Elsevier

Clinical Neurophysiology

Volume 111, Issue 10, 1 October 2000, Pages 1788-1791
Clinical Neurophysiology

Spectral analysis of electroencephalogram during sleep-related apneas in pre-term and term born infants in the first weeks of life

https://doi.org/10.1016/S1388-2457(00)00417-XGet rights and content

Abstract

Objectives: A correlation between sudden infant death syndrome (SIDS) and apnea has been discussed in a variety of studies. We analyzed polysomnographic data in 51 infants and investigated correlations between the manifestation of apneas and changes in EEG pattern.

Methods: Measurements were performed by means of the commercial polysomnographic device ‘ALICE III’. Spectral analysis of certain parts of the registered EEG was performed.

Results: During apnea a reduction of the EEG amplitude was seen. The extent of the decrease differed slightly between the frequency bands.

Conclusions: According to the widespread agreement that a lower voltage of electrical brain activity is a fundamental sign of waking up, we hypothesize that the observed change might be an immature type of arousal reaction.

Introduction

Intense interest has developed and significant advances have been made in relation to respiratory control disorders in adult patients as well as in neonates and infants. Numerous current publications deal with pathophysiology, clinical evaluation, treatment and outcome of disorders with sleep apnea syndrome in newborn infants and young children. It is now established that the sleep apnea syndrome is also a significant pediatric problem that complicates diverse diseases. Among these, in the neonatal period apnea of prematurely born infants is the best known pediatric respiratory control abnormality. However, apnea of infancy is the more important clinical condition that seems to be related to cardiorespiratory control deficits such as SIDS. Sudden infant death syndrome (SIDS) continues to be a major pediatric enigma. Apart from starvation and infectious diseases, SIDS is one of the main causes for death in infancy worldwide. There is evidence that deficient cardiorespiratory control may be an important cause of SIDS. In former studies a correlation between apnea and a risk for SIDS has been discussed (Hodgeman, 1998) and a higher duration of apnea in infants who suffered from SIDS was demonstrated (Schlüter et al., 1996). However, up to now clinical analysis has not been successful in establishing a reliable screening method to identify risk patients without employing specialized sleep laboratories. Because morphological brainstem abnormalities were found in post-mortem examinations of SIDS victims, functional brainstem abnormalities were discussed as a possible cause of an increased epidemiological risk for SIDS (Obonai et al., 1997, Rowland et al., 1991). These functional abnormalities include excess periodic breathing, increased frequency and prolonged duration of sleep apneas (Sher et al., 1986). Furthermore, a deficit in arousal responsiveness or gasping is considered to be a necessary prerequisite for SIDS to occur (Beckerman et al., 1992, Tal et al., 1988, Wulbrand et al., 1998). Altogether, the delay in the maturation of sleep patterns may affect other physiological functions that are closely linked with sleep–wake activity and brain function.

Brain maturation follows a continuous process from embryonic life to extrauterine childhood that includes dendritic arborization and synaptogenesis as well as the evolution of functional transmission sites and improved conductance properties (Scher, 1997a, Scher, 1997b). The registered functional integration or disintegration seen in the EEG spectra can be interpreted as an indicator of the degree of functional connectivities (Amzica and Steriade, 1995, Contreras and Steriade, 1996). Moreover, regional differences of the cortical EEG were demonstrated after sleep deprivation in an animal model (Schwierin et al., 1999).

The most common method to identify apnea in the neonates is the simultaneous registration of EEG activity with cardiac and pulmonary parameters as parts of the polysomnography (Myers et al., 1997). The registered pattern allows the classification of apneas in different classes. In contrast to adults EEG patterns are less characteristic and only few (Hrachovy and O'Donell, 1999) are sufficiently defined. Thus far, only clinical conditions like epileptic seizures could be detected by a number of pre-selected criteria. In respect to respiratory control, no studies deal with the question of whether disturbances of respiratory control influence or at least coincide with the appearance and/or frequency distribution of the EEG in neonates and young infants. The aim of our investigations was to study relations between the manifestation of apneas and changes in the EEG pattern.

Section snippets

Patients and methods

The study involved 51 pre-term and term infants with a gestational age between 22 and 40 weeks (mean 34.7 weeks) who suffered from respiratory disturbances of different degrees of severity. Measurements were carried out after release from the NICU and partly after their discharge at home. The clinical indications necessary to perform the polysomnography were unstable respiratory control and clinical risk of SIDS. Polysomnography took place between the 25th and the 100th week (mean 45.2 weeks)

Results

The results are depicted in the figures. Fig. 1 shows the absolute power of the EEG position C3T3. Values of absolute power during apneas are lower compared to the other subgroups, indicating a reduction of the EEG amplitude during failure of breathing. The extent of the decrease slightly differs between the frequency bands. The highest relative reduction of about 45% was observed in the theta band.

The results of absolute power for frequency bands alpha to beta 2 (peak frequency of EEG position

Discussion

Sleep states of adults are characterized by the occurrence of delta waves and specific pattern like sleep spindles. This classification cannot be applied to pre-term and term infants because specific patterns are missing. Analysis of sleep patterns in infants therefore is based on the amplitude of delta waves and includes movements of the body and the eyes (Breidbach et al., 1998). During sleep the percentage of delta waves and amplitudes increases. On the other hand, the process of waking up

References (17)

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This work was presented in part at the 14th European Congress on Sleep Research, Madrid, 9–12 June 1998 (Abstract in J Sleep Res 1998;7(2):241).

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