Slow Wave Discharges Research Articles

A proton magnetic resonance spectroscopic study in juvenile absence epilepsy in early stages

Purpose The aim of this study to evaluate the hippocampal, frontal and thalamic lobe functions in the early stage of the juvenile absence epilepsy (JAE) by magnetic resonance proton spectroscopy (MRS). Method Fourteen patients with juvenile absence epilepsy with typical absence seizures and 10 healthy volunteer controls were included in this study. The diagnosis of the patients was in accordance with EEG findings and seizure semiology. All patients had minimum twice EEG recordings and all had typical 3-Hz generalized spike and slow-wave discharges at least on one EEG. All patients had bilateral MRS of frontal, thalamic and hippocampal regions and NAA, NAA/Cr, NAA/Cho, NAA/Cho + Cr levels were detected. Results The mean age was 14.9 ± 2.05 and 14.5 ± 1.7 of the JAE patients and control subjects, respectively. Mean seizure onset duration were 2.3 ± 0.9 years. In patient group the frontal, thalamic and hippocampal NAA/Cr ratios were 1.65, 1.78, 1.47 in right and 1.75, 1.90, 1.42 in left, respectively. While in the control group NAA/Cr ratios were 1.64, 2.42, 1.57 in right and 1.83, 2.44, 1.47 in left, respectively. There weren't any difference in frontal and hippocampal regions, but the bilateral thalamic NAA, NAA/Cr ratios of the patients were significantly lower than control group even in early stages of the disease. Conclusion The observed reductions in NAA levels and NAA/Cr ratios of bilateral thalamic regions are consistent with epilepsy related excitoxicity as a possible underlying mechanism even in early stage of JAE. However, we believe that to generalize the results of our study a prospective multicenter study is required.

α 1-adrenoceptor modulation of spontaneous electrical waveforms in the guinea-pig prostate

The aim of this study was to investigate the effects of phenylephrine on the spontaneous slow wave and pacemaker activity in the guinea-pig prostate. Membrane potential recordings were made using intracellular microelectrodes. Guinea-pig prostatic cells either displayed ‘slow wave’ activity or ‘pacemaker’ potentials. In the presence of nifedipine, none of the parameters measured were significantly different between both waveforms. Phenylephrine (1 µM) or histamine (5 µM) increased the frequency of slow waves and pacemaker potentials in the absence or presence of nifedipine (1 µM). In the presence of nifedipine (1 µM), the addition of either cyclopiazonic acid (CPA, 10 µM) or carbonyl cyanide 3-chlorophenylhydrazone (CCCP, 1–10 µM) caused an initial transient increase in frequency of the spontaneous electrical activity that was associated with a membrane depolarisation of 3–7 mV before abolishing activity. Following the cessation of electrical activity, phenylephrine (1 µM) was unable to restore the spontaneous electrical events. Although niflumic acid (10–100 µM) (in the presence of 1 µM nifedipine) similarly abolished all activity, electrical activity was promptly initiated upon the addition of phenylephrine (1 µM). These results demonstrate that in the presence of nifedipine, there are no differences between the slow waves and pacemaker potentials suggesting that both activities arise from cells that are well coupled. Both phenylephrine and histamine increased the frequency of pacemaker activity which is likely to; at least, partly explain the increase in slow wave discharge also evoked by these agents. In the presence of nifedipine, the effects observed upon α 1-adrenoceptor activation were dependent on Ca 2+ cycling by both the intracellular Ca 2+ stores and mitochondria.

Continuous EEG–fMRI in patients with partial epilepsy and focal interictal slow-wave discharges on EEG

