Plasma glucose alone does not predict neurologic dysfunction in hypoglycemic nondiabetic subjects

Study objective: To assess the value of plasma glucose concentration alone as a predictor of neurologic dysfunction in nondiabetic subjects with norma l baseline neurologic examination and electroencephalographic (EEG) finding s. Methods: Neurologic function and EEG results were evaluated in 17 subjects before and during insulin-induced hypoglycemia using relevant and reliable clinical tools for bedside use. Results: Hypoglycemia (mean nadir concentration, 30 mg/dl) was without effe ct on level of consciousness or cranial nerve, motor, sensory, vestibulocer ebellar, language, or simple visuospatial functions. Attention was minimall y impaired in all subjects, but memory in only 3. EEG results remained norm al in 5 subjects; minimal to moderate nonspecific changes occurred in the r est. All patients manifested signs of sympathetic stimulation from hypoglyc emia, including tremor, tachycardia, and diaphoresis. The manifestations of neuroglycopenia did not correlate significantly with nadir plasma glucose or duration of hypoglycemia. Conclusion: Moderately severe hypoglycemia of short duration can be neurolo gically occult, or subtle inattention can be its first and only clinical ma nifestation. Our findings are at variance with reports in the emergency med icine literature in which marked deficits are universally present at glucos e concentrations equal to those attained in this study. This discrepancy su ggests that the expression of neuroglycopenia is multifactorially determine d and that plasma glucose concentration alone does not predict neurologic d ysfunction in nondiabetic subjects with normal baseline neurologic examinat ions.