The pediatric MS incidence in Sardinia is estimated to be significantly higher than those reported elsewhere. The pediatric MS prevalence in Sardinia is among the highest values worldwide.

Highlights We show that typical absence seizures (AS) and hyperventilation-induced high amplitude rhythmic slowing (HIHARS) or HIHARS with Altered Awareness (HIHARSAA) can coexist in the same patient, but never at the same time. We found that alkalosis and dysfunction of the same neural network are involved in both AS and HIHARS. AS and HIHARS should be better recognized to avoid misdiagnosis and overtreatment. AS and HIHARS can coexist in the same patient, but never at the same time.