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{#article-title-2} I read with interest the report of Teo et al.1 on acute vascular syndromes attributed to cerebral microbleeds (CMBs). Assessing neurologic presentations in these patients can be challenging; we recently encountered a patient who illustrated the diversity of presentation of this condition. A 53-year-old man with previous whole brain irradiation for metastatic cancer reported repeated episodes of slowly progressive (over 5–60 minutes) unilateral weakness, proceeding to right or left hemiplegia lasting several hours. There was a visual disturbance at symptom onset and a unilateral headache at some stage. Neurologic examination and routine EEG were normal; brain MRI demonstrated multiple widespread punctuate CMBs (figure). Complex secondary migraine was diagnosed and prophylactic treatment suggested. Months later the patient presented to his local hospital with a further such episode progressing to complete flaccid right hemiplegia and global aphasia. Neuroimaging showed no new changes. He was transferred to our center after a week of failing to improve. Though … Correspondence to: jthteo{at}gmail.com Correspondence to: sethinitinmd{at}hotmail.com Correspondence to: jacques.luaute{at}chu-lyon.fr

Summary It is now firmly established that bilateral abolition of somatosensory evoked potentials (SEPs) after a nontraumatic coma has 100% specificity for nonawakening. In traumatic coma, a bilateral absence of the N20 components of SEPs does not implicate nonawareness. Comatose brain-injured patients should be systematically explored with auditory evoked potentials to check the functional integrity of another sensory pathway and the mesencephalic tegmento-tectal region on cerebral MRI should be carefully examined. Repeated evaluations during follow-up are also mandatory.

Resume Nous avons realise l'exploration fonctionnelle de la voie auditive chez 67 patients atteints d'accidents vasculaires cerebraux ischemiques ou hemorragiques du territoire vertebrobasilaire, en effectuant des potentiels auditifs precoces (PEAP) et de latence moyenne (PEALM) (chez 39 d'entre eux), en complement de l'imagerie morphologique (IRM ou TDM). Les PEAP sont anormaux chez 41 des 67 patients, et les PEALM sont anormaux chez 25 des 39 patients en ayant beneficie. Les anomalies electrophysiologiques predominent lors de lesions massives du tronc cerebral (atteintes pontomesencephaliques ou bulbopontiques), ainsi que dans les lesions localisees a la protuberance. Elles sont homolaterales a la lesion anatomique hormis deux cas. Tous les patients ayant des PEAP normaux ont une conscience normale. La normalite des PEALM chez les patients comateux apparait comme un facteur de bon pronostic. L'etude des modifications des reponses auditives precoces et de latence moyenne s'avere complementaire de l'examen clinique et des donnees de l'imagerie, en temps qu'aide a la localisation lesionnelle et determination d'un facteur pronostic.

Thiobacillus novellus (type strain) was grown chemolithoautrophically on thiosulfate in batch cultures under microaerophilic conditions. Under these conditions,T. novellus grew exponentially (μ=0.05–0.06 h−1). The respiratory oxidation rates of tetrathionate, thiosulfate, elemental sulfur (So), and sulfite were measured respirometrically with an oxygen electrode, with exponentially growing cells. Cells growing on thiosulfate as the unique energy source retain thiosulfate-oxidizing activity, So-oxidizing activity (SOA), and very high sulfite-oxidizing activity, but lack respiratory tetrathionate-oxidizing activity. HQNO (50 μm), an inhibitor of the quinone-cytochrome b region, strongly inhibited the SOA (70%), moderately the sulfite-oxidizing activity (45%), and poorly the thiosulfate-oxidizing activity (15%), 1mm KCN totally inhibited (>89%) all respiratory activities. This study confirms that inThiobacillus novellus, as well as in otherThiobacilli, SOA is present in cells grown with thiosulfate as sole electron donor. SOA appears not to be an oxygenase; it is linked to the respiratory chain, and the electrons are probably released in the quinone-cytochrome b region.

