CSF rhinorrhea due to a transsphenoidal approach usually follows accidental
or intentional arachnoid opening. We report a patient with an intrasellar
arachnoid cyst, who developed delayed onset of CSF rhinorrhea. A sixty-two-
year-old man presented with bitemporal type visual field defect for the las
t 3 years. With the diagnosis of arachnoid cyst or Rathke's cleft cyst, bas
ed on MRI findings of intra-and supra-sellar cyst with CSF intensity, he su
ccessfully underwent transsphenoidal surgery without evidence of intra-oper
ative CSF leakage. He developed CSF rhinorrhea one week later. This needed
another operation for sellar floor repair. The pathomechanism of this delay
ed onset is explained as follows. Incomplete or one-way communication of su
barachnoid space to cyst cavity, unrecognized during surgery, might cause d
elayed onset of CSF rhinorrhea. By using MRI, identification of the residua
l gland, which was compressed posteriorly, is useful for differentiating an
arachnoid cyst from other cystic lesions. In highly suspect cases, even wi
thout evidence of intra-operative CSF leakage, peri-operative measures to p
revent occurrence of postoperative CSF rhinorrhea are required.