Electrophysiological Monitoring Research Articles

Transition from predictable to variable motor cortex and striatal ensemble patterning during behavioral exploration

Animals can capitalize on invariance in the environment by learning and automating highly consistent actions; however, they must also remain flexible and adapt to environmental changes. It remains unclear how primary motor cortex (M1) can drive precise movements, yet also support behavioral exploration when faced with consistent errors. Using a reach-to-grasp task in rats, along with simultaneous electrophysiological monitoring in M1 and dorsolateral striatum (DLS), we find that behavioral exploration to overcome consistent task errors is closely associated with tandem increases in M1 and DLS neural variability; subsequently, consistent ensemble patterning returns with convergence to a new successful strategy. We also show that compared to reliably patterned intracranial microstimulation in M1, variable stimulation patterns result in significantly greater movement variability. Our results thus indicate that motor and striatal areas can flexibly transition between two modes, reliable neural pattern generation for automatic and precise movements versus variable neural patterning for behavioral exploration.

Optical electrocardiogram monitor with a real-time analysis of an abnormal heart rhythm for home-based medical alerts.

Sudden cardiac death (SCD) caused by cardiovascular disease is the greatest hidden danger to human life, accounting for about 25% of the total deaths in the world. Due to the early concealment of SCD and the heavy medical burden of long-term examination, telemedicine combined with home monitoring has become a potential medical alert method. Among all the existing human cardiac and electrophysiology monitoring methods, optics-based sensors attract the widest attention due to the advantages of low delay, real-time monitoring, and high signal-to-noise ratio. In this paper, we propose an optical sensor with the capabilities of long-term monitoring and real-time analysis. Combining an R-peak recognition algorithm, Lorenz plots (LP), and statistical analysis, we carried out the consistency analysis and result visualization of ECG sequences over 1 h. The results of 10 subjects show that the R-peak recognition accuracy of the optical ECG monitor is higher than 97.99%. The optical system can display abnormal heart rhythm in real-time through LP, and the readability is good, which makes the system suitable for self-monitoring at home. In addition, this paper provides a detailed long-term monitoring assessment method to effectively guide the practical clinical transformation of other optical wearable devices.

Soft Electrodes for Electrochemical and Electrophysiological Monitoring of Beating Cardiomyocytes

AbstractMany cells in vivo have their inherent motions, which involve numerous biochemical and biophysical signals synergistically regulating cell behavior and function. However, existing methods offer little information about the concurrently chemical and physical responses of dynamically pulsing cells. Here, we report a soft electrode with an electrospun poly(3,4‐ethylenedioxythiophene) (PEDOT)‐based nanomesh to fully comply with spontaneous motions of cells. Moreover, this electrode demonstrated excellent electrical conductivity, electrochemical performance and cellular biocompatibility. Cardiomyocytes cultured thereon exhibited autonomous and rhythmic contractility, and synchronously induced mechanical deformation of the underlying electrode, which allowed real‐time monitoring of nitric oxide release and electrophysiological activity of cardiomyocytes. This work provides a promising way toward recording chemical and electrical signals of biological systems with their natural motions.

Soft Electrodes for Electrochemical and Electrophysiological Monitoring of Beating Cardiomyocytes.

Many cells in vivo have their inherent motions, which involve numerous biochemical and biophysical signals synergistically regulating cell behavior and function. However, existing methods offer little information about the concurrently chemical and physical responses of dynamically pulsing cells. Here, we report a soft electrode with an electrospun poly(3,4-ethylenedioxythiophene) (PEDOT)-based nanomesh to fully comply with spontaneous motions of cells. Moreover, this electrode demonstrated excellent electrical conductivity, electrochemical performance and cellular biocompatibility. Cardiomyocytes cultured thereon exhibited autonomous and rhythmic contractility, and synchronously induced mechanical deformation of the underlying electrode, which allowed real-time monitoring of nitric oxide release and electrophysiological activity of cardiomyocytes. This work provides a promising way toward recording chemical and electrical signals of biological systems with their natural motions.

The Frontier of Electrophysiologic Monitoring in Acute Brain Injury.

The Frontier of Electrophysiologic Monitoring in Acute Brain Injury.

