and the accumulation of bile acids. This relation was most obvious for unconjugated bile acids. The results are consistent with a continuous flux of bile acids, in particular unconjugated bile acids, across the blood-brain barrier. We discuss the possible physiological importance of bile acid accumulation in subdural hematomas.

Drain type after burr-hole drainage of chronic subdural hematoma in geriatric patients: a subanalysis of the cSDH-Drain randomized controlled trial.

OBJECTIVE: Chronic subdural hematoma (cSDH) occurs more frequently in elderly patients, while older patient age is associated with worse postoperative outcome following burr-hole drainage (BHD) of cSDH. The cSDH-Drain trial showed comparable recurrence rates after BHD and placement of either a subperiosteal drain (SPD) or subdural drain (SDD). Additionally, an SPD showed a significantly lower rate of infections as well as iatrogenic parenchymal injuries through drain misplacement. This post hoc analysis aims to compare recurrence rates and clinical outcomes following BHD of cSDH and the placement of SPDs or SDDs in elderly patients. METHODS: The study included 104 patients (47.3%) 80 years of age and older from the 220 patients recruited in the preceding cSDH-Drain trial. SPDs and SDDs were compared with regard to recurrence rate, morbidity, mortality, and clinical outcome. A post hoc analysis using logistic regression, comparing the outcome measurements for patients < 80 and ≥ 80 years old in a univariate analysis and stratified for drain type, was further completed. RESULTS: Patients ≥ 80 years of age treated with an SDD showed higher recurrence rates (12.8%) compared with those treated with an SPD (8.2%), without a significant difference (p = 0.46). Significantly higher drain misplacement rates were observed for patients older than 80 years and treated with an SDD compared with an SPD (0% vs 20%, p = 0.01). Comparing patients older than 80 years to younger patients, significantly higher overall mortality (15.4% vs 5.2%, p = 0.012), 30-day mortality (3.8% vs 0%, p = 0.033), and surgical mortality (2.9% vs 1.7%, p = 0.034) rates were observed. Clinical outcome at the 12-month follow-up was significantly worse for patients ≥ 80 years old, and logistic regression showed a significant association of age with outcome, while drain type had no association with outcome. CONCLUSIONS: The initial findings of the cSDH-Drain trial and the findings of this subanalysis suggest that SPD may be warranted in elderly patients. As opposed to drain type, patient age (> 80 years) was significantly associated with worse outcome, as well as higher morbidity and mortality rates.

Burr hole trepanation and insertion of a subperiosteal drain for chronic subdural haematoma: how I do it.

BACKGROUND: Burr hole trepanation (BHT) is the most commonly used surgical method for the treatment of chronic subdural haematoma (cSDH). METHOD: We give a brief overview on the indication for surgical treatment of cSDH, the surgical technique of BHT, and specific perioperative considerations. In particular, we emphasise on the technique of a subperiosteal drain placement. CONCLUSION: BHT is a valid option to treat chronic subdural haematoma. Careful surgical technique and placement of a subperiosteal drain is required to minimise complications and improve outcome.

Drains result in greater reduction of subdural width and midline shift in burr hole evacuation of chronic subdural haematoma.

