THE FUNCTIONAL-ORGANIZATION OF THE INTERICTAL SPIKE COMPLEX IN BENIGNROLANDIC EPILEPSY

Purpose: We studied the functional organization of the interictal epil eptic spike complex in patients with benign rolandic epilepsy of child hood (BREC). Methods: We recorded interictal epileptiform spikes and s omatosensory evoked potentials after median nerve stimulation, providi ng a biologic marker for the location of the central sulcus in 12 pati ents with BREC. We used multiple dipole modeling to assess the number, the three-dimensional intracerebral location, and the time activity o f the underlying neuronal sources. Results: Although the interictal sp ike complex could be modeled by a single tangential dipolar source in seven patients (group 1), in the remaining five patients, two sources- a radial and a tangential dipole-were necessary adequately to explain the interictal spikes (group 2). The tangential source was located dee per than the radial source and was characterized by a frontal positivi ty and a centroparietal negativity with a phase reversal across the ce ntral sulcus, suggesting that the interictal spikes originated in the anterior wall of the central sulcus. The radial source showed a single electronegativity over the ipsilateral central region, which would be compatible with involvement of the top of either the pre- or postcent ral gyrus. Both sources showed biphasic time patterns with an average latency difference of 30 ms. Conclusions: Our results indicate that in some patients with typical BREC, the interictal epileptiform spike co mplex is generated by multiple, simultaneously active neuronal populat ions within the central region and that epileptiform activity is propa gated between these two adjacent cortical areas.