Abstracts

Baclofen has been associated with the occurrence of epileptic seizures and status epilepticus in a small number of cases. An increased frequency of epileptic events were seen in patients with posttraumatic brain injury on intrathecal baclofen (ITB), predominantly after initiation of therapy or dose adjustements. The goal of our study was to investigate the incidence of epileptic seizures in a series of 99 patients with multiple sclerosis (MS) treated with ITB.
Data were obtained from the Mellen Center ITB Therapy Registry. The registry contains records of all patients since 1990 with a definite diagnosis of MS who had an ITB pump implanted.
Ninety-nine patients, 31 male and 68 female, underwent implantation of a baclofen pump between 1990 and 2002. Mean age at pump implantation was 46.3 years, mean disease duration 16 years. Mean baclofen rate at the most recent visit was 327.7 mcg/d. 89% percent of patients were non-ambulatory with an EDSS [ge] 7.0. A total of 297 cumulative pump years were reviewed. Epileptic seizures were noted in eleven patients, 2 male and 9 female. Mean age at pump implantation in this group was 47.1 years, mean disease duration 17 years. The mean ITB rate at onset of seizures was 382.5 mcg/d and 372.3 at last visit. Patients were followed on average four years after pump implantation. Four patients had pre-existing epilepsy, but no increase in seizure frequency was detected during the follow-up period. Seven patients had new onset of epileptic seizures on average 2 years and 3 months after initiation of ITB therapy. Five patients had single seizures, all associated with additional aggravating factors: two patients had a febrile illness; baclofen overdose, perioperative state and low serum sodium was seen in one patient, respectively. Two patients developed recurrent seizures, more than 3 times per year. Three patients developed status epilepticus.
In our registry of 99 patients, we observed the new onset of epileptic seizures in 7% of patients within an average follow-up period of four years, often associated with additional factors increasing their seizure susceptibility. None of the four patients with pre-existing epilepsy had worsening of their seizure frequency. In epidemiologic studies, patients with Multiple Sclerosis show a threefold increase in risk for developing epilepsy compared with the general population. The cumulative risk for developing epilepsy after onset of MS symptoms is estimated 3.1% by 15 years disease duration. ITB therapy seems to bear a definite risk for epileptic seizures in MS patients.
[Supported by: Innovative Medizinische Forschung, WWU Muenster (FoeKz. LO 610101, Dr. Loddenkemper; FoeKz. KE 620201 , Dr. Kellinghaus)]