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Magnetoencephalographic Analysis in a Case of Early-Onset Benign Childhood Occipital Seizures
Abstract
We report a 12-year-old boy who had one seizure comprising deviation of the eyes followed by impairment of consciousness for 30 minutes at the age of 6 years. No visual hallucination or ictal vomiting was observed. Interictal electroencephalography showed repetitive spikes and spike-wave discharges over the left occipital lobe. Magnetoencephalography revealed that the estimated dipoles were clustered in the left cuneus on magnetic resonance imaging, which corresponded to the area of peripheral vision and the associated visual cortex but not to the central visual cortex. Magnetoencephalography is advantageous for determining the electrophysiologic mechanism of early-onset benign childhood occipital seizures.
The aims of this study were to identify the generator of the paroxysmal partial discharges in Panayiotopoulos syndrome by means of magnetoencephalography and to determine the significance of these formations in the epileptogenesis of the developing nervous system. We report magnetoencephalographic data for two cases of Panayiotopoulos syndrome showing the rapid generalization of the source of interictal spikes that explains extraoccipital manifestations such as ictal vomiting and consciousness disturbance.
Panayiotopoulos syndrome (PS) is a type of benign childhood partial epilepsy that is frequently associated with abundant multifocal spikes other than main occipital spikes on the EEG. In this study, we investigated the characteristic features of dipoles in PS.
We performed dipole analysis of the interictal occipital spike discharges seen in 10 children with PS (group A) and in 10 children with other types of symptomatic localization-related epilepsy (group B). We analyzed the dipoles of the averaged spike in each patient.
In group A, the averaged occipital spikes in each patient showed dense dipole locations in the mesial occipital area; in group B, widely scattered dipole locations were observed. In Group A, the geometric centers of the dipoles at each time point (such as at the main negative peak and before or after the main peak) were estimated in the neighboring locations. In contrast, they tended to be scattered in group B.
Our study reveals that PS has high dipole stability, similar to that of rolandic epilepsy. From the electroencephalographic view, this seems to indicate a close link between these two syndromes.
We describe herein a patient with Panayiotopoulos syndrome (PS) showing an atypical course. The patient initially had seizures typical of this syndrome from 3 to 5 years of age. EEG showed right occipital high-amplitude sharp and slow-wave complexes followed by brief generalized discharges of slow waves. Sequential EEGs obtained from 5 to 11 years of age showed both multifocal discharges and generalized spike and wave complexes. With these changes in EEG findings, the patient experienced various types of seizures. The seizures were frequent and showed oculocephalic deviation followed by absence, atonic seizures, generalized tonic clonic convulsions and clonic seizures of the eyelids, which were observed between 7 and 10 years of age. Antiepileptic drugs were only partially effective for these seizures. Ictal EEG recorded at 8 years of age revealed high-voltage slow waves from the bilateral frontal and occipital regions prior to diffuse high-amplitude spike-wave bursts. At 9 years of age, magnetoencephalography (MEG) revealed the calculated dipoles of the preceding bifrontal spike-wave discharges to be in the frontal areas, while those of the following generalized spike-wave bursts were in the bilateral mid-temporal areas. In PS, reportedly, dipoles of multifocal epileptic discharges are usually located in the occipital and Rolandic areas. The unique clinical evolution in our case may be associated with the unusual frontal localization of dipoles detected by MEG.
We previously reported the results of a magnetoencephalographic study in patients with Panayiotopoulos syndrome manifesting occipital epileptic discharges, in which the equivalent current dipoles of spike discharges were clustered alongside the major cortical sulci, such as parieto-occipital and calcarine. This report is the result of a magnetoencephalographic study of three patients with Panayiotopoulos syndrome exhibiting equivalent current dipoles clustering in the frontal area. Patient 1, a 13-year-old male, exhibited clustering equivalent current dipoles alongside right inferior frontal sulcus, but the orientations were irregular. Patient 2 is an 11-year-old younger brother of Patient 1, whose magnetoencephalograph revealed equivalent current dipoles clustering alongside right prefrontal sulcus and regular orientations. Patient 3 is a 10-year-old female who had equivalent current dipoles clustering alongside right superior frontal sulcus and extremely regular orientations. The locations of clustering equivalent current dipoles of frontal spike discharges were not restricted to one specific frontal sulcus but were present in various locations over the convexity of the prefrontal area. In conclusion, these findings suggest that it is inappropriate to classify Panayiotopoulos syndrome as occipital epilepsy. In addition, the result of this study, that frontal spike discharges seem to occur in relatively older patients, may suggest a correlation between brain maturation and spike occurrence.
In a recent proposal, the Commission on Classification and Terminology of the International League Against Epilepsy recognized early-onset childhood epilepsy with occipital spikes (Panayiotopoulos type), differentiating it from the only other type of childhood epilepsy with occipital spikes previously accepted: late-onset childhood epilepsy with occipital spikes (Gastaut type). The importance of this newly recognized syndrome of benign childhood partial seizures is that it is very common-only 2.4 times less frequent than benign rolandic epilepsy, and of equally excellent prognosis. It is characterized by a unique seizure type comprising a combination of autonomic and behavioral disturbances, vomiting, deviation of the eyes, and often with impairment of consciousness that can progress to convulsions. These commonly last for more than 3 minutes and in one quarter of cases for hours. One or more of these symptoms can predominate or be absent. Eyes can remain open without deviation, ictal vomiting might not occur, and autonomic and behavioral disturbances can predominate, particularly in the early stages of the ictus, and be missed in nocturnal seizures. Age at onset is 5 years, with a singular or a median of three seizures, which are predominantly nocturnal. Interictal electroencephalography (EEG) frequently shows occipital paroxysms or occipital spikes but one-fifth of the cases have only extraoccipital spikes on normal EEG. Treatment might not be needed. Panayiotopoulos syndrome, like rolandic epilepsy, needs recognition by the general pediatrician because of the invariably excellent prognosis and also because it can be misdiagnosed as an acute cerebral insult.
