Can NIRS be a surrogate indicator of elective shunt in carotid endarterectomy? A single-center observational retrospective study says no.

BACKGROUND: Neuromonitoring during carotid endarterectomy (CEA) under general anesthesia is desirable and may be useful for preventing brain ischemia, but the selection of the most appropriate method remains controversial. PURPOSE: To determine the effectiveness of near infrared spectroscopy (NIRS) compared to multimodality intraoperative neuromonitoring (IONM) in indicating elective shunts and predicting postoperative neurological status. METHODS: This is a retrospective observational study including 86 consecutive patients with CEA under general anesthesia. NIRS and multimodality IONM were performed during the procedure. IONM included electroencephalography (EEG), somatosensory evoked potentials (SSEPs) and transcranial motor-evoked potentials (TcMEPs). Sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated for each neuromonitoring modality. RESULTS: NIRS presented a sensitivity and a specificity for detecting brain ischemia of 77.7% and 89.6%, respectively (PPV = 46.6% and NPV = 97.2%). In contrast, a 100% sensitivity and specificity for multimodality IONM was determined (PPV and NPV = 100%). No significant difference (in demographical or clinical data) between "true positive" and "false-positive" patients was identified. Among the methods included in multimodality IONM, EEG showed the best results for predicting postoperative outcome after CEA (PPV and NPV=100%). CONCLUSION: NIRS is inferior to multimodality IONM in detecting brain ischemia and predicting postoperative neurological status during CEA under general anesthesia.

Anaesthesia and multimodality intraoperative neuromonitoring in carotid endarterectomy. Chronological evolution and effects on intraoperative neurophysiology.

Contingency data was retrospectively collected to evaluate the historical and current ability to provide multimodality intraoperative neurophysiological monitoring during carotid endarterectomy under two conditions: total intravenous anaesthesia (TIVA) and low dose halogenated anaesthesia (SEVO). 229 patients were monitored during carotid endarterectomy procedures under general anaesthesia between 2012 and 2020. 121 Patients were monitored with SEVO at a minimum alveolar concentration less than 0.7 and 108 were monitored using TIVA, according to common anaesthetic practice standards in our hospital across the years. Multimodality IONM was established with electroencephalography, somatosensory evoked potentials and motor evoked potentials. As compared to TIVA, patients monitored with SEVO showed significantly higher motor evoked potential thresholds (313.52 ± 77.74 SEVO and 218.93 V ± 103.2 V TIVA p < 0.05) and lower reproducibility. Electroencephalography and somatosensory evoked potentials showed no significant differences among the groups. When using SEVO, multimodality intraoperative neurophysiological monitoring during carotid endarterectomy could mask or miss a motor isolated change in patients in spite of low dose minimum alveolar concentration and of apparently adequate electroencephalography and somatosensory evoked potentials for monitoring. Given these difficulties, we believe the chronological transfer to TIVA could have improved our ability to establish multimodality intraoperative neurophysiological monitoring during carotid endarterectomy in recent times.

Direct cortical stimulation with cylindrical depth electrodes in the interhemispheric fissure for leg motor evoked potential monitoring.

OBJECTIVE: To evaluate cylindrical depth electrodes in the interhemispheric fissure as an alternative to subdural strip electrodes for direct cortical stimulation (DCS) leg motor evoked potential (MEP) monitoring. METHODS: A cylindrical depth electrode was positioned in the interhemispheric fissure of 37 patients who underwent supratentorial brain surgery. Leg sensory and motor cortices were localized by highest tibial nerve somatosensory evoked potential amplitude and lowest DCS leg MEP threshold; the lowest-threshold electrode was then used for DCS leg MEP monitoring. RESULTS: Intraoperative leg MEPs were obtained from all the patients in the series. The mean intensity applied for leg MEP monitoring with the cylindrical depth electrode was 15.2 ± 4.0 mA. No complications secondary to neurophysiological monitoring were detected. CONCLUSIONS: Lower extremity MEPs were consistently recorded using a multi-contact cylindrical depth electrode in the interhemispheric fissure by DCS. SIGNIFICANCE: Cylindrical depth electrodes may be a safe and effective alternative for DCS in the interhemispheric fissure, where subdural strips are difficult to place.

Facial canal dehiscence in patients with cholesteatoma: concordance between intraoperative inspection, computed tomography and neurophysiological findings.