Resume Les auteurs ont fait une revue de l'effet des anesthesiques sur les potentiels evoques (PE) auditifs precoces et de latence moyenne, sur les potentiels somesthesiques et sur les potentiels visuels. Les effets des anesthesiques intraveineux et des anesthesiques volatiles ont ete successivement etudies. La surveillance neurophysiologique sous anesthesie generale sera d'autant plus efficace qu'elle prendra en compte les notions suivantes : 1) les anesthesiques volatiles halogenes exercent une action plus puissante sur les PE que les anesthesiques intraveineux, ceci quelle que soit la modalite sensorielle consideree ; 2) les reponses corticales sont plus sensibles a l'action des anesthesiques que les reponses sous-corticales ; 3) la reponse corticale primaire est plus resistante que les composantes plus tardives ; 4) l'administration continue des anesthesiques doit etre preferee a l'administration discontinue en bolus. Les PE peuvent egalement etre utilises en tant que mesure de la profondeur anesthesique ; pour cela, les reponses auditives de latence moyenne semblent actuellement les mieux adaptees. Enfin certains problemes poses par l'administration des anesthesiques intraveineux en reanimation ont ete abordes.

Objective To investigate long-term (LTH) and short-term (STH) habituation of auditory event-related potentials (ERPs) during a migraine cycle, using a classic habituation paradigm. Methods In 22 patients suffering from menstrually-related migraine and in 20 age-matched control subjects, auditory ERPs were recorded in 3 sessions: in the middle of the menstrual cycle, before menses, and during menses. In 12 patients, a migraine attack occurred during one of the peri-menses sessions. In each session, 200 trains of stimuli were presented, with an average of 10 stimuli per train. Results In response to the first stimuli of the trains, migraineurs exhibited in all sessions a larger orienting component of N1 than matched controls and a larger P3a in the interictal session, which normalized during attacks. They also showed a residual orienting component in response to the subsequent stimuli inside the trains. In contrast, the sensory component of N1 showed no difference between the two groups, with similar STH and LTH. Conclusions Migraineurs show an exacerbated attention orienting to auditory stimulation, without any habituation deficit. Significance Previous migraine studies reported interictal habituation deficits of ERPs, but demonstrated in the auditory modality only in paradigms testing intensity dependence. Previous and current results can be interpreted as an increased attention orienting, possibly relying on an abnormal involvement of frontal cortex in auditory processing.

The authors have reviewed hearing results obtained in 99 patients operated on via the suboccipital approach for acoustic neurinoma, who were not deaf prior to surgery (pure tone average less than 70 dB). Tumor size was less than 10 mm in four cases, 10 to 19 mm in 26 cases, 20 to 29 mm in 39 cases, and 30 mm or greater in 30 cases. Removal was macroscopically complete in 92 cases and incomplete in seven, including four cases with bilateral acoustic neurofibromatosis. Hearing was preserved in 29 patients (29.3%), of whom 23 had neurinomas smaller than 30 mm and six had tumors exceeding 30 mm in size. Postoperative hearing was good in eight cases (four with neurinomas less than 20 mm and four with neurinomas greater than 20 mm), serviceable in four cases (three with neurinomas less than 20 mm and one with a tumor greater than 30 mm), and poor in 17 cases (eight with neurinomas less than 20 mm and nine with tumors greater than 20 mm). Fifty-seven patients underwent intraoperative brain-stem auditory evoked potential monitoring: the rate of hearing preservation was found to be higher in this group than in the 42 without monitoring (p less than 0.05). A statistical study using stepwise regression analysis showed that the two preoperative factors most significantly associated with postoperative hearing preservation are a good auditory level for low frequencies measured by pure tone audiometry and a small-sized tumor. Overall results indicate that, even if hearing is more easily preserved when the neurinoma is small and the preoperative auditory condition is good, the surgeon should try to save hearing in all patients who have preserved hearing before surgery.

This paper describes recommended methods for the use of event-related brain potentials (ERPs) in clinical research and reviews applications to a variety of psychiatric and neurological disorders. Techniques are presented for eliciting, recording, and quantifying three major cognitive components with confirmed clinical utility: mismatch negativity (MMN), P300, and N400. Also highlighted are applications of each of the components as methods of investigating central nervous system pathology. The guidelines are intended to assist investigators who use ERPs in clinical research, in an effort to provide clear and concise recommendations and thereby to standardize methodology and facilitate comparability of data across laboratories.

