Abnormal Cortical Excitability Research Articles

Influence of sports on cortical excitability in patients with spinal cord injury: a TMS study.

Patients with spinal cord injury (SCI) show abnormal cortical excitability that might be caused by deafferentation. We hypothesize a reduced short-interval intracortical inhibition preceding movement in patients with SCI compared with healthy participants. In addition, we expect that neuroplasticity induced by different types of sports can modulate intracortical inhibition during movement preparation in patients with SCI. We used a reaction test and paired-pulse transcranial magnetic stimulation to record cortical excitability, assessed by measuring amplitudes of motor-evoked potentials in preparation of movement. The participants were grouped as patients with SCI practicing wheelchair dancing (n = 7), other sports (n = 6), no sports (n = 9), and healthy controls (n = 24). There were neither significant differences between healthy participants and the patients nor between the different patient groups. A non-significant trend (p = .238), showed that patients engaged in sports have a stronger increase in cortical excitability compared with patients of the non-sportive group, while the patients in the other sports group expressed the highest increase in cortical excitability. The small sample sizes limit the statistical power of the study, but the trending effect warrants further investigation of different sports on the neuroplasticity in patients with SCI. It is not clear how neuroplastic changes impact the sensorimotor output of the affected extremities in a patient. This needs to be followed up in further studies with a greater sample size.

429. Evidence for Abnormal Cortical Excitability Across Sensory Modalities in High Schizotypy

429. Evidence for Abnormal Cortical Excitability Across Sensory Modalities in High Schizotypy

Pediatric Migraine and Visual Cortical Excitability: A Prospective Observational Study with Sound-Induced Flash Illusions.

The pathophysiological mechanisms underlying migraine are more difficult to investigate in children than in the adult population. Abnormal cortical excitability turns out to be one of the most peculiar aspects of migraine, accounting for the manifestations of migraine attacks. Recently, visual cortical excitability has been explored effectively in adult migraineurs with a technique based on cross-modal audio-visual illusions (with sound-induced flash illusions (SIFIs) being reduced in migraineurs compared to non-migraineur subjects). On such a basis, in this study, we investigated visual cortical excitability in children with migraine using SIFIs using combinations of visual and sound stimuli presented randomly. We evaluated 26 children with migraine without aura and 16 healthy children. Migraineurs did not differ from the age-matched healthy subjects regarding fission or fusion illusions but perceived more flashes in trials of multiple flashes with or without beeps. The higher number of SIFIs in migraineur children compared to adults may be due to a greater propensity of visual stimulation to be driven by auditory stimuli (i.e., acoustic dominance). The increased ability to perceive flashes reveals a hyperfunctional visual cortex, demonstrating that the use of SIFIs is a valid tool for assessing visual cortical responsiveness even in pediatric migraine.

Abnormal cortical excitability in patients with spinocerebellar ataxia type 12

BackgroundSpinocerebellar ataxia type 12 (SCA-12) is an uncommon autosomal dominant cerebellar ataxia characterized by action tremors in the upper limbs, dysarthria, head tremor, and gait ataxia. We aimed to evaluate the motor cortical excitability in patients with SCA-12 using transcranial magnetic stimulation (TMS). MethodsThe study was done in the department of Neurology at the National Institute of Mental Health and Neuro Sciences (NIMHANS), Bangalore. Nine patients with SCA-12 (2 females) and 10 healthy controls (2 females) were included in the study. TMS was performed in all the subjects and various parameters such as resting motor threshold (RMT), central motor conduction time (CMCT) and contralateral silent period (cSP) were recorded. The left motor cortex was stimulated and the recording was done from right first dorsal interossei muscle. The severity of ataxia was assessed using the scale for assessment and rating in ataxia (SARA). ResultsThe mean age of the patients was 58.11 ± 7.56 years mean age at onset: 51.67 ± 4.18 years. The mean duration of illness was 9.44 ± 4.88 years. The mean SARA score was 13.83 ± 3.60. Patients with SCA-12 had significantly increased RMT (88.80 ± 12.78 %) compared to HC (44.90 ± 9.40 %, p < 0.05). A significantly prolonged CMCT was observed in patients (13.70 ± 2.52 msec) compared to HC (7.31 ± 1.21 msec, p < 0.05). In addition, cSP was significantly increased in SCA-12 patients (144.43 ± 25.79 msec) compared to HC (82.14 ± 28.90 msec, p < 0.05). ConclusionsPatients with SCA-12 demonstrate a reduced cortical excitability and increased cortical inhibition suggesting an increase in the GABAergic neurotransmission.

