Arachnoid Granulation Cerebrospinal Fluid Otorrhea

A case report and review of the temporal bone (TB) collection in the Department of Otolaryngology at SUNY Health Science Center in Syracuse demonstrated the occurrence of arachnoid granulations (AGs) in the posterior fossa surface of the TB and their role in cerebrospinal fluid (CSF) otorrhea. A large AG responsible for CSF otorrhea in a 64-year-old man was excised with soft tissue repair of the dural defect. Sixteen of 188 TBs (8.5%) in the collection contained 24 AGs ranging in size from 0.07 to 80.65 mm3. Nine AGs (37%) were small (less than 1 mm3) and did not demonstrate enlargement. Twelve (50%) were of intermediate size (2.50 to 9.32 mm3), and three (13%) were large (49.82 to 80.65 mm3). The intermediate and large AGs were associated with bone erosion and a high incidence of communication with a pneumatized mastoid complex (serous otitis media or meningitis). These findings suggest that AGs of sufficient size to produce bone erosion are the primary responsible lesions in adult-onset spontaneous CSF otorrhea.