Impact of White Matter Hyperintensities on Speech Perception Performance in Patients for Cochlear Implant Evaluation
Faculty Mentor’s Name: Dr. Si Chen
Phone Number: (305) 849-3004
Project Category: Clinical
International Component or Travel: No
Background: Speech comprehension is a multisystem process that can be impaired at multiple levels from the peripheral hearing organ (inner ear), cochlear nerve, brainstem, to cerebral cortex. A properly functioning inner ear is essential for sound detection, however, multiple bidirectional pathways from the inner ear to the cerebral cortex are involved for attributing meaning to a sequence of sound, namely speech comprehension. Individuals who suffer from profound sensorineural hearing loss (SNHL) have increasing difficulty understanding speech, such as older patients diagnosed with presbycusis or age-related hearing impairment (ARHI) (1). When SNHL is severe enough, patients meet criteria for surgical implantation of a neuroprosthetic known as a cochlear implant. These devices transform acoustic sound signals into an electric stimulus that is directly applied to the inner ear (5). Cochlear implants have been shown to drastically improve the quality of life and speech comprehension in both children and adults (2, 3).
White matter hyperintensities (WMH) on magnetic resonance imaging (MRI)’s are radiological findings that have corresponded to areas of inflammation and gliosis when studying gross brain specimens (4, 10). Past studies have noted the effect that brain WMH may have on central processing (CP) of speech (6). CP occurring in the central nervous system (CNS) is vital in decoding the electrical stimulus provided by the inner ear in order to understand speech. When CNS is affected by processes such as aging or Alzheimer’s dementia, central processing is impaired. Once thought to be incidental findings without significant clinical relevance, WMH’s have been correlated to specific neurological diseases (i.e Alzheimer’s disease, vascular dementia, multiple sclerosis) (7 – 9). More recently, researchers found that there is a negative correlation between increasing number of brain WMH’s and scores on speech perception tests (SPT) (11). The authors studied patients with mild high-frequency SNHL and found that their sound detection threshold (pure tone audiometry) did not correlate with SPT, but the grade of WMH correlated with SPT. It suggests that despite relatively normal inner ear function, WMH played a role in speech comprehension. Further studies are needed to confirm whether increasing WMH represents increasing impairment of CP thus impede speech perception.
It is unclear how WMH’s affect the speech perception of patients with severe to profound sensorineural hearing loss, such as those requiring cochlear implantation. With impaired peripheral auditory organ, the patient increasingly relies on CP to decode sound and understand speech. MRI abnormalities have been examined in children with congenital SNHL (12-15) but there is no previous published study that examined WMH in adult cochlear implant patients. We have performed retrospective review of speech performance in cochlear implant patients. Preliminary results support that WMH may contribute to worse speech understand score. There has been no prospective study to confirm the finding. We hypothesize that WMH is associated with worse speech understanding scores before and after cochlear implant.
Methods: This will be a prospective study of patients who will undergo cochlear implant evaluation at University of Florida Cochlear Implant Program (UFCIP). Cochlear implant patients age 18 and older will be recruited at the time of their cochlear implant evaluation appointment with the principal investigator and audiologists.
Exclusion criteria are: incomplete medical record, lack of adequate MRI images, incomplete cochlear implant evaluation, prelingual deafness, developmental delay, cochlear implant surgery complications, known neurologic disorders including Alzheimers, Parkinsons, dementia, multiple sclerosis, stroke, congenital brain abnormalities, radiation to the head and neck, tumors of the brain, surgery of the brain, trauma to the head that resulted in a fracture.
Study subjects will undergo MRI brain as a standard part of CI evaluation. The MRI images will be reviewed by neuroradiologist for WMH burden with Fazekas score. Study subjects will also undergo speech performance evaluation as a routine part of CI evaluation with the audiologists. These speech performance measures include bilateral pure tone thresholds, speech recognition threshold (SRT), word recognition score (WRS), consonant-nucleus-consonant (CNC) word list score, individual and binaural AzBIO sentence scores in quiet and noise, and Montreal Cognitive Assessment (MOCA) score.
Role of Medical Student:
1. Assist in recruitment of patients from otolaryngology and audiology clinics, specifically patients who present for cochlear implant evaluations.
2. Obtain informed consent for participation in the project.
3. Coordinate appropriate otolaryngology, audiology, and radiology evaluations.
4. Enter data from cochlear implant evaluations.
5. Participate in abstract and manuscript writing after completion of project.
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