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HANDBOOK OF PHYSIOLOGY ^^ NEUROPHYSIOLOGY I 



and slowing; progressively, which constitute a ' partial 

 seizure discharge expressed focally'. 



It is evident that such a focus or discharge does not 

 guarantee that the epileptogenic lesion is cortical, for 

 it may just as well be at the subcortical pole of the 

 system and nevertheless be expressed in the cerebral 

 cortex. The clinical manifestations of the seizures de- 

 pend upon the corticothalamic sector involved, ap- 

 pearing as clonic jerks when the sector of precentral 

 cortex :^ ventrolateral nucleus is involved; dysesthesia 

 for the sector of postcentral cortex ^ nucleus ven- 

 tralis posterolateralis; visual phenomena for the 

 striate region ^ lateral geniculate; and auditory 

 phenomena for the superior temporal ;=i medial 

 geniculate. '^ 



The discharges are not necessarily generalized 

 throughout the whole of the corticothalamic sector. 

 Some part only may be involved, for example, the 

 Jacksonian twitching may affect only the face. Simi- 

 larly, several adjacent sectors may be involved con- 

 comitantly or successively; for example, the Jack- 

 sonian jerking may accompany or be followed by 

 dysesthesia in the corresponding part of the body. 



i) In the second variety of partial epilepsy, the 

 causal discharge originates in a nervous structure 

 which is more or less diffusely connected with several 

 other cerebral regions, constituting a multiple relay 

 system. These systems are too numerous and at 

 present too ill-defined to be described fully. In addi- 

 tion they are interconnected and a given cerebral 

 structure may belong to several of them. We can how- 

 ever distinguish two great rhinencephalic systems: 

 the hippocampus connected on the one hand to the 

 limbic lobe and on the other hand to the hypothala- 

 mus and tegmentum; and the basal rhinencephalic 

 formations (piriformoamygdaloid and olfactoseptal) 

 connected on the one hand to the orbitoinsulotele- 

 temporal cortex, and on the other to the epithalamus, 

 hypothalamus and tegmentum mesencephali. There 

 is also the most rostral part of the reticular formation 

 of the brain stem which projects diffusely from the 

 thalamus on to the whole of the cerebral cortex and 

 which was previously discussed. This last system may 

 be activated globally by way of the reticular afferents, 

 as in generalized epilepsy, but it may often be 

 brought into play in a fragmentary way in the partial 

 epilepsies.'* 



" These seizures most commonly de\ elop in the precentral 

 cortex ;=i n. ventrolateral nucleus sector, not because it more 

 often contains the epileptogenic lesion but because it has the low- 

 est convulsant threshold. 



" These diffuse systems are often activated in the partial 



The clinical manifestations are complex because 

 they involve simultaneously or successively a large 

 number of structures with different functions. Sen- 

 sory, mental or motor symptoms may be associated 

 or succeed each other and Gowers (92) has described 

 cases in which a dozen visual, auditory, olfactory, il- 

 lusional, hallucinatory and motor symptoms follow 

 each other without interruption. 



Vegetative and affective manifestations are particu- 

 larly important since the discharges usually involve 

 the rhinencephalon and diencephalon. These fre- 

 quently include abnormal epigastric, abdominal and 

 precordial sensations with reactional gestures: chew- 

 ing, salivation, deglutition, and imperious needs to 

 eat, urinate or defecate, as well as disorders of atten- 

 tion, anxiety, fear, anger, etc. 



There usually is clouded consciousness and the ap- 

 pearance of more or less complex automatisms, since 

 these discharges disturb the functioning of a large 

 part of the brain and usually involve some of the 

 diffuse cortical projection system which helps to regu- 

 late cerebral excitability and consciousness. 



The electroencephalographic manifestations take 

 the form of seizure discharges which may be classified 

 as follows a) Localized discharges appearing as spike 

 rhythms in the temporal region (with anterior tem- 

 poral and middle temporal electrodes) or in the occip- 

 ital region (with occipital, posterior temporal and 

 posterior parietal electrodes), according to whether 

 the discharge develops in the amygdalotemporal 

 system or the pulvinaro-occipitoparietotemporal 

 sector. 



These localized seizure discharges are usually situ- 

 ated on the same side as the interseizure focus and its 

 causal lesions, but fairly frequently they are situated 

 on the opposite side (82). Such independent contra- 

 lateral discharges may indicate a secondary vascular 

 extension of the lesion to the other side (6g) but may 

 also indicate a functional ' vmleashing' of these homolo- 

 gous contralateral structures which have acquired 

 epileptogenic potentialitv through being bombarded 



(78). 



fe) Diffuse discharges, constituted by a rhythm of 

 waves gradually slowing or accelerating, more or less 

 generalized over one or both hemispheres but often 



epilepsies through the rhinencephalic formations for two reasons: 

 a) the latter, chiefly the hippocampus and amygdala, aie 

 frequently the seat of epileptogenic lesions (pararhinal sclerosis 

 in the so-called temporal' epilepsies); and 6) these rhinenceph- 

 alic formations have the lowest convulsant threshold of all 

 cerebral structures Csee above). 



