Typical absence epilepsy presenting prior to age of 3 years: an uncommon form of idiopathic generalized epilepsy

Age-related morphological differences in the spike-and-wave complexes of absence epilepsy

OBJECTIVE

Absence epilepsy shows age-related clinical features, as is observed in childhood and juvenile absence epilepsy. Electroencephalogram (EEG) is characterized by bursts of 3 Hz spike-and-wave complex (SWC). We noticed a morphological variation of the slow-wave component of SWCs between patients. This study investigated whether the waveform of SWC might be associated with the child's age of this epilepsy.

METHODS

Digitally-recorded EEGs under medication-free conditions were collected from 25 children who received the diagnosis of childhood or juvenile absence epilepsy. The morphology of slow wave in SWC in the frontal midline region was quantitatively compared between younger and older children using a cluster-based permutation test.

RESULTS

At <7 years of age (2.9-6.5 years of age, n = 6), the electrical potential of the descending slope in the slow wave was positively correlated with age whereas this correlation was not observed in patients of ≥7 years of age (7.1-12.9 years, n = 19). A cluster-based permutation test confirmed the results-among the entire slow wave period (0-285 msec), the period of the descending slope (195-260 msec) showed significantly lower potential in patients of <7 years of age in comparison to patients of ≥7 years of age (sum of t-values: 46.57, p-value: 0.011).

CONCLUSIONS

The current study demonstrated an age-dependent morphological difference in the slow-wave components of SWCs in EEGs of patients with pediatric absence epilepsy. This finding may provide a clue to understanding the age-related clinical manifestations of this epilepsy.

Early childhood myoclonic epilepsy: An independent genetic generalized epilepsy with myoclonic seizures as the main seizure type

OBJECTIVE

To elucidate the characteristics of the myoclonic seizures alone, or predominant myoclonus combined with generalized tonic-clonic seizures (GTCS) and/or absences, in early childhood, and discuss its classification.

METHODS

Forty-two children were retrospectively recruited between January 2006 and June 2015.

RESULTS

The mean age of seizure onset was 40.5months. They were divided into 4 groups: myoclonic seizures alone; predominant myoclonus combined with GTCS; predominant myoclonus combined with absences; predominant myoclonus combined with both GTCS and absences. Interictal EEG showed generalized spike- or polyspike-wave discharges at 2-4Hz. Seizures were controlled in 22 patients at a mean age of 60.5months. The psychomotor development was normal (30/37) or mildly delayed (7/37).

CONCLUSIONS

We reported a cohort of patients with early childhood myoclonic epilepsy (ECME), with the following characteristics: Seizures started below 5years old in otherwise normal children; Seizure types included myoclonic seizures alone or combined with GTCS and/or absences; Febrile or afebrile GTCS might appear firstly; Interictal EEG showed generalized spike- or polyspike-wave; Seizures usually were in remission before adolescence with normal development or mild cognitive or behavioral deficits in most.

SIGNIFICANCE

ECME might be an independent epileptic syndrome not established by International League Against Epilepsy (ILAE) previously.

Advantages and limitations of brain imaging methods in the research of absence epilepsy in humans and animal models

The purpose of this review is to analyze research possibilities and limitations of several methods, technical tools and their combinations for elucidation of absence epilepsy mechanisms, particularly the childhood absences. Despite the notable collection of simultaneous recording of clinical electroencephalography (EEG) and behavioral changes in relation to absence seizures, shortcomings of scalp EEG in both spatial resolution and precise detection of subcortical centers have limited the understanding of the fundamental mechanisms of altered brain function during and after recurrent epileptic paroxysms. Therefore, in the past decade, EEG recordings have often been combined with simultaneous imaging methods in epilepsy studies. Among imaging methods, the following ones are used regularly: functional magnetic resonance imaging (fMRI), positron-emission tomography (PET), low-resolution electromagnetic tomography (LORETA), single photon emission spectroscopy (SPECT), near-infrared spectroscopy (NIRS), and optical imaging of intrinsic signals (IOS). In addition, voltage-sensitive dye optical imaging method and even photoacoustic microscopy can be applied to animal models of epilepsy. Samplings of some of the most relevant data obtained by the above methods are presented. It appears that the elaboration of more adequate animal models of the patterns of absence seizures during the early postnatal period is necessary for better correspondence of human and animal absence phenomena.

Early-onset pure absence epilepsy: a distinct epileptic syndrome

Early-onset pure absence epilepsy has not yet considered in the International League Against Epilepsy classification, but several reports have supported its existence as a distinct epileptic syndrome primarily manifesting with typical absences in early childhood. This review summarizes the current understanding on this epilepsy.

CONCLUSIONS

  Early-onset pure absence epilepsy is a distinct epilepsy characterized by absences starting from a few months to 4 years of age, normal early psychomotor development, good antiepileptic drug seizure control and normal intellectual outcome.

Long term outcome in children affected by absence epilepsy with onset before the age of three years

OBJECTIVE

The goal of this study was to define the long-term outcome of absence epilepsy presenting before the age of 3 years.

METHODS

We retrospectively studied the medical records of 40 children from eight neuropediatric centers in Italy with respect to the personal and family histories of epilepsy or febrile seizures, time of follow-up, cognitive functions, treatment, and outcome.

