Evaluation of the Clinical Utility of Monothermal Caloric Testing in Comparison With the Video Head Impulse Test in Patients With Vestibular Neuritis.

Background: The monothermal caloric test (MCT) is a simplified alternative to the traditional bithermal caloric test for evaluating vestibular function. However, its diagnostic correlation with video head impulse test (vHIT) parameters, particularly in acute vestibular neuritis (VN), has not been thoroughly established.

Methods: This retrospective study included 32 patients with acute VN who underwent bithermal caloric testing and vHIT within 5 days of symptom onset. Caloric responses were analyzed to determine unilateral weakness (UW) and monothermal caloric asymmetry (MCA) for warm and cold stimuli, with and without correction for spontaneous nystagmus (SN). The vHIT was performed using head impulse paradigm (HIMP) and suppression HIMP (SHIMP). Gain, gain asymmetry, and the presence of corrective saccades were evaluated. Correlation analyses were performed between caloric parameters and vHIT metrics.

Results: Significant asymmetry was observed in the vHIT gain between the ipsilesional and contralesional ears in both the HIMP and the SHIMP (P < .001). Uncorrected warm MCA showed a stronger correlation with vHIT gain asymmetry (HIMP: r = 0.561, P < .001; SHIMP: r = 0.672, P < .001) than UW or SN-adjusted MCA values. Notably, SN correction reduced the correlation strength between MCT and vHIT results, suggesting SN as a clinically-relevant marker of vestibular asymmetry in the acute stage.

Conclusion: Warm MCA without SN adjustment demonstrated the strongest correlation with high-frequency vestibulo-ocular reflex deficits measured using the vHIT in patients with acute VN. These findings suggest that the uncorrected MCT may be valuable and practical in assessing vestibular hypofunction, particularly when interpreted alongside the vHIT. The complementary use of the MCT and vHIT may enhance diagnostic accuracy and efficiency in acute vestibular evaluation.