Cortical Amplitude Research Articles

Alterations of Spontaneous Cortical and Subcortical Activity in Type 2 Diabetes Mellitus with and without Depression

Introduction: Type 2 diabetes mellitus (T2DM) patients with depression have a higher risk of complications and mortality than T2DM without depression. However, the exact neuropathophysiological mechanism remains unclear. Consequently, the current study aimed to investigate the alteration of cortical and subcortical spontaneous neural activity in T2DM patients with and without depression. Methods: The demographic data, clinical variables, neuropsychological tests, and functional and anatomical magnetic resonance imaging of depressed T2DM (n = 47) of non-depressed T2DM (n = 59) and healthy controls (n = 41) were collected and evaluated. The correlation analysis, stepwise multiple linear regression, and receiver operating characteristic curve were performed for further analysis. Results: Abnormal neural activities in the bilateral posterior cingulate cortex (PCC) and hippocampus were observed in depressed and non-depressed T2DM and the right putamen of the depressed T2DM. Interestingly, the subcortical degree centrality (DC) of the right hippocampus and putamen were higher in depressed than non-depressed T2DM. Furthermore, the cortical amplitude of low-frequency fluctuation (ALFF) in PCC, subcortical DC in the putamen of depressed T2DM, and hippocampus of non-depressed T2DM was correlated with cognitive scores. In contrast, the cortical fractional ALFF in PCC of non-depressed T2DM was correlated with depression scores. Conclusions: The abnormalities of spontaneous cortical activity in PCC and subcortical activity in the hippocampus might represent the neurobiological feature of cerebral dysfunction in T2DM. Notably, the altered subcortical activity in the right putamen might mainly associate with negative emotion in T2DM, which could be a promising biomarker for recognizing early cerebral dysfunction in depressed T2DM. This study provided a novel insight into the neuropathophysiological mechanism of brain dysfunction in T2DM with and without depression.

Electrically evoked auditory cortical responses elicited from individually fitted stimulation parameters in cochlear implant users

Objective To investigate electrically evoked auditory cortical responses (eACR) elicited from the stimulation of intracochlear electrodes based on individually fitted stimulation parameters in cochlear implant (CI) users. Design An eACR setup based on individual fitting parameters is proposed. A 50-ms alternating biphasic pulse train was used to stimulate apical, medial, and basal electrodes and to evoke auditory cortical potentials (N1-P2 complex). Study sample The eACR setup proposed was validated with 14 adult CI users. Results Individual and grand-average eACR waveforms were obtained. The eACR amplitudes were lower in the basal than in the apical and medial regions. Earlier N1 latencies were found in CI users with lower maximum comfortable loudness levels and shorter phase duration in response to apical stimulation, while medial and basal stimulation resulted in earlier N1 latencies and larger N1-P2 amplitudes in users with longer CI experience. Conclusions eACR could be elicited by direct intracochlear stimulation using individual fitting parameters with a success rate of 71%. The highest cortical peak-to-peak amplitudes were obtained in response to apical stimulation. Unlike the P2, the N1 component appeared to be a consistent cortical potential to determine eACR and gain knowledge of the auditory processing beyond the cochlea in CI users. Highlights eACR can be elicited through direct stimulation of intracochlear electrodes. Stimulation of apical and medial regions yielded the highest N1-P2 amplitudes. CI users with lower maximum comfortable loudness levels had shorter N1 latencies during apical stimulation. The present dataset of mainly well-performing CI users suggests better cortical processing, that is, higher amplitudes and shorter latencies of N1. The N1 potential appears a more consistent and reliable potential than the P2 to determine eACR responses in CI users.

Free-Field Cortical Steady-State Evoked Potentials in Cochlear Implant Users

Auditory steady-state evoked potentials (SS-EPs) are phase-locked neural responses to periodic stimuli, believed to reflect specific neural generators. As an objective measure, steady-state responses have been used in different clinical settings, including measuring hearing thresholds of normal and hearing-impaired subjects. Recent studies are in favor of recording these responses as a part of the cochlear implant (CI) device-fitting procedure. Considering these potential benefits, the goals of the present study were to assess the feasibility of recording free-field SS-EPs in CI users and to compare their characteristics between CI users and controls. By taking advantage of a recently developed dual-frequency tagging method, we attempted to record subcortical and cortical SS-EPs from adult CI users and controls and measured reliable subcortical and cortical SS-EPs in the control group. Independent component analysis (ICA) was used to remove CI stimulation artifacts, yet subcortical responses of several CIs were heavily contaminated by these artifacts. Consequently, only cortical SS-EPs were compared between groups, which were found to be larger in the controls. The lower cortical SS-EPs' amplitude in CI users might indicate a reduction in neural synchrony evoked by the modulation rate of the auditory input across different neural assemblies in the auditory pathway. The brain topographies of cortical auditory SS-EPs, the time course of cortical responses, and the reconstructed cortical maps were highly similar between groups, confirming their neural origin and possibility to obtain such responses also in CI recipients. As for subcortical SS-EPs, our results highlight a need for sophisticated denoising algorithms to pinpoint and remove artifactual components from the biological response.