To verify whether in patients with partial epilepsy and routine electroenecephalogram (EEG) showing focal interictal slow-wave discharges without spikes combined EEG-functional magnetic resonance imaging (fMRI) would localize the corresponding epileptogenic focus, thus providing reliable information on the epileptic source. Eight patients with partial epileptic seizures whose routine scalp EEG recordings on presentation showed focal interictal slow-wave activity underwent EEG-fMRI. EEG data were continuously recorded for 24 min (four concatenated sessions) from 18 scalp electrodes, while fMRI scans were simultaneously acquired with a 1.5-Tesla magnetic resonance imaging (MRI) scanner. After recording sessions and MRI artefact removal, EEG data were analyzed offline. We compared blood oxygen level-dependent (BOLD) signal changes on fMRI with EEG recordings obtained at rest and during activation (with and without focal interictal slow-wave discharges). In all patients, when the EEG tracing showed the onset of focal slow-wave discharges on a few lateralized electrodes, BOLD-fMRI activation in the corresponding brain area significantly increased. We detected significant concordance between focal EEG interictal slow-wave discharges and focal BOLD activation on fMRI. In patients with lesional epilepsy, the epileptogenic area corresponded to the sites of increased focal BOLD signal. Even in patients with partial epilepsy whose standard EEGs show focal interictal slow-wave discharges without spikes, EEG-fMRI can visualize related focal BOLD activation thus providing useful information for pre-surgical planning.

TUO20 Continuous EEG-fMRI study in patients with partial epilepsy and focal interictal slow-wave discharges on EEG

TUO20 Continuous EEG-fMRI study in patients with partial epilepsy and focal interictal slow-wave discharges on EEG

Regional differences in the frequency of slow waves in smooth muscle of the guinea-pig stomach

The frequency of slow waves recorded from circular muscle bundles with attached longitudinal muscle (intact muscle) was compared with that of slow potentials recorded from isolated circular muscle bundles (isolated muscle) from the guinea-pig stomach. In intact muscle preparations, slow waves were generated in the corpus, antrum and pylorus with a higher frequency in the corpus (about 5 min(-1)) than the other regions (about 2 min(-1) in antrum, about 1.5 min(-1) in pylorus). The resting potential amplitude was graded across the stomach, at about -50 mV in the fundus, -60 mV in the corpus, -65 mV in the antrum and -70 mV in the pylorus. A similar distribution of resting membrane potential and slow potential frequency was also observed in isolated muscle bundles from the different regions. Caffeine (1 mM) abolished slow waves in some corpus preparations and inhibited the 2nd component of slow waves in the antrum and pylorus, and also abolished slow potentials in isolated muscle preparations from any region of the stomach. This suggests that myenteric interstitial cells of Cajal (ICC-MY) are heterogeneously distributed in the stomach (pylorus, antrum and part of the corpus regions), with a homogeneous distribution of muscular interstitial cells of Cajal (ICC-IM) within the circular muscle bundles. The frequency of slow potentials in smooth muscle isolated from any region of the stomach changed linearly in response to membrane potential changes produced by either current injection or high potassium solutions. The frequency of slow potentials after setting the membrane potential at -60 mV was larger in the corpus than the antrum, suggesting that the high frequency discharge of corpus muscle is produced by the low membrane potential and additional unidentified factors. We suggest that the regional difference in slow wave discharge is produced mainly by ICC-IM, and the role of ICC-MY may be little, if any.

K+ channel modulation of slow wave activity in the guinea‐pig prostate

The aim of this study was to investigate the role of different K(+) channel populations and the inhibitory effect of various exogenously applied K(+) channel openers in the regulation of slow wave activity in the guinea-pig prostate. Recordings of membrane potential were made using intracellular microelectrodes. Tetraethylammonium (TEA 300 micro M and 1 mM), iberiotoxin (150 nM) and 4-aminopyridine (4-AP 1 mM) increased the frequency of slow wave discharge. Apamin (1-200 nM) and glibenclamide (1 micro M) had no effect on slow wave activity. Lemakalim (1 micro M) and PCO-400 (1 micro M) abolished the slow waves, as did sodium nitroprusside (SNP 10 micro M) and calcitonin gene-related peptide (CGRP 100 nM). The inhibitory effect of these agents was independent of a significant change in membrane potential. In the presence of 4-AP (1 mM), TEA (1 mM) or glibenclamide (1 micro M) the inhibitory actions of SNP (10 micro M) were attenuated. The inhibitory actions of CGRP (100 nM) were also reversed by glibenclamide (1 micro M). In contrast, isoprenaline (1 micro M) did not alter the frequency of slow wave discharge. These results demonstrate that BK(Ca) and 4-AP-sensitive K(+) channels regulate the frequency of prostatic slow wave discharge. SNP and CGRP abolish slow waves in a hyperpolarisation-independent manner, partially via opening of K(ATP) channels. BK(Ca) and 4-AP-sensitive K(+) channels also play an important role in the SNP-induced inhibition of slow wave activity. The lack of membrane hyperpolarisation associated with the SNP- and CGRP-induced inhibition implies that the channels involved in this action are not predominantly located on the smooth muscle cells.

