Cochlear implant: what the radiologist should know

Abstract

Cochlear implant is the method of choice in the treatment of deep sensorineural hypoacusis, particularly in patients where conventional amplification devices do not imply noticeable clinical improvement. Imaging findings are crucial in the indication or contraindication for such surgical procedure. In the assessment of the temporal bone, radiologists should be familiar with relative or absolute contraindication factors, as well as with factors that might significantly complicate the implantation. Some criteria such as cochlear nerve aplasia, labyrinthine and/or cochlear aplasia are still considered as absolute contraindications, in spite of studies bringing such criteria into question. Cochlear dysplasias constitute relative contraindications, among them labyrinthitis ossificans is highlighted. Other alterations may be mentioned as complicating agents in the temporal bone assessment, namely, hypoplasia of the mastoid process, aberrant facial nerve, otomastoiditis, otosclerosis, dehiscent jugular bulb, enlarged endolymphatic duct and sac. The experienced radiologist assumes an important role in the evaluation of this condition. Keywords: Cochlear aplasia; Labyrinthine aplasia; Sensorineural hypoacusis; Cochlear implant; Computed tomography.O implante coclear é o método de escolha no tratamento da hipoacusia neurossensorial profunda, notadamente nos pacientes em que os aparelhos de amplificação convencionais não implicam melhora clínica notável. Achados de imagem são fatores decisórios na indicação ou contraindicação desse procedimento cirúrgico. Os fatores que contraindicam absoluta ou relativamente, assim como os que podem complicar de forma significativa o implante, devem ser familiares aos radiologistas na avaliação do osso temporal. Alguns critérios ainda são considerados contraindicações absolutas, como a aplasia do nervo coclear, a aplasia da cóclea e/ou labiríntica, apesar de já existirem relatos que questionam ou contradizem esses dois últimos. As contraindicações relativas são as displasias cocleares, destacando a labirintite ossificante. Outros achados podem ser citados como agentes complicadores na avaliação temporal, tais como hipoplasia do processo mastoideo, nervo facial aberrante, otomastoidite, otosclerose, deiscência do bulbo da jugular, alargamento dos ductos e saco endolinfático. O radiologista experiente na avaliação do osso temporal assume papel de destaque no curso dessa doença. Unitermos: Aplasia coclear; Aplasia labiríntica; Hipoacusia neurossensorial; Implante coclear; Tomografia computadorizada. Abstract DISCUSSIONCochlear implant consists in the subcutaneous implantation of a receptor behind the ear and a cochlear electrode passing through the mastoid cavity, which directly stimulates the acoustic nerve. The receptor sends a signal to the electrode implanted at the basal coil of the cochlea. Such signal is transformed into an electrical stimulation which propagates throughout the remaining auditory pathways until reaching the auditory cortex of the temporal lobe ing factors in the ind...

Radiological spectrum of temporal bone, inner ear and brain parenchymal abnormalities in the preoperative cross-sectional imaging of sensorineural hearing loss in cochlear implant candidates: A prospective study

“…Dilated vestibular aqueduct Mondini and Mondini variants NA/28.4% Johannes P Westerhof et al [2] (2001)…”

“…The problem of hearing loss assumes significance not only from a vocational or economic but also psychological perspective [1] Advances have led to the increasing use of cochlear implantation in subjects with sensorineural hearing loss especially when conventional amplification devices fail to give any benefit [2] . Sensorineural hearing loss can result from a constellation of abnormalities that may involve the labyrinth, internal auditory canal, CPA (cerebellopontine angle), brain stem, or auditory pathways.…”