Gas in the cranium: an unusual case of delayed pneumocephalus following craniotomy.

We present the case history of a 23-year-old man who underwent frontal craniotomy followed by radiotherapy for a Grade III anaplastic glioma. Magnetic resonance imaging (MRI) at the 3-month follow-up showed significant tumour response. He became unwell some weeks after the MRI with an upper respiratory tract infection, severe headache and mild right-sided weakness. A computed tomographic (CT) scan showed a very large volume of intracranial gas, thought to have entered via a defect in the frontal air sinus after craniotomy and brought to light by blowing his nose. Intracranial air is frequently present after craniotomy, but it is normally absorbed within 34 weeks. The presence of pneumocephalus on a delayed postoperative CT scan should raise the possibility of a cerebrospinal fluid (CSF) fistula, or infection with a gas-forming organism. Many CSF fistulae require surgical closure in order to prevent potentially life-threatening central nervous system infection and tension pneumocephalitis. Immediate neurosurgical review is advisable.