Anesthesia for deep brain stimulation system implantation: adapted protocol for awake and asleep surgery using microelectrode recordings.

PURPOSE: Deep brain stimulation (DBS), an effective treatment for movement disorders, usually involves lead implantation while the patient is awake and sedated. Recently, there has been interest in performing the procedure under general anesthesia (asleep). This report of a consecutive cohort of DBS patients describes anesthesia protocols for both awake and asleep procedures. METHODS: Consecutive patients with Parkinson's disease received subthalamic nucleus (STN) implants either moderately sedated or while intubated, using propofol and remifentanil. Microelectrode recordings were performed with up to five trajectories after discontinuing sedation in the awake group, or reducing sedation in the asleep group. Clinical outcome was compared between groups with the UPDRS III. RESULTS: The awake group (n = 17) received 3.5 mg/kg/h propofol and 11.6 µg/kg/h remifentanil. During recording, all anesthesia was stopped. The asleep group (n = 63) initially received 6.9 mg/kg/h propofol and 31.3 µg/kg/h remifentanil. During recording, this was reduced to 3.1 mg/kg/h propofol and 10.8 µg/kg/h remifentanil. Without parkinsonian medications or stimulation, 3-month UPDRS III ratings (ns = 16 and 52) were 40.8 in the awake group and 41.4 in the asleep group. Without medications but with stimulation turned on, ratings improved to 26.5 in the awake group and 26.3 in the asleep group. With both medications and stimulation, ratings improved further to 17.6 in the awake group and 15.3 in the asleep group. All within-group improvements from the off/off condition were statistically significant (all ps < 0.01). The degree of improvement with stimulation, with or without medications, was not significantly different in the awake vs. asleep groups (ps > 0.05). CONCLUSION: The above anesthesia protocols make possible an asleep implant procedure that can incorporate sufficient microelectrode recording. Together, this may increase patient comfort and improve clinical outcomes.

Motor Evoked Potentials Improve Targeting in Deep Brain Stimulation Surgery.

OBJECTIVES: One of the main challenges posed by the surgical deep brain stimulation (DBS) procedure is the successful targeting of the structures of interest and avoidance of side effects, especially in asleep surgery. Here, intraoperative motor evoked potentials (MEPs) might serve as tool to identify the pyramidal tract. We hypothesized that intraoperative MEPs are useful to define the distance to the pyramidal tract and reduce the occurrence of postoperative capsular side effects. MATERIALS AND METHODS: Motor potentials were evoked through both microelectrode and DBS-electrode stimulation during stereotactic DBS surgery on 25 subthalamic nuclei and 3 ventral intermediate thalamic nuclei. Internal capsule proximity was calculated for contacts on microelectrode trajectories, as well as for DBS-electrodes, and correlated with the corresponding MEP thresholds. Moreover, the predictivity of intraoperative MEP thresholds on the probability of postoperative capsular side effects was calculated. RESULTS: Intraoperative MEPs thresholds correlated significantly with internal capsule proximity, regardless of the stimulation source. Furthermore, MEPs thresholds were highly accurate to exclude the occurrence of postoperative capsular side effects. CONCLUSIONS: Intraoperative MEPs provide additional targeting guidance, especially in asleep DBS surgery, where clinical value of microelectrode recordings and test stimulation may be limited. As this technique can exclude future capsular side effects, it can directly be translated into clinical practice.

Directional Deep Brain Stimulation of the Thalamic Ventral Intermediate Area for Essential Tremor Increases Therapeutic Window.