Resting-State Phase-Amplitude Coupling Between the Human Subthalamic Nucleus and Cortical Activity: A Simultaneous Intracranial and Scalp EEG Study.

It has been suggested that slow oscillations in the subthalamic nucleus (STN) reflect top-down inputs from the medial prefrontal cortex, thus implementing behavior control. It is unclear, however, whether the STN oscillations are related to cortical activity in a bottom-up manner. To assess resting-state subcortico-cortical interactions, we recorded simultaneous scalp electroencephalographic activity and local field potentials in the STN (LFP-STN) in 11 patients with Parkinson's disease implanted with deep brain stimulation electrodes in the on-medication state during rest. We assessed the cross-structural phase-amplitude coupling (PAC) between the STN and cortical activity within a wide frequency range of 1 to 100Hz. The PAC was dominant between the δ/θ STN phase and β/γ cortical amplitude in most investigated scalp regions and between the δ cortical phase and θ/α STN amplitude in the frontal and temporal regions. The cross-frequency linkage between the slow oscillations of the LFP-STN activity and the amplitude of the scalp-recorded cortical activity at rest was demonstrated, and similar involvement of the left and right STNs in the coupling was observed. Our results suggest that the STN plays a role in both bottom-up and top-down processes within the subcortico-cortical circuitries of the human brain during the resting state. A relative left-right symmetry in the STN-cortex functional linkage was suggested. Practical treatment studies would be necessary to assess whether unilateral stimulation of the STN might be sufficient for treatment of Parkinson's disease.

The Effects of Midline Cerebellar rTMS on Human Pharyngeal Cortical Activity in the Intact Swallowing Motor System

We sought to compare the effects of 10 Hz cerebellar vermis (vs. unilateral hemispheric and sham) repetitive transcranial magnetic stimulation (rTMS) on cortical neuroelectrical activity and thereafter 10 Hz cerebellar vermis (vs. sham) rTMS on swallowing behaviour. Healthy participants (n = 25) were randomly allocated to receive vermis, unilateral hemisphere or sham 10 Hz cerebellar rTMS. Recordings were made using pharyngeal electromyography and manometry catheters, obtaining motor-evoked potentials (MEPs) and pressure recordings. The amplitudes of MEPs elicited using single-pulse TMS delivered to the pharyngeal areas of the motor cortex bilaterally were measured pre- and post-cerebellar stimulation. As in previous studies, abductor policis brevis (APB) MEPs were measured to assess post-rTMS modulation specificity. Swallowing was assessed using a swallowing accuracy task. Measurements were made at baseline and 15-min intervals for an hour post-intervention. Measurements involved TMS being used to elicit 10 MEPs bilaterally over the pharyngeal areas of the motor cortex, over the APB cortical representation adjacent to the pharyngeal area with the lowest resting motor threshold and 5 MEPs bilaterally over pharyngeal areas of the cerebellar hemispheres. Swallowing accuracy was assessed by giving participants 10 attempts to swallow and hit a digital target. Cerebellar vermis rTMS caused significant suppression of cortical pharyngeal MEP amplitudes compared with unilateral rTMS and sham (P = 0.0005, 0.002). APB and cerebellar MEP amplitudes were unaffected as were pharyngeal and APB MEP latencies. Following cerebellar vermis rTMS there was a significant reduction in swallowing accuracy compared with sham (P = 0.001). Our findings demonstrate cerebellar vermis rTMS exerts a suppressive effect on pharyngeal motor cortical activity and swallowing behaviour.

