Evaluation of a new cortical strip electrode for intraoperative somatosensory monitoring during perirolandic brain surgery

OBJECTIVE: During neurosurgical procedures, strip electrodes should have low impedance and sufficient adherence on the brain surface. We evaluated the signal quality, safety, and performance of a novel strip electrode (WISE Cortical Strip, WCS®), with conductive electrode contacts created with platinum nanoparticles embedded in a polymer base. METHODS: In a multicenter interventional, non-inferiority study, we compared WCS to a conventional strip electrode (Ad-Tech). We recorded impedance and somatosensory evoked potentials (SEP) and determined the signal-to-noise ratio (SNR). We performed direct stimulation of the motor cortex. An external clinical event committee rated safety and adverse events and users rated usability. RESULTS: During 32 brain surgeries in the paracentral region, WCS was rated safe and effective in signal transmission. Two seizure events were classified as probably related to the stimulation with WCS. The users rated WCS adhesion to the brain as satisfactory but reported difficulties sliding the WCS under the dura. The median (IQR) impedance of WCS was lower than for Ad-Tech: 2.7 (2.3-3.7) vs 5.30 (4.3-6.6) kΩ (p < 0.005). The SNR of SEP was non-inferior for WCS compared to Ad-Tech. CONCLUSIONS: The impedance of WCS was lower than Ad-Tech without safety limitations. In small craniotomies not exposing the motor cortex its use may be limited. SIGNIFICANCE: Low impedance electrodes facilitate recordings with high SNR

Intramedullary spinal cord cavernous malformations-association between intraoperative neurophysiological monitoring changes and neurological outcome

Background Microsurgical resection of spinal cord cavernous malformations can be assisted by intraoperative neurophysiological monitoring (IONM). While the clinical outcome after surgical resection has been discussed in several case series, the association of intraoperative IONM changes and detailed neurological outcome, however, has not been analyzed so far. Methods Seventeen patients with spinal cavernomas underwent surgery between 02/2004 and 06/2020. Detailed neurological and clinical outcome as well as IONM data including motor-evoked potential (MEP) and somatosensory-evoked potential (SSEP) monitoring were retrospectively analyzed. Intraoperative IONM changes were compared to outcome at 3-month and 1-year follow-up in order to identify surrogate parameters for an impending neurological deficit. Results Compared to the preoperative state, McCormick score at 1-year follow-up remained unchanged in 12 and improved in five patients, none worsened, while detailed neurological examination revealed a new or worsened sensorimotor deficit in 4 patients. The permanent 80% amplitude reduction of MEP and 50% amplitude reduction of SSEP showed the best diagnostic accuracy with a sensitivity of 100% and 67% respectively and a specificity of 73% and 93% respectively. The relative risk for a new neurological deficit at 1-year follow-up, when reversible IONM-deterioration was registered compared to irreversible IONM deterioration, was 0.56 (0.23-1.37) for MEP deterioration and 0.4 (0.18-0.89) for SSEP deterioration. Conclusions Reversible IONM changes were associated with a better neurological outcome at follow-up compared to irreversible IONM deterioration during SCCM surgery. Our study favors the permanent 80% amplitude reduction criterion for MEP and 50% amplitude reduction criterion for SSEP for further prospective evaluation of IONM significance and the effectiveness of corrective maneuvers during SCCM surgeries

Experimental Study of the Course of Threshold Current, Voltage and Electrode Impedance During Stepwise Stimulation From the Skin Surface to the Human Cortex

