Abstracts

Rationale: The value of individual ictal motor signs in lateralization of focal epilepsy has been analyzed extensively. We studied the occurrence of two or more motor signs in secondarily generalized motor seizures and determined its sequence and utility in lateralization of the epileptogenic zone (EZ).Methods: The material consisted of patients with focal epilepsy admitted to our epilepsy monitoring unit between 2009 and 2014, whose evaluation showed secondarily generalized motor seizures. Patients with bi-hemispheric epilepsy or ill-defined EZs were excluded. One representative seizure per patient was selected and analyzed by three independent observers. Only signs with agreement between ≥ 2 readers were included for analysis. Inter-observer agreement was verified with kappa indices and a positive predictive value (PPV) was calculated determining each sign’s reliability to accurately lateralize the EZ. Signs with PPV ≤ 80% were excluded from evaluation of the motor sequence. We then analyzed the sequence of motor signs and its predictive value for lateralization of the EZ.Results: A total of 47 seizures were studied. The motor signs with a robust lateralizing value were version (36 patients, kappa 0.6961, PPV-97%), unilateral tonic seizure (24 patients, kappa 0.2594, PPV-96%), M2e (21 patients, kappa 0.7364, PPV-100%), unilateral clonic seizure (10 patients, kappa 0.3643, PPV-90%), asymmetric clonic ending (28 patients, kappa 0.6761, PPV 89%) and Todd’s paralysis (6 patients, kappa 0.4360, PPV 83%). Figure-of-4 (23 patients, PPV-74%) and hand dystonia (6 patients, PPV-67%) had a relatively low PPV and, therefore, were not included in the following sequence analysis which included only 37 patients with ≥ 2 motor signs of high PPV . Multiple combinations of temporal progression of motor signs were seen in these 37 patients, with version being the most common initial motor sign (29/37 patients) usually followed by M2e (15/37 patients) and/or a focal tonic seizure (7/37 patient). Accurate lateralization of the EZ with a PPV of 100% can be predicted when 2 or more reliable motor signs, point to the same side. However, the various sequences of reliable motor signs did not differentiate between temporal and extratemporal epilepsy.Conclusions: Motor signs with a high predictive value for lateralization included version, unilateral tonic, unilateral clonic, M2e, asymmetric clonic ending and Todd’s paralysis. Figure-of-4 and hand dystonia, however, had a low PPV. In this study the combination of ≥ 2 signs pointing to the same side predicted lateralization with 100% certainty. Version was the most likely initial sign of the pre-secondary generalization motor sequence followed by M2e or a tonic seizure. The order of a sequence of motor signs was not useful in localizing the EZ.