OBJECTIVES: Deep brain stimulation (DBS) of the posterior subthalamic area (PSA) and the ventral intermediate thalamic nucleus (VIM) is a well-established therapy for essential tremor (ET), but it is frequently associated with side effects like dysarthria or gait ataxia. Directional DBS (dDBS) may be a way to activate fiber tracts more selectively. Is dDBS for ET superior to omnidirectional DBS (oDBS) regarding therapeutic window and clinically as effective as oDBS? MATERIALS AND METHODS: Ten patients with ET treated with PSA/VIM-DBS were recruited. Therapeutic window served as primary outcome parameter; clinical efficacy, volume of neuronal activation, and total electrical energy delivered (TEED) served as secondary outcome parameters. Therapeutic window was calculated for all three dDBS directions and for oDBS by determining therapeutic thresholds and side effect thresholds. Clinical efficacy was assessed by comparing the effect of best dDBS and oDBS on tremor and ataxia rating scales, and accelerometry. Volume of neural activation and TEED were also calculated for both paradigms. RESULTS: For best dDBS, therapeutic window was wider and therapeutic threshold was lower compared to oDBS. While side effect threshold did not differ, volume of neural activation was larger for dDBS. In terms of clinical efficacy, dDBS was as effective as oDBS. CONCLUSIONS: dDBS for ET widens therapeutic window due to reduction of therapeutic threshold. Larger volume of neural activation for dDBS at side effect threshold supports the notion of persistent directionality even at higher intensities. dDBS may compensate for slightly misplaced leads and should be considered first line for PSA/VIM-DBS.

Accuracy of Electrode Position in Sphenopalatine Ganglion Stimulation in Correlation With Clinical Efficacy.

INTRODUCTION: Sphenopalatine ganglion (SPG) stimulation is an efficient treatment for cluster headache. The target for the SPG microstimulator in the pterygopalatine fossa lies between the vidian canal and foramen rotundum, ideally two contacts should be placed in this area. However, placement according to the manufacturers recommendations is frequently not possible. It is not known whether a suboptimal electrode placement interferes with postoperative outcomes. MATERIALS AND METHODS: SPG stimulation was performed in 13 patients between 2015 and 2018 in a single center. Lead location was determined by intraoperative computed tomography scan and correlated with the planned lead position as well as clinical data and stimulation parameters. Patients with a reduction of 50% or more in pain intensity or frequency were considered responsive. RESULTS: Eleven patients (84.6%) responded to SPG stimulation with eight being frequency responders (61.5%). In seven cases, there were less than two electrodes between vidian canal and foramen rotundum, there was no significant correlation with negative stimulation results (p = 0.91). The mean distance of lead location between pre- and postoperative images did not correlate with clinical outcomes (p = 0.84) and was even bigger in responders (4.91 mm vs. 4.53 mm). The closest electrode contact to the vidian canal was in the stimulation area in all but one patient, regardless of its overall distance to canal. The distance of the closest electrode to the vidian canal was, however, not significantly correlated to the percentage of frequency (p = 0.68) or intensity reduction (p = 0.61). CONCLUSION: There was no significant correlation regarding aberrations of lead position from the planned position with clinical outcome. However, this study might be underpowered to detect such a correlation. The closest electrode contact to the vidian canal was in the stimulation area in all but one patient in the final programming. This indicates that, overall, the lead location does play a crucial role in SPG stimulation for cluster headache.

Asleep Surgery May Improve the Therapeutic Window for Deep Brain Stimulation of the Subthalamic Nucleus.

OBJECTIVE: The effect of anesthesia type in terms of asleep vs. awake deep brain stimulation (DBS) surgery on therapeutic window (TW) has not been investigated so far. The objective of the study was to investigate whether asleep DBS surgery of the subthalamic nucleus (STN) improves TW for both directional (dDBS) and omnidirectional (oDBS) stimulation in a large single-center population. MATERIALS AND METHODS: A total of 104 consecutive patients with Parkinson's disease (PD) undergoing STN-DBS surgery (80 asleep and 24 awake) were compared regarding TW, therapeutic threshold, side effect threshold, improvement of Unified PD Rating Scale motor score (UPDRS-III) and degree of levodopa equivalent daily dose (LEDD) reduction. RESULTS: Asleep DBS surgery led to significantly wider TW compared to awake surgery for both dDBS and oDBS. However, dDBS further increased TW compared to oDBS in the asleep group only and not in the awake group. Clinical efficacy in terms of UPDRS-III improvement and LEDD reduction did not differ between groups. CONCLUSIONS: Our study provides first evidence for improvement of therapeutic window by asleep surgery compared to awake surgery, which can be strengthened further by dDBS. These results support the notion of preferring asleep over awake surgery but needs to be confirmed by prospective trials.

