Recording Technique
Stimulus choices, electrode montage, recording parameters, EMG correction, and the practical pitfalls that explain most apparently absent VEMPs.
Setting up a VEMP
To record a VEMP you need three things: a loud, brief sound or vibration delivered to the ear; a contracted muscle to record from (neck for cVEMP, eye for oVEMP); and a system that averages hundreds of repeated responses to pull a tiny signal out of the background.
The standard stimulus is a 500 Hz tone burst at 95–100 dBnHL, delivered through insert earphones. The patient is asked to flex the neck or look up (depending on which VEMP is being recorded), and the system averages about 200 responses to produce the trace shown on screen.
Electrode placement
Click an electrode to see its role in the recording montage.
Recording parameters
| Parameter | cVEMP | oVEMP |
|---|---|---|
| Stimulus | 500 Hz tone burst | 500 Hz tone burst (AC) or BCV at Fz |
| Intensity | 95–100 dBnHL | 95–100 dBnHL |
| Rate | 3–5 / sec | 3–5 / sec |
| Sweeps averaged | 100–200 | 100–200 |
| Analysis window | 0–50 ms (10 ms pre) | 0–50 ms (10 ms pre) |
| Bandpass | 10–1000 Hz | 3–500 Hz |
| Patient posture | Supine, head raised 30° | Sitting, upward gaze ~25° |
| Muscle activation | Tonic SCM contraction | Sustained upgaze |
Common pitfalls
- Inadequate SCM contraction. The most common cause of an apparently absent cVEMP is not pathology but technique. Always use EMG biofeedback and confirm contraction with the patient.[2]
- Conductive hearing loss. AC stimuli are attenuated by middle-ear disease. Switch to bone-conducted vibration at Fz, using BCV-specific norms.[5]
- Age-related decline. VEMP amplitudes decrease and absence rates rise from about the seventh decade. Many labs report age-stratified normative data.[13,20]
- Bilateral abnormalities can look "normal." The IAR depends on a side-to-side comparison; bilateral disease may give a symmetrical-looking IAR with absolutely reduced amplitudes — always interpret amplitude against age-corrected norms, not the IAR alone.
- Polarity confusion. The cVEMP shows P1 first then N1; the oVEMP inverts that order (N1 first). Mistaking one for the other when annotating traces is an easy error.
Stimulus alternatives
High-frequency tone-burst VEMP (2–4 kHz) has emerged as a more specific indicator of third-window pathology than the 500 Hz response.[4] Bone-conducted vibration with a mini-shaker at Fz is the modality of choice when middle-ear pathology coexists with the indication for testing, and produces robust oVEMPs in particular.[16,18]