Intact Auditory Cortical Cross-Frequency Coupling in Early and Chronic Schizophrenia

Background Previous work has identified a hierarchical organization of neural oscillations that supports performance of complex cognitive and perceptual tasks, and can be indexed with phase-amplitude coupling (PAC) between low- and high-frequency oscillations. Our aim was to employ enhanced source localization afforded by magnetoencephalography (MEG) to expand on earlier reports of intact auditory cortical PAC in schizophrenia and to investigate how PAC may evolve over the early and chronic phases of the illness. Methods Individuals with early schizophrenia (n=12) (≤5 years of illness duration), chronic schizophrenia (n=16) (>5 years of illness duration) and healthy comparators (n = 17) performed the auditory steady state response (ASSR) to 40, 30, and 20 Hz stimuli during MEG recordings. We estimated amplitude and PAC on the MEG ASSR source localized to the auditory cortices. Results Gamma amplitude during 40-Hz ASSR exhibited a significant group by hemisphere interaction, with both patient groups showing reduced right hemisphere amplitude and no overall lateralization in contrast to the right hemisphere lateralization demonstrated in controls. We found significant PAC in the right auditory cortex during the 40-Hz entrainment condition relative to baseline, however, PAC did not differ significantly between groups. Conclusions In the current study, we demonstrated an apparent sparing of ASSR-related PAC across phases of the illness, in contrast with impaired cortical gamma oscillation amplitudes. The distinction between our PAC and evoked ASSR findings supports the notion of separate but interacting circuits for the generation and maintenance of sensory gamma oscillations. The apparent sparing of PAC in both early and chronic schizophrenia patients could imply that the neuropathology of schizophrenia differentially affects these mechanisms across different stages of the disease. Future studies should investigate the distinction between PAC during passive tasks and more cognitively demanding task such as working memory so that we can begin to understand the influence of schizophrenia neuropathology on the larger framework for modulating neurocomputational capacity.

Scoliosis in chronic neuronopathic Gaucher disease: Characterization in the treatment era

Intraoperative monitoring (IOM) using somatosensory-evoked potentials (SSEPs) plays an important role in reducing iatrogenic neurologic deficits during corrective pediatric idiopathic procedures for scoliosis. However, for unknown reasons, recent reports have cited that the sensitivity of SSEPs to detect neurologic deficits has decreased, in some to be less than 50%. This current trend, which is coincident with the addition of transcranial motor-evoked potentials, is surprising given that SSEPs are robust, reproducible responses that were previously shown to have sensitivity and specificity of >90%.Our primary aim was to assess whether SSEPs alone can detect impending neurologic deficits with similar sensitivity and specificity as originally reported. Our secondary aim was to estimate the potential predictive value of adding transcranial motor-evoked potentials to SSEP monitoring in idiopathic scoliosis procedures.This was a retrospective review to analyze the efficacy of SSEP monitoring in the group of pediatric instrumented scoliosis fusion cases.We retrospectively reviewed all consecutive cases of patients who underwent idiopathic scoliosis surgery between 1999 and 2009 at Children’s Hospital of Pittsburgh. We identified 477 patients who had the surgery with SSEP monitoring alone. Exclusion criteria included any patients with neuromuscular disorders or unreliable SSEP monitoring. Patients who had incomplete neurophysiology data or incomplete postoperative records were also excluded.Major outcomes measured were clinically significant postoperative sensory or motor deficits, as well as significant intraoperative SSEP changes.Continuous interleaved upper- and lower-extremity SSEPs were obtained throughout the duration of all procedures. We considered a persistent 50% reduction in primary somatosensory cortical amplitude or a prolongation of response latency by >10% from baseline to be significant. Persistent changes represent significant deviation in SSEP amplitude or latency in more than two consecutive averaged trials. Patients were classified into one of four categories with respect to SSEP monitoring: true positive, false positive, true negative, and false negative. The sensitivity, specificity, positive predictive value, and negative predictive value were then calculated accordingly.Our review of 477 idiopathic scoliosis surgeries monitored using SSEPs alone revealed a new deficit rate of 0.63% with no cases of permanent injury. Sensitivity = 95.0%, specificity = 99.8%, positive predictive value = 95%, negative predictive value = 99.8%. Using evidence-based epidemiologic measures, we calculated that the number needed to treat was 1,587 patients for one intervention to be performed that would have been missed by SSEP monitoring alone. In addition, the number needed to harm, which represents the increase in false positives with the addition of transcranial electrical motor-evoked potentials, was 200.SSEP monitoring alone during idiopathic scoliosis continues to be a highly reliable method for the detection and prevention of iatrogenic injury. Our results confirm the high sensitivity and specificity of SSEP monitoring alone published in earlier literature. As such, we suggest the continued use of SSEP alone in idiopathic scoliosis surgeries. At this time we do not believe there are sufficient data to support the addition of MEP monitoring, although more studies and revised criteria for the use of MEP may provide added value for its use in the future.