A mini-review of the pathophysiology of task-specific tremor: insights from electrophysiological and neuroimaging findings

Task-specific tremor (TST) is a specific type of tremor that occurs when performing or attempting to perform a specific task, such as writing or playing a musical instrument. The clinical entity of TST remains heterogeneous. Some TSTs can only be induced by conducting a specific task, while others can be elicited when adopting a particular position simulating a task. The pathophysiology of TST is controversial. Whether TST is an isolated tremor syndrome, a spectrum of dystonic tremor syndrome (DTS), or essential tremor (ET) is not yet clear. Evidence from electrophysiological studies suggests that TST patients have normal reciprocal inhibition responses but abnormal motor cortical excitability, especially relating to the maladaptive long-interval intracortical inhibitory circuitry. The blink recovery study and eyeblink classical conditioning studies demonstrated possible hyperexcitability of the brainstem circuits and cerebellar dysfunction in patients with TST. Functional MRI studies have further shown that patients with TST have reduced functional connectivity in the cerebellum, similar to patients with DTS and ET. Due to variable methodologies and the sparsity of functional MRI studies in TST, it remains uncertain if patients with TST share the connectivity abnormalities between the cortical or subcortical areas that have been demonstrated in patients with DTS. Comprehensive electrophysiological and functional neuroimaging studies may help to elucidate the pathophysiology of TST.

Exploring sensory sensitivity, cortical excitability, and habituation in episodic migraine, as a function of age and disease severity, using the pattern-reversal task

BackgroundMigraine is a cyclic, neurosensory disorder characterized by recurrent headaches and altered sensory processing. The latter is manifested in hypersensitivity to visual stimuli, measured with questionnaires and sensory thresholds, as well as in abnormal cortical excitability and a lack of habituation, assessed with visual evoked potentials elicited by pattern-reversal stimulation. Here, the goal was to determine whether factors such as age and/or disease severity may exert a modulatory influence on sensory sensitivity, cortical excitability, and habituation.MethodsTwo similar experiments were carried out, the first comparing 24 young, episodic migraine patients and 28 healthy age- and gender-matched controls and the second 36 middle-aged, episodic migraine patients and 30 healthy age- and gender-matched controls. A neurologist confirmed the diagnoses. Migraine phases were obtained using eDiaries. Sensory sensitivity was assessed with the Sensory Perception Quotient and group comparisons were carried out. We obtained pattern-reversal visual evoked potentials and calculated the N1-P1 Peak-to-Peak amplitude. Two linear mixed-effects models were fitted to these data. The first model had Block (first block, last block) and Group (patients, controls) as fixed factors, whereas the second model had Trial (all trials) and Group as fixed factors. Participant was included as a random factor in both. N1-P1 first block amplitude was used to assess cortical excitability and habituation was defined as a decrease of N1-P1 amplitude across Blocks/Trials. Both experiments were performed interictally.ResultsThe final samples consisted of 18 patients with episodic migraine and 27 headache-free controls (first experiment) and 19 patients and 29 controls (second experiment). In both experiments, patients reported increased visual hypersensitivity on the Sensory Perception Quotient as compared to controls. Regarding N1-P1 peak-to-peak data, there was no main effect of Group, indicating no differences in cortical excitability between groups. Finally, significant main effects of both Block and Trial were found indicating habituation in both groups, regardless of age and headache frequency.ConclusionsThe results of this study yielded evidence for significant hypersensitivity in patients but no significant differences in either habituation or cortical excitability, as compared to headache-free controls. Although the alterations in patients may be less pronounced than originally anticipated they demonstrate the need for the definition and standardization of optimal methodological parameters.

