Showing papers in "Neurophysiologie Clinique-clinical Neurophysiology in 2009"

Methods of therapeutic cortical stimulation.

Abstract: In the nineties, epidural cortical stimulation (ECS) of precentral region has been performed to treat drug-resistant neuropathic pain and repetitive transcranial magnetic stimulation (rTMS) of prefrontal region has shown antidepressant effects in episodes of major depression. These were among the first attempts to treat neurological or psychiatric disorders with cortical stimulation. Actually, a variety of invasive and noninvasive techniques of cortical stimulation could serve therapeutic purpose, including ECS, rTMS, but also transcranial electrical stimulation using pulsed currents (TCES) or direct currents (tDCS). This review presents the methods of therapeutic cortical stimulation that are currently applicable and some of their principles. In particular, it must be emphasized that the site(s) of action can be distant from the site of stimulation because axons with remote projections are more prone to be activated than local cell bodies. Hence, cortical stimulation may activate, inhibit or otherwise interfere with the activity of various cortico-subcortical networks, depending on stimulus frequency and intensity, current polarity, and the configuration of the induced electric field. Functional and clinical effects occur during or beyond the time of stimulation. The existence of after-effects relates to processes of synaptic plasticity induced by the stimulation. Cortical stimulation may also have neuroprotective effects against disease-related excitotoxic phenomena. Considering the multiple techniques and the various potential clinical indications, it is a challenge to determine the place of cortical stimulation in the treatment of neurological and psychiatric diseases, in particular by the side of deep brain stimulation.

Consensus on the use of neurophysiological tests in the intensive care unit (ICU): electroencephalogram (EEG), evoked potentials (EP), and electroneuromyography (ENMG).

Abstract: Summary Study aim To provide a consensus of European leading authorities about the optimal use of clinical neurophysiological (CN) tests (electroencephalogram [EEG]; evoked potentials [EP]; electroneuromyography [ENMG]) in the intensive care unit (ICU) and, particularly, about the way to make these tests clinically useful for the management of individual patients. Methods This study gathered together several European clinical neurophysiologists and neurointensivists whose leading contributions in the adult or paediatric ICU and in continuous neuromonitoring had been peer-acknowledged. It was based on both a literature review and each participant's own experience. Given the methodological impossibility to gather studies fulfilling criteria of evidence-based medicine, this article essentially relies on expert opinions that were gained after several rounds, in which each expert was invited to communicate his own contribution to all other experts. A complete consensus has been reached when submitting the manuscript. Results What the group considered as the best classification systems for EEG and EP abnormalities in the ICU is first presented. CN tests are useful for diagnosis (epilepsy, brain death, and neuromuscular disorders), prognosis (anoxic ischemic encephalopathy, head trauma, and neurologic disturbances of metabolic and toxic origin), and follow-up, in the adult, paediatric, and neonatal ICU. Regarding prognosis, a clear distinction is made between these tests whose abnormalities are indicative of an ominous prognosis and those whose relative normalcy is indicative of a good prognosis. The prognostic significance of any test may vary as a function of coma etiology. Conclusion CN provides quantitative functional assessment of the nervous system. It can be used in sedated or curarized patients. Therefore, it should play a major role in the individual assessment of ICU patients.

Chronic alcoholism: insights from neurophysiology.

Abstract: The heterogeneity of alcoholic disorders in terms of symptomatology, course and outcome is the result of various pathophysiological processes that physiological parameters may help to define. These alterations may be related to precise cognitive processes that could be easily monitored neurophysiologically in order to create more homogeneous subgroups of alcoholic individuals.

Vestibulocervical reflexes in idiopathic Parkinson disease.

Abstract: Summary Objectives The mechanism of gait instability in Parkinson disease (PD) is not completely understood. We examined the saccular part of the otolith function and its possible contribution to gait difficulties in idiopathic PD. Methods Fifty-four PD patients (mean age 66 years, 32 men) were included. These were characterized with respect to disease severity, duration, treatment, as well as the presence of disease complications, dementia and depression. Vestibular evoked myogenic potentials (VEMP) were recorded in patients and 53 healthy controls. Results VEMP responses were recorded in all controls. Unilaterally absent VEMP responses were found in 20 (37%) of PD patients and bilaterally absent responses in four (7.4%). All patients with preserved peaks had normal latencies as compared with controls. The number of PD patients with abnormal/absent VEMP was thus significantly higher than in controls (p Conclusion PD patients often have absent vestibulocollic reflexes. Further investigations are needed to elucidate the significance of this finding for postural stability and gait in this disorder.

Continuous EEG-SEP monitoring in severe brain injury.

