Iatrogenic arachnoid cyst with distinct clinical picture as a result of bone defect in the floor of the middle cranial fossa: case report

OBJECTIVE AND IMPORTANCE: This kind of arachnoid cyst has not previously been described as a complication of a cranial base bone defect. Recognition of this rare complication may be delayed, because clinicians are unaware of its possibility. CLINICAL PRESENTATION: A 22-year-old man presented with severe headache and increasing difficulty in breathing and swallowing. A physical examination revealed a pulsatile mass in the oral cavity, arising from the parapharyngeal area. A cystic mass that protruded into the oral cavity, through a dural and bony defect in the left middle fossa, was detected on neuroimages. INTERVENTION: A left frontotemporal craniotomy was made, and the cyst was decompressed. Duraplasty was performed with lyophilized dura. The bone defect was managed with a calvarial free bone graft and a pedicled myofacial flap. Serial neuroimaging studies performed postoperatively showed that the cyst had decreased in size. CONCLUSION: This report describes an unusual complication of a cranial base bone defect. Although not all bone defects in the cranial base require reconstruction, management of the large bone defect, particularly in the middle fossa, should preferably be accomplished with the help of a bone graft to support the dural graft.