Deficient GABABergic and glutamatergic excitability in the motor cortex of patients with long-COVID and cognitive impairment

ObjectiveAttention, working memory and executive processing have been reported to be consistently impaired in Neuro-Long coronavirus disease (COVID). On the hypothesis of abnormal cortical excitability, we investigated the functional state of inhibitory and excitatory cortical regulatory circuits by single “paired-pulse” transcranial magnetic stimulation (ppTMS) and Short-latency Afferent Inhibition (SAI). MethodsWe compared clinical and neurophysiological data of 18 Long COVID patients complaining of persistent cognitive impairment with 16 Healthy control (HC) subjects. Cognitive status was evaluated by means of the Montreal Cognitive Assessment (MoCA) and a neuropsychological evaluation of the executive function domain; fatigue was scored by the Fatigue Severity Scale (FSS). Resting motor threshold (RMT), the amplitude of the motor evoked potential (MEP), Short Intra-cortical Inhibition (SICI), Intra-cortical Facilitation (ICF), Long-interval Intracortical Inhibition (LICI) and Short-afferent inhibition (SAI) were investigated over the motor (M1) cortex. ResultsMoCA corrected scores were significantly different between the two groups (p = 0.023). The majority of the patients’ performed sub-optimally in the neuropsychological assessment of the executive functions. The majority (77.80%) of the patients reported high levels of perceived fatigue in the FSS. RMT, MEPs, SICI and SAI were not significantly different between the two groups. On the other hand, Long COVID patients showed a reduced amount of inhibition in LICI (p = 0.003) and a significant reduction in ICF (p < 0.001). ConclusionsNeuro-Long COVID patients performing sub-optimally in the executive functions showed a reduction of LICI related to GABAb inhibition and a reduction of ICF related to glutamatergic regulation. No alteration in cholinergic circuits was found. SignificanceThese findings can help to better understand the neurophysiological characteristics of Neuro-Long COVID, and in particular, motor cortex regulation in people with “brain fog”.

Increased Perirolandic Cortical Excitability May Facilitate Sensory Motor Mapping in Children (P13-1.003)

<h3>Objective:</h3> We are hereby describing a case of refractory pediatric epilepsy where resection of perirolandic seizure foci was performed successfully under neurophysiologic guidance. <h3>Background:</h3> Pediatric neurophysiologic sensory-motor mapping is frequently unsuccessful, due to inability to localize central sulcus (CS) and primary motor cortex (M1). These shortcomings result from poor somatosensory evoked potentials (SSEP) and high M1 depolarization thresholds respectively, both reflections of the immaturity of the central nervous system. <h3>Design/Methods:</h3> Case report <h3>Results:</h3> An 8-year-old boy with developmental delay, debilitating focal epilepsy and epileptic encephalopathy underwent phase 2 video EEG monitoring. The recordings showed seizures with early involvement of several depth electrodes located within the right parieto-frontal regions, and an early motor semiology involving the left arm. The patient underwent neurophysiologically guided resection of the seizure foci under general anesthesia. Pre-resection electrocorticography (ECoG) via a 64 contact grid showed abundant perirolandic epileptiform discharges (ED), maximal postcentrally. Cortical recordings of high amplitude median SSEP and a low depolarization threshold led to successful CS localization and identification of M1, respectively. A subdural strip electrode placed over the precentral gyrus and secured in position, allowed simultaneous ECoG and motor monitoring during the resection of the postcentral foci. Initially, ECoG showed near continuous runs of ED, unchanged by cortical electrical stimulation. Under steady state anesthesia, at a constant propofol infusion rate, this activity decreased in frequency and stopped altogether towards the end stages of the resection, as the M1 threshold increased by 7 mA. Post-resection fronto-parietal ECoG recordings were quiet. Post-operatively, the patient became seizure free, showed cognitive improvement and no motor deficits. <h3>Conclusions:</h3> Increased cortical excitability may lead to successful functional mapping in children. Under steady anesthetic conditions, increases in the M1 threshold during resection of nearby epileptic foci may be an early sign of decrease in the abnormal regional cortical excitability. <b>Disclosure:</b> Dr. Alzahrany has nothing to disclose. Dr. Simon has received personal compensation in the range of $500-$4,999 for serving as an Expert Witness for Risk Management Foundation of the Harvard Institutions Incorporated. Dr. Simon has received personal compensation in the range of $5,000-$9,999 for serving as an Expert Witness for MCIC Vermont. Dr. Simon has received personal compensation in the range of $5,000-$9,999 for serving as an Expert Witness for Aaronson, Rappaport, Feinstein&amp; Deutch. Dr. Simon has received publishing royalties from a publication relating to health care. Dr. Simon has received personal compensation in the range of $0-$499 for serving as a Speaker with American Clinical Neurophysiology Society . Dr. Simon has a non-compensated relationship as a Speaker with International Society of Intraoperative Neurophysiology that is relevant to AAN interests or activities. Dr. Simon has a non-compensated relationship as a Speaker with Brazilian Congress of Neurology that is relevant to AAN interests or activities.

