Spontaneous cerebrospinal fluid(CSF)otorrhea is less common than CSF leakage caused by trauma, and rarely occurs in adults. We report an adult case of CSF otorrhea. A 71-year-old woman with no traumatic or otologic history was hospitalized due to bacterial meningitis. After hospitalization, CSF leakage started suddenly from the left external ear canal. A high resolution CT scan with intrathecal administration of contrast material revealed CSF leakage in the left ear canal and multiple bone erosions in both the tegmen mastoideum and the posterior fossa aspect of the petrous bone. We performed closure and surgery via the middle fossa approach. We identified a bone defect in the tegmen mastoideum but could not detect any obvious abnormality in the dura mater. We placed both a pericranial flap and a free abdominal fat on the middle base of the skull as sealing materials. There was no recurrence of CSF otorrhea following surgery. In this surgery, the use of a multilayered closure technique is very important to avoid the recurrence of CSF leakage.