Dorsal Anterior Cingulum Bundle Stimulation: Modulation of Affect, Anxiety, and Pain

The anterior cingulate cortex has been ascribed putative roles in varied emotional and cognitive functions. To evaluate the cingulum bundle as a therapeutic target for anxiety and mood disorders, we investigated responses evoked by the application of direct electrical stimulation to the anterior cingulum bundle in 17 patients undergoing intracranial electrophysiological monitoring.

Microelectrode array membranes to simultaneously assess cardiac and neurological signals of xenopus laevis under chemical exposures and environmental changes

Simultaneous monitoring of electrocardiogram (ECG) and electroencephalogram (EEG) in studied animal models requires innovative engineering techniques that can capture minute physiological changes. However, this is often administered with a bulky and/or invasive system that may cause discomfort to animals and signal distortions. Here, we develop an integrated bioelectronic sensing system to provide simultaneous recordings of ECG and EEG in real-time for Xenopus laevis. The microelectrode array (MEA) membrane and the distinct anatomy of Xenopus offer noninvasive multi-modal electrophysiological monitoring with favorable spatial resolution. The system was validated under different environmental conditions, including drug exposure and temperature changes. Under the exposure of Pentylenetetrazol (PTZ), an epilepsy-inducing drug, clear ECG and EEG alterations, including frequent ictal and interictal EEG events, 30 dB average EEG amplitude elevations, abnormal ECG morphology, and heart rate changes, were observed. Furthermore, the ECG and EEG were monitored and analyzed under different temperatures. A decrease in relative power of delta band was observed when cold environment was brought about, in contrast to an increase in relative power of other higher frequency bands while the ECG remained stable. Overall, the real-time electrophysiology monitoring system using the Xenopus model holds potential for many applications in drug screening and remote environmental monitoring.

Anatomy and motor function of extra-laryngeal branching patterns of the recurrent laryngeal nerve; an electrophysiological study of 1001 nerves at risk

Introduction Safe thyroid surgery depends on a deep knowledge of human neck anatomy, including the recurrent laryngeal nerve (RLN). Anatomic variations such as extra-laryngeal terminal branching (ETB) are common. Patients and methods We studied the ETB pattern of 1001 RLNs at risk in 596 patients. We identified and exposed the location of division points on the cervical part of bifid RLN. The function of nerve branches was assessed through intraoperative nerve monitoring (IONM). Results Bifid RLNs was identified in 39.6% of patients. The nerve-based prevalence of ETB was 28.5%. The prevalence of ETB for the right and left RLN was 21.8% and 35.5%, respectively (p < 0.001). The location of the division point was found in the middle, distal, and proximal segments in 48.8%, 33.3%, and 18% of bifid RLNs, respectively. Electrophysiological monitoring revealed motor functions in all anterior and in 7% of posterior branches. The rate of injury was 0.4%, and 1.1% in single trunk and bifid nerves, respectively (p = 0.360), and 3.9% in nerves with proximal branching (p = 0.084). Conclusions The ETB prevalence is high and showing division points in different cervical segments of the RLN. All anterior branches and some posterior branches contain motor fibers. Knowledge and awareness of these anatomic and functional variations are mandatory for every thyroid surgeon to avoid misidentification and misinterpretation of human RLN anatomy.

Applications of Organic Electrochemical Transistors in Flexible Bioelectronics

Flexible bioelectronics, offering soft functionalized interfaces to couple biology and electronics, have gained increasing interest due to its great promise in personalized health monitoring, point-of-care diagnosis, and the Internet of Things (IoT). Organic electrochemical transistors (OECTs), capable of mixed ionic-electronic transport, have been widely implemented in flexible bioelectronics due to their flexibility, biocompatibility, high transconductance, low working voltage, design diversity, and facile manufacturing. In this review, we focus on the representative bioelectronic applications of flexible OECTs. We first introduce the device physics of OECTs, with a highlight on their identifying features compared to conventional field-effect transistors. Then, the state-of-the-art channel materials used in OECTs are summarized, with discussions on their figures of merit. Followed by an introduction to the main techniques employed for fabricating flexible OECTs, we examine the up-to-date progress in flexible OECTs for bioelectronic applications, including diverse biosensors, electrophysiological monitoring, and neuromorphic devices. Accompanied by a concise summary, the challenges and opportunities in the commercialization of flexible OECTs are discussed.