Action Observation and Execution Differentially Modulate Basal Ganglia-Cortical Activity in Humans

Abstract INTRODUCTION To understand an observed action, without overt execution, the observer is thought to run similar motor plans; indicating a strong coupling between the neural representation of action observation and execution. Imaging studies show activation of basal ganglia (BG) and motor cortex during movement yet comparative studies using direct and invasive human recordings are sparse. We aimed to characterize how movement execution and observation differentially modulate local and inter-regional activity across BG and sensorimotor cortex. METHODS We recorded LFP from globus palidus internus (GPi) and electrocorticography from ipsilateral sensorimotor cortex in 9 PD subjects during deep brain stimulation surgery. Subjects performed block design tasks alternating between 30 s of rest and performing or observing finger tapping with random order. We assessed changes in spectral power, along with pallidocortical coherence and cortical PAC. RESULTS We observed suppression of alpha-beta (9-25 Hz) power in contralateral GPi and sensorimotor cortex during both activities. This power suppression was significantly weaker in the motor cortex during the action observation compared to the execution (P = .02). However pallidal spectral changes in alpha-beta frequencies were not different across tasks (P = .3). Uniquely during the action execution, there was a significant increase in the gamma power (80-200 Hz) at the motor cortex (P < .05). In addition, Pallidocortical beta coherence, and motor cortical beta-gamma PAC were significantly suppressed during action execution (P < .05) and not the observation. CONCLUSION Our results support the functional dissociation within the BG-cortical network during action observation and execution. Although spectral power changes in a-ß in the BG are largely similar across tasks, suppression of BG-cortical functional connectivity is a feature of movement execution. In addition, increase in the cortical gamma power and beta-gamma phase amplitude decoupling only happen during the movement execution, in line with the theory that during movement execution the gamma signal is released from the constraint of beta.

Wavelet-Based Muscle Artefact Noise Reduction for Short Latency rTMS Evoked Potentials.

This paper presents a new method of reducing the noise in the EEG response signal recorded during repetitive transcranial magnetic stimulation (rTMS). This noise is principally composed of the residual stimulus artefact and millivolt amplitude compound muscle action potentials (CMAP) recorded from the scalp muscles and precludes analysis of the cortical evoked potentials, especially during the first 20-ms post stimulus. The proposed method uses the wavelet transform with a fourth-order Daubechies mother wavelet and a novel coefficient reduction algorithm based on cortical amplitude thresholds. Four other mother wavelets as well as digital filtering have been tested, and the Coiflets 2 and 3 also found to be effective with Coiflet 3 results marginally better than Daubechies 4. The approach has been tested using data recorded from 16 normal subjects during a study of cortical sensitivity to rTMS at different cortical locations using stimulation amplitudes, frequencies, and sites typically used in clinical practice to treat major depressive disorder.

Distinction of self-produced touch and social touch at cortical and spinal cord levels.

Differentiation between self-produced tactile stimuli and touch by others is necessary for social interactions and for a coherent concept of "self." The mechanisms underlying this distinction are unknown. Here, we investigated the distinction between self- and other-produced light touch in healthy volunteers using three different approaches: fMRI, behavioral testing, and somatosensory-evoked potentials (SEPs) at spinal and cortical levels. Using fMRI, we found self-other differentiation in somatosensory and sociocognitive areas. Other-touch was related to activation in several areas, including somatosensory cortex, insula, superior temporal gyrus, supramarginal gyrus, striatum, amygdala, cerebellum, and prefrontal cortex. During self-touch, we instead found deactivation in insula, anterior cingulate cortex, superior temporal gyrus, amygdala, parahippocampal gyrus, and prefrontal areas. Deactivation extended into brain areas encoding low-level sensory representations, including thalamus and brainstem. These findings were replicated in a second cohort. During self-touch, the sensorimotor cortex was functionally connected to the insula, and the threshold for detection of an additional tactile stimulus was elevated. Differential encoding of self- vs. other-touch during fMRI correlated with the individual self-concept strength. In SEP, cortical amplitudes were reduced during self-touch, while latencies at cortical and spinal levels were faster for other-touch. We thus demonstrated a robust self-other distinction in brain areas related to somatosensory, social cognitive, and interoceptive processing. Signs of this distinction were evident at the spinal cord. Our results provide a framework for future studies in autism, schizophrenia, and emotionally unstable personality disorder, conditions where symptoms include social touch avoidance and poor self-vs.-other discrimination.

