A case of the cytologically verified intrathecal dissemination of benign 
meningiomas was reported. A 36-year-old man was admitted to our hospital because 
trans-sphenoidal surgery was planned for the repair of CSF rhinorrhea caused by 
a recurrent pituitary adenoma. The CT scan demonstrated incidental multiple 
tumors spread throughout in the pontomedullary and ambient cisterns. The head 
and spinal MRI showed more than fifteen small tumors in the posterior fossa and 
the thoracic spinal canal. CSF cytology revealed benign fibroblastic or 
meningotheliomatous meningioma with whorl formation and psammoma body. Several 
comments were made on the mechanism of the intrathecal dissemination of the 
meningiomas.