We studied the early-onset variant of benign childhood epilepsy with occipital paroxysms (EVBCEOP) proposed by Panayiotopoulos, to confirm whether his five criteria are sufficient to delineate EVBCEOP as a new epileptic syndrome, as well as to predict a good outcome prospectively at the time of the first examination.
The subjects were 649 children with localization-related epilepsies (LREs) observed in our hospital for >4 years.
We applied the International Classification of Epilepsies and Epileptic Syndromes to the 649 patients and identified patients who had EVBCEOP from among those with nonspecific idiopathic LRE. The inclusion criteria were to satisfy all five criteria and all but one criterion (i.e., either ictal vomiting or occipital EEG paroxysms). We were blind as to the outcomes and selected patients who satisfied the following three of the five criteria at the time of the first examination, (a) normal development before the onset, (b) epilepsy onset age between 2 and 8 years, and (c) occipital EEG foci. We attempted to determine whether the outcome can be predicted prospectively, and whether the presence or absence of ictal vomiting affects the prognosis.
We identified 19 patients who satisfied all five criteria, 22 who exhibited all but occipital EEG foci, and 21 who exhibited all but ictal vomiting. The incidence of status convulsivus was higher in those with ictal vomiting than in those without ictal vomiting (p < 0.05). Interictal EEG performed every 6 months showed shifting and multiplication of EEG foci in 42 and 52% of all subjects, respectively. We identified 57 patients, 42 (74%) of whom were in remission by age 12 years. The number of patients who experienced remission did not differ significantly between those with (76%, n = 25) and without (72%, n = 32) ictal vomiting (p > 0.05).
Nosologically, EVBCEOP appears to constitute the earliest form of idiopathic epileptic syndrome different from classic BCEOP. However, its clinical spectrum, ranging from the absence of ictal vomiting to a combination of extraoccipital and multifocal EEG foci, is broad, such that further prospective study is expected to reveal the exact prerequisite criteria for determining the border of this epileptic syndrome and for clarifying the clinical spectrum within this syndrome.
Twenty-six patients were studied who had the clinical and electroencephalographic features of benign childhood epilepsy with occipital paroxysms (BCEOP) as defined by the Commission of the International League Against Epilepsy (ILAE). Twelve patients were characterized as having early-onset benign childhood occipital seizures (EBOS) susceptible syndrome, as described by Panayiotopoulos, and 14 patients had late onset childhood idiopathic occipital seizures (LOS). Patients with symptomatic epilepsy and whose EEGs exhibited occipital spikes were excluded. The age of onset of the EBOS group ranged from 2.6 to 9.4 years (mean: 4.9+/-1.7 years), which was significantly younger than the LOS group (range: 4-12 years, mean:8.4+/-2.5 years). Both sexes were equally affected. The patients in the EBOS group had less frequent and longer seizures, ictal vomiting, more frequent deviation of the eyes, adversive seizures and more frequent nocturnal and secondary generalized seizures (P<0.05). By comparison, patients in the LOS group had a higher incidence of seizures, shorter duration of seizures and more frequent diurnal onset (P<0.01); also, although not statistically significant, the LOS group had more frequent visual hallucinations and headaches. The EEG topography in both groups showed at either side of occipital area typical paroxysms that were unilateral or bilaterally synchronous. Neither group had dipoles according to scalp voltage mapping. The clinical prognoses were favorable for both groups. To distinguish EBOS from LOS, detailed description of the age of onset, motor symptoms, visual symptoms, presence of eye deviation and diurnal or nocturnal occurrence are essential.
We prospectively studied the early-onset benign occipital seizure susceptibility syndrome to confirm the benign prognosis. The patients were 37 children followed for more than 2 years after meeting the following criteria on the first examination: (1) normal development before the onset of epilepsy, (2) onset between 1 and 8 years of age, (3) normal brain MRI and cranial CT findings, (4) partial seizures manifested both initial ictal vomiting and tonic eye-deviations, and (5) normal background activity with or without epileptic EEG foci regardless of location. The incidence and clinical characteristics of seizures, response to treatment, and EEG findings were analyzed. The total number of seizures ranged from one (n = 6) to 27 times, with a median of five times. Recurrent prolonged attacks resistant to antiepileptic drugs were recognized in 15 children, who had earlier onset of epilepsy and more frequent complications than the remaining 22 children. Interictal EEG revealed occipital foci in 26 children, 17 of whom later revealed a shift in predominant foci. At the final examinations, 28 patients had been seizure-free for at least 2 years. The clinical picture of this syndrome ranges from those with a few seizures to those with recurrent prolonged seizures initially resistant to antiepileptic drugs despite ultimate remission by 12 years of age.
Magnetoencephalography/magnetic source imaging in a case of atypical benign partial epilepsy of childhood and in a sibling with rolandic epilepsy
- Sugita Ki
- K Sugita
- M Kubota
- Y Tanaka