OBJECTIVES: To assess the diagnostic capacity of intraoperative neurophysiological monitoring with respect to "gold standard" microscopic findings of facial canal dehiscence in middle ear cholesteatoma surgery. STUDY DESIGN, PATIENTS AND SETTING: We carried out a retrospective cohort study of 57 surgical interventions for cholesteatoma between 2008 and 2013 at Hospital Universitario de Canarias, Spain. DIAGNOSTIC INTERVENTIONS: Each patient underwent preoperative computed tomography (CT), intraoperative neurophysiological monitoring and intraoperative inspection of the facial nerve during microsurgery. Diagnostic concordance on the presence/absence of facial canal dehiscence was assessed in 54 surgical interventions. MAIN OUTCOME: Presence of facial canal dehiscence. RESULTS: Of 57 interventions, 39 were primary surgeries; 11 (28.2%) showed facial canal dehiscence. and 18 were revision surgeries; 6 (33.3%) showed facial canal dehiscence. The facial nerve was not damaged in any patient. Facial canal dehiscence was observed in 17 (29.82%) interventions. We used intraoperative microscopic findings as the gold standard. Neurophysiological study showed a sensitivity of 94.1, specificity 97.3, positive predictive value (PPV) 57.8 and negative predictive value of 97.2. CT showed a sensitivity of 64.7, specificity 78.4, PPV 57.8 and negative predictive value of 82. CONCLUSIONS: Our neurophysiological study showed greater sensitivity and higher PPV than CT for the detection of facial canal dehiscence. We found no relationship between disease progression time and the presence of facial canal dehiscence.

Novel approach to continuous neurophysiological monitoring during surgery of peripheral nerve tumors.

BACKGROUND: Intraoperative neurophysiological monitoring (IONM) with nerve action potential (NAP) can be useful during peripheral nerve surgery. However, current methodologies are not optimized for continuous recording of the NAP. The use of newer electrodes may make it possible to more conveniently obtain continuous recordings of the NAP during surgery. METHODS: After localizing the nerve of interest and dissecting it from the adjacent soft tissue, two APS® (Automatic Periodic Stimulation) electrodes, originally designed for stimulation of the vagus nerve during thyroid surgery, are placed on the nerve on either sides of the tumor for stimulation and recording using two subdermal electroencephalogram (EEG) needles as anode and reference, respectively. Both monopolar and bipolar recordings can be used as appropriate. Anesthesia regime comprised sevoflurane or total intravenous anesthesia (TIVA). No muscle relaxant after intubation, local anesthesia, or blood pressure cuff is used during the surgery. RESULTS: Twelve patients (6 male, 6 female) with peripheral nerve tumors (motor, sensitive, or mixed nerves) or tumors affecting the peripheral nerves were monitored in our center since 2014 (mean age: 50 years; 28-79). In 10 patients, the NAP was monitored without experiencing any changes from the beginning till the end of the surgery; in these patients, no postoperative deficit was adverted. In the last 2 patients, who departed from a complete neurological deficit, no NAP was recorded at the baseline or during the surgery, and they did not experience any neurological improvement. CONCLUSION: The vagus nerve stimulation electrodes open new possibilities in peripheral nerve IONM. We have used them for continuous monitoring without additional problems with the traditional probes.

What Can We Learn From Two Consecutive Cases? Droperidol May Abolish TcMEPs.

Droperidol is a D2 receptor antagonist currently used in Europe for preventing postoperative nausea and vomiting. It was used to perform neurolept anaesthesia in combination with fentanyl until a Food and Drug Administration (FDA) 'black box' warning restricted its use due to cardiovascular side effects in 2001. There is no literature regarding the effects of droperidol on transcranial motor evoked potentials (TcMEPs) elicited by electrical stimulation. Our aim was to report two cases of spine surgery in which TcMEPs were lost due to droperidol administration. We report the cases of a 4-year-old male with scoliosis undergoing correction and a 58-year-old woman with metastasis on the D8 vertebrae undergoing kyphosis correction. Intraoperative neurophysiological monitoring was achieved through TcMEPs and somatosensory evoked potentials (SEPs). Intraoperative neurophysiological monitoring (IONM) showed a temporal loss of TcMEPs without SEPs changes coinciding with the administration of droperidol. TcMEP stimulation parameters were changed to double train of pulses, with the aim to elicit them, obtaining responses. Five minutes after droperidol administration, TcMEPs were equal to those at baseline. Droperidol used as prophylaxis for postoperative nausea abolishes TcMEPs. Changing stimulation parameters to double train of pulses, it allows to bypass droperidol central action, achieving monitorable TcMEPs.

Low Prevalence of Sleep Disorders in Demyelinating Disease in a Northern Tenerife Population.

STUDY OBJECTIVES: Sleep disorders are seen in patients with demyelinating disease (DD) more often than in the general population. Combination of physical and psychological factors such as pain, spasms, nocturia, depression, anxiety, or medication effects could contribute to sleep disruption. Frequently, these disturbances have a major impact on health and quality of life of patients. The aim of this study was to estimate the prevalence of sleep disorders in patients seen in the DD consultation. METHODS: 240 patients; mean age 43 years, 187 women; 163 patients with multiple sclerosis (MS): 144 relapsing-remitting, 19 progressive forms, 36 clinically isolated syndrome, 26 radiological isolated syndrome, and 15 patients with others DD. All participants completed questionnaires: Pittsburgh, Epworth, and Stanford scales, indirect symptoms of RLS and Obstructive Sleep Apnea, Fatigue Severity Scale, and Multiple Sclerosis Quality of Life-54. RESULTS: Moderate/severe insomnia 12.5%, OSA 5.8%, RLS 9.6% (confirmed 3 cases), narcolepsy 0, fatigue (> 4) 24.6%. Physical QoL 66.6 ± 19.6, Mental QoL 66.1 ± 21.9. Patients with an established diagnosis showed higher scores on insomnia compared to the group of CIS and RIS (F = 3.85; p = 0.023), no differences were in the other parameters. Fatigue showed high correlation with insomnia (r = 0.443; p < 0.001), RLS (r = 0.513; p < 0.001), and sleepiness (r = 0.211; p = 0.001). None of the variables included in the regression model were shown to be predictors of Physical and Mental QoL. CONCLUSIONS: A high percentage of our sample sleeps well. Emphasize the low prevalence of sleep disorders (insomnia, fatigue, RLS, etc). We detected an overestimation in the RLS questionnaire and the low QoL recorded.

