This letter discusses the recent study by Izzo et al., which explored intraoperative microelectrode recording (MER) during asleep deep brain stimulation (DBS) of the subthalamic nucleus for Parkinson\'s disease. The study\'s integration of a systematic review positions its findings within the broader context of neurosurgical advances. Highlighting the practicality and patient comfort of the frameless technique under general anesthesia, it emphasizes the significance of MER in optimizing electrode placement, thereby potentially enhancing patient outcomes. The letter suggests future research directions, including randomized clinical trials, to assess the clinical benefits of this methodology further.

The use of microelectrode recording (MER) during deep brain stimulation (DBS) for Parkinson Disease is controversial. Furthermore, in asleep DBS anesthesia can impair the ability to record single-cell electric activity.The purpose of this study was to describe our surgical and anesthesiologic protocol for MER assessment during asleep subthalamic nucleus (STN) DBS and to put our findings in the context of a systematic review of the literature. Sixty-three STN electrodes were implanted in 32 patients under general anesthesia. A frameless technique using O-Arm scanning was adopted in all cases. Total intravenous anesthesia, monitored with bispectral index, was administered using a target controlled infusion of both propofol and remifentanil. A systematic review of the literature with metanalysis on MER in asleep vs awake STN DBS for Parkinson Disease was performed. In our series, MER could be reliably recorded in all cases, impacting profoundly on electrode positioning: the final position was located within 2 mm from the planned target only in 42.9% cases. Depth modification > 2 mm was necessary in 21 cases (33.3%), while in 15 cases (23.8%) a different track was used. At 1-year follow-up we observed a significant reduction in LEDD, UPDRS Part III score off-medications, and UPDRS Part III score on medications, as compared to baseline. The systematic review of the literature yielded 23 papers; adding the cases here reported, overall 1258 asleep DBS cases using MER are described. This technique was safe and effective: metanalysis showed similar, if not better, outcome of asleep vs awake patients operated using MER. MER are a useful and reliable tool during asleep STN DBS, leading to a fine tuning of electrode position in the majority of cases. Collaboration between neurosurgeon, neurophysiologist and neuroanesthesiologist is crucial, since slight modifications of sedation level can impact profoundly on MER reliability.

Premature ventricular contraction (PVC) is usually eliminated in the earliest activation site based on the conventional electrode of ablation catheter. However, the large size electrode may contain far-field potential. The QDOT MICRO ablation catheter has three micro electrodes with 0.33 mm electrode length, in addition to the conventional electrode with 3.5 mm electrode length. The micro electrodes can reflect only near-field potential. A 78-year-old with symptomatic frequent PVCs underwent catheter ablation. PVC-1 showed good pace-mapping in distal great cardiac vein (GCV). The local bipolar electrograms in the conventional electrode of ablation catheter preceded the PVC-QRS onset by 32 ms in distal GCV and 13 ms in left coronary cusp (LCC), but those in the micro electrodes preceded only by 13 ms both in distal GCV and LCC. PVC-1 was eliminated by radiofrequency (RF) application, not in distal GCV, but in LCC. PVC-2 showed good pace-mapping in LCC. The local bipolar electrograms in both the conventional electrode and the micro electrodes of ablation catheter preceded the PVC-QRS onset by 32 ms in LCC. PVC-2 was eliminated by RF application in LCC. Comparing the local electrograms of micro electrodes and the conventional electrodes may be important for identifying depth of the origin of PVCs.

There are many electrode types for recording and stimulating neural tissue, most of which necessitate direct contact with the target tissue. These electrodes range from large, scalp electrodes which are used to non-invasively record averaged, low frequency electrical signals from large areas/volumes of the brain, to penetrating microelectrodes which are implanted directly into neural tissue and interface with one or a few neurons. With the exception of scalp electrodes (which provide very low-resolution recordings), each of these electrodes requires a highly invasive, open brain surgical procedure for implantation, which is accompanied by significant risk to the patient. To mitigate this risk, a minimally invasive endovascular approach can be used. Several types of endovascular electrodes have been developed to be delivered into the blood vessels in the brain via a standard catheterization procedure. In this review, the existing body of research on the development and application of endovascular electrodes is presented. The capabilities of each of these endovascular electrodes is compared to commonly used direct-contact electrodes to demonstrate the relative efficacy of the devices. Potential clinical applications of endovascular recording and stimulation and the advantages of endovascular versus direct-contact approaches are presented.

