BME 215 Biomaterials and Artificial Organs Class Project Fall 2008

1. Cochlear Implants: a tutorial Hi! I’m Marvin and I want to learn more! Seth Brown Danaan Metge Rae Luan Megan Toney Click here to begin! BME 215 Biomaterials and Artificial Organs Class Project Fall 2008

2. How to navigate the lesson Use your mouse to navigate through the pages Click on the HOME button to return to the Navigation Screen Click on the RIGHT ARROW to go to the next slide Click on the LEFT ARROW to return to the previous slide Click on the U-TURN to return to the slide LAST VIEWED Click on the i to learn MORE INFORMATION about a certain subject Click on the links at the bottom of the page to trace your history Section >> Sub-section

3. Click on a topic to learn more! Ear Anatomy and Disease State Materials and Manufacture Cochlear Implant Surgery Post Operation--Rehabilitation Performance and Failure Modes Controversy Acknowledgements & References

4. Click on a topic to learn more! Ear Anatomy and Disease State Ear Anatomy Sensorineural Hearing Loss Materials and Manufacture Patient Selection Cochlear Implant Surgery Section Review Post Operation--Rehabilitation Performance and Failure Modes Controversy Acknowledgements & References

5. Click on a topic to learn more! Ear Anatomy and Disease State Materials and Manufacture External Components Internal Components Cochlear Implant Surgery Implant Sterilization Section Review Post Operation--Rehabilitation Performance and Failure Modes Controversy Acknowledgements & References

6. Click on a topic to learn more! Ear Anatomy and Disease State Materials and Manufacture Cochlear Implant Surgery Overview Procedure Post Operation--Rehabilitation Risks Tools Performance and Failure Modes Section Review Controversy Acknowledgements & References

7. Click on a topic to learn more! Ear Anatomy and Disease State Materials and Manufacture Cochlear Implant Surgery Post Operation--Rehabilitation Post Operation Rehabilitation Therapy Performance and Failure Modes Section Review Controversy Acknowledgements & References

8. Click on a topic to learn more! Ear Anatomy and Disease State Materials and Manufacture Cochlear Implant Surgery Post Operation--Rehabilitation How a CI works Overview Performance and Failure Modes Performance Complications and Failure Controversy Section Review Acknowledgements & References

9. Click on a topic to learn more! Ear Anatomy and Disease State Materials and Manufacture Cochlear Implant Surgery Post Operation--Rehabilitation Performance and Failure Modes Arguments Against CI Controversy Controversy Today Acknowledgements & References

10. Click on a topic to learn more! Ear Anatomy and Disease State Materials and Manufacture Cochlear Implant Surgery Post Operation--Rehabilitation Performance and Failure Modes Controversy Acknowledgements & References

11. Ear Anatomy and Disease State Ear Anatomy and Function Sensoineural Hearing Loss Click on a section or click Begin Lesson! Patient Selection Ear Anatomy and Disease State Begin Lesson Lesson Review

12. Human ear slide 1 The human ear consists of three major sections: • outer ear • middle ear • inner ear http://www.apps.hearingworld.co.uk/learn_about_hearing_loss.html Ear Anatomy and Disease State >> Ear Anatomy

13. Human ear slide 2 The outer ear consists of: • the pinna, or • external ear lobe • the ear canal http://www.apps.hearingworld.co.uk/learn_about_hearing_loss.html Ear Anatomy and Disease State >> Ear Anatomy Next

14. The middle ear consists of: • the tympanic • membrane, • known more • commonly as • the eardrum • the earbones • (ossicles) • malleus • incus • stapes http://www.apps.hearingworld.co.uk/learn_about_hearing_loss.html Ear Anatomy and Disease State >> Ear Anatomy

15. The inner ear consists of: • the cochlea • the cochlea connects to the auditory nerve So how do our ears hear? http://www.apps.hearingworld.co.uk/learn_about_hearing_loss.html Ear Anatomy and Disease State >> Ear Anatomy

16. What is sound? Sound is caused by vibrations pressure • When an object vibrates, it causes movement in air particles time The pressure waves that arise from the movement of air particles travel through the air and other fluid mediums so our ears can detect them Ear Anatomy and Disease State >> What is Sound?