BACKGROUND: Drain insertion following chronic subdural haematoma (CSDH) evacuation reduces recurrence and improves outcomes. The mechanism of this improvement is uncertain. We assessed whether drains result in improved postoperative imaging, and which radiological factors are associated with recurrence and functional outcome. METHODS: A multi-centre, prospective cohort study of CSDH patients was performed between May 2013 and January 2014. Patients aged > 16 years undergoing burr hole evacuation of primary CSDH with pre- and postoperative imaging were included in this subgroup analysis. Baseline and clinical details were collected. Pre- and postoperative maximal subdural width and midline shift (MLS) along with clot density were recorded. Primary outcomes comprised mRS at discharge and symptomatic recurrence requiring re-drainage. Comparisons were made using multiple logistic regression. RESULTS: Three hundred nineteen patients were identified for inclusion. Two hundred seventy-two of 319 (85%) patients underwent drain insertion at the time of surgery versus 45/319 (14%) who did not. Twenty-nine of 272 patients who underwent drain insertion experienced recurrence (10.9%) versus 9 of 45 patients without drain insertion (20.5%; p = 0.07). Overall change in median subdural width was significantly greater in the drain versus 'no drain' groups (11 mm versus 6 mm, p < 0.01). Overall change in median midline shift (MLS) was also significantly greater in the drain group (4 mm versus 3 mm, p < 0.01). On multivariate analysis, change in maximal width and MLS were significant predictors of recurrence, although only the former remained a significant predictor for functional outcome. CONCLUSIONS: The use of subdural drains results in significantly improved postoperative imaging in burr hole evacuation of CSDH, thus providing radiological corroboration for their recommended use.

Subperiosteal versus subdural drainage after burr hole evacuation of chronic subdural hematoma: systematic review and meta-analysis.

BACKGROUND: The evidence for subperiosteal drainage (SPD) versus subdural drainage (SDD) in chronic subdural hematoma (CSDH) remains controversial, and most surgeons prefer to use SDD over SPD. We aim to assess the latest evidence on the use of SPD compared to SDD in patients with CSDH undergoing burr hole evacuation. METHODS: We performed a systematic literature search on topics that assesses the use of SPD compared to SDD in patients with CSDH up until November 2019 from PubMed, EuropePMC, Cochrane Central Database, ScienceDirect, ProQuest, and ClinicalTrials.gov. The primary outcome was recurrent CSDH, and the secondary outcomes were mortality, surgical morbidities, and modified Rankin Score (mRS). RESULTS: There were a total of 3241 subjects from 10 studies. SPD was shown to reduce recurrent CSDH (OR 0.66 [0.52, 0.84], p < 0.001; I2: 17%, p = 0.30) compared to SDD. Recurrent CSDH was lower in SPD group in subgroup analysis at 3-months (OR 0.63 [0.49, 0.81]; I2: 68%, p = 0.04) and 6-months (OR 0.66 [0.51, 0.85], p = 0.001; I2: 77%, p = 0.01) follow-up. However, there was no difference in CSDH recurrence upon subgroup analysis of RCTs. Similar mortality was demonstrated between SPD and SDD group (p = 0.13). The occurrence of parenchymal injury/new neurological deficit was significantly lower in SPD group (OR 0.26 [0.14, 0.51], p < 0.001; I2: 49%, p = 0.08). The rate of seizure, (p = 0.57), postoperative bleeding (p = 0.29), and infection (p = 0.25) were shown to be similar in both SPD and SDD group. Overall, the rate of surgical morbidity was significantly lower in SPD group (OR 0.61 [0.44, 0.85], p = 0.003; I2: 16%, p = 0.25). mRS at the end of follow-up was similar in SPD and SDD group (p = 0.12). CONCLUSION: SPD was associated with less CSDH recurrence, but similar rate of mortality, seizures, postoperative bleeding, and infections compared to SDD. The rate of parenchymal injury/new neurological deficit was lower in the SPD group.

Drain type and technique for subdural insertion after burr hole evacuation of chronic subdural hematoma.

Strengths and limitations of subdural versus subperiosteal drain location after burr hole evacuation of chronic subdural hematoma (CSDH) are currently debated. The safety of subdural placement of a drain has been questioned in a recent study by Soleman et al. from 2019, showing a misplacement rate of 17%, and these results have been further highlighted by the same authors, with a slightly lower misplacement rate of 15.8%, in the recent paper "When the drain hits the brain." The safety of subdural drainage for CSDH depends to a high degree on type of drain and surgical technique. In this technical note, we describe drain type and technique for drain placement which is standardized in Denmark.

Invasive EEG-electrodes in presurgical evaluation of epilepsies: Systematic analysis of implantation-, video-EEG-monitoring- and explantation-related complications, and review of literature.

