Biomedical subjects

P Ryvlin

Publications and source records attributed to P Ryvlin.

At least 37 records · Page 2Linked to original sources

PubMed2001

Odorants elicit evoked potentials in the human amygdala.

Electroencephalographical (EEG) recording studies have shown that odorants produce olfactory evoked potentials (OEPs) on the scalp surface. However, EEGs can only provide limited information about the intracerebral sources from where the OEPs are generated. By contrast, intracerebral EEG recordings enable direct examination of the electrophysiological activity from a given cerebral area. In the present study, neural activity was recorded from the amygdala of seven epileptic patients undergoing intracerebral EEG recordings prior to surgical treatment for relief of intractable seizures. Two olfactory tests were used: a passive-stimulation test consisting of the successive presentation of 12 common odorants and a suprathreshold detection test including both odorant and non-odorant stimulations. Recordings from the amygdala revealed that all odorant stimulations induced large and reproducible OEPs, whereas the non-odorant stimulations did not. It was also found that repetition of the same odorant stimulation led to a decrease in the latency of the first OEP component. This modulation, which corresponds to a faster olfactory processing, strongly suggests that the amygdala is involved in early olfactory attentional processes. In conclusion, it appears that the human amygdala discriminates the incoming information from the nasal airflow as being odorant or not and, additionally, that its speed of processing is sensitive to recent experience with an odor.

Adolescent↗

PubMed2001

Neurophysiological monitoring for epilepsy surgery: the Talairach SEEG method. StereoElectroEncephaloGraphy. Indications, results, complications and therapeutic applications in a series of 100 consecutive cases.

OBJECT OF THE STUDY: In some candidates for epilepsy surgery in whom the decision to operate is difficult to make, invasive presurgical investigations, namely depth electrode recordings, may be needed. The SEEG (StereoElectroEncephaloGraphy) method consists of stereotactic orthogonal implantation of depth electrodes (5 to 15, 11 on average). The object of this study is to clarify the indications for SEEG, to expose its complications, and to display its usefulness in terms of surgical strategy and results. PATIENTS AND METHODS: 100 patients, suffering from drug-resistant epilepsy and selected as candidates for surgical resection, underwent SEEG between 1996 and 2000. A total of 1,118 electrodes were implanted. For each single case, the sites of implantation of the electrodes were chosen in order to determine either the side of the onset of seizures, or the uni- or multilobar feature of them, or a possible operculo-insular propagation from a temporal onset, and also, using direct electrode stimulation, the proximity of speech or motor area. RESULTS: Complications occurred in 5 patients (2 superficial infections, 2 breakages of electrodes, and 1 intracerebral hematoma responsible for death). SEEG was helpful in most (84%) of the 100 patients to confirm or annul surgical indication, and to adjust the extent of the resection. In some cases (14%), SEEG allowed to propose a resection that might have been disputable based solely on noninvasive investigation data. For frontal epilepsy, SEEG was crucial in all cases to delineate the extent of resection. CONCLUSION: SEEG proved to be a relatively safe and a very useful method in 'difficult' candidates for epilepsy surgery. In addition, in some cases the implanted electrodes can be used to perform therapeutic RF thermocoagulation of epileptic foci or networks.

Adult↗

PubMed2000

Towards an optimal reference region in single-photon emission tomography difference images in epilepsy.

There is marked variability in the cerebral blood flow (CBF) between the ictal and interictal state in epilepsy, and it would therefore be desirable to increase the reliability of ictal/interictal single-photon emission tomography (SPET) difference images. We aimed to improve the step of quantitative normalization of images by finding the best possible reference region. In 16 patients (11 with lateralization of the epileptogenic focus, five with bilateral foci) both ictal and inter-ictal SPET scans were performed after injection of technetium-99m labelled tracer. Then, each region among a selected set (brain+cerebellum, brain, cerebellum, hemispheres, and for patients with an expected lateralization, cortical lobe containing the focus and symmetrical contralateral lobe) was investigated by comparison of the regional ictal/inter-ictal variance in counts. Among patients with a suspected lateralized focus, the distribution of CBF in the contralateral cortical lobe appeared to vary less between ictal and inter-ictal states than in other investigated areas. As a consequence, this latter region constitutes the best choice as a reference region. For patients with bilateral foci, the cerebellum appears to be a good compromise even though it presents with significant CBF changes.