Objective To assess patterns of novelty P3 elicited by the subject’s own name (SON) in comatose patients and to compare SON novelty P3 prognostic value with that of mismatch negativity (MMN). Methods A passive oddball paradigm, previously validated in healthy subjects, including duration deviants and SON presented as a novel was applied in 50 severe comatose patients on average 20 days after coma onset. The outcome was assessed 3 months after coma onset. Results MMN to deviants was found in 14/50 patients and a central–parietal P3 to SON was found in 21/50 patients. In 12 patients, a parietal component (P3b) was also clearly present in the late part of P3. Four patients showed an MMN but no P3. Eleven patients had a novelty P3, with a late parietal component for 5 of them, but no MMN. The presence of a P3 was highly correlated with awakening. Compared to MMN, P3 showed as large a specificity for awakening (0.85). It showed a much higher sensitivity (0.71 versus 0.42). All but one patient with P3b woke up. Conclusions The use of novelty P3 elicited by SON increases the prognostic value of MMN alone and improves the assessment of comatose patients by demonstrating the activation of higher-level cognitive functions in some of them. It shows that unconsciously perceived stimuli are processed and activate brain areas similarly to consciously perceived stimuli. Significance SON as a novel in an MMN design can be used to increase the prognostic value of ERPs in comatose patients and to assess unconscious cognitive processes in uncommunicative patients.

International audience; Hemodynamic studies have shown that the auditory cortex can be activated by visual lip movements and is a site of interactions between auditory and visual speech processing. However, they provide no information about the chronology and mechanisms of these cross-modal processes. We recorded intracranial event-related potentials to auditory, visual, and bimodal speech syllables from depth electrodes implanted in the temporal lobe of 10 epileptic patients (altogether 932 contacts). We found that lip movements activate secondary auditory areas, very shortly (approximately equal to 10 ms) after the activation of the visual motion area MT/V5. After this putatively feedforward visual activation of the auditory cortex, audiovisual interactions took place in the secondary auditory cortex, from 30 ms after sound onset and before any activity in the polymodal areas. Audiovisual interactions in the auditory cortex, as estimated in a linear model, consisted both of a total suppression of the visual response to lipreading and a decrease of the auditory responses to the speech sound in the bimodal condition compared with unimodal conditions. These findings demonstrate that audiovisual speech integration does not respect the classical hierarchy from sensory-specific to associative cortical areas, but rather engages multiple cross-modal mechanisms at the first stages of nonprimary auditory cortex activation.

In noisy environments, we use auditory selective attention to actively ignore distracting sounds and select relevant information, as during a cocktail party to follow one particular conversation. The present electrophysiological study aims at deciphering the spatiotemporal organization of the effect of selective attention on the representation of concurrent sounds in the human auditory cortex. Sound onset asynchrony was manipulated to induce the segregation of two concurrent auditory streams. Each stream consisted of amplitude modulated tones at different carrier and modulation frequencies. Electrophysiological recordings were performed in epileptic patients with pharmacologically resistant partial epilepsy, implanted with depth electrodes in the temporal cortex. Patients were presented with the stimuli while they either performed an auditory distracting task or actively selected one of the two concurrent streams. Selective attention was found to affect steady-state responses in the primary auditory cortex, and transient and sustained evoked responses in secondary auditory areas. The results provide new insights on the neural mechanisms of auditory selective attention: stream selection during sound rivalry would be facilitated not only by enhancing the neural representation of relevant sounds, but also by reducing the representation of irrelevant information in the auditory cortex. Finally, they suggest a specialization of the left hemisphere in the attentional selection of fine-grained acoustic information.

With a view to elaborating a clinical tool to assess cognitive functions in brain-damaged patients, we had previously displayed characteristic patterns of ERPs (32 electrodes) in awake healthy persons in response to their own name (SON) presented as a novel in a passive oddball paradigm. In the present combined ERP and PET study, in an attempt to identify brain correlates of duration MMN and response to SON uttered by a familiar (FV) or an unknown voice (NFV), we used a block design protocol as close as possible to the aforementioned SON protocol. ERP data showed robust duration MMN and novelty P3 in response to SON similar to our previous results. The PET technique did not allow true MMN generators to be disclosed, but blocks with duration deviants elicited an increase of activation in the right temporal pole as compared with the control condition with no deviants, supporting the hypothesis of right hemispheric dominance in early sound discrimination. For SON contrasts, robust cerebral blood flow activation present over temporal, frontal and parietal cortices, in the hippocampus and in the precuneus could be associated with speech, novelty and self-recognition processing. Familiar and unfamiliar voices activated the prefrontal cortex differently, suggesting different retrieval processes, although corresponding ERP responses could not be differentiated.