244 A Systematic Review of Epileptiform Changes During Sevoflurane Anesthesia In Infants and Children

OBJECTIVES/GOALS: Early clinical case reports have described incidental epileptiform changes during electrophysiological monitoring. The objective of this study was to perform a systematic review of all existing investigations of epileptiform activity during sevoflurane use in pediatric anesthesia. The heterogenous EEG data will be analyzed in a meta analysis METHODS/STUDY POPULATION: A targeted, PICO-based clinical question was crafted and registered a priori on PROSPERO on 3/19/21. Under the guidance of a librarian from the Albert Einstein College of Medicine, a boolean search string was generated to search articles and gray literature for terms such as pediatric, sevoflurane and electroencephalogram in PubMed, OVID, Cochrane, Google Scholar, etc. We utilized the software platform tool COVIDENCE to manage our review. 495 references were imported for initial screening. 56 English-language, full-text studies were included for further review. The final 13 references were included in data extraction and Newcastle-Ottawa bias assessment. The characteristics of the studies and their primary outcomes were collected in tabular form. Strategies for data synthesis were discussed weekly. RESULTS/ANTICIPATED RESULTS: Epileptiform changes reported in the literature during pediatric sevoflurane anesthesia ranged from 0 - 95%. EEG data were acquired using a variety of recording systems with variable number of leads and heterogeneous outcomes reported. The periods of anesthesia monitoring were also heterogeneous. Characteristics of the studies are presented in Table 1. 495 references were imported for screening with 13 final references for data extraction. EEG abnormalities were reported in 204/649 (31.4%) subjects ranging in age from neonate to 18 years; the majority of studies utilized less than 16 channels of (10/13, 76.9%) (Table 1). There was variability in sevoflurane dosing, premedication (e.g., midzolam, hydroxyzine), and periods of anesthesia monitored. DISCUSSION/SIGNIFICANCE: There was heterogeneity noted across reviewed literature including study design, phases of anesthesia, ventilation methods, number of EEG leads recorded and adjuvant anesthetics administered. Nevertheless, this review rigorously classified epileptiform activity during Sevoflurane thereby influencing modern anesthesia.

Intramedullary Spinal Cord Lesions: A Single-Center Experience.

ObjectiveSpinal cord tumors constitute a small part of spinal surgery owing to their rarity. This retrospective study describes their current management. MethodsForty-eight patients were treated for an intramedullary tumor between 2014 and 2020 at a single institution. Patients’ files were retrospectively studied. We detailed clinical status according to neurological deficit and ambulatory ability using the modified McCormick Scale, radiological features like number of levels, associated syringomyelia, surgical technique with or without intraoperative electrophysiological monitoring, pathological findings, and postoperative outcome. ResultsThe median age of this population was 43 years, including 5 patients under 18 years. The median delay before first neurosurgical contact was 3 months after the first clinical complaint. Treatment was gross total resection in 43.8%, subtotal resection in 50.0%, and biopsy in 6.2%. A laminectomy was performed for all the patients except 2 operated using the laminoplasty technique. Pathological findings were ependymoma in 43.8%, hemangioblastoma in 20.8%, and pilocytic astrocytoma in 10.4%. Six patients were reoperated for a tumor recurrence less than 2 years after the first surgical resection. One patient was reoperated for a postoperative cervical kyphosis. ConclusionIntramedullary tumors are still a challenging disease and they are treated by various surgical techniques. They must be managed in a specialized center including a trained surgical, radiological, electrophysiological, and pathological team. Arthrodesis must be discussed before performing extensive laminectomy to avoid postoperative kyphosis.

A Self-Supporting, Conductor-Exposing, Stretchable, Ultrathin, and Recyclable Kirigami-Structured Liquid Metal Paper for Multifunctional E-Skin.

