Pneumoparotid with imaging findings: A case report and review of literature

Abstract

BACKGROUND

Pneumoparotid is a rare disease associated with retrograde airflow into the ductal system. There is no established treatment for this disease, which has no known complications. Mouth puffing and playing wind instruments are known to be the causes of this disease.

CASE SUMMARY

We managed a case, in which pneumoparotid suddenly recurred 4 months after surgery for purulent parotiditis. The patient did not report any obvious etiological factors, such as mouth puffing or playing a wind instrument. We reviewed 128 articles (from 1941 to 2023) that reported on a total of 166 patients with pneumoparotid, including the patient from the present case report, with imaging findings. This is the first reported case of pneumoparotid following surgery for purulent parotitis. The etiology in our case was classified as idiopathic.

CONCLUSION

Imaging findings could be sufficient for accurate pneumoparotid diagnoses and the exclusion of complications; computed tomography could be useful.

Key Words: Computed tomography; Imaging findings; Parotid gland; Pneumoparotid; Pneumoparotitis; Case report

Core Tip: Pneumoparotid is a rare disease linked to retrograde airflow into the parotid ductal system, often caused by mouth puffing or playing wind instruments. No established treatment exists, and it typically has no complications. We present a unique case of pneumoparotid recurrence 4 months after surgery for purulent parotitis without typical etiological factors. Our review of 128 articles (1941-2023), involving 166 patients, identified this as the first reported case post-parotitis surgery, classified as idiopathic. Imaging, especially computed tomography, proves crucial for accurate diagnosis and excluding complications.

INTRODUCTION

Edema or discomfort in the parotid region or facial area is a common patient presentation in the daily practice of otolaryngology, oral and maxillofacial surgery, pediatrics, and dentistry. Parotid gland swelling can stem from several underlying factors, such as inflammation, viral infection, sialoliths, benign or malignant tumors, autoimmune disorders, and endocrine abnormalities. Pneumoparotid is a rare cause of swelling and discomfort in the parotid gland area. The term pneumoparotid was first used by Hyrtl and Mundhöhlein 1865 to describe this condition in individuals engaged in playing wind instruments[1]. Until the mid-20^th century, pneumoparotid was primarily associated with playing wind instruments and glassmaking. However, in 1915, Hemphill reported a case of a patient who developed self-induced pneumoparotitis in the French Legion of North Africa, which was initially misdiagnosed as mumps[2]. Another case of a patient who developed self-induced pneumoparotid was reported in 1918[3]. Subsequently, several cases of pneumoparotid have been reported worldwide[1-131]. Recently, the incidence of pneumoparotid with an iatrogenic cause (such as dental treatment or continuous positive airway pressure) has been increasing[6,8,11,12,33,51,93,95,98,116,127]. Herein, we report the case of an 83-year-old man who developed pneumoparotid approximately 4 months after undergoing surgery for purulent parotiditis. Although surgical treatments for purulent parotiditis have been performed in numerous patients in the fields of otolaryngology and oral surgery, to the best of our knowledge, no study has reported on the postoperative complications associated with pneumoparotid. As the complications occurred 4 months after surgery in our patient, it can be inferred that the etiology of pneumoparotid was not solely attributable to the surgical procedure but may have involved other contributing factors as well. Herein, we aimed to review previous case reports of this disease and show that objective evaluation using imaging studies and timely and accurate identification of identifying disease etiology are important for its treatment. Computed tomography (CT) may help identify this disease with a high rate of accuracy, highlighting the relevance of this method in this context.

CASE PRESENTATION

Chief complaints

An 83-year-old male patient presented to our hospital with concerns of swelling and crepitus in the left cheek.

History of present illness

The patient’s medical history included hypertension and pacemaker placement due to a complete atrioventricular block.

History of past illness

The patient had undergone surgical intervention in the Dentistry and Oral Surgery department of the Sapporo Tokushukai hospital for the management of Stensen’s duct orifice stenosis resulting from recurrent purulent parotiditis. The patient’s medical history included left suppurative parotitis and abdominal aortic aneurysm surgery. The patient experienced satisfactory postoperative recovery; however, approximately 4 months later, he presented to our hospital with concerns of swelling and crepitus in the left cheek.

Personal and family history

The patient denied any occupational or habitual exposure to increased intraoral pressure, such as playing wind instruments or inflating balloons.

Physical examination

The patient’s cheeks were swollen but were neither red nor warm. Palpation of the left cheek revealed the presence of frothy salivary flow (Figure 1).

Figure 1 Foamy saliva flowing out of the left Stensen’s duct.

Laboratory examinations

The patient’s blood test results were normal, lacking any evidence of an inflammatory reaction. Saliva culture results did not show the presence of gas-producing bacteria.