Anodal-TDCS over Left-DLPFC Modulates Motor Cortex Excitability in Chronic Lower Back Pain.

Chronic pain is associated with abnormal cortical excitability and increased pain intensity. Research investigating the potential for transcranial direct current stimulation (tDCS) to modulate motor cortex excitability and reduce pain in individuals with chronic lower back pain (CLBP) yield mixed results. The present randomised, placebo-controlled study examined the impact of anodal-tDCS over left-dorsolateral prefrontal cortex (left-DLPFC) on motor cortex excitability and pain in those with CLBP. Nineteen participants with CLBP (Mage = 53.16 years, SDage = 14.80 years) received 20-min of sham or anodal tDCS, twice weekly, for 4 weeks. Short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were assessed using paired-pulse Transcranial Magnetic Stimulation prior to and immediately following the tDCS intervention. Linear Mixed Models revealed no significant effect of tDCS group or time, on SICI or ICF. The interactions between tDCS group and time on SICI and ICF only approached significance. Bayesian analyses revealed the anodal-tDCS group demonstrated higher ICF and SICI following the intervention compared to the sham-tDCS group. The anodal-tDCS group also demonstrated a reduction in pain intensity and self-reported disability compared to the sham-tDCS group. These findings provide preliminary support for anodal-tDCS over left-DLPFC to modulate cortical excitability and reduce pain in CLBP.

Simultaneous Motor and Visual Intraoperative Neuromonitoring in Asleep Parietal Lobe Surgery: Dual Strip Technique.

Background: The role played by the non-dominant parietal lobe in motor cognition, attention and spatial awareness networks has potentiated the use of awake surgery. When this is not feasible, asleep monitoring and mapping techniques should be used to achieve an onco-functional balance. Objective: This study aims to assess the feasibility of a dual-strip method to obtain direct cortical stimulation for continuous real-time cortical monitoring and subcortical mapping of motor and visual pathways simultaneously in parietal lobe tumour surgery. Methods: Single-centre prospective study between 19 May–20 November of patients with intrinsic non-dominant parietal-lobe tumours. Two subdural strips were used to simultaneously map and monitor motor and visual pathways. Results: Fifteen patients were included. With regards to motor function, a large proportion of patients had abnormal interhemispheric resting motor threshold ratio (iRMTr) (71.4%), abnormal Cortical Excitability Score (CES) (85.7%), close distance to the corticospinal tract—Lesion-To-Tract Distance (LTD)—4.2 mm, Cavity-To-Tract Distance (CTD)—7 mm and intraoperative subcortical distance—6.4 mm. Concerning visual function, the LTD and CTD for optic radiations (OR) were 0.5 mm and 3.4 mm, respectively; the mean intensity for positive subcortical stimulation of OR was 12 mA ± 2.3 mA and 5/6 patients with deterioration of VEPs > 50% had persistent hemianopia and transgression of ORs. Twelve patients remained stable, one patient had a de-novo transitory hemiparesis, and two showed improvements in motor symptoms. A higher iRMTr for lower limbs was related with a worse motor outcome (p = 0.013) and a longer CTD to OR was directly related with a better visual outcome (p = 0.041). At 2 weeks after hospital discharge, all patients were ambulatory at home, and all proceeded to have oncological treatment. Conclusion: We propose motor and visual function boundaries for asleep surgery of intrinsic non-dominant parietal tumours. Pre-operative abnormal cortical excitability of the motor cortex, deterioration of the VEP recordings and CTD < 2 mm from the OR were related to poorer outcomes.

