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S41: Neurophysiology of congenital mirror movements
Abstracts of Speakers / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
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anodal direct cortical stimulation, activates the corticospinal tract close to the axon hillock at the border between the grey and the white matter. DCS remains the most focal stimulation possible and thus is favorable used for tumor removal within the vicinity of the motor cortex. MEPs became focus of neurooncological strategies for optimized glioma resection. Combining DCS-MEPs and monopolar cortical/subcortical stimulation mapping techniques in supratentorial tumor surgery as well as combination with intraoperative imaging could achieve supramarginal resection. The proposed subcortical stimulation motor threshold of 2 mA for safe resection has to be confirmed with regard to tumor type and precise location of stimulation. As been shown in cerebral aneurysm surgery, the ability to detect pure motor hemiparesis in carotid endarterectomy was more recently shown in a multicenter study. In spine surgery, presence or disappearance (“all-or-nothing” principle) of MEP amplitude criteria is commonly accepted: the presence of any MEPs is related to unaffected motor function or transient paresis, with the exception of radiculopathy. In cervical and thoracic intramedullary spinal cord surgery, the additional implementation of the D-wave helps to distinguish between permanent and transient motor deficit: D-wave preservation is always followed by a recovery of motor function. The latter seems to be applicable in supratentorial surgeries alike. In summary, MEPs are specific and sensitive for the assessment of the motor cortex and the corticospinal tract. In supratentorial tumor surgery MEPs are increasingly becoming a tool for “functional” guided resection strategies.
The contribution of transcranial magnetic stimulation (TMS) and other non-invasive electrophysiological techniques to characterize the neural mechanisms underlying persistent congenital MM will be summarized. The neurophysiological hallmark of persistent congenital MM is the presence of fast-conducting corticospinal fibers connecting abnormally the hand area of the primary motor cortex (M1) with both sides of the spinal cord. This has been demonstrated by transcranial electric stimulation and TMS studies, showing that stimulation of one M1 elicits bilateral motor evoked potentials of normal latency in the resting hand muscles. Further insight into the origin of the ipsilateral corticospinal projection was provided by task-related modulation of short-interval intracortical inhibition (SICI). In two otherwise normal patients with persistent congenital MM, during intended unimanual contraction, SICI decreased in the “task” hand but was unchanged in the “mirror” hand compared to rest condition. This SICI dissociation strongly suggests that the ipsilateral pathway was not due to branching of crossed corticospinal neurons and supports the existence of a separate uncrossed projection. Moreover, in the same patients, interference with M1 function by focal TMS showed motor output from bilateral M1 during intended unimanual tasks. These data provide a rationale for rehabilitation aiming to reduce MM by favoring activation of crossed corticospinal neurons from the M1 contralateral to the voluntary task and uncrossed corticospinal neurons from the ipsilateral M1. Finally, altered interhemispheric inhibition and abnormal involvement of the supplementary motor area during both unimanual and bimanual movements has been recently found in 7 patients with congenital MM associated with mutations in the RAD51 gene.
S40 Intraoperative neurophysiological monitoring in pediatric neurosurgery: a focus on the sacral system
S42 Functional and effective connectivity in the developing brain
F. Sala 1 , G. Squintani 2 , V. Tramontano 2 , C. Arcaro 1 1 Institute of Neurosurgery, Verona, Italy; 2 Division of Neurology, Neurosciences, Verona, Italy Introduction: Intraoperative neurophysiologic monitoring (IOM) is nowadays extensively used in Pediatric Neurosurgery and tethered cord surgery is one of the most useful application. Our goal is to describe and discuss the standard IOM techniques used during tethered cord surgery, in the light of our clinical experience over the past ten years. Material and methods: Neurophysiological mapping of the conus-cauda is performed through direct stimulation of these structures and bilateral recording from segmental target muscles. While mapping identify ambiguous neural structures, their functional integrity during surgery can be assessed by monitoring techniques only, such as somatosensory evoked potentials (SEPs), transcranial motor evoked potentials (MEPs) from limb muscles and anal sphincters, and the bulbocavernosus reflex (BCR). Results: Between 2002 and 2012, we performed 48 surgical procedures in 47 patients with a tethered cord secondary to a variety of spinal dysraphisms. The monitorability rate was 84% for SEPs, 97% for limb muscle MEPs, 74% for the anal sphincter MEPs, and 59% for the BCR. In all patients but one SEP, MEP and BCR remained stable during surgery. Post-operatively two out of 47 patients presented a significant – though transient – neurological worsening. In six patients an unexpected muscle response was evoked by stimulating tissue macroscopically considered as not functional. Conclusions: Mapping techniques allow to identify and spare functional neural tissue and, vice-versa, to cut non-functional structures that may contribute to cord tethering. Monitoring techniques, MEP and BCR in particular, improve the reliability of intraoperative neurophysiology. IOM minimizes neurological morbidity in tethered cord surgery.