Abstract: Summary Aims To monitor acute brain injury in the neurological intensive care unit (NICU), we used EEG and somatosensory evoked potentials (SEP) in combination to achieve more accuracy in detecting brain function deterioration. Methods Sixty-eight patients (head trauma and intracranial hemorrhage; GCS Results Fifty-five patients were considered “stable” or improving, considering the GCS and CT scan: in this group, SEP didn’t show significant changes. Thirteen patients showed neurological deteriorations and, in all patients, cortical SEP showed significant alterations (amplitude decrease > 50% often till complete disappearance). SEP deterioration anticipated ICP increase in 30%, was contemporary in 38%, and followed ICP increase in 23%. Considering SEP and ICP in relation to clinical course, all patients but one with ICP less than 20 mmHg were stable, while the three patients with ICP greater than 40 mmHg all died. Among the 26 patients with ICP of 20–40 mmHg, 17 were stable, while nine showed clinical and neurophysiological deterioration. Thus, there is a range of ICP values (20–40 mmHg) were ICP is scarcely indicative of clinical deterioration, rather it is the SEP changes that identify brain function deterioration. Therefore, SEP have a twofold interest with respect to ICP: their changes can precede an ICP increase and they can constitute a complementary tool to interpret ICP trends. It has been very important to associate SEP and EEG: about 60% of our patients were deeply sedated and, because of their relative insensitivity to anesthetics, only SEP allowed us to monitor brain damage evolution when EEG was scarcely valuable. Conclusions We observed 3% of nonconvulsive status epilepticus compared to 18% of neurological deterioration. If the aim of neurophysiological monitoring is to “detect and protect”, it may not be limited to detecting seizures, rather it should be able to identify brain deterioration, so we propose the combined monitoring of EEG with SEP.

Spike detection algorithm automatically adapted to individual patients applied to spike-and-wave percentage quantification.

Abstract: Summary Objective To report an innovative spike detection algorithm that tailors its detection to the patient Interictal epileptiform activity quantification was accomplished in the setting of epileptic syndromes with continuous spike and waves during slow sleep, which is a time-consuming task for the EEG analysis Methods The algorithm works in three steps Firstly, a first spike detection is made with generic parameters Secondly, the detected spikes are used to tailor the detection algorithm to the patient; and thirdly, the resulting patient-specific detection algorithm is used to analyze individual patient with high-quality detection Therefore, the algorithm produces a patient-specific template —hence exhibiting improved performance metrics, without the need of a priori knowledge from the experts Results The system was first evaluated for EEG of three patients, against the scoring of three EEG experts, demonstrating similar performance Later, it was evaluated against the spike and wave percentage evaluation of another expert for 17 additional records The difference between the two evaluations was 44% on average, which is almost the same as the interexpert difference (47%) Conclusions We designed a fully automated and efficient spike detection algorithm, which is liable to trim down the specialist's diagnostic time

How far do patients with sensory ataxia benefit from so-called “proprioceptive rehabilitation”?

Abstract: A rehabilitation program including foot sensory stimulation, balance and gait training with limited vision was performed in 24 patients with clinically defined sensory ataxia. There were 15 patients with bilateral somatosensory loss related to chronic neuropathy and nine patients with unilateral loss-related to multiple sclerosis. After training, balance control assessed using the Berg Balance Test improved similarly in both groups, and Romberg's sign disappeared in some patients, suggesting an improvement in dynamic balance and in the proprioceptive contribution. Conversely, balance assessed on a static force platform remained similar in the open-eyes condition and improved in the closed-eyes condition only in patients with unilateral sensory loss. These results show that ataxic patients can improve their balance with better results in dynamic conditions and that the relative contribution of proprioceptive and visual inputs may depend on the extent of somatosensory loss.

How clinical neurophysiology may contribute to the understanding of a psychiatric disease such as schizophrenia.

Abstract: Summary Introduction The increasing knowledge about anatomical structures and cellular processes underlying psychiatric disorders may help bridge the gap between clinical manifestations and basic physiological processes. Accordingly, important insights have been brought these last years into a main psychiatric affection, i.e. schizophrenia. Material and methods Here we reviewed and described, by comparison to healthy people, different physiological parameters – oculomotor measures, startle response, and cognitive event related potentials, which are altered in schizophrenia, in order to link these physiological parameters to dysfunctional cognitive processes and specific clinical symptoms. Results Schizophrenic patients displayed: (1) abnormalities in smooth pursuit eye movements and saccadic inhibition during antisaccade tasks that may stem from the same prefrontal “inhibitory” cortical dysfunction; (2) deficits in prepulse inhibition and facilitation suggesting disturbed attentional modulations, which seem also correlated to abnormal patterns of prefrontal activation; and (3) decreased amplitude for cognitive ERP situated all along the continuum of the information processing, suggesting that schizophrenia shows neurophysiological deficits since the level of the sensory cortex and not only disturbances involving associative cortices and limbic structures. Discussion The heterogeneity of schizophrenic disorders regarding symptomatology, course, and outcome is underlain by various pathophysiological processes that physiological parameters may help define. These alterations may be related to precise cognitive processes that are easily neurophysiologically monitored in order to create more homogeneous subgroups of schizophrenic patients.

