Florian Sohm

Accuracy of stereotactic electrode placement in deep brain stimulation by intraoperative computed tomography

The purpose of this study was to evaluate the accuracy of stereotactic electrode placement in patients undergoing deep brain stimulation by using pre- and postoperative computed tomography (CT). Twenty-three patients with movement disorders (Parkinsons disease (n=7), tremor (n=9), dystonia (n=7)) treated with bilateral deep brain stimulation (DBS) (overall 46 target points) were investigated. The target point of the electrode was planned stereotactically in combination with a preoperative stereotactic helical computed tomography (CT). A postoperative CT, which was carried out still in the operating room while the patient had the stereotactic frame on the head, was performed in order to control the position of the electrodes in relation to the previously planned target point. The position of the four electrode contacts was measured according to the Talairach space (AC-PC line) and compared with the coordinates of the planned target point. The mean spatial distance of planned target perpendicular to the electrode was 1.32+/-0.75mm. These results show the high accuracy of stereotactic implantation of DBS electrodes assisted by pre- and postoperative image fusion with computed tomography (CT).

High dose Erythropoietin increases Brain Tissue Oxygen Tension in Severe Vasospasm after Subarachnoid Hemorrhage

BackgroundVasospasm-related delayed cerebral ischemia (DCI) significantly impacts on outcome after aneurysmal subarachnoid hemorrhage (SAH). Erythropoietin (EPO) may reduce the severity of cerebral vasospasm and improve outcome, however, underlying mechanisms are incompletely understood. In this study, the authors aimed to investigate the effect of EPO on cerebral metabolism and brain tissue oxygen tension (PbtO2).MethodsSeven consecutive poor grade SAH patients with multimodal neuromonitoring (MM) received systemic EPO therapy (30.000 IU per day for 3 consecutive days) for severe cerebral vasospasm. Cerebral perfusion pressure (CPP), mean arterial blood pressure (MAP), intracranial pressure (ICP), PbtO2 and brain metabolic changes were analyzed during the next 24 hours after each dose given. Statistical analysis was performed with a mixed effects model.ResultsA total of 22 interventions were analyzed. Median age was 47 years (32–68) and 86 % were female. Three patients (38 %) developed DCI. MAP decreased 2 hours after intervention (P < 0.04) without significantly affecting CPP and ICP. PbtO2 significantly increased over time (P < 0.05) to a maximum of 7 ± 4 mmHg increase 16 hours after infusion. Brain metabolic parameters did not change over time.ConclusionsEPO increases PbtO2 in poor grade SAH patients with severe cerebral vasospasm. The effect on outcome needs further investigation.

Parenteral diclofenac infusion significantly decreases brain-tissue oxygen tension in patients with poor-grade aneurysmal subarachnoid hemorrhage

IntroductionDiclofenac, a nonsteroidal antiinflammatory drug, is commonly used as antipyretic therapy in intensive care. The purpose of this study was to investigate the effects of parenteral diclofenac infusion on brain homeostasis, including brain-tissue oxygen tension (PbtO2) and brain metabolism after aneurysmal subarachnoid hemorrhage (aSAH).MethodsWe conducted a prospective, observational study with retrospective analysis of 21 consecutive aSAH patients with multimodal neuromonitoring. Cerebral perfusion pressure (CPP), mean arterial pressure (MAP), intracranial pressure (ICP), body temperature, and PbtO2 were analyzed after parenteral diclofenac infusion administered over a 34-minute period (20 to 45 IQR). Data are given as mean ± standard error of mean and median with interquartile range (IQR), as appropriate. Time-series data were analyzed by using a general linear model extended by generalized estimation equations (GEEs).ResultsOne-hundred twenty-three interventions were analyzed. Body temperature decreased from 38.3°C ± 0.05°C by 0.8°C ± 0.06°C (P < 0.001). A 10% decrease in MAP and CPP (P < 0.001) necessitated an increase of vasopressors in 26% (n = 32), colloids in 33% (n = 41), and crystalloids in 5% (n = 7) of interventions. PbtO2 decreased by 13% from a baseline value of 28.1 ± 2.2 mm Hg, resulting in brain-tissue hypoxia (PbtO2 <20 mm Hg) in 38% (n = 8) of patients and 35% (n = 43) of interventions. PbtO2 <30 mm Hg before intervention was associated with brain-tissue hypoxia after parenteral diclofenac infusion (likelihood ratio, 40; AUC, 93%; 95% confidence interval (CI), 87% to 99%; P < 0.001). Cerebral metabolism showed no significant changes after parenteral diclofenac infusion.ConclusionsParenteral diclofenac infusion after aSAH effectively reduces body temperature, but may lead to CPP decrease and brain-tissue hypoxia, which were both associated with poor outcome after aSAH.

