Personality changes in temporal lobe epilepsy.

Our topic tonight is the personality changes in temporal lobe epilepsy. This follows naturally from the second lecture in this series on the physiological basis of emotional behavior. The personality alterations in temporal lobe epilepsy are our best illustration of the anatomical and physiological organization of emotion. There are other conditions in which one sees some aspects of change in emotional behavior, but none are very common and none reveal the events contributing to change in emotional behavior as well as temporal lobe epilepsy. In my last lecture we discussed the patient of Plum and Reeves who had a congenital tumor near the ventromedial nuclei of the hypothalamus. This patient had exactly the same syndrome as do animals with destruction of that region. The patient became massively obese and became very aggressive. That isolated case provides only limited insights into mechanisms. There is one disease a cardinal feature of which is change in emotional behavior, and in fact this is a disease whose name obviously means rage in all languages except English. It is a disease which in French is called rage, in German is called tollwut, which means rage, in Italian rabbia, and in English rabies. Rabies also means rage but the derivation is less obvious. The word ‘‘rabid” as applied to dogs describes the very striking change in the dog who becomes an animal who transmits the disease by biting. The effect of the lesion causes the dog to bite more readily, providing the virus a means for transmission to the next host. Oddly, rage behavior as a characteristic of rabies was always well known, but it took a very long time for people to appreciate that the localization of its lesions was giving a message about the localization of rage in the nervous system. Gastaut, the French neurologist interested in temporal lobe epilepsy, pointed out that the lesions in rabies occur in the limbic system in areas similar to the ones that John Flynn reported in simulation-induced rage. Rabies is not a very good disease to study. It is an acute disease. It is invariably fatal and the changes which occur are very rapid and very dramatic. Temporal lobe epilepsy is therefore unique in a very special way. Among all of the psychiatric disorders known to mankind, it is the one cause of serious psychiatric symptoms whose mechanism we understand fairly well. This makes temporal lobe epilepsy a tremendously important disorder, although it remains very widely neglected. If you take the large number of patients in mental hospitals with schizophrenia, you can say that this is an important and common disorder, but nobody to my knowledge knows the cause or mechanism of schizophrenia. Second, there are many organic behavior disorders in which we know the cause but not the mechanism. Consider atropine, an anticholinergic drug that is often used to treat Parkinson’s disease. It can produce a paranoid psychosis that disappears when the drug wears off or can be reversed instantly by giving an anticholinesterase agent such as phyostigimine. This is an empirical fact. But we cannot explain why someone becomes psychotic on atropine. Some people who become hypoglycemic on insulin develop extremely paranoid and curious behavior. This is an empirical fact but we do not understand the inner mechanism. The importance of temporal lobe epilepsy is that the mechanism of the behavior disorder seems more apparent. As a result, as an avenue of study in psychiatry and behavioral disorders, it should be one of the major interests. However, it is not an area of active research. People study disorders of obscure etiology when they have a common disorder of clear etiology that could be studied much more fruitfully. 2