Decrease of vigilance assessed by EEG-mapping in Type I diabetic patients with history of recurrent severe hypoglycaemia

In Type I diabetic patients with history of recurrent severe hypoglycaemia, a more rapid decrease in vigilance (slowing of brain function) during hypo glycaemia in comparison to patients without history of such events was foun d. Our aims were: (1) to study EEG parameters of vigilance in non-hypoglyca emic state in representative groups of Type I diabetic patients with and wi thout previous recurrent severe hypoglycaemia; and (2) to compare them with non-diabetic controls. A vigilance-controlled EEG mapping (10-20 system, s ignificance probability maps) was performed in a non-hypoglycaemic state (b lood glucose 4.0-10.0 mmol/l) in a group of 13 Type I diabetic patients wit h a history of recurrent severe hypoglycaemia and compared to that of 14 Ty pe I diabetic patients without history of severe hypoglycaemia, matched for HbA(1c), age and gender, and to age- and gender-matched non-diabetic contr ols. When compared to non-diabetic controls, hypoglycaemia patients demonst rated a reduction in absolute power in beta band (13-35 Hz) and slowing of centroid frequencies of beta and total frequency bands (1.3-35 Hz) (up to P < 0.01). whereas patients without history of severe hypoglycaemia showed o nly a borderline reduction of absolute power in delta (1.3-3.5 Hz) band. De celeration in hypoglycaemia patients versus those without recurrent hypogly caemia was most remarkable (P < .01) in centroid frequency of total frequen cy band. Patients with history of recurrent severe hyperglycaemia demonstra ted in non-hypoglycaemic state significantly reduced vigilance when compare d to the group without hypoglycaemia history and to the controls, its well. Lower vigilance may be at least in part responsible for impaired hypoglyca emia perception in these patients, but, as it resembles EEG patterns seen i n pathologic ageing, it might also represent a consequence of recurrent epi sodes of severe hypoglycaemia. (C) 1999 Elsevier Science Ltd. All rights re served.