Haemodynamic changes during seizure-like activity in a neonate: a simultaneous AC EEG-SPIR and high-resolution DC EEG recording.

Abstract: Summary Objective We sought to define the interaction between neonatal epileptic discharges and the haemodynamic activities in a control situation (i.e. in the absence of cardiorespiratory perturbation or any interaction with normal, ongoing, synchronized neuronal activity). Method Alternating-current electroencephalography (AC EEG), near-infrared spectroscopy (NIRS), and high-resolution direct-current (HR DC) EEG were performed in a curarized, ventilated neonate with a flat interictal EEG. The seizure-like discharges (SLD) first spike was used as a trigger for further averaging of NIRS, AC and DC EEG. Source localization was performed on the averaged spike and the averaged, negative DC shift. Results SLD were of maximal amplitude in centroparietal areas and induced a change in local haemodynamic parameters characterized by a first increase in [HHb] followed by an increase in [HbO 2 ] and [HbT]. [HHb] returned to baseline at the end of the seizure and decreased thereafter. The negative DC shift started before the first spike and the increase in haemodynamic parameters. It then became positive and returned to baseline at the end of the seizure. Source localization revealed different positions for the first spike and the negative DC shift. Discussion Pure SLD in neonates might induce a negative blood oxygen level-dependent (BOLD) effect on the cortex, which occurs after the negative DC shift and which has a closer temporal relationship with the neuronal discharge than a positive BOLD effect.

The importance of stimulus parameters for the experience of the thermal grill illusion.

Abstract: Summary Aims This study aimed to investigate the quality of the thermal grill illusion (TGI) and the importance of stimulus parameters (distance between, and number of stimulation bars). Material and methods Twenty-one different stimuli were applied to a group of 19 healthy subjects on the glabrous skin over the palm and fingers. Results The TGI was found to be painful (19.42% on the palm; 17.98% on the fingers), mechanical (25.24% on the palm; 5.62% on the fingers), emotional (13.59% on the palm; 14.61% on the fingers) or unusual (42.72% on the palm; 61.8% on the fingers) sensations. A total of 89.5% (palm) and 94.4% (fingers) of the subjects reported TGI. Between 45% (fingers) and 50% (palm) of the stimuli elicited TGI. Neither the distance (2 ∼ 10 mm) between adjacent warm (40 ± 1 °C) and cold (20 ± 1 °C) bars nor the number of the stimulation bars (2 ∼ 6) significantly affected the occurrence of the TGI (N.S.). The average reaction time was 2.4 ± 0.1 seconds to the TGI sensation. Females showed longer reaction time than males ( P ≤ 0.001). Conclusion The distance and number of stimulation bars were not important to the sensation of TGI, of which the responses varied. These results are useful for future TGI studies with respect to experimental design. The variability of the TGI needs to be considered in future experimental and clinical studies.

Electroencephalographic analysis for the assessment of hepatic encephalopathy: comparison of non-parametric and parametric spectral estimation techniques.

Abstract: Summary Objective To compare electroencephalographic spectral analysis obtained by periodogram (calculated by means of Fast Fourier Transform) and autoregressive (AR) modelling for the assessment of hepatic encephalopathy. Methods The mean dominant frequency (MDF) and the relative power of delta, theta, alpha, and beta bands were computed by both techniques from the electroencephalograms (EEG) of 201 cirrhotics and were evaluated in the clinical and prognostic assessment of the patients. Results The values of all the five indexes computed by periodogram and AR modelling matched each other, but the latter provided stable values after the analysis of fewer epochs. Independently of the technique, the relative power of theta and alpha bands fitted the clinical data and had prognostic value. The relative power of beta and delta bands computed by AR modelling fitted more closely with clinical data fitted the clinical data more closely. Conclusions The electroencephalographic spectral indexes obtained by periodogram and AR modelling were found to be, on average, undistinguishable, but the latter appeared less sensitive to noise and provided a more reliable assessment of low-power bands.

A-delta and C-fibres function in primary restless legs syndrome.