Sphenopalatine Ganglion Stimulation for Chronic Headache Syndromes.

Neuropathic facial pain is notoriously difficult to treat, regardless of its origin and duration. Since the first reported sphenopalatine ganglion blockade by Sluder in 1908, this ganglion has assumed an important role among the structures targeted for the treatment of facial pain. Recent years have witnessed the rise of neuromodulation over ablative procedures, including the development of an implantable stimulation device specially designed for use in the pterygopalatine fossa. Sphenopalatine ganglion stimulation has been demonstrated as effective and safe for refractory cluster headache, today the major indication for this therapy, but increasing evidence shows that the effect on the autonomic system and cerebral circulation could justify an even wider use of sphenopalatine ganglion stimulation for other chronic headache syndromes and vascular diseases.

Synergetic efficacy of simultaneous DRG- and traditional spinal cord stimulation.

BACKGROUND: Dorsal root ganglion stimulation has established its role in chronic pain states and is commonly used as an alternative treatment to traditional spinal cord stimulation. Due to its approach, DRG stimulation is preferably used in pain conditions affecting a small area or a distinct nerve root. In selected patients, a combination of both techniques might be useful. METHODS: We report a series of five patients with chronic pain treated with DRG stimulation and traditional spinal cord stimulation from 2011 to 2018. Pain was reported on the VAS scale at the baseline, before and 12 months after the second procedure. RESULTS: All patients suffered from back and lower limb pain, four with a FBSS syndrome, one with CRPS. In all but one patient, SCS was implanted first and complemented with a DRG in the course (4-90 months between procedures). An additional stimulation system was implanted because the previous stimulation failed to reach the pain area or because the patient had an altered perception of other pain component after stimulation. All but one patient had a consistent and satisfying therapeutic effect with both systems activated. CONCLUSION: The combination of dorsal root ganglion and traditional spinal cord stimulation is surgically and technically feasible. In selected patients, the combination of both methods offers an option to alleviate pain states not sufficiently or not efficiently treated with one method alone. The introduction of IPGs combining SCS and DRG stimulation paradigms might be useful to increase acceptance of this option.

A multicenter, open-label, controlled trial on acceptance, convenience, and complications of rechargeable internal pulse generators for deep brain stimulation: the Multi Recharge Trial.

OBJECTIVE: Rechargeable neurostimulators for deep brain stimulation have been available since 2008, promising longer battery life and fewer replacement surgeries compared to non-rechargeable systems. Long-term data on how recharging affects movement disorder patients are sparse. This is the first multicenter, patient-focused, industry-independent study on rechargeable neurostimulators. METHODS: Four neurosurgical centers sent a questionnaire to all adult movement disorder patients with a rechargeable neurostimulator implanted at the time of the trial. The primary endpoint was the convenience of the recharging process rated on an ordinal scale from "very hard" (1) to "very easy" (5). Secondary endpoints were charge burden (time spent per week on recharging), user confidence, and complication rates. Endpoints were compared for several subgroups. RESULTS: Datasets of 195 movement disorder patients (66.1% of sent questionnaires) with Parkinson's disease (PD), tremor, or dystonia were returned and included in the analysis. Patients had a mean age of 61.3 years and the device was implanted for a mean of 40.3 months. The overall convenience of recharging was rated as "easy" (4). The mean charge burden was 122 min/wk and showed a positive correlation with duration of therapy; 93.8% of users felt confident recharging the device. The rate of surgical revisions was 4.1%, and the infection rate was 2.1%. Failed recharges occurred in 8.7% of patients, and 3.6% of patients experienced an interruption of therapy because of a failed recharge. Convenience ratings by PD patients were significantly worse than ratings by dystonia patients. Caregivers recharged the device for the patient in 12.3% of cases. Patients who switched from a non-rechargeable to a rechargeable neurostimulator found recharging to be significantly less convenient at a higher charge burden than did patients whose primary implant was rechargeable. Age did not have a significant impact on any endpoint. CONCLUSIONS: Overall, patients with movement disorders rated recharging as easy, with low complication rates and acceptable charge burden.

Is the Intensity of 5-Aminolevulinic Acid-Derived Fluorescence Related to the Light Source?

