Shortly after his discovery of insulin, Banting and his collaborators observed that in diabetics given insulin the clinical symptoms of an insulin reaction may occur without depression of the blood sugar to a subnormal level (1-3). Subsequently others found that the symptoms of an insulin reaction may develop even with a high blood sugar level (4, 5).In the past twenty years we and others have noted that many patients with labile diabetes who are subject to episodes that clinically resemble hypoglycemic reactions, exhibit abnormalities in the electroactivity of the brain. Moreover, these reactions are not associated with hypoglycemia, and fail to respond to carbohydrate administration though they may be prevented or minimized by anticonvulsive therapy (6-10). For these reasons we have proposed the term "pseudohypoglycemic reaction" to designate the clinical symptoms that resemble those of an insulin reaction (in both labile and stable diabetes) but develop in the absence of a critically low blood sugar level (6-8). The occurrence of pseudohypoglycemic reactions was later reported in association with : (a) clinical disorders which can interfere with the normal function of the central nervous system, e.g., cerebral arteriosclerosis, and (b) clinical disorders accompanied by symptoms simiiar to those of hypoglycemia, e.g., the hypocalcemia of hypoparathyroidism (6,(11)(12)(13)(14)(15)(16).It is the purpose of this paper to stress the value of electroencephalographic studies in patients with pseudohypoglycemic reactions and unpredictable insulin reactions, and the importance of differential diagnosis.
CLINICAL MATERIAL AND METHODSThe study was carried out on 122 patients with labile diabetes and 89 patients with stable diabetes, all 211 of whom were subject to frequent or unpredictable insulinreactions.Electroencephalographic records were obtained routinely in all cases. To avoid the effect of subnormal blood glucose levels, the EEG tracings were taken one or two hours after a normal meal. Both a resting record and a record after two minutes of hyperventilation were obtained. The electroencephalograms were repeated in most patients within six months to four years.Since many of the manifestations of parathyroid insufficiency and hypocalcemia may mimic those of hypoglycemia (14), serum calcium determinations were made routinely