Abstract: Summary Study aims The sensory symptoms that are reported in restless legs syndrome (RLS) suggest involvement of the peripheral nervous system (PNS) in general and of the small-fibre system in particular. We aimed to study the status of the small-fibre system in primary RLS. Patients and methods We investigated 10 patients with idiopathic RLS (mean time since disease onset: 11.4 ± 12 years, mean International Restless Legs Syndrome Study Group [IRLSSG] score: 23.4 ± 8). Five had a family history. All had normal results for laboratory tests, neurological examination, and a sural/deep-peroneal nerve conduction study. Lower-limb thulium YAG laser-evoked potentials (LEP) and skin sympathetic reflexes (SSR) were performed. The results were compared with data from 10 healthy subjects. Results The nociceptive thresholds were 293 ± 62 mJ for patients and 333 ± 77 mJ for controls. For patients, the vertex N2 and P2 latencies were 208 ± 25 ms and 366 ± 51 ms, respectively (controls: N2 = 235 ± 41 ms; P2 = 373 ± 44 ms). The N2-P2 amplitude was 19 ± 6 μV for patients and 18 ± 7 μV for controls. SSR were normal in all patients. No significant differences between patients and healthy subjects were observed. Conclusion We failed to demonstrate any significant involvement of small fibres and spinothalamic tracts in idiopathic RLS. Even though sufferers of this specific form of RLS report sensory symptoms, pathogenesis appears to be dissociated from a PNS alteration.

Autonomic aspect of emotional response in depressed patients: relationships with personality.

Abstract: Summary Study aim Affective symptoms are major descriptors of depression; therefore, a lot of studies investigated emotional-responsiveness modulation in depression, and reported either a potentiation of negative affects, a reduction of positive affects, or a reduction of both positive and negative affects On the other hand, personality was classically found to be modulated in depression, with behavioral inhibition system (BIS)-related dimensions (namely harm avoidance (HA), neuroticism) showing higher scores in depressed subjects The aim of this study was to investigate the relationships between emotional responsiveness (as measured by skin conductance response [SCR]) and personality in depression Methods SCR was recorded following the presentation of neutral, pleasant, and unpleasant pictures in 20 depressed subjects and 20 controls Results Pleasant pictures elicited more and larger responses than unpleasant ones in control but not in depressed subjects This effect was not modulated by personality Moreover, depressed subjects were found to show generally faster half-recovery times and to rate emotional pictures as less arousing than control subjects and these effects disappeared when BIS-related dimensions were controlled Conclusions These results suggest that BIS-related dimensions are independent from the specifically reduced responses to pleasant pictures, but are involved in the observed general affect reducing

Mélatonine et troubles du rythme veille-sommeil

Abstract: Resume La melatonine, hormone produite par la glande pineale, est secretee preferentiellement pendant la nuit avec un pic situe vers 03 h 00 du matin. Ce rythme endogene est genere par les noyaux suprachiasmatiques de l’hypothalamus et entraine par l’alternance jour/nuit. La lumiere artificielle selon les conditions d’administration supprime ou decale la secretion de melatonine. Le role de la melatonine est celui d’un synchroniseur endogene des rythmes circadiens, des rythmes de temperature et de veille-sommeil en particulier. L’administration de melatonine est capable d’influencer son rythme endogene selon une courbe de reponse de phase. Cette donnee constitue la base physiologique du traitement des dysrythmies (syndrome de franchissement rapide des fuseaux horaires, syndrome de retard de phase, desynchronisation chez les aveugles). L’interet de la melatonine dans le traitement de l’insomnie, en particulier liee au vieillissement, vient d’etre relance avec la mise sur le marche d’une preparation a liberation prolongee.

Transient post-traumatic locked-in syndrome: a case report and a literature review.

Abstract: Summary Introduction Post-traumatic locked-in syndrome may be particularly difficult to recognize, especially when it follows a state of coma and presents the clinical feature of a “total” locked-in syndrome. Patient and methods A 56-year-old male with a closed head injury was admitted in intensive care unit (ICU) with GCS = 4 (V1, M2, E1). Computed tomography (CT) scan disclosed a limited subarachnoid haemorrhage in the sylvian region without any brain oedema or ventricular shift. The GCS did not change until day 6. At the same time EEG showed a reactivity to acoustic stimuli consisting in the paradoxical appearance of a posterior rhythm in alpha range (10–12 c/s), blocked by passive eye opening. Early cortical components (N20–P25) of somatosensory evoked potentials were normal on both hemispheres; middle components were also clearly evident. Magnetic resonance imaging of the brain showed both diffuse and midbrain axonal injuries, particularly in a strategic lesion involving both cerebral peduncles. Event related potentials showed N2 and P3 components to stimulation by rare tones. Conclusions A comprehensive multimodal neurophysiological approach, using the more informative tests and the proper time of recording, should be included in protocols for patients with severe head trauma, in order to establish the actual patient's clinical state and to avoid that a locked-in syndrome state be mistaken for prolonged coma, vegetative state, minimally conscious state or akinetic mutism. Neurophysiological evaluation before discharge from ICU can be a baseline evaluation useful for the follow-up of low-responsive patients in the neuro-rehabilitation unit.