Brain↗

PubMed2000

Functional mapping of the insular cortex: clinical implication in temporal lobe epilepsy.

PURPOSE: We report the results of 75 intracortical electrical stimulations of the insular cortex performed in 14 patients during stereo-electroencephalography (SEEG) investigation of drug-resistant partial epilepsy. The insular cortex was investigated on electroclinical arguments suggesting the possibility of a perisylvian spread or a rapid multilobar diffusion of the discharges during video EEG. METHODS: In these 14 patients, 27 stereotactically implanted transopercular electrodes reached the insular cortex (11 the right insula, 16 the left insula). Square pulses of current were applied between the two deepest adjacent contacts of each transopercular electrode using low (1 Hz) or high-frequency (50 Hz) stimulation. Only symptoms evoked in the absence of afterdischarges were analyzed. RESULTS: Clinical responses were evoked in 10 of the 14 patients (in 20 of the 27 insular sites) and showed a clear topographic specificity inside the insular cortex. Viscerosensitive and visceromotor responses, similar to those evoked by temporomesial stimulation, were evoked by anterior insular stimulation and somesthetic sensation, similar to those evoked by opercular cortex stimulation, by posterior insular stimulation. CONCLUSIONS: The topographic organization of the induced responses within the insular cortex suggest that two different cortical networks, a visceral network extending to the temporomesial structures and a somesthetic network reaching the opercular cortex, are disturbed with stimulation of the anterior or the posterior insula, respectively. Thus ictal symptoms associated with the spread of the epileptic discharges to the insular cortex might be difficult to distinguish from those usually reported during temporomesial or opercular discharges.

Adult↗

PubMed1999

Transient and falsely lateralizing flumazenil-PET asymmetries in temporal lobe epilepsy.

We have observed a falsely lateralizing mesial temporal [11C]-flumazenil binding asymmetry in three patients who had temporal lobe epilepsy (TLE) with normal hippocampal volumes. This abnormality was not detected 3 months later in two of the patients who underwent a second PET study. We conclude that transient and falsely lateralizing changes of flumazenil binding might occur in patients with TLE and no hippocampal sclerosis.

Adult↗

PubMed1999

Painful seizures with allodynia in an 11-year-old boy.

An 11-year-old boy's epileptic seizures started with a feeling of impending crisis, dizziness, headache, and a bad taste in the mouth. This was followed by swallowing and a burning sensation in the left hand. At the same time, other parts of the body experienced allodynia. MRI and CT scans showed a right anteromesial temporal lesion which proved at neuropathology to be a ganglioglioma. Lesionectomy resulted in complete cessation of seizures. Seizures were absent at an 18-month follow-up. Allodynia is discussed in relation to the locality of the lesion.

Child↗

PubMed1999

MRI assessment of the anatomy of optic radiations after temporal lobe epilepsy surgery.

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.

Adult↗

PubMed1998

[Recurrent Mollaret's meningitis of herpetic origin].

BACKGROUND: Benign recurrent meningitis, or Mollaret's meningitis, is an uncommon disease whose viral origin was long unidentified. Since 1991, about twenty cases have been reported in patients with herpes infection. CASE REPORT: A female patient had experienced repeated episodes of spontaneous meningitis since 1983. The episodes resolved spontaneously and no etiology had been identified. A spinal tap was performed when the patient was again hospitalized a new episode of meningitis and PCR amplification of the herpes simplex virus type 2 (HSV 2) was positive. The patient was given long term acyclovir per os. A new spinal tap after resolution of the meningitis episode was PCR HSV2 negative. DISCUSSION: HSV2 infection is one of the known causes of Mollaret's meningitis. Long-term antiviral therapy appears to prevent recurrence as was observed in our patient.

Acyclovir↗

PubMed1998

Course of valvular strands in patients with stroke: cooperative study with transesophageal echocardiography.

