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The head impulse test (HIT) and caloric test are important tests when examining for vestibular deficits. The HIT has a moderate sensitivity (35 45 ) and high specificity (90 ) compared with the caloric test. In 2009, the video Head Impulse Test (vHIT) was developed that can detect covert catch up saccades which can hardly be seen with the naked eye and has better sensitivity and specificity than the HIT. However, no studies have been conducted to evaluate the performance of vHIT in a Japanese population.In the caloric test, the monothermal stimulation technique is widely used in Japan. On the other hand, the bithermal stimulation technique is used worldwide with the exception of Japan.The objective of the present study was to evaluate the performance of the vHIT and monothermal cool caloric test (MCCT) mutually in a Japanese population. The sensitivity of the vHIT was 62.6 and specificity was 86.2 . The area under the receiver operating characteristic curve in the MCCT was 0.892 using VOR gain as the dependent variable, and 0.849 using CUS as the dependent variable.The vHIT is a specific and fast test to detect vestibular deficits using angular acceleration stimulation, and MCCT decreases test time and side effects without reducing sensitivity of the caloric test in bithermal stimulation.

Vestibular compensation after acute unilateral vestibular loss plays an important role in reducing uncomfortable symptoms, such as strong rotatory vertigo, nausea, and vomiting. In most cases of acute unilateral vestibular loss, the vestibular functions of the healthy side are temporally reduced but subsequently recover. This phenomenon is well known as vestibular compensation. In addition, the vestibular functions of the affected side also recover in some cases. To obtain an overall understanding of the vestibular function in cases with acute unilateral vestibular loss, vestibular function must be tested several times. However, the caloric test is not suitable for repetitive evaluations of vestibular function because it is time-consuming, labor-intensive, and tends to cause nausea.The video Head Impulse Test (vHIT), a novel semicircular canal function test that was developed in 2009, is suitable for repetitive evaluations of vestibular function. The vHIT can be performed relatively quickly and is unlikely to cause nausea.Here, we report a case of Ramsey-Hunt syndrome with frequent changes in the direction of gazed-nystagmus. We were able to evaluate the patient's complicated clinical course of vestibular function using vHIT in detail. We concluded that vHIT is a useful test for evaluating the clinical course of bilateral vestibular function in cases of acute unilateral vestibular loss.