OBJECTIVE: With the introduction of the 5-aminolevulinic acid (5-ALA) technique, surgical neuro-oncology has made a major advance. 5-ALA fluorescence-guided resection of malignant glioma results in more complete surgical resections and subsequently prolonged survival. However, it remains uncertain how light intensities of the blue light source and 5-ALA-derived fluorescence intensities of the illuminated tissue are connected. The aim of the present study was to compare light intensities of different blue light sources and protoporphyrin (PpIX) fluorescence intensities of PpIX solutions with defined concentrations after illumination with different light sources. MATERIAL AND METHODS: The light spectrum of 7 different blue light sources and the fluorescence intensity of 2 PpIX solutions (0.15 µg/mL and 5 µg/mL) were quantified after illumination. We compared the Zeiss OPMI Pentero microscope, the Zeiss OPMI Pentero 900 microscope, the Leica M530 OH6 microscope, an endoscope equipped with the 5-ALA technique, a mini-spectrometer equipped with a multi-channel light-emitting diode (LED) source emitting monochromatic light, a modified commercially available LED head lamp, and a commercially available unmodified UV-LED lamp. PpIX fluorescence was quantified in a standardized setup using a mini-spectrometer. RESULTS: Maximum light intensities of the evaluated light sources were reached at different wavelengths. All tested devices were able to detect PpIX-induced fluorescence. However, the intensity of PpIX fluorescence of the differently concentrated PpIX solutions (0.15 µg/mL and 5 µg/mL) was significantly dependent on the light source used. CONCLUSIONS: Intensity of the 5-ALA-derived fluorescence is related to the light source used.

Cervical and High-Thoracic Dorsal Root Ganglion Stimulation in Chronic Neuropathic Pain.

INTRODUCTION: Dorsal root ganglion stimulation is a meanwhile established but rather new technique of neuromodulation to treat chronic pain states of different origin. While being primarily used in the lumbar region, dorsal root ganglion (DRG) stimulation also can be used in the upper thoracic and cervical region with slight alterations of the surgical approach. This offers new therapeutic options especially in the treatment of neuropathic pain states of the upper extremities. Data on surgical technique, outcome and complications rates of DRG in this region are limited. MATERIALS AND METHODS: We report a consecutive series of 20 patients treated with DRG stimulation in the upper thoracic and cervical region. All patients suffered from chronic neuropathic pain unresponsive to best medical treatment. Main pain etiologies were trauma, spine surgery, postherpetic neuralgia, and peripheral nerve surgery. All patients were trialed with externalized electrodes prior to permanent pulse generator implantation. Routine clinical follow-up was performed during reprogramming sessions. RESULTS: Out of all 20 patients trialed, 18 were successfully trialed and implanted with a permanent stimulation system. The average pain relief after three months compared to the baseline was of 60.9% (mean VAS 8.5 to VAS 3.2). 77.8% of the patients reported a pain relief of at least 50% after three months. One patient developed a transient paresis of the arm caused by the procedure. She completely recovered within three months. CONCLUSION: Cervical and upper thoracic DRG stimulation resulted in good overall response rates to trialing and similar pain relief when compared to DRG stimulation for groin and lower limb pain. A modified surgical approach has to be used when compared with lumbar DRG electrode placement. Surgery itself in this region is more complication prone and challenging.

Is it all a matter of size? Impact of maximization of surgical resection in cerebral tumors.

The oncological impact of cytoreductive surgery for malignant glioma has been analyzed in a few prospective, randomized studies; however, the impact of different cytoreductive surgical techniques of cerebral tumors remains controversial. Despite retrospective analyses revealing an oncological impact of complete surgical resection in cerebral metastases and low-grade glioma, the oncological impact of further extension of resection to a supramarginal resection remains disputable lacking high-grade evidence: supramarginal resections have yet to be analyzed in malignant glioma. Although extension of resection towards a supramarginal resection was thought to improve outcome and prevent malignant transformation in low-grade glioma, the rate of (temporary) deficits was higher than 50% in recent retrospective studies, and the oncological impact and long-term results have to be analyzed in further (prospective and controlled) studies. Cerebral metastases show a growth pattern different from glioma with less and more locally limited brain invasion. Therefore, local control may be achieved by extension of resection after complete lesionectomy of cerebral metastases. Therefore, supramarginal resection may be a promising approach but must be evaluated in further studies.

