Altered Neural Pitch Encoding in Vestibular Schwannoma: Evidence From Frequency-Following Responses

Vestibular schwannomas (VSs) frequently cause hearing dysfunction, yet standard clinical assessments may not fully capture neural processing deficits.

To determine whether unilateral VS impairs neural encoding of speech sounds, as measured by frequency-following responses (FFRs), beyond hearing loss alone.

Exploratory observational case-control study with both within-subject and matched between-subject comparisons.

Tertiary referral center (Antwerp University Hospital, Belgium).

Twenty-three adults (mean age 53.7 ± 9.8 years; 13 men) with untreated unilateral VS and sufficient residual hearing for FFR assessment were included. Patients with prior VS treatment, neurological disease, middle ear pathology, or profound hearing loss were excluded. VS ears were matched to a previous sensorineural hearing loss (SNHL) cohort by age, sex, and hearing thresholds.Intervention or Exposures:Magnetic resonance imaging-confirmed unilateral VS.

FFR measures of neural encoding of voice pitch were evaluated, with pitch strength as the primary outcome. Additional exploratory FFR measures and formant encoding (F₁) were analyzed. Auditory brainstem response (ABR) latencies and thresholds were also recorded.

Within subjects, VS-affected ears showed reduced pitch strength compared with contralateral ears for both the /a/ and /o/ stimulus sections (both P = .023). In the matched comparison with SNHL controls, pitch strength remained significantly reduced (P = .049 for /a/, P = .043 for /o/), whereas other FFR measures did not differ significantly. ABR analysis showed prolonged wave V latency and interpeak latency I to V in VS-affected ears.

VS is associated with reduced neural encoding of voice pitch, most consistently reflected by reduced FFR pitch strength even after accounting for hearing loss.

These findings suggest a selective vulnerability of temporal pitch coding in VS and support the clinical potential of the FFR as an adjunct measure when standard audiological tests do not fully capture patient-reported listening difficulties.