INTRODUCTION: Stereoelectroencephalography (sEEG) is a diagnostic procedure for patients with refractory focal epilepsies that is performed to localize and define the epileptogenic zone. In contrast to grid electrodes, sEEG electrodes are implanted using minimal invasive operation techniques without large craniotomies. Previous studies provided good evidence that sEEG implantation is a safe and effective procedure; however, complications in asymptomatic patients after explantation may be underreported. The aim of this analysis was to systematically analyze clinical and imaging data following implantation and explantation. RESULTS: We analyzed 18 consecutive patients (mean age: 30.5 years, range: 12-46; 61% female) undergoing invasive presurgical video-EEG monitoring via sEEG electrodes (n = 167 implanted electrodes) over a period of 2.5 years with robot-assisted implantation. There were no neurological deficits reported after implantation or explantation in any of the enrolled patients. Postimplantation imaging showed a minimal subclinical subarachnoid hemorrhage in one patient and further workup revealed a previously unknown factor VII deficiency. No injuries or status epilepticus occurred during video-EEG monitoring. In one patient, a seizure-related asymptomatic cross break of two fixation screws was found and led to revision surgery. Unspecific symptoms like headaches or low-grade fever were present in 10 of 18 (56%) patients during the first days of video-EEG monitoring and were transient. Postexplantation imaging showed asymptomatic and small bleedings close to four electrodes (2.8%). CONCLUSION: Overall, sEEG is a safe and well-tolerated procedure. Systematic imaging after implantation and explantation helps to identify clinically silent complications of sEEG. In the literature, complication rates of up to 4.4% in sEEG and in 49.9% of subdural EEG are reported; however, systematic imaging after explantation was not performed throughout the studies, which may have led to underreporting of associated complications.

Craniotomy Size for Subdural Grid Electrode Placement in Invasive Epilepsy Diagnostics.

BACKGROUND: Traditionally, for subdural grid electrode placement, large craniotomies have been applied for optimal electrode placement. Nowadays, microneurosurgeons prefer patient-tailored minimally invasive approaches. Absolute figures on craniotomy size have never been reported. To elucidate the craniotomy size necessary for successful diagnostics, we reviewed our single-center experience. METHODS: Within 3 years, 58 patients with focal epilepsies underwent subdural grid implantation using patient-tailored navigation-based craniotomies. Craniotomy sizes were measured retrospectively. The number of electrodes and the feasibility of the resection were evaluated. Sixteen historical patients served as controls. RESULTS: In all 58 patients, subdural electrodes were implanted as planned through tailored craniotomies. The mean craniotomy size was 28 ± 15 cm2 via which 55 ± 16 electrodes were implanted. In temporal lobe diagnostics, even smaller craniotomies were applied (21 ± 11 cm2). Craniotomies were significantly smaller than in historical controls (65 ± 23 cm2, p < 0.05), while the mean number of electrodes was comparable. The mean operation time was shorter and complications were reduced in tailored craniotomies. CONCLUSION: Craniotomy size for subdural electrode implantation is controversial. Some surgeons favor large craniotomies, while others strive for minimally invasive approaches. For the first time, we measured the actual craniotomy size for subdural grid electrode implantation. All procedures were straightforward. We therefore advocate for patient-tailored minimally invasive approaches - standard in modern microneurosurgery - in epilepsy surgery as well.

Surgical management of Chiari I malformation based on different cerebrospinal fluid flow patterns at the cranial-vertebral junction.