BACKGROUND: Native valve strands might be related to the acute stage of thrombosis or might suggest a long-term valvular change. We aimed to estimate changes in the strands in patients with stroke through a serial transesophageal echocardiographic (TEE) study. METHODS AND RESULTS: A study was conducted among patients who were referred for TEE for stroke or cardiac pathology. Patients had TEE examinations with a 5-MHz multiplane TEE probe. Echocardiography was repeated 3 months later in patients with stroke. TEE was performed in 180 patients admitted to cardiology units and in 160 patients referred to neurology units. Among 34 patients with valvular strands, 30 were referred to neurology for stroke, whereas 4 patients were admitted to cardiology (18.8% versus 2.2%, difference 16.5%, 95% confidence interval 10% to 22.9%, P =.001). Strands were located on the mitral valve in 16 patients, the aortic valve in 6 patients, and both left heart valves in 8 patients. Among the 38 valves with strands, 17 (44. 7%) were morphologically normal, 4 (10.5%) were thickened, 7 (18.4%) were redundant, and 10 (26.3%) had both abnormalities. TEE showed other abnormalities in 16 (53.3%) patients, whereas 14 patients had only strands. Twenty-six (86.6%) patients had a second TEE study 3 months later. Strands were not found in 4 (15.4%) patients (95% confidence interval 4.3% to 34.9%). CONCLUSIONS: Valvular thickening or redundancy may predispose valves to strand formation. Native valve strands usually persist and thus reflect a chronic valvular change.

Adolescent↗

PubMed1998

Topographical reliability of mesio-temporal sources of interictal spikes in temporal lobe epilepsy.

PURPOSE: Localization of hippocampal paroxysmal activities in temporal lobe epilepsy (TLE) by means of dipole modeling has often been criticized because of the supposed inaccuracy of this technique in localizing deep sources of EEG signals. This study aimed at assessing the relevance of mesio-temporal dipoles, as identified by modeling of scalp recorded spikes in TLE. METHODS: Surface and depth EEG activities were simultaneously recorded using scalp and intracranial electrodes implanted through the foramen ovale (FO) in 3 patients with refractory TLE seizures. Intracranial FO spikes were used as triggers for scalp EEG averaging. The averaged signals were modeled by current dipoles, the localization of which were fused with patients' 3D-MRI. RESULTS: Individual FO spikes were undetectable on visual analysis of raw scalp EEG but were reflected by low-amplitude scalp EEG transients on averaged signal. Dipole modeling of this EEG deflection consistently identified a mesio-limbic source in a position close to that of the FO pole recording the intracranial spike with its maximal amplitude. CONCLUSION: This result suggests that mesio-temporal sources can be accurately localized by modeling the signals recorded on the scalp, thus validating the anatomical and clinical relevance of hippocampal sources identified by modeling scalp interictal averaged spikes in TLE.

Adult↗

PubMed1998

Clinical utility of flumazenil-PET versus [18F]fluorodeoxyglucose-PET and MRI in refractory partial epilepsy. A prospective study in 100 patients.

We assessed the clinical utility of [11C]flumazenil-PET (FMZ-PET) prospectively in 100 epileptic patients undergoing a pre-surgical evaluation, and defined the specific contribution of this neuro-imaging technique with respect to those of MRI and [18F]fluorodeoxyglucose-PET (FDG-PET). All patients benefited from a long term video-EEG monitoring, whereas an intracranial EEG investigation was performed in 40 cases. Most of our patients (73%) demonstrated a FMZ-PET abnormality; this hit rate was significantly higher in temporal lobe epilepsy (94%) than in other types of epilepsy (50%) (P < 0.001). Most FMZ-PET findings coexisted with a MRI abnormality (81%), including hippocampal atrophy (35%) and focal hypometabolism on FDG-PET (89%). The area of decreased FMZ binding was often smaller than that of glucose hypometabolism (48%) or larger than that of the MRI abnormality (28%). FMZ-PET did not prove superior to FDG-PET in assessing the extent of the ictal onset zone, as defined by intracranial EEG recordings. However, it provided useful data which were complementary to those of MRI and FDG-PET in three situations: (i) in temporal lobe epilepsy associated with MRI signs of hippocampal sclerosis, FMZ-PET abnormalities delineated the site of seizure onset precisely, whenever they were coextensive with FDG-PET abnormalities; (ii) in bi-temporal epilepsy, FMZ-PET helped to confirm the bilateral origin of seizures by showing a specific pattern of decreased FMZ binding in both temporal lobes in 33% of cases; (iii) in patients with a unilateral cryptogenic frontal lobe epilepsy, FMZ-PET provided further evidence of the side and site of seizure onset in 55% of cases. Thus, FMZ-PET deserves to be included in the pre-surgical evaluation of these specific categories of epileptic patients, representing approximately half of the population considered for epilepsy surgery.

