Pathophysiology of unilateral asterixis due to thalamic lesion.

[Objective]:Unilateral asterixis has been reported in patients with thalamic lesion. This study aims at elucidating the pathophysiology of the thalamic asterixis. [Methods]:Two cases with unilateral asterixis caused by an infarction in the lateral thalamus were studied by analysing the asterixis-related cortical activities, transcranial magnetic stimulation (TMS) for motor cortex excitability and probabilistic diffusion tractography for the thalamo-cortical connectivity. [Results]:Averaging of electroencephalogram (EEG) time-locked to the asterixis revealed rhythmic oscillations of a beta band at the central area contralateral to the affected hand. TMS revealed a decrease in the motor evoked potential (MEP) amplitude and a prolongation of the silent period (SP). The anatomical mapping of connections between the thalamus and cortical areas using a diffusion-weighted image (DWI) showed that the lateral thalamus involved by the infarction was connected to the premotor cortex, the primary motor cortex (M1) and the primary somatosensory cortex (S1) of the corresponding hemisphere. [Conclusions]:The thalamic asterixis is mediated by the sensorimotor cortex, which is subjected to excessive inhibition as a result of the thalamic lesion involving the ventral lateral nucleus. [Significance]:This is the first demonstration of participation of the sensorimotor cortex in the generation of asterixis due to the lateral thalamic lesion

Neural Sources of Vagus Nerve Stimulation–Induced Slow Cortical Potentials

[Objectives] This study investigated neuronal sources of slow cortical potentials (SCPs) evoked during vagus nerve stimulation (VNS) in patients with epilepsy who underwent routine electroencephalography (EEG) after implantation of the device. [Materials and Methods] We analyzed routine clinical EEG from 24 patients. There were 5 to 26 trains of VNS during EEG. To extract SCPs from the EEG, a high-frequency filter of 0.2 Hz was applied. These EEG epochs were averaged and used for source analyses. The averaged waveforms for each patient and their grand average were subjected to multidipole analysis. Patients with at least 50% seizure frequency reduction were considered responders. Findings from EEG analysis dipole were compared with VNS responses. [Results] VNS-induced focal SCPs whose dipoles were estimated to be located in several cortical areas including the medial prefrontal cortex, postcentral gyrus, and insula, with a significantly higher frequency in patients with a good VNS response than in those with a poor response. [Conclusions] This study suggested that some VNS-induced SCPs originating from the so-called vagus afferent network are related to the suppression of epileptic seizures

パーキンソン病患者における神経フィードバック法の訓練を用いた運動準備電位の増強

京都大学0048新制・課程博士博士(医科学)甲第17467号医科博第43号新制||医科||3(附属図書館)30233京都大学大学院医学研究科医科学専攻(主査)教授 福山 秀直, 教授 村井 俊哉, 教授 松原 和夫学位規則第4条第1項該当Doctor of Medical ScienceKyoto UniversityDA

Alpha-band desynchronization in human parietal area during reach planning.

[Objective]The symptoms with optic ataxia suggest that simple and visually guided hand movements are controlled by 2 different neural substrates. To assess the differential frequency-coded posterior parietal cortex (PPC) role in planning visuo-motor goal-directed tasks, we studied the action specificity of event-related desynchronization (ERD) in this area. [Methods]We investigated cortical activity by electroencephalography, while 16 healthy subjects performed self-paced reaching or wrist extension (control) movements. Time–frequency representations were calculated for each movement during the preparatory period. [ResultsERD dynamics in upper alpha-band indicated that preparing a goal-directed action activates contralateral PPC to the moving hand around 1.2 s before starting the movement, while this activation is later (around 0.7 s) in preparing a not-goal-directed action. The posterior dominant rhythm had peak frequency of lower alpha-band at bilateral parietal. [Conclusions]Posterior parietal cortex encodes goal-directed movement preparation through upper alpha-band activity, whereas general attention is processed via lower alpha-band oscillations. [Significance]Preparing to reach an object engages posterior parietal cortex earlier than a not-goal directed movement

Network hyperexcitability in a patient with partial reading epilepsy: converging evidence from magnetoencephalography, diffusion tractography, and functional magnetic resonance imaging.

