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Biomedical subjects

O Mecarelli

Publications and source records attributed to O Mecarelli.

At least 19 recordsLinked to original sources
PubMed2006

Effects of repetitive transcranial magnetic stimulation in a patient with fixation-off sensitivity.

Aim of the present study was to evaluate the acute and long-term effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) on focal epileptiform interictal EEG activity in a patient with fixation-off sensitivity and partial epilepsy. Real and sham rTMS were delivered over the vertex. Two trains of 500 stimuli per day were delivered at 0.33 Hz frequency and threshold intensity for five consecutive days. The number of posterior EEG spikes and spike-and-wave complexes/min before and after the application of rTMS were compared in a blinded manner. In our patient, real-rTMS induced a long-lasting decrease in the number of posterior EEG spikes and spike-and-wave complexes/min. Despite the limitations of a single case report, our study confirms that low-frequency rTMS significantly reduces interictal focal epileptic activity over time.

Adult↗
PubMed2004

Observations on EEG patterns in neurally-mediated syncope: an inspective and quantitative study.

We performed an observational EEG study in 43 patients with neurally-mediated syncope in basal condition and during hyperventilation (HV), and compared it with 32 healthy controls. On blind analysis at rest, EEG was classified as normal in 47% of patients (vs. 94% of controls, P < 0.001). More abundant and pronounced delta-theta activities and alpha slowing were found in patients than in control subjects on both visual inspection and quantitative spectral analysis. During prolonged HV, the EEG remained normal in 21% of patients only. Slow activities became more evident in patients than in control subjects, and intermittent rhythmic delta activity appeared in 40% of syncopal patients. These "pseudoparoxysmal" EEG changes differed from the common slowings induced by HV in adult subjects and were not observed in our control subjects. Moreover, these distinctive EEG changes, a common finding in syncopal patients, could not be confused with epileptiform activity of any kind. Further studies will clarify the pathophysiology of these EEG modifications.

Adult↗
PubMed1999

Systemic lupus erythematosus and myoclonic epileptic manifestations.

Systemic lupus erythematosus (SLE) frequently involves the central nervous system (CNS) and, in fact, epileptic manifestations may be one of the earliest symptoms of SLE. These early occurrences of epilepsy, however, can easily be misdiagnosed as indication of pure epileptic syndrome when the SLE diagnosis is still largely incomplete. We present a young girl who developed myoclonic photosensitive seizures at the onset of the illness, erroneously diagnosed as manifestation of a "pure" epileptic syndrome. Shortly after the onset of an anticonvulsant therapy (lamotrigine), there was a remarkable impairment of the general clinical condition: at that time a diagnosis of SLE was made and a specific treatment began. However, the seizures persisted and evolved toward status epilepticus which needed pentobarbitone therapy in an intensive care unit (ICU). After recovery, the girl gradually got better and during the 23 months of follow-up she received only corticosteroid therapy and did not experience seizures nor SLE relapses.

Anti-Inflammatory Agents↗
PubMed1997

Vigabatrin versus carbamazepine and phenytoin in kainic acid-treated pubescent rats.

The effects of the administration of two doses (1,000 and 1,500 mg kg-1) of gamma-vinyl-GABA (GVG), have been tested in pubescent rats, systemically injected with kainic acid (KA). The changes in spontaneous behaviour before KA injection, the behavioural and epileptic manifestations (Wet Dog Shakes, Limbic Seizures and Status Epilepticus) and the lethality rate caused by KA were taken into account and compared to those observed in controls and in carbamazepine (CBZ) or phenytoin (PHT) treated animals. While GVG appeared to reduce the incidence of the epileptic manifestations and the subsequent mortality, particularly when higher doses of the drug were used, CBZ exerted a proconvulsant action and PHT did not substantially modify the parameters considered. Moreover, GVG, but not CBZ and PHT, induced remarkable sedative effects which disappeared within 48 h. The different anticonvulsant profile of GVG, CBZ and PHT were correlated to their different modes of action, since GVG acts by enhancing the inhibitory GABA-mediated processes, while CBZ and PHT act by reducing the excitatory processes.

4-Aminobutyrate Transaminase↗
PubMed1995

Seizure susceptibility in immature rats with micrencephaly induced by prenatal exposure to methylazoxymethanol acetate.

The administration of the alkylating neurotoxin methylazoxymethanol acetate (MAM) to pregnant rats on day 15 of gestation induces, in the offspring, a marked micrencephaly, characterized by an impaired formation of interneurons at cortical, hippocampal and striatal levels. Since in man developmental CNS malformations are often associated with severe epileptogenic encephalopathies with seizures appearing in the first months or years of life, we have studied the development of kainic-acid- and bicuculline-induced seizures in 15- and 30-day-old rats, prenatally exposed to MAM. Compared to controls, a higher susceptibility to seizures has been found in micrencephalic rats aged 15 days, while no significant differences have been observed in those aged 30 days. It is hypothesized that the cerebral global anatomical dysgenesis caused by MAM underlies the higher seizure susceptibility shown by animals during the first periods of life. Successively, the processes of adjustment occurring between the cerebral regions affected by the neurotoxic action of MAM and the afferent and efferent pathways spared by the substance may re-establish adequate interneuronal relationships and, therefore, a normal convulsive susceptibility.