Corpus callosotomy: A palliative therapeutic technique may help identify resectable epileptogenic foci

Corpus callosotomy has a long history as a palliative treatment for intractable epilepsy. Identification of a single epileptogenic zone is critical to performing successful resective surgery. We describe three patients in which corpus callosotomy allowed recognition of unapparent seizure foci, leading to subsequent successful resection. We retrospectively reviewed our epilepsy surgery database from 2003 to 2005 for children who had a prior callosotomy and were candidates for focal resection. All underwent magnetic resonance imaging and scalp video electroencephalograph monitoring, and two had magnetoencephalography, electrocorticography and/or intracranial video electroencephalograph monitoring. The children were 8 and 9 years old, and seizure onset varied from early infancy to early childhood. One child had a history of head trauma preceding seizure onset, one had a large intracerebral infarct and dysplastic cortex in the contralateral frontal lobe, and the other had an anterior temporal lobe resection without improvement in seizure frequency. After medical management failed, callosotomy was performed with the expectation of decreasing the seizure types affecting both hemispheres. Following transection of the callosal fibers, a single focus was recognized and resected, with resultant dramatic improvement in seizure control. In medically refractory epilepsy, where rapid secondary bisynchrony is suspected but the electroencephalograph is non-localizing, callosotomy should be considered as a means of treating generalized seizure types, but may also assist in identifying potentially operable seizure foci. Study limitations include its retrospective nature and cohort size. The findings, however, suggest the need for prospective, systematic, well-controlled studies of the use of corpus callostomy in this intractable patient population.

Transgenic mice over-expressing GABABR1a receptors acquire an atypical absence epilepsy-like phenotype

In this study, we tested whether over-expressing the GABA(B) receptor R1a subtype in transgenic mouse forebrain neurons would be sufficient to induce spontaneous absence seizures. As hypothesized, these transgenic mice develop spontaneous, recurrent, bilaterally synchronous, 3-6 Hz slow spike and wave discharges between 2 and 4 months of age. These discharges are blocked by ethosuximide and exacerbated by baclofen confirming their absence nature. The discharges occur coincident with absence-like behaviors such as staring, facial myoclonus, and whisker twitching. However, in contrast to typical absence epilepsy models, these mice move during the ictal event, display spike and wave discharges in both thalamocortical and limbic circuitry, exhibit impaired hippocampal synaptic plasticity, and display significantly impaired learning ability. Collectively, these features are more characteristic of the less common but more debilitating atypical form of absence epilepsy. Thus, these data support a role for the GABA(B)R1a receptor subtype in the etiology of atypical absence epilepsy.

Hemispherectomy in Early Infantile Epileptic Encephalopathy

The authors report the successful surgical treatment of early infantile epileptic encephalopathy and suppression burst in 2 children with hemispheric dysplasia. At surgical evaluation, focal epileptic patterns were recorded from the abnormal hemisphere, and ictal single-photon emission computed tomography demonstrated ipsilateral regional hyperperfusion. Functional hemispherectomy was performed after electrocorticography revealed near-continuous spike and slow-wave discharges over the affected hemisphere. Histopathology revealed Taylor-type cortical dysplasia. Postoperatively, both patients are seizure free on antiepileptic drug monotherapy and have shown improved developmental status. Their favorable outcome demonstrates that children with early infantile epileptic encephalopathy due to unilateral malformations of cortical development may benefit from early surgical intervention.

