Case 266.

History A 1-year-old boy was referred for cochlear implant assessment after he received a diagnosis of bilateral profound sensorineural hearing loss at neonatal hearing screening shortly after birth. The child was born at term via uneventful delivery, and there was no history of familial hearing loss or maternal illness. Tympanic membranes were normal, and hearing loss was confirmed with auditory brainstem testing, which showed no response from either ear. Hearing aids were provided from 3 months of age, but no behavioral responses were noted when these were worn. He was also noted to have some mild developmental delay throughout his 1st year of life and was slow to crawl, roll over, and stand up. Physical examination showed no syndromic features or physical abnormalities. Ophthalmology confirmed normal vision and visual movements but bilateral anesthetic corneas. He had corneal abrasions due to minor repeated corneal trauma, and left-sided tarsorraphy was performed at 6 months. Facial nerve function, swallow, and voice quality were normal. To assess suitability for a cochlear implant, the patient underwent MRI of the temporal lobe and brain ( Figs 1 - 4 ) and thin-section CT of the temporal bones ( Figs 5 , 6 ). The patient subsequently underwent left cochlear implantation. Figure 1: Sagittal midline T1-weighted 1.5-T MR image (repetition time msec/echo time msec, 541/15). Figure 2: Axial T2-weighted MR image (6703/116, 4-mm section thickness) at the level of the pontomesencephalic junction. Figure 3: Axial T2-weighted MR image one level inferior to that shown in Figure 2 . Figure 4a: (a) Axial 1.5-T single-slab three-dimensional (3D) turbo spin-echo MR image (1200/271) at the level of the right internal auditory canal. (b) Corresponding axial 1.5-T single-slab 3D turbo spin-echo MR image at the level of the left internal auditory canal. Figure 4b: (a) Axial 1.5-T single-slab three-dimensional (3D) turbo spin-echo MR image (1200/271) at the level of the right internal auditory canal. (b) Corresponding axial 1.5-T single-slab 3D turbo spin-echo MR image at the level of the left internal auditory canal. Figure 5: Unenhanced axial thin-section (0.7-mm section thickness) CT image of the temporal bone at the level of the internal auditory canals and middle cochlear turns. Figure 6: Unenhanced axial thin-section (0.7-mm section thickness) CT image of the temporal bone at a level slightly inferior to that shown in Figure 5 .