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Biomedical subjects

L Carmant

Publications and source records attributed to L Carmant.

At least 19 recordsLinked to original sources
PubMed2005

Interaction between the flash evoked SSVEPs and the spontaneous EEG activity in children and adults.

OBJECTIVE: To evaluate the interaction between the steady-state visual evoked potentials (SSVEPs) recorded during the intermittent photic stimulation (IPS) and the spontaneous EEG activities both in children and adults. METHODS: EEG was recorded during the rest and under 5, 7.5, 10 and 12.5 Hz IPS in 41 children between 3 and 16 years and 10 adults. We distinguished between the spontaneous resting EEG spectra, SSVEPs (1st harmonic) and undriven (ongoing) EEG spectra recorded during the IPS. RESULTS: We show that IPS influences spontaneous EEG activity by specifically suppressing or desynchronizing individual posterior dominant resting EEG frequencies (DF) in both children and adults. Further, this highly significant and consistent suppressing effect positively correlates with the SSVEPs amplitude. CONCLUSIONS: Our data suggest that the desynchronization of the spontaneous EEG activity under IPS and the SSVEPs are related to each other. SIGNIFICANCE: These relationships could be interesting to study in pathological conditions where the neural synchronization and the responses to IPS have been shown to be affected, such as epilepsy and schizophrenia.

Adolescent↗
PubMed2005

Impact of childhood epilepsy on reading and phonological processing abilities.

Although children with epilepsy tend to exhibit more reading difficulties than their classmates, no systematic studies have investigated the relationship between these difficulties and epilepsy. As functional neuroimaging studies have implicated both temporal and frontal lobes in the phonological aspect of reading [K.R. Pugh, B.A. Shaywitz, S.E. Shaywitz, et al. Brain 1996;119:1221-38], seizure activity originating in either region could interfere with phonological processing, whereas generalized seizures would not disturb this function as much. To explore this hypothesis, we compared the metaphonological skills of school-aged children with either temporal lobe epilepsy (TLE), frontal lobe epilepsy (FLE), or generalized absence seizures (ABS) with those of healthy controls. While the reading ability of all epileptic children was close to 2 years behind expectations, children with TLE did not differ from the controls on phonological tasks. In contrast, children with FLE exhibited significant deficits, whereas children with ABS showed difficulties restricted to phonemic segmentation. The results suggest that FLE and, to a lesser extent, generalized seizures may interfere with phonological processing, whereas TLE may affect other aspects of reading.

Analysis of Variance↗
PubMed2004

A motor resonance mechanism in children? Evidence from subdural electrodes in a 36-month-old child.

The presence of a neural mechanism matching execution and observation of actions in the adult human brain is well established. In children, however, description of a resonance motor mechanism is still preliminary. In the present study, we recorded electroencephalographic signals from a subdural 64-contact grid electrode in a 36-month-old child with epilepsy. Spectral analysis was performed on sequences where the child drew with her right hand, watched an experimenter drawing with his right hand or was at rest. Contact sites corresponding to sensorimotor areas were discovered where absolute power was decreased during both observation and execution of hand/arm actions. These data suggest the presence of a mirror neuron system early in the developing brain.

Analysis of Variance↗
PubMed2004

Clinical significance of isolated hippocampal volume asymmetry in childhood epilepsy.

This study defines the clinical characteristics and evolution of 16 epileptic children with hippocampal asymmetry (HA) without sclerosis on MRI. The association of a positive family history of epilepsy (11/16), low incidence of febrile seizures (2/16), and benign prognosis (seizure control in monotherapy in 11/16, mean follow-up = 4.3 years, range 1 to 10) suggest a different clinical presentation than patients with mesial temporal sclerosis. Genetic studies of these mostly French Canadian families should help confirm the existence of a distinct syndrome.

Adolescent↗
PubMed2003

The pathological basis of temporal lobe epilepsy in childhood.

