RESUMO
Pneumocephalus is collection of gas or air within the cranial cavity, commonly associated with trauma, cranial surgery, air embolism, open meningomyelocele; and rarely as a result of central nervous system infections. Asymptomatic pneumocephalus usually recovers spontaneously within few days. Untreated pneumocephalus can progress to tension pneumocephalus, manifesting as severe headache, dizziness, cranial nerve palsy, mental changes, seizure and disorientation. Herein, we report a rare case of pneumocephalus in a 9-month infant with subdural effusion following infection of nasal septum and otomastoiditis. There was no sign of meningitis but CThead showed communication of intracranial dura mater across widened foramen caecum with pre-nasal space, and bilateral otomastoiditis with erosion of anterior and lateral wall of right mastoid bone. The patient was treated successfully and discharged without sequelae.