[Analysis of a "movement epilepsy" bearing a rolandic focus in a monkey]

Several observations in Man as well as in animals have stressed the importance of specific afferents in triggering some focal cortical fits. The authors report an analysis of the role of various afferents on the activity of a precentral focus in the monkey. The chronic focus was created on one adult female monkey by subpial injection of alumina cream in the motor area of the left foot. Typical seizures were clonic and local. The most striking feature was that movement or, more generally, proprioceptive afferents from the concerned leg could elicit and maintain these motor fits. This assumption was verified by curaryzing the animal with succinyl-choline. In this condition, the number of attacks was strongly reduced. Since there was no lowering of excitability at the central level, as shown by direct stimulation of the perifocal area, this decrease seems to result from the lack of triggering mechanisms. If this is the case, one should be able to elicit seizures by proprioceptive afferent volleys coming from the concerned leg. In fact, although passive motion was not very effective (the reason probably being the decrease of the back-ground activity of stretch receptors under curare), direct electrical intramuscular stimulation was always followed by an attack. Similar stimulation of the opposite leg was ineffective. These results are discussed. The role of the "motor cortex proprioceptive feedback" in jacksonian progression of motor seizures is debated. The same concept is applied to "startle epilepsy", for which a physiological hypothesis is purposed.