The strength of the MRI is the visualization of the fluid content of the membraneous labyrinth (Fig. This pictorial review aims to provide a comprehensive overview of the most relevant pre-operative and post-operative imaging aspects in CI candidates intending to help radiologists and surgeons in routine practice.Įight different types of cochlear malformations can be differentiated by HRCT: (1) complete labyrinthine aplasia-Michel deformity (complete absence of cochlea, vestibule, vestibular aqueduct, and cochlear aqueduct), (2) cochlear aplasia (absence of the cochlea), (3) rudimentary otocyst (incomplete millimetric otic capsule remnant), (4) common cavity (cochlea and vestibule are represented by a single chamber), (5) incomplete partition of the cochlea (defect in the modiolus and the interscalar septa with three subtypes), (6) cochlear hypoplasia (cochlea with dimensions less than normal with four subtypes), (7) large vestibular aqueduct syndrome (enlarged vestibular aqueduct in the presence of normal cochlea, vestibule, and semicircular canals), and (8) cochlear aperture abnormalities (narrow cochlear nerve canal or internal auditory canal, possibility of an absent, or hypoplastic cochlear nerve). Post-operative imaging is important to confirm and document the intended electrode position and to demonstrate any scalar dislocation, cochlear dislocation, electrode fold, or malposition, which can be a possible source of CI malfunction. It allows the best insight into all relevant anatomical details and potential situations which preclude surgery or require modifying standard surgical approaches. Pre-operative imaging is essential to diagnose any type of inner ear malformations and to identify other abnormalities in the temporal bone that may be encountered. Radiologists play an essential role in the pre- and post-operative evaluation and selection of CI candidates. Acute infections such as otitis media and mastoiditis as well as chronic inflammation and cholesteatoma must be adequately controlled before CI surgery. For elderly patients, general health problems and life expectancy should be taken into account, and the indications for CI should be considered on a case by case basis. Disabilities including developmental delay, cerebral palsy, visual impairment, autism, and attention deficit disorder significantly affect the outcomes. In children with syndromic disorders such as CHARGE (congenital features of coloboma of the eye, heart defect, atresia of the nasal choanae, retardation of growth and/or development, genital and/or urinary abnormalities, and ear abnormalities and deafness), CI implant surgery is very challenging due to abnormal anatomy and comorbidity. Patients are less likely to benefit, but meaningful hearing can be achieved in selected cases. CI in cochlear nerve aplasia or hypoplasia is controversial. Ībsolute contraindications are complete labyrinthine aplasia, cochlear aplasia, and complete cochlear ossification. More recently, indications have been expanded to patients with single-sided deafness and ipsilateral vestibular schwannoma. In brief, current indications are (a) children (12–24 months) with profound SNHL (> 90 dB) and limited benefit from binaural amplification trial based on the meaningful auditory integration scale (b) children (2–17 years) with severe to profound SNHL (> 70 dB) with limited benefit from binaural amplification defined by ≤ 20–20% word recognition scores and (c) adults with moderate to profound SNHL in both ears (> 40 dB) with limited benefit from binaural amplification defined by ≤ 50% sentence recognition in the ear to be implanted (or ≤ 40% by centers for medicare and medicaid services criteria) and ≤ 60% in the contralateral ear or binaurally. Over the past few decades, CI surgery has increased and revolutionized the treatment of severe to profound sensorineural hearing loss (SNHL) in both children and adults. Straight lateral wall electrode arrays and pre-curved perimodiolar electrode arrays are available in different lengths for coverage of various cochlear duct lengths. The electrodes electrically stimulate the spiral ganglion cells along the cochlear turns, which then travel along the auditory nerve axons to the brain for sound perception. The receiver–stimulator converts the signal into rapid electrical impulses which are distributed to multiple electrodes on an electrode array implanted within the cochlea. A magnet held external transmitter sends the signal via electromagnetic induction through the skin to an internal receiver–stimulator. An external microphone and speech processor are worn behind the ear and convert sound into an electric signal. A cochlear implant (CI) is a surgically implanted device consisting of external and internal components.
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