Brain↗

PubMed1998

[Functional imaging in idiopathic generalized epilepsy].

Positron emission tomography has offered the possibility to investigate the pathophysiology of idiopathic generalized epilepsies. Absence epilepsies demonstrate normal cerebral glucose metabolism and benzodiazepine receptor density. Conversely, juvenile myoclonic epilepsies are associated with frontal hypometabolism, which aggravates during a working memory task. Typical 3 Hz spike and wave discharges lead to a diffuse hypermetabolism. The latter resembles that observed during GAERS rats absences, and clearly differs from the hypometabolism encountered in partial epilepsies associated with generalized spike and wave discharges. Overall, functional imaging data provide further evidence of syndromic specificities in idiopathic generalized epilepsies.

Animals↗

PubMed1997

Brain glucose metabolism with [18F]-fluorodeoxyglucose and positron emission tomography before and after surgical resection of epileptogenic cavernous angiomas.

Surgery of cavernous angiomas is often proposed due to the epileptogenic and hemorrhagic potential of this lesion. Little information is available on the impact of surgical resection on brain metabolism, locally or at a distance from the lesion. Fifteen patients presenting with a cavernoma and epileptic seizures underwent positron emission tomography examinations before and 1 year after surgical resection. We studied the quantitative cerebral metabolic rate of glucose (CMRGlu) with [18F]-fluorodeoxyglucose. The global brain CMRGlu remained unchanged after surgery. There was a significant decrease of metabolism in the lesion hemisphere, which remained unchanged after surgery. The perilesional regions were less metabolic than the contralateral ones and less metabolic than remote regions within the same hemisphere, before and after surgery. The absence of pre- to postsurgical variations suggests that the metabolic consequences of the lesion are maintained despite the surgical procedure during long-term follow-up studies.

Brain↗

PubMed1995

Magnetic resonance imaging evidence of decreased putamenal iron content in idiopathic Parkinson's disease.

OBJECTIVE: To determine the changes in basal ganglia iron content associated with various stages of idiopathic Parkinson's disease. DESIGN: Prospective magnetic resonance imaging study using a 2-T magnet. SETTING: Ambulatory care referral center. PATIENTS AND PARTICIPANTS: Forty-five patients suffering from levodopa-responsive Parkinson's disease and 45 age-matched controls. MAIN OUTCOME MEASURES: The T2 relaxation time calculated in various regions of the basal ganglia, the duration of Parkinson's disease, and the age of subjects. RESULTS: Patients with Parkinson's disease exhibited significantly decreased T2 relaxation time in the pars compacta of the substantia nigra compared with controls (P < .01), regardless of disease duration. Patients with a duration of illness above 10 years (n = 12) exhibited significantly increased T2 relaxation time in the anterior and posterior putamen (P < .005 and P < .01, respectively) and in the pallidum (P < .05) compared with age-matched controls. Putamental T2 relaxation time positively correlated with disease duration (P < .05). CONCLUSION: These results suggest that more complex brain iron changes than those previously reported are associated with idiopathic Parkinson's disease, including increased nigral iron content and decreased putamenal and pallidal iron concentration in patients with a duration of illness above 10 years.

Adult↗

PubMed1995

Interictal cerebral metabolism and epilepsy in cavernous angiomas.