Age Factors↗
PubMed1995

Prenatal cocaine: seizure susceptibility in rat offspring.

Proconvulsant and convulsant effects of cocaine have been described in various experimental models of epilepsy. We have studied the susceptibility to bicuculline and pentylenetetrazol-induced seizures in developing 10-, 20- and 30-day old rats, gestationally exposed to cocaine. Incidence and latency of appearance of the epileptic manifestations, their evolution toward status epilepticus and successive recovery or death, have been evaluated and compared to the same parameters obtained in control animals of the same ages. Results have demonstrated that 10-day-old rats that had been exposed to cocaine are significantly less sensitive than control animals to the convulsant action of both bicuculline and pentylenetetrazole while no substantial differences between the two groups have been found at the successive ages. It is possible that modifications of various neurotransmitter systems caused by prenatal cocaine exposure modify neuronal excitability at least at early stages of development.

Age Factors↗
PubMed1992

Age-related anticonvulsant activity of NMDA in the rat caudate-putamen.

Striatal pathways are important for modulating the threshold for seizures in the rat forebrain. N-Methyl-D-aspartate (NMDA), an excitatory amino acid derivative and powerful anticonvulsant agent, when injected into the brain, has been shown to protect adult rats against kindling and pilocarpine-induced seizures when injected into the caudate-putamen. The present study examines whether the anticonvulsant action of NMDA in the caudate-putamen varies with age. Bilateral striatal administration of NMDA was effective in suppressing bicuculline-induced seizures in rats older than 23 days of age. The results suggest that striatal pathways involved in the anticonvulsant activity of NMDA in the caudate-putamen are not functionally active in developing rats before the 4th week of life.

Aging↗
PubMed1991

The utility of ambulatory EEG monitoring in typical absence seizures.

In this study 8 hours ambulatory EEG monitoring (A/EEG) was performed in 25 outpatients with electroclinical evidence of absence attacks, in order to evaluate the possibility of objective quantification of the epileptic discharges, their distribution during the daytime and their relationship with evident behavioral correlates. A comparison between data obtained by A/EEG and standard EEG (S/EEG) was also made. The results have shown that: 1) it was possible to perform real quantification of the epileptic discharges only through the A/EEG test; 2) the two peaks of a greater incidence of the epileptic discharges corresponded to the execution of relaxing activities and ones requiring a low level of attentiveness; 3) a large number of epileptic generalized discharges did not exhibit a signal pattern like that of a "seizure", although they were of long duration; and 4) in six patients who showed the normalization of S/EEG and the disappearance of the absences after one month of valproate therapy, A/EEG revealed the persistence of epileptic discharges. These data demonstrate that A/EEG is a very useful technique for the quantification of paroxysmal discharges and that it may be of importance in the management of this kind of epileptic disorder.

Behavior↗
PubMed1991

Effects of carbamazepine on bicuculline- and pentylenetetrazol-induced seizures in developing rats.

The anticonvulsant effect of carbamazepine (CBZ) was examined in 10-, 18- and 25-day-old Wistar albino rats into which bicuculline or pentylenetetrazol had been systemically injected to induce generalized epileptic manifestations typical for the specific age of the animals. The results showed that: a) in developing rats, CBZ appears to be more effective in the pentylenetetrazol than the bicuculline model of epilepsy; b) in both models of epilepsy the efficacy of CBZ increases with the age of the animals; and c) among the various epileptic manifestations, the tonic phase is the most sensitive to the anticonvulsant effect of CBZ. These conclusions are correlated with the different levels of cerebral maturation of the animals, and are discussed with reference to the mechanisms of action of CBZ and bicuculline or pentylenetetrazol.

Animals↗
PubMed1988

Effects of progabide on bicuculline-induced epileptic seizures in developing rats.

The effects of progabide, a direct gamma-aminobutyric acid (GABA) receptor agonist, on bicuculline-induced seizures have been tested in developing rats, ages 7-28 days, to study the correlation between the antiepileptic effectiveness of this drug and the level of functional maturation of the GABAergic system. The incidence, latency of appearance, and behavioral characteristics of the epileptic manifestations, their evolution toward status epilepticus, and the percentage of recovery from status epilepticus have been evaluated in rats that had received a single injection (treatment) or three successive daily administrations (pretreatment) of progabide. The results have been compared with those obtained in a control group of animals in which only bicuculline had been injected. In rats ages 7-14 days the treatment appears to be substantially ineffective in protecting animals against bicuculline seizures and their consequences, probably because of the substantial immaturity of the GABAergic system at birth and during the first days of life. At this age, repetitive administrations of progabide cause a protective anticonvulsant action more remarkable than the single injection, particularly when using the higher doses of the substance. In 15-28-day-old rats, the treatment significantly reduces the lethality from status epilepticus but does not substantially modify the incidence of seizures, their latency of appearance, or their evolution toward status epilepticus. As in younger animals, in these rats also pretreatment is more effective than treatment against bicuculline seizures, whatever dose of progabide is used. At this age, therefore, the anticonvulsant properties of progabide appear to be more remarkable than in the previous age, probably because of a higher level of development of the GABAergic system, according to biochemical data on the GABAergic system ontogenesis.