S41 Neurophysiology of congenital mirror movements M. Cincotta U.O. di Neurologia, Azienda Sanitaria di Firenze, Florence, Italy Mirror movements (MM) are unintended movements on one side of the body which are mirror reversals of the contralateral voluntary ones. MM can be seen in healthy children, whereas in adulthood, the persistence or the reappearance of strong and sustained MM is pathological. Persistent congenital MM can be seen in different conditions, ranging from absence of other abnormalities to severe congenital hemiparesis. Congenital MM not associated with other motor abnormalities may be sporadic or familial.
S. Maeaettae Kuopio university Hospital, University of eastern Finland, Clinical Neurophysiology, KYS, Finland Question: The EEG response to transcranial magnetic stimulation (TMS) is a new approach to characterize reactivity and connectivity of the brain. However, studies on children’s TMS-EEG responses are yet few. Method: We used navigated transcranial magnetic stimulation (nTMS) combined with high-density EEG on 30 healthy right-handed subjects (children, n=10, mean 10.5 yrs; adolescents, n=10, mean 16 yrs and adults, n=10, mean 26 yrs). nTMS was targeted to the primary motor cortex (optimal representation site of abductor pollicis brevis muscle) as well as to associative (frontal and parietal) brain regions. Results: The waveform, amplitude and distribution of TMS-evoked EEGresponses show developmental changes. The oscillatory activity evoked by TMS stimulation changes in strenght and duration with development. Conclusions: nTMS-EEG co-registration suits well for studying developmental changes in brain activation and connectivity.
S43 Functional and effective connectivity in epilepsy: overview and insight from TMS-EEG studies V.K. Kimiskidis Aristotle University of Thessaloniki, Laboratory of Clinical Neurophysiology, Thessaloniki, Greece The investigation of brain connectivity in epilepsy from multi-channel EEG, MEG or fMRI has attracted research interest in recent years. As a result of these studies, epilepsy is being increasingly envisaged as a connectivity dysfunction at the network level. Both scalp and intracranial EEG studies explored the dynamics of epileptiform activity primarily in focal epilepsies and revealed distinct changes in the network structure during the evolution of seizures. According to some evidence, synchronizability appears to be decreased during the ictal state but increases prior to seizure termination thereby challenging the traditional view of epilepsy as a purely hypersynchronous state. The advent of the combination of high density EEG with Transcranial Magnetic Stimulation (TMS-EEG) opened up new possibilities by allowing, for the first time in a non-invasive manner, the recording and mapping of neuronal responses induced by TMS at the cortical level (EEG reactivity) as well as the investigation and modulation of functional connectivity between brain areas. Recent studies suggest that TMS can induce short-lasting alterations in brain connectivity in a subset of epileptic patients that can possibly be used for diagnostic or prognostic purposes. In addition, trains of TMS stimuli applied during epileptiform discharges
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anodal direct cortical stimulation, activates the corticospinal tract close to the axon hillock at the border between the grey and the white matter. DCS remains the most focal stimulation possible and thus is favorable used for tumor removal within the vicinity of the motor cortex. MEPs became focus of neurooncological strategies for optimized glioma resection. Combining DCS-MEPs and monopolar cortical/subcortical stimulation mapping techniques in supratentorial tumor surgery as well as combination with intraoperative imaging could achieve supramarginal resection. The proposed subcortical stimulation motor threshold of 2 mA for safe resection has to be confirmed with regard to tumor type and precise location of stimulation. As been shown in cerebral aneurysm surgery, the ability to detect pure motor hemiparesis in carotid endarterectomy was more recently shown in a multicenter study. In spine surgery, presence or disappearance (“all-or-nothing” principle) of MEP amplitude criteria is commonly accepted: the presence of any MEPs is related to unaffected motor function or transient paresis, with the exception of radiculopathy. In cervical and thoracic intramedullary spinal cord surgery, the additional implementation of the D-wave helps to distinguish between permanent and transient motor deficit: D-wave preservation is always followed by a recovery of motor function. The latter seems to be applicable in supratentorial surgeries alike. In summary, MEPs are specific and sensitive for the assessment of the motor cortex and the corticospinal tract. In supratentorial tumor surgery MEPs are increasingly becoming a tool for “functional” guided resection strategies.
The contribution of transcranial magnetic stimulation (TMS) and other non-invasive electrophysiological techniques to characterize the neural mechanisms underlying persistent congenital MM will be summarized. The neurophysiological hallmark of persistent congenital MM is the presence of fast-conducting corticospinal fibers connecting abnormally the hand area of the primary motor cortex (M1) with both sides of the spinal cord. This has been demonstrated by transcranial electric stimulation and TMS studies, showing that stimulation of one M1 elicits bilateral motor evoked potentials of normal latency in the resting hand muscles. Further insight into the origin of the ipsilateral corticospinal projection was provided by task-related modulation of short-interval intracortical inhibition (SICI). In two otherwise normal patients with persistent congenital MM, during intended unimanual contraction, SICI decreased in the “task” hand but was unchanged in the “mirror” hand compared to rest condition. This SICI dissociation strongly suggests that the ipsilateral pathway was not due to branching of crossed corticospinal neurons and supports the existence of a separate uncrossed projection. Moreover, in the same patients, interference with M1 function by focal TMS showed motor output from bilateral M1 during intended unimanual tasks. These data provide a rationale for rehabilitation aiming to reduce MM by favoring activation of crossed corticospinal neurons from the M1 contralateral to the voluntary task and uncrossed corticospinal neurons from the ipsilateral M1. Finally, altered interhemispheric inhibition and abnormal involvement of the supplementary motor area during both unimanual and bimanual movements has been recently found in 7 patients with congenital MM associated with mutations in the RAD51 gene.
