Sensorimotor interaction between somatosensory painful stimuli and motor sequences affects both anticipatory alpha rhythms and behavior as a function of the event side

It has been shown that concomitant painful stimulation and simple movement at the same hand is related to decreased anticipatory alpha event-related desynchronization (ERD) and reduced pain intensity, possibly due to the interference between somatosensory and motor information processing (Babiloni et al. [6]). Here, we tested the hypothesis that such interference also affects motor performance during sequential movements. Visual warning stimuli were followed by imperative stimuli associated to electrical painful stimulation at left or right middle finger; imperative stimuli triggered motor sequences with right index finger. Electroencephalographic data (N = 10, 128 electrodes) were spatially enhanced by surface Laplacian transformation. Cortical activity as revealed by the alpha event-related desynchronization (ERD) was compared in “Pain + ipsilateral movement” condition (movements and painful stimuli performed at the right hand) vs. “Pain + contralateral movement” condition (painful stimuli at left hand and movements performed at the right hand). Results showed that compared with the “Pain + contralateral movement” condition, the “Pain + ipsilateral movement” condition induced lower anticipatory alpha ERD (about 10–12 Hz) in left sensorimotor area, lower subjective pain rate, and delayed movement initiation at the group level. These findings suggest that anticipatory alpha rhythms may underlie cortical preparatory sensorimotor processes preceding somatosensory painful and the initiation of sequential motor events occurring at unilateral or bilateral hand.     

Cardiovascular autonomic function tests to provide normative data from a healthy older population

We aimed to derive normative data for cardiovascular autonomic function tests (AFT) in an older population using new measures. The AFT were performed in 48 healthy control subjects. The average heart rate (HR) response to deep breathing (DB) (HR_DB), Valsalva ratio (VR), magnitude of the HR and blood pressure (BP) response of different phases of the Valsalva maneuver, BP recovery times (PRT 100 and PRT 50) and HR and BP changes on head-up tilting were calculated. The mean age (±standard deviation) of study participants was 58 ± 14.5 years (range 20–82 years), of whom 29 (60%) were men. The systolic blood pressure (SBP) early phase 2 amplitude showed an inverse relationship with age (p = 0.03). There was a trend for progressive attenuation of SBP late phase 2 amplitude with age (p = 0.09). The systolic BP recovery time was not affected by age, gender or body mass index. We concluded that age has a significant effect on most AFT variables. Age and gender did not influence the systolic BP recovery time; hence, systolic BP recovery time could be useful in the evaluation of adrenergic failure.     

Differentiated effects of deep brain stimulation and medication on somatosensory processing in Parkinson’s disease

ObjectivesDeep brain stimulation (DBS) and dopaminergic medication effectively alleviate the motor symptoms in Parkinson’s disease (PD) patients, but their effects on the sensory symptoms of PD are still not well understood. To explore early somatosensory processing in PD, we recorded magnetoencephalography (MEG) from thirteen DBS-treated PD patients and ten healthy controls during median nerve stimulation.MethodsPD patients were measured during DBS-treated, untreated and dopaminergic-medicated states. We focused on early cortical somatosensory processing as indexed by N20m, induced gamma augmentation (31–45 Hz and 55–100 Hz) and induced beta suppression (13–30 Hz). PD patients’ motor symptoms were assessed by UPDRS-III.ResultsUsing Bayesian statistics, we found positive evidence for differentiated effects of treatments on the induced gamma augmentation (31–45 Hz) with highest gamma in the dopaminergic-medicated state and lowest in the DBS-treated and untreated states. In contrast, UPDRS-III scores showed beneficial effects of both DBS and dopaminergic medication on the patients’ motor symptoms. Furthermore, treatments did not affect the amplitude of N20m.ConclusionsOur results suggest differentiated effects of DBS and dopaminergic medication on cortical somatosensory processing in PD patients despite consistent ameliorating effects of both treatments on PD motor symptoms.SignificanceThe differentiated effect suggests differences in the effect mechanisms of the two treatments.     