Frame-based vs frameless placement of intrahippocampal depth electrodes in patients with refractory epilepsy: a comparative in vivo (application) study.

BACKGROUND:Despite progress in imaging technologies, documentation of unifocal electrical excitability is pivotal in patient selection for epilepsy surgery. OBJECTIVE:To compare the application accuracy of the Vogele-Bale-Hohner system (VBH), a maxillary fixation system with an external fiducial frame permitting frameless stereotactic guidance, with that of conventional frame-based stereotaxy for placement of intrahippocampal depth electrodes (DEs) in patients with refractory epilepsy. METHODS:Retrospective study. Comparison of two patient cohorts with DEs implanted along the occipitotemporal axis (group A, VBH; group B, frame-based stereotaxy). In vivo accuracy (lateral target localization error [TLE]), determined postoperatively by measuring the normal distance between virtual target and real electrode position at the tip and at 4cm from the tip, number of electrode contacts within the target structure, and diagnostic quality of electroencephalogram recordings were compared. RESULTS:Seventeen DEs (A, 6 electrodes, 60 contacts; B, 11 electrodes, 90 contacts) were placed. electroencephalogram recordings via DEs supported further treatment decisions in all patients. TLE was 2.433 ± 0.977 mm (SD) (95% confidence interval [CI], 1.715-3.214 mm) (A) and 1.803 ± 0.392 mm (SD) (95% CI,1.511-2.195 mm) (B) (P = .185). Maximal error was 4 mm (A) and 3.2 mm (B). TLE 4 cm from the tip was 2.166 ± 2.188 mm (SD) (95% CI,0.438-3.916 mm) (A) and 1.372 ± 0.548 mm (SD) (95% CI,1.049-1.695 mm) (B) (P = .39). Maximal error 4 cm from the tip was 6.4 mm (A) and 2.14 mm (B). On average, 7 (A) and 5 (B) electrode contacts were placed in the target region. CONCLUSION:The VBH and frame-based systems offer similar in vivo accuracy for intrahippocampal DE placement. With frame-based methods, accuracy is higher but the number of contacts per side is lower. This does not translate to clinically important differences.

Cerebral tau is elevated after aneurysmal subarachnoid haemorrhage and associated with brain metabolic distress and poor functional and cognitive long-term outcome

Background Recent evidence suggests axonal injury after aneurysmal subarachnoid haemorrhage (aSAH). The microtubule-associated protein, tau, has been shown to be elevated in the cerebrospinal fluid after aSAH, however, brain extracellular tau levels and their relation to long-term neurological and cognitive outcomes have not been investigated. Methods Serial cerebral microdialysis (CMD) samples were collected from 22 consecutive aSAH patients with multimodal neuromonitoring to determine CMD-total-tau by ELISA. CMD-total-tau was analysed considering other brain metabolic parameters, brain tissue oxygen tension (PbtO2), and functional and neuropsychological outcome at 12 months. All outcome models were analysed using generalised estimating equations with an autoregressive working correlation matrix to account for multiple measurements of brain extracellular proteins per subject. Results CMD-total-tau levels positively correlated with brain extracellular fluid levels of lactate (r=0.40, p<0.001), glutamate (r=0.45, p<0.001), pyruvate (r=0.26, p<0.001), and the lactate-pyruvate ratio (r=0.26, p<0.001), and were higher in episodes of hypoxic (PbtO2<20 mm Hg) brain extracellular lactate elevation (>4 mmol/L) (p<0.01). More importantly, high CMD-total-tau levels were associated with poor functional outcome (modified Rankin Scale ≥4) 12 months after aSAH even after adjusting for disease severity and age (p=0.001). A similar association was found with 3/5 neuropsychological tests indicative of impairments in cognition, psychomotor speed, visual conceptualisation and frontal executive functions at 1 year after aSAH (p<0.01). Conclusions These results suggest that CMD-total tau may be an important biomarker for predicting long-term outcome in patients with severe aSAH. The value of axonal injury needs further confirmation in a larger patient cohort, preferably combined with advanced imaging techniques.