For comatose patients in intensive care units, it is important to anticipate their functional outcome as soon and as reliably as possible. Among clinical variables the Glasgow Coma Score (GCS) and the patient's pupil reactivity are the strongest predictive variables. Evoked potentials help to assess objectively brain function. Over the past 20 years, numerous studies have assessed their prognostic utility in terms of awakening from coma. Fewer studies, however, have focused upon the utility of evoked potentials in predicting progression to the vegetative state. In this area evoked potentials appear to have a highly predictive value. In anoxic coma the abolition of somatosensory evoked potentials (SEPs) is related to a poor outcome, defined as death or survival in a vegetative state, with a 100% specificity. Following traumatic brain injury, the predictive value for unfavourable outcome is 98.5% when there are no focal injuries likely to abolish SEP cortical components. In contrast, the presence of event-related evoked potentials, and particularly mismatched negativity (MMN), is a strong predictor of awakening and precludes comatose patients from moving to a permanent vegetative state (PVS).

Luaute J, Fischer C, Adeleine P, Morlet D, Tell L, Boisson D. Late auditory and event-related potentials can be useful to predict good functional outcome after coma. Objective To investigate whether late auditory and event-related potentials, and in particular N100 and mismatch negativity, together with clinical parameters, can help to predict good functional outcome in comatose patients. Design Prospective cohort study. Setting Hospital. Participants Consecutively sampled comatose patients (N=346) whose etiologies of coma were stroke (125 patients), brain injury (96 patients), anoxia (64 patients), complication of neurosurgery (54 patients), and encephalitis (7 patients). Interventions Not applicable. Main outcome measures Glasgow Outcome Scale score at 1 year postonset. Patients in a minimally conscious state and those who awoke and died during the follow-up period were classified separately. Results Univariate analysis showed that all variables studied, except brainstem auditory evoked potentials, correlated significantly with functional outcome. Mismatch negativity showed the highest positive predictive value for good outcome. A validated model was obtained with multivariate logistic analysis, including pupillary light reflex, N100, mismatch negativity, etiology, and age. Conclusions Late auditory and event-related potentials, and particularly N100 and mismatch negativity, provide strong prognostic factors for good functional outcome. Furthermore, these components may enhance the accuracy of prognosis when associated with other clinical parameters available at the early stage of coma.

The authors studied the relation between seizure-associated nose wiping (NW) and intracerebral EEG data in 32 patients. NW was more frequent in mesial temporal lobe seizures (TLSs; 65%) than in other TLSs (36%; p < 0.05) and in frontal lobe seizures (3%; p < 0.0001). It was associated with the presence of an amygdala discharge at seizure onset (p < 0.05) and with the recording of an ictal low-voltage fast activity within that structure (p < 0.05), supporting the role of an amygdala dysfunction in the pathophysiology of NW.

We studied the existence, localization and attentional modulation of gamma-band oscillatory activity (30--130 Hz) in the human intracranial region. Two areas known to play a key role in visual object processing: the lateral occipital (LO) cortex and the fusiform gyrus. These areas consistently displayed large gamma oscillations during visual stimulus encoding, while other extrastriate areas remained systematically silent, across 14 patients and 291 recording sites scattered throughout extrastriate visual cortex. The lateral extent of the responsive regions was small, in the range of 5 mm. Induced gamma oscillations and evoked potentials were not systematically co-localized. LO and the fusiform gyrus displayed markedly different patterns of attentional modulation. In the fusiform gyrus, attention enhanced stimulus-driven gamma oscillations. In LO, attention increased the baseline level of gamma oscillations during the expectation period preceding the stimulus. Subsequent gamma oscillations produced by attended stimuli were smaller than those produced by unattended, irrelevant stimuli. Attentional modulations of gamma oscillations in LO and the fusiform gyrus were thus very different, both in their time-course (preparatory period and/or stimulus processing) and direction of modulation (increase or decrease). Our results thus suggest that the functional role of gamma oscillations depends on the area in which they occur.

Auditory disorders resulting from focal brainstem lesions are rarely symptomatic. Isolated lesions of the inferior colliculus have previously been reported, whereas no detailed description of a localized involvement of the lateral lemniscus is yet available. We report a unilateral lesion of the lateral lemniscus by a bleeding in a cavernoma. Symptoms included strictly contralateral tinnitus and auditory impairment, with normal pure-tone and speech audiometry. Conversely, the dichotic listening test revealed an extinction of contralateral ear input. The brainstem auditory evoked potentials disclosed a reduced and delayed wave V only after contralateral ear stimulation, while the middle latency evoked potentials were normal. This observation shows that a unilateral lesion of the lateral lemniscus can produce auditory symptoms. The dysfunction of auditory pathways is associated with specific electrophysiological abnormalities that can be assessed by evoked potential recording.

