⁃ Group 1: Prelinguistic hearing loss (birth-5 years; age at implantation of ABI 18 months-5 years)

⁃ • Pre-linguistic hearing loss (birth-5 yrs.; age at ABI 18 months-5yrs) with both:

• MRI +/- CT evidence of one of the following:

‣ Cochlear nerve deficiency

⁃ Cochlear aplasia or severe hypoplasia

⁃ Severe inner ear malformation

⁃ Post-meningitis ossification

• When a cochlea is present or patent, lack of significant benefit from CI despite consistent use (\>6 mo.)

‣ No or limited speech perception ability (limited to pattern perception on closed set testing materials using the CI)

⁃ Lack of progress in auditory skills development

⁃ Group 2: Post-linguistic hearing loss (\<21 yrs. of age)

• Post-linguistic hearing loss (\<21 yrs. of age) with:

‣ Loss or lack of benefit from appropriate CI without the possibility for revision or contralateral implantation. Examples might include:

• Post-meningitis ossification

∙ Bilateral temporal bone fractures with cochlear nerve avulsion

∙ Failed revision CI without benefit

⁃ Previously developed open set speech perception and auditory-oral language skills

• No medical contraindications

• Willing to receive the appropriate meningitis vaccinations

• No or limited cognitive/developmental delays.

• Strong family support

• Reasonable expectations from parents/guardians including a thorough understanding:

‣ of potential benefits and limitations of ABI

⁃ of parental role in rehabilitation

⁃ that the child may not develop spoken language as a primary communication mode or even sufficient spoken language to make significant academic progress in an aural/oral environment

• Involvement in a rehabilitation program that emphasizes development of auditory skills with or without the use of supplementary visual communication.

• Able to comply with study requirements including travel to investigation sites.

• Informed consent for the procedure from the child's parents/legal guardian.