Unilateral strength training increases voluntary activation of the opposite untrained limb

ObjectiveWe investigated whether an increase in neural drive from the motor cortex contributes to the cross-limb transfer of strength that can occur after unilateral strength training.MethodsTwitch interpolation was performed with transcranial magnetic stimulation to assess changes in strength and cortical voluntary activation in the untrained left wrist, before and after 4 weeks of unilateral strength-training involving maximal voluntary isometric wrist extension contractions (MVCs) for the right wrist (n = 10, control group = 10).ResultsWrist extension MVC force increased in both the trained (31.5 ± 18%, mean ± SD, p < 0.001) and untrained wrist (8.2 ± 9.7%, p = 0.02), whereas wrist abduction MVC did not change significantly. The amplitude of the superimposed twitches evoked during extension MVCs decreased by 35% (±20%, p < 0.01), which contributed to a significant increase in voluntary activation (2.9 ± 3.5%, p < 0.01). Electromyographic responses to cortical and peripheral stimulation were unchanged by training. There were no significant changes for the control group which did not train.ConclusionUnilateral strength training increased the capacity of the motor cortex to drive the homogolous untrained muscles.SignificanceThe data show for the first time that an increase in cortical drive contributes to the contralateral strength training effect.     

Intraoperative monitoring of carotid endarterectomy by transcranial motor evoked potential: A multicenter study of 600 patients

ObjectiveThis study was to investigate the utility of motor evoked potential monitoring elicited by transcranial electrical stimulation (tcMEP) during CEA in addition to the established median nerve somatosensory evoked potentials (mSSEPs).MethodsWe retrospectively reviewed data from 600 patients undergoing CEA under general anesthesia with monitoring of mSSEPs and tcMEPs in a multicenter study. MSSEP and tcMEP parameters were recorded during internal carotid artery (ICA) cross clamping and compared with the postoperative motor outcome, demographic and patient history data.ResultsThe intraoperative monitoring of tcMEPs was successful in 594 of the patients (99%) and selective shunt was performed in 29 of them (4.83%). Nine of the patients showed a transient contralateral loss of tcMEPs, without changes in mSSEPs and required intervention (1.5% “false-negative”). Three of them showed postoperative motor deficits. The time period from tcMEP loss to intervention was significantly longer (p = 0.01) in this group compared to the patients without postoperative motor deficit.ConclusionTcMEPs during CEA may be an adjunct to mSSEP monitoring to avoid “false-negative” mSSEP results, as mSSEPs seem to lack specificity for detecting isolated ischemia of corticospinal pathway.SignificanceTcMEPs seem to improve postoperative outcome, especially in case of a timely correction of cerebral ischemia.     

Lack of differential motor outcome with subthalamic nucleus region stimulation in Parkinson’s disease

Deep brain stimulation (DBS) has emerged as a viable therapy for Parkinson’s disease (PD). The impact of subthalamic nucleus (STN) lead placement (lateral versus medial) on motor outcome, however, has not been systematically evaluated. Forty-eight patients with PD underwent STN-DBS surgery and were evaluated postoperatively for 48 weeks for motor improvement as measured by the Unified Parkinson’s Disease Rating Scale (UPDRS) part III (standardized motor examination) and levodopa equivalent daily dose (LEDD). Postoperative MRI was used to identify the location of the active stimulating contact and motor outcome was analyzed. STN-DBS was associated with significant improvement in motor outcome as determined by a reduction in the UPDRS part III subscore from 34.44 ± 1.29 at baseline to 18.76 ± 1.06 at end visit (p < 0.0001) and a reduction in LEDD from 1721 ± 152 mg/day at baseline to 1134 ± 119 mg/day at end visit (p = 0.0024). Patients with stimulating contacts in the medial STN compared to the lateral STN did not demonstrate any significant differences in motor outcome (UPDRS, p = 0.5811; LEDD, p = 0.7341). No significant differences were found in motor outcome between patients with STN stimulation compared to stimulation of surrounding fiber tracts (p = 0.80). No significant difference in stimulation voltage was noted with respect to lead location. Our study did not find a significant effect for the location of active contact and motor outcome neither within the subregions of the STN nor between the STN and surrounding fibers. Further research is needed to better understand the neurophysiological basis for these results.     

