INTRODUCTION

 

Epilepsy is characterized by the spontaneous periodic occurrences of seizures and affects nearly 1-2% of the general population. Etiologically, epilepsy is either symptomatic secondary to structural brain changes or idiopathic; that is mostly genetic. Experimental evidence in rodents have showed the ability of different brain insults as trauma, stroke and febrile seizures, to induce inflammation in the brain¹. The clinical observation of the efficacy of selected anti-inflammatory drugs; like steroids to control seizures that are resistant to anti-epileptic drugs, has marked a list of studies that incriminated inflammation in the etiopathogenesis of symptomatic epilepsy.² Cytokines are chemical mediators of inflammation and immune responses. The interleukin (IL) -1β was found to be linked to seizure susceptibility and epileptogensis. Its administration in experimental seizure models has worsened the seizure activity while its depression, suppressed this activity.³ Most of clinical studies on IL-1β were done on patients with chronic symptomatic epilepsy and its results are still controversial. The aim of this study was to examine IL-1β in patients with idiopathic epilepsy and those with newly diagnosed epilepsy immedietly following seizure activity to understand its pathological role.

 

PATIENTS AND METHODS

 

Patients with idiopathic epilepsy admitted to Neurology department, Mansoura University for investigation or treatment, were recruited if they develop in hospital -spontaneous epileptic seizure activity for less than 5 minutes. Patients were selected to serve two main groups; newly diagnosed epilepsy and chronic epilepsy. Patients with an evidence of status epilepticus, recent trauma, electrolyte imbalance, history of drug intoxication, acute neurological diseases, inflammatory, metabolic or neoplastic diseases were excluded from the study.  Evidence of infection was excluded by history, clinical examination and C-reactive protein assessment. A group of patients with cryptogenic epilepsy served as control. All patients didn’t experience another seizure within 24-hours of the index seizure. All patients had Magnetic resonance imaging (MRI) of the brain using a high resolution 1.5 Tesla MRI scan and reported to be normal. Plasma samples were collected within 6 hours of the index seizure. Another plasma sample for 20 patients 24-hours after the index seizure to detect the basal level of IL-1β. The serum samples were immediately centrifuged and frozen at -80 C. IL-1β were measured by commercially available ELISA (Enzyme Linked Immunosorbent Assay) kits (Human IL-1β ELISA Kit, Boster Biological Technology Ltd) according to the manufacturers’ instructions.

 

Data entry and statistical analyses were performed using SPSS (statistical package of social sciences) version 16.0 (SPSS Inc., Chicago, IL, USA). Parametric data were expressed in mean ± standard deviation. Non parametric data were expressed in median, minimum and maximum. Normality of data was first tested by one sample K-S test. In addition, independent t test was used to compare means for continous parametric variables of each two different groups. Also, Mann-Whitney U test (z) was used to compare non parametric continuous variables in two different groups. Pearson Chi-square tests were used to compare the categorical variables between the both cases and control groups. P-value < 0.05 was considered as statistically significant.

The study was approaved by the Neurology departmental council and the ethical committee for research of Mansoura Faculty of Medicine.

 

RESULTS

 

Sixty patients were recruited for the study. Four patients were excluded because of sample lyses and 56 patients were considered for statistical analysis. The clinical characteristics of patients are presented in Table (1). Seven patients (12.5%) were considered cryptogenic because they had secondary generalized tonic-clonic seizures (sGTCS) after complex partial seizures (CPS) and their MRI were normal. Polytherapy was found in half of the patients reflecting their drug-refractory pattern. Table 2 and 3 summarizes IL-1β results in different situations. Patients with seizure onset within the last 6 months were considered new onset epilepsy. IL-1β was significantly higher than those of the normal population (P<0.001*). The normal concentration of IL-1β reported in healthy general population is 0.3pg/ml.(4,5). To know if this is the basal level, we reassessed 20 patients 24 hours after the index seizure. The level significantly dropped but still significantly higher than normal concentrations (P=0.003*). The rise of IL-1β following the index seizure was significantly higher among adults when compared to children (P=0.01*). The levels of IL-1β were not significantly different between idiopathic epilepsy and cryptogenic type, new-onset epilepsy and chronic one, and childhood-onset and adult- onset. The level was also not significantly increased with higher seizure frequency or poly therapy.

 

Table 1. The clinical characteristics of the studied patients.

 

Variables	Patients (N=56)
Age (median and range in years)	18.5 (3-65)
Gender (male/female)(%)	38/18(67.9/32.1)
Duration of epilepsy(median and range in years)	1.5 (0.08-28)
Etriology of epilepsy ·                  Idiopathic (N&%) ·                  Cryptogenic (N&%)	49 (87.5) 7 (12.5)
Seizure frequency (median/month)	3.5
Type of seizure: ·                  GTCS ·                  sGTCS	49 (87.5) 7 (12.5)
Number of AEDs ·                  monotherapy ·                  polytherapy	28 (50%) 28 (50%)
IL-1β after index seizure (pg/ml) (median +/- SD)	4.7 (1.28)

 

Table 2. IL-1β essay in different time points from index- seizure  compared to normal population, to each other and with their age & gender differences.

