1. pediatric: usually presents with either meningitis or hearing loss
a) preserved labyrinthine function(hearing and balance): these usually present with meningitis.
3 usual routes of fistula:
● facial canal: can fistulize into middle ear
● petromastoid canal: along path of arterial supply to mucosa of mastoid air sinuses
● Hyrtl’s fissure (AKA tympanomeningeal fissure): links p-fossa to hypotympanum
b) anomalies of labyrinth (hearing loss):one of several types of Mundini dysplasias, usually presenting with rounded labyrinth/cochlea that permits CSF to erode through oval or round window into the auditory canal
2. adult: usually presents with conductive hearing loss with serous effusion, meningitis (often following an episode of otitis media), or cerebral abscess. This occurs most commonly through middle fossa. May be due to arachnoid granulations eroding into air sinus compartment