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
