Propofol Anesthesia Depth Monitoring Based on Self-Attention and Residual Structure Convolutional Neural Network.

METHODS: We compare nine index values, select CNN+EEG, which has good correlation with BIS index, as an anesthesia state observation index to identify the parameters of the model, and establish a model based on self-attention and dual resistructure convolutional neural network. The data of 93 groups of patients were selected and randomly grouped into three parts: training set, validation set, and test set, and compared the best and worst results predicted by BIS. RESULT: The best result is that the model's accuracy of predicting BLS on the test set has an overall upward trend, eventually reaching more than 90%. The overall error shows a gradual decrease and eventually approaches zero. The worst result is that the model's accuracy of predicting BIS on the test set has an overall upward trend. The accuracy rate is relatively stable without major fluctuations, but the final accuracy rate is above 70%. CONCLUSION: The prediction of BIS indicators by the deep learning method CNN algorithm shows good results in statistics.

Monitoring of Anesthesia by Bispectral Analysis of EEG Signals.

BACKGROUND: In intensive care, monitoring the depth of anesthesia during surgical procedures is a key element in the success of the medical operation and postoperative recovery. However, despite the development of anesthesia thanks to technological and pharmacological advances, its side effects such as underdose or overdose of hypnotics remain a major problem. Observation and monitoring must combine clinical observations (loss of consciousness and reactivity) with tools for real-time measurement of changes in the depth of anesthesia. Methodology. In this work, we will develop a noninvasive method for calculating, monitoring, and controlling the depth of general anesthesia during surgery. The objective is to reduce the effects of pharmacological usage of hypnotics and to ensure better quality recovery. Thanks to the overall activity of sets of neurons in the brain, we have developed a BIS technique based on bispectral analysis of the electroencephalographic signal EEG. Discussion. By collecting the electrical voltages from the brain, we distinguish light sleep from deep sleep according to the values of the BIS indicator (ranging from 0 : sleep to 100 : wake) and also control it by acting on the dosage of propofol and sevoflurane. We showed that the BIS value must be maintained during the operation and the anesthesia at a value greater than 60. CONCLUSION: This study showed that the BIS technology led to an optimization of the anesthetic management, the adequacy of the hypnotic dosage, and a better postoperative recovery.

Intraoperative Neurological Monitoring in Lower Limb Surgery for Patients With Mucopolysaccharidoses.

BACKGROUND: There are reports of spinal cord injury (SCI) occurring after lower extremity (LE) surgery in children with mucopolysaccharidoses (MPS). Intraoperative neurological monitoring (IONM) has been adopted in some centers to assess real-time spinal cord function during these procedures. The aim of this investigation was to review 3 specialty centers' experiences with MPS patients undergoing LE surgery. We report how IONM affected care and the details of spinal cord injuries in these patients. METHODS: All pediatric MPS patients who underwent LE surgery between 2001 and 2018 were reviewed at 3 children's orthopaedic specialty centers. Demographic and surgical details were reviewed. Estimated blood loss (EBL), surgical time, positioning, use of IONM, and changes in management as a result of IONM were recorded. Details of any spinal cord injuries were examined in detail. RESULTS: During the study period, 92 patients with MPS underwent 252 LE surgeries. IONM was used in 83 of 252 (32.9%) surgeries, and intraoperative care was altered in 17 of 83 (20.5%) cases, including serial repositioning (n=7), aggressive blood pressure management (n=6), and abortion of procedures (n=8). IONM was utilized in cases with larger EBL (279 vs. 130 mL) and longer operative time (274 vs. 175 min) compared with procedures without IONM. Three patients without IONM sustained complete thoracic SCI postoperatively, all from cord infarction in the upper thoracic region. These 3 cases were characterized by long surgical time (328±41 min) and substantial EBL (533±416 mL or 30.5% of total blood volume; range, 11% to 50%). No LE surgeries accompanied by IONM experienced SCI. CONCLUSIONS: Patients with MPS undergoing LE orthopaedic surgery may be at risk for SCI, particularly if the procedures are long or are expected to have large EBL. One hypothesis for the etiology of SCI in this setting is hypoperfusion of the upper thoracic spinal cord due to prolonged intraoperative or postoperative hypotension. IONM during these procedures may mitigate the risk of SCI by identifying real-time changes in spinal cord function during surgery, inciting a change in the surgical plan. LEVEL OF EVIDENCE: Level III-retrospective comparative series.

