BACKGROUND Cervical subcutaneous emphysema and pneumomediastinum are often secondary to trauma, surgery or infection. More rarely, they can be spontaneous with no identified cause, but forced Valsalva manoeuvres are a known predisposing factor. Any forced effort with a closed glottis, such as sneezing, can cause rupture of the mucosa leading to the formation of cervical subcutaneous emphysema and pneumomediastinum. METHODS The authors report the case of a 30-year-old man with cervical subcutaneous emphysema complicated by pneumomediastinum due to fistula of the piriform sinus following sneezing while simultaneously obstructing both nostrils. CONCLUSIONS Rupture of the mucosa of the piriform sinus is an extremely rare complication of this type of manoeuvre. This condition requires management in hospital due to the risk of infection with cervical cellulitis progressing to mediastinitis. Simultaneously obstructing both nostrils during sneezing is a dangerous manoeuvre that should be avoided.