17. Frequency Frequency is the measure of oscillations per second and is measured in Hertz (cycles/second) 1 oscillation Higher frequency signals have more oscillations that a low frequency signal in the same amount of time High frequency Low frequency 1 second 1 second Ear Anatomy and Disease State >> What is Sound?

18. Frequency Words are characterized by specific frequency spectra with sounds ranging from 125Hz for a deep male voice to 7,000 or 8,000 Hz for the hissing sound of the letter ‘s’ So when you listen to someone speaking you decode their words based on the different frequencies of each phonetic pronunciation http://www.daniellongstreet.com/AM_Speech/AMspeechsignal.html#2 Ear Anatomy and Disease State What is Sound? >>

19. Decibels Decibels (dB) is a logarithmic measure of the power For oscillatory sounds: where A is amplitude Prolonged exposure to sounds over 90 decibels can lead to eventual hearing loss OW! http://www.acme-rents.com/Pages/matrix.html Ear Anatomy and Disease State What is Sound? >>

20. The outer ear collects sound in the environment and guides the pressure waves down the ear canal, where they cause the eardrum to vibrate. http://www.apps.hearingworld.co.uk/learn_about_hearing_loss.html Ear Anatomy and Disease State >> Ear Function

21. Ossicles The malleus (hammer) is embedded in the eardrum The end of the stapes inserts into the oval window of the cochlea so it can transfer the vibrations in the eardrum to the incus (anvil) and passes these vibrations to the inner ear (specifically the scala vestibuli and the scala tympani of the cochlea) which in turn passes the vibrations to the stapes (stirrup). http://www.britannica.com/EBchecked/topic/175622/ear Ear Anatomy and Disease State >> Ear Function

22. The Cochlea (cross section) • Vibrations in the stapes cause pressure waves in the interstitial fluid of the scala vestibuli and the scala tympani. • Fluctuations in this fluid cause the Reissner’s and basilar membranes to vibrate and force pressure waves in the cochlear duct. • The resulting motion of the tectorial membrane against the organ of Corti cause displacement of the stereocilia. Visit this website for a detailed animation of cochlear movement http://www.britannica.com/EBchecked/topic/175622/ear Ear Anatomy and Disease State >> Ear Function

23. The Cochlea • Because the base of the cochlea is stiffer than the apex, different positions along the length of the cochlea respond differently to a particular stimuli • The bends in the cochlea are tuned to different frequencies and generate different electrical responses, allowing us to differentiate between varying frequencies and sounds. • This spatial coding of frequency is called tonotophy http://www.britannica.com/EBchecked/topic/175622/ear Ear Anatomy and Disease State >> Ear Function

24. Hair Cells • Stereocilia are the “hair” of the hair cells. • Movement of the tectorial membrane against the basilar membrane causes motion in the stereocilia. • The physical displacement of the stereocilia triggers an action potential in the auditory nerve. http://www.britannica.com/EBchecked/topic/175622/ear http://www.britannica.com/EBchecked/topic/175622/ear Visit this website for a detailed animation of hair cell activation Ear Anatomy and Disease State >> Ear Function

25. Auditory Nerve Movement of the stereocilia trigger action potentials in the auditory nerve… which transports these electrical impulses to the brain… where they are processed and interpreted as sound! http://www.crh.noaa.gov/lmk/?n=lightning_safety This interface between auditory nerve fibers and each individual hair cell must be intact for a cochlear implant to be an effective form of treatment So what can go wrong? Ear Anatomy and Disease State >> Ear Function

26. Sensorineural Hearing Loss What is it? Genetic Causes Aging Noise and Traumatic Injury Ototoxicity Disease http://www.hearinglife.com.au/about_loss.cfm Disease is an important causal factor in children Ear Anatomy and Disease State Sensorineural Hearing Loss Begin Section >>

