W9: ANSD Flashcards
Explain how ANSD and APD are the same but also different
- Lower part of the auditory brainstem, whereas APD is mostly associated with the auditory cortex
- Both groups demonstrate difficulty with auditory information processing and aspects are similarly affected in both groups
- ANSD is a comorbidity that may be observed in some cases with APD
- In current research, both are considered auditory perception disorders (some consider ANSD a type of APD)
What is ANSD?
ANSD is characterized by impaired temporal coding of acoustic signals due to deficiency in neural synchrony or neural transmission
The prevalence of ANSD is higher in (3):
- children with a history of NICU
- 40%
- ANSD is rare in well baby population (no more than 3 in 10000 births)
- children with HL
- 4-5% in all degrees of HL
- 10-15% of school-aged children with severe to profound HL
- individuals with genetic disorders
- one half of all children with ANSD diagnosis
Explain neural transmission and neural synchrony in ANSD?
- Neural transmission = function of auditory neural fibers
- Neural synchrony = function of myelin sheath
- A case with ANSD may have 1 of these or both
- It can begin with one, but after a while, almost all cases show a progress in the severity of the diseases and demonstrate the involvement of both
- The disease might start in the lower brainstem and progress to higher parts
- First only ABR is affected
- Then MLR, ALR, and eventually P3
- This is not for APD (we typically don’t see people with APD progress in severity)
What is the audiologic profile of ANSD?
Inconsistency in auditory findings
- absent or severely abnormal findings in ABR and CAP
- present findings in OAE, CM, and SP (except for IHC damage)
- normal hearing or slight to profound HL
- poor speech perception (especially in noise)
What is the most common HL pattern in adults with ANSD?
- LF loss (rising)
- flat loss
- no specific pattern found in children with ANSD
What are the variations in ANSD lesion site?
ANSD etiology is complex and broadly classified into ____ and ____ factors
acquired, genetic
What are 5 acquired or developmental factors?
- perinatal conditions (hyperbillirubinemia, low birth rate)
- neurometabolic diseases
- immune disorders (guillain-barre syndrome)
- ototoxic drug exposure
- severe developmental delay
half (50%) of patients with ANSD have ____ or ____
family history or genetic inheritance
What are 4 genetic factors of ANSD?
- autosomal recessive (OTOF)
- autosomal dominant (OPA1)
- x linked (AIFM1)
- mitochondrial mutations during maternal inheritance
____ of children with ANSD demonstrate at least one ____ other than HL
1/3, additional disability
____ of children with ANSD show evidence of ____
1/3, cochlear nerve deficiency (CND) or a very abnormal auditory nerve structure (due to CHARGE or waardenburg syndrome)
How is CND identified?
high resolution MRI
What is CND?
CND = total or partial loss of auditory nerve fibers or auditory nerve in general
What are 2 types of CND?
1) hypoplasia: a small cochlear nerve (< facial nerve), partial loss of ANFs
2) aplasia: absent cochlear nerve
What does an ANSD diagnosis require?
a comprehensive TB, using behavioural and objective tests of the peripheral and central auditory nervous system
ANSD minimum TB in audiology practice:
1) OAE and CM
2) ABR
3) audiometry
ANSD: 3 additional auditory tests you could add to the TB?
- acoustic startle reflex
- auditory steady state responses (ASSR)
- cortical auditory evoked responses (CAERs)
ANSD: 6 additional NON-auditory tests you could add to the TB?
- magnetic resonance imaging (MRI)
- pediatric and developmental history
- medical genetics evaluation
- ophthalmologic evaluation
- neurological evaluation
- communication assessment
Why is MRI necessary for ANSD?
- to identify individuals with CND
- in addition, CND is associated with intracranial abnormalities
ANSD - how do you differentiate CM from early ABR waves?
- It is recorded using both rarefaction and condensation click stimuli
- CM, as a cochlear response, is perfectly inverted with a change in stimulus polarity
What does the CM response look like ANSD?
CM begins within 1ms of stimulus presentation will appear as an initial downward shift from baseline with a rarefaction click stimulus and as an initial upward shift from baseline with a condensation click stimulus
ANSD - why is it important to define the CM response range?
To not have it confused with early ABR waves
Why is it important to monitor hearing status in those with ANSD?
to identify any spontaneous improvement of hearing ability, the need for subsequent hearing aid adjustments, and ANSD is progressive (may get worse)
ANSD - in some infants, early audiological findings might be ____ over time
transient or reversible
Improvement of auditory results may be observed in: (2)
- perinatal diseases or factors
- neurodevelopmental disorders
Do we have to monitor hearing status in APD?
No
What should you do if you suspect ANSD?
If suspect ANSD, lower the repetition rate (a second confirmation of ANSD)
What is the importance of recording CAEP in ANSD?
- it provides information about the integrity of the entire auditory system
- the absence of aided CAERs may help early identify cases who are the candidates for receiving CIs
ANSD - what do present aided CAERs mean?
- the HA leads to synchronous response in the ANS
- suggest the use of HAs
- When we use HAs and see CAEPs present it means the remaining auditory nerves or myelin sheaths are enough to provide auditory information to the auditory cortex to get the cortical auditory evoked responses (can rely on HAs to provide enough information to the auditory cortex)
ANSD - what do absent aided CAERs mean?
- the HA cant produce a synchronous response in the ANS
- suggest assessing CI candidacy
- When we aren’t able to see any clear CAEP it means there are not enough ANF or the myelin sheath is damage (the neural synchrony is not enough to get a clear response to the auditory cortex, even with the use of HAs). May benefit from CI
What is auditory steady state response (ASSR)?
an electrophysiological response recorded with an electrode setting similar to ABR
In ANSD, the ASSR follows the ____
ABR
What is ASSR good for?
- ASSR can provide a good estimation of hearing thresholds and to assess the function of lower parts of the auditory brainstem
- Use for those who cannot complete behavioural testing
What can inconsistency between estimated ASSR thresholds and behavioural thresholds assist in?
early identification
Explain how hearing thresholds are estimated using ASSR?
Case 1 = typical ANSD case
Case 2 = ANSD OPA1 gene mutation
explain 3 differences between OPA1 and OTOF
Case 3 = temperature sensitive ANSD
Case 4