Publisher Summary This chapter presents a prospective study of 346 comatose patients, to study and confirm the known interest of short-latency evoked potentials (EPs), to determine if late (N 100) and cognitive mismatch negativity (MMN) auditory evoked potentials (AEP) have an awakening prognostic value better than the short-latency EPs alone. The patients belonging to the categories of recovery, moderate disability, severe disability, minimally responsive state, or unrelated death are classified as awakening. Patients in a vegetative state, persistent coma, or death categories are classified as no awakening. This study, based on a large prospective series, shows the interest to record late AEPs and cognitive EPs in the awakening prognostic. Ten patients with MMN failed to regain consciousness. In this study, 80.3% of the comatose patients in whom the N100 component was present finally awoke. The study confirms the interest of the short-latency evoked potentials in the functional evaluation of comatose patients.

Objectives: To determine the prognostic role of late auditory (N100) and cognitive evoked potentials (MMN) for awakening in a cohort of comatose patients categorized by etiology. Methods: The authors prospectively studied a series of 346 comatose patients. Coma was caused by stroke (n = 125), trauma (n = 96), anoxia (n = 64), complications of neurosurgery (n = 54), and encephalitis (n = 7). Patients were followed for 12 months and classified as awake or unawake. Univariate and multivariate analyses were performed using regression logistic and Cox models. Results: Pupillary light reflex, N100, middle-latency auditory evoked potentials, age, and etiology were the most discriminating factors for awakening. Statistical analysis showed that pupillary reflex was the strongest prognostic variable for awakening (estimated probability 79.7%). The estimated probability of awakening rose to 87% when N100 was present and to 89.9% when middle-latency evoked potentials (MLAEPs) were present. It was 13.7% when pupillary reflex was absent in anoxic patients. When MMN was present, 88.6% of patients awakened. No patient in whom MMN was present became permanently vegetative. Conclusion: Pupillary reflex is the strongest prognostic variable, followed by N100 and MLAEPs allowing a reliable model for awakening. The presence of MMN is a predictor of awakening and precludes comatose patients from moving to a permanent vegetative state. Evaluation of primary sensory cortex and higher-order processes by middle-latency-, late, and cognitive evoked potentials should be performed in the prognosis for awakening in comatose patients.

Experiments in animals have shown that the temporal pole and the amygdala are involved in auditory processing. Comparable data are scarce in humans. It is only known that after temporal lobectomy, hearing may be impaired and dichotic listening scores reduced on the ear contralateral to the operated temporal lobe. Middle-latency auditory evoked potentials (MLAEPs) and late auditory evoked potentials (LAEPs) have been recorded in 14 patients before and after temporal lobectomy for the treatment of drug-resistant temporal lobe epilepsy. The Na and Pa components of MLAEPs were significantly delayed and the Pa component amplitude reduced before and after surgery as compared to a group of 21 healthy subjects. Data in pre- and postoperative period were not statistically different. N100 and P200 component of LAEPs were similarly altered. It is concluded that in humans the amygdala and probably the temporal pole may be involved in the process of auditory activation-inhibition. The possible role of auditory processing impairment in cognitive deficits in TLE patients can also be questioned.

We describe documented simultaneous intracerebral auditory evoked potentials from the auditory cortex and medial geniculate body (MGB) of a human patient. The MGB response lasted300 ms, with an initial negativity at 13.5 ms (N13), two positive peaks P21 and P29, and two broader negativities N50 and N200. P21 and N50 amplitudes were strongest for lowest tone frequencies, suggesting possible MGB tonotopic organization. Thalamic peaks were strongly interlaced with cortical activities recorded in Heschl's gyri before 30 ms: N13 preceded the first cortical component by 3.5 ms, then P21 and P29 preceded and lagged, respectively, the following two cortical polarity reversals by 1.5-2 ms. This study provides new functional data on the human MGB, and supports a more complex than simply relay-like role of the thalamus in sound perception.

