Bone Anchored Amplification/SSD Flashcards
Percutaneous
- The instrument has direct contact with the mastoid bone through the skin
- Bolt on outside of skin
What are the advantages of bone anchored devices?
- improved sound quality
- no occlusion effect (nothing in ear)
- cosmetics
- conventional BC hearing aids can cause pain and/or skin irritation with long-term use
Transcutaneous
Involves placement of a magnet anchored to the mastoid beneath the skin
What are the indications/requirements laid out by the manufacturers for a bone anchored device? Specifically for Percutaneous approach? For transcutaneous approach?
In general:
- hearing loss that can't be adequately fit with AC hearing aids - AC PTA greater than 40 dB HL - AC SRT less than 40 dB HL - AC WR greater than or equal to 80%
Percutaneous approach:
- mixed but primarily conductive hearing loss (can get more power from this approach so if mild then transcutaneous would be better) - BC PTA < 45 dB HL
Transcutaneous approach:
- Conductive or mixed hearing loss - BC PTA < 25 dB HL
What pathologies might benefit from bone anchored devices?
- Treacher-Collins Syndrome
- recurrent otitis media
- otitis externa
- atresia or severe malformation of outer ear
- microtia
What is SSD?
Unaidable hearing in one ear and normal hearing in the other ear
What are some causes of SSD?
- Physical damage to ear
- Compression of auditory nerve
- inner ear infections (viral or bacterial)
- tumors
- circulatory disorders
- severe Meniere’s disease
- trauma associated with head injury
- measles or mumps
- congenital SSD
Why does SSD matter?
- Speech, language, and educational development
- Head Shadow effect
- Problem with localization
- Lack of loudness summation
- Loss of squelch effect
Why is the Head shadow effect a factor in SSD?
- average of 6.4 dB or up to 7 dB for speech
- negligible for low frequencies
- up to 15-20 dB at 2000 Hz and above
- overall reduction in volume, plus filtering
- degradation of SNR
What is CROS amplification?
- Mic/transmitter on the poor/dead ear
- receiver on the “normal” ear
No amplification
What is a BiCROS?
- mic/transmitter on the poorer/dead ear
- microphone/receiver (aka hearing aid) on better ear
When would you use a CROS vs a BiCROS?
CROS –> SSD/Unilateral hearing loss (dead ear and normal ear)
BiCROS –> Asymmetrical hearing loss (dead ear and ear with hearing loss)
What is a transcranial CROS?
Deep-fitting power CIC hearing aid in the poorer ear that is set to the max amount of gain with the idea that the signal will be sent to the better ear through bone conduction.
Limitations:
- comfort (needs to be tight)
- feedback
- quality
What is the history of bone anchored devices?
Implanted in Europe (1977) –> approved for use with conductive and mixed HL in the US (1996) –> FDA approval for BAHA by Entific Medical Systems for SSD (2002) –> Entific Medical Systems was purchased by Cochlear Corporation (2005) –> Oticon trialed product (2006) –> Oticon launched Ponto (2009)
What are the candidacy factors for bone anchored devices?
- Better AC PTA at 500, 1000, 2000, and 3000 Hz that is < or equal to 20 dB
- free from generalized disease that may inhibit wound healing
- unable to use conventional AC or BC hearing aids
- Strongly motivated
- Able to maintain hygiene of the per cutaneous abutment
- Understand objectives and expectations of this type of amplification
- 5+ years of age