A meta-analysis of cortical inhibition and excitability using transcranial magnetic stimulation in psychiatric disorders

ObjectiveTo evaluate transcranial magnetic stimulation (TMS) measures of inhibition and excitation in obsessive–compulsive disorder (OCD), major depressive disorder (MDD) and schizophrenia (SCZ).MethodsParadigms included: short-interval cortical inhibition (SICI), cortical silent period (CSP), resting motor threshold, intracortical facilitation, and motor evoked potential amplitude. A literature search was performed using PubMed, Ovid Medline, Embase Psychiatry and PsycINFO 1990 through April 2012.ResultsA significant Hedge’s g was found for decreased SICI (g = 0.572, 95% confidence interval [0.179, 0.966], p = 0.004), enhanced intracortical facilitation (g = 0.446, 95% confidence interval [0.042, 0.849], p = 0.030) and decreased CSP (g = ?0.466, 95% confidence interval [?0.881, ?0.052], p = 0.027) within the OCD population. For MDD, significant effect sizes were demonstrated for decreased SICI (g = 0.641, 95% confidence interval [0.384, 0.898], p = 0.000) and shortened CSP (g = ?1.232, 95% confidence interval [?1.530, ?0.933], p = 0.000). In SCZ, a significant Hedge’s g was shown for decreased SICI (g = 0.476, 95% confidence interval [0.331, 0.620], p = 0.000).ConclusionInhibitory deficits are a ubiquitous finding across OCD, MDD, SCZ and enhancement of intracortical facilitation is specific to OCD.SignificanceProvides a clear platform from which diagnostic procedures can be developed.     

Effects of spinal cord stimulation on the cortical somatosensory evoked potentials in failed back surgery syndrome patients

ObjectiveTo evaluate the functional activation of the somatosensory cortical regions in neuropathic pain patients during therapeutic spinal cord stimulation (SCS).MethodsIn nine failed back surgery syndrome patients, the left tibial and the left sural nerves were stimulated in two sessions with intensities at motor and pain thresholds, respectively. The cortical somatosensory evoked potentials were analyzed using source dipole analysis based on 111 EEG signals.ResultsThe short-latency components of the source located in the right primary somatosensory cortex (SI: 43, 54 and 65 ms) after tibial nerve stimulation, the mid-latency SI component (87 ms) after sural nerve stimulation, and the mid-latency components in the right (≈161 ms) and left (≈168 ms) secondary somatosensory cortices (SII) were smaller in the presence of SCS than in absence of SCS. The long-latency source component arising from the mid-cingulate cortex (≈313 ms) was smaller for tibial and larger for sural nerve stimuli during SCS periods compared to periods without SCS.ConclusionsSCS attenuates the somatosensory processing in the SI and SII. In the mid-cingulate cortex, the effect of SCS depends on the type of stimulation and nerve fibers involved.SignificanceResults suggest that the effects of SCS on cortical somatosensory processing may contribute to a reduction of allodynia during SCS.     

The threshold of cortical electrical stimulation for mapping sensory and motor functional areas

This study aimed to investigate the threshold of cortical electrical stimulation (CES) for functional brain mapping during surgery for the treatment of rolandic epilepsy. A total of 21 patients with rolandic epilepsy who underwent surgical treatment at the Beijing Institute of Functional Neurosurgery between October 2006 and March 2008 were included in this study. Their clinical data were retrospectively collected and analyzed. The thresholds of CES for motor response, sensory response, and after discharge production along with other threshold-related factors were investigated. The thresholds (mean ± standard deviation) for motor response, sensory response, and after discharge production were 3.48 ± 0.87, 3.86 ± 1.31, and 4.84 ± 1.38 mA, respectively. The threshold for after discharge production was significantly higher than those of both the motor and sensory response (both p < 0.05). A negative linear correlation was found between the threshold of after discharge production and disease duration. Using the CES parameters at a stimulation frequency of 50 Hz and a pulse width of 0.2 ms, the threshold of sensory and motor responses were similar, and the threshold of after discharge production was higher than that of sensory and motor response.     