Open Microsurgical Dorsal Root Ganglion Lead Placement.

INTRODUCTION: Dorsal root ganglion stimulation (DRG) is a new but well-established neuromodulation technique allowing new indications and superiority to pre-existing stimulation techniques such as spinal cord stimulation in selected pain etiologies. Previous surgical procedures in the implantation area pose a challenge for the percutaneous technique and are therefore considered contraindications for DRG stimulation surgery. We describe the successful open DRG electrode placement in two patients with previous surgeries suffering from severe radiculopathy due to foraminal stenosis. METHODS: Percutaneous implantation attempts failed and an open laminotomy/foraminotomy followed by open lead placement was performed. Leads and loops were placed under the microscope, lead location was verified by x-ray during surgery. Leads and loops were kept in position with fibrin glue and fibrin sealant patches. No special tool was required for open lead placement. RESULTS: In both patients, surgery resulted in lead and loop placement resembling the results seen in percutaneous technique. Programming and stimulation results are similar to observations made following percutaneous techniques in one patient significantly lower stimulation amplitudes were necessary. In 18 and 12 months follow-up, respectively, lead location and paresthesia coverage were stable. CONCLUSION: The option of open electrode placement should be taken into account following unsuccessful percutaneous lead placement. A combination of fibrin sealant patch and fibrin glue may be a good option for stabilization of the lead and specially of the strain relief loops in open placement. Knowledge of basic spinal surgery techniques and experience in percutaneous DRG stimulation is necessary to perform this procedure.

Bow Hunter's Syndrome Caused by Compression of the Subaxial Vertebral Artery: Surgical Technique of Anterolateral Decompression (video).

Bow hunter's syndrome is a rare clinical condition. It is caused by dynamic compression of the vertebral artery (VA) either at the level of the transverse foramina (V2 segment) or at the atlantoaxial level (V3 segment). We report a 54-year-old man with typical bow hunter's syndrome caused by compression at the level of C6/C7. He was successfully treated by anterolateral VA decompression without a need for stabilization. We present preoperative imaging (magnetic resonance imaging, computed tomographic angiography, and dynamic angiography) and a high-quality intraoperative video detailing each step of the surgical technique (high-definition video with annotations and audio track of the Doppler ultrasound used as intraoperative control). Furthermore, postoperative imaging and a video of the clinical outcome are presented. Adequate management of bow hunter's syndrome requires good pathophysiologic understanding of the disease and careful clinical examination. Dynamic angiography confirms the exact site of VA compression. Surgical decompression is the treatment of the cause. Surgical techniques include VA decompression by an anterolateral approach (V2 or V3) or a posterior approach (V3). Some authors advocate stand-alone stabilization, which is, however, only an indirect treatment and results in significant loss of head motion. Other nonsurgical treatments such as orthesis, medical therapy, or endovascular stenting have been only anecdotally reported. Bow hunter's syndrome is best treated by VA decompression. This may safely be achieved by good anatomic knowledge and a straightforward surgical technique. Here, the anterolateral approach is presented in detail in a high-definition surgical instruction video.

An introduction to the pathophysiology of aneurysmal subarachnoid hemorrhage.

Pathophysiological processes following subarachnoid hemorrhage (SAH) present survivors of the initial bleeding with a high risk of morbidity and mortality during the course of the disease. As angiographic vasospasm is strongly associated with delayed cerebral ischemia (DCI) and clinical outcome, clinical trials in the last few decades focused on prevention of these angiographic spasms. Despite all efforts, no new pharmacological agents have shown to improve patient outcome. As such, it has become clear that our understanding of the pathophysiology of SAH is incomplete and we need to reevaluate our concepts on the complex pathophysiological process following SAH. Angiographic vasospasm is probably important. However, a unifying theory for the pathophysiological changes following SAH has yet not been described. Some of these changes may be causally connected or present themselves as an epiphenomenon of an associated process. A causal connection between DCI and early brain injury (EBI) would mean that future therapies should address EBI more specifically. If the mechanisms following SAH display no causal pathophysiological connection but are rather evoked by the subarachnoid blood and its degradation production, multiple treatment strategies addressing the different pathophysiological mechanisms are required. The discrepancy between experimental and clinical SAH could be one reason for unsuccessful translational results.