The Lance-Adams syndrome (LAS) is a myoclonus syndrome caused by hypoxic-ischemic encephalopathy. LAS cases could be refractory to first-line medications, and the neuronal mechanism underlying LAS pathology remains unknown.
To describe a patient with LAS who underwent bilateral globus pallidus internus (GPi) stimulation and discuss the pathophysiology of LAS with intraoperative electrophysiological findings.
A 79-year-old woman presented with a history of cardiopulmonary arrest due to internal carotid artery rupture following carotid endarterectomy after successful cardiopulmonary resuscitation. However, within 1 month, the patient developed sensory stimulation-induced myoclonus in her face and extremities. Because her myoclonic symptoms were refractory to pharmacotherapy, deep brain stimulation of the GPi was performed 1 year after the hypoxic attack.
Continuous bilateral GPi stimulation with optimal parameter settings remarkably improved the patient\'s myoclonic symptoms. At the 2-year follow-up, her Unified Myoclonus Rating Scale score decreased from 90 to 24. In addition, we observed burst firing and interburst pause patterns on intraoperative microelectrode recordings of the bilateral GPi and stimulated this area as the therapeutic target.
Our results show that impairment in the basal ganglion circuitry might be involved in the pathogenesis of myoclonus in patients with LAS.

In this paper, we present a non-fluidic microsystem for the simultaneous visualization and electrochemical evaluation of confined, growing bacteria on solid media. Using a completely automated platform, real-time monitoring of bacterial and image-based computer characterization of growth were performed. Electrochemical tests, using Escherichia coli K-12 as the model microorganism, revealed the development of a faradaic process at the bacteria-microelectrode interface inside the microsystem, as implied by cyclic voltammetry and electrochemical impedance spectrometry measurements. The electrochemical information was used to determine the moment in which bacteria colonized the electrode-enabled area of the microsystem. This microsystem shows potential advantages for long-term electrochemical monitoring of the extracellular environment of cell culture and has been designed using readily available technologies that can be easily integrated in routine protocols. Complementarily, these methods can help elucidate fundamental questions of the electron transfer of bacterial cultures and are potentially feasible to be integrated into current characterization techniques.

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Hemophilia B is an X linked recessive deficiency of factor IX that presents with a range of clinical severity that co-relates with factor levels. Although guidelines exist to guide perioperative hemostasis in such patients, there is scarce data on elective high-risk neurosurgeries, resulting in a reluctance to offer these patients elective neurosurgeries. These patients thus rarely if ever undergo such procedures. We report a unique case of undiagnosed mild hemophilia B in a gentleman that was found incidentally at age 64 during pre-operative workup. This gentleman had intractable Parkinson\'s disease for which subthalmic deep brain stimulation was indicated. He was found to have a prolonged APTT on initial lab testing. After subsequent workup, and having excluded the presence of inhibitors, he was diagnosed with Hemophilia B. With the use of Factor IX concentrates (AlphaNine®) and close clinical, laboratory, and radiological monitoring a plan was made for this patient to undergo this procedure. Our patient successfully underwent subthalmic deep brain stimulation with microelectrode recordings and intraoperative test stimulation in a two-step procedure, followed by single channel implantable neurostimulator and extension wire implantations 2 weeks later. The successful peri-operative course of this patient using this novel approach is described, and the need for future data in this regard is emphasized.

The amputation of an extremity is commonly followed by phantom sensations that are perceived to originate from the missing limb. The mechanism underlying the generation of these sensations is still not clear although the development of abnormal oscillatory bursting in thalamic neurons may be involved. The theory of thalamocortical dysrhythmia implicates gamma oscillations in phantom pathophysiology although this rhythm has not been previously observed in the phantom limb thalamus. In this study, the authors report the novel observation of widespread 38-Hz gamma oscillatory activity in spike and local field potential recordings obtained from the ventral caudal somatosensory nucleus of the thalamus (Vc) of a phantom limb patient undergoing deep brain stimulation (DBS) surgery. Interestingly, microstimulation near tonically firing cells in the Vc resulted in high-frequency, gamma oscillatory discharges coincident with phantom sensations reported by the patient. Recordings from the somatosensory thalamus of comparator groups (essential tremor and pain) did not reveal the presence of gamma oscillatory activity.

OBJECTIVE: As technology continues to advance for our aging population, an increasing number of deep brain stimulation (DBS) candidates will have preexisting implanted electrical devices. In this article, we discuss safe and successful DBS in a patient with Parkinson\'s disease (PD) and bilateral cochlear implants.
METHODS: A 70-year-old male with PD and bilateral cochlear implants underwent successful microelectrode-guided DBS implantation into bilateral subthalamic nuclei (STN). The patient\'s cochlear implant magnets were removed and replaced in the outpatient clinic for preoperative MRI and stereotactic targeting. The cochlear implants were turned off intraoperatively for STN microelectrode recordings.
RESULTS: Precise, MRI-guided stereotactic DBS implantation was possible. Intraoperative high-fidelity microelectrode recordings confirmed STN neurons with the cochlear implants turned off. These recordings were not possible with active cochlear implant devices. Our literature review describes the other approaches/techniques that have been used to manage DBS surgery in the setting of cochlear implants.
CONCLUSIONS: Despite the risk of electrical interference between implanted medical devices, DBS and cochlear implants may be safe and compatible in the same patient if necessary precautions are taken.