Lecture 24: Cochlear implants and improving the bionic interface Flashcards
Q: What are some common causes of conductive hearing loss?
A:
Earwax blockage: Excess earwax can block sound from reaching the eardrum.
Middle ear infections: Fluid buildup from infections (otitis media) can block sound transmission.
Ossicle damage: Damage to the middle ear bones (ossicles) from infection, injury, or otosclerosis (abnormal bone growth).
Eardrum perforation: A hole or rupture in the eardrum prevents sound waves from reaching the middle ear effectively.
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Q: What leads to sensorineural hearing loss?
A:
Aging (presbycusis): As we age, the hair cells in the cochlea degenerate, leading to gradual hearing loss.
Noise exposure: Prolonged exposure to loud sounds damages the delicate hair cells in the cochlea.
Genetic factors: Some people are born with or develop hearing loss due to inherited conditions.
Medications (ototoxic drugs): Certain medications (e.g., some antibiotics and chemotherapy drugs) can damage the inner ear structures.
Q: How does the Rinne test help diagnose hearing loss?
A:
The Rinne test compares air conduction (AC) to bone conduction (BC) using a tuning fork.
Normal Hearing: AC > BC, meaning sound is heard better through the air (via the ear canal).
Conductive Hearing Loss: BC > AC, meaning sound is better conducted through the bone than through the air (indicating a problem with the outer or middle ear).
Q: What is the Weber test, and how does it indicate the type of hearing loss?
A:
The Weber test uses a tuning fork placed in the center of the forehead to check for lateralization of sound.
Normal Hearing: Sound is heard equally in both ears.
Conductive Hearing Loss: Sound is heard louder in the affected ear (due to the blockage preventing external noise from masking the vibration).
Sensorineural Hearing Loss: Sound is heard louder in the unaffected ear, as the damaged ear cannot properly perceive the sound.
Q: What are ear grommets, and when are they used?
A:
Ear grommets are small tubes inserted into the eardrum to drain fluid from the middle ear, often used to treat otitis media (middle ear infection).
Function: They allow air to enter the middle ear, preventing fluid buildup and restoring normal sound conduction.
Risks: Grommets can cause scarring on the eardrum and potentially result in long-term reduction in hearing if the scarring is severe.
Q: How does stapes surgery help with conductive hearing loss?
A:
Stapes surgery (stapedectomy) is performed when the stapes bone in the middle ear is no longer able to vibrate properly due to conditions like otosclerosis (bone overgrowth).
Procedure: The surgeon replaces the stapes with an artificial prosthesis to restore sound conduction through the middle ear.
Outcome: This can significantly improve hearing for people with conductive hearing loss caused by stapes issues.
Q: What are bone-anchored hearing aids (BAHA), and how do they work?
A:
BAHA uses bone conduction to bypass damaged parts of the outer and middle ear.
How it works: The device is surgically implanted and transmits sound vibrations directly to the inner ear through the skull bone, bypassing the ear canal and middle ear.
Use: Primarily for patients with conductive hearing loss or single-sided deafness.
Q: How do cochlear implants help people with sensorineural hearing loss?
A:
Cochlear implants are devices that bypass damaged hair cells in the cochlea by directly stimulating the auditory nerve.
How it works: An external microphone captures sound, which is converted into electrical signals and sent directly to the auditory nerve.
Who benefits: Individuals with severe to profound sensorineural hearing loss who cannot benefit from traditional hearing aids.
Q: What role does gene therapy play in treating hearing loss?
A:
Gene therapy aims to repair or replace defective genes responsible for hearing loss, particularly for sensorineural hearing loss.
Mechanism: By introducing functional genes into damaged hair cells or cochlear structures, gene therapy may restore hearing at a cellular level.
Future potential: While still in experimental stages, gene therapies hold promise for reversing genetic hearing loss and regenerating damaged inner ear cells.
Q: What are the two main types of hearing loss, and how do they differ?
Conductive Hearing Loss: Affects the outer or middle ear. It occurs when sound waves can’t efficiently travel through the ear canal to the eardrum and ossicles.
-> Causes: Earwax blockage, infections, fluid buildup, or damage to the eardrum or ossicles.
-> Treatment: Often reversible with medical or surgical intervention (e.g., earwax removal, ear grommets, stapes surgery).
Sensorineural Hearing Loss: Affects the inner ear (cochlea) or auditory nerve. It occurs when there’s damage to the hair cells in the cochlea or the nerve pathways to the brain.
-> Causes: Aging, noise exposure, genetics, or damage to the auditory nerve.
-> Treatment: Permanent and typically managed with hearing aids or cochlear implants.
Q: How does a cochlear implant work?
A:
External Components: A microphone and speech processor capture sound.
Implanted Components: Electrodes placed in the cochlea stimulate the auditory nerve directly, bypassing damaged hair cells.
Q: When is an Auditory Brainstem Implant (ABI) used?
A: ABI is used when the auditory nerve is non-functional or absent, such as after removal of a tumor affecting the nerve. It bypasses the cochlea and directly stimulates the brainstem.
Q: What is the goal of gene therapy for hearing loss?
A: Gene therapy aims to repair or replace defective genes responsible for hearing loss, especially for sensorineural hearing loss, to regenerate or protect hair cells in the cochlea.
Q: What is the neural gap in cochlear implants, and why is it important?
The electrode array in a cochlear implant bypasses the damaged hair cells in the cochlea (which normally convert sound into electrical signals). Instead, the electrode array directly stimulates the spiral ganglion neurons, which is then carried as an impulse through the auditory nerve fibers to the brain.
A: The neural gap refers to the space between the cochlear implant’s electrode array and the spiral ganglion neurons. Closing this gap improves the effectiveness of the implant by enhancing direct stimulation of the auditory nerv
The neural gap refers to the space between the electrodes of the cochlear implant and the spiral ganglion neurons (and their auditory nerve fibers).
• Why is it important?
• A smaller neural gap allows for more precise stimulation of the spiral ganglion neurons. When the electrodes are closer to the nerve fibers, the electrical signals can directly and efficiently stimulate the neurons.
• A larger neural gap means the electrical signals have to travel a greater distance to reach the neurons. This can lead to:
• Less focused stimulation: The electrical signals might spread out too much, stimulating multiple neurons at once, leading to poorer sound resolution.
• Higher power requirements: The implant may need to use more energy to overcome the gap, which can decrease the battery life and overall efficiency of the device.
Q: How does gene electrotransfer work?
A:
The gene delivered to the cells usually encodes a protein that helps in repairing or regenerating these cells or restoring function.
DNA is delivered.
Electric pulses are applied to facilitate DNA entry into cells.
DNA interacts with the cell membrane, is internalized, and transported to the nucleus, where gene expression occurs.