Low-frequency rTMS of the premotor cortex reduces complex movement patterns in a patient with pantothenate kinase-associated neurodegenerative disease (PKAN)

Abstract: Summary Introduction Pantothenate kinase-associated neurodegenerative disease (PKAN) is a secondary generalized dystonia associated with an accumulation of iron in the basal ganglia and increased motor cortex excitability. A pilot study in three patients with secondary generalized dystonia had reported a reduced frequency of painful axial spasms following inhibitory 1-Hz repetitive transcranial magnetic stimulation (rTMS) applied over the premotor cortex. Patient and methods We compared the effects of real versus sham rTMS on the frequency of the complex movement pattern and the need for additional benzodiazepine medication in a 6-year-old male patient with PKAN. A 20-minute session of left premotor 1-Hz rTMS was performed daily on 5 consecutive days. Results The occurrence of the complex movement pattern was gradually reduced from three to two attacks daily to one attack daily by real rTMS while sham rTMS had no effect. This reduction was obtained concomitantly with a similar reduction of additional benzodiazepines for both real and sham rTMS sessions. Conclusion Inhibitory rTMS of the premotor cortex may be used to temporarily control motor symptoms in PKAN.

Wicket spikes misinterpreted as focal abnormalities in idiopathic generalized epilepsy with prescription of carbamazepine leading to paradoxical aggravation.

Abstract: Wicket spikes (WS) are a normal variant EEG pattern that sometimes can be mistaken for epileptiform activity. We present a patient with WS and idiopathic generalized epilepsy who had been wrongly diagnosed with focal epilepsy, which leads to the prescription of carbamazepine with severe aggravation of generalized tonic-clonic seizures. She was referred for presurgical assessment of refractory focal epilepsy but long-term video-EEG showed sharp theta waves over the temporal regions during awakening, with a typical aspect of WS during drowsiness, nREM sleep stages I-II, and rapid eye movements (REM) sleep. There were a few generalized spike-waves during sleep but interictal changes were increased in frequency at awakening with bursts of fast-generalized spike-waves. Carbamazepine was progressively withdrawn and the patient was progressively switched to zonisamide. The patient no longer complained of generalized tonic-clonic seizures. At one year follow-up, this patient receives zonisamide with valproate. She has remained seizure-free.

Personality modulation of P300 wave recorded within an emotional oddball protocol.

Abstract: Summary Objectives Several studies reported that personality modulates responses to emotional stimuli, including cognitive and attentional aspects of the emotional response. The aim of this study was to refine these results while using visual event-related potentials (ERPs) and referring to Cloninger's personality model. Methods ERPs were recorded in 46 normal subjects within a visual oddball protocol with checkerboards as the standard stimuli and pictures selected as neutral, pleasant or unpleasant from the International Affective Picture System as the target stimuli. Results N200 amplitude was smaller and P300 amplitude was larger following the presentation of pleasant pictures in low-harm avoidance but not high-harm avoidance subjects. Conclusions These results support the idea that both automatic and selective cognitive processing of emotional pictures is modulated by personality.

Physiologie de l’horloge circadienne endogène : des gènes horloges aux applications cliniques

Abstract: Resume Une multitude d’activites biologiques telles que les concentrations hormonales, les performances cognitives, la puissance musculaire, le cycle veille-sommeil et, plus recemment mises en evidence, la division cellulaire et la reparation de l’ADN, presentent une rythmicite de 24 heures, directement controlee par l’horloge circadienne endogene. Leur expression appropriee au cours des 24 heures necessite la synchronisation de l’horloge, principalement realisee par la lumiere au niveau oculaire. Un defaut de synchronisation de l’horloge circadienne se traduit par l’alteration des fonctions sous son controle et conduit a des alterations de la veille, du sommeil, de l’humeur, des processus neurocognitifs et du cycle cellulaire. Les troubles du rythme circadien du sommeil et certaines depressions peuvent etre traitees par des approches chronobiologiques, telles que la phototherapie.

Time and frequency domain analysis of surface myoelectric signals during electrically-elicited cramps.

