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PubMedDate not supplied

[Functional disorder of the hypothalamic osmoreceptor as the cause of excessive hypernatremia in a girl with absence epilepsy].

BACKGROUND: Chronic hypernatremia is a rare disorder in childhood and normally results from impairment of the water homeostasis. In some cases, chronic hypernatremia is caused by decreased intake of water based on impaired thirst perception. CASE REPORT: We report a girl with microcephaly, partial agenesis of the corpus callosum, mild midface hypoplasia and absence seizures, who presented with severe hypernatremia (serum sodium concentration 189 mmol/l). Though serum osmolality was increased up to 382 mOsm/kg, the girl showed no signs of thirst. After normalization by intravenous fluid therapy, serum osmolality and serum sodium concentration remained in the normal range with an oral water intake of at least 1500 ml/d. Polyuria was never present, the ability to concentrate urine was preserved. CONCLUSIONS: In summary, we speculate that the chronic hypernatremia in our patient is caused by a selective hypothalamic osmoreceptor dysfunction associated with mild dysplasia of the midline structures. Only very few similar cases have been documented in the literature.

Agenesis of Corpus Callosum↗
PubMed2002

Suppression of absence seizures by electrical and pharmacological activation of the caudal superior colliculus in a genetic model of absence epilepsy in the rat.

Activation of the superior colliculus has been shown to reproduce the antiepileptic effect of the inhibition of the substantia nigra reticulata. A circuit involving neurons of the caudal deep layers of the superior colliculus has been suggested to control brain stem convulsive seizures. The present study was designed to examine whether a similar circuit is also involved in the control of absence seizures. For this, activation of either the rostral or caudal parts of the deep and intermediate layers of the superior colliculus was applied in a genetic model of absence seizures in the rat (GAERS). Single-shock (5 s) electrical stimulation of the rostral and caudal superior colliculus interrupted ongoing spike-and-wave discharges at an intensity (antiepileptic threshold) significantly lower than the intensity inducing behavioral effects. At this intensity, no interruption of licking behavior was observed in water-deprived rats. Repeated stimulations (5 s on/5 s off) at the antiepileptic threshold reduced absence seizures only during the first 10 min. Bilateral microinjection of a GABA antagonist (picrotoxin, 33 pmol/side) significantly suppressed spike-and-wave discharges when applied in the caudal aspect of the superior colliculus. This antiepileptic effect appears dissociated from an anxiogenic effect, as tested in an elevated plus maze test. Finally, bilateral injection of picrotoxin (33 pmol/side) appeared more effective in the superficial and intermediate layers of the caudal superior colliculus, whereas such injections had only weak effects on absence seizures when applied in the deep layers. These results suggest that a specific population of neurons located in the intermediate and superficial layers of the caudal superior colliculus is involved in the inhibitory control of absence seizures. It may constitute an important relay for the control of absence seizures by the basal ganglia via the substantia nigra reticulata.

Animals↗
PubMed2003

Absence epilepsy and sinus dysrhythmia in mice lacking the pacemaker channel HCN2.

Hyperpolarization-activated cation (HCN) channels are believed to be involved in the generation of cardiac pacemaker depolarizations as well as in the control of neuronal excitability and plasticity. The contributions of the four individual HCN channel isoforms (HCN1-4) to these diverse functions are not known. Here we show that HCN2-deficient mice exhibit spontaneous absence seizures. The thalamocortical relay neurons of these mice displayed a near complete loss of the HCN current, resulting in a pronounced hyperpolarizing shift of the resting membrane potential, an altered response to depolarizing inputs and an increased susceptibility for oscillations. HCN2-null mice also displayed cardiac sinus dysrhythmia, a reduction of the sinoatrial HCN current and a shift of the maximum diastolic potential to hyperpolarized values. Mice with cardiomyocyte- specific deletion of HCN2 displayed the same dysrhythmia as mice lacking HCN2 globally, indicating that the dysrhythmia is indeed caused by sinoatrial dysfunction. Our results define the physiological role of the HCN2 subunit as a major determinant of membrane resting potential that is required for regular cardiac and neuronal rhythmicity.

Animals↗
PubMed1990

Development of tolerance to the anticonvulsant effect of valproate but not to ethosuximide in a rat model of absence epilepsy.

Ethosuximide and valproic acid were tested for 4 and 2 weeks, respectively, in rats showing the spontaneous spike-wave syndrome. Ethosuximide suppressed the syndrome at plasma concentrations of 75-100 micrograms/ml. High doses of valproate (170 mg/kg i.p., t.i.d.), resulting in plasma concentrations of about 500 micrograms/ml, were necessary to suppress the syndrome, but signs of tolerance to the drug developed from day 5. Tolerance was confined to the number of spike-wave complexes, whereas the duration of the discharges was shortened to 60% of the control value, without there being signs of tolerance. It is assumed that increases in cerebral GABA, induced by the high concentration of valproate, counteracted the anti-absence effect of the drug in this model.