Epilepsy surgery in a patient with Lennox–Gastaut syndrome and cortical dysplasia

Lennox–Gastaut syndrome (LGS) is classified as a generalized epilepsy, and is often intractable to antiepileptic drugs. Although corpus callosotomy may sometimes control drop attacks, curative epilepsy surgery is rarely possible in LGS. We report, here, a patient with LGS and focal cortical dysplasia, who became seizure-free after epilepsy surgery. The patient was a 24-month-old boy without perinatal insult in whom seizures began 7 days after birth and who experienced development delay. Brain magnetic resonance imaging (MRI) showed focal cortical lesion with calcification in the right frontal area. At age 13 months, his seizure type changed from tonic seizures to head drops (atonic types) and atypical absence seizures. His interictal electroencephalogram (EEG) showed generalized slow spike and wave discharges, and he was diagnosed with LGS. His seizures were intractable to medical treatment, and a ketogenic diet was not effective. He was evaluated prior to surgery by long-term video-EEG monitoring, which detected many seizures consisted of a sudden onset of falling attacks (atonic type) intermittently followed by atypical absence seizures with diffuse slow wave bursts followed by slow spike and wave discharges in ictal EEG, brain positron emission tomography (PET) and MRI. A right frontal lesionectomy with intra-operative electrocorticography (EcoG) was performed. From the time of lesionectomy to the present, the patient has been seizure free and has been developing normally. Our results suggest that focal resective surgery should be considered in patients with LGS and focal epileptic lesions.

GABA A-R α1 subunit knockin mutation leads to abnormal EEG and anesthetic-induced seizure-like activity in mice

Gamma-aminobutyric acid-type A receptors (GABA A-Rs) have been proposed as a target for many general anesthetics. We recently created knockin (KI) mice harboring a point mutation (serine 270 to histidine) in the GABA A-R α1 subunit. This mutation abolishes sensitivity of recombinant GABA A–Rs to isoflurane while maintaining normal sensitivity to halothane and increasing the potency of GABA. KI mice showed abnormalities in the EEG baseline, including occasional spike-wave activity and spindle-like bursts. When anesthetized with isoflurane, the KI mice but not the control mice revealed repetitive 4–5Hz slow wave discharges in the cortical EEG. KI mice did not differ from controls in response to isoflurane or halothane in the standard tail clamp/withdrawal and loss of righting reflex assays. We recorded miniature inhibitory postsynaptic currents (mIPSCs) from hippocampal interneurons and pyramidal cells in brain slices. mIPSCs in neurons from KI mice were of normal amplitude, but decayed more slowly than controls. Hippocampal mIPSCs in control mice were significantly prolonged by 0.4 and 0.9 MAC isoflurane, and by 0.5 MAC halothane. In KI mice, the effect of isoflurane on mIPSC decay was dramatically reduced, while halothane prolonged mIPSCs as for controls. We conclude that the kinetic and pharmacological properties of hippocampal GABA A-Rs in the KI mouse recapitulate many features of mutant α1β2γ2 GABA A-Rs observed in vitro. GABA A-Rs containing α1 subunits do not appear to contribute to the actions of isoflurane in the spinal cord, but both EEG and synaptic recordings provide evidence for effects of isoflurane on these GABA A-R isoforms in cortical structures.

Juvenile myoclonic epilepsy: non‐classic electroencephalographical presentation in adult patients*

Although diagnosis of juvenile myoclonic epilepsy (JME), a common form of idiopathic generalized epilepsy, is based on clinical and electroencephalogram (EEG) criteria, at times clinical symptoms may be misleading, like the occurrence of asymmetric myoclonic jerks. Thus EEG assumes an important role in these cases, it can fail to show the classical polyspike and slow wave (PSW) discharges of JME, specially in a routine evaluation in older patients. We analyzed retrospectively EEG results of 35 patients with JME [Commission on Classification and Terminology of the International League Against Epilepsy (ILAE) Epilepsia 1989; 30: 389] aged 12-44 years. (mean 22.7 years) at first medical evaluation. EEG findings of 35 patients (19 females, 16 males) with JME consisted of normal tracings in 22.9 and 54.3% had at least one normal exam. EEG abnormalities present in 27 patients (77.1%) consisted of isolated generalized slowing in two and generalized discharges in 25: irregular spike and wave complexes (SWC) in 76%; PSW in 48%; SWC faster than 3 Hz in 20%; spikes, sharp waves, and irregular slow waves in 24%; asymmetric generalized epileptiform discharges in 40%; and associated focal paroxysms in 12%. Thus JME is classically associated to PSW on EEG, the most frequent abnormality was irregular SWC. Generalized paroxysms could occur in an asymmetric fashion and rarely associated to focal activity.

