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Transcript
COCHLEAR IMPLANTS BME 181 Brittany M. Alphonse Biomedical Engineering Table of Contents Definition and History of Cochlear Implants How Normal Hearing Works Reasons for a Cochlear Implant Parts of a Cochlear Implant How a Cochlear Implant Works Place Theory and Time Theory Implant Surgery Activation of Cochlear Implant Rehabilitation Life After Having a Cochlear Implant Definition and History of Cochlear Implants Definition: Small, complex electronic Composed of external and internal parts Directly stimulates the auditory nerve Improves hearing History: Research for device started in 1950s First commercial device approved in mid 1980s How Normal Hearing Works Outer ear Captures sound vibrations Sent to ear cannel then to middle ear Middle ear Vibration cause the bones to move Bones cause the fluid in Cochlea to move Fluid movement stimulates hair cells Hairs move back and forth sending electrical signals to auditory nerve Carried to the brain How Normal Hearing Works Continued Cochlea Snail shaped or curled tube in the part of the ear where the nerves are contained Gathers electrical signals from sound vibration Transmits to auditory nerve Reasons for a Cochlear Implant Hearing Aids only amplify sound Restore or regain ability to sense sound for those who have experience significant hearing loss Hearing loss due to infections of the ear Profound deafness Problems with the inner ear or cochlea Parts of the cochlea are not working the right way Auditory nerve isn’t stimulated Nerve deafness or sensorineural hearing loss Parts of a Cochlear Implant Implant Package Receiver and Stimulator Antenna Magnet Wire containing Electrodes Sound and Speech Processor Mini computer Microphone Transmitter How a Cochlear Implant Works Sound is Picked up by Microphone Amount of current determines loudness Converted into Electrical Signals by Sound and Speech Processor Position of Electrodes determines Pitch Signals received by Transmitter Implant Package determines how much current passes through to electrodes Nerve Endings in Cochlea Stimulated Message sent to brain Signals converted to hearing Place Theory and Time Theory Place Theory Cochlear responds better to a simple tone at one place along its length Sound is separated into groups Lower pitches Higher Pitches Use several channels and electrodes spaced out inside the cochlea Time Theory Ear Responds to timing of sound Sound signals are created into pulses Cochlea responds to different kinds of pulses Implant Surgery Under General Anesthesia (2-3 Hours) Incision behind the Ear Drills a 3-4 millimeter “bed” into Temporal Bone Opens the Mastoid Bone Access to Middle Ear Drills a small whole into Cochlea Implant Surgery Continued Threads wires of Electrodes into spirals of Cochlea Receiver is implanted in skull Implant Package is secured Incision is closed Most leave after surgery Activation of Cochlear Implant Fitting Audiologist attaches headset Align external magnet with the implanted Implant Check Information is communicated between implant and external speech processor Every electrode is checked All components are checked Activation of Cochlear Implant Continued Programming Speech Processor Electrodes are individually tuned for threshold and comfortable listening levels Electrodes Measure are turned on in small increments lowest and highest current for electrodes Matches sounds of different electrodes with different volumes to create a version of sound Creates Set a Hearing Map of instructions for each electrode on how to stimulate the nerve endings Rehabilitation Train brain to understand sounds Initially Programming sessions Obtain overwhelmed and Maintain optimal performance Listening Exercises Recognize different sounds Speech and Language Therapy Identify and interpret sounds Life After Having a Cochlear Implant Understand Speech without looking at speaker Understand Speech with Speech Reading Improved voice monitoring Improved speech reading Ability to hear soft sounds Success Rates: Auditory Memory Number of functioning Auditory Nerve Fibers in Cochlea How long been Deaf Ability to Speak before Hearing loss Age Continued therapy and programming sessions References for Pictures http://www.hearingclinic.net.au/mhc/content/the_ear. php http://universe-revie w.ca/I10-85-cochlea.jpg http://kidshealth.org/PageManager.jsp?dn=familydo ctor&lic=44&cat_id=192&article_set=34740&ps= 104# http://www.mayoclinic.org/cochlear-implants/ http://media3.washingtonpost.com/wpdyn/content/graphic/2008/04/11/GR20080411 02690.jpg