Electronic skin (E-skin) is a crucial seamless human-machine interface (HMI), holding promise in healthcare monitoring and personal electronics. Liquid metal (LM) has been recognized as an ideal electrode material to fabricate E-skins. However, conventional sealed LM electrodes cannot expose the LM layer for direct contact with the skin resulting in the low performance of electrophysiological monitoring. Furthermore, traditional printed LM electrodes are difficult to transfer or recycle, and fractures easily occur under stretching of the substrate. Here, we report a kind of LM electrode that we call a kirigami-structured LM paper (KLP), which is self-supporting, conductor-exposing, stretchable, ultrathin, and recyclable for multifunctional E-skin. The KLP is fabricated by the kirigami paper cutting art with three types of structures including uniaxial, biaxial, and square spiral. The KLP can act as an E-skin to acquire high-quality electrophysiological signals, such as electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG). Upon integration with a triboelectric nanogenerator (TENG), the KLP can also operate as a self-powered E-skin. On the basis of the self-powered E-skin, we further developed a smart dialing communication system, which is applied on human skin to call a cellphone. Compared with conventional sealed or printed LM electrodes, the KLP can simultaneously achieve self-supporting, conductor-exposing, stretchable, ultrathin, and recyclable features. Such KLP offers potential for E-skins in healthcare monitoring and intelligent control, as well as smart robots, virtual reality, on-skin personal electronics, etc.

Recovery of consolidation after sleep following stroke-interaction of slow waves, spindles, and GABA.

Sleep is known to promote recovery after stroke. Yet it remains unclear how stroke affects neural processing during sleep. Using an experimental stroke model in rats along with electrophysiological monitoring of neural firing and sleep microarchitecture, here we show that sleep processing is altered by stroke. We find that the precise coupling of spindles to global slow oscillations (SOs), a phenomenon that is known to be important for memory consolidation, is disrupted by a pathological increase in "isolated" local delta waves. The transition from this pathological to a physiological state-with increased spindle coupling to SO-is associated with sustained performance gains during recovery. Interestingly, post-injury sleep could be pushed toward a physiological state via a pharmacological reduction of tonic γ-aminobutyric acid (GABA). Together, our results suggest that sleep processing after stroke is impaired due to an increase in delta waves and that its restoration can be important for recovery.

421 Coherence Between the Subthalamic Nucleus and the Primary Motor Cortex in Patients With Parkinson's Disease

INTRODUCTION: DBS is established as a safe and effective treatment for Parkinson’s Disease (PD). The development of second generation stimulators based on closed loop systems is dependent upon deeper understanding of the cortical control of motricity and its coupling with STN oscillations. METHODS: Experimental study on human subjects involving 10 patients with idiopathic PD with indication for deep brain stimulation implants into the STN. Primary motor area of the hands were identified preoperatively with fMRI. Corkscrew electrodes were implanted in the scalp to obtain C3-Cz and C4-Cz derivations of the EEG. Needle electrodes were implanted into the thenar and hypothenar muscles of both hands to record motor evoked potentials and voluntary myoelectric activity. At the time of implantation of the definitive macro-electrodes, the best contacts were connected to the electrophysiological monitoring device to record STN local field potentials (LFP) from 1 side at a time. During the next 3 minutes, the patient was asked to perform closing and opening movements of the hand contralateral to the implant. Simultaneously recordings of hand-EMG, EEG signals from M1, and STN field potentials were acquired for off line analysis. RESULTS: Our data indicate that during epochs of hand movements, theta and beta range components of the EEG related to M1 were significantly increased as compared with rest epochs. Additionally, we demonstrated that, during movement, the cross correlation between STN-LFP and M1 significantly increased (p &lt; 0.001). CONCLUSION: Movement control is highly dependent upon theta and beta EEG components and upon a high coherence between STN and M1 specifically occurring during movement. The development of closed-loop stimulation devices should consider this physiology to reach better results.

Do evoked potentials matter? Pre-pathologic signal change and clinical outcomes with expandable cages in lateral lumbar interbody fusion surgery

Minimally Invasive Lateral Lumbar Interbody Fusion (MIS LLIF) is a reliable technique for treatment of degenerative disk disease, foraminal stenosis and spinal deformity. The retroperitoneal transpsoas approach risks lumbar plexus injury that may result in anterior thigh pain, sensory loss and weakness. A prospective study of 64 consecutive patients undergoing MIS LLIF with expandable cages (23 standalone, 41 integrated with lateral plate) using multimodal electrophysiological monitoring was performed. We measured sequential retraction times, complications, patient reported outcome scores and electrophysiologic findings with a minimum 12-month follow-up. Incidence of evoked potential and electromyographic signal change was moderate, and rarely resulted in post-operative neurologic deficit. Evoked potential signal changes were frequently resolved by the un-breaking of the surgical table or repositioning of the retractor. Average retraction times were 24 (15–41) minutes for standalone cages and 30 (15–41) minutes for integrated cages. At follow-up, the vast majority (97%) of patients reported significant clinical improvement post-operatively with only 2 patients reporting postoperative neurologic symptoms and subsequent recovery at 12-months. The present study shows that evoked potentials combined with electromyography is a more sensitive measure of pre-pathologic lumbar plexopathy in LLIF compared to electromyography alone, especially at L3/4 and L4/5 levels. Based on our findings, there is limited clinical indication for routine neural monitoring at rostral lumbar levels. The routine inclusion of multimodal electrophysiological monitoring in lateral transpsoas surgery is recommended to minimise the risk of neural injury by enabling optimal patient and retractor positioning and continued surveillance throughout the procedure.

