lunedì 8 febbraio 2010
Figure 1: Noncontrast head CT in brain window demonstrates no other abnormality.
Figure 2: Noncontrast head CT demonstrates small foci of gas within the right parotid gland. The parotid gland is otherwise normal without any definite inflammatory changes.
Pneumoparotid refers to air within the parotid gland without any demonstrable inflammation or infection. This is caused by reflux of intra-oral air into the parotid gland through Stenson’s duct. It is associated with any process that significantly increases intra-oral pressure. Intra-oral pressure must increase enough to overcome the small, slit like orifice of Stensen’s duct with surrounding redundant mucosal folds that normally prevent reflux of salvia and air into the duct and the parotid gland.
Iatrogenic causes, underlying medical conditions, occupational hazards and self-induced mechanisms have been reported. Iatrogenic causes include: dental instrumentation, general anesthesia with endotracheal intubation, spirometry. Pneumoparotid has been descibed with conditions associated with chronic cough including COPD, cystic fibrosis and allergic rhinitis. Additionally, wind instrument players, SCUBA divers and glass blowers can develop this condition. Finally, pneumoparotid has been reported to be self-induced to simulate mumps to avoid school or military duty and in children who obsessively puff their cheeks in response to psychological stress.
If intra-oral pressure increases adequately, often in the setting of chronic or recurrent cases, rupture of air through parotid acini and dissection into surrounding soft tissues including the retropharyngeal space, facial and neck soft tissues as well as pneumomediastinum can occur.
Pneumoparotid can be an incidental finding as in the current case or associated with unilateral or bilateral parotid swelling. The swelling is generally painless, however occasionally can be tender with associated mild warmth and erythema. Crepitus and air bubbles at Stensen’s duct with palpation may be observed at physical examination. Symptoms usually resolve spontaneously in a few days. Occasionally this process can be recurrent and lead to superimposed infection and/or inflammation secondary to reflux of oral bacteria and some authors recommend treatment with prophylactic antibiotics. Treatment also involves avoidance of further increases in intra-oral pressure. Surgery is indicated only in chronic and recurrent cases.