Recent advances in sudden infant death syndrome: possible autonomic dysfunction of the airways in infants at risk

Otolaryngic Manifestations in Children Presenting with Apparent Life-Threatening Events

Apparent life-threatening event (ALTE) is a term used to characterize an event of unknown cause after an infant is found limp, cyanotic, bradycardic, and/or requiring resuscitation. Like sudden infant death syndrome (SIDS), ALTE is a general term used until a precise diagnosis can be established. The relationship between ALTE and SIDS has not been clearly defined, although 7 to 15 percent of children with ALTE die of SIDS. If children with ALTE are at greater risk for SIDS, morbidity and mortality may be prevented if the underlying pathology can be identified and corrected or closely monitored. The otolaryngologist is being consulted more frequently to evaluate children who have been through an ALTE to help elucidate any underlying pathology that may have caused the near-death experience. This retrospective chart review reports the evaluation of 30 infants with ALTE requiring consultation by the Division of Pediatric Otolaryngology at the Children's Memorial Hospital in Chicago during a 3-year period. We reviewed the literature and here compare our findings with current animal models. Of the 30 children evaluated, 53% had gastroesophageal reflux, 40% had laryngeal abnormalities, 13% had tracheal abnormalities, and 10% had pharyngeal abnormalities. Thirteen percent of the children had nonotolaryngic anomalies identified during evaluation. Surgical intervention was required in 10 patients and medical treatment was used in 18. When evaluating a child with ALTE, a complete history and physical examination, evaluation for gastroesophageal reflux, assessment for upper airway obstruction by radiographs and endoscopy, and a multidisciplinary approach are recommended. (Otolaryngol Head Neck Surg 1997;116:575–9.)

Developmental characteristics of apnea in infants who succumb to sudden infant death syndrome

We compared the breathing characteristics of 40 infants who subsequently died of sudden infant death syndrome (SIDS) with those of 607 healthy infants matched for sex and age. The infants were between 2 and 19 wk old at the time of recording. Compared with the control group, the infants who died of SIDS experienced significantly more frequent episodes of obstructive and mixed sleep apnea. The duration of the apneic episodes did not exceed 15 s. Moreover, the SIDS group had a greater proportion of infants with obstructive and mixed apneic episodes than did the control group. In both groups, the frequency of episodes among male infants with apnea was greater than that among female infants. After the age of 9 wk, the proportion of male infants with episodes of obstructive apnea was greater in the SIDS group than in the control group. The frequency of apneic episodes decreased with age. The rate of decrease was significantly greater in the control subjects than in the SIDS group. This finding was made mainly in male infants. The present study provides further indirect evidence for a slower maturation of respiratory control in some infants who ultimately die of SIDS.

Heart rate response profiles during head upright tilt test in infants with apparent life threatening events

Sympatheticovagal imbalance causing episodes of severe bradycardia has been suggested as a cause of apparent life threatening events (ALTEs). The autonomic control of the heart rate in 18 infants with ALTEs and 12 controls was evaluated by the head upright tilt test. Five different heart rate response profiles (compared with the baseline) were observed during the tilt: (1) increase followed by a decrease and return to baseline; (2) sustained increase; (3) decrease followed by an increase and return to baseline; (4) sustained decrease; (5) no change. Eighty eight per cent of controls responded with heart rate increase followed by decrease or sustained increase compared with 55% of infants with an ALTE; a significantly greater proportion of infants with ALTEs than controls responded with heart rate decrease or no change in rate (45% v 8%). This altered reaction during a head upright tilt test may be an expression of an underlying autonomic dysfunction in infants who have experienced an ALTE.