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|Year : 2000 | Volume
| Issue : 4 | Page : 357-60
Risk of recurrence of seizures following single unprovoked idiopathic seizure.
Das CP, Sawhney IM, Lal V, Prabhakar S
Department of Neurology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India.
Department of Neurology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India.
A prospective study was conducted to look for various factors that could predict the risk of recurrence of a single unprovoked idiopathic seizure. Seventy six patients with a history of single episode of seizure ultimately completed the study and the data regarding age, sex, duration of seizure, time of occurrence of the ictus, interval between onset and referral, family history of seizure and alcohol consumption were analysed. All patients of symptomatic epilepsy and those with an abnormal scan were excluded. The patients were randomized into two groups, one of which received anti epileptic medication and the other did not. All patients underwent electroencephalography (EEG). Twenty two (M=16, F=6) of the 76 patients (M=56, F=20) had a recurrence of seizure. The duration of seizure at initial presentation was 10.1 +/- 5.2 min. in the recurrence group and 6.5 +/- 4.1 min. in the non-recurrence group. Twelve of the 16 patients with an abnormal EEG had a recurrence whereas only 10 of the 60 patients with a normal EEG had a recurrence (p <0.001). Of the treated cases (n=36), only 4 had a recurrence compared to 18 of the untreated cases (n=40) (p <0.002). Eighteen of the 22 cases having a recurrence did so within three months. Six of the cases with family history of seizure (n=10) had a recurrence, whereas only 16 of the cases without family history of seizure (n=16) had a recurrence (p <0.05). Patients of a single unprovoked idiopathic seizure with a normal CT scan are less likely to have a recurrence if the duration of seizure at presentation is short, EEG is normal, more than 3 months have passed since the first seizure and if treatment has been started. Family history of seizures does have a moderately significant bearing, but alcohol intake does not increase the chances of seizure.
|How to cite this article:|
Das C P, Sawhney I M, Lal V, Prabhakar S. Risk of recurrence of seizures following single unprovoked idiopathic seizure. Neurol India 2000;48:357
The incidence of single seizure in general population is 5%, whereas epilepsy develops in 1-2% people. A single seizure does not constitute epilepsy which is defined as atleast 2 episodes of unprovoked seizures 24 hours apart. Most of the studies have shown that approximately one third of patients with single seizure will experience a second one., Data regarding recurrence vary widely. Recurrence rates as high as 58-80% have been reported., In a prospective study, Hauser et al estimated the risk of recurrence to be 14%, 29% and 34% at 1, 3 and 5 years respectively following the first episode. Anticonvulsant medication did not decrease the risk of recurrence. This study addresses the influence of various factors on recurrence of a single unprovoked idiopathic seizure with regards to timing and duration of seizure, family history of seizures, alcohol intake, EEG abnormality and effect of anticonvulsant medication.
Between 1996-99, patients of single idiopathic generalized seizure were recruited from the neurology outpatient of the Postgraduate Institute of Medical Education and Research, Chandigarh. Patients with a history of febrile seizures or unprovoked seizure (e.g. absences in childhood) in the past were excluded. Patients with symptomatic epilepsy with history of perinatal asphyxia, CNS infection, head trauma, stroke, mental retardation, cerebral palsy, and presence of focal neurological deficit, were also excluded from the study.
Detailed data was collected in 100 patients, who presented with single unprovoked seizure. Age, sex, type and duration of seizure, time of the occurrence of ictus, interval between onset and referral, family history of seizure in first degree relatives, and alcohol consumption were recorded. A positive history of alcohol intake mandated a frequency of more than twice a week and a quantity of more than 60 ml in a single sitting. All the patients were subjected to EEG and CT scan. Five categories of EEG findings were evaluated (i) generalized spike and wave (GSW) patterns regardless of symmetry, repetition and rate, (ii) focal epileptiform (sharp waves or focal spikes, multifocal spikes) activity, (iii) focal slowing (unilateral polymorphic or rhythmic), (iv) nonspecific theta or delta slowing regardless of symmetry. Seventeen patients with an abnormal CT scan (neurocysticercosis - 11 cases, tuberculoma - 4 cases, infarct and arterio-venous malformation - one each) were excluded from the study, and 7 cases were lost on follow up. The remaining 76 patients were interviewed alongwith one attendant and explained the risks and benefits of anticonvulsant therapy as well as controversy regarding treatment of a single seizure. They were randomized into two groups : one treated and the other untreated, after obtaining a written consent. All patients were followed up for recurrence at monthly intervals for 3 months, then quarterly for 1 year and once in 6 months thereafter, for a period ranging from 12-24 (mean 19.1+5.00) months. The data collected was analyzed by applying the Chisquare test. 'p' values were calculated and compared in the group having recurrence of seizure versus those who did not have recurrence.