Objective To describe sonographic findings in livers of pregnant women with severe preeclampsia and abdominal pain. Methods Over a 12-month period, we performed serial sonographic examinations on 32 pregnant women with severe preeclampsia and acute right upper quadrant and epigastric pain. On each sonogram we observed the liver size and texture, "periportal halo" sign, gallbladder wall, Glisson capsule thickness, painful compression of the liver and gallbladder, and ascites. The pancreas, spleen, kidneys, and uterus were also studied. Sonography was repeated after delivery. Results Initial sonograms showed liver abnormalities in 28 patients. Abnormalities consisted of liver hypertrophy (n = 24), hyperechoic thickening of the periportal area (periportal halo sign; n = 23), striated thickening of the gallbladder wall (n = 27), hyperechoic thickening of the Glisson capsule (n = 11), liver areas of increased echogenicity (n = 11), subcapsular hematoma (n = 1), and subcapsular calcification (n = 1). Probe compression of the liver enhanced abdominal pain (n = 13), whereas the gallbladder was painless in all cases. No gallbladder stones were detected. Ascites (n = 16) and pleural effusion (n = 11) were also present. In no case did we detect abnormalities of the pancreas, kidneys, or spleen. All patients eventually had hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome according to the American College of Obstetricians and Gynecologists classification. In 7 cases, HELLP syndrome developed postpartum. Three patients also had eclampsia. Follow-up sonograms highlighted quick regression of abnormalities after delivery. Conclusions The livers of women with severe preeclampsia who had HELLP syndrome showed sonographic abnormalities before biological abnormalities. Serial sonographic examinations could therefore contribute to the obstetric care of these women. Preeclampsia and HELLP syndrome should be routinely checked for in all pregnant women with acute abdominal pain.

Publisher Summary Coma is a state of apparently absent or suspended consciousness, complicating various clinical conditions, for example, circulatory arrest or head trauma. In recent times, interest is growing in the assessment of coma and in predictors of awakening and recovery. With respect to auditory evoked potentials short-latency responses (BAEPs) that explore the brainstem and middle-latency responses (MLAEPs), exploring the primary auditory cortex, have been used more often than late auditory evoked responses. It is only recently that event-related potentials (ERPs) have been studied in comatose patients. The use of P300 in comatose patients is questionable, as it is closely related to attention and decision-making. Recording mismatch negativity (MMN), in comatose patients, is more suitable, as it can be elicited in the absence of attention— that is, when no task performance is required —and it is best recorded in conscious subjects, using a passive condition in which attention is directed away from the auditory stimulation. The MMN is mainly generated by the auditory cortex. It depends on the presence of a memory trace formed by the preceding standard stimulus. The chapter describes and discusses the procedure and the result, respectively, of a few studies in detail that have dealt with MMN recording results in comatose patients.

In humans, administration of benzodiazepines (BZD) has been shown to have an asymmetrical effect on the medial olivocochlear system. Indeed, a decrease of evoked otoacoustic emission suppression by contralateral acoustic stimulation, which explores the medial olivocochlear efferent system, was observed in the right ear, with no left ear effect. This result suggests a possible left-right auditory pathway BZD receptor asymmetry. Given the anatomical link between auditory centers and the medial olivocochlear system, the existence of a larger volume of cortical connecting fibers in the left hemisphere, and the possible link between BZD receptor density and neuronal density, we tested the hypothesis of an asymmetrical localization of BZD receptors in the auditory system in 10 right-handed subjects using [ 11 C]flumazenil positron emission tomography. Semi-quantitative measurements of flumazenil binding were evaluated in Heschl's gyrus showing a left-right asymmetry in favor of left auditory cortex. This result indicates a higher density of neurons in left auditory cortex. The possible link between neurochemical asymmetry and functional asymmetry, and the perceptual outcome of BZD administration, will be discussed.

Mismatch negativity (MMN) and N100 auditory evoked potential were recorded in 52 healthy subjects and in 128 severely comatose patients. The MMN was present in 33/128 patients and N100 in 84/128. A ratio of 30/33 patients with MMN and 70/84 with N100 regained consciousness in a mean time of 6.3 ± 4 days after the recording session. Thus, in terms of predicting return to consciousness, the MMN was more specific (90.9%) than the N100 (57.6%), but its sensitivity was lower (31.6% for MMN and 73.7% for N100, respectively). The amplitudes of MMN and N100 in comatose patients were smaller than those of healthy subjects. It is concluded that MMN and N100 can be very useful in predicting whether or not a comatose patient will regain consciousness.

Objective: The aim of this study was to determine the course of the temporal optic radiations. Material and Methods: Eighteen patients were included in this prospective study. All of them underwent a temporal lobectomy for epilepsy, including the mesial temporal structures and a variable extent of lateral neocortex (from 2 to 7 cm behind the temporal tip). An MRI was performed 2 months postoperatively, allowing assessment of the extent of lateral resection. Postoperative visual fields were determined by automatic static perimetry (ASP). Results: (1) No patient complained of a disabling visual field deficit. (2) ASP, a highly sensitive technique, however, detected postoperative visual field deficits in 83% of patients, confined to the superior homonymous field contralateral to the resection. (3) A strong correlation was found between the presence of a visual field deficit and the extent of laterotemporal resection. (4) The smallest anteroposterior resection resulting in a field defect was limited to 20 mm from the temporal tip. Conclusion: (1) This study confirms a strong correlation between postoperative visual field deficits and the extent of lateral neocortical temporal resection. (2) The anterior limit of Meyer’s loop is likely to be located more rostrally than previously believed. (3) Despite this, lateral resection remains useful in some cases for seizure control.

