**4. Candidacy and patient selection**

Selecting the right patient is the building block of a successful cochlear implantation. Therefore, a complete medical and audiologic workup is needed for evaluating candidacy of cochlear implantation and to make sure that the patient can tolerate anesthesia and surgical process. Patients are considered to take benefit from CI when they suffer from bilateral moderate to profound sensorineural hearing loss and when hearing aids cannot help them [24]. A combination of objective and subjective hearing tests is conducted to accurately identify the degree of hearing loss within audiometric frequencies. Currently available guidelines mention that children up to 2 years of age should have a bilateral profound sensorineural hearing loss, which is indicated by a pure tone audiometry (PTA) more than 90 dBHL for 500, 1000, and 2000 Hz frequencies, while patients older than 2 years of age should have bilateral sever to profound SNHL indicated by PTA more than 75 dBHL for 500, 1000, and 2000 Hz frequencies [25, 26]. Preoperative speech and language evaluation has the same importance for decision making regarding rehabilitation strategies and programs, as well as appropriateness of auditory performance, speech production, and mode of communication. Hearing loss is categorized to prelingual, postlingual, and perilingual types based on the time of onset. In prelingually deaf patients, hearing impairment occurs before gaining speaking skills, which is usually before 2 years of age, while it occurs after gaining complete speaking skills in postlingual patients which is usually after age of 5 years. In perilingual patients, hearing impairment occurs when some speaking skills are gained but are not completed usually between 2 and 5 years of age [16].

In addition, preoperative imaging and auditory testing are needed. Imaging modalities such as computed tomography (CT) scan, for assessing temporal bone, and magnetic resonance imaging (MRI), for evaluating brain anatomy and ruling out abnormalities of cochlear nerve, are conducted [15]. After scheduling patient for surgery, pneumococcal vaccines are administered according to FDA guidelines.

Current contraindications for cochlear implantation are two absolute and relative categories. Absence of cochlear development, deafness due to lesions of the central auditory pathway, and massive cochlear ossification that prevents electrode insertion are among absolute contraindications. Relative contraindications include aplasia of the acoustic nerve and medical conditions or developmental delays that would severely limit participation in aural rehabilitation.
