THE PHYSIOPATHOLOGY OF EPILEPTIC SEIZURES 



331 



ELECTROENCEPHALOGRAPHic ASPECTS. Partial epileptic 

 seizures differ from generalized seizures in that their 

 discharges can be recorded from a part of the scalp 

 only, and they show a great diversity of expression. 

 Without attempting to give a full description, we may 

 divide them into two main topographical groups: 

 a) localized partial discharges, consisting of rhsthmic 

 spikes, occasionally from the frontal or central regions, 

 but much more frequently from the temporal or 

 parieto-occipital regions and b) diffuse partial dis- 

 charges, showing as desynchronization or slow hyper- 

 synchronization and arising from all or a part of one 

 or both hemispheres (usually the temporofrontal 

 regions). 



In addition there are numerous cases in which 

 localized and diffu.se discharges both appear during 

 the same seizure with a variety of temporospatial 

 relations. The discharges appear either independently 

 or concomitantly, and either in or out of phase; 

 they usually involve the anterior temporal and frontal 

 or the posterior temporal and parieto-occipital re- 

 gions. 



It is of course well recognized that any partial 

 seizure may become generalized and then present 

 the electrical and clinical characteristics of a grand 

 mal fit, whether or not it is preceded by myoclonic 

 jerks. One must therefore carefully distinguish be- 

 tween fits which are generalized from the start and 

 those which become generalized after a partial 

 onset. 



ETIOLOGY 



It is generally recognized that epileptic seizures 

 may be divided into two main categories, according 

 to whether or not there is a demonstrable brain lesion. 

 One category comprises the so-called secondary or 

 symptomatic epilepsies arising from a lesion which is 

 infective, degenerative, traumatic, neoplastic or 

 vascular; these constitute a well-recognized and un- 

 disputed entity. The etiology in the other category has 

 always been controversial; some authors regard the.se 

 epileptic fits as the result of brain lesions which are 

 undemonstrable and consider that they should be 

 called collectively cryptogenic epilepsy; others believe 

 that they represent disordered metabolism or a fault 

 in cerebral function, unassociated with any organic 

 abnormality. They should therefore be qualified as 

 "functional', 'metabolic' or 'primitive' as opposed to 

 those that are 'organic' or 'secondary'. This termi- 



nology unfortunateh- has not been adhered to, and it 

 has become customary to call functional epilepsies 

 either 'idiopathic' or 'essential'. This has given rise 

 to a discussion the etymological origin of which has 

 gone unrecognized but which has caused divergence 

 of opinion which was more apparent than real. How- 

 ever this may ije, the existence of two types of epilepsy 

 is now accepted. 



Functiomd Epilepsy 



This disorder is encountered in only 5 per cent of 

 all cases, according to Bicard et al. (17). It is also 

 known as primitive, essential, genuine, idiopathic, 

 metabolic, genetic, etc. It results from a fault in the 

 functioning of the brain manifested b\- an epileptic 

 'predisposition', fairly often hereditary. It is not asso- 

 ciated with any anatomically detectable lesion of the 

 brain and it is not accompanied by any interictal 

 neurological or psychiatric manifestations; and it is 

 always manifested by seizures (grand mal or petit 

 mal) which are generalized from the start of the 

 attack. 



Organic Epilepsy 



This type is very common (95 per cent of all 

 cases). It is also known as symptomatic or secondary. 

 It is caused by an anatomically recognizable cerebral 

 lesion and for this reason it may be associated with 

 neurological or psychiatric abnonnalities between 

 fits; it may develop on a 'soil' already predisposed to 

 convulsions and thus a mildly irritative lesion inay be 

 markedly epileptogenic; and only rarely is it mani- 

 fested as a primarily generalized seizure, rather usu- 

 ally appearing as partial epilepsy which may or may 

 not become secondarily generalized. 



PHYSIOPATHOLOGY OF SEIZURES 

 GENER.-VLIZED FROM START 



This presentation will be divided into two parts. 

 The first will be an impartial review with some de- 

 .scription of the experimental results accumulated over 

 nearly two centuries of effort to explain the mecha- 

 nism of generalized seizures, particularly those of grand 

 mal. The second will furnish a personal interpretation 

 of these experimental results, based on modern neuro- 

 physiological data. 



