A case of hyperventilation-induced high-amplitude rhythmic slowing with altered awareness requiring differentiation from typical absence seizure

DOI
  • Noda Marie
    Section of Pediatrics, Department of Medicine, Fukuoka Dental College, Fukuoka
  • Ichimiya Yuko
    Section of Pediatrics, Department of Medicine, Fukuoka Dental College, Fukuoka Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka
  • Okuzono Sayaka
    Section of Pediatrics, Department of Medicine, Fukuoka Dental College, Fukuoka Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka
  • Sakai Yasunari
    Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka
  • Torisu Hiroyuki
    Section of Pediatrics, Department of Medicine, Fukuoka Dental College, Fukuoka

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Other Title
  • 一過性の意識減損を呈し定型欠神発作と鑑別を要したhyperventilation-induced high-amplitude rhythmic slowing with altered awareness（HIHARSAA）の1例

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<p>  Hyperventilation-induced high-amplitude rhythmic slowing with altered awareness (HIHARSAA) is an age-dependent nonepileptic physiological phenomenon induced by hyperventilation, in which rhythmic high-amplitude slow-wave activity appears on electroencephalogram (EEG) and transiently alters the consciousness. Here, we report the case of a 4-year-old girl who was diagnosed with HIHARSAA by EEG video recording. She showed transient loss of consciousness during hyperventilation followed by crying and was subsequently admitted to our hospital for detailed examination. She was alert and had no neurological abnormalities. Head MRI and MRA showed no significant abnormal findings such as stenosis of the main cerebral arteries. Electroencephalography showed no abnormalities during the interictal period. During hyperventilation, a sudden occurrence of rhythmic high-amplitude 3-3.5 Hz slow-wave activity was observed on EEG, and she became dazed, started to mumble, moved her hands, and began to fidget, consistent with the appearance of EEG abnormalities. Although it was difficult to differentiate the seizures from typical absence seizures, the patient was diagnosed with HIHARSAA because the ictal EEG was a rhythmic high-amplitude slow wave without spikes. Hence, she was followed up without medication. Although HIHARSAA is a rare phenomenon, it should be differentiated from typical absence seizure by means of EEG video recording.</p>

Journal

  • NO TO HATTATSU

    NO TO HATTATSU 57 (1), 45-48, 2025

    The Japanese Society of Child Neurology

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