Deep brain stimulation of different targets has been shown to drastically improve symptoms of a variety of neurological conditions. However, the occurrence of disabling side effects may limit the ...ability to deliver adequate amounts of current necessary to reach the maximal benefit. Computed models have suggested that reduction in electrode size and the ability to provide directional stimulation could increase the efficacy of such therapies. This has never been demonstrated in humans. In the present study, we assess the effect of directional stimulation compared to omnidirectional stimulation. Three different directions of stimulation as well as omnidirectional stimulation were tested intraoperatively in the subthalamic nucleus of 11 patients with Parkinson's disease and in the nucleus ventralis intermedius of two other subjects with essential tremor. At the trajectory chosen for implantation of the definitive electrode, we assessed the current threshold window between positive and side effects, defined as the therapeutic window. A computed finite element model was used to compare the volume of tissue activated when one directional electrode was stimulated, or in case of omnidirectional stimulation. All but one patient showed a benefit of directional stimulation compared to omnidirectional. A best direction of stimulation was observed in all the patients. The therapeutic window in the best direction was wider than the second best direction (P = 0.003) and wider than the third best direction (P = 0.002). Compared to omnidirectional direction, the therapeutic window in the best direction was 41.3% wider (P = 0.037). The current threshold producing meaningful therapeutic effect in the best direction was 0.67 mA (0.3-1.0 mA) and was 43% lower than in omnidirectional stimulation (P = 0.002). No complication as a result of insertion of the directional electrode or during testing was encountered. The computed model revealed a volume of tissue activated of 10.5 mm(3) in omnidirectional mode, compared with 4.2 mm(3) when only one electrode was used. Directional deep brain stimulation with a reduced electrode size applied intraoperatively in the subthalamic nucleus as well as in the nucleus ventralis intermedius of the thalamus significantly widened the therapeutic window and lowered the current needed for beneficial effects, compared to omnidirectional stimulation. The observed side effects related to direction of stimulation were consistent with the anatomical location of surrounding structures. This new approach opens the door to an improved deep brain stimulation therapy. Chronic implantation is further needed to confirm these findings.
OBJECTIVE Frontal ventriculostomy is one of the most frequent and standardized procedures in neurosurgery. However, many first and subsequent punctures miss the target, and suboptimal placement or ...misplacement of the catheter is common. The authors therefore reexamined the landmarks and rules to determine the entry point and trajectory with the best hit rate (HtR). METHODS The authors randomly selected CT scans from their institution's DICOM pool that had been obtained in 50 patients with normal ventricular and skull anatomy and without ventricular puncture. Using a 5 × 5-cm frontal grid with 25 entry points referenced to the bregma, the authors examined trajectories 1) perpendicular to the skull, 2) toward classic facial landmarks in the coronal and sagittal planes, and 3) toward an idealized target in the middle of the ipsilateral anterior horn (ILAH). Three-dimensional virtual reality ventriculostomies were simulated for these entry points; trajectories and the HtRs were recorded, resulting in an investigation of 8000 different virtual procedures. RESULTS The best HtR for the ILAH was 86% for an ideal trajectory, 84% for a landmark trajectory, and 83% for a 90° trajectory, but only at specific entry points. The highest HtRs were found for entry points 3 or 4 cm lateral to the midline, but only in combination with a trajectory toward the contralateral canthus; and 1 or 2 cm lateral to the midline, but only paired with a trajectory toward the nasion. The same "pairing" exists for entry points and trajectories in the sagittal plane. For perpendicular (90°) trajectories, the best entry points were at 3-5 cm lateral to the midline and 3 cm anterior to the bregma, or 4 cm lateral to the midline and 2 cm anterior to the bregma. CONCLUSIONS Only a few entry points offer a chance of a greater than 80% rate of hitting the ILAH, and then only in combination with a specific trajectory. This "pairing" between entry point and trajectory was found both for landmark targeting and for perpendicular trajectories, with very limited variability. Surprisingly, the ipsilateral medial canthus, a commonly reported landmark, had low HtRs, and should not be recommended as a trajectory target.
Mapping and monitoring are believed to provide an early warning sign to determine when to stop tumor removal to avoid mechanical damage to the corticospinal tract (CST). The objective of this study ...was to systematically compare subcortical monopolar stimulation thresholds (1-20 mA) with direct cortical stimulation (DCS)-motor evoked potential (MEP) monitoring signal abnormalities and to correlate both with new postoperative motor deficits. The authors sought to define a mapping threshold and DCS-MEP monitoring signal changes indicating a minimal safe distance from the CST.
