Cochealer implant surgery

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definition of cochlear implant , history of the procedure , purpose of the procedure , indications for cochlear implant , surgical procedure , risk of cochlear implant surgery , post operative care , normal result

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Cochealer implant surgery

  1. 1. Implant SurgeryDr , Ibrahim habib barakat , M.D.
  2. 2. overviewDefinitionPurposeHistoryHardwareDescriptionIndicationsSurgical ProcedureNormal resultsRisks
  3. 3. DefinitionA cochlear implant is a small, complexelectronic device used to treatsevere to profound hearing loss.It is surgically implanted underneaththe skin behind the patients ear.
  4. 4. purposeA cochlear implant bypass nonfunctional partsof the ear and directly stimulating theauditory nerve.It does not merely amplify sound. It increases the amount of nervous response tosound.It often improves sound detection andincreases speech understanding.
  5. 5. historyBetween 1965 and 1970, Dr. House teamed upwith Jack Urban, an innovative engineer, toultimately make cochlear implants a clinicalrealityThe new devices consisted of a single electrodeand benefited from microcircuit fabricationderived from space exploration andcomputer development
  6. 6. historyBetween 1965 and 1970, Dr. House teamed upwith Jack Urban, an innovative engineer, toultimately make cochlear implants a clinicalrealityThe new devices consisted of a single electrodeand benefited from microcircuit fabricationderived from space exploration andcomputer development
  7. 7. The House 3M Single-Electrode ImplantIn 1972, a speech processor was developed tointerface with the single-electrode implant and itwas the first to be commercially marketed as theHouse/ 3M cochlear implantMore than 1,000 of these devices were implantedbetween 1972 to the mid 1980sIn 1980, the age criteria for use of this device waslowered from 18 to 2 years and several hundredchildren were subsequently implanted
  8. 8. Multi-Channel ImplantsDuring the late 70s, work was also being donein Australia, where Clark and colleagues weredeveloping a multi-channel cochlear implantlater to be known as the Cochlear NucleusFreedomMultiple channel devices were introduced in1984, and enhanced the spectral perceptionand speech recognition capabilitiescompared to House’s single-channel device
  9. 9. Cochlear Nucleus Freedom
  10. 10. Cochlear Nucleus Freedom
  11. 11. Advanced Bionics Hi-Res 90K
  12. 12. Advanced Bionics Hi-Res 90K
  13. 13. DescriptionNormal hearing , sound vibrates the eardrum.The vibration is carried through the middle earand the cochlea. Movement in the cochlear fluid is transferred tohair fibers within the cochlea. The movement of these hair cells stimulatesganglion cells that send an electrical current tothe auditory nerve.The nerve carries the current to the brain, wherethe electrical stimulation is recognized as sound.
  14. 14. descriptionDamage to the hair cells within thecochlea (sensorineural deafness ), canoften be treated with cochlear implants, if damage to the hair cells is notaccompanied by damage to the auditorynerve itself.
  15. 15. descriptionCochlear implants consist of internal andexternal parts.The external parts include a microphone, aspeech processor, and a transmitter.The internal parts include a receiver-stimulatorand an electrode..
  16. 16. The various components are :1. The electrode array (which is placed in theinner ear). 2. The receiver for the electrode array. 3. The speech processor, a small electronicspackage that typically is placed in thewearers pocket.4. Transmitting coil and 5. Microphone, both of which are worn behindthe ear.
  17. 17. descriptionWithin the headpiece, the microphone picks upsound in the environment.The speech processor converts these sounds into adigital signal. The content of the generated digital signal isdetermined by the programming of theprocessor and is complex. The transmitter converts the digital signals intoFM radio signals and sends them through theskin to the internal parts of the implant.
  18. 18. descriptionThe internal parts are those that aresurgically implanted into the patient.The receiver-stimulator is disk-shapedand is about the size of a quarter. It receives the digital signals from thetransmitter and converts them intoelectrical signals..
  19. 19. descriptionA wire connects the receiver to a group ofelectrodes that are threaded into the cochleawhen the implant is placed. As many as 24 electrodes, depending on thetype of the implant, stimulate the ganglioncells in the cochlea. These cells transmit the signals to the brainthrough the auditory nerve. The brain theninterprets the signals as sound.
  20. 20. descriptionThe sounds heard through an implant artificialor robot-like. This is because the implants electrodes cannotmatch a persons 15,000 hair cells. However, as more electrodes are added, andthe software for the implant speech aremoving closer to how speech and othersounds are naturally perceived.
  21. 21. indicationsFor children who canrespond reliably, standard pure-tone andspeech audiometrytests are used to screenlikely candidates.Otherwise, ABR and OAEscan be used to detectvery young childrenwith severe-to-profound hearing loss
  22. 22. indicationsFor children aged 12-23months, the pure-tone average (PTA) forboth ears shouldequal or exceed 90dB.For individuals olderthan 24 months, thePTA for both earsshould equal orexceed 70 dB.
  23. 23. indicationsOlder children are then evaluated with speech-recognition tests with best-fit hearing aids in placein a sound field of 55-dBOne of the most common speech-recognition tests isthe hearing in noise test (HINT), which tests speechrecognition in the context of sentences (open setsentences)Current guidelines permit implantation in childrenwhose recognition is <60%
  24. 24. Meningitis and labyrinthitis ossificans12 months is the current age limit the FDA hasestablished for implantationHowever, a child with deafness due tomeningitis may develop labyrinthitisossificans, filling the labyrinth with boneIn these cases, special techniques may beneeded for implantation and suboptimaloutcome may result
