Radiographic diagnosis of trans-stapedial cerebrospinal fluid fistula

OBJECTIVE: To report the high-resolution computed tomography and magnetic resonance imaging (MRI) findings of a bulging oval window in children with recurrent meningitis and congenital cerebrospinal fluid fistula. STUDY DESIGN: Case series. SETTING: Academic medical center children's hospital. SUBJECTS AND METHODS: A series of eight ears in four children with profound, bilateral sensorineural hearing loss and perilymphatic hydrops were evaluated. Two patients presented with recurrent meningitis. All children were assessed with highresolution computed tomography, and two children also underwent MRI. RESULTS: Seven of eight ears had a common cavity malformation. The vestibular compartment showed severe dysplasia (n = 5), moderate dysplasia (n = 1), or a single semicircular canal (n = 2). The lamina cribrosa was clearly absent in four of eight ears. Its presence was difficult to assess in ears with small internal auditory canals. A bulging oval window, present in six of eight ears, was defined as a fluid density on high-resolution computed tomography or a hyperintense mass demonstrated by T2-weighted MRI protruding from the vestibule into the middle ear cavity. When present, this herniation of a fluid-filled sac could be seen on both MRI and computed tomography. This imaging finding was surgically confirmed in two patients. CONCLUSION: The bulging oval window, which represents a fluid-filled sac, can be identified by both high-resolution computed tomography and MRI. Communication between the middle ear and the subarachnoid space through the inner ear is an important etiology for recurrent meningitis in children with sensorineural hearing loss.