THE PHYSIOPATHOLOGY OF EPILEPTIC SEIZURES 



359 



predominant in the frontotemporal region. This oc- 

 curs when the discharges develop in the diffuse 

 thalamocortical system. 



f) Complex discharges, in which localized and 

 diffuse discharges are associated, either independently 

 or concomitantly, and if the latter, either in or out of 

 phase. This occurs when various cortical-subcortical 

 systems are brought into play simultaneously or suc- 

 cessively causing " erratic' discharges. 



cf) Localized or generalized flattening of the basic 

 rhythm occurs when the structure involved in the 

 seizure is endowed with the property of desyn- 

 chronizing the cortical electrical activity. 



e) There may be no EEG manifestation of a seizure 

 at all when the discharge invokes subcortical struc- 

 tures with very poor cortical projection or when it is 

 unable to cross the synapses leading to the cortex. 



The interseizure discharges may be more or less 

 diffuse for the same reason as the seizure discharges, 

 but they are most often localized to the temporal 

 region (and particularly the anterior temporal) or one 

 or both hemispheres. This particular site is the most 

 common, as Gibbs has well shown, because these in- 

 terictal discharges usually originate in the diseased 

 cerebral structures with the lowest convulsant thresh- 

 old, that is to say, the tip of the temporal lobe and the 

 basal rhinencephalic formations (piriform cortex, 

 amygdala and hippocampus) which also project on 

 to the teletemporal region (72, 121; and later authors). 



Having described these two great varieties of partial 

 epilepsy on the basis of pathological physiology, we 

 shall further describe them in terms of anatomy, 

 etiology, symptomatology and therapy. 



a) The localized partial epilepsies not only show a 

 local discharge but are usually caused by a localized 

 superficial lesion, either atrophic or neoplastic. The 

 causes are not numerous and include open head in- 

 juries with well-defined craniocerebral wounds, lo- 

 calized infections, chiefly periarterial or perivenous, 

 local vascular accidents (malformations or throm- 

 bcses) and small cortical or paracortical tumors. These 

 lesions are discrete and, because they interfere with 

 the normal functioning of only a small amount of 

 cerebral parenchyma, the patient's mental make-up 

 is usually normal between seizures, especially from 

 the intellectual point of view. The lesion is usually 

 cortical for the superficial pole of the corticothalamic 

 sector is a much larger area and is more vulnerable 

 than is its deep pole. Since the lesion involves the 

 convexity of the cortex and spares the rhinencephalon 

 and diencephalon, there is usually no disturbance of 



character or behavior between seizures. On the other 

 hand, interictal neurological symptoms are relatively 

 frequent (mild hemiplegia, dysphasia or hemianop- 

 sia) for the lesion involves a corticothalamic sector 

 with specific functions. Surgery may often be indicated 

 when medical treatment fails in this type of partial 

 epilepsy because of the precise and superficial locali- 

 zation of the lesion and because of its small size. The 

 operation usually is easily performed and yields excel- 

 lent results. 



6) The diffuse partial epilepsies not only have a 

 diffuse discharge but arise from diffuse sclerosis, pre- 

 dominating in the inferomedial aspect of the hemi- 

 sphere, the 'pararhinal' region. The causes are 

 numerous and varied ijut may be divided into three 

 main groups, depending on the age at which the 

 lesion is acquired: severe and prolonged compression 

 of the head during delivery (156); cerebral edema in 

 infancy or early childhood which accompanies various 

 disorders clinically misnamed 'encephalitis', consist- 

 ing of status epilepticus with coma and subsequent 

 transient hemiplegia (57, 58); and closed head in- 

 juries in the adult (64). The principal pathogenic 

 mechanisms in these three conditions are wedging of 

 the hippocampal gyrus and the blood vessels supply- 

 ing it into the tentorial incisure during compression of 

 the brain at birth, or during intracranial hypertension 

 secondary to cerebral edema in childhood, and in- 

 jury of the orbitoinsulotemporal region by the sharp 

 edge of the lesser wing of the sphenoid from the contre- 

 coup accompanying closed head injuries. These two 

 mechanisms are responsible for the two aspects of 

 pararhinal sclerosis, incisural sclerosis (156), and 

 vallecular (perifalciform) sclerosis (53, 57) which 

 develops in relation to the tentorial incisure and 

 around the vallecula sylvii in the region correspond- 

 ing to the pararhinal region. 



Because the lesions responsible for psychomotor 

 epilepsy are so widespread and so severe and are lo- 

 cated in the pararhinal region, these patients fre- 

 quently show interseizin-e disturbances of intellect 

 and particularly of character and of sexual, alimen- 

 tary and social behavior (62).'-^ 



On the other hand, these diffuse and deep lesions 

 do not involve the majority of the corticothalamic 

 sectors and the important projection pathways which 

 explains the fact that interseizure neurological mani- 



'° The basal part of the rhinencephalon acts as a controlling 

 and regulating system of complex automatic activities, princi- 

 pally those adapted to the seeking of the opposite sex and 

 to the pursuit, intake and ingestion of food (56). See the chap- 

 ters in this work dealing with this region. 



