Vestibular schwannoma: how much residual hearing is useful?

The objective of this study was to determine the usefulness of residual hearing in the tumour ear in vestibular schwannoma patients.

A prospective case series study.

The study was performed at the Queen Elizabeth Health Sciences Centre in Halifax, Nova Scotia.

Thirty-three vestibular schwannoma patients and 13 controls underwent QuickSIN (Etymotic Research Inc, Elk Grove, IL) speech-in-noise testing with the tumour and good ears open and occluded. Nine testing conditions used three speakers with speech signal from the tumour side, the front, and the good ear side, with noise in other speakers.

Tumour ear contribution (TEC) was calculated by the decrease in score with the index ear occluded. Multiple regression analysis and correlation coefficients were used to determine predictors of TEC.

The strongest correlation was between the pure-tone average (PTA) and the TEC with signal from the tumour side. The speech discrimination score (SDS) was also significantly correlated with TEC in this condition. Neither PTA nor SDS correlated well with TEC with signal from other directions. Multiple regression analysis with TEC and sound from the tumour ear as the dependent variable showed that the SDS and PTA of the tumour ear are significant independent predictors (p = .049 and .037, respectively). There are no obvious breakpoints in the PTA or SDS to make 50%, 50 dB, or other operating points "special."

The main contribution of residual hearing is in signals from the tumour side. The various rules are more or less equivalent in discriminating between those who will have a high TEC and those who will not.