27. Occurs in the inner ear when the hair cells within the cochlea are damaged but other auditory structures remain functional. The potential for hearing remains because the auditory nerve is still intact and able to transmit electrical impulses to the brain if properly stimulated. What is Sensorineural Hearing Loss? ? ? ? ? ? How does this type of hearing loss occur? Ear Anatomy and Disease State Sensorineural Hearing Loss What is Sensorineural Hearing Loss? >> >>

28. Genetic Causes • More than 24,000 children are born with congenital hearing loss in the US each year1 • Mistakes in the genetic code can result in ear anatomy that is not formed correctly and as a result does not collect and interpret sound normally While some are born with hearing loss, it can occur at any time of life http://www.frequencyawareness.com/dna_activation.html Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Genetic Causes

29. Aging (Presbycusis) At birth, a normal human ear contains about 15,000 hair cells that degenerate steadily throughout life 4 basic types: Sensory: hair cells of organ of Corti degenerate first Neural: cochlear neurons degenerate first Strial/metabolic: atrophy of the stria vascularis Mechanical/inner ear conductive: thickening of basilar membrane Older individuals are often favorable candidates for cochlear implant selection because they have preexisting speech abilities http://www.offthemark.com/search-results/key/hearing+loss/ http://news.softpedia.com/news/Vision-and-Hearing-Loss-Linked-in-Old-Age-37611.shtml Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Aging

30. Aging (Presbycusis) • Older individuals can be favorable candidates for cochlear implant selection because they have preexisting speech abilities • learning to use the implant after surgery can be much easier and can lead to a huge improvement in quality of life • However, degeneration of the auditory nerve can undermine the effectiveness of a cochlear implant http://www.offthemark.com/search-results/key/hearing+loss/ http://news.softpedia.com/news/Vision-and-Hearing-Loss-Linked-in-Old-Age-37611.shtml Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Aging

31. Noise and Traumatic Injury • Exposure to noise is the second most common cause of all levels of hearing impairment • The level of hearing loss is dependent on the duration and intensity of the sound causing the loss • Can be bilateral (in both ears) or unilateral (in one ear) depending on the type of exposure Traffic could cause hearing loss due to prolonged exposure While hearing loss associated with firearm use is often unilateral and from one time exposure http://www.orlandhearingaids.com/hearing_info/?i=Protecting%20Your%20Hearing http://www.bowhunting.net/artman/publish/HUNT_DOCTORS_81/Hearing_Loss.shtml Ear Anatomy and Disease State Sensorineural Hearing Loss Noise and Traumatic Injury >> >>

32. Noise and Traumatic Injury • Hearing loss due to noise can be temporary or permanent • Cochlear implants are applicable for permanent loss presenting as a threshold shift • Hearing loss due to noise exposure is usually characterized by a loss of the sensitive hair cells followed by degeneration of the auditory nerve • Workplace guidelines have been established to protect workers constantly exposed to high decibel noises7 http://www.orlandhearingaids.com/hearing_info/?i=Protecting%20Your%20Hearing http://www.bowhunting.net/artman/publish/HUNT_DOCTORS_81/Hearing_Loss.shtml Ear Anatomy and Disease State Sensorineural Hearing Loss Noise and Traumatic Injury >> >>

33. Ototoxicity • Hearing loss can be the result of adverse interaction between the body and certain drugs • Areas for detecting high frequencies are usually affected first (cochlear base) • Deafness resulting from ototoxicity is correlated to the dose, treatment duration, and combined use of other drugs • Neuronal survival is highest for this cause of deafness, theoretically making it a candidate for good results with a cochlear implant http://www.buckeyeinstitute.org/article/935 What kinds of drugs can cause this type of hearing loss? http://www.nbhope.org/blogs/under_the_microscope/archive/2008/01/29/17441.aspx Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Ototoxicity

