Magnetic resonance imaging of the pharynx in OSA patients and healthy subjects

Abstract

Obstructive sleep apnoea (OSA) occurs because of recurrent narrowing and occlusion of the velopharynx (VP) during sleep. The speci®c cause of OSA is unknown. Cephalometric radiography, ®breoptic nasopharyngoscopy, acoustic re¯ec-tion techniques, and computerized tomography have limitations (dynamic and tridimensional evaluation) in the mechanism of occlusion investigation. Static and dynamic examination of the soft tissue structures surrounding the upper airway during the respiratory cycle in wakefulness and sleep, can lead to a better understanding of the process.Ultrafast magnetic resonance imaging (one image per 0.8 s) was used to study the upper airway and surrounding soft tissue in 17 patients with OSA during wakefulness and sleep, and in eight healthy subjects whilst awake.The major ®ndings of this investigation in the 25 subjects were as follows: 1) the VP was smaller in apnoeic patients, only during part of the respiratory cycle; 2) the variation in VP area during the respiratory cycle was greater in apnoeic patients than in controls, particularly during sleep, suggesting an increased compliance of the VP in these patients; 3) VP narrowing was similar in the lateral and anterior-posterior dimensions, both in controls and apnoeic patients while awake; apnoeic patients during sleep have a more circular VP upon reaching the minimum area; 4) there was an inverse relationship between dimensions of the lateral pharyngeal walls and airway area, probably indicating that lateral walls are passively compressed or stretched as a result of changes in the airway calibre; and 5) soft palate and parapharyngeal fatpads were larger in apnoeic patients, although their role in the genesis of OSA is uncertain.It was concluded that changes in the velopharynx area and diameter during the respiratory cycle are greater in apnoeic patients than in normal subjects, particularly during sleep. This suggests that apnoeic patients have a more collapsible velopharynx, this being the main mechanism of obstruction. Eur Respir J 2001; 17: 79±86. Obstructive sleep apnoea (OSA) occurs because of recurrent narrowing and occlusion of the upper airway during sleep [1], and the site of obstruction is most commonly at the level of the velopharynx (VP). Unfortunately, the speci®c cause of this obstruction is unknown [2±4]. Cephalometric analysis [5,6], which provides information on the morphology of the upper airway, does not allow dynamic evaluation. Fibreoptic nasopharyngoscopy with the Mu È ller manoeuvre [4,7,8] allows a dynamic evaluation of the pharyngeal airway, but is usually performed with the patient awake, and the changes in pressure and shape during the manoeuvre are not necessarily representative of the physiological changes during quiet breathing. Acoustic re¯ection has been used to demonstrate increased effective compliance of the pharynx during wakefulness in OSA patients in response to changes in pharyngeal intraluminal pressure and lung volume [9,10]. A major limitation of the acoustic re¯ection technique is its inabi...

The biomechanics of the human tongue

“…It was also found using MRI, that the changes in the velopharynx cross-sectional area during respiration of OSA subjects was significantly different to that of healthy subjects, especially during the sleep state. This may contribute to OSAS patients have a more collapsible velopharynx [20].…”

Avaliação da faringe de pacientes portadores de apneia obstrutiva do sono, por meio da tomografia computadorizada multislice obtida em vigília e durante o sono

“…A região RL se estende da ponta da úvula à base da epiglote (11) . Muitos estudos têm sido realizados na tentativa de demonstrar que o tamanho e a morfologia das estruturas que compõem as vias aéreas superiores e as dimensões das estruturas a ela adjacentes influenciam o calibre da via aérea superior dos pacientes com SAOS (5,6,(11)(12)(13)18,29,(32)(33)(34)(35)(36)(37)(38)(39)(40)(41) .…”

“…Após revisão de literatura, notamos que havia poucos estudos por imagem realizados durante o sono, em pacientes com SAOS (34,44,48) . Esse número tornou-se ainda menor quando procuramos estudos realizados sob sono espontâneo, e não sob sedação (35) .…”

“…Este dado confirma outros já descritos na literatura, segundo os quais a morfologia faríngea nos pacientes com SAOS é mais arredondada, se comparada à de indivíduos livres da doença (69) . Essa alteração da morfologia da VAS superior nos pacientes com SAOS também foi descrita por outros autores (34,41) . Li et al (41) O achado de palato mole espesso e redução do espaço aéreo retropalatal nos pacientes com SAOS também já foi descrito na literatura (12,39,63) .…”

“…Assim como na literatura, este estudo constatou que mudanças na área e diâmetro da faringe durante o ciclo respiratório são maiores em portadores de SAOS, se comparadas com as de indivíduos saudáveis (34) . …”