Drawn-on-Skin Sensors from Fully Biocompatible Inks toward High-Quality Electrophysiology.

The need to develop wearable devices for personal health monitoring, diagnostics, and therapy has inspired the production of innovative on-demand, customizable technologies. Several of these technologies enable printing of raw electronic materials directly onto biological organs and tissues. However, few of them have been thoroughly investigated for biocompatibility of the raw materials on the cellular, tissue, and organ levels or with different cell types. In addition, highly accurate multiday in vivo monitoring using such on-demand, in situ fabricated devices has yet to be done. Presented herein is the first fully biocompatible, on-skin fabricated electronics for multiple cell types and tissues that can capture electrophysiological signals with high fidelity. While also demonstrating improved mechanical and electrical properties, the drawn-on-skin ink retains its properties under various writing conditions, which minimizes the variation in electrical performance. Furthermore, the drawn-on-skin ink shows excellent biocompatibility with cardiomyocytes, neurons, mice skin tissue, and human skin. The high signal-to-noise ratios of the electrophysiological signals recorded with the DoS sensor over multiple days demonstrate its potential for personalized, long-term, and accurate electrophysiological health monitoring.

Reconstruction clipping of ruptured anterior circulation aneurysms via supraorbital lateral keyhole approach

BackgroundIntracranial aneurysm (IA) is a serious disease. Analyze and review the cases of anterior circulation ruptured IA by supraorbital lateral keyhole approach, and summarize the experiences of this approach.MethodsRetrospective analysis of 16 cases of ruptured anterior circulation IA in our department from January 2019 to June 2020, CT angiography (CTA) was performed before operation. Analyzing the IA’s parameters by 3D-CT reconstruction. The IA was clipped by supraorbital lateral keyhole approach combined with the 3D-skull reconstruction. Extraventricular drainage was performed before craniotomy. Intraoperative neurophysiological monitoring was performed during the operation. After operation, fluorescein angiography and vascular ultrasound were performed to check the clipping effect. Intracranial pressure monitor was performed postoperatively. CTA was reexamined one week after operation. The modified Rankin Scale (MRS) was performed 6 months after operation.ResultsThere were 7 males (43.8%) and 9 females (56.2%), and the average age is 52.31 ± 11.12 years old. Among them, 11 patients (68.8%) were anterior communicating artery aneurysms and 5 (31.2%) were middle cerebral artery aneurysms. All patients were out of hospital within 10 days without any death, without cerebral infarction, cerebrospinal fluid leakage and neurological impairments. About mRS score, after 6 months follow-up, 8 cases (50%) had 0 point, 4 cases (25%) had 1 point, and 4 cases (25%) had 2 points.ConclusionsFor ruptured anterior circulation IA, the supraorbital lateral keyhole approach combined with ventricular drainage, intraoperative electrophysiological monitoring, and intraoperative vascular ultrasound is a safe and minimally invasive treatment. The application of reconstruction clipping can reconstruct the diameter of parent vessel and reduce the recurrence rate of IA.

