• Ratio of patients who are free of seizure between H3 and H24 in both groups.
  

• Items 1,2,3 of the Clinical Global Impression scale.
  
• Side effects during the study.
  
• Time between H0 and the last seizure.
  
• Type and ratio of epileptic fit between H0 and H24.
  
• Number of seizures occured between H3 and H10, H10 and H17, H17 and H24, corresponding to the half-time of the treatment (7 hours).
  
• Description of therapeutic adaptation at 1 month after patient enrolment.
  

Seizure clustering has been defined as a series of unusual frequency of seizures with return to baseline between events. The most common definition of cluster seizure is three seizures per 24 hours.

The usual treatment of cluster seizure is benzodiazepin. This is recognized efficient therapy but has many side effects. Thus it is important to develop as an new therapeutic to improve patient care. Levetiracetam is an antiepileptic drug used in addition to other antiepileptic drugs with less side effects than benzodiazepin.

The aim of this study is to evaluate the effectiveness and safety of levetiracetam in epilepsy cluster seizure.

This is a double blind, placebo controlled, add-on clinical trial with two phases :

Phase 1 : Double blind phase during 24 hours (H0 to H24). After consent signature and randomization, the patient takes two tablets of levetiracetam or placebo. If the patient has a seizure between H3 and H24, he is considered as a non-respondent patient. If there is a risk of rapid evolution to an statue epilepticus, the investigator can break the blind and adapt the patient treatment accordingly.

Phase 2 : This is an open phase after H24. this phase consists of breaking the blind with free adaption of the therapy by the investigator, and patients follow-up during 1 month.

The randomization is stratify by center. The size of randomization blocks is random because of the systematic breaking blind after 24 hours.