Animals↗
PubMed2005

Epilepsy with myoclonic absences.

Epilepsy with myoclonic absences is characterized clinically by absences accompanied by marked, diffuse, rhythmical myoclonias, often associated with a progressive tonic contraction. The ictal EEG shows bilateral, synchronous and symmetrical spike and wave discharges repeated at 3 Hz (similar to that observed in typical absences of childhood absence epilepsy) in strict relation with myoclonias recorded on EMG. These seizures occur many times a day. Associated seizures are present in 2/3 of the cases, the most frequent association being GTCS in 45%. The age at onset is about 7 years. There is a male preponderance. The evolution is variable and seems to depend on the existence or not of GTCS. Classical cotherapy with valproate and ethosuximide with appropriate plasma levels is more efficient if myoclonic absences are non-associated with GTCS. In cases where GTCS are associated, there is often an unfavourable outcome, with persistence of myoclonic absences or with modification of the epilepsy with a possible evolution towards a generalized cryptogenic or symptomatic form.

Anticonvulsants↗
PubMed2004

An impaired neocortical Ih is associated with enhanced excitability and absence epilepsy.

Neuronal subthreshold excitability and firing behaviour are markedly influenced by the activation and deactivation of the somato-dendritic hyperpolarization-activated cation current (Ih). Here, we evaluated possible contributions of Ih to hyperexcitability in an animal model of absence seizures (WAG/Rij rats). We investigated pyramidal neurons of the somatosensory neocortex, the site of generation of spike-wave discharges. Ih-mediated functions in neurons from WAG/Rij rats, Wistar rats (sharing the same genetic background with WAG/Rij, but less epilepsy-prone) and ACI rats (an inbred strain, virtually free of seizures) were compared. We complemented whole-cell recordings from layer 2-3 pyramidal neurons with immunohistochemistry, Western blot and RT-PCR analysis of the h-channel subunits HCN1-4. The fast component of Ih activation in WAG/Rij neurons was significantly reduced (50% reduction in the h-current density) and four times slower than in neurons from nonepileptic Wistar or ACI rats. The results showing decreases in currents corresponded to a 34% reduction in HCN1 protein in the WAG/Rij compared to the Wistar neocortex, but HCN1 mRNA showed stable expression. The other three Ih subunit mRNAs and proteins (HCN2-4) were not affected. The alterations in Ih magnitude and kinetics of gating in WAG/Rij neurons may contribute to augmented excitatory postsynaptic potentials, the increase in their temporal summation and the facilitation of burst firing of these neurons because each of these effects could be mimicked by the selective Ih antagonist ZD 7288. We suggest that the deficit in Ih-mediated functions may contribute to the development and onset of spontaneously occurring hyperexcitability in a rat model of absence seizures.

2-Amino-5-phosphonovalerate↗
PubMed1991

Effect of psychotropic agents on a model of absence epilepsy in rats.

The effect of different groups of psychotropic agents on the spontaneous absence-like paroxysms in the ECoG of rats was studied in order to evaluate the specificity of the model for antiabsence drugs. Morphine-like analgesics increased the number of paroxysms, whereas this was depressed or the discharges were completely abolished by the following drugs: d-amphetamine, tricyclic antidepressants, centrally acting anticholinergics and L-DOPA, NMDA antagonists and memantine. Since the latter drugs have been reported to be effective in petit mal epilepsy, or the NMDA antagonists and memantine, have a potential anticonvulsant effect, the results are in favour of the usefulness of the model for antiabsence drugs.

Animals↗
PubMed2004

Photosensitive absence epilepsy with myoclonias and heterozygosity for succinic semialdehyde dehydrogenase (SSADH) deficiency.

OBJECTIVE: Succinic semialdehyde dehydrogenase (SSADH) deficiency is a neurometabolic disorder characterized by excessive GABA levels and seizures. There has been no clinical phenotype described to date with heterozygosity for SSADH deficiency. METHODS: A patient heterozygous for SSADH deficiency presented with absence and myoclonic seizures. EEG monitoring and enzymatic, metabolic, and molecular studies for SSADH were obtained on the patient and family members. RESULTS: EEG recordings yielded generalized 3-4 Hz spike-wave paroxysms and trains of multiple spikes in the heterozygous patient, and photosensitivity in the heterozygous patient and parent as well as in the sibling with homozygous deficiency. The heterozygous patient and parents did not manifest 4-OH-butyric aciduria but SSADH levels were low and a splice site mutation of the SSADH gene was identified in each. CONCLUSIONS: Heterozygosity for SSADH deficiency may be associated with an epilepsy syndrome characterized by absence and myoclonic seizures, photoparoxysmal EEG and generalized epileptiform discharges SIGNIFICANCE: Heterozygous SSADH deficiency may be suspected, given an appropriate family history in the setting of an apparently idiopathic generalized epilepsy. Pathogenic explanations may relate to regional elevations in GABA or GHB concentrations.