F108. The prognostic value of median nerve SSEP after cardiac arrest: Evaluation of severity of hypoxic-ischemic encephalopathy by brain autopsies

Introduction The severity of hypoxic-ischemic encephalopathy (HIE) strongly determines outcome after cardiac arrest (CA). Bilaterally absent cortical median nerve somatosensory evoked potentials (SSEPs) have been shown to accurately predict poor prognosis. However, self-fulfilling prophecy due to withdrawal of life-sustaining therapy is an important bias in prognostication studies on CA patients. Brain autopsies in patients who died after CA provide a unique opportunity to verify prognostic parameters such as SSEPs. Methods We retrospectively identified CA patients from university hospitals in Berlin, Germany, Lund, Sweden and Arhus, Denmark, who died after initially successful resuscitation and for whom SSEPs for neuro-prognostication and brain autopsy were available. We blindly determined presence/absence and, if applicable, cortical peak-to-peak SSEP amplitudes from original recordings. Severity of HIE was quantified histopathologically according to the selective eosinophilic neuronal death (SEND) score. Results We identified 58 CA autopsy patients who had been investigated with SSEP. All 21 patients with bilaterally absent SSEP and all 5 with cortical SSEP amplitudes below 0.5 μV had severe HIE (SEND 2–4 in cortical regions). The highest cortical SSEP amplitude in a patient with severe HIE was 2.7 μV, all 11 patients with higher amplitudes had no/moderate HIE (SEND 0–1 in cortical regions). Conclusion We did not find evidence for a self-fulfilling prophecy in the prediction of poor neurological outcome by SSEP after cardiac arrest. Bilaterally absent cortical SSEP and very low SSEP amplitudes indicated histopathologically severe HIE whereas cortical SSEP amplitudes above 2.7 μV indicated absence of severe HIE.

S117. Intraoperative detection of posterior circulation transient ischemic attack: Single case study

Introduction Intraoperative Neuromonitoring (IONM) has been utilized to aid in the prevention of iatrogenic injury. Studies have described the role IONM may play in predicting post procedural neurological deficits (PPNDs). Here we discuss a unique case study of a patient who underwent stent-assisted embolization of a large basilar tip aneurysm with very specific localizing changes observed by analysis of somatosensory evoked potentials (SSEPs), electroencephalography (EEG), and brainstem auditory evoked potentials (BAEPs). Methods A 66 year old female with past medical history of hypertension and hyperlipidemia presented to the emergency department (ED) with photophobia and a left dilated pupil. MR angiography revealed a large basilar tip aneurysm. Aspirin and Plavix were administered and a stent-assisted coil embolization was performed with complete resolution of symptoms. Follow-up elective repair of the aneurysm was scheduled. Prior to the follow-up elective repair, the patient presented to the ED once again with a new onset headache and anisocoria. MR angiogram was performed which revealed no acute changes. The patient was admitted and underwent further embolization of the aneurysm from the left P1 into the basilar apex. The initial stent was deployed with no complications. During advancement of a second stent, abrupt cortical amplitude decreases of 76% and 79% in the left upper and lower extremity traces, respectively, were observed. All other traces remained stable. Catheter placement was inspected and noted as normal. Signals began to improve and returned to baseline in less than 10 min as the procedure was completed without placement of an additional stent. Results Six days post-operatively, the patient presented to an outside ED complaining of posterior headache and left-sided paresthesia in the trigeminal nerve distribution. She was transferred to the University of Michigan for further evaluation. MR imaging was unremarkable but further workup revealed sub-therapeutic Plavix levels so her dose was increased. Her symptoms resolved within 24 h. Conclusion We hypothesize that both intraoperative electrophysiological changes and PPNDs reflect a specific ischemic event in the P1/P2 deep perforator distribution affecting the right ventral posterolateral and posteromedial nuclei of the thalamus, respectively. This case highlights the potential anatomic specificity of multimodal IONM by the changes seen at the time of manipulation of the perforating branches of the posterior circulation, correlating with subsequent TIA and symptoms attributable to the same vascular distribution. This interpretation must be taken with caution as this does not establish a direct correlation of IONM changes with subsequent TIA. Potential correlation should be studied in a larger population undergoing endovascular intervention in the posterior circulation.

