Discussion
This study is the first to report a patient with obstructive sleep apnea syndrome accompanying pneumoparotid, who was treated effectively with an oral appliance and was followed up for 10 years.
Pneumoparotid describes the presence of air within the duct system and/or parenchyma of the parotid gland secondary to its reflux through Stensen’s duct. Parotitis associated with pneumoparotide is referred to as pneumoparotitis. The pneumoparotid has been observed in glass blowers until the first half of the 20th century.2-4 In those days, 6%–10% of glass blowers had symptoms of suspected pneumoparotid.4 More pressure is required to produce larger glassware than delicate works and is more likely to cause pneumoparotid.3, 4 Fortunately, subsequent innovations and mechanization have dramatically reduced the pneumoparotid as an occupational disease in glass workers.
Previous studies indicated an association between playing wind instruments, such as the trumpet,1, 40, 41horn,1, 8, 42 tuba,43clarinet,8 flute,44 or recorder.45 The Stensen’s duct valve prevents reflux into the parotid gland by the smaller diameter of the orifice, which is covered by redundant mucosal layers. The duct is laterally compressed by the masseter muscle and the buccinator muscle contraction with an increase in oral pressure. If the intraoral pressure exceeds the protective mechanism, pneumoparotid can occur. Hyrtl1stated that when pressure in the oral cavity increases when playing a wind instrument, air can enter retrogradely from the orifice of Stensen’s duct. He added that it is easier for beginners to pull in the air when they blow with their cheeks full, and less likely to occur when they learn the appropriate embouchure technique.
Gazia et al.46 reviewed 49 reports and analyzed 54 patients with pneumoparotid or pneumoparotitis. The most frequent etiology is self-induction by blowing the cheeks, which mainly involves children for conflicts with parents, excuses for not going to school, and nervous tics.46 Treatment with antibiotics and steroidal anti-inflammatory drugs is the most common treatment. Behavioral therapy is applied to remove bad habits such as blowing cheeks; in some cases, supportive psychotherapy is necessary.7, 8, 10, 11, 41
The relationship between pneumoparotid and sleep apnea syndrome remains to be elucidated. This patient played a traditional Japanese wind instrument, hichiriki (Fig 4), for 20 years from the age of 7 years. The hichiriki is made of bamboo and is small compared to other wind instruments (Fig 3), but it requires considerably high pressure to play and emits a very large sound. Kreuter et al.47reported intraoral pressure while playing various wind instruments; however, hichiriki was not included. Although the patient had seldom played hichiriki for 30 years after the age of 27, it might be a predisposing factor for enlargement of the orifice of the Stensen’s duct. It was suspected that air reflux occurred during sleep, as the crepitus and swelling in the parotid region were prominent when waking up. The patient noticed the first swelling of the right parotid region when he boarded an airplane and slept, and the airplane landed. The sleep test indicated that the patient had a mild obstructive sleep apnea syndrome. Playing hichiriki could be a predisposing factor, and the first occurrence of pneumoparotid was triggered by an increase in barometric pressure on the board. Considering the fact that the patient boarded only once and pneumoparotid recurred, an increase in intraoral pressure could be a plausible cause of pneumoparotid. Cabello et al.22 reported a case of pneumoparotid, who blew severely overnight. The patient in this study did not snore. He might have been blown during sleep. The oral appliance with anterior opening might have helped prevent the oral cavity from increasing intraoral pressure during sleep. Oxygen saturation was considerably reduced, and during sleep apnea, the oral pressure can be increased, resulting in pneumoparotid.
In 1995, the American Sleep Disorders Association issued guidelines stating that oral appliances are indicated for snoring, mild obstructive sleep apnea, and moderate to severe sleep apnea if continuous positive airway pressure is not accepted or if surgery is not appropriate.48 Various oral appliances have been increasingly used in the treatment of sleep apnea syndrome. Many randomized trials have confirmed the effects of oral appliances.49-55 Recent guidelines have extended indications to moderate and severe sleep apnea patients when a patient refuses continuous positive airway pressure therapy after being informed about the risks.56 All appliances for the treatment of sleep apnea syndrome are constructed with the goal of advancing the position of the mandible and tongue in order to enlarge the airway or reduce its collapsibility. This may lead to an improvement in the upper airway dimensions and possible effects on upper airway muscle tone.57 It is indispensable to suppress events that increase intraoral pressure for patients in this report. An oral appliance to reduce intraoral pressure with anterior opening was fabricated and inserted during sleep (Fig 4). Some researchers have reported patients with pneumoparotid accompanied by obstructive sleep apnea syndrome.22-24 Long-term use of oronasal continuous positive airway pressure23, 24 or mandibular advancement device22 can be a potential cause of pneumoparotid. In a recent review46, 24.1% of patients with pneumoparotid disease revealed an unknown etiology. The average age of idiopathic cases was 28.6 years. In some patients, the pneumoparotid gland can be related to sleep apnea syndrome. Further studies confirmed by polysomnography in larger cases may be necessary to clarify this hypothesis.