OBJECTIVE: To characterize the pathologic findings of temporal lobe epilepsy (TLE) in children undergoing temporal lobectomy for refractory seizures and to correlate these findings with clinical presentation. METHODS: The authors reviewed the charts of all children who underwent anterior temporal lobectomy for refractory TLE from 1979 through 1999. A new neuropathologic analysis was performed blinded to clinical features and outcome. RESULTS: Twenty-two children met inclusion criteria. Mean age at onset of epilepsy was 3 years, 7 months (range 1 month to 10 years). Mean age at surgery was 10 years, 11 months (range 1 to 18 years). All patients had complex partial seizures, 48% with secondary generalization. Most had daily seizures. Auras were reported in 45% of patients. Post-resection follow-up averaged 5 years, 2 months (range 2 to 19 years). Seizure-free status was achieved in 41% of patients, and 14% had residual auras only. The most frequent neuropathologic abnormalities were cortical dysplasia (CD) of the temporal neocortex (14 of 22) and mesial temporal sclerosis (MTS) (12 of the 15 children with available hippocampal tissue). These two findings coexisted in seven children. MTS was associated with extra-hippocampal pathology in 8 of 12 (67%) of the cases. CONCLUSIONS: MTS occurs frequently in association with CD in this population of children. The high incidence of dual pathology could explain the early age of seizure onset and high seizure frequency rate observed. TLE in childhood may constitute a different entity than in adults, from both the clinical and neuropathologic perspectives.

Adolescent↗
PubMed2001

The carbohydrate and caloric content of concomitant medications for children with epilepsy on the ketogenic diet.

BACKGROUND: The ketogenic diet for children with refractory epilepsy requires a strict control of the amount of ingested carbohydrates. This can be altered by medication prescribed for the epileptic syndrome or for intercurrent illnesses. The goal of this paper is to compile the carbohydrate and caloric content of commonly used medications in this population. METHODS: We compiled a list of frequently used medications with the help of Canadian manufacturers and the Compendium of Pharmaceuticals and Specialties. We also tested a worst case scenario calculation based on the weight of the tablet. RESULTS: We list the carbohydrate and caloric content of 790 medications studied. Our worst case scenario gives an over-estimate in all cases, making adjustments based on this calculation in an emergency setting safe. CONCLUSION: We propose this list as a tool for physicians, dietitians, nurses and pharmacists. The list can easily be adjusted, based on local practices and reviewed periodically.

Anti-Bacterial Agents↗
PubMed2000

Immature rat convulsions and long-term effects on hippocampal cholinergic neurotransmission.

Generalized tonic-clonic convulsions were induced on 2 consecutive days by pentylenetetrazol (PTZ) in immature rats (postnatal days 10 and 20), and hippocampal slices were prepared at different intervals post-injection. The anticholinesterase eserine provoked interictal-like discharges in the CA3 area of PTZ-injected rats (19/33), but not in controls (0/15), an effect mimicked by carbachol and reversed by atropine. This enhanced response to eserine was recorded in slices from 25-100% of the PTZ-injected rats, the percentage varying with the age at injection and post-injection interval. These results suggest that seizures in immature brain may have long-term consequences in cholinergic neurotransmission, converting a rise in endogenous ACh into an epileptogenic stimulus, which in turn would presumably facilitate the recurrence of seizures.

Acetylcholine↗
PubMed2000

Stroke in children: the coexistence of multiple risk factors predicts poor outcome.

OBJECTIVE: To characterize the risk factors for stroke in children and their relationship to outcomes. METHODS: We reviewed charts of children with ischemic and hemorrhagic stroke seen at Hopital Sainte-Justine, Montreal between 1991 and 1997. RESULTS: We found 51 ischemic strokes: 46 arterial and 5 sinovenous thromboses. Risk factors were variable and multiple in 12 (24%) of the 51 ischemic strokes. Ischemic stroke recurred in 3 (8%) patients with a single or no identified risk factor and in 5 (42%) of 12 patients with multiple risk factors (p = 0.01). We also found 21 hemorrhagic strokes, 14 (67%) of which were caused by vascular abnormalities. No patient with hemorrhagic stroke had multiple risk factors. Hemorrhagic stroke recurred in two patients (10%). Outcome in all 72 stroke patients was as follows: asymptomatic, 36%; symptomatic epilepsy or persistent neurologic deficit, 45%; and death, 20%. Death occurred more frequently in patients with recurrent stroke (40%) than in those with nonrecurrent stroke (16%). CONCLUSIONS: Multiple risk factors are found in many ischemic strokes and may predict stroke recurrence. Recurrent stroke tends to increase rate of mortality. Because of the high prevalence and importance of multiple risk factors, a complete investigation, including hematologic and metabolic studies and angiography, should be considered in every child with ischemic stroke, even when a cause is known.

Adolescent↗
PubMed1999

ACTH versus vigabatrin therapy in infantile spasms: a retrospective study.

ACTH is the standard treatment for infantile spasms (IS) in North America. Recent reports showed that vigabatrin is a valuable treatment for IS, but comparative studies with ACTH are limited. In this study, we compare the effectiveness of ACTH versus vigabatrin on IS. Our results support that vigabatrin is as effective as and better tolerated than ACTH. Because of their similar efficacy, we believe that vigabatrin should be the first intention drug for the treatment of IS.

