42 Paul Fourman and Patricia M. Leeson 



insipidus the plasma [Na] is not usually very much raised ; in 

 a patient of ours, a man of 28 with sarcoidosis, the plasma 

 [Na] was at times as high as 149 m-equiv./L, but he was then 

 very thirsty, and he would not tolerate the [Na] rising any 

 higher. On the other hand, patients who are apathetic, weak, 

 disorientated or unconscious may be unaware of thirst, or 

 unable to respond to it. In these patients even normal losses 

 of water may lead to water deficiency with hypernatraemia. 

 It is not unusual to have elderly patients with cerebro- 

 vascular disease who tolerate a plasma [Na] of 150 m-equiv./l. 

 without any complaint of thirst. But when they are given 

 water they retain it, and their clinical and biochemical 

 responses show they had a need for it. We do not know the 

 possible sites of the lesions which may interfere with the 

 sensation of thirst in these people. There is, however, some 

 evidence that in man (Leaf and Mamby, 1952; Engstrom and 

 Liebman, 1953), as in the rat (Stevenson, Welt and Orloff, 

 1950) and the goat (Andersson, 1957), neurological lesions 

 may interfere with the normal sensation of thirst. 



We have had the opportunity of studying a boy of ten who 

 had had a large suprasellar craniopharyngioma removed by 

 Mr. C. Langmaid. There was no evidence of diabetes insipidus 

 before the operation. After the operation, however, while he 

 was in a stuporous state, his plasma [Na] ranged between 

 152 and 163 m-equiv./l. It remained high even when he 

 recovered, and was up and about, and receiving pitressin. 

 The boy did not complain of thirst and we think the lack of 

 thirst led to water deficiency and hypernatraemia. These are 

 some of the values before and after he received pitressin : — 



Date Plasma sodium Urine vol : ml. Specific 



m-equiv.jl. per 24 hours. gravity 



Before pitressin 7 Nov. 161 1370 



After pitressin 21 Nov. 156 860 



25 Nov. 156 1420 1-008 



The urine volume and specific gravity while he was having 

 pitressin suggest the treatment was inadequate, but he did 