Abstract: OBJECTIVES: To examine if different frequencies of electrical stimulation trigger different sized cramps in the abductor hallucis muscle and to analyze their surface electromyographic (EMG) behaviour in both time and frequency domains. METHODS: Fifteen subjects were studied. Stimulation trains of 150 pulses were applied to the muscle motor point. Frequency was increased (starting from 4pps with 2-pps steps) until a cramp developed. Current intensity was 30% higher than that eliciting maximal M-waves. After the first cramp ("threshold cramp"), a 30-minute rest was provided before a second cramp ("above-threshold cramp") was elicited with a frequency increased by 50% with respect to that eliciting the first cramp. RESULTS: We found greater EMG amplitude and a compression of the power spectrum for above-threshold cramps with respect to threshold cramps. M-wave changes (ranging between small decreases of M-wave amplitude to complete M-wave disappearance) occurred and progressively increased throughout stimulation trains. Significant positive correlations were found between estimates of EMG amplitude during cramps and estimated reductions of M-wave amplitude. CONCLUSIONS: Varying frequencies of electrical stimulation triggered different sized cramps. Moreover, decreases in M-wave amplitude were observed during both threshold and above-threshold stimulations. The choice of the stimulation frequency has relevance for optimizing electrical stimulation protocols for the study of muscle cramps in both healthy and pathological subjects.

Sensations and reaction times evoked by electrical sinusoidal stimulation.

Abstract: Summary Objective To determine whether 5 Hz and 2000 Hz sinusoidal electric currents evoke different sensations and to indirectly evaluate which peripheral nerve fibers are stimulated by these different frequencies. Methods One hundred and fifty subjects chose three among eight descriptors of sensations evoked by 5 Hz and 2000 Hz currents and the results were submitted to factor analysis. In 20 subjects, reaction times to 5, 250 and 2000 Hz currents were determined at 1.1x ST and reaction times to 5 Hz currents were also determined at 2x ST. Results Responses were grouped in four factors: Factor 1, which loaded mainly in descriptors related to tweezers stimulation, was higher than the other factors during 2000 Hz stimulation at 1.5x ST. Factor 2, which loaded mainly in descriptors related to needle stimulation, was higher than the other factors during 5 Hz stimulation. Factor 1 increased and Factor 2 decreased with an increase in 5 Hz intensity from 1.5 to 4x ST. Reaction times measured from the fastest responses were significantly different: 0.57 s (0.16 to 1.60), 0.34 s (0.12 to 0.71) and 0.22 s (0.08 to 0.35) for 5, 250 and 2000 Hz, respectively, and 0.22 s (0.11 to 0.34) for 5 Hz at 2x ST. Conclusions Sinusoidal electrical stimulation of 5 Hz and 2000 Hz evoke different sensations. At juxta-threshold intensities, RT measurements suggest that 2000 Hz stimulates Aβ-fibers, 250 Hz Aβ- or A∂-fibers, 5 Hz Aβ-, A∂- or C-fibers. The fiber type, which was initially stimulated by the lower frequencies, depended on inter-individual differences.

Prognostic role of somatosensory and auditory evoked potentials in paediatric hypoxic-ischemic encephalopathy managed with hypothermia: An illustrative case

Abstract: Summary Introduction The contribution of clinical neurophysiology in the neurological prognosis of hypoxic-ischemic coma has been well established in adults: the bilateral absence of cortical somatosensory evoked potentials (SEP) is considered the single best indicator of adverse outcome, while the presence of the auditory mismatch negativity (MMN) is thought to herald arousal. Study aim To use MMN combined with serial EEG recordings, somatosensory and brainstem auditory evoked potentials (BAEP) in a paediatric case of postanoxic coma managed with hypothermia, since they have not yet been described in children. Methods We report the case of a nine-year-old boy with hypoxic-ischemic encephalopathy due to cardiorespiratory arrest after accidental burial in sand, who was treated with therapeutic hypothermia for 72 hours. Serial EEG recordings, evoked potentials, brain CT scan and brain MRI were performed in the first few days after the event. Results SEP to median nerve stimulation showed bilateral absence of the N20 component, while the N13 and P14 peaks were preserved; BAEP showed normal I–V interpeak latency and normal hearing threshold. At the same time, the MMN component of auditory event related potentials, recorded in the classical oddball paradigm, was absent. Seventeen months after the accident, the patient is alive in persistent vegetative state. Conclusions This case illustrates the particular significance of SEP and MMN together with EEG in gaining prognostic information, even in sedated and hypothermic patients, and encourages systematic study of these prognostic tools in paediatric postanoxic coma.