34. Ototoxicity • Aminoglycoside antibiotics • Cause sensory and supporting hair cells degenerate and disappear • Begins affecting the cochlear base and then progresses towards the apex • Most studies show that hair cells are affected and damages to the neural system (ganglion) also often occur, but this connection is not well understood. • Survival of the ganglion (nerve) makes cochlear implant a potentially good therapy http://www.buckeyeinstitute.org/article/935 http://www.nbhope.org/blogs/under_the_microscope/archive/2008/01/29/17441.aspx Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Ototoxicity

35. Ototoxicity • Loop Diuretics • Most often used to treat heart conditions like hypertension and edema resulting from heart failure • Affect the ion transport system of the stria vascularis • Usually only result in short term deafness • Cisplatin • Chemotherapy drug used to treat cancer • Hair cell loss begins in lower basal turn with changes occurring in the stria vascularis • Causes symptoms similar to aminoglycosides http://www.buckeyeinstitute.org/article/935 http://www.nbhope.org/blogs/under_the_microscope/archive/2008/01/29/17441.aspx Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Ototoxicity

36. Infectious Diseases • Important cause of deafness in children • Can be contracted in utero, prenatally, or postnatally • Some diseases that can cause hearing loss include: • Bacterial Meningitis • Measles • Mumps • Maternal Rubella • Syphilis http://www.metrohealth.org/body.cfm?id=1570&oTopID=1570 Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Disease

37. Infectious Diseases • Bacterial Meningitis • Causes hearing loss in about 20% of infected individuals • The cause of hearing loss from meningitis is not well understood but is thought to be worsened by inflammation and blockage of blood supply to the inner ear • Shows no preference for hearing loss at high or low frequencies • Usually severe and permanent but can be bi- or unilateral • Severe neural damage from infection and bony occlusion (labyrinthine ossificans) are known to occur http://www.co.monroe.mi.us/Monroe/uploadedImages/bacterial%20meningitis(1).gif Unfortunately, if the auditory nerve or the cochlea are seriously damaged, a cochlear implant may no longer be an effective treatment Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Disease

38. Infectious Diseases • Measles • Common cause of acquired profound hearing loss in children • Lower cochlear turns affected and there is often a slightly reduced ganglion presence • Mumps • Most often results in unilateral deafness • Hair cell loss observed in basal and lower middle cochlear turn • Changes are mainly restricted to the cochlear duct with “mild to moderate secondary degenerations of cochlear neurons” www.wikipedia.org http://www.wales.nhs.uk/sites3/page.cfm?orgId=719&pid=23312 Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Disease

39. Infectious Diseases • In utero from maternal rubella • Ear most susceptible in the first trimester (especially during the 8th and 9th week) • There are generally varying degrees of hair cell loss but little effect on the neural components • Primarily affects the Stria vascularis and can cause secondary effects in the cochlea • Deafness occurring with congenital cataracts and congenital heart defects are known as the rubella triad. http://www.lib.uiowa.edu/Hardin/md/pictures22/cdc/269_B82-0203_lores.jpg Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Disease

40. Other Causes • Other causes for sensorineural hearing loss include: • Any stimulus for new bone growth or the development of bony abnormalities within the cochlea (trauma, otosclerosis2) • Meniere’s Disease3 • Autoimmune Inner Ear Disease4 • Hematologic (blood) Disorders • Can cause thrombosis in the cochlear blood supply which can cause cell death and result in permanent hearing loss • Lyme Disease • Syphilis • Idiopathic sudden sensorineural hearing loss • Hearing loss with no apparent cause http://www.principalhealthnews.com/topic/adam1003340 Ear Anatomy and Disease State Sensorineural Hearing Loss >> >> Disease

41. Patient Selection Eligibility Other Solutions Hearing Aids Osseo Integrated Hearing Aid Brain Stem Stimulation Ear Anatomy and Disease State Begin Section >> Patient Selection