Response: Nonconvulsive Status Epilepticus after Temporal Lobectomy

To the Editor: Dr. Fernández-Torre raises several valid points on the difficulties facing clinicians caring for patients with nonconvulsive status epilepticus (NCSE). As we mentioned in our article (1), the characteristics of NCSE are usually subtle, ambiguous, and nonspecific. Generalized 3-Hz spike-and-wave is seen in only 7% of patients with absence status epilepticus (ASE) (2), whereas other EEG patterns, including generalized spike-and-waves with a frequency less than 3 Hz, generalized rhythmic slowing with intermixed spike and slow-wave discharges, irregular sharp and slow waves, or even diffuse background slowing are more frequent (3, 4). These often predominate in the frontal region, as in our case. Although some ictal patterns in complex partial status epilepticus may include spike-and-wave discharges, resembling those seen in ASE (2, 5), our patient had interictal EEG recordings before surgery showing a small amount of generalized spike-and-wave without evidence of secondary bilateral synchrony and had no evidence of frontal lobe pathology, leading us to conclude that she was in ASE. She remains seizure free 8 months after temporal lobectomy. The approach of providing a simple classification of ASE is indeed reasonable, but one must also consider certain variants, such as our case, a patient with localization-related epilepsy with interictal evidence of generalized epileptiform discharges. Fortunately, the existing protocols for treatment do not make any distinction between status epilepticus of the localization-related or generalized type, with benzodiazepines the preferred initial treatment.

Electroencephalogram slowing, sleepiness and treatment response in patients with schizophrenia during olanzapine treatment

Electroencephalogram (EEG) slowing is associated with clozapine side effects, e.g., sedation, and may predict treatment response during clozapine treatment. As olanzapine and clozapine share many pharmacological properties, we investigated whether EEG slowing during olanzapine treatment was related to therapy outcome and sleepiness in patients with schizophrenia. Participants were age- and gender-matched schizophrenic patients treated with olanzapine (n 54), receiving no pharmacological treatment (n 54), or cotreated with olanzapine and some other psychotropic drug (n 38). Their EEG recordings were assessed visually by the same rater blind to clinical data. The EEG scores were categorized using standardized forms. Patients with a poor treatment response did not differ significantly from those with a good response to treatment either in EEG patterns or in frequency of sleepiness. Olanzapine treatment was associated with increased rates of slow (70.4% vs. 22.3%) and sharp waves (22.2% vs. 7.4%), as well as of paroxysmal slow wave discharges (14.8% vs. 1.9%), but did not induce spike- or sharp-slow-wave complexes. Cotreatment with another antipsychotic further increased EEG abnormalities, whereas benzodiazepine administration diminished the olanzapine-induced EEG changes. The results show that olanzapine inducing both slow and sharp waves, as well as paroxysmal discharges, has a strong impact on EEG. However, as no spike- or sharp-slow-wave complexes were observed, the risk of epileptic seizure during olanzapine treatment can be regarded as low, as long as olanzapine is not combined with some other antipsychotic.

FMRI “deactivation” of the posterior cingulate during generalized spike and wave

Using spike-triggered fMRI, we sought to document regional changes in blood oxygen level-dependent (BOLD) activity associated with spontaneous generalised spike and slow-wave discharges (S&W). Five adult patients were studied who had idiopathic generalised epilepsy (IGE) and frequent S&W. EEG was recorded inside a 3T MRI, allowing acquisition of single, whole-brain fMRI images following S&W, as well as baseline images. Between 4 and 25 spike and wave complexes were captured in individuals. Four of the five individuals showed significant S&W-related BOLD signal reductions (“deactivation”) in the posterior cingulate ( P < 0.001 uncorrected). Significant changes were absent only in the individual with fewest spikes. Group analysis including all five subjects confirmed fMRI deactivation in the posterior cingulate. Some S&W-related BOLD signal increases were seen in the depths of the precentral sulci in individuals and on group analysis. No significant S&W-related changes in thalamic BOLD activity were observed. The posterior cingulate may have a role in the electroclinical phenomenon of S&W and “absence.” Possibilities include a causative role, with reduced activity in the cingulate facilitating the onset of S&W, a secondary role, explaining the cognitive changes observed during prolonged S&W, or an epiphenomenon.