Influence of Intraoperative Microelectrode Recording in Deep Brain Stimulation.

BACKGROUND: There is considerable debate regarding the use of intraoperative microelectrode recording (MER) in deep brain stimulation (DBS). OBJECTIVE: To determine if the use of intraoperative MER impacts the final position of the lead implant in DBS of the subthalamic nucleus (STN) and globus pallidus (GPi) and to evaluate the incidence of complications. METHODS: The authors conducted a retrospective chart review of all patients who underwent STN and GPi DBS with MER, at the University of Texas Health Science Center in Houston from June 1, 2009 to October 1, 2013 to compare initial and final coordinates. Hemorrhagic and infectious complications were reviewed. RESULTS: A total of 90 lead implants on 46 patients implanted at the center during this time period were reviewed and included in the study. A statistically significant difference between the initial and final coordinates was observed in the superior-inferior direction with a mean difference of 0.40 mm inferiorly (±0.96 mm, P<0.05) and 0.96 mm inferiorly (±1.32 mm, P<0.05) in the STN and GPi locations, respectively. A nonstatistically significant difference was also observed in the anterior-posterior direction in both locations. There were no intraparenchymal hemorrhages on postoperative computed tomography. Two patients developed postoperative seizures (7.4%). One STN electrode (1.1%) required revision because of a suboptimal response. CONCLUSIONS: Intraoperative MER in STN and GPi DBS implant does not seem to have a higher rate of surgical complications compared with historical series not using MER and might also be useful in determining the final lead location.

Comparison of electroencephalogram between propofol- and thiopental-induced anesthesia for awareness risk in pregnant women.

There have been few comparative studies using electroencephalogram (EEG) spectral characteristics during the induction of general anesthesia for cesarean section. This retrospective study investigated the differences in the depth of anesthesia through EEG analysis between propofol- and thiopental-induced anesthesia. We reviewed data of 42 patients undergoing cesarean section who received either thiopental (5 mg/kg) or propofol (2 mg/kg). EEG data were extracted from the bispectral index (BIS) monitor, and 10-second segments were selected from the following sections: 1) Stage I, BIS below 60 after induction; 2) Stage II, after intubation completion; 3) Stage III, end-tidal sevoflurane above 0 vol%. The risk of awareness was represented by the BIS and entropy measures. In Stage III, the thiopental group (n = 20) showed significantly higher BIS value than the propofol group (n = 22) (67.9 [18.66] vs 44.5 [20.63], respectively, p = 0.002). The thiopental group had decreased slow-delta oscillations and increased beta-oscillations as compared to the propofol group in Stages II and III (p < 0.05). BIS, spectral entropy, and Renyi permutation entropy were also higher in the thiopental group at Stages II and III (p < 0.05). In conclusion, frontal spectral EEG analysis demonstrated that propofol induction maintained a deeper anesthesia than thiopental in pregnant women.

Monitoring the level of hypnosis using a hierarchical SVM system.

Monitoring level of hypnosis is a major ongoing challenge for anesthetists to reduce anesthetic drug consumption, avoiding intraoperative awareness and prolonged recovery. This paper proposes a novel automated method for accurate assessing of the level of hypnosis with sevoflurane in 17 patients using the electroencephalogram signal. In this method, a set of distinctive features and a hierarchical classification structure based on support vector machine (SVM) methods, is proposed to discriminate the four levels of anesthesia (awake, light, general and deep states). The first stage of the hierarchical SVM structure identifies the awake state by extracting Shannon Permutation Entropy, Detrended Fluctuation Analysis and frequency features. Then deep state is identified by extracting the sample entropy feature; and finally light and general states are identified by extracting the three mentioned features of the first step. The accuracy of the proposed method of analyzing the brain activity during anesthesia is 94.11%; which was better than previous studies and also a commercial monitoring system (Response Entropy Index).

IONM and thyroidectomy in benign thyroid disease. Analysis of adverse events.