Chiari I malformation has been shown to present different cerebrospinal fluid (CSF) flow patterns at the cranial-vertebral junction (CVJ). Posterior fossa decompression is the first-line treatment for symptomatic Chiari I malformation. However, there is still controversy on the indication and selection of decompression procedures. This research aims to investigate the clinical indications, outcomes, and complications of the decompression procedures as alternative treatments for Chiari I malformation, based on the different CSF flow patterns at the cranial-vertebral junction. In this study, 126 Chiari I malformation patients treated with the two decompression procedures were analyzed. According to the preoperative findings obtained by using cine phase-contrast MRI (cine PC-MRI), the abnormal CSF flow dynamics at the CVJ in Chiari I malformation was classified into three patterns. After a preoperative evaluation and an intraoperative ultrasound after craniectomy, the two procedures were alternatively selected to treat the Chiari I malformation. The indication and selection of the two surgical procedures, as well as their outcomes and complications, are reported in detail in this work. Forty-eight patients underwent subdural decompression (SDD), and 78 received subarachnoid manipulation (SAM). Ninety patients were diagnosed as having Chiari I malformation with a syrinx. Two weeks after the operation, the modified Japanese Orthopedic Association (mJOA) scores increased from the preoperative value of 10.67 ± 1.61 to 12.74 ± 2.01 (P < 0.01). The mean duration of follow-up was 24.8 months; the mJOA scores increased from the postoperative value of 12.74 ± 2.01 to 12.79 ± 1.91 at the end of follow-up (P = 0.48). More complications occurred in the patients who underwent SAM than in those who received SDD (SAM 11 of 78 (9.5%) vs SDD 2 of 48 (3.5%)). The abnormal CSF flow dynamics at the CVJ in Chiari I malformation can be classified into three patterns. A SAM procedure is more feasible in Chiari I malformation (CM1) patients with pattern III CSF flow dynamics, whereas a SDD procedure is more suitable for CM1 patients with pattern I CSF flow dynamics. In CM1 patients with pattern II CSF flow dynamics, an intraoperative ultrasound after craniectomy could play an important role in the selection of an effective decompression procedure.

Improved long-term survival with subdural drains following evacuation of chronic subdural haematoma.

BACKGROUND: Chronic subdural haematoma (CSDH) is a common condition that is effectively managed by burrhole drainage but requires repeat surgery in a significant minority of patients. The Cambridge Chronic Subdural Haematoma Trial (CCSHT) was a randomised controlled study that showed placement of subdural drains for 48 h following burrhole evacuation significantly reduces the incidence of reoperation and improves survival at 6 months. The present study examined the long-term survival of the patients in the trial. METHODS: In the original trial patients at a single neurosurgical centre from 2004-2007 were randomly assigned to receive a drain (n = 108) or no drain (n = 107) following burrhole drainage of CSDH. We ascertained whether the trial patients were alive in February 2016-a minimum of 8 years following enrollment-via the UK NHS tracing service. Survival was compared between the trial groups and against expected survival for the UK general population matched for age and sex. RESULTS: At 5 years following surgery the drain group continued to have significantly better survival than the no drain patients (p = 0.027), but this was no longer apparent at 10 years. Survival of patients in the drain group did not differ significantly from that of the general population whereas patients who did not receive a drain had significantly lower survival than expected (p = 0.0006). CONCLUSION: Subdural drains following CSDH evacuation are associated with improved long-term survival, which appears similar to that expected for the general population of the same age and sex. All patients having burrhole CSDH evacuation should receive a drain as standard practice unless specifically contraindicated.

[Metastasis of Hepatocellular Carcinoma to the Membrane of Chronic Subdural Hematomas:A Case Report].

An 81-year-old man presented with gait disturbance. Two months previously, he suffered from hepatocellular carcinoma and transarterial chemoembolization was performed. A head computed tomography(CT)scan revealed bilateral chronic subdural hematomas. The patient's gait disturbance was improved after achievement of bilateral burr hole drainage. A head CT two months after treatment revealed no recurrence of the hematomas. However, head CT images obtained four months after treatment revealed an abnormal mass in the right parietal region attached to the internal surface of the skull. The mass was located in the same region from where the chronic subdural hematomas were previously removed via burr hole drainage, and was suspected to have originated from the dura mater. We performed craniotomy and total removal of the mass. The dura mater was intact, and macroscopically, the mass originated from the organized membrane of the chronic subdural hematoma. A pathological examination revealed metastasis of hepatocellular carcinoma to the membrane of the chronic subdural hematomas. Head magnetic resonance imaging(MRI)performed 39 days after craniotomy presented a new lesion in the left parietal region attached to the internal surface of the skull. The patient subsequently died 46 days post-operation. When examining chronic subdural hematomas in cancer patients, histological examination of the dura mater, hematoma, and membrane of the hematoma are important. The possibility of metastasis to the capsule of the hematoma should be considered.