Imaging examinations

Ultrasound (US) evaluation revealed areas of heightened echogenicity in the left parotid gland and Stensen’s duct, suggesting the presence of air (Figure 2). CT using a 320-row multidetector CT scanner (Aquilion one, Canon, Tokyo, Japan) was performed.

Figure 2 Ultrasound evaluation. A: Swelling and hyperechoic areas, suspected of containing air bubbles, are scattered in the left parotid gland; B: A belt-like hyperechoic region, suspected of containing air bubbles, is noted along the left Stensen’s duct.

FINAL DIAGNOSIS

CT (Figure 3) confirmed the presence of swelling accompanied by air accumulation in the left parotid gland and Stensen’s duct, with no evidence of subcutaneous emphysema or pneumomediastinum.

Figure 3 Computed tomography scans reveal swelling of the left cheek. Marked dilation with air density is observed extending from the left Stensen’s duct to the intraparotid duct. No subcutaneous emphysema is noted.

TREATMENT

As the patient’s left pneumoparotid was not complicated by infection, conservative treatment was employed, which involved expelling air from the parotid gland through massage.

OUTCOME AND FOLLOW-UP

The patient’s left pneumoparotid persisted after 6 months of follow-up, but with no worsening of swelling, pain, or warmth in the left cheek. Currently, patients with pneumoparotid are required to consult an oral surgeon when symptoms worsen.

DISCUSSION

Parotid gland swelling is a commonly encountered manifestation in daily clinical practice[4-131]. Considering its various etiologies, including autoimmune diseases, recurrent mumps, sarcoidosis, and parotid tumors, pneumoparotid is a rare and challenging-to-diagnose condition[4,5]. Pneumoparotid occurs when air refluxes through the Stensen’s duct due to increased intraoral pressure, leading to emphysema within the gland and duct[35]. Typically, the mucosal opening of the Stensen’s duct is narrower than that of the parotid duct and has a slit-like structure, which functions to regulate airflow[20]. If pneumoparotid extends beyond the capsule, it can result in subcutaneous emphysema, pneumomediastinum, and rarely, pneumothorax. The diagnosis relies on clinical findings, such as crepitus in the swollen area and the presence of frothy saliva upon parotid gland massage. Moreover, imaging examinations, such as CT and US scanning, are used to confirm the presence of pneumoparotid.

When this condition is suspected, a comprehensive medical interview is necessary to identify the potential factors contributing to the elevated oral pressure. Although glass craftsmen and wind instrument players are commonly affected by this condition, occupation-related cases are rarely reported in Japan. Many cases are associated with abnormal habits, psychogenic factors, balloon inflation, and breath holding. In addition, iatrogenic cases related to dental treatments, respiratory disease management, and medical examinations have been reported recently[6,8,11,12,33,51,93,95,98,116,127]. Moreover, some patients develop pneumoparotid with no evident cause[4,5]. In our case, we speculated that the pneumoparotid was associated with the patient’s medical history because the patient developed pneumoparotid on the same side as the previous surgery. However, it was unlikely to be iatrogenic, given the delayed onset several months postoperatively.

To our knowledge, this is the first study to report on the imaging findings of pneumoparotid. We evaluated the diagnostic contribution of CT scans, US images, and radiographic images, including their ability to detect complications. CT scans were required to adequately assess the complications associated with pneumoparotid in our case. Globally, there have been fewer than 200 reported cases of pneumoparotid, and further large studies are required to determine the standard diagnostic and treatment protocols for this disease.

Given the rarity of this disease and the challenges associated with designing a large study on the diagnosis, treatment of this disease, and pathogenesis, we conducted a literature comprehensive review. The PubMed, Scopus, Web of Science, Business Source Complete, Ovid, Google Scholar, SciElo, LILACS, Japan Centra Revuo Medical database, CiNii, and J-Stage databases were searched using the following keywords "pneumoparotid", "pneumoparotitis", and "pneumoparotide". The total number of records from the databases was 867 (Google Scholar: 267; Business Source Complete: 223; PubMed: 103; Scopus: 85; Web of Science: 66; CiNii: 38; Ovid: 36; Japan Centra Revuo Medical database: 32; J-Stage: 9; SciElo: 4; and LILIACS: 4), and an additional 5 records were obtained from manual searches of relevant papers and books. Duplicate reports and double publications from the same cases and cases without imaging findings were excluded. Supplementary Table 1 summarizes the results of the 128 articles on pneumoparotid.

