Influence of Anesthesia and Clinical Variables on the Firing Rate, Coefficient of Variation and Multi-Unit Activity of the Subthalamic Nucleus in Patients with Parkinson's Disease

BACKGROUND: Microelectrode recordings (MER) are used to optimize lead placement during subthalamic nucleus deep brain stimulation (STN-DBS). To obtain reliable MER, surgery is usually performed while patients are awake. Procedural sedation and analgesia (PSA) is often desirable to improve patient comfort, anxiolysis and pain relief. The effect of these agents on MER are largely unknown. The objective of this study was to determine the effects of commonly used PSA agents, dexmedetomidine, clonidine and remifentanil and patient characteristics on MER during DBS surgery. METHODS: Data from 78 patients with Parkinson's disease (PD) who underwent STN-DBS surgery were retrospectively reviewed. The procedures were performed under local anesthesia or under PSA with dexmedetomidine, clonidine or remifentanil. In total, 4082 sites with multi-unit activity (MUA) and 588 with single units were acquired. Single unit firing rates and coefficient of variation (CV), and MUA total power were compared between patient groups. RESULTS: We observed a significant reduction in MUA, an increase of the CV and a trend for reduced firing rate by dexmedetomidine. The effect of dexmedetomidine was dose-dependent for all measures. Remifentanil had no effect on the firing rate but was associated with a significant increase in CV and a decrease in MUA. Clonidine showed no significant effect on firing rate, CV or MUA. In addition to anesthetic effects, MUA and CV were also influenced by patient-dependent variables. CONCLUSION: Our results showed that PSA influenced neuronal properties in the STN and the dexmedetomidine (DEX) effect was dose-dependent. In addition, patient-dependent characteristics also influenced MER

Combining gamma with Alpha and Beta power modulation for enhanced cortical mapping in patients with focal epilepsy

About one third of patients with epilepsy have seizures refractory to the medical treatment. Electrical stimulation mapping (ESM) is the gold standard for the identification of "eloquent" areas prior to resection of epileptogenic tissue. However, it is time-consuming and may cause undesired side effects. Broadband gamma activity (55-200 Hz) recorded with extraoperative electrocorticography (ECoG) during cognitive tasks may be an alternative to ESM but until now has not proven of definitive clinical value. Considering their role in cognition, the alpha (8-12 Hz) and beta (15-25 Hz) bands could further improve the identification of eloquent cortex. We compared gamma, alpha and beta activity, and their combinations for the identification of eloquent cortical areas defined by ESM. Ten patients with intractable focal epilepsy (age: 35.9 ± 9.1 years, range: 22-48, 8 females, 9 right handed) participated in a delayed-match-to-sample task, where syllable sounds were compared to visually presented letters. We used a generalized linear model (GLM) approach to find the optimal weighting of each band for predicting ESM-defined categories and estimated the diagnostic ability by calculating the area under the receiver operating characteristic (ROC) curve. Gamma activity increased more in eloquent than in non-eloquent areas, whereas alpha and beta power decreased more in eloquent areas. Diagnostic ability of each band was close to 0.7 for all bands but depended on multiple factors including the time period of the cognitive task, the location of the electrodes and the patient's degree of attention to the stimulus. We show that diagnostic ability can be increased by 3-5% by combining gamma and alpha and by 7.5-11% when gamma and beta were combined. We then show how ECoG power modulation from cognitive testing can be used to map the probability of eloquence in individual patients and how this probability map can be used in clinical settings to optimize ESM planning. We conclude that the combination of gamma and beta power modulation during cognitive testing can contribute to the identification of eloquent areas prior to ESM in patients with refractory focal epilepsy.info:eu-repo/semantics/publishedVersio

Preterm Perinatal Hypoxia-Ischemia Does not Affect Somatosensory Evoked Potentials in Adult Rats