Adolescent↗
PubMed1993

[Epilepsies with absence in childhood].

Absences are one of the most often seen type of seizures in the first and second decade and the prominent feature in infantile, juvenile and childhood absence epilepsy. Besides these in some way benign epilepsies absences were found in other prognostic more serious epileptic syndromes and in some neurodegenerative diseases. Therefore, the appearance of absences in the pediatric age group need a thoroughly done work up in any patient.

Anticonvulsants↗
PubMed2006

Epilepsy with myoclonic absences.

Epilepsy with myoclonic absences is a rare seizure disorder with intellectual impairment and resistance to conventional anti-convulsants. It is essential to diagnose epilepsy with myoclonic absences earlier for a better outcome. The authors present a case report to highlight this fact.

Anticonvulsants↗
PubMed2001

[New antiepileptic drugs in childhood epilepsies: indications and limits].

Regarding the antiepileptic drugs (AEDs) in children, it was recently shown that they have a specific profile of efficacy and also of worsening according to the different epilepsy syndromes. However, the therapeutic profile of the most recent compounds is still not completely established in children because of the high number of syndromes and the difficulty to perform controlled studies in this age range. Controlled studies are most often first performed in adults and they begin in children whereas the new drug is already approved. However, some new AEDs dramatically improved seizure control, particularly in some severe epilepsy syndromes such as West syndrome and Lennox-Gastaut syndrome. Vigabatrin demonstrated a remarkable efficiency in infantile spasms whereas it tends to worsen myoclonic epilepsies, absence epilepsy and idiopathic partial epilepsy. Lamotrigine is efficient in absence epilepsy and symptomatic or cryptogenic generalized epilepsies such as Lennox-Gastaut syndrome and myoclonic astatic epilepsy. By contrast, lamotrigine increases the frequency of seizures in severe myoclonic epilepsy in infancy (Dravet syndrome) as well as in some cases of idiopathic partial epilepsy. Felbamate remains indicated as third line drug in refractory Lennox-Gastaut syndrome provided blood parameters are controlled. The therapeutic profile of oxcarbazepine is closed to that of carbamazepine. The efficacy of topiramate was demonstrated in partial epilepsy, but the other indications remain to be précised. Pediatric studies using gabapentin and tiagabine disclosed encouraging results in partial epilepsy. Clinical trials with stiripentol represent an example of strategy for developing a new AED in children; it recently demonstrated, in association with clobazaru, efficacy in a severe myoclonique epilepsy in infancy.

Anticonvulsants↗
PubMed1983

Long-term prognosis in two forms of childhood epilepsy: typical absence seizures and epilepsy with rolandic (centrotemporal) EEG foci.

Findings in children seen between 1955 and 1965 during the year of onset of typical absence seizures (90 patients) or rolandic epilepsy (79 patients) were analyzed by actuarial methods. One hundred and eighteen patients were followed for more than 15 years. Rolandic epilepsy is a true benign epilepsy ending with puberty. Although school and family problems are common during the acute stage of the disease, the social adaptability of such patients is excellent. We considered only typical absences occurring as a first epileptic sign in normal children. Myoclonic or atonic absences have a poor prognosis. Many patients with simple and automatic absences experience remission 15 years after withdrawal of medication. The overall cessation rate in those experiencing absences was only 57.5%, however, and 36% of patients developed tonic-clonic seizures. Social adaptability was often inadequate. Simple and automatic absences (constituting a homogeneous group) are not truly a benign form of epilepsy, even though prognosis for those afflicted is better than that for those with other forms of primary generalized epilepsy.

Adolescent↗
PubMed1997

Opposite effects of GABAB receptor antagonists on absences and convulsive seizures.

In Wistar rats with spontaneous non-convulsive absence epilepsy, absence seizures were dose dependently suppressed by intraperitoneal administration of the GABAB receptor antagonists CGP 36742, 50-400 mg/kg, and CGP 56999, 0.25-0.75 mg/kg, and by bilateral microinjections of the same compounds into the lateral nuclei of the thalamus. In rats susceptible to audiogenic seizures, intraperitoneal administration of both GABAB receptor antagonists, at doses which suppressed absence seizures, facilitated the elicitation of sound-induced tonic seizures. In non-epileptic control rats, intraperitoneal injections of higher doses of CGP 36742 (800-2400 mg/kg) and CGP 56999 (3-6 mg/kg) induced delayed clonic convulsions, which were suppressed by pretreatment with baclofen. c-Fos protein was expressed after GABAB receptor antagonist-induced seizures in the cortex, hippocampus, amygdala, perirhinal and piriform cortex. Intra-cortical and hippocampal microinfusion of both GABAB receptor antagonists produced focal seizures. In conclusion, GABAB receptor antagonists suppress non-convulsive absence seizures by blocking thalamic GABAB receptors, while they induce convulsions in cortical and limbic structures.

Animals↗