Clusters of Cortical Spreading Depolarizations in a Patient with Intracerebral Hemorrhage: A Multimodal Neuromonitoring Study

BackgroundSpontaneous intracerebral hemorrhage (ICH) is associated with high morbidity and mortality. Cortical spreading depolarizations (CSDs) increase brain matrix metalloproteinase (MMP)-9 activity leading to perihematomal edema expansion in experimental ICH.MethodsThe purpose of this report is to describe cerebral metabolic changes and brain extracellular MMP-9 levels in a patient with CSDs and perihematomal edema expansion after ICH.ResultsWe present a 66-year-old male patient with ICH who underwent craniotomy for hematoma evacuation. Multimodal neuromonitoring data of the perihematomal region revealed metabolic distress and increased MMP-9 levels in the brain extracellular fluid during perihematomal edema progression. At the same time, subdural electrocorticography showed clusters of CSDs, which disappeared after ketamine anesthesia on day six. Perihematomal edema regression was associated with decreasing cerebral MMP-9 levels.ConclusionsThis novel association between clusters of CSDs, brain metabolic distress, and increased MMP-9 levels expands our knowledge about secondary brain injury after ICH. The role of ketamine after this devastating disorder needs further studies.

Neuroinflammation is Associated with Brain Extracellular TAU-Protein Release after Spontaneous Subarachnoid Hemorrhage

INTRODUCTION Animal data suggest an association between neuroinflammation and secondary brain injury including axonal injury after aneurysmal subarachnoid hemorrhage (aSAH). We sought to study the association between brain extracellular interleukin (IL)-6 and TAU-protein levels as a surrogate marker for neuroinflammation and axonal injury in patients with poor grade aSAH. METHODS Prospectively collected data from 26 consecutive poor-grade aSAH patients with multimodal neuromonitoring including cerebral microdialysis (CMD) were retrospectively analyzed. IL-6 and TAU-protein levels were analyzed using ELISA from a single CMD-sample every 24 hours and correlated with brain metabolic and hemodynamic parameters. Patients were dichotomized to highgrade (N=10) or low-grade (N=16) neuroinflammation according to their median CMD-IL-6 levels. Data were analyzed using generalized estimating equations to account for multiple within-subject measurements. RESULTS Perilesional probe location (P=0.02) and aSAH related intracerebral hemorrhage (aICH) volume (P=0.003) at admission were associated with high-grade neuroinflammation. Brain extracellular TAU-protein levels (P=0.001), metabolic distress and delayed cerebral infarction (DCI; P=0.001) were linked to high-grade neuroinflammation. Relative or absolute phosphor-TAU levels were not correlated with CMD-IL-6 levels. High-grade neuroinflammation was a predictor for worse outcome three months after ictus, independently from probe location, initial Hunt&Hess grade and age (P=0.01). CONCLUSION Neuroinflammation after aSAH is associated with intraparenchymal bleeding, deranged cerebral metabolism and TAU-protein release. The impact of potential anti-inflammatory treatment strategies on secondary brain injury after aSAH has to be investigated in future studies.

Refractory status epilepticus in a patient with short bowel syndrome—A microdialysis study

Alois J. Schiefecker *, Ronny Beer , Josef Steidl , Florian Sohm, Andrea Griesmacher , Alexander K. Brendel , Iris Unterberger , Marlene Fischer , Anelia Dietmann , Bettina Pfausler , Claudius Thome , Erich Schmutzhard , Raimund Helbok a Division of Neurocritical Care, Department of Neurology, Medical University Innsbruck, Austria Central Institute of Medical and Chemical Laboratory Diagnostics, Medical University Innsbruck, Austria Department of Neurosurgery, Medical University Innsbruck, Austria

Refractory intracranial hypertension in traumatic brain injury: Proposal for a novel score to assess the safety of lumbar cerebrospinal fluid drainage

Background: Cerebrospinal fluid (CSF) drainage via ventricular puncture is an established therapy of elevated intracranial pressure (ICP). In contrast, lumbar CSF removal is believed to be contraindicated with intracranial hypertension. Methods: We investigated the safety and efficacy of lumbar CSF drainage to decrease refractory elevated ICP in a small cohort of patients with traumatic brain injury (TBI). A score (0–8 points) was used to assess computed tomography (CT) images for signs of herniation and for patency of the basal cisterns. All patients received lumbar CSF drainage either as a continuous drainage or as a single lumbar puncture (LP). Type and method of CSF drainage, mean ICP 24 h prior and after CSF removal, and adverse events were documented. Outcome was assessed after 3 months (with dichotomized Glasgow outcome scale). Results: Eight patients were evaluated retrospectively. n = 5 suffered a moderate, n = 2 a severe TBI (one Glasgow coma score not documented). The CT score was ≥5 in all patients prior to LP and decreased after puncture without clinical consequences in two patients. The amount of CSF removal did not correlate with score changes (P = 0.45). CSF drainage led to a significant reduction of mean ICP (from 22.3 to 13.9 mmHg, P = 0.002). Continuous drainage was more effective than a single LP. Three of eight patients reached a favorable outcome. Conclusions: Lumbar CSF removal for the treatment of intracranial hypertension is effective and safe, provided the basal cisterns are discernible, equivalent to ≥5 points in the proposed new score. The score needs further validation.