Search

Summary 1 In eight patients with petit mal EEGs (approximately thirty) were taken. During the seizure patterns various external stimuli were applied. In these cases clinical and electroencc-phalographic changes were observed simultaneously and relationships between the two were studied. 2 In petit mal attacks there are various degrees of alteration of consciousness grading from almost no loss of consciousness to complete lapse of consciousness. Between subclinical and clinical seizures there is a transition, and it is difficult to determine a definite border line between the two. 3 liven in a single petit mal seizure the degree of disturbance of consciousness is not constant but is altered in various ways spontaneously or following various stimuli. This can be confirmed by applying various stimuli during die seizure. 4 There are often no changes in the seizure waves in spite of changes of consciousness during a petit mal seizure. Even though various responses are elicited by stimuli the petit mal waves sometimes continue unchanged. Therefore even though petit mal waves usually do show the presence of disturbance of consciousness, they do not always indicate the degree of alteration of consciousness during the seizure.

SUMMARY 1. (a) Metrazol or strychnine intracarotid injections, (b) strychnine topical application to the motor cortex, (c) metrazol injection into the motor cortex and (d) electrical stimulation of the motor cortex and of the diffuse thalamic projection system were used in sixty-five anesthetized cats. After observing the patterns of abnormal electrical activity, spasms and convulsions, the animals were decapitated at various stages. The distribution of the blood within the brain at the time of decapitation was examined with the benzidine method and the findings compared with the observations mentioned above. 2. Spikes and at times local spasms were seen before clear-cut circulatory disturbance of the brain appeared, in all methods of stimulation from (a) to (c). This shows that vasospasm of the brain does not necessarily precede the appearance of convulsions. 3. Clear circulatory disturbance may be seen when the spikes have spread to the deeper regions of the brain. Furthermore, even though the appearance of the spikes or muscle spasms is one-sided, the circulatory abnormality is often seen on both sides. This fact suggests the influence of the subcortical vasomotor center on the occurrence of wide-spread vasospasm. 4. When general convulsions occurred, definite circulatory abnormalities were seen in wide-spread regions of the brain in most of the cases studied. However, regardless of the occurrence of an almost generalized convulsion as far as the electrical activity and the behavior of the animal are concerned, there were a few cases which showed very little change in circulatory condition. This was especially noticeable when metrazol was injected in or electrical stimulus was applied to the motor cortex. 5. In animals decapitated during the appearance of 3 c/s spikes-and-waves or similar patterns waves after electrical stimulation of the diffuse thalamic projection system, clearly defined circulatory disturbances were not seen. RESUME 1. (a) Injections intracarotidiennes de metrazol ou de strychnine; (b) application locale de strychnine sur le cortex moteur, (c) injection de metrazol dans le cortex moteur et (d) excitation electrique du cortex moteur et des projections thalamiques diffuses chez soixante-cinq chats sous narcose. Apres observation des traces de l'activiteelectrique anormale, des spasmes et des convulsions, les animaux furent decapites a differents stades. La distribution du sang dans le cerveau au moment de la decapitation fut etudiee par la methode basee sur l'emploi de la benzidine et les constatations faites a cette occasion furent comparees avec les observations mentionnees ci-dessus. 2. Des pointes et parfois meme des spasmes ont ete observes avant que n'apparaissent des troubles circulatoires bien definis du cerveau avec les trois methodes d'excitation citees sous (a), (b) et (c). Ceci montre que le spasme vasculaire du cerveau ne precede pas necessairement l'apparition des convulsions. 3. Des perturbations circulatoires nettes peuvent etre observees lorsque les pointes se sont etendues aux regions plus profondes du cerveau. De plus, meme lorsque les pointes ou les spasmes musculaires ne se manifestent que d'un cote, la perturbation circulatoire est souvent bilaterale. Cette observation indique que le centre vasomoteur sous-cortical parait avoir une influence sur l'apparition des spasmes vasculaires etendus. 4. Dans les cas ou des convulsions generalisees se sont produites, des perturbations circulatoires nettes ont ete observees dans des regions etendues du cerveau pour la plupart des cas etudies. Toutefois, independamment de l'apparition d'une convulsion quasi generalisee en ce qui concerne l'activiteelectrique et le comportement de l'animal, il y eut quelques cas dans lesquels l'etat de la circulation ne fut affecte que dans une mesure tres reduite. Ce phenomene fut particulierement observe dans les cas ou l'on eut recours aux injections de metrazol ou aux excitations electriques du cortex moteur. 5. Chez les animaux decapites au moment de l'apparition de pointes-ondes de 3 c/s, apres une excitation electrique des projections thalamiques diffuses, aucune perturbation circulatoire nette n'a ete observee.