Epilepsy and EEG Patterns in Children Diagnosed with Hyperinsulinism. Report of Two Cases Presented as Atypical Generalized Epilepsy and Review of EEGS of 15 Supplementary Cases.

Purpose: Hyperinsulinism is a rare genetic disorder with a heterogeneous presentation. Its severity ranges from severe, life-threatening hypoglycemia in newborns to mildly symptomatic hypoglycemia beginning in childhood, adolescence, or adulthood. Hypoglycemic loss of consciousness and seizures are the most common presentations. Electroencephalography (EEG) patterns are not well known, and patients may be erroneously diagnosed with epilepsy. We tried to better characterize EEG datas in a cohort of patients with hyperinsulinism.

Methodos: Two cases of hyperinsulinism were diagnosed after an initial follow-up for epilepsy in our department. We then identified all patients followed for hyperinsulinism in the endocrinology department since 2000 and their respective EEGs were reviewed.

Results: The two index cases are those of an 8-month-old infant and a 14-year-old adolescent. Their EEGs were reviewed including an episode of hypoglycemia verified for each one of them (without epileptic seizure on the EEG). We found an inconstant slowing, focal, or diffuse, with very slow notched waves or spikes or polyspikes, isolated, or in bursts. During hypoglycemia, we found an accentuation of these slow notched waves, with an EEG-tracing, with progressively increasing amplitude and delta frequencies. In the second patient, a glucose infusion under EEG recording resulted in an immediate disappearance of the pathological pattern. The interictal pattern in both patients was consistent with generalized yet atypical epilepsy. Another 15 hyperinsulinic patients were identified and 12 of them had an EEG. These EEGs were normal in six patients. Five patients had focal abnormalities and one patient had a temporo occipital slowing.

Conclusion: Our two patients had no revelation of their hyperinsulinism by clinical suspicion of hypoglycemia but presented themselves as having epilepsy. Interestingly, although their initial EEG-tracings revealed epileptic abnormalities, these were different from those seen during their proven hypoglycemic episodes. This could lead to the hypothesis of an altered cerebral activity with further epileptogenesis resulting from untreated repeated hypoglycemia.

No conflict of interest has been declared by the author(s).