OBJECTIVES: The aim of this study is to identify statistically significant differences in the onset of postoperative complications in patients undergoing thyroid surgery for benign pathology, following the systematic introduction of intraoperative neuromonitoring (IONM) of the laryngeal nerves. MATERIALS AND METHODS: In this study we have retrospectively analysed data of 604 consecutive patients underwent to thyroidectomy in the Unit of General Surgery - University Hospital of Parma between January 2011 and December 2017. All patients were divided in two groups: the first group of patients was operated without the use of IONM (Group A) the second group was operated after the introduction of the systematic use of IONM (Group B). We have compared the incidence of adverse events in these two groups, analysing the impact of IONM on the onset of the most frequent complications after thyroid surgery. We have considered the impact of other variables in both groups, such as thyroiditis, hyperfunction and gland sinking in mediastinum. RESULTS: No statistically significant differences in the incidence between Group A (patients operated without the use of IONM) and Group B (patients operated with the use of IONM) were detected, though a decreasing trend after the introduction of IONM was observed. No statistically significant differences were reported even analysing the influence of other patient's variables such as thyroiditis, hyperfunction and glandular sinking in mediastinum. CONCLUSION: Even if the number of patients considered is not sufficient to value statistically significant differences, the decreasing trend of the incidence of postoperative complications after introduction of IONM encourage us. The surgeon expertise is still the most relevant variable influencing the decreasing of postoperative complications, underlining the importance of the centralization of this kind of surgery in the high volume centres.

Accuracy of intraoperative electrophysiological testing in confirming correct cochlear implant electrode positions.

Objective: To investigate the accuracy of intraoperative electrophysiological studies in detecting incorrectly positioned electrodes in cochlear implant surgery. Study design: A retrospective chart review. Setting: Tertiary referral centre. Patients: In total, 104 consecutive patients with a mean age of 5 years underwent cochlear implant surgery at our centre between January 2012 and December 2013. All patients were implanted with Cochlear Nucleus Freedom implants. Method: A retrospective study to compare intraoperative neural response telemetry (NRT), impedance and electrode position using Stenver's transorbital plain X-ray view. Results: Intraoperative electrophysiological tests for patients with Cochlear Nucleus Freedom implants showed 97% sensitivity and 100% specificity compared with postoperative X-ray imaging. Conclusion: NRT results for the position of cochlear implants were very accurate when checked by X-ray imaging showing that this technique is sufficient in most cases. Stenver's plain X-ray view is needed in complicated cases with abnormal NRT testing or difficult electrode insertion.

Practice Patterns in Parathyroid Surgery: A Survey of Asia-Pacific Parathyroid Surgeons.

BACKGROUND: Practice variations exist amongst parathyroid surgeons depending on their expertise and resources. Our study aims to elucidate the choice of surgical techniques and adjuncts used in parathyroid surgery by surgeons in the Asia-Pacific region. METHODS: A 25-question online survey was sent to members of five endocrine surgery associations. Questions covered training background, practice environment and preferred techniques in parathyroid surgery. Respondents were divided into three regions: Australia/New Zealand, South/South East Asia and East Asia, and responses were analysed according to region, specialty, case volume and years in practice. RESULTS: One hundred ninety-six surgeons returned the questionnaire. Most surgeons (98%) routinely perform preoperative imaging, with 75% preferring dual imaging with 99mTcsestamibi and ultrasound. Ten per cent of surgeons use parathyroid 4DCT as first-line imaging, more commonly in East Asia (p = 0.038). Minimally invasive parathyroidectomy is the favoured technique of choice (97%). Most surgeons reporting robotic or endoscopic approaches are from East Asia. Rapid intraoperative parathyroid hormone is accessible to just under half of the surgeons but less available in Australian/New Zealand (p < 0.001). The use of intraoperative neuromonitoring is not commonly used, even less so amongst Asian surgeons (p = 0.048) and surgeons with low case load (p = 0.013). CONCLUSION: Dual localisation techniques are the preferred choice of investigations in preparation for parathyroid surgery, with minimally invasive surgery without neuromonitoring the preferred approach. Use of adjuncts is sporadic and limited to certain centres.

Laryngeal force sensor metrics are predictive of increased perioperative narcotic requirements.

OBJECTIVES/HYPOTHESIS: To determine the relationship between force metrics measured by the laryngeal force sensor (LFS) during suspension microlaryngoscopy (SML) and perioperative narcotic requirements. STUDY DESIGN: Prospective observational study. METHODS: Compressive tissue forces were recorded during SML using the LFS and correlated with postoperative narcotic requirements in the postanesthesia care unit (PACU) at an academic tertiary center. Patients were prospectively enrolled and had force metrics recorded throughout each procedure including maximum force, average force, suspension time, and total impulse. Narcotic administration in the intraoperative period and PACU were also recorded and converted into intravenous morphine equivalents (ME). Surgeons were blinded to the force recordings during surgery to prevent operator bias. RESULTS: Eighty-two patients completed the study. Of these patients, the mean perioperative ME requirement was 16.96 mg (range, 0.15-79.82 mg). Univariate analysis demonstrated a positive correlation between perioperative narcotic requirements and total suspension time (P < .001) as well as total impulse (P = .007). A positive correlation was also seen with maximum force, although not significantly. On multiple linear regression, total suspension time was a significant predictive variable for perioperative narcotic use, with a marginal incremental increase of 0.273 mg of ME per minute of total suspension time (0.273 mg/min, 95% confidence interval: 0.040-0.507 mg/min, P = .022). CONCLUSIONS: Intraoperative force metrics including total suspension time are predictive of increased perioperative narcotic requirement after SML. Total impulse during SML may also correlate with increased perioperative narcotic requirements. LEVEL OF EVIDENCE: 2 Laryngoscope, 129:2563-2567, 2019.

Prediction of Postoperative Vocal Fold Function After Intraoperative Recovery of Loss of Signal.

OBJECTIVES/HYPOTHESIS: This multicenter study aimed to 1) evaluate early postoperative vocal fold function in relation to intraoperative amplitude recovery, and 2) determine optimal absolute and relative thresholds of intraoperative amplitude recovery heralding normal early postoperative vocal fold function, both after segmental type 1 and after global type 2 loss of signal (LOS). STUDY DESIGN: Prospective outcome study. METHODS: This study, encompassing nine surgical centers from four countries, correlated intraoperative amplitude recovery with early postoperative vocal fold function using receiver operating characteristic analysis. RESULTS: Included in this study were 68 patients, 48 women and 20 men, who sustained transient recurrent laryngeal nerve injury during thyroid surgery under continuous intraoperative nerve monitoring. Early transient vocal fold palsy was seen in 18 (64%) of 28 patients with ipsilateral segmental LOS type 1, and in 10 (25%) of 40 patients with ipsilateral global LOS type 2. On receiver operating characteristic analysis, relative amplitude thresholds were superior to absolute amplitude thresholds in predicting vocal fold function after LOS type 2 (area under the curve [AUC]: 0.83 vs. 0.65; P = .01 vs. P = .15; Youden index 44% and 253 µV) and LOS type 1 (AUC: 0.96 vs. 0.97; P < .001 each; Youden index 49% and 455 µV). Amplitude recovery ≥50% of baseline after LOS always indicated intact vocal fold function. CONCLUSIONS: When the nerve amplitude recovers ≥50% of baseline after segmental LOS type 1 or global LOS type 2, it is appropriate to extend completion thyroidectomy to the other side during the same session. LEVEL OF EVIDENCE: 2b Laryngoscope, 129:525-531, 2019.

Recurrent laryngeal nerve paralysis after thyroid cancer surgery and intraoperative nerve monitoring.

OBJECTIVES/HYPOTHESIS: This study aimed to investigate the risk of postoperative recurrent laryngeal nerve paralysis (RLNP) with and without the use of intraoperative nerve monitoring (IONM) during thyroid cancer surgery. STUDY DESIGN: Retrospective cohort study. METHODS: This study utilized a nationwide claims database in Japan. Patients who underwent thyroid cancer surgery with and without IONM were included, and postoperative RLNP incidence was compared. RESULTS: The study included 5,804 patients. Multivariable logistic regression analysis revealed that use of IONM was not associated with increased RLNP risk (odds ratio: 1.15; 95% confidence interval: 0.67-1.96). There was no significant effect on RLNP prevention when stratified by tumor or nodal classification. Rather, the patients who had T4 or N1b classifications who received IONM had higher incidences of RLNP. CONCLUSIONS: Use of IONM did not significantly reduce the risk of RLNP. The results for the T4 and N1b populations may be explained by indication bias or unmeasured confounders. LEVEL OF EVIDENCE: NA Laryngoscope, 129:1954-1960, 2019.

Influence of Intraoperative Neuromonitoring on the Outcomes of Surgeries for Pediatric Scoliosis in the United States.

BACKGROUND: Intraoperative neuromonitoring (IONM) is used to detect impending neurologic damage during complex spinal surgeries. Although IONM is increasingly used during pediatric scoliosis surgeries in the United States, the effect of IONM on the outcomes of such surgeries at a national level is unclear. METHODS: Using National Inpatient Sample (NIS) from 2009 to 2012, 32,305 spinal fusions performed in children 18 years old or younger of age with scoliosis were identified using ICD-9 procedure and diagnosis codes. IONM was identified using the ICD-9 procedure code 00.94. The effects of IONM use on length of stay (LOS), discharge disposition, hospital charges, and in-hospital complications were assessed using multivariate regression analysis adjusting for patient and hospital characteristics. RESULTS: IONM was used in 5,706 (18%) of the surgeries. IONM was associated with increased home discharge (adjusted odds ratio [AOR] = 1.25 [95% confidence interval 1.10-1.40], p = .001). There was no difference in LOS (p = .096) and hospital charges (p = .750). Neurologic complications were noted in 52 (0.9%) surgeries using IONM and 368 (1.4%) surgeries without IONM (p = .005). Although IONM use trended toward lower risk of neurologic complications in multivariate analysis, it failed to achieve statistical significance (AOR = 0.77 [0.57-1.04], p = .084). CONCLUSIONS: Reported use of IONM in this database was significantly less compared with other databases, suggesting that IONM might be underreported in the NIS database. Nevertheless, in this database, IONM was significantly associated with increased home discharge. Hospital charges and LOS were not affected by IONM. There was a trend toward lower risk of neurologic complications with IONM use, though this finding was not statistically significant.

The impact and value of uni- and multimodal intraoperative neurophysiological monitoring (IONM) on neurological complications during spine surgery: a prospective study of 2728 patients.

PURPOSE: We compared the value of different uni- and multimodal intraoperative neurophysiological monitoring (IONM) methods on the detection of neurological complications during spine surgery. METHODS: IONM data derived from sensory spinal and cortical evoked potentials combined with continuous electromyography monitoring, motor evoked potentials and spinal recording were evaluated in relation to subsequent post-operative neurological changes. Patients were categorised based on their true-positive or true-negative post-operative neurological status. RESULTS: In 2728 consecutive patients we had 909 (33.3%) IONM alerts. We had 8 false negatives (0.3%) with post-operative radicular deficit that completely recovered within 3 months, except for one. There was no false negative for spinal cord injury. 107 were true positives, and 23 were false positives. Multimodal IONM sensitivity and specificity were 93.0% and 99.1%, respectively. The frequency of neurological complications including minor deficits was 4.2% (n = 115), of which 0.37% (n = 10) were permanent. Analysis of the single IONM modalities varied between 13 and 81% to detect neurological complications compared with 93% when using all modalities. CONCLUSION: Multimodal IONM is more effective and accurate in assessing spinal cord and nerve root function during spine surgeries to reduce both neurological complications and false-negative findings compared to unimodal monitoring. We recommend multimodal IONM in all complex spine surgeries. These slides can be retrieved from Electronic Supplementary Material.

Usefulness of Ultrasound-Guided Microsurgery in Cavernous Angioma Removal.

BACKGROUND: Primary elements of surgical treatment of cavernous angiomas (CAs) are precise lesion identification and optimal trajectory determination. Navigation techniques allow for better results compared to microsurgery alone. In this study, we examined the benefits of intraoperative ultrasound (IOUS) use as an adjunct to standard localization systems. METHODS: We retrospectively analyzed 59 CAs, comparing outcomes in 2 groups of patients: 34 who underwent frame-based or frameless navigation-assisted microsurgery (no-IOUS group) and 25 who underwent IOUS-guided microsurgery associated with these techniques (IOUS group). RESULTS: The use of IOUS did not significantly increase the surgery time (mean, 172 ± 1.7 minutes in the IOUS group and 192.6 ± 11.5 in no-IOUS group; P = 0.08). In all 25 patients in the IOUS group, IOUS allowed for ready identification of CA as a hyperechoic mass. At the last follow-up (mean, 41.7 ± 3.5 months postsurgery), 95.2% of the IOUS group and 80.8% of the no-IOUS group had a modified Rankin Scale score of 0-1 and an Extended Glasgow Outcome Scale score of 7-8 (P = 0.2), with 100% and 64%, respectively, included in Engel outcome scale class IA (P = 0.006). Complete removal, as confirmed on postoperative magnetic resonance imaging, was achieved in all patients in the IOUS group and in almost all (97.1%; P = 0.4) patients in the no-IOUS group. CONCLUSIONS: IOUS is a valid tool for the intraoperative identification of CAs. Implementation of standard localization methods with IOUS guidance was associated with complete resection in all cases, without increasing surgical time. Compared with microsurgery without IOUS guidance, long-term functional outcomes showed better trends, and the epilepsy-free rate was significantly higher.

Safeness and Utility of Concomitant Intraoperative Monitoring with Intraoperative Magnetic Resonance Imaging in Children: A Pilot Study.

BACKGROUND: High-field intraoperative magnetic resonance imaging (MRI) has become increasingly available in neurosurgery centers. There is little experience with combined intraoperative MRI and intraoperative neurophysiologic monitoring (IONM). We report the first series, to our knowledge, of pediatric patients undergoing brain tumor surgery with 3T intraoperative MRI and IONM. METHODS: This pilot study included all consecutive children operated on for brain tumors between October 2013 and April 2016 in whom concomitant intraoperative MRI and somatosensory evoked potentials and motor evoked potentials were used. Neuromonitoring findings and related complications of all cases were retrospectively analyzed. RESULTS: During a 30-month period, 17 children (mean age 8.4 years; 3 girls) undergoing surgery met the study criteria. During intraoperative MRI, 483 IONM needles were left in place. Of these needles, 119 were located on the scalp, 94 were located above the chest, and 270 were located below the chest. Two complications with skin burns (first degree) were observed. In all patients, neuromonitoring was still reliable after MRI. In 1 case, a threshold increase for motor evoked potential stimulation (20 mA) was necessary after intraoperative MRI; in 2 cases, a reduction of 50% of the somatosensory evoked potential amplitude at the end of the surgery was observed compared with the values obtained before intraoperative MRI. CONCLUSIONS: The combination of intraoperative MRI and IONM can be safely used in pediatric patients. IONM data acquisition after intraoperative MRI was feasible and remained reliable.

Trends in Intraoperative Testing During Cochlear Implantation.

OBJECTIVE: No consensus guidelines exist regarding intraoperative testing during cochlear implantation and wide variation in practice habits exists. The objective of this observational study was to survey otologists/neurotologists to understand practice habits and overall opinion of usefulness of intraoperative testing. STUDY DESIGN: Cross-sectional survey. SETTING: A web-based survey was sent to 194 practicing Otologists/Neurotologists. MAIN OUTCOME MEASURES: Questions included practice setting and experience, habits with respect to electrodes used, intraoperative testing modalities used, overall opinion of intraoperative testing, and practice habits in various scenarios. RESULTS: Thirty-nine of 194 (20%) completed the survey. For routine patients, ECAPs and EIs were most commonly used together (38%) while 33% do not perform testing at all. Eighty-nine percent note that testing "rarely" or "never" changes management. Fifty-one percent marked the most important reason for testing is the reassurance provided to the family and/or the surgeon. CONCLUSION: Intraoperative testing habits and opinions regarding testing during cochlear implantation vary widely among otologic surgeons. The majority of surgeons use testing but many think there is minimal benefit and that surgical decision-making is rarely impacted. The importance of testing may change as electrodes continue to evolve.

Somatosensory evoked potentials after decompressive craniectomy for traumatic brain injury.

Somatosensory evoked potentials (SSEPs) are used for neuroprognosis after severe traumatic brain injury (TBI). However decompressive craniectomy (DC), involving removal of a portion of the skull to alleviate elevated intracranial pressure, is associated with an increase in SSEP amplitude. Accordingly, SSEPs are not available for neuroprognosis over the hemisphere with DC. We aim to determine the degree to which SSEP amplitudes are increased in the absence of cranial bone. This will serve as a precursor for translation to clinically prognostic ranges. Intra-operative SSEPs were performed before and after bone flap replacement in 22 patients with severe TBI. SSEP measurements were also performed in a comparison non-traumatic group undergoing craniotomy for tumor resection. N20/P25 amplitudes and central conduction time were measured with the bone flap in (BI) and out (BO). Linear regressions, adjusting for skull thickness and study arm, were performed to evaluate the contribution of bone presence to SSEP amplitudes. Latencies were not different between BO or BI trials in either group. Mean N20/P25 amplitudes recorded with BO were statistically different (p = 0.0001) from BI in both cohorts, showing an approximate doubling in BO amplitudes. For contralateral-ipsilateral montages r2 was 0.28 and for frontal pole montages r2 was 0.62. Cortical SSEP amplitudes are influenced by the presence of cortical bone as is particularly evident in frontal pole montages. Larger, longitudinal trials to assess feasibility of neuroprognosis over the hemisphere with DC in severe TBI patients are warranted.