Absent Hypoxic and Hypercapneic Arousal Responses in Children With Myelomeningocele and Apnea

Abstract

Hypoxic and hypercapneic arousal responses from quiet sleep were tested in seven infants with myelomeningocele and Arnold-Chiari malformation who were symptomatic with apnea and/or hypoventilation. All infants with myelomeningocele required tracheostomy and posterior fossa decompression. Responses were compared with those of nine healthy control infants. To assess hypoxic arousal, inspired Po2 was decreased until the end-tidal (alveolar) Po2 reached 45 mm Hg for a maximum of three minutes. Eleven studies were performed in seven infants with myelomeningocele, and arousal occurred in only two studies (18.2%). Eight of nine control infants aroused to hypoxia (89%). To test hypercapneic arousal, inspired Pco2 was increased until end-tidal Pco2 reached 60 mm Hg for a maximum of three minutes. Eight studies were performed on six infants with myelomeningocele, and arousal occurred in three studies (37.5%). All seven control infants studied aroused to hypercapnea (100%). Three infants with myelomeningocele subsequently died. Infants with myelomeningocele, Arnold-Chiari malformation, and apnea or hypoventilation have arousal deficits to respiratory stimuli.

Impact of Spina Bifida on Sleep Quality: Current Insights

“…The increased risk of SDB in patients with MMC is a consequence of the abnormalities in the spinal cord, brainstem function, pulmonary function, and upper airway maintenance that are commonly appreciated in this patient population. 33 , 34 , 36 , 38 , 39 In fact, commonly associated neurological conditions like CM-II and hydrocephalus are known to affect respiratory pattern and reflex response while sleeping, leading to SDB. 32 , 40 Abnormalities of the brainstem and respiratory centers may serve as the mechanism involved in producing central apnea, whereas compression of the nuclei of cranial nerves IX and X may result in upper airway obstruction due to decreased ability to maintain upper airway patency 41 MMC with CM-II results in abnormal brainstem control resulting in absent arousal responses to hypoxia and hypercapnia, and absent ventilatory responses to hypoxia and hypercapnia in these patients ( Figure 1 ).…”

“…Several studies have reported a higher prevalence of SDB in patients with MMC and CM-II by evaluating patients with the signs or symptoms suggestive of respiratory abnormalities, 36 , 39 , 53 or after retrospectively evaluating patients with MMC based on having any previously completed polysomnography. 32 Despite these findings, no clear predictors of SDB have been identified in patients with MMC and CM-II.…”

“…Individuals with MMC are likely to undergo multiple surgical procedures over the course of their lives. 36 , 39 , 50 Many of these patients undergo fetal surgical closure of the open MMC prior to birth. Otherwise, the remainder of children undergo this closure within 48 hours of birth.…”

“… 9 While the anatomic findings associated with CM-II are present in nearly all individuals with MMC, fewer than 10% of children undergo CM-II decompression surgery in the modern era. 9 , 36 , 39 , 50 , 61 Prenatal surgery has been shown to decrease the need for hydrocephalus surgery to as low as 40%, and decrease the anatomic severity of CM-II in children treated with prenatal closure compared to standard post-natal repair. 65 However, little is known about the effect of neurosurgical intervention on SDB in patients with MMC.…”

“…Studies have reported that more than half of infants with MMC will continue to demonstrate SDB often with CSA, periodic breathing, and hypoventilation despite relief of upper airway obstruction through CM decompression, shunt placement, and/or tracheostomy tube placement. 4 , 14 , 21 , 22 , 32 , 36 , 39 , 40 , 46 , 50 In fact, most studies reporting a high prevalence of SDB in CM-II patients were performed on patients after they had undergone neurosurgery, suggesting that SDB may develop regardless of neurosurgical intervention. Patel et al included repeat overnight polysomnography on nine children that underwent neurosurgical intervention (6 CM-II decompression, 4 HC shunt placement, 1 with both procedures), with repeat polysomnography indices indicating interval improvement in the severity of their SDB, though none of these improvements met statistical significance.…”