The impact of cerebral metastases growth pattern on neurosurgical treatment.

The surgical resection of cerebral metastases is one key element in a multimodal therapy of brain oligometastatic patients. Standard surgery alone is often not sufficient to achieve local control. Various reasons have been discussed including microscopic and macroscopic tumor rests after surgery and different growth patterns of cerebral metastases: In this review, we assessed the surgical standard technique and then analyzed the growth pattern of cerebral metastases and discussed its oncologic impact and new strategies in the surgical management of cerebral metastases. A major percentage of cerebral metastases are not sharply delimitated but show an irregular tumor-brain interface or even an infiltrative growth pattern. Different patterns of adjacent brain invasions have been described and may correlate with the prognosis of patients with cerebral metastasis. Even metastases of the same histological subtype and the same origin show a heterogeneous brain invasion pattern. Future therapeutic strategies might have to take this heterogeneity into account. An infiltrative growth pattern of cerebral metastases might be one reason for their extraordinary high local recurrence rate and might have an influence on the individual overall survival. An intraoperative detection of residual tumor and development of more radical surgical techniques is therefore an important neurooncological challenge and might result in better tumor control. Supramarginal resection of cerebral metastases is a promising approach.

Predictors for a further local in-brain progression after re-craniotomy of locally recurrent cerebral metastases.

Treatment of recurrent cerebral metastases is an emerging challenge due to the high local failure rate after surgery or radiosurgery and the improved prognosis of patients with malignancies. A total of 36 patients with 37 metastases who underwent surgery for a local in-brain progression of a cerebral metastasis after previous metastasectomy were retrospectively analyzed. Degree of surgical resection on an early postoperative MRI within 72 h after surgery was correlated with the local in-brain progression rate and overall survival. Complete surgical resection of locally recurrent cerebral metastases as confirmed by early postoperative MRI could only be achieved in 37.8%. Detection of residual tumor tissue on an early MRI following recurrent metastasis surgery correlated with further local in-brain progression when defining a significance level of p = 0.05 but not after Sidák or Bonferroni significance level correction for multiple testing: However, definite local tumor control could finally be achieved in 91.9% after adjuvant therapy. Overall survival after recurrent metastasectomy was significantly higher as predicted by diagnosis-specific graded prognostic assessment (12.9 ± 2.3 vs. 8.4 ± 0.7 months; p < 0.0001). However, our series involved a limited number of heterogeneous patients. A larger, prospective, and controlled study is required. Considering the adequate local tumor control achieved in the vast majority of patients, surgery of recurrent metastases may represent one option in a multi-modal treatment approach of patients suffering from locally recurrent cerebral metastases.

High-Frequency Spinal Cord Stimulation in Surgery-Naïve Patients-A Prospective Single-Center Study.

INTRODUCTION: A multitude of evidence supporting the beneficial effects of spinal cord stimulation (SCS) in patients suffering from chronic pain syndromes following spinal surgery has been published in the last decade. Evidence is scarce, however, for the use of high frequency SCS (HF-SCS) in the treatment of surgery naïve patients suffering from lower back pain (LBP). METHODS: From June 2014 to April 2015, we prospectively enrolled patients suffering from LBP alone or in conjunction with leg pain in a trial of HF-SCS. None of the patients had undergone surgical procedures of the lumbar spine. Patients suffered medically intractable LBP and were deemed ineligible for spine surgery. All patients underwent trial stimulation for at least one week. Pain levels were assessed daily during initial stay, 4 weeks later and then every 3 months. Different preprogrammed modes of HF-SCS were changed if pain persisted or increased during trial or postimplant follow-up (FU). RESULTS: Eight patients (four male, four female) underwent HF-SCS trials. Mean age was 60 ± 4.8 years. Mean numeric rating scale (NRS) baseline intensity for back pain was 8.9 ± 0.23 and 8.1 ± 0.6 for leg pain. All patients achieved meaningful reductions in pain intensities and underwent IPG implantation at a mean interval of 13 days. Mean follow-up was 306 days. Mean back pain reduction from baseline at last follow-up was -4.13 ± 0.85, and -6.2 ± 1.03 for leg pain. Two patients showed skin irritations and localized pain at the IPG site. Both patients underwent surgery to replant the IPG. No infections were seen in any of the eight patients enrolled. CONCLUSIONS: In this prospective cohort of surgery naïve patients, we were able to show good efficacy of HF-SCS with mean NRS reductions of 4.13 and 6.2 for back and leg pain, respectively, after a mean follow-up of 10 months.