Complications of subdural and depth electrodes in 269 patients undergoing 317 procedures for invasive monitoring in epilepsy.

OBJECTIVE: Intracranial monitoring is fundamental to epilepsy surgery, with reported complication rates of 3-17%. We aimed to assess the differences in complication rates between subdural and depth electrodes. METHODS: We conducted a retrospective review of 317 electrode implantation procedures. All documented abnormal postoperative findings were recorded in our study. Those that resulted in a significant alteration of treatment course, including neurologic deficit, long-term medication use, reoperation, or hospital readmission, were deemed clinically significant. When possible, findings were attributed to a particular electrode type based on relative location to each electrode. RESULTS: Postoperative abnormalities were associated with SDE placement in 152 (47.9%) procedures and 40 (25.2%) DE placements (p < 0.001). Twenty-nine (9.1%) clinically significant complications were seen in the subdural electrode (SDE) group compared to 10 associated with DEs (6.3%, p = 0.37). SDEs were associated with increased rates of any postoperative hemorrhage (p < 0.001) or extraaxial collection (p = 0.007). Subdural grid placement was associated with an increased risk of any extraaxial collection (odds ratio [OR 2.42), as well as clinically significant collections (OR 9.47). Previous craniotomy was found to be associated with any abnormal postoperative finding (OR 1.71) as well as radiographic hemorrhage (OR 1.99). Concurrent resection is also associated with abnormal findings (OR 1.83) and extraaxial collections (OR 2.37). The overall complication rate was 9.1%, with 13 procedures (4.1%) resulting in neurologic deficit. However, only two patients (0.6%) had permanent neurologic sequelae resulting from lead placement. SIGNIFICANCE: Subdural electrodes appear to have an increased rate of abnormal postoperative findings, including hemorrhage and extraaxial collections; however, there was no difference in clinically significant findings. Subdural grids also appear to be associated with symptomatic extraaxial collections, and previous craniotomy increases the risk of hemorrhage. Overall, intracranial monitoring remains a safe and effective procedure for localization of operative seizure foci. Patient selection and risk education for various modalities is an essential aspect of preoperative evaluation.

Frontotemporal epi- and subdural approach to a cavernous sinus tumor for sphenobasal vein preservation--technical case report.

In cavernous sinus (CS) surgery, venous complication may occur in some types of venous drainage. The sphenobasal vein (SBV) drains from the superficial middle cerebral vein (SMCV) to the pterygoid venous plexus at the temporal skull base. A frontotemporal epi- and interdural approach (Dolenc approach), which is one of the CS approaches, may damage the SBV's route. We report a case of intracavernous trigeminal schwannoma that contained the SBV and discuss our modified surgical procedure that combined epi- and subdural approaches to preserve the SBV. A 64-year-old man complained of right progressive oculomotor palsy and was referred to our hospital for surgery. MR images revealed a hemorrhagic tumor in the right CS. Three-dimensional venography revealed that the SMCV drained into the pterygoid venous plexus via the SBV. After identifying the first branch of the trigeminal nerve epidurally, we incised the dura linearly along the sylvian fissure and entered the subdural space to visualize the SBV. The incision was continued to the meningeal dura of the lateral wall of the CS along the superior margin of the first branch of the trigeminal nerve, and the Parkinson's triangle was opened from the subdural side. The tumor was grossly totally removed, and the SBV was preserved. In conclusion, a frontotemporal epi- and subdural approach to the intracavernous trigeminal schwannoma can effectively preserve the SBV.