The parotid glands should be impalpable in children. Noticeable facial asymmetry and unilateral or bilateral oedema are usually associated with parotid pathology. The most common causes include infection, autoimmune or lymphoproliferative diseases, duct obstruction, as well as benign or malignant tumours. Rapidly growing oedema is a typical outcome of viral infection or chronic, recurrent parotitis.

The term “pneumoparotid” refers to the presence of air in either the parotid gland or the Stensen’s duct (1, 2). Pneumoparotiditis is a parotitis secondary to a retrograde pathogen invasion through the duct orifice, which is dilated as a result of barotrauma (3). The presence of pneumoparotid in the absence of pneumoparotiditis is unlikely due to the diversity of oral flora. The co-existence of secondary inflammatory oedema often leads to a misdiagnosis of simple parotitis.

Patients at risk of pneumoparotitis include wind instrument players and adults with mental disorders (4, 5). Most patients are aware of their ability to inflate the gland. Patients with unintentional parotid gland inflation pose a greater diagnostic challenge.

A 12.5-year-old boy was admitted in an emergency to the Department of Paediatric Otolaryngology, Medical University of Warsaw, due to a swelling in the right cheek. About 1.5 days earlier, he completed a 7-day course of oral clindamycin for parotitis. The diagnosis and the treatment were suggested in the Department of Otolaryngology of another centre, where the patient had stayed for 5 days prior to outpatient treatment. At that time, salivary gland ultrasound showed inflammation of the gland and a cyst in the mandibular angle. Head CT was performed (fig. 1, 2).

The findings were as follows: “A 23 mm space filled with air in the right parotid region, below the external auditory canal, in the projection of the salivary gland; air is also present in the salivary ducts of the right parotid gland and the parotid duct. On the left, air is present in the parotid duct and salivary ducts within the gland. Cervical lymphadenopathy up to 21 mm. Positive intra-oral pressure causes dilation of both the salivary ducts and the right-sided gas-filled space. The CT image most likely corresponds to a cyst drained through a fistula to salivary ducts, with a leaking orifice and air reflux into the salivary glands”. Buccal oedema located directly under the right ear lobe again increased rapidly, causing moderate pain in the child. Inflammatory markers on admission were normal: CRP < 0.5, WBC 8.59 thous., LYMF 34.3% (N: 24.7-56.0%), NEUT 56.3% (N: 43-65%), MONO 6.6% (N: 4.4-12.3), EOSINO 2.4% (N: 0.0-4.4%). Body temperature was 36.6°C. Otolaryngological examination showed no evacuation of pathological content from the dilated orifice of the gland, but only normal secretion containing air bubbles. Emergency ultrasound findings were as follows: “Both parotid glands are not enlarged, but show inhomogeneous parenchymal echostructure, without any focal lesions. A slight amount of air in the left parotid duct; a large amount of air and a small amount of fluid (about 6-5 cm) in the right parotid gland. Slightly increased vascularity in the right parotid gland. Mild reactive lymphadenopathy up to approx. 24 x 7 mm at both submandibular areas. No oedema of the surrounding tissue”. Based on the clinical picture and medical history, IV Amoxiclav was included by the doctor on duty. The boy admitted that during the past months he “played” by inflating both parotid glands. Initially, the dilation of the distal end of the duct was unnoticeable, and the resistance during gland insufflation was high. With time, however, the boy was able to develop a 27-mm-long pneumatocele. He also reported that he derived much joy from the “bubbling sensation” during air evacuation.

According to the patient’s mother, the boy had a history of 2 episodes of right-sided parotitis. Purulent discharge from the Stensen’s duct was observed each time. Both infections were developed in the last 6 months.

At the time of admission, the patient was under outpatient immunological, gastroenterological and cardiological care. He complained of a few-minute episodes of intra-abdominal pain unrelated to food ingestion for several years. His mother confirmed the lack of appetite, extended chewing time and difficulties swallowing solid foods. Percentile charts were difficult to develop due to the lack of measurements. At examination, the boy’s body weight of 31 kg corresponded to the third percentile (25^th percentile at 5 years old), and his height of 149 cm corresponded to the 25^th percentile (27^th at 5 years old). The mother reported recurrent URTIs, allergy (no allergen test or treatment), gastroesophageal reflux disease (no medical records or treatment) and excluded celiac disease (again no records). Family history additionally revealed that the boy’s father was diagnosed with and treated for Barrett’s oesophagus.

Laboratory tests were run at the Department to evaluate total IgE, serum and urine amylase, anti-TPO, TSH, ANA, ANCA, Ig A, Ig M, Ig G, EBV, CMV, RF, CRP, and complete blood cell count. Abnormal findings were reported for total IgE ? 163 kU/L (N: 0-100). The above mentioned ultrasound was performed.

The patient was qualified for bilateral sialography. The procedure was performed under local anaesthesia: “Contrast agent (Imeron) was administered through a catheter inserted into the right parotid duct ? the dilated parotid duct was filled; several smaller spaces in the distal part of the duct and one significantly larger space were also filled. Contrast agent evacuation from these spaces was spontaneous (fig. 3). This was followed by contrast agent (Imeron) administration through a catheter inserted into the left parotid duct ? the parotid duct, which gave off branches in its distal dilated part, was filled with contrast agent (fig. 4)”.

A decision was made during the examination to qualify the patient for intraductal administration of dexamethasone. Bilateral irrigations were performed every day until the child declared distension-related pain. Treatment outcomes were monitored based on salivary gland ultrasonography and the decreasing volumes of drug that could be introduced without tissue resistance. Initially, 5 and 3 mL of solution were introduced into the right and the left duct, respectively. The treatment was completed after 6 days, when the radiologist reported a non-dilated right parotid duct (1.5 mL for the right and 0.5 mL for the left side) (fig. 5).