Utilization of EEG in A Teaching Hospital: A Descriptive Cross-Sectional Study

INTRODUCTION Electroencephalography is a safe, convenient, non-invasive, and inexpensive technique that allows assessment of cerebral function and detects physiological manifestations of abnormal cortical excitability. Published literature about its utilization and application is sparse from this part of the world. &#x0D; METHODOLOGY It is a descriptive, cross-sectional study conducted in Nepalgunj Medical College, Kohalpur, Nepal. All the subjects referred for EEG evaluation from January 2019 to December 2020 (two years) were enrolled and EEG was performed. A self-designed proforma was used to record different variables and data was analyzed using Statistical Package for the Social Sciences version 21.0 for Windows.&#x0D; RESULT Of total 246 subjects, 53.3% were male and 58.9% of the subjects were 20 years or younger by age. Maximum (35.8%) number of referrals came from the department of psychiatry. Generalized seizure discharge was the most common EEG diagnosis and presence of seizure activity was noted in 37%of patients.&#x0D; CONCLUSION EEG is utilized by different specialities commonly for seizure disorder, psychiatric disorders and headaches.

Quantitative assessment of cortical excitability in Alzheimer’s dementia and its association with clinical symptoms: A systematic review and meta‐analyses

AbstractBackgroundAlzheimer’s Disease (AD) is characterized by cognitive and neuropsychiatric symptoms (NPS). Studies using electroencephalography (EEG) have shown increased epileptiform and epileptic activity in AD. Transcranial magnetic stimulation (TMS) studies have also shown abnormal cortical excitability in AD, however findings have been inconsistent. Further, relationship between cortical excitability and clinical symptoms of AD is not clear. This review and meta‐analyses aims to synthesize the existing evidence for abnormal cortical excitability in AD and its relationship with clinical symptoms.MethodWe systematically searched and reviewed publications that quantitatively assessed cortical excitability, using TMS resting motor threshold (rMT), active motor threshold (aMT), motor evoked potential (MEP) or directly from the cortex using TMS‐EEG via TMS‐evoked potential (TEP). Effect sizes and 95% confidence intervals (CI) of rMT and aMT were calculated using Hedges’ g and meta‐analyzed using a random effects model. Heterogeneity among studies was assessed by Cochran’s Q and I2 statistic.ResultWe identified 895 publications out of which 68 were reviewed in full‐text and 37 were included in the final review. Thirty studies using rMT and seven using aMT were included in the meta‐analyses. The AD group had reduced rMT (Hedges’ g = ‐0.99, 95% CI [‐1.29, ‐0.68], p &lt; 0.00001) and aMT (Hedges’ g = ‐0.87, 95% CI [‐1.50, ‐0.24], p &lt; 0.00001) as compared with control groups, indicative of higher cortical excitability. Evidence of considerable heterogeneity was found across the studies (Q (29) = 85.68, p &lt; 0.00001, I2 =81%). Qualitative review of the literature showed some evidence of increased MEP amplitude (n = 2 studies), however findings related to TEP were inconsistent. Further, there was some evidence (n = 4 studies) supporting an inverse association between cortical excitability and global cognition. No publications reported on the relationship between cortical excitability and neuropsychiatric symptoms (NPS).ConclusionThere is strong evidence of increased motor cortex excitability in AD and some evidence of an inverse association between excitability and cognition. Future studies should assess cortical excitability from non‐motor areas and examine its relationship with cognition and NPS.