Does somatosensory discrimination activate different brain areas in children with unilateral cerebral palsy compared to typically developing children? An fMRI study

Aside from motor impairment, many children with unilateral cerebral palsy (CP) experience altered tactile, proprioceptive, and kinesthetic awareness. Sensory deficits are addressed in rehabilitation programs, which include somatosensory discrimination exercises. In contrast to adult stroke patients, data on brain activation, occurring during somatosensory discrimination exercises, are lacking in CP children. Therefore, this study investigated brain activation with functional magnetic resonance imaging (fMRI) during passively guided somatosensory discrimination exercises in 18 typically developing children (TD) (age, M = 14 ± 1.92 years; 11 girls) and 16 CP children (age, M = 15 ± 2.54 years; 8 girls). The demographic variables between both groups were not statistically different. An fMRI compatible robot guided the right index finger and performed pairs of unfamiliar geometric shapes in the air, which were judged on their equality. The control condition comprised discrimination of music fragments. Both groups exhibited significant activation (FDR, p < .05) in frontoparietal, temporal, cerebellar areas, and insula, similar to studies in adults. The frontal areas encompassed ventral premotor areas, left postcentral gyrus, and precentral gyrus; additional supplementary motor area (SMA_proper) activation in TD; as well as dorsal premotor, and parietal operculum recruitment in CP. On uncorrected level, p < .001, TD children revealed more left frontal lobe, and right cerebellum activation, compared to CP children. Conversely, CP children activated the left dorsal cingulate gyrus to a greater extent than TD children. These data provide incentives to investigate the effect of somatosensory discrimination during rehabilitation in CP, on clinical outcome and brain plasticity.     

Deep brain stimulation of the lateral cerebellar nucleus produces frequency-specific alterations in motor evoked potentials in the rat in vivo

The cerebral cortex is tightly and reciprocally linked to the cerebellum and the ascending dentato-thalalmo-cortical pathway influences widespread cortical regions. Using a rodent model of middle cerebral artery stroke, we showed previously that chronic, 20 Hz stimulation of the contralateral lateral cerebellar nucleus (LCN) improved motor recovery, while 50 Hz stimulation did not. Using motor evoked potentials (MEP) elicited by intracortical microstimulation, we now show the effect of LCN stimulation on motor cortex excitability as a function of pulse frequency in propofol-anesthetized rats. MEPs were recorded serially, at 15-s intervals, with cerebellar stimulation delivered in 10-min blocks at rates of 20, 30, 40, 50 or 100 Hz. Stimulation at 20, 30, 40 or 50 Hz enhanced the average MEP response across the block, with the maximal overall increase observed during 30 Hz stimulation. However, the effect varied as a function of both repeated trials within the block and LCN stimulation frequency, such that 40 Hz and 50 Hz stimulation showed a reduced effect over time. Stimulation at 100 Hz produced a transient increase in MEP amplitude in some animals; however the overall effect across the block was a trend towards reduced cortical excitability. These results suggest that direct stimulation of the LCN can yield frequency-dependent changes in cortical excitability and may provide a therapeutic approach to modulating cortical activity for the treatment of strokes or other focal cortical lesions, movement disorders and epilepsy.     

Central nervous system abnormalities in vaginismus

ObjectiveTo investigate possible altered CNS excitability in vaginismus.MethodsIn 10 patients with primary idiopathic lifelong vaginismus, 10 with vulvar vestibulitis syndrome accompanied by vaginismus and healthy controls we recorded EMG activity from the levator ani (LA) and external anal sphincter (EAS) muscles and tested bulbocavernosus reflex (BCR). Pudendal-nerve somatosensory evoked potentials (SEPs) were tested after a single stimulus. Pudendal-nerve SEP recovery functions were assessed using a paired conditioning-test paradigm at interstimulus intervals (ISIs) of 5, 20 and 40 ms.ResultsEMG in patients showed muscular hyperactivity at rest and reduced inhibition during straining. The BCR polysynaptic R2 had larger amplitude (p < 0.01) and longer duration (p < 0.01) in patients from both groups than in controls. In controls, paired-pulse SEPs were suppressed at the 5 ms ISI for N35–P40 (p < 0.05) and P40–N50 ms (p < 0.001) and facilitated at the 20 ms ISI for N35–P40 (p < 0.05) and P40–N50 (p < 0.05). No significant differences were found in the paired-pulse N35–P40 in patients and controls but the cortical P40–N50 at 20 ISI was facilitated in patients (p < 0.05).ConclusionsEMG activity is enhanced and the cortical SEP recovery cycle and BCR are hyperexcitable in vaginismus.SignificanceThe neurophysiological abnormalities in patients with vaginismus indicate concomitant CNS changes in this disorder.     