A consecutive cohort of 100 patients underwent tumor surgery adjacent to the CST while simultaneous subcortical motor mapping and DCS-MEP monitoring was used. Evaluation was done regarding the lowest subcortical mapping threshold (monopolar stimulation, train of 5 stimuli, interstimulus interval 4.0 msec, pulse duration 500 μsec) and signal changes in DCS-MEPs (same parameters, 4 contact strip electrode). Motor function was assessed 1 day after surgery, at discharge, and at 3 months postoperatively.
The lowest individual motor thresholds (MTs) were as follows (MT in mA, number of patients): > 20 mA, n = 12; 11-20 mA, n = 13; 6-10 mA, n = 20; 4-5 mA, n = 30; and 1-3 mA, n = 25. Direct cortical stimulation showed stable signals in 70 patients, unspecific changes in 18, irreversible alterations in 8, and irreversible loss in 4 patients. At 3 months, 5 patients had a postoperative new or worsened motor deficit (lowest mapping MT 20 mA, 13 mA, 6 mA, 3 mA, and 1 mA). In all 5 patients DCS-MEP monitoring alterations were documented (2 sudden irreversible threshold increases and 3 sudden irreversible MEP losses). Of these 5 patients, 2 had vascular ischemic lesions (MT 20 mA, 13 mA) and 3 had mechanical CST damage (MT 1 mA, 3 mA, and 6 mA; in the latter 2 cases the resection continued after mapping and severe DCS-MEP alterations occurred thereafter). In 80% of patients with a mapping MT of 1-3 mA and in 75% of patients with a mapping MT of 1 mA, DCS-MEPs were stable or showed unspecific reversible changes, and none had a permanent motor worsening at 3 months. In contrast, 25% of patients with irreversible DCS-MEP changes and 75% of patients with irreversible DCS-MEP loss had permanent motor deficits.
Mapping should primarily guide tumor resection adjacent to the CST. DCS-MEP is a useful predictor of deficits, but its value as a warning sign is limited because signal alterations were reversible in only approximately 60% of the present cases and irreversibility is a post hoc definition. The true safe mapping MT is lower than previously thought. The authors postulate a mapping MT of 1 mA or less where irreversible DCS-MEP changes and motor deficits regularly occur. Therefore, they recommend stopping tumor resection at an MT of 2 mA at the latest. The limited spatial and temporal coverage of contemporary mapping may increase error and may contribute to false, higher MTs.
During intraoperative monitoring of motor evoked potentials (MEP), heterogeneity across studies in terms of study populations, intraoperative settings, applied warning criteria, and outcome reporting ...exists. A scoping review of MEP warning criteria in supratentorial surgery was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). Sixty-eight studies fulfilled the eligibility criteria. The most commonly used alarm criteria were MEP signal loss, which was always a major warning sign, followed by amplitude reduction and threshold elevation. Irreversible MEP alterations were associated with a higher number of transient and persisting motor deficits compared with the reversible changes. In almost all studies, specificity and Negative Predictive Value (NPV) were high, while in most of them, sensitivity and Positive Predictive Value (PPV) were rather low or modest. Thus, the absence of an irreversible alteration may reassure the neurosurgeon that the patient will not suffer a motor deficit in the short-term and long-term follow-up. Further, MEPs perform well as surrogate markers, and reversible MEP deteriorations after successful intervention indicate motor function preservation postoperatively. However, in future studies, a consensus regarding the definitions of MEP alteration, critical duration of alterations, and outcome reporting should be determined.
Background
Due to its complexity and to existing treatment alternatives, exposure to intracranial aneurysm microsurgery at the time of neurosurgical residency is limited. The current state of the art ...includes training methods like assisting in surgeries, operating under supervision, and video training. These approaches are labor-intensive and difficult to fit into a timetable limited by the new work regulations. Existing virtual reality (VR)–based training modules lack patient-specific exercises and haptic properties and are thus inferior to hands-on training sessions and exposure to real surgical procedures.
