Meta-Analysis—Correlation between Spiral Ganglion Cell Counts and Speech Perception with a Cochlear Implant

Abstract

The presence of spiral ganglion cells (SGCs) is widely accepted to be a prerequisite for successful speech perception with a cochlear implant (CI), because SGCs provide the only known conduit between the implant electrode and the central auditory system. By extension, it has been hypothesized that the number of SGCs might be an important factor in CI outcomes. An impressive body of work has been published on findings from the laborious process of collecting temporal bones from CI users and counting the number of SGCs to correlate those numbers with speech perception scores, but the findings thus far have been conflicting. We performed a meta-analysis of all published studies with the hope that combining existing data may help us reach a more definitive conclusion about the relationship between SGC count and speech perception scores in adults.

Cochlear Implantation in US Military Veterans: A Single Institution Study

“…This is consistent with prior research suggesting that SGN counts did not correlate with CI outcomes when the SGN counts were between 2800 to 25,000. However, counts <2800 were associated with poor CI outcomes 20 . As noise exposure does not adversely affect outcomes in veterans—who are at higher risk of experiencing severe acoustic trauma than almost any other population—NIHL appears unlikely to reduce SGN counts below the level necessary to worsen CI outcomes in any population.…”

“…However, counts <2800 were associated with poor CI outcomes. 20 As noise exposure does not adversely affect outcomes in veterans-who are at higher risk of experiencing severe acoustic trauma than almost any other population-NIHL appears unlikely to reduce SGN counts below the level necessary to worsen CI outcomes in any population. Thus, a history of noise exposure alone should not impact decision-making regarding candidacy for cochlear implantation.…”

The Conundrum of Labyrinthitis Ossificans: An Etiology-Based Case Comparison and Review of Literature

“…The compressed electrode array (Form series - MEDEL) and double/split array are commonly used. While the ideal number of spiral ganglion population for serviceable hearing is 3500, and histopathological studies show a decrease in spiral ganglion number, there is no evidence linking spiral ganglion population with auditory-verbal outcomes in CI patients, as supported by a large meta-analysis by Cheng and Svirsky ( 10 ). For patients with failed CI in LO, the auditory brainstem implant is an alternative option, although its efficacy remains uncertain and is generally poorer than that of CI.…”

Changes in the Electrically Evoked Compound Action Potential over time After Implantation and Subsequent Deafening in Guinea Pigs

“…More direct evidence is provided by human histopathological studies (e.g., Seyyedi et al 2014 ; Kamakura and Nadol 2016 ) – showing that speech perception scores are positively correlated with SGC survival. This relationship, however, is not entirely undisputed, since there have also been reports of a negative correlation between the two (e.g., Nadol et al 2001 ; Fayad and Linthicum 2006 ), as well as several studies that did not find a significant correlation (see Cheng and Svirsky ( 2021 ) for a meta-analysis).…”