Effects of transcranial direct current stimulation on esophageal motility in patients with gastroesophageal reflux disease

ObjectiveTo evaluate the effects of transcranial direct current stimulation (tDCS) on esophageal peristalsis in patients with gastroesophageal reflux disease (GERD).MethodsPatients with GERD preliminary diagnosis were included in a randomized double-blind sham-controlled study. Esophageal manometry was performed before and during transcranial direct current stimulation (tDCS) of the right precentral cortex. Half of patients were randomly assigned to anodal, half to sham stimulation. Distal waves amplitude and pathological waves percentage were measured, after swallowing water boli, for ten subsequent times. Last, a 24 h pH-bilimetry was done to diagnose non-erosive reflux disease (NERD) or functional heartburn (FH). The values obtained before and during anodal or sham tDCS were compared.ResultsSixty-eight patients were enrolled in the study. Distal waves mean amplitude increased significantly only during anodal tDCS in NERD (p = 0.00002) and FH subgroups (p = 0.008) while percentage of pathological waves strongly decreased only in NERDs (p = 0.002).ConclusionsTranscranial stimulation can influence cortical control of esophageal motility and improve pathological motor pattern in NERD and FH but not in erosive reflux disease (ERD) patients.SignificancePathophysiological processes in GERD are not only due to peripheral damage but to central neural control involvement as well. In ERD patients dysfunctions of the cortico-esophageal circuit seem to be more severe and may affect central nervous system physiology.     

Outcomes and patterns of care in adult skull base chondrosarcomas from the SEER database

This study aims to demonstrate survival rates and treatment patterns among patients with chondrosarcomas of the skull base using a large population database. Patients with skull base chondrosarcomas between 1973 and 2009 were identified from the USA Surveillance, Epidemiology, and End Results (SEER) database. Kaplan–Meier survival analysis was used to examine the effect of surgery and radiation on overall survival. We identified 226 patients with skull base chondrosarcomas. Median follow-up was 5.4 years. Median overall survival was 22 years, and 10 year survival was 68.2%. Most patients underwent surgery (92.5%). Few received radiation after diagnosis (38.1%). Ten year survival for all patients treated with surgery was significantly increased compared to those without surgery (69.3% versus 53.9%, p = 0.02). There was a significant difference in survival amongst treatment groups (p = 0.02), with median overall survival not yet reached for patients who received surgery and radiation (median follow-up 5.3 years), compared to 22 years for non-irradiated surgical patients. Surgery predicted better overall survival by univariate analysis (hazard ratio [HR] 0.420, p = 0.03). Female sex (HR 0.470, p = 0.011), younger age at diagnosis (HR 1.046, p < 0.0001), and later year of diagnosis (HR 0.949, p = 0.0006) were prognostic of improved survival in a multivariate model. In subgroup analysis of patients with documented tumor size, smaller tumor size (HR 1.054, p = 0.0003) and younger age (HR 1.021, p = 0.0067) predicted improved survival. This population based study further reaffirms the role of surgery as an effective treatment for skull base chondrosarcoma as previously reported in small case series. Adjuvant radiation may also confer survival benefit. Optimal treatment strategy has yet to be defined in the literature.     

Outcomes and patterns of care in adult skull base chordomas from the Surveillance,Epidemiology, and End Results (SEER) database

This study aims to demonstrate survival rates and treatment patterns among patients with chordomas of the skull base using a large population database. Patients with cranial chordomas between 1973 and 2009 were identified from the USA Surveillance, Epidemiology, and End Results (SEER) public use database. Kaplan–Meier analysis was used to examine the effect of surgery and radiation on overall survival. We identified 394 patients with histologically-confirmed cranial chordomas. Median survival was 151 months. Most patients (89.09%) underwent surgery. Less than half (44.92%) received radiation after diagnosis. Patients who underwent surgical resection survived significantly longer than those who did not undergo resection, regardless of other treatments (151 versus 81 months, p < 0.001). Ten year survival was lower among patients receiving radiation (44.8% versus 61.4%, p = 0.66). Surgery predicted better overall survival by univariate analysis (hazard ratio [HR] 0.603, p = 0.0293); younger age at diagnosis (HR 1.028, p < 0.001), and later year of diagnosis (HR 0.971, p = 0.0027) were prognostic of improved survival in a multivariate model. In subgroup analysis of patients with documented tumor size, smaller tumor size (HR 1.021, p = 0.0067), younger age (HR 1.031, p = 0.001), and treatment within a higher volume registry (HR 0.490, p = 0.0129) predicted improved survival. Surgical intervention offers survival benefit for cranial chordomas. Findings of decreased survival in patients receiving radiation may be associated with selection. Studies examining surgical extent of resection data and radiation details are needed to determine the impact of radiotherapy.     

