CI Atlas · Audiological Evaluation · Module 01

1The test battery & the cross-check principle

Before anyone decides whether a person should have a cochlear implant, someone has to measure how they hear — and that measurement is never a single number. The audiological evaluation is a battery of complementary tests, each probing a different part of the auditory system, bound together by one governing idea: the cross-check principle. No result is accepted in isolation; every behavioural finding is checked against an independent, objective measure of the same function. When they agree, confidence grows; when they clash, the disagreement is itself the diagnosis — the present-emission-but-absent-brainstem-response of auditory neuropathy, or the too-good-to-be-true objective tests of a non-organic loss. This chapter is the audiologist's toolkit; the candidacy decision that uses its output is the next chapter. We begin with the logic that holds the whole battery together.

FWhat this chapter is

This is the how-we-measure-hearingchapter — the audiologist's diagnostic battery, from the pure tone to the cross-checked picture. It is the clinical foundation the candidacy decision (Chapter 11) rests on: candidacy applies these measurements; here we learn to make them.[2020]

FThe cross-check principle

The organising idea, from Jerger and Hayes, is simple and powerful: the result of any single audiometric test is cross-checked by an independent measure of the same function. A behavioural threshold is confirmed by an objective one; an audiogram is validated by the speech reception threshold. No number stands alone.[1976]

TPatterns and site of lesion

Each site of lesion leaves a recognisable fingerprint across the battery. Conductive, cochlear, retrocochlear, auditory neuropathy and non-organic patterns each combine the air–bone gap, tympanogram, reflexes, OAEs, evoked potentials and speech scores in a distinct way — so the diagnosis falls out of reading the tests together, never one at a time.

TWhy physiologic tests come first

Objective measures (tympanometry, reflexes, OAEs, ABR, ASSR) need little or no cooperation, so they are the backbone for infants and the way to confirm or refute doubtful behavioural results. A practical consequence is order: opening the session with the quick physiologic battery means the audiologist enters threshold testing already expecting a result, ready to question a surprise rather than accept it.

FChapter roadmap

Movement	Modules	What they cover
Behavioural core	2–5	Pure-tone audiometry, masking, bone conduction and the air–bone gap, and speech audiometry.
The objective battery	6–10	Immittance, the acoustic reflex, OAEs, the ABR, and ASSR / ECochG / cortical responses.
Children	11–12	Behavioural audiometry and speech perception in babies and young children.
Real-world & synthesis	13–18	Speech-in-noise, real-ear verification, loudness/tinnitus/non-organic loss, self-report, tele-audiology, and putting it all together.

We start with the test at the centre of it all — pure-tone audiometry (Module 2).

A single behavioural threshold, however carefully obtained, leaves real uncertainty — the patient may mishear instructions, feign, or have a neural disorder that pure tones cannot reveal. Each independent layer the battery adds — immittance and otoacoustic emissions, then an objective threshold measure, then the explicit cross-check of behavioural against physiologic results — closes a different failure mode, so confidence rises far faster than any one test could deliver. This is the cross-check principle made quantitative. Illustrative figures; schematic.

Case 10.1 · Results that disagree

An infant's OAEs are robustly present, but the ABR shows no replicable wave V even at high levels. A trainee is tempted to accept the OAEs as proof of normal hearing.

How should the conflicting results be interpreted?

Self-assessment — Module 12 questions

Question 1 · Foundation

What is the cross-check principle?

Question 2 · Trainee

Why does Wolfe recommend running the physiologic battery before behavioural testing?

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