Electroencephalography (EEG) records of consecutive 275 children (ages 3-18 years; average 11 years; 34.5% females), with generalized epilepsy, consistent with epileptiform discharges in baseline EEG, who underwent 5 minutes of voluntary hyperventilation during standard EEG recordings were reviewed in this study to determine the actual value of the voluntary hyperventilation in routine clinical EEG in provoking epileptiform EEG abnormalities. Of the 275 EEG records, only in 11.6% hyperventilation revealed increased interictal epileptiform discharges as evidenced by increase in frequency during hyperventilation when compared with the baseline EEG and in 0.7% ictal epileptiform discharges without clinical seizure. None of the 275 children elicited clinical seizure during hyperventilation. The value of voluntary hyperventilation as an ''activating'' procedure in routine clinical EEG studies even in children with generalized epilepsy was questioned in this study.

This meta-analysis aimed to advance our knowledge about dacrystic epilepsy in children in the present time. PubMed searches for peer-reviewed case reports and case series were conducted using the keywords “dacrystic epilepsy”, “dacrystic seizures”, “crying epilepsy”, “ictal crying”, “crying seizures”. The databases were developed in accordance with preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. The author collected relevant information to characterise the study population including clinical outcome. Eleven studies out of 353 citations between 1998 and 26 May 2021 met the inclusion criteria, including both single cases and series pertaining to dacrystic epilepsy. Eight case reports and three case series were eligible for this meta-analysis and included twenty one cases. The seizure patterns were dacrystic seizures alone in seven cases (33%), and a combination of dacrystic seizures and gelastic seizures in fourteen cases (67%). Neuroimaging revealed structural abnormality in 95% cases. Hypothalamic hamartoma was found in most of the cases (79%) with combined dacrystic seizures and gelastic seizures, whereas it was found in one case (16%) with dacrystic seizures alone. The other underlying lesions in children with dacrystic seizures alone were subependymal nodules and cortical hamartomas (17%), left mesial temporal sclerosis (33%), and cortical dysplasia (17%). Regarding outcome, antiepileptic drugs alone achieved seizure freedom in four cases (22%) only and others (78%) were difficult to treat cases excluding three cases where treatments were not mentioned. Six cases underwent surgical intervention and two cases received ablative radiotherapy. Lesional dacrystic epilepsy is predominant and pharmaco-resistant in children. However, antiepileptic drugs lead to achieving seizure remission in few cases.

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