We studied glucose metabolism in brain tissue surrounding cavernous angioma in 22 patients, using PET, and evaluated its relation to the size, site and epileptogenic nature of the vascular malformation, as well as to the post-surgical seizure outcome. Preoperatively, 18 patients suffered recurrent seizures, the origin of which could be clearly related to the vascular malformation in 14. Brain metabolism surrounding cavernous angiomas was normal in 18 patients (82%), and significantly decreased in four (18%). In these four patients, but in none of the 18 other cases, the vascular malformation disrupted connections between paralimbic areas and the adjacent temporal neocortex where hypometabolism was most pronounced. The latter did not correlate with the size nor with the epileptogenic nature of the cavernomas. Sixteen epileptic patients underwent surgical removal of their cavernoma, without resection of the surrounding cortex. At 1-year postoperatively, seizures have relapsed in seven patients (44%), including those four whose epilepsy could not be clearly related to the vascular malformation. Conversely, the four patients with perilesional hypometabolism on preoperative PET were seizure free postoperatively. Hypometabolism in brain tissue surrounding cavernomas is a rare finding which seems more likely to reflect deafferentation than the epileptogenic process itself.

Adolescent↗

PubMed1993

Pontine versus capsular pure motor hemiparesis.

We prospectively studied 21 patients with pure motor hemiparesis (PMH). CT showed a capsular lesion consistent with the clinical syndrome in 15 patients (71%) and was repeatedly negative in the remaining six (29%). In all six patients with repeatedly negative CT, MRI showed a pontine paramedian infarct as the notable cause of PMH. Clinical findings could not definitely distinguish between capsular and pontine PMH, but the combination of dysarthria and a history of previous transient gait abnormality or vertigo favored a pontine location. Outcome at 3 months was characterized by persistent, moderate to severe disability in 86% of patients with pontine PMH versus 46% in capsular PMH. Based on MRI and magnetic resonance angiographic findings, the presumed mechanism of pontine ischemic lesions was a lacunar process in most instances (86%).

Aged↗

PubMed1992

Functional neuroimaging strategy in temporal lobe epilepsy: a comparative study of 18FDG-PET and 99mTc-HMPAO-SPECT.

We performed 99mTc-hexamethylpropyleneamineoxime-single-photon emission computed tomography (SPECT) and 18F-fluorodeoxyglucose-positron emission tomography (PET) in 20 epileptic patients with well-lateralized temporal electroencephalographic focus, normal computed tomographic scan, and brain magnetic resonance imaging (MRI) either normal (n = 10) or showing nonspecific changes in the epileptogenic temporal lobe (n = 10). In patients with a normal MRI, PET exhibited focal hypometabolism in 80%, whereas SPECT showed corresponding hypoperfusion in only 20%. In patients with an abnormal MRI, PET and SPECT yielded 100% and 90% sensitivity, respectively. The metabolic and regional cerebral blood flow disturbances were topographically concordant with electroencephalographic and MRI findings in all these patients. Only patients with a large and pronounced hypometabolism on PET images exhibited hypoperfusion on SPECT. Spatial resolution appeared to be the critical factor responsible for the higher sensitivity of PET. However, this superiority of PET did not prove clinically useful in patients whose SPECT was abnormal, particularly when brain MRI showed nonspecific changes in the epileptogenic temporal lobe.

Adolescent↗

PubMed1991

Metabolic patterns associated with non-specific magnetic resonance imaging abnormalities in temporal lobe epilepsy.

We investigated the cerebral metabolic patterns associated with non-specific hyperintense T2-weighted image on Magnetic Resonance Imaging (MRI) in Temporal Lobe Epilepsy (TLE). Nineteen patients suffering from TLE with a normal CT scan underwent Positron Emission Tomography (PET) using 18F-fluorodeoxyglucose; 8 had hyperintense T2-weighted image on MRI in the epileptogenic temporal lobe and 11 had a normal MRI. Interictally, PET exhibited focal hypometabolism in all the patients with hyperintense T2-weighted image and in 8 of the 11 whose MRI was normal. The hypometabolic area was significantly more extensive in patients with hyperintense T2-weighted image in whom it always encompasses the site of the MRI abnormality. Moreover, these patients had higher metabolic asymmetry index in the temporal and parietal lobes than patients with a normal MRI. One patient with mesial temporal hyperintense T2-weighted image underwent an ictal PET, which showed that the focal hypermetabolism fitted remarkably with the site and size of the abnormal MR signal. Thus, non-specific hyperintense T2-weighted images are associated with particular interictal and ictal metabolic patterns which might suggest that these MRI abnormalities reflect an epileptogenic lesion.

Adolescent↗