[Objective]The pathophysiological mechanisms of partial reading epilepsy are still unclear. We delineated the spatial–temporal characteristics of reading-induced epileptic spikes and hemodynamic activation in a patient with partial reading epilepsy. [Methods]Magnetoencephalography (MEG) was recorded during silent letter-by-letter reading, and the source of reading-induced spikes was estimated using equivalent current dipole (ECD) analysis. Diffusion tractography was employed to determine if the white matter pathway connected spike initiation and termination sites. Functional magnetic resonance imaging (fMRI) was employed to determine the spatial pattern of hemodynamic activation elicited by reading. [Results]In 91 spike events, ECDs were clustered in the left posterior basal temporal area (pBTA) during Katakana reading. In 8 of these 91 events, when the patient continued to read >30 min, another ECD cluster appeared in the left ventral precentral gyrus/frontal operculum with a time-difference of ∼24 ms. Probabilistic diffusion tractography revealed that the long segment of the arcuate fasciculus connected these two regions. fMRI conjunction analysis indicated that both Katakana and Kanji reading activated the left pBTA, but Katakana activated the left lateral frontal areas more extensively than Kanji. [Conclusions]Prolonged reading of Katakana induced hyper-activation of the cortical network involved in normal language function, concurrently serving as the seizure onset and symptomatogenic zones. [Significance]Reflex epilepsy is believed to result from intrinsic hyper-excitability in the cortical regions recruited during behavioral states that trigger seizures. Our case shows that reading epilepsy can arise from a hyperexcitable network of cortical regions. Physiological activation of this network can have cumulative effects, resulting in greater reciprocal network propagation and electroclinical seizures. These effects, in turn, may give insights into the brain networks recruited by reading

Bereitschaftspotential augmentation by neuro-feedback training in Parkinson's disease

[Objective]Decreased early Bereitschaftspotential (BP) is one of the electrophysiological characteristics in patients with Parkinson's disease (PD). We examined whether PD patients could increase BP amplitude by means of neuro-feedback (NFB) training for their slow cortical potentials (SCPs). [Methods]We worked with 10 PD patients and 11 age-matched controls. BP was measured for self-paced button pressing by their right thumb. The subjects were instructed to make the introspective efforts to produce negative SCPs (negativation). The one-day session consisted of three trials, that is, the first BP, NFB training and the second BP, and each patient performed this routine for 2–4 days. Amplitudes of the first and second BPs were compared between the two groups that were divided depending on NFB performance. [Results]Good NFB performance had the tendency of larger early BP in the second BP recording than in the first one, whereas in the poor NFB performance the early BP was smaller in the second BP recording than in the first one in both patient and normal groups (p < 0.001). [Conclusions] Good NFB performance of negativation could increase excitatory field potentials of pyramidal cells for the generation of early BP. [Significance]Voluntary regulation of SCPs could enhance BP in PD patients and in aged controls

Parieto-frontal network in humans studied by cortico-cortical evoked potential.

Parieto-frontal network is essential for sensorimotor integration in various complex behaviors, and its disruption is associated with pathophysiology of apraxia and visuo-spatial disorders. Despite advances in knowledge regarding specialized cortical areas for various sensorimotor transformations, little is known about the underlying cortico-cortical connectivity in humans. We investigated inter-areal connections of the lateral parieto-frontal network in vivo by means of cortico-cortical evoked potentials (CCEPs). Six patients with epilepsy and one with brain tumor were studied. With the use of subdural electrodes implanted for presurgical evaluation, network configuration was investigated by tracking the connections from the parietal stimulus site to the frontal site where the maximum CCEP was recorded. It was characterized by (i) a near-to-near and distant-to-distant, mirror symmetric configuration across the central sulcus, (ii) preserved dorso-ventral organization (the inferior parietal lobule to the ventral premotor area and the superior parietal lobule to the dorsal premotor area), and (iii) projections to more than one frontal cortical sites in 56% of explored connections. These findings were also confirmed by the standardized parieto-frontal CCEP connectivity map constructed in reference to the Jülich cytoarchitectonic atlas in the MNI standard space. The present CCEP study provided an anatomical blueprint underlying the lateral parieto-frontal network and demonstrated a connectivity pattern similar to non-human primates in the newly developed inferior parietal lobule in humans

Comparison of Acute Withdrawal and Slow Taper of Antiseizure Medications during Video Electroencephalographic Monitoring: Efficacy for Shortening of Hospital Stay

Antiepileptic medications (ASMs) are withdrawn at the epilepsy monitoring unit to facilitate seizure recordings. The effect of rapid tapering of ASMs on the length of hospital stay has not been well documented. We compared the mean length of hospital stay between patients who underwent acute ASM withdrawal and slow dose tapering during long-term video electroencephalography (EEG) monitoring. We retrospectively investigated 57 consecutive patients admitted to the epilepsy monitoring unit regarding the mean length of hospital stay in the acute ASM withdrawal group (n = 30) and slow-taper group (n = 27). In the acute-withdrawal group, all ASMs were discontinued once the patients were admitted. In the slow-taper group, the doses of ASMs were gradually reduced by 15–30% daily. We also evaluated the safety of the acute-withdrawal and slow-taper protocols. The mean lengths of hospital stay were 3.8 ± 1.92 and 5.2 ± 0.69 days in the acute-withdrawal and slow-taper groups, respectively (p < 0.005). No severe adverse events, including status epilepticus, were observed. Acute ASM withdrawal has the advantage of significantly reducing the length of hospital stay over slow tapering, without any severe adverse effects