42. Eligibility Determining whether a patient is eligible for a cochlear implant an assessment of responsiveness of auditory nerve is required Adults Must have at least 6 months experience with high-powered binaural (two ears) amplification AND undergo aided speech audiometry (established by FDA guidelines) Individuals with some remaining speech comprehension tend to have more success with a cochlear implant PTA > 90dB or word understanding up to 30% Children PTAs of at least 90dB Evaluation of child ability to acquire speech and language For infants, threshold testing is used to asses degree of hearing loss Ear Anatomy and Disease State >> >> Patient Selection Eligibility

43. Success of Implantation • While many factors impact how successful a particular implantation will be, the most successful patients generally17: • Have been hearing impaired for only a short time • Are younger • Have some level of retained speech abilities • Patients who learned to speak before losing their ability to hear tend to regain speaking abilities faster than individuals who never acquired speaking skills • Able and willing to learn quickly • Have strong support networks for learning to use their new implant • Retain more nerve (spiral ganglion cells) for the cochlear implant to stimulate What happens if a cochlear implant is not an effective treatment? Ear Anatomy and Disease State >> >> Patient Selection Eligibility

44. When a cochlear implant is not effective • Sometimes a cochlear implant is not the best treatment option and other restorative procedures must be considered and may include: • Hearing Aids • Osseo-integrated Hearing Aids • Brain Stem Stimulation http://jamescartermd.com/the-hearing-aids.htm http://www.earcentergreensboro.com/baha_device.htm http://www.wiredtowinthemovie.com/mindtrip_xml.html Ear Anatomy and Disease State >> >> Other Solutions Patient Selection

45. Hearing Aids Amplify existing sound (increase dB) but do not help the ear to distinguish between different frequencies Many individuals who use hearing aids do not qualify for cochlear implantation because their hair cells are mostly intact and require only amplification in order to detect sounds and discriminate between frequencies18 Often employed for older patients with functional but desensitized inner ear structures (including the cochlea and hair cells) http://www.nidcd.nih.gov/health/hearing/hearingaid.asp Ear Anatomy and Disease State >> >> Other Solutions Patient Selection

46. Osseo-Integrated Hearing Aids Used to bypass the outer and middle ear if they are damaged A sound processor is anchored in the temporal bone of the skull and translates sound waves into structural vibrations in the skull that stimulate the cochlea and trigger the signal cascade to the auditory nerve This implant is a good option for individuals who retain normal cochlear function19 http://www.cochlearamericas.com/Products/2127.asp Ear Anatomy and Disease State >> >> Other Solutions Patient Selection

47. Brain Stem Stimulation ABI (auditory brainstem implant) is a relatively new technology that bypasses all periphery auditory structures (outer, middle, and inner ear) to directly stimulate the cochlear nucleus in the brainstem ABIs are often used to treat neurofibromatosis type 2 (NF2) in which noncancerous tumors develop in the peripheral auditory structures Tonotopic mapping of the cochlear nucleus is required at the time of implantation Ear Anatomy and Disease State >> >> Other Solutions Patient Selection

48. Ear Anatomy and Disease State Review True/False: Younger patients tend to have greater success with cochlear implants. Did you get them all right? Click repeat lesson to review! True False What part of the inner ear is damaged with sensorineural hearing loss? c. cochlea a. pinna b. ossicles d. ear canal What is an important causal factor in hearing loss in children? a. noise b. disease c. age d. ototoxicity Ear Anatomy and Disease State Repeat Lesson Next Lesson >> REVIEW

49. Cochlear Implant Surgery Overview Procedure Risks Click on a section or click Begin Lesson! Tools Cochlear Implant Surgery Begin Lesson Lesson Review

50. Warning! Graphic material ahead!!!!! • Minor operation • - General Anesthesia • - Time: 1.5 - 5 hours • 1. Emplacement of Receiver • 2. Insertion of electrode array into cochlear • 3. Suture and Clean up • Some patients can go home immediately afterwards Cochlear Implant Surgery Overview Cochlear Implant Surgery >> Overview