Pneumoparotid: A case report and review of its pathogenesis, diagnosis, and management.
Pneumoparotid is considered to be a rare entity, but the diagnosis might not be as uncommon as reported. We report a case in which computed tomography incidentally revealed air in the parotid ducts bilaterally. Treatment is aimed at the elimination of predisposing and causative factors, but because our patient denied any symptoms or precipitating factors and had a benign presentation, no immediate intervention was initiated.
Pneumoparotid is the presence of gas in the parotid gland or salivary ducts. It is the result of an increase in intraoral pressure and the subsequent forced entry of air through Stensen's duct. Pneumoparotid can be caused by dental instrumentation, positive-pressure ventilation during anesthesia, chronic cough, and playing a wind instrument and other physical activities that involve forceful exhalation.
The clinical examination can reveal unilateral or bilateral parotid swelling, subcutaneous emphysema, or frothy salivary secretions. Computed tomography (CT) and standard sialography confirm the diagnosis. Treatment is aimed at the elimination of precipitating factors. Two treatments have been considered for sialadenitis secondary to recurrent or chronic episodes of pneumoparotid: transposition of Stensen's duct and parotidectomy. In this article, we present a case of pneumoparotid, and we review its pathogenesis, diagnosis, and management.
A 50-year-old man came to the otolaryngology clinic with a long history of postnasal drainage and nasal congestion that were refractory to medical management. Screening CT of the paranasal sinuses revealed well-aerated paranasal sinuses and air in Stensen's duct bilaterally (figure).
The patient had not undergone any recent dental manipulation and had never played a wind instrument. Head and neck examination revealed no evidence of parotid swelling. The patient was afebrile, and the saliva flow from the ducts on manual parotid pressure was normal. In view of these findings, no immediate intervention was initiated. The patient was followed clinically for the potential occurrence of parotitis or sialadenitis, and he reported no symptoms at 1 month.
Pneumoparotid is the result of an increase in intraoral pressure and the subsequent insufflation of air into Stensen's duct. Other terms for this condition include pneumatocele glandulae parotis,  wind parotitis,  surgical mumps and anesthesia mumps,  and pneumosialadenitis. 
Pathogenesis. The diagnosis is considered rare, but it might not be as uncommon as previously reported. A review of the literature reveals reports of several etiologies. In 1865, Hyrtl first described this condition in musicians who were learning to play wind instruments.  Glassblowers are known to be predisposed to pneumoparotid, as well.  Following anesthesia, patients sometimes strain and cough during extubation while receiving positive pressure, which can cause air to insufflate into the parotid gland.  Injury during a dental procedure can occur when the dentist is working near the maxillary molars or when the angulation of instruments is improper.  Pneumoparotid has also been induced by nose blowing,  blowing up balloons,  chronic attempts to suppress cough, [8,9] and rapid decompression while scuba diving.  It can also be self-induced, and the literature contains an increasing number of reports involving pediatric and adolescent patients who induce parotid insufflation to avoid sc hool or gain attention. [5,1,12] Other episodes have been attributed to anatomic abnormalities, including a patulous Stensen's duct,  masseter muscle hypertrophy,  and buccinator muscle weakness. 
The anatomy of Stensen's duct normally prevents a retrograde influx of air. Redundant mucosal folds surround the slit-shaped orifice, providing a seal when intraoral pressure increases. In addition, the diameter of the duct orifice is smaller than that of the duct itself.  The buccinator muscle further acts to compress the duct during contraction. However, large increases in intraoral pressure can overwhelm normal protective mechanisms and allow air and saliva to enter the ductal system. Air rupturing through the parotid acini can extend to the parapharyngeal space and cause subcutaneous emphysema and airway obstruction. This can progress to involve the retropharyngeal space.
Diagnosis. The history and physical examination are key to the diagnosis. Parotid swelling can be unilateral or bilateral, depending on its cause. Cases involving dental instrumentation are usually unilateral on the side where the work was done. It is necessary to exclude obstructive, inflammatory, metabolic, and neoplastic causes of parotid enlargement. The clinical examination might reveal subcutaneous emphysema, crepitation along the course of Stensen's , [1,4,6,10,14] and frothy saliva. [1,4,6,13,14] Patients usually experience pain, tenderness, and erythema. Salivary gland enlargement usually resolves within several days. In contrast, fever and toxicity accompany parotitis as a result of the presence of gas-forming organisms. Recurrent parotid insufflation can predispose the patient to recurrent parotitis and sialectasis.
Radiographic examination confirms the diagnosis. CT and sialography delineate the salivary ducts, salivary gland tissue, and surrounding structures. Ductal dilation is a common finding. Although a normal duct pattern is often seen after repeated episodes of air reflux, the secondary ducts can become dilated and strictured.
Treatment. Treatment is directed toward elimination of the causative or predisposing factors. Depending on the patient's condition, other measures can be taken, including reassurance, massage, hydration, warm compresses, and the prescription of anti-inflammatory medications, prophylactic antibiotics, and sialagogues. Wind instrumentalists and glassblowers can be taught techniques to reduce their chances of insufflation. In cases of self-induction, psychological counseling might be of benefit. Surgical intervention--including salivary gland duct ligation,  the transposition of Stensen's duct to the tonsillar fossa, [4,13] and parotidectomy--can be considered for recurrent infectious episodes.
From the Division of Otolaryngology, Department of Surgery, Duke University Medical Center, Durham, N.C. (Dr. Huang and Dr. Misko), and the Department of Radiology, Asheville (N.C.) VA Medical Hospital (Dr. Schuster).
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|Publication:||Ear, Nose and Throat Journal|
|Date:||Apr 1, 2000|
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