P222 Diagnostic and therapeutic possibilities of transcranial magnetic stimulation in patients after traumatic brain injury

Objectives Recovery of both mental and motor functions is one of the key problems of neurorehabilitation of patients with traumatic brain injury (TBI), accompanied by posttraumatic unconsciousness state (PUS). The purpose of pilot study is to clarify the diagnostic and therapeutic potential of TMS in patients after TBI with impaired motor activity and consciousness. Methods Observation groups: (1) 15 patients after TBI at the age of 17–56, in which the diagnostic TMS (cortical motor areas (M1) bilaterally, CVII bilaterally, registration of MEPs from musculus abductor pollicis brevis) was performed; (2) 9 patients after TBI at the age of 16–44 with a prolonged (from 60 to 220 days) unconscious state in which the rhythmic TMS was performed; (3) Control group: 5 healthy men aged 22–28. Diagnostic TMS evaluated cortical, radicular latency and amplitude of MEPs,time of central motor conduction. In the second and third groups changes of neurological status, indicators of the memory and attention, and N100, N200 and P300 components of auditory ERP hour before and hour after stimulation were estimated. Results Diagnostic TMS in patients with positive or ambiguous clinical dynamics showed initial difference of conductivity of tracts in comparison with normal data by 20–30% or 30–40%, respectively, with progressive improvement as motor and cognitive functions recovered. In patients with negative clinical dynamics TMS values had significantly larger deviation of cortical latency and amplitudes of MEPs (over 45%), and also the time of central motor conduction. Statistical analysis of acquired data revealed the greatest prognostic significance for determining the level of the amplitudes of MEPs with undeniable importance for the indicators of cortical latency and the time of central motor conduction. Therapeutic TMS of the sagittal premotor cortex areas in groups 2 and 3 concurred with improvement of any attention and normalization of amplitude and latency of all ERP components, as well as indicators of their spatial synchronism, especially for P300. Conclusions The obtained data clarifies diagnostic parameters of TMS and proposes the availability of using rTMS for therapeutic purposes in patients with PUS. Supported by RFFI N16-29-08304 .

Age-related dynamics of the parameters of somatosensory evoked potentials in healthy children

The purpose of this study was to evaluate the parameters of somatosensory evoked potentials (SSEPs) in healthy children of different age groups (n = 94). The amplitudes of the main cortical peaks and the central sensory conduction time (CSCT) from n. medianus and n. tibialis in children aged under 12 months, 1–12 years, and 12–17 years were estimated and compared. No significant cortical peaks were recorded from the tibial nerve in five children younger than 1 year (5 out of 23, 22%). Significant differences in CSCT were observed between the children younger than 1 year and two other groups. The amplitudes did not significantly differ between the groups. Thus, SSEPs may be used for the evaluation of somatosensory pathways in children aged one month to 17 years. CSCT differs significantly between children younger than 1 year and other age groups. Age-related reduction in CSCT and elevation of the cortical peak amplitudes may reflect the myelination of somatosensory pathways and the improvement in nervous system integration.

Effect of forward Head Posture on Sensorimotor Integration

Background: Forward head posture (FHP) is a common type of postural distortion seen clinically, whereby an anterior shift of the head position occurs. Ideal posture is considered to be present when the external auditory meatus is aligned with the vertical line. There were different assessment methods of FHP and the measurement of craniovertebral (CV) angle considered as the most common assessment methods of FHP, The smaller the angle, the greater the FHP. Muscle strain considered as one of the complications of FHP, repetitive strain of the muscle lead to a change in the way of the brain processes the incoming sensory information and subsequent motor output to muscles, a process known as sensorimotor integration(SMI). This study was conducted to measure the neurophysiological effect of FHP on SMI. Methods: Sixty volunteers participated in the study,30 normal subjects with CV angle≥49 are in group A (Normal), 30 forward head subjects with CV angle ≤49 are in group B (forward head). The amplitude of Cortical Somatosensory evoked potential (SSEPs) of N30-P22, N20-P25 and N24-P22 N30 complex (N30-P22), N20 complex (N20-P25) and N24 complex(N24-P22) of SEPS were recorded for both groups after stimulation of the right median nerve. Results: There was a significant increase in the cortical amplitude of N30-P22, N20-P25 and N24-P22 of SEPS in the group (A) compared with a group (B) as p-value was ≤ 0.05. Conclusion: forward head posture affects SMI through changing the response of CNS to afferent input, as demonstrated by attenuation of cortical STEPS in the group (B) compared with a group (A).