Suprasegmental neurophysiological monitoring with H reflex and TcMEP in spinal surgery. Transient loss due to hypotension. A case report.

OBJECTIVE: H-reflex is a well known neurophysiological test used to evaluate sensory afferent and motor efferent impulses of S1 root. Despite its simplicity and feasibility, it is not used very often in the operating room. METHODS: We report the case of a 16-year-old male patient who undergoes a surgical correction for a severe paralytic scoliosis (160°). On account of previous deficits, intraoperative neurophysiological monitoring was achieved through TcMEP and H-reflex. RESULTS: Intraoperative neurophysiological monitoring (IONM) showed a transient and simultaneous loss of bilateral TcMEP and H-reflex, coinciding with an abrupt hypotension during pedicle screw placement. After having dismissed mechanical injury and after increasing blood pressure, TcMEP and H-reflex were equivalent to those at baseline. CONCLUSIONS: The H-reflex is a classic neurophysiological test not used very frequently in the operating room. It is a feasible and reliable technique that can be helpful during spine surgery IONM, especially in patients with preexisting neurological deficits. Although simultaneous TcMEP and H-reflex monitoring has been previously described, to our knowledge, this is the first recorded case of a decline in both associated with abrupt hypotension.

Electrical stimulation threshold in chronically compressed lumbar nerve roots: Observational study.

OBJECTIVES: Intraoperative neuromonitoring (IONM) is a common practice in spinal surgery, mostly during pedicle screw placement. However, there is not enough information about the factors that can interfere with IONM data. One of these factors may be existing damage of the nerve root whose function must be preserved. The main purpose of the present study is to evaluate the effect of chronic compression in lumbar nerve roots in terms of stimulation thresholds during direct nerve stimulation. PATIENTS AND METHODS: Direct electrical stimulation was performed in 201 lumbar nerve roots during lumbar spinal procedures under general anaesthesia in 80 patients with different lumbar spinal pathologies. Clinical and radiological data were reviewed in order to establish the presence of chronic compression. RESULTS: Chronically compressed nerve roots showed a higher stimulation threshold than non compressed nerve roots (11.93 mA vs. 4.33 mA). This difference was confirmed with intra-subject comparison (paired sample t test, p=0.012). No other clinical factors were associated with this higher stimulation threshold in lumbar nerve roots. CONCLUSION: A higher stimulation threshold is present in compressed lumbar nerve roots than non compressed roots. This needs to be taken into consideration during pedicle screw placement, where intraoperative neurophysiological monitoring is being used.

Role of multimodal intraoperative neurophysiological monitoring during positioning of patient prior to cervical spine surgery.

OBJECTIVE: To determine the use of multimodal intraoperative neurophysiological monitoring (IONM) during positioning procedures in cervical spine surgery. METHODS: IONM data was collected from 75 patients from the onset of positioning to the end of the surgical procedure. These included: transcranial motor evoked potentials (TcMEP), somatosensory evoked potentials (SEP) and free running electromyography (EMG) recordings. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (PNV) were calculated. RESULTS: IONM warnings were given in 5 cases during neck positioning. These consisted of the disappearance of TcMEP in all the cases, while two cases showed a loss of SEPs as well. Four of these patients presented a complete recovery of TcMEP and SEPs after neck repositioning. The patient in which this recovery was not present, woke up with new postoperative neurological deficits. Sensitivity, specificity, PPV and NPV of TcMEP during cervical positioning were all 100%. Sensitivity of SEPs was 40%; specificity and PPV were 100%; and the NPV of SEPs was 95.9%. CONCLUSION: Multimodal IONM is a useful method to prevent spinal cord injury during neck positioning in cervical spine surgical procedures. TcMEPs showed the highest sensitivity in detecting injuries to cervical spine related to neck positioning. SIGNIFICANCE: Multimodal IONM should not only be considered for detecting intra-operative warnings, but also during positioning.

Parálisis del sueño hipnopómpica con alucinaciones y síndrome de estallido cefálico: una asociación infrecuente / Hypnopompic sleep paralysis with hallucinations and exploding brain syndrome: an infrequent association

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