Subcortical arousal response in child patients with obstructive sleep apnea Jun Kohyama * , Takeshi Hasegawa Department of Pediatrics, Tokyo Medical and Dental University, 1-5-45 Yushima, Tokyo 113-8519, Japan Abstract Objective: The objective of this study is to assess subcortical arousal response (SCA) in child patients with obstructive sleep apnea syndrome (OSAS). Methods: A new index termed SCA was defined as a sigh associated with elevated chin muscle activity. According to the duration, SCAs were divided into three types; SCA short (1 s or more and less than 3 s), SCA intermediate (3 s or more and less than 10 s), and SCA long (10 s or more). We scored SCAs in six child OSAS patients, aged 2–5 years, before and after adenotonsillectomy. SCAs were also counted in four age-matched controls. Results: In the pretreatment records, 45.5% of SCAs were associated with electroencephalographic arousals. In all patients, SCA short and SCA intermediate decreased after the treatment to the levels in the controls. SCA long exhibited no consistent changes after treatment. The incidence of SCAs was much higher than arousals previously reported in child OSAS patients as well as in normal children. Conclusions: SCAs, especially SCA short and SCA intermediate, are sensitive and useful indices for assessing subcortical involvement in child OSAS patients. q 2002 Elsevier Science B.V. All rights reserved. Keywords: Sleep disordered breathing; Obstructive sleep apnea; Subcortical arousal response; Children 1. Introduction Arousal from sleep is an important defense mechanism against life-threatening events during sleep. Spontaneous arousals tend to increase with age, and arousal to sensory stimuli occurs less during infancy and childhood [1]. Arou- sals can also occur in response to hypoxia, hypercapnia, and airway occlusion. In adult patients with obstructive sleep apnea syndrome (OSAS), excessive daytime sleepiness and neurobehavioral abnormalities of vigilance and reaction time are considered to be the sequelae of frequent arousals [1]. Even in children, OSAS occurs in about 1–3% [2,3] of the cases. However, according to McNamara et al., arousals in child OSAS patients (mean age; 4.6 years) with electro- encephalographical (EEG) changes were observed only in 39.3% of respiratory events during quiet sleep and 37.8% of events during rapid-eye-movement sleep (REMS) [4]. In other words, more than half of the apneas were not asso- ciated with EEG arousals in OSAS children. This lack of cortical arousal in child OSAS patients may account for the low incidence of excessive daytime sleepiness compared to adults with OSAS [5]. However, children with OSAS are reported to have neurocognitive deficits, such as poor learn- ing, behavioral problems, and attention deficit hyperactivity disorder [6]. Even without EEG arousals, higher brain func- tions are likely to be affected. In child OSAS patients, arousals, demonstrated by move- ment or autonomic changes, occur frequently [6]. Marcus pointed out that the presence of frequent movement arousals in child OSAS patients may play a role in autonomic conse- quences, such as hypertension and heart rate changes [5]. Marcus also stated that subcortical arousals probably occur frequently in child OSAS patients [6]. Subcortical arousals may also contribute to the occurrence of neurobehavioral complications. It is postulated that subtle disturbances in sleep architecture, which cannot be detected on routine polysomnography, are present in child OSAS patients [7]. In the current study, we aimed to introduce a new index that can be detected during routine polysomnography, which can reflect subcortical arousals, and that correlates with the severity of OSAS. In the case of infants, McNamara et al. speculated that sighs and startles were parts of a fixed sequence in an arou- sal pathway that begins in the brainstem and ends in cortical arousal [8]. It is also suggested that sighs are an independent brainstem reflex that is neither cortically mediated or influ- enced [8,9]. So far, we have noticed that sighs often occurred in association with elevation of chin muscle activ- ity in OSAS children. According to the standard criteria, Sleep Medicine 3 (2002) S33–S36 1389-9457/02/$ - see front matter q 2002 Elsevier Science B.V. All rights reserved. PII: S1389-9457(02)00161-2 www.elsevier.com/locate/sleep * Corresponding author. Tel.: 181-3-5803-5245; fax: 181-3-5803-5247. E-mail address: jkohyama.ped@tmd.ac.jp (J. Kohyama).