Cortical excitability in drug naive juvenile myoclonic epilepsy

PurposeTo evaluate the effect of diurnal variability on cortical excitability using single pulse transcranial magnetic stimulation (TMS), in drug naive patients with juvenile myoclonic epilepsy (JME) and to look for any differences in cortical excitability between males and females.MethodsThirty drug-naive patients with JME and 10 healthy controls were studied. Resting motor threshold (RMT), motor evoked potential (MEP), the duration of central motor conduction time (CMCT) and cortical silent period (CSP) were measured, twice, first early in the morning and again in the afternoon of the same day.ResultsDiurnal variation with higher evening values of CMCT and CSP were observed in the control group. In the study group, diurnal variation in RMT, CMCT and CSP was found with higher values in the morning than in control group. However, only the raised values of CSP [mean, 110.7 ms, morning and 96.44 ms, evening] were of statistical significance [p = 0.005, morning and 0.039, evening] as compared to controls. In the study group, males had higher values of RMT, CMCT and CSP than in females. However, the CMCT in males was lower in the evening study than in females. Further, RMT and morning CMCT was lower in females than in controls. In females, the morning CSP [mean, 100.91 ms, morning versus 87.86 ms, evening] was significantly prolonged [p = 0.017, morning versus 0.221, evening] as compared to controls.ConclusionThe study is suggestive of the existence of impaired supraspinal/intracortical inhibitory circuits which may account for the hyperexcitability of the motor system being prominent in the morning among drug naïve patients with JME. In this study, increased activity of cortical inhibitory networks, as evidenced by prolonged cortical silent period existed among drug naïve JME patients, but was found to be significant only in female patients. This may explain the increased seizure susceptibility in this cohort, at this time of the day and an increased manifestation of JME in females.     

Neuropsychological and psychiatric assessments following bilateral deep brain stimulation of the subthalamic nucleus in Japanese patients with Parkinson’s disease

The physical benefits of subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson’s disease (PD) patients are well documented, but the mental benefits are uncertain, particularly in Japanese patients. This study evaluated the clinical and neuropsychological characteristics before and after STN-DBS surgery in Japanese PD patients. PD patients (n = 13, age 67.0 ± 7.8 years) were evaluated pre-surgery (baseline) and at 1 and 6 months post-surgery by two trained psychiatrists. The motor symptoms were assessed by the Unified Parkinson’s Disease Rating Scale (UPDRS) motor score. The neuropsychological and psychiatric tests performed were the Mini-Mental State Examination, the Wisconsin Card Sorting Test (WCST), the Verbal Fluency Test (VFT), the Hamilton Depression Rating Scale and the Hamilton Anxiety Rating Scale (HAM-A). The UPDRS motor score (p < 0.001) and HAM-A score (p = 0.004) showed significant improvement at 1 month post-surgery, but a significant decline was observed in the WCST total error (p = 0.005) and the semantic VFT score (p < 0.001). The phonetic VFT also showed a substantial decline (p = 0.015) at 1 month post-surgery. At 6 months post-surgery, the improvement in the UPDRS motor score was maintained, and the scores on the neuropsychological and psychiatric tests had returned to baseline. Although bilateral STN-DBS did not appear to have long-term effects on neuropsychological and psychiatric outcomes, the microlesion effects associated with STN-DBS appear to increase the risk of transient cognitive and psychiatric complications. These complications should be monitored by careful observation of neurological and psychiatric symptoms.     