Ultrasound findings were as follows: “Both parotid glands of normal size, but showing inhomogeneous, abnormal parenchymal echostructure (more pronounced in the right gland), with no focal lesions. A lesion filled with air, 5 mm in diameter, and a duct (about 9 mm in length) filled with air, running from the ear lobe to the upper pole of the parotid gland, are present subcutaneously, near the upper pole of the right parotid gland. The parotid duct is not dilated. No parotid gland inflammation was detected. Minor reactive lymphadenopathy is present at both submandibular areas, more pronounced on the right side, up to about 21 mm, compared to the left side (14 mm). Periparotid tissues unremarkable. Submandibular salivary glands and the thyroid are normal”.

In cooperation with the doctors in the Department of Gastroenterology, the patient was qualified for gastroscopy with oesophageal biopsy to exclude eosinophilic esophagitis (EoE). Normal macroscopic and histopathological findings were obtained.

The 12-year-old boy was discharged the following day, instructed to follow intensive oral hygiene routine and incorporate acidic products in the diet. The boy was instructed to avoid intentional parotid insufflation, chewing gums, whistling and playing wind instruments. A 3-month follow-up showed no increase in the size of pneumatocele or episodes of parotitis.

The following terms are used in literature to refer to the presence of air in the parotid gland: pneumoparotitis (6), pneumoparotiditis (7, 8), pneumosialoadenitis (9), surgical mumps or anaesthesia mumps (10), and pneumatocele glandulae parotis (11-13). Currently, the term pneumoparotitis is increasingly used, which does not indicate inflammation of the gland as opposed to pneumoparotiditis.

Pneumoparotid may be occupational or self-induced. Regardless of the aetiology, the condition is a consequence of increased intra-oral pressure and retrograde air flow into the Stensen’s duct and gland lobules. It may be either unilateral (11, 14, 15) or bilateral (5, 6, 16) ? often asymmetric, which was the case of our patient.

Self-induced cases of the disease among both children and adults are most common in literature (5, 6, 11, 12, 14, 15, 17-19). The problem usually occurs in the context of psychological and psychiatric disorders (4, 5, 20), traumatic events (22), nervous tics (14, 21), and a way to avoid school (5, 14) or even imprisonment (2). Cases of pneumoparotitis due to aggressive nose blowing (23), following spirometry (24), and sneezing with a blocked nose due to allergic rhinitis (25) have been described.

Under physiological conditions, the parotid gland is protected against retrograde invasion of pathogens, saliva or air by a system of mucosal folds covering the orifice, a slit-like shape of the orifice itself, the diameter of which is smaller than that of the Stensen’s duct, and a mechanism responsible for closing the orifice of the duct in response to increasing intra-oral pressure. The mechanism involves increasing duct angulation by compressing the anterior edge of the masseter muscle with the cheek stretched and a simultaneous closure of the orifice by the buccinator (5, 6, 14, 20). Therefore, an increase in the intra-oral pressure above typical values, i.e. 2-3 mmHg (up to 150 mmHg in trumpet players (26)), buccinator hypotonia, masseter hypertrophy, deposits in the Stensen’s duct impairing salivary flow, and dilated orifice (6, 14) promote pneumoparotid and pneumoparotiditis.

Pneumoparotitis most often manifests as salivary gland oedema with crepitation on palpation (3, 4). Foamy or purulent discharge from one or both parotid duct orifices may be observed (3, 4). Air bubbles coming from the duct are often observed during buccal palpation, which was also the case of our patient (3, 11, 12, 14). The skin over the gland may be warm and flushed. The tissue surrounding the gland does not have to be painful on palpation (27). Subcutaneous emphysema of the face and neck (3, 11, 21) and even pneumothorax (3, 5, 11, 28, 29) have been described in extreme cases. Sudden onset and short duration are typical of the disease (3, 18, 29). Additional history of blowing balloons, playing wind instruments or nervous ticks helps make the correct diagnosis. Computed tomography, which clearly differentiates between air and deposits/calculus in the Stensen’s duct, is the gold diagnostic standard (3, 4, 16). Recent research indicates that the imaging should be performed in a patient with inflated cheeks to increase sensitivity (3, 16). Ultrasonography may be performed as a preliminary study, especially in paediatric patients (3, 16, 29). Sialography usually shows a dilated Stensen’s duct (29, 30); if chronic, recurrent pneumoparotitis is present, ductal dilatation and characteristic “sausaging” may be observed (29, 30).

The treatment involves both conservative and surgical methods. Anti-inflammatory treatment and antibiotic therapy to prevent bacterial superinfection are sufficient for mild lesions. Psychologist or psychiatrist support may be needed to change unhealthy habits (5, 6, 14). Cheek compressors may be used in patients at an occupational risk of increased intra-oral pressure (3, 11, 19, 29).

Due to the short interval between recurrences in our patient, a decision was made to perform dexamethasone irrigation of the Stensen’s duct immediately after sialography and during the several days of in-patient follow-up. The aim of such management is to remove deposits, suppress inflammation and shrink the parotid duct (31-36). Ligation of the Stensen’s duct is the first-line surgical procedure. Parotidectomy is reserved for patients with high recurrence rates (2, 3, 4, 19).

Although pneumoparotitis is a rare entity, it should be included in the differential diagnosis of recurrent parotitis. Parotid ultrasonography is a commonly used diagnostic method in the paediatric population due to the typical clinical picture facilitating the diagnosis, wide availability and relatively low costs. Sialography irrigation of the duct with steroid solution may be considered in the prevention of recurrent inflammation in the pneumatocele. Patient’s cooperation is needed to eliminate the habit of self-insufflation. It should be noted that most patients require conservative treatment, and surgery should be used in the case of previous treatment failure.