Of the 76 patients (M-56, F-20), 22 patients (M-16, F-6) had a recurrence [Table I]. The age distribution of the two groups is shown in [Figure. 1]. In the recurrence group there was a longer duration of seizure at presentation whereas in the group without recurrence a descending trend in number of cases was noted as the duration of seizure at presentation increased [Figure. 2]. The mean duration of seizure in the recurrence group was 10.1+5.2 minutes as opposed to 6.5+4.1 minutes in the group not having a recurrence and the values were statistically significant [Table I].
Twelve of the 40 cases having an ictus in the morning hours had a recurrence, the mean time of initial seizure being 6.57+4.1 a.m. In similar fashion 10 of the 36 cases of evening seizures having an ictus at 8.12+2.16 p.m., later on had a second episode. The `p' value for the effect of family history of seizures on recurrence was moderately significant, whereas that of alcohol intake was not related as depicted in [Table I]. Twelve of the 16 patients with an abnormal EEG had a recurrence whereas only 10 of the 60 patients with a normal EEG had a recurrence. Thus EEG abnormality attains significant value as a risk factor of recurrence [Table I]. Of the various EEG abnormalities, generalised spike wave discharges has the highest propensity for recurrence [Table II]. Four out of the 36 treated cases had a recurrence as opposed to 18 out of 40 untreated cases and the results were statistically significant [Table I]. All 4 of the treated cases had a recurrence in the first 2 months whereas more than half (10 out of 18) untreated cases had a recurrence after 2 months. Most of the cases (18 out of 22) had a recurrence within first three months [Figure. 3].
In both the groups (recurrence vs non-recurrence) males outnumbered females. This is because of a selection bias in a hospital based study, in a developing country, where more males report to the hospitals than females because of socio-economic reasons. However, the rates of recurrence are similar (males : 16 out of 56, females : 6 out of 20). The same conclusion has been drawn in 4 different studies.,,, One study showed that the risk estimates for males and females were within a percentage point of each other. When patients were grouped as per age, we found that the proportion of recurrences were higher in those in the 4th and 5th decades [Figure. 1]. Although most studies reveal that age at the time of first seizures is not a predictor of recurrence risk, Hopkins et al reported a slightly higher risk in patients who were over 50 years of age at the time of the first seizure. Hirtz et al, however, reported a higher recurrence risk in children who had focal motor seizures with onset under 2 years of age. Hopkins et al have shown that the risk of subsequent seizures was higher if the initial seizure occurred between the hours of midnight and breakfast time than at any other time of the day. In the present study, the proportion of recurrence of initial seizure occurring in the morning hours (12/40) were similar to that where the ictus developed later in the day (10/36). However, the duration of seizure at presentation was longer in the recurrence group reflecting a more severe neural insult, which may have a propensity to incite a second attack.
As in 6 different studies a family history of seizure was not found to be a significant factor for recurrence in the present study as reported earlier.,,,,, However, Hauser et al found that a history of epilepsy, is sibling was a definite risk factor. Unlike other studies they did not take into account seizures in second and third degree relatives. Our study included family history of seizures in first degree relatives only and hence the 'p' value was moderately significant (p <0.05). History of alcohol intake was not found to be a significant predictor for recurrence in our study possibly due to the wide spread stigma associated, which may have prompted patients to considerably lower the amount and frequency of alcohol intake, and thus not fulfilling the criteria set. An abnormal EEG was found to be a significant factor for recurrence (75% versus 16% in cases with normal EEG). In three other studies, the pooled risk of recurrence was 58% with an abnormal EEG as compared to 27% of cases having a normal EEG.,,
Epileptiform abnormality did not significantly alter the rate of recurrence, possibly because of inclusion of cases with a structural brain lesion in the study, some of whom might have had a small lesion to have a normal EEG, despite provoking a second seizure. The relevance of EEG has also been questioned by Gilad et al. The study included only 17 cases of unprovoked single seizure. In the present study, both generalized and focal spike wave discharges were associated with recurrence, although only the former contributed to recurrence in the study by Hauser. Treatment is associated with a significant drop in the rate of recurrence. Some studies have failed to show any significant difference in treated and untreated groups,, whereas others have showed a mild increase in recurrence rate with treatment. This is possibly due to difference in selection criteria e.g. including patients of a structural lesion having a first attack, and obtaining cases from the emergency services where a minor prior episode may not be forthcoming. This would increase the incidence of recurrence later on. The adequacy of anticonvulsant dosage has a significant inter-individual variation and failure to abort a second attack, should not be construed as lack of efficacy. Recent trials involving only patients with single unprovoked seizure, as in the present study have shown a 2.8 times higher hazard ratio of recurrence in the untreated group, and the benefits of treatment are more evident in male patients.
There is a dilemma whether a single unprovoked idiopathic seizure should be treated or not. The decision should be individualized depending upon the risk of recurrence, occupation, and social circumstances. The present study shows that the duration of seizure at presentation and EEG abnormalities can be correlated with possible recurrence. Most of the recurrent seizures occur in the first three months and their incidence decreases with treatment.
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