Summary: Purpose: This study explored the mechanism of light-induced complex partial seizures by using ictal intracerebral recordings in a patient with refractory epilepsy of the right temporal lobe. Methods: Presurgical evaluation of this patient was realized by means of video-EEG recordings, WADA test, magnetic resonance imaging (MRI), F”-deoxyglucose and C’ Iflumazenil positron emission tomography (PET) interictal neuroimaging data, and stereoelectroencephalographic (SEEG) ictal recordings. Results: SEEG investigations demonstrated the right mesiotemporal origin of all the patient’s seizures. This result was confirmed by a successful right temporal lobectomy. Moreover, SEEG recordings revealed a frequent interictal spiking activity in the right occipital visual cortex that was undetectable on scalp recordings. However, the occipital cortex was not involved at the onset of mesiotemporal ictal discharges and was not hyperresponsive to focal electrical stimulation. Conclusions: This study shows that, in spite of interictal occipital spiking, the photosensitivity of mesiotemporal seizures can be observed in both the absence of occipital cortex involvement during ictal discharges and demonstrable hyperexcitability of the occipital cortex to light or direct electrical stimulation. Key Words: Light-induced seizures-Temporal lobe epilepsy-SEEG-Epilepsy surgery.

Experience in the use of intraoperative monitoring of brainstem auditory evoked potentials (BAEPs) to relieve hemifacial spasm (HFS) in 42 patients is reported. No patient was deaf before surgery. Postoperatively, one patient (2.3%) was totally deaf. Mean preoperative pure tone average (PTA) was 12.5 ± 9.2 dB. Mean postoperative PTA was 20.5 ± 18 dB (p 1 ms (18 cases). In 15 cases changes were negligible. The main concern in BAEP monitoring was to identify significant changes of the response waveform, latencies and amplitudes on-line, and to give functional warnings to the surgeon so that he or she could modify his or her maneuvers and thus prevent deterioration of the auditory pathway. It is concluded, as it has been in other studies, that intraoperative BAEP monitoring during microvascular decompression to relieve HFS reduces the risk of postoperative deafness.

Human brain stem auditory evoked potentials (BAEPs) recorded from the scalp are a series of potentials corresponding to the sequential activation of peripheral, pontomedullary, pontine, and probably midbrain portions of the auditory pathways.

Thiobacillus tepidarius (type strain) was grown in microaerophilic conditions, on tetrathionate, thiosulfate or crystalline So. The rates of tetrathionate, thiosulfate, elemental sulfur (So) and sulfite oxidation of the different cultures were measured respirometrically, using exponentially growing cells, with an oxygen electrode. Cells growing on the three different sulfur compounds retain thiosulfate-, tetrathionate, and So-oxidizing activities (SOA), but lack respiratory sulfite-oxidizing activity. The SOA for all the cultures was almost totally inhibited by 50 μM myxothiazol, an inhibitor of the quinone-cytochrome b region, and by 10 μM of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). Tetrathionate- and thiosulfate-oxidizing activities were moderately and weakly inhibited by 50 μM totally inhibited (>95%) all respiratory activities. This study suggests that electrons released by So oxidation enter the respiratory chain in the quinone-cytochrome b region.