MRI AND EVOKED POTENTTIALS IN DIFFERENTIAL DIAGNOSIS OF ENCEPHALITIS, DISSEMINATED ENCEPHALOMYELITIS AND MULTIPLE SCLEROSIS IN CHILDREN

Last years are characterized by the growth of encephalitis (Ef) frequency and demyelination diseases of CNS in children, especially, among teenagers. The diseases are characterized by similar of clinical features of the disease onset, absence of differential diagnostical criteria and frequency of the disease chronisation and possibility of transformation in multiple sclerosis (MS), all this determines the problem of differential diagnosis. The aim is to determine differential-diagnostical features of Ef, disseminated encephalomyelitis (DEM) and MS in children by analysis of structure MRI and brain multi-modal evoked potentials (MEP). We observed 35 children with Ef, 40 with DEM and 40 with MS. All patients were from 3 to 17 years old. All patients were diagnosed clinically in acute period and in catamnesis — after 3 and 6 months. MS diagnosis was based on McDonald criteria, 2010 year. ADEM diagnosis was also based on international criteria. We analyzed brain MRI, spinal MRI and MEP in all patients during the first day of hospitalization and after 3 and 6 months later. The analysis of the MRI of the brain and spinal cord in encephalitis (EF, n=35), disseminated encephalomyelitis (ADEM, n=60) and multiple sclerosis (MS, n=60) of children on admission to hospital, and then — after 3 and 6 months. Up to 85% of foci with ADEM and EF had irregular shapes, accompanied by swelling phenomena, and mass effect and in 2⁄3 cases were localized in the gray or white and gray matter of the CNS. In 60% of cases in patients with EF and ADEM based on the localization of foci could suggest the etiology of the disease. In MS 67,5% were detected multifocal white matter lesions (more than 10 lesions), and most of the foci had a size of up to 1 cm and the correct round-oval and the absence of signs of inflammation. The presence of lesions in the gray matter at EF, ADEM and MS respectively observed in 82,5%, 40% and 7,5% of cases. After 3–6 months of MRI in the majority of EF and DEM foci regressed, and in MS were reduced in size, but not completely disappeared. According to the study of evoked potentials (EP) of the brain in children with MS and ADEM often increased latency of the responses, while the EF decreased cortical or brainstem response amplitude. The majority of patients with MS have changed the parameters both 3–4 different EP (somatosensory from the upper and lower limbs, acoustic stem and/or visual), while ADEM and EF-1–2 evoked potentials. Chronic EF, and the progression of neurological symptoms was not associated with the advent of the «new» lesion, and up to 75% of the foci can regress completely after 3–6 months. Chronic EF characterized by increase of only brain atrophy, which involves communication of these changes only with neuronal process. Whereas in MS and multiphase ADEM appeared «new» foci accumulating contrast agent that allows you to talk about preserving the pathogenesis of vascular component in their progression. Study of MEP and MRI in children with Ef, DEM and MS in dynamics can be useful for differential diagnosis and monitoring of therapy efficacy.

Comparison of Subdermal Needle and Surface Adhesive Stimulating Electrodes for Somatosensory Evoked Potential Monitoring during Anterior Cervical Discectomy and Fusion

ABSTRACTIntroduction: Needle stick injuries remain a physical and psychological burden to healthcare workers. Noninvasive surface adhesive stimulating electrodes used to generate somatosensory evoked potentials can help decrease this risk.Methods: We performed a retrospective observational study of patients who underwent anterior cervical discectomy and fusion (ACDF) surgery to determine the utility and variability of using surface adhesive stimulating electrodes. Our analysis for utility compared alarm (significant changes) frequency, defined by established alarm criteria, between subdermal needle (Group I) and surface adhesive electrodes (Group II). We compared the variability by comparing the frequency of alarms based on establishing baselines during various stages of the procedure.Results: Between Group I and Group II, no significant differences were found in demographic, age, number of levels decompressed and fused, and length of surgery variability. However, stimulation intensity was significantly higher in Group II. Significant differences in the mean frequency of alarm of cortical, subcortical, and Erb’s somatosensory evoked potential (SSEP) responses for the upper extremities between the two groups were only observed for the upper left Erb’s point amplitude (p = 0.03) at retraction and upper right cortical amplitude at incision (p = 0.02).The frequency of alarms of the amplitude of left ulnar cortical responses from SSEPs using surface adhesives when baselines were established at the beginning of the procedure, at the time of incision, and at placement of retractors were 13.83 % (±14.08%), 7.50 % (±7.56%) and 3.42 % (±3.48%), respectively. Comparatively, the frequencies of alarms of the amplitude of left ulnar cortical responses from SSEPs using needle electrodes were 18.07 % (±22.85%), 12.13 % (±17.30%) and 7.37 % (±11.82%), respectively. Similar results were observed from frequency for alarms from the right ulnar SSEPs.Conclusion: This study found little significant difference between the frequencies of alarm in patients who had SSEP responses obtained using surface adhesive electrodes when compared to needle electrodes. This lack of significant difference was observed even when alarms were established at various stages of the surgery before any major manipulation. For short procedures monitoring the upper extremities only, surface adhesive electrodes may provide a reliable alternative to invasive needle electrodes.

