A study of unilateral brief focal atonia in childhood partial epilepsy

We studied unilateral brief focal atonia (BFA) in seven patients with childhood partial epilepsy. BFA was observed as a transient dropping of one arm lasting from 100 to 150 ms when patients were asked to keep both arms outstretched in front of the body. Close examination using simultaneous video-polygraphic recordings showed dropping of the arm to correspond exactly with a single sharp and slow wave complex arising from the contralateral centrotemporoparietal region. The BFA occasionally would progress to atonic seizures or atonic absence seizures, when the localized epileptic discharge evolved into generalized discharges. In one patient we found a positive correlation between the intensity of BFA and the amplitude of the contralateral epileptic discharges. A higher amplitude corresponded to more pronounced BFA and a lower amplitude to less pronounced BFA. These results led us to conclude that the apparently interictal single sharp and slow wave complex in the rolandic region may inhibit contralateral motor control, thus producing BFA that corresponds with the spike amplitude.