Iatrogenic pneumoparotid secondary to biopsy of buccal mucosal tumour

A 44-year-old male patient came for contrast-enhanced CT face and neck to evaluate biopsy-proven squamous cell carcinoma of right cheek. There was an ill-defined patch of leukoplakia in the right buccal mucosa with crepitus over the right preauricular and parotid regions on oral examination. Since biopsy, patient has had dull pain in right preauricular area. 

Contrast-enhanced CT face and neck with a puffed cheek protocol demonstrated heterogeneously enhancing irregular thickening of right buccal mucosa without evidence of bony erosion or skin invasion [Figure 1(a)]. There was a mildly swollen right parotid gland without adjacent fat stranding. There was no evidence of abnormal enhancement in the parotid gland or other inflammation signs. There was evidence of air within the entire Stenson's duct of the right parotid gland from its opening within the glandular parenchyma up to the level of the buccinator muscle [Figure 1(b, c)]. There was no free air in the glandular parenchyma. The left parotid, bilateral submandibular and sublingual glands appeared unremarkable. There was no evidence of air in the left Stenson's duct. There was no proof of sialolithiasis in any of the salivary glands. 

Background

The pneumoparotid word, coined by Hertel in 1865, refers to the presence of air within the parotid system, including the gland, the Stenson’s duct or both. This may result in unilateral or bilateral salivary gland enlargement. The words pneumoparotid, pneumoparotiditis, pneumoparotitis, and wind parotitis are all used to describe this condition in the literature [1].

Pneumoparotid is associated with increased intraoral pressure and retrograde airflow into Stenson's duct as in glassblowing and trumpet playing [2]. Psychological illnesses such as nervous tics have also been reported as causative factors [3]. Gazia et al reported self-induction by puffing the cheeks as the most frequent aetiology. Other causes include dental instrumentation and positive pressure ventilation during anaesthesia. Pneumoparotid can also be caused by CT imaging for buccal cancer using the puff cheek approach, which case it is usually bilateral and symmetrical in distribution [4]. We present a case of iatrogenic pneumoparotid secondary to buccal mucosal tumour biopsy. Since the biopsy, the patient has had continued discomfort and dull pain in the right preauricular region.

Clinical perspective

Variable degree of glandular enlargement and palpable crepitus are common symptoms, as seen in our patient [5]. The parotid gland may be painless or painful with overlaying warmth, erythema, discomfort and soreness. Usually, one or both of Stenson's ducts may produce frothy saliva or purulence, which was not seen in our case. Air may burst through the parotid acini and enter the parapharygeal region, extending into the face and neck, causing subcutaneous emphysema [6,7]. In extreme cases, life-threatening conditions such as pneumothorax and pneumomediastinum may develop [8].

Imaging perspective

Ultrasonography is the first imaging technique for detecting air pockets within the parotid gland and Stenson’s duct. CT is the gold standard for definitive confirmation. The absence of inflammation and a sialolith add credibility to the diagnosis [9–11]. A thorough clinical history and detailed physical examination are crucial to diagnosis. 

Outcome

Warm compressions help to self-limit the condition. With or without antibiotics and steroidal anti-inflammatories, medical therapy is the most prevalent form of treatment. Antibiotics are used to keep suppurative parotitis at bay. Behavioural therapy helps to overcome bad oral habits. In rare instances, surgical techniques such as parotidectomy or duct ligation are employed [2,12]. 

Unilateral air-filled right Stenson’s duct, pain over the right preauricular region, and a recent biopsy favoured iatrogenic pneumoparotid in our patient. There was presumed injury to the parotid ampulla where the Stensen's duct opens in the vestibule of mouth next to second maxillary molar tooth. Pressure dressing was applied in the outpatient department. The patient responded well to the conservative therapy with uneventful recovery. Meanwhile, he was referred to the maxillofacial tumour board to manage the buccal mucosal tumour.

Written informed patient consent for publication has been obtained.

Take-Home Message / Teaching Points

1. Detailed clinical and occupational history plays a crucial role in diagnosis.  
2. History of personal habits like manipulation of the oral cavity and balloon blowing is also important.

CT scan exquisitely elaborates the whole course of Stenson’s duct, from its origin within the parotid gland to parotid ampulla and intraoral orifice.

Conclusion

Pneumoparotid is a very uncommon condition that affects the parotid glands. Increased intraoral pressure has been identified as a contributing factor. In our case, pneumoparotid developed as a consequence of buccal mucosal biopsy. Avoiding the triggering source, pressure dressings, and massage over the parotid area are all part of the treatment plan. In extreme circumstances, surgical intervention may be required. The illness is often self-limiting, with minimal long-term consequences on the parotid gland and a good response to symptomatic conservative treatment.