ID 212 – Neuromagnetic evidence of reduced functional connectivity of cortical somatosensory network in patients with writer‘s cramp

Objective The involvement of motor cortex and sensorimotor integration in patients with writer’s cramp (WC) has been well documented. However, the exact neurophysiological profile within the somatosensory system, including primary somatosensory cortex (SI), contralateral (SIIc) and ipsilateral (SIIi) secondary somatosensory areas remains ambiguous. Methods This study investigated the neuromagnetic cortical activities of median nerve stimulation in 10 patients with WC and 10 healthy controls (HC). To explore all the aspects of somatosensory functioning, our data were analyzed with the minimum norm estimate (MNE), time–frequency approach with evoked and induced activities, and cortical coherence between SI and SIIc (SI–SIIc), SI and SIIi (SI–SIIi), and SIIc and SIIi (SIIc–SIIi) from theta to gamma oscillations. Results No significant between-group differences were found in the MNE cortical amplitudes of SI, SIIc, and SIIi. Powers of evoked gamma oscillation and induced beta synchronization were also equivalent between WC and HC. Notably, we found significantly reduced theta coherence of SI-SIIi, alpha coherence of SI-SIIi and SIIc-SIIi, and beta coherence of SIIc–SIIi. Moreover, a longer duration of illness was strongly associated with a less SI-SIIi beta coherence. Conclusions Our results suggest the involvement of somatosensory abnormalities, primarily with the form of functional connectivity, in patients with WC.

Reduced functional connectivity of somatosensory network in writer's cramp patients.

BackgroundThe involvement of motor cortex and sensorimotor integration in patients with writer's cramp (WC) has been well documented. However, the exact neurophysiological profile within the somatosensory system, including primary somatosensory cortex (SI), contralateral (SIIc), and ipsilateral (SIIi) secondary somatosensory areas remains less understood.MethodsThis study investigated the neuromagnetic cortical activities of median nerve stimulation in 10 patients with WC and 10 healthy controls (HC). To comprehensively explore all the aspects of somatosensory functioning, we analyzed our data with the minimum norm estimate (MNE), the time‐frequency approach with evoked and induced activities, and functional connectivity between SI and SIIc (SI–SIIc), SI and SIIi (SI–SIIi), and SIIc and SIIi (SIIc–SIIi) from theta to gamma oscillations.ResultsNo significant between‐group differences were found in the MNE cortical amplitudes of SI, SIIc, and SIIi. Power strengths of evoked gamma oscillation and induced beta synchronization were also equivalent between WC and HC groups. However, we found significantly reduced theta coherence of SI–SIIi, alpha coherence of SI–SIIi and SIIc–SIIi, as well as beta coherence of SIIc–SIIi in patients with WC.ConclusionOur results suggest the involvement of somatosensory abnormalities, primarily with the form of functional connectivity, in patients with WC.

A Review of Transcranial Magnetic Stimulation and Multimodal Neuroimaging to Characterize Post-Stroke Neuroplasticity.

Following stroke, the brain undergoes various stages of recovery where the central nervous system can reorganize neural circuitry (neuroplasticity) both spontaneously and with the aid of behavioral rehabilitation and non-invasive brain stimulation. Multiple neuroimaging techniques can characterize common structural and functional stroke-related deficits, and importantly, help predict recovery of function. Diffusion tensor imaging (DTI) typically reveals increased overall diffusivity throughout the brain following stroke, and is capable of indexing the extent of white matter damage. Magnetic resonance spectroscopy (MRS) provides an index of metabolic changes in surviving neural tissue after stroke, serving as a marker of brain function. The neural correlates of altered brain activity after stroke have been demonstrated by abnormal activation of sensorimotor cortices during task performance, and at rest, using functional magnetic resonance imaging (fMRI). Electroencephalography (EEG) has been used to characterize motor dysfunction in terms of increased cortical amplitude in the sensorimotor regions when performing upper limb movement, indicating abnormally increased cognitive effort and planning in individuals with stroke. Transcranial magnetic stimulation (TMS) work reveals changes in ipsilesional and contralesional cortical excitability in the sensorimotor cortices. The severity of motor deficits indexed using TMS has been linked to the magnitude of activity imbalance between the sensorimotor cortices. In this paper, we will provide a narrative review of data from studies utilizing DTI, MRS, fMRI, EEG, and brain stimulation techniques focusing on TMS and its combination with uni- and multimodal neuroimaging methods to assess recovery after stroke. Approaches that delineate the best measures with which to predict or positively alter outcomes will be highlighted.