The authors of some articles did not provide details of the course of treatment and were contacted by electronic mail for supplemental information[75,92,102]. Meanwhile, some of the authors reported detailed progress of the examined patients. We analyzed data from 166 patients diagnosed with pneumoparotid worldwide (1941-2023), including the present case, with studies using sialography, US, radiography, CT, and magnetic resonance imaging (MRI) (Table 1). Data on a total of 166 patients (mean age: 28.6 years) from 128 studies were reviewed. The patient in our case report was the oldest. This disease was approximately three times more common in men than in women[4,5]. The chief complaints often included swelling (92.9%) and pain (36.9%). Our patient was a man presenting with swelling of the left parotid gland. Symptoms of crepitus in the parotid region (75.8%) and frothy saliva from the orifice (72.2%) are characteristic of this disease. Our patient also had these symptoms. The disease equally affected the left, right, and both parotid glands. Patients with this condition frequently visited otolaryngologists, ear-nose-throat doctors, and head and neck surgeons (53.0%), followed by dentists, oral and maxillofacial surgeons, oral surgeons (13.3%), emergency room doctors (10.8%), pediatricians (9.0%), and internal medicine doctors (2.4%). The most frequent etiology of pneumoparotid was self-induction by mouth puffing (29.5%). Self-induced pneumoparotid was more prevalent in children aged < 18 years (55.1%), i.e., pediatric patients with self-induced pneumoparotid, which was often associated with school or home stress. Idiopathy (21.7%) was also frequently reported as an etiology. Pneumoparotid due to mouth puffing (13.9%) or another self-induced behavior presented in a similar manner; however, abnormal habits that made patients unconsciously puff their mouths made the treatment challenging. The rate of iatrogenic disease was approximately 11.4%, with increased reporting in recent years[6,8,11,12,33,51,93,95,98,116,127], especially for cases associated with dental treatment. Most patients underwent medical treatment, such as antibiotic, analgesic, and steroid administration (46.4%). Many patients who did not respond to antibiotics (15.6%) had pneumoparotid caused by self-induction or abnormal habits. A significant proportion of patients positively responded to behavior modification therapy (26.5%) and psychotherapy (8.7%), highlighting the need for detailed patient history in disease management. Some patients required surgery (9.6%)[17,21,22,29,30,41,42,59-61,63,72,75,91,111,130]. Subcutaneous emphysema (33.7%), pneumomediastinum (10.2%), and pneumothorax (0.6%)[68] were reported as complications. Patients with complications were approximately three times more likely to require surgery. Considering the risk of airway obstruction due to subcutaneous emphysema and mediastinitis due to pneumomediastinum, a detailed examination using CT scanning is important. Before the 1980s, sialography was the primary imaging modality for evaluating parotid emphysema; however, CT, US, and radiography have been commonly used in recent years. CT scans have an accuracy of 99.1%. Only one of the 109 patients could not be accurately evaluated by CT scans owing to the presence of artifacts associated with dentures[12]. Of the seven patients who underwent MRI scanning, three had no abnormal findings[12,45,50,60,79,81,90]. There were no abnormal findings in any of the five patients who underwent panoramic dental radiographs[12,44,79,116]. Therefore, MRI and panoramic dental radiograph were not useful in this context. Both CT and US evaluations were performed, and the US did not detect parotid emphysema or any other complications in six of 23 patients[67,96,102,104,113,131]. Air appears as a bright spot on a US image. Nonetheless, it must be distinguished from calcification and salivary stones. CT makes distinguishing between calcification and air straight forward and offers a more objective assessment compared to US. However, a history of X-ray exposure must be considered when performing a CT scan. Radiation exposure to the thyroid should be avoided, especially in children. As approximately 10% of patients with complications require surgery[17,21,22,29,30,41,42,59-61,63,72,75,91,111,130], CT is considered an important evaluation tool.

Table 1 Summary of the characteristics of 166 cases of pneumoparotid (1941-2023), including the present case.

Characteristics
Age (years)	5-83
Mean	28.6
Percentage of children (%)	55.1
Percentage of men (%)	72.9
Chief symptom (%)
Swelling	92.9
Pain	36.9
Signs (%)
Crepitus	75.8
Frothy saliva	72.2
First consultation specialist (%)
Otolaryngologist	53.0
Dentists and oral and maxillofacial surgeons	13.3
ER doctors	10.8
Pediatricians	9.0
Etiology (%)
Self-induced	29.5
Idiopathic	21.7
Abnormal habit	13.9
Iatrogenic	11.4
Playing wind instruments	11.4
Blowing balloons	4.2

ER: Emergency room.

CONCLUSION

Most patients with pneumoparotid respond to conservative treatment; however, 10% of patients develop severe disease requiring surgery. Complications, such as subcutaneous emphysema, pneumomediastinum, and pneumothorax, may arise; consequently, local evaluation using US or radiography, along with comprehensive evaluations utilizing CT, is essential.