Effect of Natalizumab on seizure frequency and EEG tracks. A. Bars indicate the number of episodes of partial (yellow) and generalized (blue) seizures along the 10-years period. After natalizumab introduction (arrow), the number (Y axis) of partial seizure dramatically dropped from 10 to 4 (60% reduction), while generalized seizures disappeared. T-test (two-tailed 95% confidence interval) was used to test the null hypothesis (number of seizures after the start of natalizumab is not different from the mean of the 2002-2008 period). Mean values were 6.71 ± 2.21 (95% CI 3.22-5.62) for partial seizures and 4.43 ± 1.81 (95% CI 5.24-8.17) for generalized seizures, respectively. One tailed p-values are 0.003 for partial (*) and 0.00004 for generalized (**) seizures, allowing to strongly reject the null hypothesis. B. Intercritical scalp EEG recording (18'' duration) of the case, performed while awake on July 2008 and showing a reactivation of a focus of sharp waves and low-amplitude slow activity over the left fronto-temporal region, which correspond to a complex partial seizure accompanied by gestural automatisms. The patient was on therapy with GA and on poly-AEDs treatment (oxcarbazepine 2400 mg/day, levetiracetam 3000 mg/day and gabapentin 900 mg/day). C. Intercritical scalp EEG recording (18'' duration) performed on June 2009 while awake, showing minimal low-amplitude slow activity over the left fronto-temporal region. The patient was on therapy with natalizumab and on poly-AEDs treatment with levetiracetam 2000 mg/day (33% reduction) and gabapentin 900 mg/day. Scalp EEG recording set up: PA filter 0.53 Hz; PB filter 30 Hz, amplitude 70 microvolt/cm. Electrode placement refers to the Jasper's 10-20 system. EKG = electrocardiogram.