Use of 3D CT/MRI imaging in profound deafness
Imaging with CT or MRI is performed prior to cochlear implantation to evaluate the inner ear, facial nerve, cochleovestibular nerve, brain, and brainstem.
MRI may reveal hypoplasia or aplasia of the cochleovestibular nerve, whereas CT may show a narrow internal auditory canal or absence of the bony cochlear nerve canal at the modiolus.
Inner ear malformations ranging from the rare cases of cochlear aplasia to the more common enlarged vestibular aqueduct are easily visualized on CT or MRI. Such results may alter the choice of side of implantation.
Absence of the cochlea or the cochlear nerve can usually be confirmed with imaging and are absolute contraindications for cochlear implantation.
The cochlear implant is a surgically placed device that converts sound to an electrical signal. This electrical signal is transmitted via electrodes to the spiral ganglion cells in the cochlear modiolus.
Contra indication for Cochlear implant
Hearing Loss of Neural or Central Origin
Absence of Cochlea
Absence of VIIIth Nerve Development
Active Middle Ear Infections
3DCT scan is obtained to evaluate the status of the middle and inner cochlea and to establish the presence of a patent cochlea or to identify a common cavity, Mondini dysplasia, enlarged vestibular aqueduct, or an ossified cochlea. In some cases, an MRI is more useful than CT Scan when questions exist regarding the presence of the eighth nerve or severe ossification.
3D CT Images of a 2 year old child with Rudimentary Cochlea and hypoplasia of the semicircular canal:
(Courtesy Dr.Sangashil Jumle, consultant radiologist, Travancore Scans, Trivandrum, Kerala, India)
Radiologist report of the above findings: