Unilateral abnormality of initial motor-evoked potential in the upper limb detected during lumbar spine surgery: a case report.

BACKGROUND: We present a case with abnormal findings of initial motor-evoked potential (MEP) in the left upper limb after prone positioning during lumbar spine surgery. CASE PRESENTATION: A 71-year-old man with bilateral lower extremity numbness without a history of preexisting motor weakness underwent L3-5 spinal fenestration. Initial MEP monitoring after prone positioning revealed markedly prolonged latency and lower amplitude in the left abductor pollicis brevis (APB). Because the left upper limb somatosensory-evoked potentials had normal values, a position-related impending peripheral nerve injury located between the neck and the forearm was excluded. Postoperative examination revealed that MEP abnormality in the left APB was caused by carpal tunnel syndrome. CONCLUSIONS: Abnormal initial MEP from the upper limb was unexpectedly detected after prone positioning during lumbar spine surgery. The condition was caused by preexisting carpal tunnel syndrome.

Which patients do we need to consider augmentation of muscle active potentials regarding transcranial electrical stimulation motor-evoked potentials monitoring before spine surgery?

BACKGROUND CONTEXT: Transcranial electrical stimulation motor-evoked potentials (Tc-MEPs) are the current trend and are important in preventing intraoperative neurological deficits. Post-tetanic Tc-MEPs (p-MEP) can augment the amplitudes of compound muscle active potentials (CMAPs), especially in the case of insufficient conventional Tc-MEPs (c-MEP). PURPOSE: To retrospectively investigate pre- and intraoperative factors necessitating p-MEP monitoring and to examine changes in the success rates of baseline Tc-MEP monitoring before and after tetanic stimulation in patients with such factors. STUDY DESIGN: Retrospective observational study. PATIENT SAMPLE: Patients (n=184) who underwent spinal surgery with Tc-MEP monitoring in our department between August 2020 and July 2022. OUTCOME MEASURES: Manual muscle testing (MMT) scores were calculated to identify patients with preoperative motor deficits. c-MEP and p-MEP amplitudes were recorded from the defined muscles. METHODS: We compared preoperative and intraoperative factors between the c-MEP and p-MEP groups (study 1). In cases where the factors were identified, we investigated the success rate of the baseline MEP measurement of each muscle before and after tetanic stimulation (study 2). RESULTS: One hundred fifty-seven patients were included. Of those, 87 showed sufficient CMAPs with c-MEP. Meanwhile, 70 needed p-MEP because of insufficient CMAPs. In univariate analysis, cervical/thoracic surgery (p<.001), preoperative MMT 3 or below (p=.009), shorter duration of illness (p=.037), previous cerebrovascular disease (p=.014), and dialysis (p=.031) were significantly associated with p-MEP group. Preoperative MMT 3 or below was the only factor requiring p-MEP (odds ratio, 3.34; 95% confidence interval, 1.28-8.73, p=.014) in multivariate analysis. In the p-MEP group, 24 patients had preoperative motor deficits; 16 patients with complete data were included in the analysis (study 2). The success rates of MEP monitoring before and after tetanic stimulation of the entire lower-extremity muscles were 42.7 and 57.3%, respectively (p<.001). The success rates for each muscle before and after tetanic stimulation were abductor pollicis brevis: 81.3% and 96.9%, tibialis anterior: 34.4% and 50.0%, gastrocnemius: 25% and 40.6%, and abductor hallucis: 68.8% and 81.3%, respectively. No significant differences were observed in success rates for any of the muscles. CONCLUSIONS: Patients with preoperative MMT 3 or below highly needed p-MEP. The success rate of baseline MEP monitoring increased with tetanic stimulation, even in patients with preoperative motor deficits. We believe that p-MEP monitoring can result in reliable CMAP recording, especially in cases of preoperative motor deficits with MMT scores of 3 or below.

Quantitative Analysis of Photochemical Reactions in Pentacene Precursor Films.

On-surface reactions are rapidly gaining attention as a chemical technique for synthesizing organic functional materials, such as graphene nanoribbons and molecular semiconductors. Quantitative analysis of such reactions is essential for fabricating high-quality film structures, but until our recent work using p-polarized multiple-angle incidence resolution spectrometry (pMAIRS), no analytical technique is available to quantify the reaction rate. In the present study, the pMAIRS technique is employed to analyze the photochemical reaction from 6,13-dihydro-6,13-ethanopentacene-15,16-dione to pentacene in thin films. The spectral analysis on a pMAIRS principle readily reveals the photoconversion rate accurately without other complicated calculations. Thus, this study underlines that the pMAIRS technique is a powerful tool for quantitative analysis of on-surface reactions, as well as molecular orientation.

Effect of Sevoflurane Anesthesia on Intraoperative Spikes, High-Frequency Oscillations, and Phase-Amplitude Coupling in MRI-Normal Hippocampus.

INTRODUCTION: The purpose of this study was to determine the effect of sevoflurane anesthesia on spikes, high-frequency oscillations (HFOs), and phase-amplitude coupling using a modulation index in MRI-normal hippocampus, with the aim of evaluating the utility of intraoperative electrocorticography in identifying the epileptogenic hippocampus during sevoflurane administration. METHODS: Eleven patients with intractable temporal lobe epilepsy with a normal hippocampus on MRI underwent extra-operative electrocorticography evaluation. Patients were assigned to the Ictal (+) or Ictal (-) group depending on whether the parahippocampal gyrus was included in the seizure onset zone. Intraoperative electrocorticography was performed under 0.5 and 1.5 minimum alveolar concentration of sevoflurane. The rates of spikes, ripples, fast ripples (FRs), ripples on spikes, FRs on spikes, and MI HFO(3-4 Hz) were evaluated. RESULTS: During the intraoperative electrocorticography procedure, sevoflurane administration was found to significantly increase the rate of spikes, ripples on spikes, fast ripples on spikes, and MI HFO(3-4 Hz) in the Ictal (+) group (P < 0.01). By contrast, the Ictal (-) group exhibited a paradoxical increase in the rate of ripples and fast ripple (P < 0.05). CONCLUSIONS: Our findings indicate that the administration of sevoflurane during intraoperative electrocorticography in patients with MRI-normal hippocampus can lead to a dose-dependent enhancement of epileptic biomarkers (spikes, ripples on spikes, fast ripples on spikes, and MI (HFO 3-4)) in the epileptogenic hippocampus, while paradoxically increasing the rate of ripples and fast ripple in the nonepileptogenic hippocampus. These results have significant implications for the identification of the MRI-normal hippocampus that requires surgical intervention and preservation of the nonepileptogenic hippocampus.

Utility of desflurane as an anesthetic in motor-evoked potentials in spine surgery and the facilitating effect in tetanic stimulation of bilateral median nerves.

Although desflurane is a safe and controllable inhalation anesthetic used in spinal surgery, to our knowledge, there have been no reports of successful motor-evoked potential (MEP) recordings under general anesthesia with desflurane alone. A high desflurane concentration may reduce the risk of intraoperative awareness but can also reduce the success of MEP recording. Therefore, we aimed to evaluate the reliability of MEP monitoring and investigate whether tetanic stimulation can augment MEP amplitude under general anesthesia with high-concentration desflurane during spinal surgery. We prospectively evaluated 46 patients who were scheduled to undergo lumbar surgery at a single center between 2018 and 2020. Anesthesia was maintained with an end-tidal concentration of 4% desflurane and remifentanil. Compound muscle action potentials were recorded bilaterally from the abductor pollicis brevis, abductor hallucis, tibialis anterior, gastrocnemius, and quadriceps. For post-tetanic MEPs (p-MEPs), tetanic stimulation was applied to the median nerves (p-MEPm) and tibial nerves (p-MEPt) separately before transcranial stimulation. The average success rates for conventional MEP (c-MEP), p-MEPm, and p-MEPt were 77.9%, 80%, and 79.3%, respectively. The p-MEPm amplitudes were significantly higher than the c-MEP amplitudes in all muscles (P < 0.05), whereas the p-MEPt amplitudes were not significantly different from the c-MEP amplitudes. The MEP recording success rates for the gastrocnemius and quadriceps were inadequate. However, bilateral median nerve tetanic stimulation can effectively augment MEPs safely under general anesthesia with high-concentration desflurane in patients who undergo spinal surgery.

Complexation study of a 1,3-phenylene-bridged cyclic hexa-naphthalene with fullerenes C60 and C70 in solution and 1D-alignment of fullerenes in the crystals.

To investigate the host ability of a simple macrocycle, 1,3-phenylene-bridged naphthalene hexamer N6, we evaluated the complexation of N6 with fullerenes in toluene and in the crystals. The complexes in the solid-state demonstrate the one-dimensional alignment of fullerenes. The single-crystals of the C60@N6 composite have semiconductive properties revealed by photoconductivity measurements.

Buckybowl and its chiral hybrids featuring eight-membered rings and helicene units.

Here we report the synthesis of a novel buckybowl (7) with a high bowl-to-bowl inversion barrier (ΔG‡ = 38 kcal mol-1), which renders the rate of inversion slow enough at room temperature to establish two chiral polycyclic aromatic hydrocarbons (PAHs). By strategic fusion of eight-membered rings to the rim of 7, the chiral hybrids 8 and 9 are synthesized and display helicity and positive and negative curvature, allowing the enantiomers to be configurationally stable and their chiroptical properties are thoroughly examined. Computational and experimental studies reveal the enantiomerization mechanisms for the chiral hybrids and demonstrate that the eight-membered ring strongly affects the conformational stability. Because of its static and doubly curved conformation, 9 shows a high binding affinity towards C60. The OFET performance of 7-9 could be tuned and the hybrids show ambipolar characteristics. Notably, the 9·C60 cocrystal exhibits well-balanced ambipolar performance with electron and hole mobilities of up to 0.19 and 0.11 cm2 V-1 s-1, respectively. This is the first demonstration of a chiral curved PAH and its complex with C60 for organic devices. Our work presents new insight into buckybowl-based design of PAHs with configurational stability and intriguing optoelectronic properties.

An Unsymmetrical 5,15-Disubstituted Tetrabenzoporphyrin: Effect of Molecular Symmetry on the Packing Structure and Charge Transporting Property.

Molecular design strategy to control the crystal structure of two-dimensional (2D) π-extended organic semiconductors has not been intensively explored. We synthesized an unsymmetric tetrabenzoporphyrin derivative (TIPS-Ph-BP) to demonstrate the effect of molecular symmetry on crystal packing. TIPS-Ph-BP formed an antiparallel slipped π-stacking and 2D herringbone-like structure. An unsymmetric structure would make 2D π-stacking more stable than a one-dimensional (1D) columnar structure to counteract steric and electronic imbalance in the crystal. As a result, TIPS-Ph-BP achieved the high hole mobility of 0.71 cm2 V-1 s-1.

Application of laser speckle flowgraphy to evaluate cerebral perfusion after carotid endarterectomy.

Cerebral hyperperfusion syndrome (CHS) after carotid endarterectomy (CEA) is devastating, and postoperative monitoring of cerebral perfusion is essential to prevent CHS. We report two cases of successful measurement of ocular blood flow using laser speckle flowgraphy (LSFG) for bedside assessment of the changes in cerebral perfusion after CEA. An 18.7% (case 1) and 47.7% (case 2) increase in ocular blood flow were measured postoperatively using LSFG compared with the baseline. LSFG might be applicable to evaluate cerebral perfusion after CEA.

Motor-evoked potential monitoring from urinary sphincter muscle during pediatric untethering surgery: a case series.

PURPOSE: Postoperative urinary dysfunction following untethering surgery for spinal lipoma is devastating. To assess urinary function, we invented a pediatric urinary catheter equipped with electrodes for the direct transurethral recording of myogenic potential from the external urethral sphincter (EUS). This paper presents two cases in which urinary function was monitored intraoperatively by recording of motor-evoked potential (MEP) from EUS during untethering surgery in children. METHODS: Two children (aged 2 and 6 years) were included in this study. One patient had no preoperative neurological dysfunction, while the other had frequent urination and urinary incontinence. A pair of surface electrodes was attached to a silicone rubber urethral catheter (6 or 8 Fr; diameter, 2 or 2.6 mm). The MEP from the EUS was recorded to assess the function of the centrifugal tract from the motor cortex to the pudendal nerve. RESULTS: Baseline MEP waveforms from the EUS were successfully recorded with latency and amplitude of 39.5 ms and 66 µV in patient 1 and 39.0 ms and 113 µV in patient 2, respectively. A significant decrease in amplitude was not observed during surgery in the two cases. No new urinary dysfunction and complications associated with the urinary catheter-equipped electrodes developed postoperatively. CONCLUSION: Using an electrode-equipped urinary catheter, monitoring of MEP from the EUS could be applicable during untethering surgery in pediatric patients.

An Atropisomerism Study of Large Cycloarylenes: [n]Cyclo-4,10-Pyrenylenes' Case.

An atropisomerism of large cycloarylenes was studied using [n]cyclo-4,10-pyrenylenes (n=6-21) as an illustrative example with two simple assumptions: (1) alternating configurations (R,S,R,S,…) are thermodynamically most stable, and (2) three consecutive identical configurations (R,R,R or S,S,S) are prevented. Ni-mediated coupling of a 5,9-diiodopyrene gave a series of directly-linked cyclic pyrene oligomers in one-pot reaction. As-synthesized cyclic hexamer was assigned as an (R,S,S,R,R,S) structure, converted into an (R,S,R,S,R,S)-form upon heating. Cyclic heptamer consists of two types of C2 symmetric structures predicted from assumption (2), one of which was convergent to one another by heating. Three atropisomers of cyclic octamer were analyzed from the possible five candidates by means of 1 H nuclear magnetic resonance (NMR) spectroscopy, and the conversion process to (R,S,R,S,R,S,R,S) configurations upon heating was investigated. In total, according to two simple rules, the analysis of atropisomerism could be performed smoothly.

Effects of intraoperative motor evoked potential amplification following tetanic stimulation of the pudendal nerve in pediatric craniotomy.

OBJECTIVE: Monitoring the intraoperative motor evoked potentials (MEPs) in pediatric craniotomy is challenging because of its low detection rate, which makes it unreliable. Tetanic stimulation of the peripheral nerves of the extremities and pudendal nerves prior to transcranial electrical stimulation (TES) or direct cortical stimulation (DCS) amplifies the MEPs. The authors investigated the effects of MEP amplification following tetanic stimulation of the median and tibial nerve or the pudendal nerve in pediatric patients undergoing craniotomy. METHODS: This prospective observational study included 15 patients ≤ 15 years of age (mean age 8.9 ± 4.9 years) undergoing craniotomy. MEPs were obtained with TES (15 cases) or DCS (8 cases)-conventional MEP without tetanic stimulation (c-MEP) and MEP following tetanic stimulation of the unilateral median and tibial nerves (mt-MEP) or following tetanic stimulation of the pudendal nerve (p-MEP) were used. Compound muscle action potentials were elicited from the abductor pollicis brevis, gastrocnemius, tibialis anterior, and abductor hallucis longus muscles. The authors compared the identification rate and the rate of amplitude increase of each MEP. RESULTS: For both TES and DCS, the identification and amplitude increase rates were significantly higher in cases without preoperative hemiparesis for p-MEPs than in those for c-MEPs and mt-MEPs. In comparison to patients with preoperative hemiparesis, p-MEPs displayed a higher identification rate, with fewer false negatives in DCS cases. CONCLUSIONS: In pediatric craniotomy, the authors observed the amplification effect of MEPs with pudendal nerve tetanic stimulation and the amplification effect of DCS on MEPs without increasing false negatives. These findings suggested the likelihood of more reliable intraoperative MEP monitoring in pediatric cases.

Correction: Phosphaacene as a structural analogue of thienoacenes for organic semiconductors.

Correction for 'Phosphaacene as a structural analogue of thienoacenes for organic semiconductors' by Kyohei Matsuo et al., Chem. Commun., 2022, 58, 13576-13579, https://doi.org/10.1039/D2CC05122B.

Resection of brachial plexus schwannomas while monitoring transcranial motor evoked potentials: report of two cases.

A schwannoma is a benign nerve sheath tumor treated by enucleation, which carries the risk of intraoperative nerve injury that is observed after awakening. Transcranial motor evoked potential (TcMEP) monitoring has been established as an effective method to predict and prevent intraoperative neurological complications during brain and spinal surgery. However, there have been few reports on its application in head and neck surgeries. We performed enucleation to relieve the symptoms due to schwannomas in the neck of two women, aged 25 years and 70 years. Both women presented with a left cervical mass, paresthesia of the left upper limb, and a Tinel-like sign without muscle weakness. TcMEPs were recorded before beginning surgery, during surgery, and immediately before completing surgery. The dissecting lines were decided using the stimulator attached to the dissecting instrument, which helped warn the surgeon regarding risky areas. Histopathological examinations confirmed the diagnosis of schwannoma. There was no significant difference in the pre- and postoperative TcMEP recordings, and no postoperative motor deficits were identified. Intraoperative TcMEP monitoring is expected to be useful in preventing operative complications while treating head and neck schwannomas.

On-surface synthesis of hydroxy-functionalized graphene nanoribbons through deprotection of methylenedioxy groups.

We demonstrate on-surface deprotection of methylenedioxy groups which yielded graphene nanoribbons (GNRs) with edges functionalized by hydroxy groups. While anthracene trimer precursors functionalized with hydroxy groups did not yield GNRs, it was found that hydroxy groups are first protected as methylenedioxy groups and then deprotected during the cyclo-dehydrogenation process to form GNRs with hydroxy groups. The X-ray photoemission spectroscopy and non-contact atomic force microscopy studies revealed that ∼20% of the methylenedioxy turned into hydroxy groups, while the others were hydrogen-terminated. The first-principles density functional theory (DFT) study on the cyclo-dehydrogenation process was performed to investigate the deprotection mechanism, which indicates that hydrogen atoms emerging during the cyclo-dehydrogenation process trigger the deprotection of methylenedioxy groups. The scanning tunneling spectroscopy study and DFT revealed a significant charge transfer from hydroxy to the Au substrate, causing an interface dipole and the HOMO being closer to the Fermi level when compared with hydrogen-terminated GNR/Au(111). This result demonstrates on-surface deprotection and indicates a possible new route to obtain GNRs with desired edge functionalization, which can be a critical component for high-performance devices.

Intraoperative Transcranial Motor-Evoked Potential Monitoring During Head and Neck Surgeries: A Case of Cervical Vagus Nerve Schwannoma With Laryngeal Paralysis.

Intraoperative transcranial motor-evoked potential (TcMEP) monitoring can effectively prevent neurological complications by enabling the evaluation of neurological deficits in all pathways from the motor cortex to the periphery. However, studies regarding its applicability in head and neck surgery are insufficient. This case report discusses a patient who was intraoperatively diagnosed with a right cervical vagus nerve schwannoma previously at another hospital. The patient then developed right laryngeal paralysis after the surgery without neuromonitoring. No significant recovery of the paralysis was observed, and after eight months of being referred to our institution, the patient opted for surgical retreatment following tumor growth and accompanying symptoms such as cervical swelling and discomfort. The patient was examined to evaluate the nerve damage in his previous surgery TcMEP monitoring as well as direct stimulation (DS). The right vagus nerve (RVN) showed no response on TcMEP monitoring throughout the surgery despite a significant response to DS at the tumor site. These findings suggest that the RVN had been damaged medial to the tumor site, and the damage occurred because of traction and ischemia during the previous surgery. Thus, contrary to our belief, medial nerve damage may be present even when local and peripheral nerve preservation is observed through peripheral neuromonitoring. This suggests that DS alone during neuromonitoring in head and neck surgery is insufficient. A multimodal evaluation approach, including TcMEP monitoring, is effective in not only preventing neurological complications but also in evaluating neurological deficits in all pathways from the motor cortex to the periphery.

Phosphaacene as a structural analogue of thienoacenes for organic semiconductors.

An air-stable λ3-phosphinine-containing polycyclic aromatic compound without steric protection was synthesized and its charge transport properties were evaluated, which revealed moderate hole mobility. This research is the first experimental demonstration of the organic electronic applications of low-coordinate phosphorus compounds.

Retrospective observational study of the effects of residual neuromuscular blockade and sugammadex on motor-evoked potential monitoring during spine surgery in Japan.

