Background: Pneumocephalus after posterior fossa craniotomy is very common. However, cranial nerve dysfunction secondary to pneumocephalus is a very rare phenomenon.
Patient presentation: This case reports a patient who suffers from Chiari I malformation with syringomyelia in cervical spinal cord and develops unilateral oculomotor nerve palsy after atlanto-occipital decompression with dural plasty.
Conclusions: Cranial nerve dysfunction caused by pneumocephalus after craniotomy is rare and easily misdiagnosed. Timely head computed tomography or magnetic resonance imaging examination can exclude other causes and reveal the anatomic sites of pneumocephalus. Conservative treatment is available in most patients while sometimes it is necessary to drain the air.