  25. 25. Meningitis and labyrinthitis ossificans
  26. 26. Meningitis and labyrinthitis ossificansUsing serial imaging, implant teams may monitorpatients with new deafness due to meningitis andperform implantation at the first sign ofreplacement of the scala tympani with fibroustissue or boneOtherwise, implantation in patients withpostmeningitic deafness is usually recommendedafter 6 months to allow for possible recovery ofhearing
  27. 27. Cochlear AbnormalitiesPreoperative CT scan should always beperformed, to detect cochlear abnormalitiesor absence of CN VIIICochlear malformations, though, do notnecessarily preclude implantationIn pediatric patients with progressive hearingloss, neurofibromatosis II and acousticneuromas should be excluded by performingMRI
  28. 28. Cochlear Abnormalities
  29. 29. procedureThe future site of the implant reciever is marked withmethylene blue in a hypodermic needleThis site at least 4 cm posterosuperior to the EAC,leaving room for a behind-the-ear controllerNext, a postauricular incision is made and carrieddown to the level of the temporalis fascia superiorlyand to the level of the mastoid periosteuminferiorlyAnterior and posterior supraperiosteal flaps are thendeveloped in this plane
  30. 30. procedureNext, an anteriorly based periosteal flap,including temporalis fascia is raised, until thespine of Henle is identified.Next, a superior subperiosteal pocket isundermined to accept the implant transducerUsing a mock-up of the transducer, the size ofthe subperiosteal superior pocket is checked
  31. 31. procedureNext, using a 6 mm cutting burr, a corticalmastoidectomy is drilledIt is not necessary to completely blueline thesinodural angle, and doing so may interferewith proper placement of the implanttransducer
  32. 32. procedureUsing a mock-up of the transducer for sizing, a well isdrilled into the outer cortex of the parietal bone toaccept the transducer magnet housingSmall holes are drilled at the periphery of the well toallow stay sutures to pass through.These suture will be used to secure down the implantStay sutures are then passed through the holes
  33. 33. procedureUsing the incus as a depth level, the facialrecess is then drilled outThrough the facial recess, the round windowniche should be visualizedUsing a 1 mm diamond burr, a cochleostomy ismade just anterior to the round windowniche
  34. 34. procedureThe transducer is then laid into the well andsecured with the stay suturesThe electrode array is then inserted into thecochleostomy and the accompanyingguidewire is removed
  35. 35. procedureSmall pieces of harvested periosteum arepacked in the cochleostomy around theelectrode array, sealing the holeFibrin glue is then used to help secure theelectrode array in placeThe wound is then closed in layered fashionand a standard mastoid dressing is applied
  36. 36. AftercareFor a short period of time after the surgery, a special bandageis worn on the head during sleep. After about one month, the surgical wounds are healed andthe patient returns to the implant clinic to be fitted withthe external parts of the device and to have the deviceturned on and mapped.Mapping involves fine tuning the speech processor and settinglevels of stimulation for each electrode, from soft to loud.The patient is then trained in how to interpret the soundsheard through the device. The length of the training varies from days to years,depending on how well the person can interpret the soundsheard through the device.
  37. 37. Normal resultsMost profoundly deaf patients who receive animplant are able to discern medium and loudsounds, including speech, at comfortablelistening levels.Many use sound clues from the implant,together with speech reading and other facialcues, to achieve understanding.
  38. 38. Normal resultsAlmost all adults improve their communication skillswhen combining the implant with speech reading(lip reading), and some can understand spokenwords without speech reading. More than half ofadults who lost hearing after they learned to speakcan understand some speech without speechreading. Especially with the use of accessorydevices, the great majority can utilize the telephonewith their implants.
  39. 39. RisksAs with all operations, there are risks with thissurgery. These include:infection at the incision sitebleedingcomplications related to anesthesiatransient dizzinessfacial paralysis (rarely)temporary taste disturbancesadditional hearing lossdevice failure
  40. 40. RisksHowever, it should be noted that serioussurgical complications have been observed atonly one in 10,000 procedures of this type.Some long-term risks of the implant include theunknown effects of electrical stimulation onthe nervous system. It is also possible to damage the implantsinternal components by a blow to the head,which will render the device unworkable.
  41. 41. RisksA further consideration is that the use of magneticresonance imaging (MRI) for patients with cochlearimplants is not recommended because of the magnetspresent in the devices.Several companies have developed implants that do not usemagnets or have altered the receiver-stimulator make upto make it easier to remove the magnets before testing. One fact that reduces the concern about MRI testing is thatfor many medical indications, MRI can be replaced with acomputer assisted tomography scan (CAT or CT scan),which is not a problem for persons with cochlearimplants.
  42. 42. RisksAdditionally, in July 2002, the Food and DrugAdministration (FDA) issued a warning about apossible connection between increased incidence ofmeningitis and the presence of a cochlear implant.This warning included special vaccine recommendationsfor those with implants, as well as the voluntaryremoval from the market of certain devices.Specifically, those implants that included a positionerto hold the electrodes in place in the cochlea appearto be associated with an increased risk of the disease.

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