EEG abnormalities with and without relation to severe hypoglycaemia in adolescents with type 1 diabetes

Aims/hypothesis: The aim of the present study was to identify whether adolescents with type 1 diabetes receiving modern multiple insulin injection therapy (MIT) have abnormal EEGs, and to elucidate possible correlations with a history of severe hypoglycaemia, poor metabolic control and nerve conduction defects. Methods: We investigated 35 patients (age 14-19 years) with disease duration 7.6 +/- 4.6 years, and 45 healthy control subjects. EEG spectral components were obtained from 15-min recordings in resting, awake subjects. Nerve conduction was measured bilaterally in motor and sensory fibres in the median, peroneal and sural nerves. Results: The EEGs of patients showed an increase in slow activity (delta and theta) and a reduction in alpha peak frequency, both of which were most pronounced in the frontal regions (p < 0.001). They also showed a decrease in fast activity, which was most pronounced bilaterally in the posterior temporal regions (alpha p < 0.001, beta p < 0.01, gamma p < 0.001). A history of severe hypoglycaemia was correlated with a global increase in theta activity (p < 0.01-0.05). Poor metabolic control, measured as acute and long-term HbA(1)c levels, was correlated with an increase in delta activity and a decrease in alpha peak frequency. The decrease in fast activity in the temporal regions was a separate type of abnormality because it had a different distribution, and was not correlated with the increase in delta/theta power, poor metabolic control or with hypoglycaemia. Conclusions/interpreation: Recurrent severe hypoglycaemia and poor metabolic control are risk factors for EEG abnormalities in adolescents with type 1 diabetes receiving MIT treatment. In addition, we found pronounced abnormalities in the temporal regions that were not related to these risk factors.