Svatopluk Ostrý

Experience of 500 cases of neurophysiological monitoring in carotid endarterectomy

SummaryBackground. Experience with Intraoperative monitoring using neurophysiological and haemodynamic indices in 500 operations for carotid endarterectomy is reported. Methods. Transcranial Doppler technique (TCD), electroencephalogram (EEG) and bilateral median somatosensory evoked potentials (SEP) were performed. Latency and amplitude of SEP, spectral analysis of EEG signal and blood flow velocity in the medial cerebral artery (MCA) were continuously measured. Findings. After two consecutive drops of N20/P25 complex of more than 50%, a warning was given, and when the decrease continued, an the alarm raised. Abnormal EEG changes, if any, appeared after a significant decrease in the N20/P25 amplitude. A mean blood flow velocity drop below 40% of the reference value after cross clamping was rated as a significant warning event.A warning as a result of a decrease in N20/P25 amplitude occurred in 80 operations (16.0%), after an spectral edge frequency decrease in 2 cases (0.4%) and after a Vmean decrease in 21 cases (4.2%). False negative results were experienced in 2 patients (0.4%). A shunt was inserted in 2.8% of the operations. The overall mortality/morbidity rate was 2.4%. Conclusion. A decrease of more than 50% in the amplitude of the thalamocortical somatosensory evoked potential complex N20/P25 proved to be the most reliable warning of danger of ischaemia during carotid endarterectomy.

Intraoperative MR imaging in a case of a cervical spinal cord lesion

The aim of this article is to describe the feasibility of performing intraoperative MR imaging in patients with spinal cord lesions and the potential value of this technique. The authors report a case involving a 28-year-old man who presented with chronic cervical pain and pain along the ulnar side of the forearms during neck flexion. Findings on clinical examination were normal, but MR imaging revealed a multicystic cervical spinal cord lesion. Surgery was undertaken to open the cysts, evacuate old blood, and search for pathological tissue. Intraoperative MR imaging showed that the caudal cyst was not opened, and surgery was therefore continued. The caudal cyst was fenestrated and a suspected small cavernous malformation was removed. Electrophysiological monitoring was performed both before and after the intraoperative MR imaging. The use of intraoperative MR imaging changed the strategy of the procedure and helped the surgeon to safely enter all the cysts in the cervical cord.

Multifunctional Surgical Suite (MFSS) with 3.0 T iMRI: 17 Months of Experience

The 3T ioMRI in Prague is composed of two independent suites: the operating theatre and the 3T MR suite, both of which can and do work independently. They are connected by a double door and a special transportation system. The whole operating table is moved on rails to and from the MR gantry. Anaesthesiological equipment is built from paramagnetic material, which is also moved to and from the MR suite. The integral parts of the multifunctional surgical suite (MFSS) are the neuronavigation system, electrophysiological monitoring, surgical microscope with availability of indocyanin green angiography and fluorescence-guided glioma resection technique and endoscopy equipment. The operating theatre is equipped in a normal fashion with the exception of a head holder that is paramagnetic. MR radiologist and MR assistants are alerted approximately 30 min before the requested intraoperative and out-patient service is interrupted to clean the MR suite. The ioMRI takes 15-20 min and immediately after the door closes the out patient activity is resumed. Intraoperative MR was performed in 332 surgeries in the first 17 months of operation. The most frequent indications were pituitary adenomas, followed by gliomas. Other indications were less frequent and included meningiomas, cavernomas, aneurysms, epilepsy surgery, intramedullary lesions, non-pituitary sellar lesions, metastases and various other surgeries. In 332 cases no technical or medical complication connected with ioMRI was encountered.

O38: Subcortical mapping and intraoperative diffusion tensor tractography 3.0T of the corticospinal tract in supratentorial intrinsic tumor surgery. Reliability study

Question: What is the agreement in spindle scoring within, between and among experts? How does spindle scoring by humans compare to automated spindle scoring algorithms? Methods: We crowd-sourced the collection of spindle scorings from 24 experts in a large and varied dataset of EEG (C3-M2) from 110 middle-aged sleeping subjects. Epochs were scored by an average of 5.3 unique experts. Two experts scored parts of the dataset multiple times. We developed a simple method to build a large gold standard by establishing group consensus among expert scorers. We tested the performance of six previously published automated spindle detectors against the gold standard and refined methods of performance analysis for event detection. Results: We found an interrater agreement (F1-score) of 61±6% (Cohen’s Kappa (κ): 0.52±0.07) averaged over 24 expert pairs and an intrarater agreement of 72±7% (κ: 0.66±0.07) averaged over two experts. We tested the performance of individual experts to a gold standard compiled from all the expert scorers and found average agreement of 75±6% (κ: 0.68) over the 24 experts. We recompiled the gold standard and excluded the single expert whose performance was being assessed, and found an average agreement of 67±7% (κ: 0.59). Overall, we found the performance of human experts to be significantly better than the automated sleep spindle detectors we tested (maximum F1-score of detectors: 52%). Conclusions: Sleep spindle characteristics between subjects are very diverse which makes the scoring task difficult. The low interrater reliability suggests using more than one expert when scoring a dataset.