Canadian Neighbor Pharmacy: Discussion of Sleep in Pierre Robin Syndrome
Our patients, all of whom were chronic snorers, suffered minor degrees of sleep disturbances (a higher sleep disordered breathing index, more movement arousals and sleep stage changes, less time spent in REM sleep, and minor degrees of arterial oxygen desaturation compared to our normal subjects).
The most obvious cause for an increased incidence of such sleep disturbances in patients with the Pierre Robin syndrome is anatomic. Rivlin et al negatively correlated the apnea index with overall posterior displacement of the mandibular symphysis in adults with obstructive sleep apnea. The apnea index also correlated negatively with awake pharyngeal crosssectional area as measured by acoustic reflection in these patients. Presumably, the small mandible retro-displaces the base of the tongue, narrowing the upper airway in both the awake and asleep subject. Severe narrowing of the upper airways has also been demonstrated in patients with obstructive sleep apnea by computerized tomographic scanning during sleep and wakefulness and during sleep by fiberoptic phar-yngoscopy. The region with the smallest cross-sectional area was noted to be posterior to the soft palate and base of the tongue in both normal subjects and those patients with obstructive sleep apnea. The sleep disordered breathing index correlated negatively with pharyngeal size. Therefore, our patients with shortened mandibles, which could lead to retro-displacement of the tongue, could be expected to have smaller pharyngeal cross-sectional areas. This might increase upper airway resistance, resulting in obstructive sleep apnea. All of our patients had small mandibles, although the were not markedly small. This would explain why they had minor sleep abnormalities but did not suffer from frank obstructive sleep apnea. This would also explain, with their minimal sleep disturbances, why there was no significant correlation between their cephalometric and sleep disordered breathing indices.
Pruzansky and Richmond demonstrated only partial normalization of mandibular size in three patients by seven months of age. Michelet et al demonstrated normal mandibular measurements in five children aged 7 to 11 years, but they did not have early cephalometric evidence of micrognathia. Others have noted the persistence of micrognathia well beyond infancy in some patients, and our results are in accord with these. The particular predisposition of patients with Pierre Robin syndrome to develop frank obstructive sleep apnea following palatoplasty to correct speech problems supports the hypothesis that their upper airways remain compromised. What is it – Insulinoma? The answer is given on Canadian Neighbor Pharmacy website.
Other possible causes for the sleep abnormalities we observed in these patients with Pierre Robin syndrome include central nervous system abnormalities, muscular hypotonia, palatal abnormalities, or adenoton-sillar enlargement secondary to recurrent infections. Patient 6 had, in fact, suffered a cardiac arrest as a neonate. We did not observe gross glossal hypotonia, though Michelet et al comment upon glossal muscular abnormalities in their patients.
Mallory and Paradise believed that the marked relief of upper airway obstruction occurs too early in life (at 3% months of age in many cases) to be accounted for by mandibular growth; however, Pruzansky and Richmond nicely demonstrated a large increase in upper airway size with partial normalization of the facial contour using cephalometric roentgenography in such a young patient. Three of our patients had their tonsils or adenoids (or both) removed several years prior to the sleep studies, so this would not explain their present propensity to have such sleep disturbances.
Chronic snoring was very common in our patients (13 of 20 responding to the questionnaire). Even if we assume that none of the nonresponders snored, then the rate still appears to be high (13 of 36). Lugaresi et al reported a prevalence of snoring of only 5 percent in children younger than 16 years old. Although our eight subjects may represent one end of the spectrum of patients with Pierre Robin syndrome surviving to adolescence, they still represent a considerable proportion of the population questioned.
According to Lugaresi et al,
The feet that snoring is related to stenosis of the upper airways, that it can be associated with obstructive apnea, and may reduce alveolar ventilation and increase systemic and pulmonary pressure, confirms the similarities between it and the OSA syndrome. These findings and the fact that, in clinical history, OSA syndrome can be preceded by heavy and habitual snoring for decades, suggests that snoring represents the first stage in the natural history of such syndrome.
As both snoring and obstructive sleep apnea increase with age, these patients with Pierre Robin syndrome may be at risk for more severe obstructive sleep apnea with advancing years, although they exhibit only minor degrees of sleep disturbances at the present time. These patients may also be at risk for developing systemic arterial hypertension and myocardial infarctions (What is an acute myocardial infarction?).
Our patients had large right ventricular end-diastolic dimensions. Their normal right-sided systolic time intervals suggest that they do not have significantly elevated pulmonary vascular resistance. Patients with Pierre Robin syndrome do have an increased incidence of cardiac defects, but our examination did not demonstrate any intrinsic cardiac defects. The ventricular dilatation may be the residua of previous nocturnal hypoxemic insults, presumably when the patients had relatively smaller mandibles; however, it could be a result of the ongoing minor nocturnal hypoxemic events that our patients have demonstrated. Alternatively, such dilatation could be secondary to large stresses exerted upon the cardiac chamber through the large negative intrapleural pressures generated during snoring or obstructive sleep apnea. Cardiac conduction defects have been seen in snoring children without obstructive sleep apnea. The minor degree of ventricular dysfunction we have seen is appropriate for the minor degree of micrognathia and sleep disturbances we noted in our patients.
Patient A unexpectedly demonstrated prolonged central apneas with almost no obstructive component. His snores were, in fact, large snorts when he terminated his central apneas. He had surgical advancement of his mandible to correct significant clinical obstructive sleep apnea one year prior to the sleep study. Unfortunately, he had had no sleep study done prior to the operation. He also had the most enlarged right ventricle and one of the smaller mandibles and SNB angles. Guilleminault et al demonstrated that central apneas may persist for many months following tracheostomy for obstructive sleep apnea. Presumably, this is due to prolonged central nervous system depression and sleep fragmentation while the patient suffered from obstructive sleep apnea and severe hypoxemia. It has also been shown that central apneas associated with large esophageal pressure swings could precede the development of frank obstructive apneas following mandibular osteotomy. Sackner et al demonstrated that one may mislabel obstructive apneas as central when only using rib cage-abdominal motion and a thermistor to record the event. Any of these possibilities could explain this patients results.
In conclusion, our patients with Pierre Robin syndrome had an increased incidence of minor, although clinically insignificant, sleep disturbances associated with small decreases in mandibular size. Although clinically insignificant, one of our patients demonstrated frank sleep apnea. Increased right ventricular size was present in these patients. As both snoring and obstructive sleep apnea are primarily a problem of middle age and older male adults, with an increasing prevalence with years, our patients’ problems have the potential of not only ameliorating with mandibular growth but also worsening with age. These patients should be carefully evaluated for sleep disturbances and their sequelae.