Prevalence of occult cochlear basal turn patency

Perilymph gusher (PLG) is a rare complication of otologic surgery attributed to a communication between the cochlea and the internal auditory canal (IAC). Subtle patency between the cochlear basal turn and IAC has recently been identified on computed tomography (CT) as a risk factor, specifically when the defect is > 0.75 mm.

Investigate the prevalence of radiographic cochlear basal turn patency.

Patients with CT of the temporal bones and inner ears interpreted as "normal" were included. An otologist and a radiologist independently reviewed CTs to measure radiographic dehiscence in an oblique plane along the interface of the cochlea and IAC. Known PLGs were excluded.

Two hundred and ten ears were included (88 conductive or mixed hearing loss, 62 sensorineural hearing loss, 41 audiometrically normal ears). 71 ears (33.8%) were radiographically patent. Mean defect width was 0.41 mm (0.15-0.7 mm). Defect width was not associated with type of hearing loss, age, or gender. No defects were wider than 0.75 mm.

Radiographic patency of the cochlear basal turn may be present in patients with hearing loss and normal hearing, but patency > 0.75 mm (i.e. risk for PLG) is rare.