Semiology Lateralizing value (PPV) Symptomatogenic zone Mechanism Homonymous hemifield visual aura or defect 100% Brodmann areas 17-19 Activation Unilateral ictal paresis or immobile limb 100% Negative motor areas Activation Forced head version less than 10 second before secondary generalization > 90% Brodmann areas 6 & 8 (frontal eye and motor areas) Activation Unilateral ictal dystonia > 90% Spread from seizure onset zone to ipsilateral basal ganglia Activation Postictal (Todd’s) palsy > 90% Brodmann areas 4 & 6 (primary motor area) Exhaustion/ Inhibition Fencing posture 90% SMA  Activation Figure-of-4 sign (Asymmetric tonic limb posturing) ~ 90% SMA/ Prefrontal area Activation Unilateral tonic activity ~ 90% SMA/Brodmann area 6 Activation Unilateral sensory or painful aura ~ 90% Brodmann areas 1, 2, 3 (primary SSA) Activation Unilateral clonic activity > 80% Brodmann areas 4 & 6 (primary motor area) Activation Emotional facial asymmetry > 80% Unknown Unknown Epileptic nystagmus N/A Posterior head regions Unknown PPV: Positive Predictive Value; SMA: Supplementary Motor Area; N/A: Not Assigned.

Table 1: Localizing semiologic findings pointing to the contralateral location (for the epileptogenic zone).