 

IL-1β	(N)	Mean	Std. Deviation	P value
-6 hours of index seizure	56	4.7460	1.28486	<0.001*
-24 hours of index seizure	20	1.9849	0.56676	<0.001*
-6 hours -24 hours	20 20	5.0200 1.9849	1.33549 0.56676	<0.001*
Pediatrics Adults	28 28	4.4549 5.1436	1.09548 1.28601	0.03*
Male Female	38 18	4.7479 4.9044	1.15224 1.42066	0.6

 

Table 3. IL-1β in different epilepsy variables.

 

	IL-1β	N	mean	Std Deviation	Value
Age of onset	<15 >16	50 6	4.8112 4.6900	1.26064 1.07553	0.8
Duration of epilepsy	New-onset Chronic	27 29	4.8474 4.7524	1.40299 1.07620	0.7
Etiology	idiopathic cryptogenic	49 7	4.8759 4.2543	1.23746 1.14489	0.2
Seizure frequency/month	<2 >2	21 35	4.6810 4.6868	1.43718 1.11093	0.5
Number of AEDs	Monotherapy Polytherapy	28 28	4.9886 4.6079	1.38100 1.05780	0.2

 

 

DISCUSSION

 

Epilepsy is chronic medical illness irrespective of the current treatment with AEDs because they don't work with every patient with epilepsy. Even those, who responded to AEDs, have a nearly 50% chance of seizure recurrence within 10 years.⁶ This clinical observation suggests that the locus of control of epilepsy is outside the repertoire of AEDs. One plausible hypothesis for seizure recurrence is brain inflammation and because epilepsy has enduring predisposition to generate seizures, a relationship between the later and inflammation was the focus of several research works. Studies have shown that inflammation, irrespective of its cause, can cause seizures and also seizures can cause inflammation. In this study, we measured the level of IL-1β in the sera of patients with idiopathic epilepsy whether new onset or chronic one. The study showed significant rise of IL-1β immediately following seizure activity suggesting cause-effect relationship. In animal epilepsy models, seizure induction by different electrical and chemical stimuli triggered rapid induction of inflammatory mediators in brain regions of seizure activity onset and propagation^7-11. The proinflammatory cytokines like IL –1β and their receptors are expressed in neurons as well as microglia and astrocytes.¹² Clinical studies in temporal lobe epilepsy and extratemporal lobe epilepsy has shown evidence of increased interleukin-1 receptor antagonist (IL-1Ra), which is mainly induced by IL-1β reflecting the activation of IL-1 system^3,13,14. However most of the studies failed to show rise of IL-1β either because of the time of assay or the small rise. Peltola and his group's assay on patients with primary generalized or secondary generalized seizures showed no significant rise when they did the assay 72- and 24-hours following seizure activity^15,16. While Uldag et al. found significant rise of IL-1Ra, within 12 hours from seizure activity, but the ratio of IL-1β/IL-Ra has not changed suggesting increase of IL-1β level. They attributed that to the small and rapid rise of IL-1β that was overcome by increased IL-Ra activity.³

We re-assayed the plasma level of IL-1β after 24-hours of the index seizure and it significantly decreased confirming the short-lived response as suggested by Peltola et al.^15,16. However the basal level attained by 20 patients after the index seizure is significantly higher than normal population. This could reflect a state of mild chronic inflammation in epileptic patients that facilitate occurrences of seizures. In a nice review about the role of inflammation in epilepsy, Vezzani et al. suggested three different mechanisms through which, brain inflammation might lead to seizures; all has involved IL-1β. The first is the positive evidence that IL-1β, TNF, IL-6, prostaglandin E2, and complement cascade can generate and perpetuate seizures. The second evidence is also mediated by IL-1β as a response to fever that accompany most inflammatory processes as happens in febrile seizures and the later development of mesial temporal sclerosis and temporal lobe epilepsy. The third evidence came from a systemic injection of inflammation–inducer; lipopolysaccharide into rats lowering their seizure threshold and electrographic discharge in animal model of petit mal epilepsy. These changes were also brought by the effect of brain cytokines; namely IL-1β or TNF. ¹⁷

The rise of IL-1β, in our results was not significantly changed by seizure frequency, epilepsy duration or the number of AEDs. This is in agreement with Uludag et al whose cases were both idiopathic and symptomatic epilepsy. That finding denotes that inflammation and its cytokine generators starts very early during the process of epileptogenesis.

In this study we ascertained the involvement of IL-1β as a seizure response and a possible role in seizure generation in patients with idiopathic epilepsy. We didn't measure IL-6 and the IL-1Ra that reflects the rest of interleukin activity. We also didn't do CSF assay of these cytokines that reflects more brain activity because of the cost and the invasive technique of the later.

We conclude that IL-1β is seizure-related in idiopathic epilepsy and presumably its pathogenesis and introducing it as a possible target in epilepsy management.

 

[Disclosure: Authors report no conflict of interest]

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