L’évaluation du chronotype en clinique du sommeil

Abstract: Resume L’examen visuel d’un agenda du sommeil permet de diagnostiquer les troubles du rythme circadien du sommeil (TRCS) et de visualiser une mauvaise hygiene du sommeil ou un syndrome d’insuffisance du sommeil. Les questionnaires de chronotypes, qui permettent d’identifier les sujets du matin ou du soir, presentent un interet indeniable en clinique du sommeil mais ne peuvent pas etre utilises pour confirmer un TRCS. L’estimation du chronotype permet d’expliquer les horaires de sommeil et leur stabilite, la duree du sommeil, les besoins de sommeil, la qualite du sommeil, la somnolence matinale, l’adaptation au travail poste, etc. De plus, les sujets du soir sont confrontes a une privation chronique de sommeil les jours de travail qu’ils compensent en allongeant la duree du sommeil les jours de repos et en consommant des substances eveillantes. Le questionnaire de matinalite et vesperalite de Horne et Ostberg serait le questionnaire de reference, mais celui-ci presente certaines limites (19 items, non adapte aux sujets travaillant en poste ou de nuit, etc.) et doit prendre en compte l’âge des sujets. En revanche, le fait de presenter les caracteristiques des sujets du matin et du soir et de demander ensuite au sujet d’estimer son chronotype serait une alternative en clinique du sommeil.

The two sensory branches of the superficial peroneal nerve: Electrophysiological differences and correlations with gender, age, height and BMI

Abstract: Summary Aims of the study To detect amplitude differences between the sensory nerve action potentials (SNAP) obtained by simultaneous recording of the two main branches of the superficial peroneal sensory nerve (SPSN), the medial and intermediate dorsal cutaneous sensory nerves (MDCN, IDCN); to investigate whether these differences, if any, are correlated with gender, age, body mass index (BMI), and height of normal subjects; to discuss their clinical significance. Population and methods Seventy-six healthy volunteers (36 males) were included (mean age: 36.5 years, range 20–80). Simultaneous MCND and IDCN recordings were performed via surface electrodes placed at precise positions on the intermalleolus line. Stimulation was performed 14 cm proximally on two different sites over the anterolateral aspect of the right leg. Results Responses were obtained for both nerve branches in all subjects. Median value and lower normal limit for the amplitude of the greater among both MDCN and IDCN responses was 10.95 μV and 4.9 μV, respectively. Statistically significant differences were found between the two branches in median amplitude and frequency of the greater value. These differences were not correlated with gender, age, BMI, or height. Conclusion We propose simultaneous recording of the two main branches of the superficial peroneal sensory nerve, placing the recording electrodes and stimulation device on precise positions and measuring the amplitude of the best of both responses. This method is an improvement of an already existent one, and may be clinically useful in detecting abnormal responses of the SPSN.

Changes in local and distant EEG activities before, during and after the observation and execution of sequential finger movements

Abstract: Aim of the study: To consider cortical oscillations at local and distant/large scale levels during the time course of motor events under both an observation and an execution condition. Methods: Local and distant changes in EEG cortical oscillations were respectively assessed by the Event-Related Desynchronization/Synchronization technique and the Synchronization Likelihood technique. Data collected prior to, during, and after observation and execution of complex sequential finger movements were used to investigate these changes. EEGs were recorded from 19 active sites across the cortex of 10 subjects. Sensorimotor activity was examined in alpha frequency bands. Results: Local power changes and global interregional synchronizations were two distinct phenomena, which occurred simultaneously and displayed different spatiotemporal patterns. Discussion and conclusions: These findings demonstrate the complementary character of both analysis techniques. Results are discussed in light of the recent findings from the cognitive and behavioural neuroscience literature.

Neuroleptic malignant syndrome and acute motor axonal neuropathy after Campylobacter jejuni infection

Abstract: We report the case of a patient with Parkinson's disease who developed rapidly progressive weakness of the four limbs due to an acute motor axonal neuropathy (AMAN). This occurred days after a neuroleptic malignant syndrome (NMS). Serologic evidence of a preceding Campylobacter jejuni infection was detected and treatment with intravenous immunoglobulins proved effective. This case suggests that the rarely described neuropathies occurring with NMS may have a postinfectious immune basis and respond to immunomodulatory therapy.

Links between the number of sleep ultradian cycles and REMS duration: Confirmation in rats