Adrenocorticotropic Hormone↗
PubMed1999

Toxicity profile of interferon alfa-2b in children: A prospective evaluation.

The toxicity of interferon (IFN) alfa-2b therapy was prospectively evaluated in 53 children treated from 1991 to 1996 in 2 successive studies of IFN alfa therapy for severe hemangiomas at Sainte-Justine Hospital. Toxicity was generally mild and transient, with grade 1 toxicity occurring in 100% of patients, grade 2 toxicity in 89%, grade 3 toxicity in 58%, and grade 4 toxicity in 17%. Ten of 43 patients available for evaluation had an abnormal neurologic examination. Severe neurotoxicity in the form of spastic diplegia occurred in one patient. In conclusion, IFN alfa therapy is generally well tolerated in children. However, it may rarely be associated with severe toxicity and must be used with caution.

Antineoplastic Agents↗
PubMed1999

Effects of hyperthermia and continuous hippocampal stimulation on the immature and adult brain.

Whether febrile seizures lead to hippocampal necrosis is a question of paramount clinical importance. This study attempted to simulate a complex febrile seizure, compared with hyperthermia (HYP) alone and prolonged seizure alone (produced by continuous hippocampal stimulation (CHS)). Four groups of rats were studied at each of two ages, immature (postnatal day, P20) and adult (P60). Group 1 was subjected to 45 min of HYP (body temperature 40 degrees C) plus CHS, Group 2 received 45 min of HYP alone, Group 3 got 45 min of CHS alone, and Group 4 was sham-handled control rats. Baseline and post-session EEGs were recorded in all groups. Subsequently, brains were examined histologically for evidence of hippocampal damage. Both CHS-treated groups (with and without HYP) exhibited behavioral and EEG seizures while the group undergoing HYP alone did not have seizures. There were no gross histological lesions in any group. Cell counts in regions CA1, CA3, dentate gyrus and dentate hilus did not differ in rats under any condition of hyperthermia and CHS, in either P20 or P60 rats compared to age-matched controls. These results indicate that both immature and mature rodents are resistant to hyperthermic brain damage and raises the question of whether febrile seizures play a role in the genesis of mesial temporal sclerosis.

Aging↗
PubMed1998

Electroencephalographic discharges of temporal lobe seizures in children and young adults.

We investigated the discharge morphology and propagation patterns of electroencephalographic seizures of temporal lobe onset in 21 children and young adults who underwent invasive long-term EEG monitoring (LTM). Of those, 15 subsequently underwent anterior temporal lobectomy. The onset was focal in 63%. The most frequent discharge morphology was low amplitude beta (30%) or rhythmic/semirhythmic theta discharge (30%). Thirteen patients displayed several sequences of propagation with different spreading stages along a fixed path. Initial spreading to the ipsilateral frontal lobe was associated with a higher frequency of secondary generalization than initial spreading to the contralateral temporal lobe (P = 0.18). A comparison of 13 patients older than 18 years of age with 8 patients younger than 14 years showed a trend towards a lower rate of propagating from the temporal lobe (P = 0.13) in the younger age group. Discharge morphology was not correlated with age, focality, or outcome of surgery.

Adolescent↗
PubMed1998

Transient visual symptoms as the initial manifestation of childhood adrenoleukodystrophy.

We report two patients with transient visual symptoms after an acute illness (hypoglycemia and head trauma) who went on to develop a progressive neurodegenerative disease (adrenoleukodystrophy). This report supports the suggestion that environmental factors play a role in the initial expression of the disease and reviews atypical visual manifestations of adrenoleukodystrophy. Proper diagnosis and institution of early treatment before the catastrophic deterioration typical of its natural history requires a high degree of suspicion.

Adrenoleukodystrophy↗
PubMed1998

Role of vigabatrin and lamotrigine in treatment of childhood epileptic syndromes.

PURPOSE: Vigabatrin (VGB) and lamotrigine (LTG) are two new antiepileptic drugs (AEDs) with different mechanisms of action for treatment of refractory epilepsies. Previous reports have indicated efficacy of both drugs in a number of epileptic syndromes. METHODS: We compared these new AEDs drugs to determine their respective efficacy against different types of epileptic syndrome and to develop a rational approach to their use. We reviewed the charts of 105 children, with partial and generalized epilepsies. RESULTS: VGB was to be significantly more effective in children with partial epilepsies, and LTG was more effective in those with generalized epilepsies. CONCLUSIONS: VGB and LTG have different therapeutic profiles. Combination treatment with the two drugs may represent rational polytherapy for patients with epilepsy resistant to treatment with either drug alone or as add-on to other AED treatment.