<p>Background: Transcranial electric stimulation as used during intraoperative neurostimulation is dependent on electrode and skull impedances.</p><p>Objective: Threshold currents, voltages and electrode impedances were evaluated with electrical stimulation at 8 successive layers between the skin and the cerebral cortex.</p><p>Patients and Methods: Data of 10 patients (6f, 53 +/- 11 years) were analyzed. Motor evoked potentials were elicited by constant current stimulation with corkscrew type electrodes (CS) at C3 and C4 in line with standard transcranial electric stimulation. A monopolar anodal ball tip shaped probe was used for all other measurements being performed at the level of the skin, dura and cortex, as well as within the skull by stepwise performed burr holes close to C3 resp. C4.</p><p>Results: Average stimulation intensity, corresponding voltage and impedance for muscle MEPs at current motor threshold (CMT) were recorded: CS 54 +/- 23 mA (mean +/- SD), 38 +/- 21 V. 686 +/- 146 Omega; with the monopolar probe on skin 55 +/- 28 mA, 100 +/- 44 V. 1911 +/- 683 Omega and scalp 59 +/- 32 mA, 56 +/- 28 V. 1010 +/- 402 Omega; within the skull bone: outer compact layer 33 23 mA, 91 +/- 53 V. 3734 +/- 2793 Omega; spongiform layer 33 +/- 23 mA, 70 +/- 44 V.2347 +/- 1327 Omega; inner compact layer (ICL) 28 +/- 19 mA, 48 +/- 23 V. 2103 +/- 14980; on dura 25 +/- 12 mA, 17 +/- 12 V.643 +/- 244 Omega and cortex 14 +/- 6 mA, 11 +/- 5 V.859 +/- 300 Omega. CMTs were only significantly different for CS (P = 0.02) and for the monopolar probe between the cortex and ICL (P = 0.03), scalp (P = 0.01) or skin (P = 0.01) and between ICL and CS (P</p><p>Conclusion: The mean stimulation current of the CMT along the extracranial to intracranial anodal trajectory followed a stepwise reduction. VMT was strongly dependent on electrode impedance. CMT within the skull layers was noted to have relative strong shunting currents in scalp layers. (C) 2013 Elsevier Inc. All rights reserved.</p>

Intraoperative electrical stimulation in awake craniotomy: methodological aspects of current practice.

There is increasing evidence that the extent of tumor removal in low-grade glioma surgery is related to patient survival time. Thus, the goal of resecting the largest amount of tumor possible without leading to permanent neurological sequelae is a challenge for the neurosurgeon. Electrical stimulation of the brain to detect cortical and axonal areas involved in motor, language, and cognitive function and located within the tumor or along its boundaries has become an essential tool in combination with awake craniotomy. Based on a literature review, discussions within the European Low-Grade Glioma Group, and illustrative clinical experience, the authors of this paper provide an overview for neurosurgeons, neurophysiologists, linguists, and anesthesiologists as well as those new to the field about the stimulation techniques currently being used for mapping sensorimotor, language, and cognitive function in awake surgery for low-grade glioma. The paper is intended to help the understanding of these techniques and facilitate a comparison of results between users

Proof of principle: supramarginal resection of cerebral metastases in eloquent brain areas

Cerebral metastases are not sharply delimitatable; therefore, microsurgical circumferential stripping of intracerebral metastases is often insufficient for preventing local tumor recurrence. Supramarginal resection significantly improves local tumor control but was suggested not to be suitable for metastases in eloquent brain areas. Therefore, we retrospectively analyzed a series of patients with cerebral metastases situated in eloquent areas for newly occurring neurologic deficits after supramarginal resection performed as awake surgery. A retrospective analysis was performed for all patients who underwent supramarginal resection for a cerebral metastasis performed as awake surgery between June 2011 and April 2012. All metastases were localized in eloquent brain areas. Pre- and postsurgical neurologic status was documented as well as data regarding the primary cancer and histopathologic data. Postoperative MRI within 72 h was scheduled routinely to verify complete resection. A total of 19 patients underwent awake surgery for a cerebral metastasis in eloquent brain areas. Surgery was well tolerated in all patients. Neurologic symptoms improved in five patients after surgery. In three patients, neurologic deficits existing before surgery worsened. The postoperative median National Institute of Health Stroke Scale (NIHSS) score did not differ from the preoperative value. Awake surgery is a feasible tool for metastases in eloquent areas, minimizing postoperative neurologic deficits and morbidity. Therefore, eloquently situated metastases may also be eligible for supramarginal resection. Further studies are needed in order to analyze the benefit of this method in achieving better tumor control

Letter: Guidelines for the use of electrophysiological monitoring for surgery of the human spinal column and spinal cord

[no abstract available