Prophylactic antiepileptic treatment reduces seizure frequency in natalizumab-associated progressive multifocal leukoencephalopathy

Little is known about seizures in natalizumab-associated progressive multifocal leukoencephalopathy (NAT-PML). Methods: A review of clinical records of 15 NAT-PML patients with multiple sclerosis (MS) treated at a German university hospital. Results: Some 53% (8/15) of our patients developed seizures with often multiple semiologies (seven grand mal, three simple partial motor and two psychomotor seizures). Series of seizures or status epilepticus occurred in seven of these eight. Seizure onset was on average 61 days after onset of NAT-PML and was associated with immune reconstitution inflammatory syndrome (IRIS) in five of eight patients. After having observed severe seizures during NAT-PML in seven of our first nine patients, we started preventive antiepileptic treatment (PAT) with levetiracetam (1000–1750 mg/day). Patient subgroups analyzed for seizures and PAT did not differ in baseline characteristics. Only one of six patients, who received PAT, had a seizure compared with seven of nine patients without PAT (2-tailed Fisher's exact test, p = 0.04). Although the small sample size and retrospective nature of the study are limitations, we propose to treat NAT-PML patients with PAT early after diagnosis, as seizures seem to be common and severe in NAT-PML.