A new, sensitive biomarker for abnormal cortical excitability: Single trial based synchronization and desynchronization with cortical myoclonus

Giant somatosensory evoked potentials (SEPs), i.e., enlarged cortical components of SEPs, represent abnormal cortical excitability such as cortical myoclonus (CM). Recently, we reported high-frequency oscillations (HFOs) with a part of giant SEPs specifically observed in benign adult familial myoclonus epilepsy (Tojima et al., 2021). However, no clear HFOs after N33 were observed. We herein hypothesized, in CM patients, late cortical abnormal excitability may be poorly synchronized in average method and thus only detectable by single trial, event-related synchronization (ERS) and desynchronization (ERD). We also compared ERS/ERD between CM patients and healthy controls (HCs).

Cyclic changes of visual cortical excitability across migraine phases: A study with sound induced flash illusions

Abnormal cortical excitability has a role in migraine but the link with beginning and stop of migraine attacks remains unclear. Critical insight could come by excitability changes across the migraine cycle. Here we explore it through sound induced flash illusions (SIFI). SIFI are cross-modal illusory percepts critically dependent on visual cortical excitability (less illusions = increased excitability) that have been found to be altered in episodic and chronic migraine(1–2).

Quantitative Assessment of Cortical Excitability in Alzheimer’s Dementia and its Association With Clinical Symptoms: A Systematic Review and Meta-Analysis

Alzheimer’s Disease (AD) is characterized by cognitive and neuropsychiatric symptoms (NPS). Some studies have shown abnormal cortical excitability in AD; however, findings have been inconsistent. Further, relationship between cortical excitability and clinical symptoms of AD is not clear. This systematic review and meta-analysis assessed evidence for abnormal cortical excitability and its relationship with clinical symptoms in AD.

Evaluation of Changes in Preoperative Cortical Excitability by Navigated Transcranial Magnetic Stimulation in Patients With Brain Tumor.

Background: This prospective study aimed to evaluate the cortical excitability (CE) of patients with brain tumors surrounding or directly involving the corticospinal tract (CST) using navigated transcranial magnetic stimulation (nTMS).Methods: We recruited 40 patients with a single brain tumor surrounding or directly involving the CST as well as 82 age- and sex-matched healthy controls. The patients underwent standard nTMS and CE evaluations. Single and paired pulses were applied to the primary motor area (M1) of both affected and unaffected cerebral hemispheres 1 week before surgery. The CE parameters included resting motor threshold (RMT), motor evoked potential (MEP) ratio for 140 and 120% stimulus (MEP 140/120 ratio), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF). Motor outcome was evaluated on hospital discharge and on 30-day and 90-day postoperative follow-up.Results: In the affected hemispheres of patients, SICI and ICF were significantly higher than in the unaffected hemispheres (p=0.002 and p=0.009, respectively). The 140/120 MEP ratio of patients' unaffected hemispheres was lower than that in controls (p=0.001). Patients with glioblastomas (GBM) had a higher interhemispheric RMT ratio than patients with grade II and III gliomas (p = 0.018). A weak correlation was observed among the RMT ratio and the preoperative motor score (R2 = 0.118, p = 0.017) and the 90-day follow-up (R2 = 0.227, p = 0.016).Conclusion: Using preoperative nTMS, we found that brain hemispheres affected by tumors had abnormal CE and that patients with GBM had a distinct pattern of CE. These findings suggest that tumor biological behavior might play a role in CE changes.

Invasive and Noninvasive Brain Stimulation in Parkinson's Disease: Clinical Effects and Future Perspectives.