Summary: Single-photon emission computed tomography (SPECT) and [99mTc]HMPAO were used to assess the functional significance of nonspecific magnetic resonance imaging (MRI) abnormalities observed in patients with temporal lobe epilepsy and no focal lesion on CT scan. We studied 18 patients whose MRI was normal or showed high signal intensity on T2-weighted images (T2WIs) at the site of the EEG focus in 11 and 7 cases, respectively. EEG was monitored during regional cerebral blood flow (rCBF) study. Lateralized hypoperfusion was present in 7 of 17 interictal(41%) and in one Postictal cases; it was located in the temporal lobe on the side of the EEG focus in all, and was significantly more frequent in patients with high signal intensity on T2WI (86%) than in patients with a normal MRI (18%). The degree of temporal perfusion asymmetry measured in each individual was higher in patients whose MRI was abnormal. RESUME Le SPECT AU Tc 99m-HMPAO a ete utilise pour evaluer la signification fonctionnelle d'anomalies non specifiques a I'IRM retrouvees chez des patients presentant une epilepsie du lobe temporal en l'absence de lesions focales a la scanographie. Les auteurs ont etudie 18 patients presentant une IRM normale ou presentant des images de haute intensite en T2 pondere au niveau du site du foyer epileptique (I 1 et 7 cas respectivement). L'EEG a ete enregistre pendant I'etude du flux sanguin cerebral regional. Une hypoperfusion lateralisee etait presente en etat intercritique 7 fois sur 17, et dans un cas evaluee en postcritique. Elle etait localisee au niveau du lobe temporal du cote du foyer EEG dans tous les cas, elle etait significativement plus frequente chez les patients presentant un signal de haute intensite en T2 pondere (86%) que chez les patients presentant une IRM normale (18%). Le degre d'asymetrie de perfusion temporale mesure chez chaque patient etait plus eleve chez les patients avec IRM anormale. RESUMEN Para determinar el significado funcional de las anormalidades inespecificas que aparecen en la Resonancia Magnetica (MRI) de pacientes con epilepsia de 1obulo temporal y sin lesiones focales en la Tomografia Computarizada, se han utilizado la Tomografia Computarizada por Emision de Fotonsimple (SPCT) y TC 99M-HMPAO. Hemos estudiado 18 pacientes en los que la MR fue normal o mostro senales de aka intensidad en las imagenes T2 (T2WI) en el lugar del foco del EEG en 11 y 7 casos respectivamente. El EEG fue monitarizado durante estudios de flujo cerebral regional (rCBF). Se encontro una hipoperfusion lateralizada en 7 de 17 casos interictales (41%) y en 1 postictal que se localizo en el 1obulo temporal del lado del foco del EEG en todos los casos y fue significativamente mas frecuente en pacientes con alta senal de intensidad en TZWI (86%) que en pacientes con una MRI normal (18%). El grado de asimetria de la perfusion temporal fue medido en cada individuo y fue mayor en 10s pacientes en 10s que la MRI fue anormal. ZUSAMMENFASSUNG Single-Photon-Emissions-Computertomographie (SPECT) und Tc99m-HMPAO wurden zur Untersuchung der funktionellen Signifikanz nicht spezifischer magnetresonanztomographischer Abnormitaten benutzt, die bei Patienten mit Temporallappenepilepsie und fehlenden fokalen Lasionen im CT gesehen wurden. Wir untersuchten 18 Patienten, deren MRT normal war (11) oder eine hohe Signalintensitat in der T2-Gewichtung auf der Seite des EEG-Fokus (7 Falle) zeigte. Das EEG wurde wahrend der regionalen zerebralen Blutfluβuntersuchung (rCBF) abgeleitet. Eine lateralisierte Hypoperfusion trat bei 7 von 17 Pattienten (41%) interiktal auf, bei einem Patient postiktal; sie war bei allen Fallen im Temporallappen auf der Seite des EEG-Fokus lokalisiert und war bei Patienten mit hoher Signalintensitat im T2-Bild signifikant haufiger (86%) als bei Patienten mit normalem MRT (18%). Das Ausmaβ der temporalen Perfusionsasymmetrie war hoher bei Patienten mit abnormem MRT.

How do we keep an object in mind? Based on evidence from animal electrophysiology and human brain-imaging techniques, it is commonly held that short-term memory relies on sustained activity in a network distributed over sensory and prefrontal cortices. How does neural firing persist in such a distributed network in the absence of visual input? Hebb's influential but so far unproved proposal, developed more than 50 years ago, is that sustained activation in short-term memory networks is maintained by reverberating activity in neuronal loops. We hypothesized that synchronized oscillatory activity, proposed to provide a dynamic link between distributed areas, could not only coordinate activity in the network but also establish reentrant loops in the system to enable both sustained firing and temporal coincidence of inputs. We show in human intracranial recordings that limited regions of extrastriate visual areas, separated by several centimeters, become synchronized in an oscillatory mode during the rehearsal of an object in visual short-term memory. Synchrony occurs specifically in the beta range (15-25 Hz) and disappears in a control condition. These findings thus confirm experimentally the hypothesis of a functional role of synchronized oscillatory activity in the coordination of distributed neural activity in humans, and support Hebb's popular but unproved concept of short-term memory maintenance by reentrant activity within the activated network.