Fast Cortical Oscillations Are Not Dependent on the Activity of GABAergic Neurons.

Effects of Bicuculline Methiodide on Fast (&gt;200 Hz) Electrical Oscillations in Rat Somatosensory Cortex Jones MS, Barth DS J Neurophysiol 2002;88(2):1016–1025 Fast oscillatory activity (more than ∼200 Hz) has been attracting increasing attention regarding its possible role in both normal brain function and epileptogenesis, yet its underlying cellular mechanism remains poorly understood. Our prior investigation of the phenomenon in rat somatosensory cortex indicated that fast oscillations result from repetitive synaptic activation of cortical pyramidal cells originating from γ-aminobutyric acid (GABA)ergic interneurons (Jones et al., 2000). To test this hypothesis, the effects of topical application of the GABAA antagonist bicuculline methiodide (BMI) on fast oscillations were examined. At subconvulsive concentrations (∼10 μM), BMI application resulted in a pronounced enhancement of fast activity, in some trials, doubling the number of oscillatory cycles evoked by whisker stimulation. The amplitude and frequency of fast activity were not affected by BMI in a statistically significant fashion. At higher concentrations, BMI application resulted in the emergence of recurring spontaneous slow-wave discharges resembling interictal spikes (IISs) and the eventual onset of seizure. High-pass filtering of the IISs revealed that a burst of fast oscillations accompanied the spontaneous discharge. This activity was present in both the pre- and the postictal regimens, in which its morphology and spatial distribution were largely indistinguishable. These data indicate that fast cortical oscillations do not reflect GABAergic postsynaptic currents. An alternate account consistent with results observed to date is that this activity may instead arise from population spiking in pyramidal cells, possibly mediated by electrotonic coupling in a manner analogous to that underlying 200-Hz ripple in the hippocampus. Additionally, fast oscillations occur within spontaneous epileptiform discharges. However, at least under the present experimental conditions, they do not appear to be a reliable predictor of seizure onset or an indicator of the seizure focus.

Effects of bicuculline methiodide on fast (>200 Hz) electrical oscillations in rat somatosensory cortex.

Fast oscillatory activity (more than approximately 200 Hz) has been attracting increasing attention regarding its possible role in both normal brain function and epileptogenesis. Yet, its underlying cellular mechanism remains poorly understood. Our prior investigation of the phenomenon in rat somatosensory cortex indicated that fast oscillations result from repetitive synaptic activation of cortical pyramidal cells originating from GABAergic interneurons (). To test this hypothesis, the effects of topical application of the gamma-aminobutyric acid-A (GABA(A)) antagonist bicuculline methiodide (BMI) on fast oscillations were examined. At subconvulsive concentrations (approximately 10 microM), BMI application resulted in a pronounced enhancement of fast activity, in some trials doubling the number of oscillatory cycles evoked by whisker stimulation. The amplitude and frequency of fast activity were not affected by BMI in a statistically significant fashion. At higher concentrations, BMI application resulted in the emergence of recurring spontaneous slow-wave discharges resembling interictal spikes (IIS) and the eventual onset of seizure. High-pass filtering of the IIS revealed that a burst of fast oscillations accompanied the spontaneous discharge. This activity was present in both the pre- and the postictal regimes, in which its morphology and spatial distribution were largely indistinguishable. These data indicate that fast cortical oscillations do not reflect GABAergic postsynaptic currents. An alternate account consistent with results observed to date is that this activity may instead arise from population spiking in pyramidal cells, possibly mediated by electrotonic coupling in a manner analogous to that underlying 200-Hz ripple in the hippocampus. Additionally, fast oscillations occur within spontaneous epileptiform discharges. However, at least under the present experimental conditions, they do not appear to be a reliable predictor of seizure onset nor an indicator of the seizure focus.