Aging↗
PubMed1985

Bicuculline- and allylglycine-induced epilepsy in developing rats.

The development of bicuculline- and allylglycine-induced epilepsy has been studied in developing rats (6 to 30 days old). The results showed that during the first period of life, in both experimental models, the behavioral modifications were atypical and poorly correlated to corresponding epileptic EEG changes. Successively, a gradual evolution of the electroclinical patterns was observed, with similar characteristics in both bicuculline- and allylglycine-treated animals. Only from the 3rd week did electroclinical patterns similar to those of adult animals and more specific for the type of the convulsant agent appear. These data suggest that during the 1st 2 weeks after birth, the level of global cerebral immaturity, rather than the type of the epileptogenic substance, is the prominent element in the characterization of epileptic manifestations. From the 3rd week, the more advanced level of anatomical, biochemical, and neurophysiologic maturation of the CNS allows a more selective involvement of various cerebral structures with subsequent well defined epileptic features.

Allylglycine↗
PubMed1984

Status epilepticus and brain maturation.

The development of a limbic and a generalized tonic-clonic form of epilepsy, induced by systemic injections of kainic acid and pentylenetetrazol respectively, has been studied in developing rats. The purpose of this research was to investigate the correlations between the maturational stages of the CNS and the electro-clinical manifestations of epilepsy and status epilepticus. In both models of epilepsy, the electro-clinical patterns of seizures typical of the adult animal were reached as early as the third week of life. During the first weeks, atypical behavioural and EEG epileptic manifestations were observed. An attempt has been made to compare the experimental results with the electro-clinical epileptic signs of the infant, in order to suggest some neurophysiological explanations of the peculiar aspects of infantile epilepsy.

Animals↗
PubMed1983

Intracortical and intrahippocampal injections of kainic acid in developing rats: an electrographic study.

Electrographic patterns induced by neocortical and hippocampal microinjections of kainic acid (KA) have been studied in curarized 4-30-day-old rats. In younger (4-6-day-old) animals, both hippocampal and neocortical KA application induced, with a long delay, the appearance of sequences of slow spikes, simultaneously occurring in the cortex and hippocampus. The same pattern was observed in about 60% of animals 7-9 days old. In the remaining 40% of the rats of this age, epileptic abnormalities, initially localized in the neocortical or hippocampal injection site were obtained. The latter pattern always appeared in 10-14-day-old rats. In some of these status epilepticus was also reached. In older (15-30 days) animals, the hippocampal injection caused the appearance of hippocampal seizures, always evolving into status epilepticus. In neocortically injected animals, cortical bursts of polyspikes appeared, with or without hippocampal involvement. After 40-60 min, typical hippocampal seizures occurred, later leading to status epilepticus. The simultaneous hippocampal and neocortical response observed in younger rats is attributed to a massive activation of the immature brain structures. The focal response seems to be correlated with a maturational process of glutamate and/or kainate receptors at both hippocampal and neocortical levels. This process is completed during the third week, when a typical selective activation of the limbic structures is obtained.

Animals↗
PubMed1982

A simple method for implanting electrodes in freely moving neonatal rats.

A simple method for implanting cortical and subcortical electrodes in very young rats is described, which does not interfere with the behavior of the animal during the experiment. The cortical electrodes are anchored to the skull by a spiral whose first loop is introduced between the inner layer of the skull and the dura mater. The subcortical electrodes have a loop which rests above the skull. Both the spirals of the cortical electrodes and the loops of subcortical electrodes are then embedded in dental acrylic.

Animals↗
PubMed1981

EEG and clinical features in epileptic children during halothane anaesthesia.

Clinical and EEG changes were studied in 12 children affected by infantile cerebral palsy and generalized or focal epilepsy, during and after halothane anaesthesia induced by orthopaedic surgery. The anaesthesia was induced by inhalation of halothane 1.5%, and maintained with halothane 0.5%. During anaesthesia a decrease of the incidence of epileptic abnormalities was observed in 10 patients. In the other 2 children no changes were seen. At the end of surgery, when the anaesthetic was gradually suspended, there was a notable increase of epileptic abnormalities in 4 children. Clinical seizures were never observed during or shortly after surgery. In the majority of the cases, the EEGs performed 1 week later did not show modifications of epileptic abnormalities, as compared to the preoperative EEGs. Only in a few patients the epileptic activity was modified. The data show that halothane anaesthesia can be used in epileptic children without risking activation of seizures.

Anesthesia↗