Materials and methods
We developed a physical simulator able to reproduce the experience of clipping an intracranial aneurysm based on a patient-specific 3D-printed model of the skull, brain, and arteries. The simulator is made of materials that not only imitate tissue properties including arterial wall patency, thickness, and elasticity but also able to recreate a pulsatile blood flow. A sample group of 25 neurosurgeons and residents (
n
= 16: early residency with less than 4 years of neurosurgical exposure;
n
= 9: late residency and board-certified neurosurgeons, 4–15 years of neurosurgical exposure) took part to the study. Participants evaluated the simulator and were asked to answer questions about surgical simulation anatomy, realism, haptics, tactility, and general usage, scored on a 5-point Likert scale. In order to evaluate the feasibility of a future validation study on the role of the simulator in neurosurgical postgraduate training, an expert neurosurgeon assessed participants’ clipping performance and a comparison between groups was done.
Results
The proposed simulator is reliable and potentially useful for training neurosurgical residents and board-certified neurosurgeons. A large majority of participants (84%) found it a better alternative than conventional neurosurgical training methods.
Conclusion
The integration of a new surgical simulator including blood circulation and pulsatility should be considered as part of the future armamentarium of postgraduate education aimed to ensure high training standards for current and future generations of neurosurgeons involved in intracranial aneurysm surgery.
BACKGROUND AND PURPOSE—Whether maximal treatment should be offered to elderly patients suffering from poor-grade aneurysmal subarachnoid hemorrhage (aSAH) is controversial. The survival of patients ...in this subgroup beyond the usual outcome measurements 6 to 12 months after aSAH is unclear. The purpose of this study is to provide survival and outcome data to support clinicians making decisions on treatment for this subgroup of patients.
METHODS—We performed a retrospective analysis of the Bernese SAH database for poor-grade (World Federation of Neurosurgical Societies grade IV and V) elderly patients (age ≥60 years) suffering from aSAH admitted to our institution from 2005 to 2017. Patients were divided into 3 age groups (60–69, 70–79, and 80–90 years). Survival analysis was performed to estimate mean survival and hazard ratios for death. Binary logarithmic regression was used to estimate the odds ratio for favorable (modified Rankin Scale score of 0–3) and unfavorable (modified Rankin Scale score of 4–6) outcome.
RESULTS—Increasing age was associated with an increasing risk of death after aSAH. The hazard ratio increased by 6% per year of age (P<0.001; hazard ratio, 1.06; 95% CI, 1.03–1.09) and 76% per decade (P<0.001; hazard ratio, 1.76; 95% CI, 1.35–2.29). Mean survival was 56.3±8 months (patients aged 60–69 years), 31.6±7.6 months (70–79 years), and 7.6±5.8 months (80–90 years). Unfavorable outcomes 6 to 12 months after aSAH were strongly related to older age. The odds ratio increased by 11% per year of age (P<0.001; odds ratio, 1.11; 95% CI, 1.05–1.18) and 192% per decade (P<0.001; odds ratio, 2.92; 95% CI, 1.63–5.26).
CONCLUSIONS—Risk for death and unfavorable outcome increases markedly with older age in elderly patients with poor-grade aSAH. Despite a high initial mortality, treatment resulted in a reasonable proportion of favorable outcomes up to 79 years of age and only a small number of patients who were moderately or severely disabled 6 to 12 months after aSAH. Mean survival and proportion of favorable outcomes decreased markedly in patients older than 80 years.
OBJECTIVE Outcome analysis of comatose patients (Hunt and Hess Grade V) after subarachnoid hemorrhage (SAH) is still lacking. The aims of this study were to analyze the outcome of Hunt and Hess Grade ...V SAH and to compare outcomes in the current period with those of the pre-International Subarachnoid Aneurysm Trial (ISAT) era as well as with published data from trials of decompressive craniectomy (DC) for middle cerebral artery (MCA) infarction. METHODS The authors analyzed cases of Hunt and Hess Grade V SAH from 1980-1995 (referred to in this study as the earlier period) and 2005-2014 (current period) and compared the results for the 2 periods. The outcomes of 257 cases were analyzed and stratified on the basis of modified Rankin Scale (mRS) scores obtained 6 months after SAH. Outcomes were dichotomized as favorable (mRS score of 0-2) or unfavorable (mRS score of 3-6). Data and number needed to treat (NNT) were also compared with the results of decompressive craniectomy (DC) trials for middle cerebral artery (MCA) infarctions. RESULTS Early aneurysm treatment within 72 hours occurred significantly more often in the current period (in 67% of cases vs 22% in earlier period). In the earlier period, patients had a significantly higher 30-day mortality rate (83% vs 39% in the current period) and 6-month mortality rate (94% vs 49%), and no patient (0%) had a favorable outcome, compared with 23% overall in the current period (p < 0.01, OR 32), or 29.5% of patients whose aneurysms were treated (p < 0.01, OR 219). Cerebral infarctions occurred in up to 65% of the treated patients in the current period. Comparison with data from DC MCA trials showed that the NNTs were significantly lower in the current period with 2 for survival and 3 for mRS score of 0-3 (vs 3 and 7, respectively, for the DC MCA trials). CONCLUSIONS Early and aggressive treatment resulted in a significant improvement in survival rate (NNT = 2) and favorable outcome (NNT = 3 for mRS score of 0-3) for comatose patients with Hunt and Hess Grade V SAH compared with the earlier period. Independent predictors for favorable outcome were younger age and bilateral intact corneal reflexes. Despite a high rate of cerebral infarction (65%) in the current period, 29.5% of the patients who received treatment for their aneurysms during the current era (2005-2014) had a favorable outcome. However, careful individual decision making is essential in these cases.
