PP301 - Slow Down in the Fast Lane: Mitochondrial Disorder and the Auditory Brain

POSTERS

Instructional Level: Intermediate

Presenter(s)

BG

Briar Grant, BA (she/her/hers)

Wichita State University
Newton, Kansas

Disclosure(s): No financial or nonfinancial relationships to disclose.

PDF Slides

Lead Presenter(s)

KF

Katharine Fitzharris, AuD, MS, PhD (she/her/hers)

Associate Clinical Professor
Wichita State University
Wichita State University
Wichita, Kansas

Disclosure(s): Financial: Wichita State University: Employment (Ongoing); Nonfinancial: No nonfinancial relationships to disclose

PDF Slides

Abstract:
Mitochondrial disorder (MD), a common genetic disease resulting from cellular energy defects that can affect all organs of the body. Hearing impairment caused by MD is due to defects in oxidative phosphorylation. The case presented here is of a 36-year-old female who is undergoing MD testing and was referred for a central auditory processing disorder evaluation ((C)APD). A (C)APD diagnosis was given due to multiple abnormal test scores and ABR testing revealed fast-rate abnormalities bilaterally. The ABR abnormalities are consistent with demyelinating disorders which are linked to MD. Recommendations were made for therapy and neurology follow-up.

Summary:
Mitochondrial Disorder (MD)
MD is a common genetic disease that results in cellular energy defects that can affect every organ in the body, including the auditory pathway from cochlea to cortex. Clinically, MD may present as nystagmus, blindness, hearing loss, etc. MD is typically autosomal recessive and maternally-inherited but can also be autosomal dominant and X-linked. MD causes hearing impairment through defects in oxidative phosphorylation in the cochlea. Inherited MD has also been linked to non-syndromic hearing loss.

(Central) Auditory Processing Disorder ((C)APD)
Individuals with (C)APD may have poor skills with one or more of the following: sound localization and lateralization, auditory discrimination, pattern recognition, temporal aspects of audition, decrements with competing acoustic signals, and decrements with degraded acoustic signals. Common complaints/signs of (C)APD may include difficulties understanding rapid speech, trouble with paying attention, and the need for repetition during conversations.

Auditory Brainstem Responses (ABRs
ABRs are a far-field potential that have short latencies, <10 ms, and arise from CN VIII and nuclei in the auditory brainstem. Fast and slow-rate rarefaction waves and condensation waves are recorded, and the latencies and morphology of waves I, III, and V are analyzed.

The case presented here is from a 36-year-old female who underwent testing for MD and was referred for a central auditory processing disorder evaluation. A (C)APD diagnosis was given due to abnormal test scores and ABR testing revealed fast-rate abnormalities bilaterally.

Case History
Ms. X noted that she was struggling with understanding speech, localizing sounds and speech, and hearing in background noise; these issues have become difficult to ignore. She reported being extremely sensitive to loud sounds, having trouble recalling short- or long-term information, and having difficulty understanding rapid speech. She has undergone genetic testing, a chromosomal microarray analysis revealed 0.5 Mb deletion in 3p26.3 which compasses exons 1-3 of CNTN4, consistent with MD. Ms. X had normal hearing and excellent WRS on previous audiometric testing. She had an HHI-S score of 30 and a Vanderbilt Fatigue Scale score of 24.

Results
Results on behavioral (C)APD measures were abnormal for the CS and CW-DE of the SCAN-3A with abnormal ear advantages on several measures. Frequency Pattern testing normal, but scores for both ears were abnormal on the Dichotic Digits.

Results from the ABR were normal for slow rate waves (21.1 cps) with no evidence of ANSD. There were abnormal morphological breakdowns in fast waves (71.1 cps).

Conclusion
Due to her abnormal behavioral measures, Ms. X was diagnosed with (C)APD. Several therapies were recommended, including LACE and DIID trainings. Further, her fast-rate ABR had abnormal morphological breakdown bilaterally, which is indicative of demyelinating disease. She was referred to neurology to further examine these findings. MD can result in demyelinating disease due to a lack of sufficient oxidative phosphorylation in neurons. The demyelinating disease may be due to oxidative stress, stemming from MD causing neuroinflammation. It causes an influx in reactive oxygen species, which are harmful to neurons. Further research is needed on this topic.

Learning Objectives:

Upon completion, participants will be able to describe how mitochondrial disorder affects the body's systems.
Upon completion, participants will be able to describe how mitochondrial disorder can affect electrophysiological testing.