Abstract: Preferential links were found in previous studies between the number of sleep ultradian cycles (NCy) and the duration of rapid eye movement sleep (REMS), not the duration of non-REMS (NREMS). This was shown in healthy human controls [2], depressive patients [4], as well as in mice [3]. Furthermore, in the human control study, no relationship was found between the NCy and the intensity of sleep (slow wave activity). The present retrospective study performed on rats aimed to check whether these relationships could be generalized in another species. Sixteen male Sprague-Dawley rats, 250—300 g, were implanted with chronic electrodes under intraperitoneal chlornembutal 3 ml/kg anesthesia about 10 days before recordings began [5]. Each rat was housed in a 30 cm × 30 cm × 25 cm cage, placed within an 80 cm × 80 cm × 80 cm sound-isolated cube, under a light-dark schedule with lights on from 08:00 to 20:00 local time. Two cortical, one hippocampal and one muscle derivation were brought through a slip-ring assembly to a polygraph. A REMS cycle was defined as comprising one REMS episode and an adjacent interval without REMS. A smoothing procedure was used to incorporate isolated epochs into the surrounding stages. More details on the methodology can be found in Vivaldi et al.’s original paper (1994) [5]. The average daytime total sleep time was 453.2 min (24.8); mean NREMS was 365.4 min (26.1); mean REMS was 88.2 min (14.2); mean NCy was 79.4 (15.4). As in the previous cited studies, positive correlations were found between the NCy and REMS, not NREMS (Fig. 1). The positive correlation between the NCy and the ratio between REMS and NREMS indicates that the more numerous the ultradian cycles, the more REMS will be found in comparison with NREMS. We now have convergent data in two independent human samples as well as in two rodents species. The likelihood of a mammal invariant relationship is thus high, especially since it is now confirmed in both monophasic (humans) and polyphasic (rodents) sleep organizations. The first of the two main hypotheses about the ultradian cyclicity considers NREMS, and especially its deep sleep component (slow wave activity), to be the main drive for the cycling, REMS being permitted between hypothesized peaks [1]. The second hypothesis considers the opposite, i.e., REMS inhibits and interrupts a noncyclical NREMS several times in the night [5]. If REMS and NREMS compete against each other, the relative pressure for their expression should be translated into both duration of episodes and number of cycles. It seems reasonable to predict both a higher number of cycles and longer duration of episodes in cases of higher pressure for a sleep state and thus a positive link between these two variables. In any case, it seems more consistent for any sleep regulation mechanism to present with a link between the number of cycles and the duration of the concerned sleep state than with the other. The present data thus indirectly support that REMS is the primum movens in the alternation between the two sleep states.

Minimal electrical stimulation intensity and duration to elicit maximal cutaneous silent period in hand.

Abstract: Summary Introduction The cutaneous silent period (CSP) is an interruption of electromyographic activity produced by a painful stimulation delivered in homotopic cutaneous territory. It may be useful in evaluating small afferent fibers. However, standardized parameters of stimulation still need to be carefully defined before using this technique in routine clinical application. In this study, we investigated the effects of stimulus intensity and duration on the CSP. Methods Twenty healthy adults were included. The digital cutaneous nerve of the right index finger was stimulated and the CSP was measured from the right thenar muscle. The voluntary contraction of thenar muscle was maintained at 50% of maximal voluntary contraction, and the digital cutaneous nerve was stimulated using 0.1, 0.2, 0.5, and 1.0 ms durations and, for each stimulus duration, intensities increasing from 30 to 80 mA in 10 mA steps. Results CSP duration first increased with increasing stimulus intensity and duration and then reached a plateau. Maximal CSP duration ranged from 34.7 to 71.0 ms (mean ± S.D.: 51.2 ± 9.5 ms). CSP duration was not significantly different for intensities varying between 40 and 80 mA and for stimulus durations varying between 0.2 and 1.0 ms. Conclusion This study demonstrates a high inter-individual variability of maximal CSP duration, and that CSP duration first increased with stimulus intensity and duration and then reached a plateau. We suggest to use a minimal stimulus intensity of 40 mA, and a minimal stimulus duration of 0.2 ms in order to elicit maximal CSP duration.

Sommeil et grossesse

Abstract: Resume Les troubles du sommeil et de la vigilance sont particulierement frequents chez la femme enceinte et sont lies aux modifications hormonales, morphologiques et parfois psychologiques induites par la grossesse. Ces troubles apparaissent plus frequents et plus invalidants au fur et a mesure de l’avancee de la grossesse et disparaissent generalement quelques semaines apres l’accouchement. Le syndrome des jambes sans repos et l’insomnie sont les plus frequents. Le syndrome d’apnees du sommeil est important a depister, car potentiellement source de complications fœtomaternelles. La prise en charge de ces troubles est specifique et doit etre adaptee a la grossesse en evitant si possible le recours aux medicaments.

Travail posté et cancers

Abstract: Resume En depit d’un cadre legislatif qui stipule que le travail de nuit doit rester exceptionnel, force est de constater que les rythmes de travail en horaires postes sont de plus en plus frequents, ce qui n’est pas sans consequence sur l’organisme. En effet, la deregulation des rythmes circadiens genere des troubles du sommeil, mais a aussi des repercussions sur le systeme cardiovasculaire, le fonctionnement digestif et le systeme immunitaire. Apres un rappel du contexte reglementaire actuel en France, la problematique des liens entre travail poste et cancers sera abordee avec l’exemple du cancer du sein.