Summary Background Clazosentan, an endothelin receptor antagonist, significantly and dose-dependently reduced angiographic vasospasm after aneurysmal subarachnoid haemorrhage (aSAH). We investigated ...whether clazosentan reduced vasospasm-related morbidity and all-cause mortality. Methods In this randomised, double-blind, placebo-controlled, phase 3 study, we randomly assigned patients with aSAH secured by surgical clipping to clazosentan (5 mg/h, n=768) or placebo (n=389) for up to 14 days (27 countries, 102 sites, inpatient and outpatient settings) using an interactive web response system. The primary composite endpoint (week 6) included all-cause mortality, vasospasm-related new cerebral infarcts, delayed ischaemic neurological deficit due to vasospasm, and rescue therapy for vasospasm. The main secondary endpoint was dichotomised extended Glasgow outcome scale (GOSE; week 12). This trial is registered with ClinicalTrials.gov , number NCT00558311. Findings In the all-treated dataset, the primary endpoint was met in 161 (21%) of 764 clazosentan-treated patients and 97 (25%) of 383 placebo-treated patients (relative risk reduction 17%, 95% CI −4 to 33; p=0·10). Poor functional outcome (GOSE score ≤4) occurred in 224 (29%) clazosentan-treated patients and 95 (25%) placebo-treated patients (−18%, −45 to 4; p=0·10). Lung complications, anaemia, and hypotension were more common with clazosentan. Mortality (week 12) was 6% in both groups. Interpretation Clazosentan at 5 mg/h had no significant effect on mortality and vasospasm-related morbidity or functional outcome. Further investigation of patients undergoing endovascular coiling of ruptured aneurysms is needed to fully understand the potential usefulness of clazosentan in patients with aSAH. Funding Actelion Pharmaceuticals.
Objective
Spinal cerebrospinal fluid (CSF) leaks cause spontaneous intracranial hypotension (SIH). Microsurgery can sufficiently seal spinal CSF leaks. Yet, some patients suffer from residual ...symptoms. Aim of the study was to assess predictors for favorable outcome after surgical treatment of SIH.
Methods
We included consecutive patients with SIH treated surgically from January 2013 to May 2020. Subjects were surveyed by a questionnaire. Primary outcome was resolution of symptoms as rated by the patient. Secondary outcome was postoperative headache intensity on the numeric rating scale (NRS). Association between variables and outcome was assessed using univariate and multivariate regression. A cut-off value for continuous variables was calculated by a ROC analysis.
Results
Sixty-nine out of 86 patients (80.2%) returned the questionnaire and were analyzed. Mean age was 46.7 years and 68.1% were female. A significant association with the primary and secondary outcome was found only for preoperative symptom duration (
p
= 0.001 and
p
< 0.001), whereby a shorter symptom duration was associated with a better outcome. Symptom duration remained a significant predictor in a multivariate model (
p
= 0.013). Neither sex, age, type of pathology, lumbar opening pressure, nor initial presentation were associated with the primary outcome. ROC analysis yielded treatment within 12 weeks as a cut-off for better outcome.
Conclusion
Shorter duration of preoperative symptoms is the most powerful predictor of favorable outcome after surgical treatment of SIH. While an initial attempt of conservative treatment is justified, we advocate early definitive treatment within 12 weeks in case of persisting symptoms.
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