Effects of continuous theta burst transcranial magnetic stimulation on cortical excitability in patients with idiopathic generalized epilepsy

IntroductionTranscranial magnetic stimulation (TMS) is a noninvasive technique for investigating cortical physiologic functions in the brain. In this study, the effects of continuous theta burst stimulation (cTBS) on motor evoked potential (MEP) parameters in patients with idiopathic generalized epilepsy (IGE) were investigated.Materials and methodsFifteen patients with IGE were included. Motor threshold (MT) and cortical silent period (CSP) were determined before cTBS application. Next, cTBS was applied to the dominant (left) hemisphere M1 hand area as the first application. After 1 day, cTBS was applied first to the left M1 hand area and then to the right lateral cerebellar area as the second application. Parameters were again determined after the applications.ResultsThere was no difference in resting MT values before and after cTBS application (p > 0.05). Although CSP increased after stimulation (p < 0.05), it was not significantly different between applications (p > 0.05).ConclusionFor patients with epilepsy, cTBS is a safe technique when applied at a low intensity. The inhibitory effect of cTBS, a noninvasive technique, on cortical excitability in patients with IGE was determined using MEP parameters. The effect lasted at least 1 h. To our knowledge, this is the first study to assess the effect of cTBS on cortical excitability in patients with IGE. Our findings indicate that cTBS decreases cortical excitability in patients with IGE.     

Reduced plastic brain responses to repetitive transcranial magnetic stimulation in severe obstructive sleep apnea syndrome

ObjectivesAbnormalities in cortical excitability have been proposed to underlie the pathophysiology of various neurocognitive manifestations of obstructive sleep apnea syndrome (OSAS). Transcranial magnetic stimulation (TMS) provides a noninvasive method for study and modulation of cortical excitability in the human brain, and repetitive TMS (rTMS) has been proven useful for neurophysiologic investigation in various neurologic conditions. We aimed to investigate cortical excitability in patients with OSAS during wakefulness and to determine if rTMS would change the abnormal excitability patterns.MethodsMeasures of motor cortical and corticospinal excitability (resting motor threshold [RMT], motor-evoked potential [MEP] amplitude, and cortical silent period [CSP]) were taken before and after a session of 10-Hz rTMS applied to the motor cortex in 13 individuals with untreated severe OSAS (apnea–hypopnea index [AHI] > 30) and 12 age- and sex-matched healthy controls (HC).ResultsOSAS subjects had a significantly higher RMT (P < .003) and a longer CSP duration (P < .002) compared to HC. No difference was observed between MEP values of OSAS subjects and HC (P > .05). In response to rTMS, the HC group had a significant increase in CSP and MEP values from baseline, which were absent in OSAS subjects.ConclusionsIndividuals with OSAS demonstrated increased motor cortex inhibition, which did not respond to 10-Hz rTMS. As rTMS-induced changes in MEP and CSP involve a separate neurotransmitter system (N-methyl-d-aspartate [NMDA] and gamma-aminobutyric acid [GABA], respectively), these findings suggest a widespread alteration in cortical neurophysiology in severe OSAS subjects that requires clarification with further exploration.     

The effects of EEG suppression and anesthetics on stimulus thresholds in functional cortical motor mapping

ObjectiveTo investigate the effects of EEG suppression and anesthetics on variability of electrical stimulus thresholds during functional cortical motor mapping, and the possible influences of age, lesion location and pathology.MethodsMultivariate regression analysis was performed to study these relationships in 60 cases of successful mapping using the monopolar multipulse train technique.ResultsAn increase in the length of EEG “flats” by 1 s produced an increase in stimulus threshold by 1.08 mA (p = 0.0004). Administration of TIVA (total intravenous anesthesia) or inhalational agents produced an additional increase in threshold by 1.27 mA (p = 0.38) or 4.84 mA (p = 0.04) respectively, when compared to awake patients.ConclusionsDepth of cortical suppression impacts the stimulus thresholds. The effect of TIVA on thresholds is mediated by its effect on cortical excitability. The effects of inhalational agents on thresholds involve their influence on excitability at other levels of the neuraxis.SignificanceThe study represents an important step towards building a predictive model for stimulus thresholds. It also improves our understanding of the relationships of anesthetics, EEG burst suppression pattern and age with cortical excitability.