In this review, we discuss the clinical and electrophysiological effects and the future directions of invasive and noninvasive brain stimulations in Parkinson's disease (PD). Deep brain stimulation (DBS) can improve motor symptoms in moderate to advanced PD. However, the optimal stimulation paradigm for nonmotor symptoms (NMS), freezing of gait, and the optimal timing of DBS are still under investigation. The findings of pathological oscillations and abnormal frequency to amplitude coupling provide models to develop adaptive DBS. Transcranial magnetic stimulation (TMS) revealed abnormal cortical excitability and plasticity in PD. Consecutive sessions of high-frequency, repetitive TMS on the motor cortex showed promising results. Paired TMS and DBS at specific times provided a novel way to investigate PD pathophysiology and have potential as a future treatment. Transcranial direct current stimulation or transcranial alternating current stimulation with multifocal electrodes or at specific phases of oscillation are also potential future strategies.

Changes of motor cortical excitability and response inhibition in patients with obsessive–compulsive disorder

Deficits in cortical inhibitory processes have been suggested as underlying pathophysiological mechanisms of obsessive–compulsive disorder (OCD). We examined whether patients with OCD have altered cortical excitability using paired-pulse transcranial magnetic stimulation (TMS). We also tested associations between TMS indices and OCD-related characteristics, including age of onset and response inhibition in the go/no-go paradigm, to examine whether altered cortical excitability contributes to symptom formation and behavioural inhibition deficit in patients with OCD. We assessed motor cortex excitability using paired-pulse TMS in 51 patients with OCD and 39 age-matched healthy controls. We also assessed clinical symptoms and response inhibition in the go/nogo task. All patients were undergoing treatment with serotonin reuptake inhibitors. We performed repeated-measures multivariate analysis of covariance to compare TMS indices between patients with OCD and controls. Compared to controls, patients with OCD showed a shorter cortical silent period and decreased intracortical facilitation. However, we found no significant difference between groups for resting motor threshold or short-interval intracortical inhibition. In the OCD group, the shortened cortical silent period was associated with a prompt reaction time in the go/no-go task and with early onset of OCD. We could not exclude the influence of medications on motor cortex excitability. These findings suggest abnormal cortical excitability in patients with OCD. The associations between cortical silent period and response inhibition and age of onset further indicate that altered cortical excitability may play an important role in the development of OCD.

Use of illicit amphetamines is associated with long-lasting changes in hand circuitry and control

ObjectiveThe study aim was to determine if use of illicit amphetamines or ecstasy is associated with abnormal excitability of the corticomotoneuronal pathway and manipulation of novel objects with the hand. MethodsThree groups of adults aged 18–50 years were investigated: individuals with a history of illicit amphetamine use, individuals with a history of ecstasy use but minimal use of other stimulants, and non-drug users. Transcranial magnetic stimulation was delivered to the motor cortex and the electromyographic response (motor evoked potential; MEP) was recorded from a contralateral hand muscle. Participants also gripped and lifted a novel experimental object consisting of two strain gauges and an accelerometer. ResultsResting MEP amplitude was larger in the amphetamine group (6M, 6F) than the non-drug and ecstasy groups (p < 0.005) in males but not females. Overestimation of grip force during manipulation of a novel object was observed in the amphetamine group (p = 0.020) but not the ecstasy group. ConclusionsHistory of illicit amphetamine use, in particular methamphetamine, is associated with abnormal motor cortical and/or corticomotoneuronal excitability in males and abnormal manipulation of novel objects in both males and females. SignificanceAbnormal excitability and hand function is evident months to years after cessation of illicit amphetamine use.

Electroencephalography in Pediatric Epilepsy

Surface electroencephalography (EEG) is a useful electrophysiological investigation for evaluating a paroxysmal event in children. It measures the electro potential difference between two points on the scalp. It is a non-invasive tool that analyzes neuronal maturation and abnormal cortical excitability. EEG helps in differentiating epileptic from non-epileptic clinical event and focal seizures from generalized seizure. This review is to discuss the rational use of interictal scalp EEG in diagnosis of epilepsy and different types of epilepsy syndromes in children. It further highlights its role in febrile seizure, first unprovoked seizure, status epilepticus and unexplained coma.