Given neuromuscular blockade (NMB) can affect the amplitude and detection success rate of motor-evoked potentials (MEP), sugammadex may be administered intraoperatively. We evaluated the factors affecting the degree of residual NMB (i.e., the train-of-four [TOF] ratio) and the relationship between TOF ratio and MEP detection success rate in Japanese patients undergoing spine surgery. This single-center retrospective observational study included adults who underwent spine surgery under propofol/remifentanil anesthesia, received rocuronium for intubation, and underwent myogenic MEP monitoring after transcranial stimulation. TOF ratios were assessed using electromyography. Sugammadex was administered after finishing the MEP setting and the TOF ratio was ≤0.7. To identify factors affecting the TOF ratio, TOF ratio and MEP detection success rate were simultaneously measured after finishing the MEP setting; to compare the time from intubation to the start of MEP monitoring after NMB recovery between sugammadex and spontaneous recovery groups, multivariable analyses were performed. Of 373 cases analyzed, sugammadex was administered to 221 (59.2%) cases. Age, blood pressure, hepatic impairment, and rocuronium dose were the main factors affecting the TOF ratio. Patients with higher TOF ratios (≥0.75) had higher MEP detection success rates. The time from intubation to the start of MEP monitoring after NMB recovery was significantly shorter in patients administered sugammadex versus patients without sugammadex (P < .0001). The MEP detection success rate was higher in patients with a TOF ratio of ≥0.75. Sugammadex shortened the time from intubation to the start of MEP monitoring after NMB recovery.

Transurethral electrical stimulation for intraoperative bulbocavernosus reflex monitoring during spine surgery in females.

OBJECTIVE: Intraoperative bulbocavernosus reflex (BCR) monitoring is more difficult in females than in males. This study was designed to compare the feasibility of transurethral electrical stimulation BCR (tu-BCR) monitoring with that of conventional BCR (c-BCR) monitoring during spine surgery in females. METHODS: Twenty-four females were included. For stimulation in c-BCR monitoring, a pair of surface electrodes was placed on the genitals (cathode/anode: clitoris/adjacent labium). For stimulation in tu-BCR monitoring, a urethral catheter attached to a pair of electrodes was inserted into the urethra. BCRs were recorded from the external anal sphincter after a single train of four stimulation pulses. RESULTS: There was no postoperative urinary tract injury associated with urethral catheter insertion for tu-BCR. Tu-BCR monitoring had a significantly higher success rate of baseline recording than c-BCR monitoring (87.5% vs 66.7%, respectively, p = 0.028). The specificities of tu-BCR and c-BCR monitoring were 100% and 87.2%, respectively. The sensitivity was not calculated because no patients had postoperative urinary or bowel dysfunction. CONCLUSIONS: Our data indicate that tu-BCR monitoring improved the success rate of baseline recording and specificity during spine surgery in females. SIGNIFICANCE: Tu-BCR monitoring was more reliable than c-BCR monitoring during spine surgery in females.

Exploration of Alkyl Group Effects on the Molecular Packing of 5,15-Disubstituted Tetrabenzoporphyrins toward Efficient Charge-Carrier Transport.

The high design flexibility of organic semiconductors should lead to diverse and complex electronic functions. However, currently available high-performance organic semiconductors are limited in variety; most of p-type materials are based on thienoacenes or related one-dimensionally (1D) extended π-conjugated systems. In an effort to expand the diversity of organic semiconductors, we are working on the development of tetrabenzoporphyrin (BP) derivatives as active-layer components of organic electronic devices. BP is characterized by its large, rigid two-dimensionally (2D) extended π-framework with high light absorptivity and therefore is promising as a core building unit of organic semiconductors for optoelectronic applications. Herein, we demonstrate that BP derivatives can afford field-effect hole mobilities of >4 cm2 V-1 s-1 upon careful tuning of substituents. Comparative analysis of a series of 5,15-bis(n-alkyldimethylsilylethynyl)tetrabenzoporphyrins reveals that linear alkyl substituents disrupt the π-π stacking of BP cores, unlike the widely observed "fastener effect" for 1D extended π-systems. The n-octyl and n-dodecyl groups have the best balance between high solution processability and minimal π-π stacking disruption, leading to superior hole mobilities in solution-processed thin films. The resulting thin films show high thermal stability wherein the field-effect hole mobility stays above 1 cm2 V-1 s-1 even after heating at 160 °C in air, reflecting the tight packing of large BP units. These findings will serve as a good basis for extracting the full potential of 2D extended π-frameworks and thus for increasing the structural or functional diversities of high-performance organic semiconductors.