Adolescent↗
PubMed1997

Clinical characteristics of complex partial seizures: a temporal versus a frontal lobe onset.

The site of origin of complex partial seizures (CPS) is predominantly in the temporal lobe, but frontal, parietal, and occipital lobes may also be involved. In order to correlate clinical behaviours with either a temporal or frontal site of origin, we analysed 211 seizures occurring during invasive monitoring in 26 patients with temporal lobe epilepsy (TLE) and in eight patients with frontal lobe epilepsy (FLE). Although leg movements, defined as thrashing, pedalling and kicking, hand posturing, facial twitching, sitting up, and tonic-clonic movements occurred more frequently in FLE, and hand automatisms were more frequent in TLE, no statistically significant difference was found between the two groups. When analysing only electrographic seizures that did not spread or propagated only to homologous controlateral lobes, leg movements and hand posturing were seen only with FLE, and oral automatisms only in TLE. Seizures of temporal lobe origin were longer in duration and had a higher frequency of auras. We therefore conclude that the reliability of clinical behaviour alone to predict the site of origin of an epileptic discharge is limited when the surface EEG is equivocal or the neuroradiologic evidence of a focus is not clear.

Adolescent↗
PubMed1997

Interneuron-specific Ca2+ responses linked to metabotropic and ionotropic glutamate receptors in rat hippocampal slices.

Glutamate-mediated regulation of intracellular Ca2+ levels was examined in different populations of CA1 interneurons, using confocal microscopy and the Ca2+ indicator fluo 3-AM in rat hippocampal slices. Interneurons in basal [stratum oriens/alveus (OA)] and apical [strata radiatum and lacunosum-moleculare (R/LM)] dendritic layers responded heterogeneously to glutamate. In control medium, OA interneurons responded mostly with oscillatory Ca2+ responses, which consisted of a large Ca2+ transient and successive smaller elevations. R/LM interneurons responded mostly with biphasic responses, characterized by an initial large transient and a secondary prolonged elevation. Other interneurons in both R/LM and OA responded with transient elevations in Ca2+ levels. Ionotropic glutamate receptor antagonists (+/-)2-amino-5-phosphonopentanoic acid and 6-cyano-7-nitro-quinoxaline-2,3-dione reduced peak Ca2+ responses in OA and R/LM cells, and blocked biphasic responses in R/LM interneurons. The metabotropic glutamate receptor antagonist (RS)-alpha-methyl-4-carboxyphenylglycine reduced peak Ca2+ responses only in OA interneurons, and prevented oscillatory responses. In low Ca2+ medium, peak responses were reduced in R/LM but not in OA interneurons, and oscillatory responses were absent. Combination of ionotropic and metabotropic receptor antagonists blocked all glutamate-evoked Ca2+ responses. Activation of different types of glutamate receptors may thus produce heterogeneous Ca2+ signals in subpopulations of CA1 interneurons. Ionotropic receptors may generate biphasic responses in interneurons in apical dendritic layers, whereas combined activation of metabotropic and ionotropic receptors may trigger oscillatory responses in interneurons of basal dendritic layers. These heterogeneous Ca2+ responses indicate that glutamate-mediated Ca2+ processes and second messenger systems differ in subpopulations of hippocampal interneurons and suggest possible postsynaptic functional specialization of interneurons.

Animals↗
PubMed1996

Differential diagnosis of staring spells in children: a video-EEG study.

Staring is frequently a nonepileptic manifestation in children. To differentiate epileptic versus nonepileptic staring, we reviewed clinical and video-EEG findings in 143 patients, aged 5 months to 43 years, monitored for staring episodes. In 79 patients staring was of epileptic origin; 46 had partial seizures and 33 atypical absence. Thirty-five had behavioral staring, 8 psychogenic seizures, 1 a migraine equivalent, and in 20 no staring spells were recorded. In all patients with epileptic staring, epilepsy was suspected clinically. Only 22 of the admissions for behavioral staring and 3 for pseudoseizures were to exclude a possible nonepileptic phenomenon. Review of their clinical histories revealed that certain findings strongly support a nonepileptic origin. In conclusion, a careful clinical history will differentiate between epileptic and nonepileptic staring episodes in most patients. Video-monitoring is helpful to adjust treatment or to exclude nonepileptic events in patients with refractory staring spells.

Adolescent↗