RESULTS

Forty patients were enrolled in this study. They all fulfilled the criteria for absence epilepsy with 3-Hz spike-wave complexes on the EEG, normal neurological examination, and no other seizures types. Seizure onset occurred between 24.1 and 36.0 months. There was a family history of epilepsy in 28%, and of febrile seizures in 13%. Thirty-three patients were treated with valproic acid (VPA), mostly used in monotherapy (26 patients) or in association with ethosuximide. At final follow-up, 33 patients were seizure free and 29 had normal EEGs. Thirty-four patients had a normal intelligence quotient (IQ), whereas 6 had a decreased IQ, mainly associated with poor control of seizures.

CONCLUSION

In our series, absence seizures presenting before the age of 3 appeared to have quite a good long-term clinical prognosis; the neuropsychological outcome was comparable to that of childhood epilepsy presenting after 3 years of age.

Childhood absence epilepsy: Elctroclinical features and diagnostic criteria

OBJECTIVE

To analyze the electroclinical features of children with childhood absence epilepsy (CAE) and discuss the diagnostic criteria for CAE.

METHODS

The video-electroencephalogram (VEEG) database in our hospital was searched using "absence seizures" and "3-Hz generalized spike and waves (GSW)" as key-words. Other epileptic syndromes with typical absence seizures were carefully excluded. Children meeting the CAE diagnostic criteria of the International League Against Epilepsy (ILAE) in 1989 were further evaluated with the diagnostic criteria proposed by Panayiotopoulos in 2005.

RESULTS

Totally 37 children met the 1989 ILAE criteria of CAE. The onset age of absence seizures ranged from 3 to 11 years. All patients had frequent absence seizures (5-60 times per day). Two patients (5.4%) had generalized tonic-clonic seizures. Hyperventilation induced absences in all patients. VEEG confirmed that 7 patients (18.9%) had only simple absences, 25 patients (67.6%) had only complex absences, and 5 patients (13.5%) had both simple and complex absences. Ictal EEG showed 3Hz GSW discharges in all patients. The seizure duration ranged from 3 to 40s. Four patients (10.8%) had two spikes per wave in ictal EEG. GSW fragments were found in 29 patients (78.4%) during sleep. Interictal polyspikes and waves were present in 17 patients (45.9%). Focal discharges predominantly in the anterior regions, were found in 22 patients (56.8%). Only 7 patients (18.9%) met the diagnostic criteria proposed by Panayiotopoulos in 2005.

CONCLUSIONS

Few patients meeting the 1989 ILAE diagnostic criteria for CAE meet the new diagnostic criteria proposed by Panayiotopoulos in 2005. The new criteria for CAE are too strict to appropriately classify some patients.

Absence seizures in the first 3 years of life: an electroclinical study of 46 cases

PURPOSE

Early onset absence seizures have been considered a rare heterogeneous group with a poor prognosis. Only few patients may be categorized into well-known syndromes. We have evaluated electroclinical features, evolution, and the nosologic boundaries of early onset absence seizures.

METHODS

Forty-six neurologically normal patients with absence seizures associated with bilateral, synchronic, or asynchronic, and symmetric or asymmetric spike-and-wave paroxysms with onset in the first 3 years of life were included. Patients with abnormal neurologic examination and brain imaging were excluded from the study.

KEY FINDINGS

In our study, 39 patients met the clinical and electroencephalography (EEG) criteria of well-defined epileptic syndromes. Childhood absence epilepsy was found in 11 patients, benign myoclonic epilepsy in infancy in 18 patients, eyelid myoclonic epilepsy in 4, and epilepsy with myoclonic absences in 6. We did not find clinical and EEG criteria of well-recognized epileptic syndromes in seven children. Nine of 11 patients with simple absence seizures became seizure free. All these patients had normal neurologic and neuropsychological evaluations. Of the 35 patients who had absence seizures associated with myoclonic seizures, 20 became seizure free. Fifteen of 35 children continue having seizures. At the last visit, 20 of these 35 patients had normal neurologic and neuropsychological evaluations, 11 presented with mild mental retardation, and 4 with severe mental retardation.

SIGNIFICANCE

Epilepsies with absence seizures of early onset are relatively uncommon. Most of the patients had well-defined epileptic syndromes with a variable evolution. The evolution depended on the epileptic syndromes.

Absence seizures: a review of recent reports with new concepts

Absence seizures with bilateral spike-wave (SW) complexes at 3Hz are divided into the childhood form, with onset at around 6 years of age, and the juvenile form, with onset usually at 12 years of age. These seizures typically last 9-12s and, at times, are activated by hyperventilation and occasionally by photic stimulation. Generalized tonic-clonic (GTC) seizures may also occur, especially in the juvenile form. There may be cognitive changes, in addition to linguistic and behavioral problems. Possible mechanisms for epileptogenesis may involve GABAergic systems, but especially T-calcium channels. The thalamus, especially the reticular nucleus, plays a major role, as does the frontal cortex, mainly the dorsolateral and orbital frontal areas, to the extent that some investigators have concluded that absence seizures are not truly generalized, but rather have selective cortical networks, mainly ventromesial frontal areas and the somatosensory cortex. The latter network is a departure from the more popular concept of a generalized epilepsy. Between the "centrencephalic" and "corticoreticular" theories, a "unified" theory is presented. Proposed genes include T-calcium channel gene CACNA1H, likely a susceptible gene in the Chinese Han population and a contributory gene in Caucasians. Electroencephalography has revealed an interictal increase in prefrontal activity, essential for the buildup of the ictal SW complexes maximal in that region. Infraslow activity can also be seen during ictal SW complexes. For treatment, counter to common belief, ethosuximide may not increase GTC seizures, as it reduces low-threshold T-calcium currents in thalamic neurons. Valproic acid and lamotrigine are also first-line medications. In addition, zonisamide and levetiracetam can be very helpful in absence epilepsy.