Normal Waveforms
An interactive laboratory for the normal cVEMP and oVEMP. Move the sliders, compare sides, and watch the interaural asymmetry ratio update live.
The two diagnostic peaks
Every clinical VEMP is described by two peaks. For the cVEMP, an initial positive peak called P1 (or p13) is followed by a negative peak N1 (n23). The oVEMP reverses that order — N1 first at about 10 ms, then P1 at about 16 ms.
Try the simulator below. Toggle between cVEMP and oVEMP and notice how the peaks change.
Normative ranges
| cVEMP | oVEMP | |
|---|---|---|
| P1 latency | ~13 ms (±1.2) | ~16 ms (±1.3) |
| N1 latency | ~23 ms (±2.0) | ~10 ms (±1.0) |
| P1–N1 amplitude | 60–200 µV | 4–15 µV |
| Threshold | 75–95 dBnHL | 90–105 dBnHL |
| Best frequency | 500 Hz | 500 Hz |
| IAR upper limit | 33–40 % | 33–40 % |
The interaural asymmetry ratio (IAR)
The IAR adapts the Jongkees caloric formula to VEMP amplitudes:
Values under 33% are considered symmetric in most labs; 33–40% is a grey zone; above 40% suggests genuine asymmetry of otolith function. The simulator above computes the IAR live as the amplitude sliders change.[1,2]
A worked example
A 40-year-old presents with right-sided fullness and a single attack of vertigo. cVEMP amplitudes are recorded at 120 µV on the left and 55 µV on the right. Plug those values into the IAR:
That value is in the borderline range — within laboratory tolerance for some norms but flagging an emerging asymmetry. Repeating at 1 kHz to check for a frequency-tuning shift would be a natural next step in this patient given the clinical suspicion of Ménière's.[8]
Threshold testing
Threshold is determined by descending the stimulus intensity in 5 dB steps until the response disappears. A pathologically low threshold (≤ 70 dBnHL on cVEMP) is the most specific finding for superior canal dehiscence; conversely, an elevated threshold can help distinguish age-related decline from focal pathology.[9]