Occurrence of hyperventilation-induced high amplitude rhythmic slowing with altered awareness after successful treatment of typical absence seizures and a network hypothesis

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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.

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We found that alkalosis and dysfunction of the same neural network are involved in both AS and HIHARS.

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AS and HIHARS should be better recognized to avoid misdiagnosis and overtreatment.

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AS and HIHARS can coexist in the same patient, but never at the same time.

Background

Typical absence seizures (AS) are epileptic phenomena typically appearing in children 4–15 years of age and can be elicited by hyperventilation (HV). Hyperventilation-induced high-amplitude rhythmic slowing (HIHARS) represents a paraphysiological response during HV and may manifest with alteration of awareness (HIHARSAA). To date, HIHARSAA has mostly been described in patients without epilepsy.

Aim

To describe five patients with treatment-responsive typical AS who, after becoming seizure free, presented with HIHARSAA.

Methods

By using video-electroencephalographic recording (Video-EEG), we describe differential clinical characteristics and ictal electrophysiological patterns of both typical AS and HIHARSAA.

Results

We demonstrate that when HIHARSAA occurs in patients with typical AS there is a temporal window between the two phenomena. This suggests that the presence of typical AS precludes the appearance of HIHARSAA.

Conclusions

We hypothesize that alkalosis and dysfunction of the same neural network are involved in both typical AS and HIHARSAA and that their distinct electroclinic manifestations are due to the involvement of different ion channels.

Significance

A better understanding of the characteristics of typical AS and HIHARSAA and of the role of alkalosis in both, can help avoiding misdiagnosis and identifying more suitable therapies for typical AS.

CACNA1A-Linked Hemiplegic Migraine in GLUT 1 Deficiency Syndrome: A Case Report

Background: Glucose-transporter-1 deficiency syndrome (GLUT1-DS), due to SLC2A1 gene mutation, is characterized by early-onset seizures, which are often drug-resistant, developmental delay, and hypotonia. Hemiplegic migraine (HM) is a rare form of migraine, defined by headache associated with transient hemiplegia, and can be caused by mutations in either CACNA1A, ATP1A2, or SCN1A. Paroxysmal movements, other transient neurological disorders, or hemiplegic events can occur in GLUT1-DS patients with a mild phenotype.

Case: We report on a girl with GLUT1-DS, due to SLC2A1 mutation, with a mild phenotype. In early childhood, she developed epilepsy and mild cognitive impairment, balance disorders, and clumsiness. At the age of 9, the patient reported a first hemiplegic episode, which regressed spontaneously. Over the next 3 years, two similar episodes occurred, accompanied by headache. Therefore, in the hypothesis of HM, genetic testing was performed and CACNA1A mutation was identified. The treatment with Lamotrigine avoided the recurrence of HM episodes.

Discussion: To our knowledge, among the several cases of GLUT1-DS with HM symptoms described in the literature, genetic testing was only performed in two of them, which eventually proved to be negative. In all other cases, no other genes except for SLC2A1 were examined. Consequently, our patient would be the first description of GLUT1-DS with HM due to CACNA1A mutation. We would emphasize the importance of performing specific genetic testing in patients with GLUT1-DS with symptoms evocative of HM, which may allow clinicians to use specific pharmacotherapy.