CSF gusher in cochlear implantation: The risk of missing CT evidence of a cochlear base defect in the presence of otherwise normal cochlear anatomy.

Intraoperative cerebrospinal fluid (CSF) leakages from the cochleostomy site - known as gushers - are a serious complication of cochlear implantation surgery in cases of congenital deafness. They occur as the result of abnormal communication between CSF in the internal auditory canal and perilymph in the cochlea. Gushers are well recognized as occurring in a proportion of cases in which there is a clearly visible congenital malformation of the cochlea. In this report, we describe two cases in which pre-operative computed tomography (CT) scanning of the cochlea was initially reported as normal but gushers occurred during cochlear implant surgery. In both cases, more detailed review of the CT scans (peroperatively in the first case, pre-operatively in the second case) showed a defect at the cochlear base, in the absence of any other cochlear malformation. The aim of this paper is to draw attention to the risk of missing this abnormality and to encourage careful inspection of the cochlear base on CT scans in all cases, even when the rest of the cochlear appears normal.