Intraoperative Indocyanine Green-Based Cortical Perfusion Assessment in Patients Suffering from Severe Traumatic Brain Injury.

OBJECTIVES: The pathophysiology of traumatic brain injury (TBI) largely involves the brains vascular structural integrity. We analyzed the value of an intraoperative cortical indocyanine green (ICG) angiography in patients with severe TBI and acute subdural hematoma who underwent decompressive craniectomy. METHODS: ICG-derived fluorescence curves of cortex and cerebral vessels were recorded by the use of software integrated into a surgical microscope in 10 patients. The maximum intensity, rise time (RT), time to peak, and residual fluorescence intensity (FI) were estimated from cortical arteries, the parenchyma, and veins. RESULTS: ICG-derived fluorescence parameters were correlated with the short-term outcome 3 months after discharge. Five patients had a favorable and 5 an unfavorable outcome. Patients with a favorable outcome showed a significant longer RT in the arteries and a trend towards a significant longer RT in the veins. Overall mean residual FI was 47.5 ± 6.8% for the arteries, 45.0 ± 7% for the parenchyma and 57.6 ± 6% for the veins. The residual FI of the parenchyma and the veins was significantly greater in patients with an unfavorable clinical outcome. CONCLUSIONS: Patients with an unfavorable clinical outcome showed an altered shape of the ICG-derived fluorescence curve, a shorter increase of the ICG-derived fluorescence intensity in the cortical arteries, and significantly greater residual fluorescence intensity. These observations are likely a correlate of an increased intracranial pressure, a capillary leak, and venous congestion. Intraoperative quantification of the ICG-derived fluorescence might help to appreciate the clinical outcome in patients with severe TBI.

Intraoperative neurophysiological monitoring during resection of infratentorial lesions: the surgeon's view.

OBJECTIVE Methods of choice for neurophysiological intraoperative monitoring (IOM) within the infratentorial compartment mostly include early brainstem auditory evoked potentials, free-running electromyography, and direct cranial nerve (CN) stimulation. Long-tract monitoring with somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) is rarely used. This study investigated the incidence of IOM alterations during posterior fossa surgery stratified for lesion location. METHODS Standardized CN and SEP/MEP IOM was performed in 305 patients being treated for various posterior fossa pathologies. The IOM data were correlated with lesion locations and histopathological types as well as other possible confounding factors. RESULTS Alterations in IOM were observed in 158 of 305 cases (51.8%) (CN IOM alterations in 130 of 305 [42.6%], SEP/MEP IOM alterations in 43 of 305 [14.0%]). In 15 cases (4.9%), simultaneous changes in long tracts and CNs were observed. The IOM alterations were followed by neurological sequelae in 98 of 305 cases (32.1%); 62% of IOM alterations resulted in neurological deficits. Sensitivity and specificity for detection of CN deficits were 98% and 77%, respectively, and 95% and 85%, respectively, for long-tract deficits. Regarding location, brainstem and petroclival lesions were closely associated with concurrent CN IOM and SEP/MEP alterations. CONCLUSIONS The incidence of IOM alterations during surgery in the posterior fossa varied widely between different lesion locations and histopathological types. This analysis provides crucial information on the necessity of IOM in different surgical settings. Because MEP/SEP and CN IOM alterations were commonly observed during posterior fossa surgery, the authors recommend the simultaneous use of both modalities based on lesion location.