Acute alcohol exposure can affect balance and the vestibulo-ocular reflex (VOR), but the effect is not uniform across every vestibular test. In a study of 31 healthy volunteers, investigators observed lower postural-stability scores, decreased gains for several high-frequency VOR measurements, and shorter rotational-response time constants after drinking. Other measurements remained statistically unchanged. This pattern matters when applying vestibular physiology to forensic alcohol interpretation.
The VOR is a reflex that stabilizes the retinal image as the head turns. Sensors in the semicircular canals register angular movement, and the nervous system produces compensatory eye movements. Vestibular laboratories use different tests to probe different properties: video head impulse testing (vHIT) measures high-acceleration responses, while rotational-chair testing samples other frequencies and the duration of eye-movement responses. Posturography measures standing stability under specified sensory conditions.
A quantitative change in VOR gain is not the same observation as a horizontal gaze nystagmus (HGN) clue during roadside testing. Different protocols test different functions and should not be treated as interchangeable without validation.
Choi and colleagues evaluated 31 healthy adults when alcohol-free and after acute alcohol consumption. Individual dosing was calculated to target approximately 0.05% blood alcohol concentration (BAC). The observed average BAC was 0.07% ± 0.018%, ranging from 0.05% to 0.12%. The group averaged 30.3 years of age, with 22 women and nine men.
The investigators performed posturography on normal and perturbed support surfaces with eyes open or closed, video head impulse testing, rotational-chair testing, and subjective visual vertical/horizontal assessments. Using multiple modalities allowed the study to distinguish significant effects from outcomes that did not change.
Postural stability declined. With eyes open on normal support, the mean stability score fell from 94.58 to 92.35 (p = 0.004). With eyes closed on perturbed support, it fell from 88.32 to 84.32 (p = 0.003). The investigators also reported statistically significant decreases in the other tested support/vision combinations. These are group-level laboratory scores, not cutoffs for diagnosing individual impairment.
Several high-frequency VOR gains declined. Right lateral-canal gain decreased from 1.04 to 0.96 and left lateral-canal gain from 0.99 to 0.92 (both p = 0.001). Some other canals showed significant changes, but not all. The changes generally stayed within the normal range, without meaningful overt refixation saccades at the studied exposures.
Rotational velocity-storage time constants shortened. For clockwise rotation, the mean fell from 16.43 to 12.70 seconds (p = 0.008); for counterclockwise rotation, from 14.73 to 12.37 seconds (p = 0.003). Velocity storage is a central vestibular mechanism that extends the duration of reflex eye movements beyond the shorter response of the semicircular canals.
Most mid-frequency rotational VOR-gain measurements, subjective visual vertical/horizontal perception, and phase lead in the slow harmonic acceleration test did not show statistically significant alcohol effects. A correct reading of the paper must include these null findings. It does not support the claim that every eye-movement or vestibular outcome becomes abnormal after drinking.
The study provides evidence of alcohol-related physiological changes in controlled participants. It does not permit an examiner to infer an individual’s BAC from sway or VOR gain, nor does it validate a roadside HGN test or establish that alcohol caused a particular fall. Case-specific review must consider chronology, chemical testing, observation conditions, vestibular disease, fatigue, medications and other possible causes of instability.
This distinction between specimen concentration and target-organ response is also central to our discussion of blood alcohol versus brain alcohol concentration. Accurate measurement, physiological interpretation and behavioral causation are related but separate scientific questions.
No. In this study some vestibular measures changed while others did not. One normal measurement cannot establish that every other physiological or behavioral function was normal.
No. VOR gain measures a reflexive eye response during head movements under a defined protocol. HGN assessment observes eye movement during a different procedure. A result from one is not a substitute for the other.
No. The sample was small, the measured BACs ranged from 0.05% to 0.12%, and the study did not validate an individual diagnostic or legal threshold.
Choi HG, Hong SK, Park SK, Lee H-J, Chang J. Acute Alcohol Intake Impairs the Velocity Storage Mechanism and Affects Both High-Frequency Vestibular-Ocular Reflex and Postural Control. International Journal of Environmental Research and Public Health. 2022;19(7):3911. doi:10.3390/ijerph19073911.