Somatosensory evoked potentials (SSEPs) are a valuable tool to assess functional integrity of the somatosensory pathways and for the prediction of sensorimotor outcome in perinatal injuries, such as perinatal hypoxia-ischemia (HI). In the present research, we studied the translational potential of SSEPs together with sensory function in the male adult rat with perinatal HI compared to the male healthy adult rat. Both somatosensory response and evoked potential were measured at 10-11 months after global perinatal HI. Clear evoked potentials were obtained, but there were no group differences in the amplitude or latency of the evoked potentials of the preceding sensory response. The bilateral tactile stimulation test was also normal in both groups. This lack of effect may be ascribed to the late age-of-testing and functional recovery of the rats

Effect of sevoflurane on neuronal activity during deep brain stimulation surgery for epilepsy: A case report

Deep brain stimulation of the anterior nucleus of the thalamus is an effective treatment for patients with refractory epilepsy who do not respond sufficiently to medical therapy. Optimal therapeutic effects of deep brain stimulation probably depend on accurate positioning of the stimulating electrodes. Microelectrode recordings show bursty firing neurons in the anterior nucleus of the thalamus region, which confirms the anatomical target determined by the surgeon. Deep brain stimulation electrodes in epilepsy patients are implanted under general anesthesia. The type and depth of anesthesia might interfere with microelectrode ecordings. Here, we describe our experience of a patient who underwent deep brain stimulation surgery under general anesthesia with sevoflurane, a volatile anesthetic, and its effect on the microelectrode recordings. Keywords: Thalamus, Deep brain stimulation, Sevofluran

Thalamocortical coherence and causality in different sleep stages using deep brain stimulation recordings

Previous research has shown an interplay between the thalamus and cerebral cortex during NREM sleep in humans, however the directionality of the thalamocortical synchronization is as yet unknown. In this study thalamocortical connectivity during different NREM sleep stages using sleep scalp electroencephalograms and local field potentials from the left and right anterior thalamus was measured in three epilepsy patients implanted with deep brain stimulation electrodes. Connectivity was assessed as debiased weighted phase lag index and granger causality between the thalamus and cortex for the NREM sleep stages N1, N2 and N3. Results showed connectivity was most prominently directed from cortex to thalamus. Moreover, connectivity varied in strength between the different sleep stages, but barely in direction or frequency. These results imply relatively stable thalamocortical connectivity during NREM sleep directed from the cortex to the thalamus

Neonatal loss of motor function in human spina bifida aperta

OBJECTIVE: In neonates with spina bifida aperta (SBA), leg movements innervated by spinal segments located caudal to the meningomyelocele are transiently present. This study in neonates with SBA aimed to determine whether the presence of leg movements indicates functional integrity of neuronal innervation and whether these leg movements disappear as a result of dysfunction of upper motor neurons (axons originating cranial to the meningomyelocele) and/or of lower motor neurons (located caudal to the meningomyelocele). METHODS: Leg movements were investigated in neonates with SBA at postnatal day 1 (n = 18) and day 7 (n = 10). Upper and lower motor neuron dysfunction was assessed by neurologic examination (n = 18; disinhibition or inhibition of reflexes, respectively) and by electromyography (n = 12; absence or presence of denervation potentials, respectively). RESULTS: Movements, related to spinal segments caudal to the meningomyelocele, were present in all neonates at postnatal day 1. At day 1, leg movements were associated with signs of both upper (10 of 18) and lower (17 of 18) motor neuron dysfunction caudal to the meningomyelocele. In 7 of 10 neonates restudied after the first postnatal week, leg movements had disappeared. The absence of leg movements coincided with loss of relevant reflexes, which had been present at day 1, indicating progression of lower motor neuron dysfunction. CONCLUSIONS: We conclude that the presence of neonatal leg movements does not indicate integrity of functional lower motor neuron innervation by spinal segments caudal to the meningomyelocele. Present observations could explain why fetal surgery at the level of the meningomyelocele does not prevent loss of leg movements