Non-convulsive status epilepticus induced by tiagabine in a patient with pseudoseizure

Tiagabine, a novel GABA reuptake inhibitor, has been reported to induce non-convulsive status epilepticus (NCSE) in patients with epilepsy. We report a 27 year old female with history of pseudoseizure documented by video-EEG monitoring who presented confusion while on 56 mg per day of tiagabine. Electroencephalography showed generalized sharp and slow wave discharges, consistent with NCSE. The NCSE was terminated by lorazepam and did not recur after tiagabine was discontinued. This case report suggests that tiagabine may induce NCSE in patients without epilepsy.

Juvenile myoclonic epilepsy: A clinical and sleep EEG study

Juvenile myoclonic epilepsy (JME) is characterized by myoclonic jerks on awakening, generalized tonic–clonic seizures (GTCS) and is associated with absence seizures in more than one third of cases. Fifteen patients with juvenile myoclonic epilepsy were studied with regard to their clinical profile, EEG data and sleep EEG findings. There was a delay in the diagnosis of JME (mean of 3.5 years) due to various reasons. Sleep deprivation was the most common precipitating factor for triggering seizures, followed by fatigue. Routine EEGs were abnormal in 73.33% of cases only and had misleading findings in 6.66%. Sleep EEGs were abnormal in 100% of cases with generalized spikes, polyspikes and slow wave discharges. Discharge rates on sleep EEGs typically increased significantly during the transition phase (i.e. the asleep to awakening stage) and we consider this to be a specific finding in appropriate clinical setting. Sleep EEGs are a more sensitive and specific tool for the diagnosis of JME while routine awake EEGs may miss or mislead.

Treatment of typical absence seizures and related epileptic syndromes.

Typical absences are brief (seconds) generalised seizures of sudden onset and termination. They have 2 essential components: clinically, the impairment of consciousness (absence) and, generalised 3 to 4Hz spike/polyspike and slow wave discharges on electroencephalogram (EEG). They differ fundamentally from other seizures and are pharmacologically unique. Their clinical and EEG manifestations are syndrome-related. Impairment of consciousness may be severe, moderate, mild or inconspicuous. This is often associated with motor manifestations, automatisms and autonomic disturbances. Clonic, tonic and atonic components alone or in combination are motor symptoms; myoclonia, mainly of facial muscles, is the most common. The ictal EEG discharge may be consistently brief (2 to 5 seconds) or long (15 to 30 seconds), continuous or fragmented, with single or multiple spikes associated with the slow wave. The intradischarge frequency may be constant or may vary (2.5 to 5Hz). Typical absences are easily precipitated by hyperventilation in about 90% of untreated patients. They are usually spontaneous, but can be triggered by photic, pattern, video games stimuli, and mental or emotional factors. Typical absences usually start in childhood or adolescence. They occur in around 10 to 15% of adults with epilepsies, often combined with other generalised seizures. They may remit with age or be lifelong. Syndromic diagnosis is important for treatment strategies and prognosis. Absences may be severe and the only seizure type, as in childhood absence epilepsy. They may predominate in other syndromes or be mild and nonpredominant in syndromes such as juvenile myoclonic epilepsy where myoclonic jerks and generalised tonic clonic seizures are the main concern. Typical absence status epilepticus occurs in about 30% of patients and is more common in certain syndromes, e.g. idiopathic generalised epilepsy with perioral myoclonia or phantom absences. Typical absence seizures are often easy to diagnose and treat. Valproic acid, ethosuximide and lamotrigine, alone or in combination, are first-line therapy. Valproic acid controls absences in 75% of patients and also GTCS (70%) and myoclonic jerks (75%); however, it may be undesirable for some women. Similarly, lamotrigine may control absences and GTCS in possibly 50 to 60% of patients, but may worsen myoclonic jerks; skin rashes are common. Ethosuximide controls 70% of absences, but it is unsuitable as monotherapy if other generalised seizures coexist. A combination of any of these 3 drugs may be needed for resistant cases. Low dosages of lamotrigine added to valproic acid may have a dramatic beneficial effect. Clonazepam, particularly in absences with myoclonic components, and acetazolamide may be useful adjunctive drugs.