3D‐Knit Dry Electrodes using Conductive Elastomeric Fibers for Long‐Term Continuous Electrophysiological Monitoring

AbstractRecent advances in telemedicine and personalized healthcare have motivated new developments in wearable technologies targeting continuous monitoring of biosignals. Common limitations of wearables for continuous monitoring include durability and breathability of their biopotential electrodes. This paper tackles this challenge by proposing flexible, breathable, and washable dry textile electrodes made of conductive elastomeric filaments (CEFs). First, candidate CEF fibers are characterized. Using an industrial knitting machine, CEF fibers are then directly knitted into textile electrodes. To assess their performance in more realistic circumstances, smart garments with textile electrodes are knitted. Electrocardiograms (ECGs) are acquired using an underwear garment and electrooculograms (EOGs) are acquired using a headband. ECGs and EOGs with textile electrodes are found to have comparable fidelity to that of the gold standard gel electrodes. CEF electrodes are also resistant to repeated wash and dry cycles (30×) and continue to acquire high‐fidelity biosignals. Smart underwear garments are also used to perform continuous ECG measurements in five participants over 24 h of unrestricted daily activities. Results demonstrate the success of these garments in performing high fidelity continuous ECG monitoring. Collectively, these results present CEF electrodes as a promising scalable solution to the challenges of wearable technologies for long‐term continuous electrophysiological monitoring applications.

Effects of Lidocaine on Motor-Evoked Potentials and Somatosensory-Evoked Potentials in Patients Undergoing Intraspinal Tumour Resection: Study Protocol for a Prospective Randomized Controlled Trial.

PurposeAt present, it is believed that intravenous (IV) infusion of lidocaine can inhibit hyperalgesia, relieve postoperative acute and chronic pain, and accelerate the rehabilitation of patients. However, studies of its effects on necessary electrophysiological monitoring during neurosurgery are few, and the results are controversial. This study assumes that the propofol-remifentanil based anaesthesia combined with lidocaine in patients undergoing intraspinal tumour resection will not have adverse effects on motor-evoked potentials (MEPs) or somatosensory-evoked potentials (SEPs).Study Design and MethodsThis is a prospective, randomized, placebo-controlled double-blind trial. A total of 96 patients undergoing intraspinal tumour resection will be randomly allocated to lidocaine and placebo group. The lidocaine group will receive IV lidocaine during anaesthesia, while the placebo group will receive the same dose of normal saline with the same infusion rate and infusion time, and the anaesthesia procedures of the two groups will be the same. All patients will be monitored the MEPs and SEPs of all four limbs during operation. The primary outcome will be the MEP amplitudes of both upper limbs at the end of operation. The secondary outcome measures will be the other electrophysiological parameters at the end of operation, the incidence of alert events for all four limbs, and the incidence of false positive events.DiscussionThe purpose of this study is to evaluate the effects of IV infusion of lidocaine on SEPs and MEPs during intraspinal tumour resection to determine whether electrophysiological monitoring can accurately reflect the integrity of nerve functions while infusing lidocaine and to explore the possibility of lidocaine use during intraspinal tumour resection as an anaesthesia option.

Deep Brain Stimulation Reduces Conflict-Related Theta and Error-Related Negativity in Patients With Obsessive–Compulsive Disorder

ObjectivesObsessive–compulsive disorder (OCD) is a psychiatric disorder with alterations of cortico-striato-thalamo-cortical loops and impaired performance monitoring. Electrophysiological markers such as conflict-related medial frontal theta (MFT) and error-related negativity (ERN) may be altered by clinically effective deep brain stimulation (DBS) of the anterior limb of the internal capsule and nucleus accumbens (ALIC/NAc). We hypothesized that ALIC/NAc DBS modulates electrophysiological performance monitoring markers. Materials and MethodsFifteen patients (six male) with otherwise treatment-refractory OCD receiving ALIC/NAc DBS performed a flanker task with EEG recordings at three sessions: presurgery and at follow-up with DBS on and off. We examined MFT, ERN, and task performance. Furthermore, we investigated interrelations with clinical efficacy and then explored the influence of the location of individual stimulation volumes on EEG modulations. ResultsMFT and ERN were significantly attenuated by DBS with differences most pronounced between presurgery and DBS-on states. Also, we observed reaction time slowing for erroneous responses during DBS-off. Larger presurgery ERN amplitudes were associated with decreased clinical efficacy. Exploratory anatomical analyses suggested that stimulation volumes encompassing the NAc were associated with MFT modulation, whereas ALIC stimulation was associated with modulation of the ERN and clinical efficacy. ConclusionALIC/NAc DBS diminished MFT and ERN, demonstrating modulation of the medial frontal performance monitoring system in OCD. Furthermore, our findings encourage further studies to explore the ERN as a potential predictor for clinical efficacy.