S40 Intraoperative neurophysiological monitoring in pediatric neurosurgery: a focus on the sacral system
S42 Functional and effective connectivity in the developing brain
F. Sala 1 , G. Squintani 2 , V. Tramontano 2 , C. Arcaro 1 1 Institute of Neurosurgery, Verona, Italy; 2 Division of Neurology, Neurosciences, Verona, Italy Introduction: Intraoperative neurophysiologic monitoring (IOM) is nowadays extensively used in Pediatric Neurosurgery and tethered cord surgery is one of the most useful application. Our goal is to describe and discuss the standard IOM techniques used during tethered cord surgery, in the light of our clinical experience over the past ten years. Material and methods: Neurophysiological mapping of the conus-cauda is performed through direct stimulation of these structures and bilateral recording from segmental target muscles. While mapping identify ambiguous neural structures, their functional integrity during surgery can be assessed by monitoring techniques only, such as somatosensory evoked potentials (SEPs), transcranial motor evoked potentials (MEPs) from limb muscles and anal sphincters, and the bulbocavernosus reflex (BCR). Results: Between 2002 and 2012, we performed 48 surgical procedures in 47 patients with a tethered cord secondary to a variety of spinal dysraphisms. The monitorability rate was 84% for SEPs, 97% for limb muscle MEPs, 74% for the anal sphincter MEPs, and 59% for the BCR. In all patients but one SEP, MEP and BCR remained stable during surgery. Post-operatively two out of 47 patients presented a significant – though transient – neurological worsening. In six patients an unexpected muscle response was evoked by stimulating tissue macroscopically considered as not functional. Conclusions: Mapping techniques allow to identify and spare functional neural tissue and, vice-versa, to cut non-functional structures that may contribute to cord tethering. Monitoring techniques, MEP and BCR in particular, improve the reliability of intraoperative neurophysiology. IOM minimizes neurological morbidity in tethered cord surgery.
S41 Neurophysiology of congenital mirror movements M. Cincotta U.O. di Neurologia, Azienda Sanitaria di Firenze, Florence, Italy Mirror movements (MM) are unintended movements on one side of the body which are mirror reversals of the contralateral voluntary ones. MM can be seen in healthy children, whereas in adulthood, the persistence or the reappearance of strong and sustained MM is pathological. Persistent congenital MM can be seen in different conditions, ranging from absence of other abnormalities to severe congenital hemiparesis. Congenital MM not associated with other motor abnormalities may be sporadic or familial.
S. Maeaettae Kuopio university Hospital, University of eastern Finland, Clinical Neurophysiology, KYS, Finland Question: The EEG response to transcranial magnetic stimulation (TMS) is a new approach to characterize reactivity and connectivity of the brain. However, studies on children’s TMS-EEG responses are yet few. Method: We used navigated transcranial magnetic stimulation (nTMS) combined with high-density EEG on 30 healthy right-handed subjects (children, n=10, mean 10.5 yrs; adolescents, n=10, mean 16 yrs and adults, n=10, mean 26 yrs). nTMS was targeted to the primary motor cortex (optimal representation site of abductor pollicis brevis muscle) as well as to associative (frontal and parietal) brain regions. Results: The waveform, amplitude and distribution of TMS-evoked EEGresponses show developmental changes. The oscillatory activity evoked by TMS stimulation changes in strenght and duration with development. Conclusions: nTMS-EEG co-registration suits well for studying developmental changes in brain activation and connectivity.
S43 Functional and effective connectivity in epilepsy: overview and insight from TMS-EEG studies V.K. Kimiskidis Aristotle University of Thessaloniki, Laboratory of Clinical Neurophysiology, Thessaloniki, Greece The investigation of brain connectivity in epilepsy from multi-channel EEG, MEG or fMRI has attracted research interest in recent years. As a result of these studies, epilepsy is being increasingly envisaged as a connectivity dysfunction at the network level. Both scalp and intracranial EEG studies explored the dynamics of epileptiform activity primarily in focal epilepsies and revealed distinct changes in the network structure during the evolution of seizures. According to some evidence, synchronizability appears to be decreased during the ictal state but increases prior to seizure termination thereby challenging the traditional view of epilepsy as a purely hypersynchronous state. The advent of the combination of high density EEG with Transcranial Magnetic Stimulation (TMS-EEG) opened up new possibilities by allowing, for the first time in a non-invasive manner, the recording and mapping of neuronal responses induced by TMS at the cortical level (EEG reactivity) as well as the investigation and modulation of functional connectivity between brain areas. Recent studies suggest that TMS can induce short-lasting alterations in brain connectivity in a subset of epileptic patients that can possibly be used for diagnostic or prognostic purposes. In addition, trains of TMS stimuli applied during epileptiform discharges