Abstracts

Rationale: Unilateral ictal dystonic posturing (DP) is the most reliable lateralizing sign in temporal lobe epilepsy (TLE), particularly in patients with mesial temporal sclerosis (MTS). Basic neurosciences data have suggested the hypothesis that DP could be the expression of an alternative network which might halt generalization. During prolonged video-EEG monitoring for pre-surgical evaluation of refractory seizures, antiepileptic drugs (AED) withdraw is a frequent procedure, which may, however, facilitate secondary generalization (SG). In this study we aimed to analyze the impact of AED withdraw on the frequency of SG in patients with and without DP.Methods: Five-hundred twenty-seven seizures of 171 patients with TLE-MTS submitted to prolonged video-EEG monitoring were reviewed. Patients under 15 years and those with other lesions besides MTS in MRI were excluded. Timing of seizure occurrence according to AED withdraw and frequency of SG and DP were analyzed. To assess the effect of AED withdraw, medical records during VEEG monitoring were reviewed with respect to AED prescription. Patients without AED for a period longer than five half-lives of the drug were considered as off-AED . Results: Seventy-nine of 527 seizures evolved to SG. DP was observed in 162 seizures. SG occurred more often in seizures without DP (67/365; 18.4%) when compared with those with DP (12/162; 7.4% p = 0.001). With respect to AED withdraw, SG was more frequently observed during AED withdraw (65/72; 7.8%) and off-AED seizures (6/72; 8.1%) than in seizures which occurred when AED were in habitual dosing (3/72; 4.1%; p<0.0001). No SG occurred associated with DP while the patients were taking the habitual AED dosing. In contrast, 12/72 seizures with DP (100%) evolved to SG during AED withdraw. No SG preceded by DP occurred in off-AED period . The reduced number of seizures occurred in off-AED and habitual AED dosing compared with those in AED withdraw did not allow for statistical comparison . Conclusions: DP in seizures of patients with TLE-MTS appears to protect from SG. This holds true during video-EEG monitoring, when AED withdraw is associated with increased frequency of SG.