Statistical analysis was done using JASP version 19.2 software (JASP Team, Amsterdam, Netherlands). The Shapiro-Wilk’s test of normality showed that the data followed normal distribution for all parameters of tVEMP. Descriptive statistics were done to find out the mean, median, mode, standard deviation, minimum, and maximum values for the response of tVEMP. Independent t-tests were used to compare the gender effects. Paired t-tests were done to compare ear effects.

The tVEMP response parameters were compared based on gender, are listed in Table 1. On analysis, the results show no significant differences between males (20.1 ± 1.72) and females (20.7 ± 1.56) P1 latency (p = 0.64), N1 latency (p = 0.18), interpeak latency (p = 0.26), rectified amplitude (p = 0.34) in the right ear. For the left ear also there is no statistical difference was found between male and female P1 latency (p = 0.21), N1 latency (p = 0.27) interpeak latency (p = 0.68). And, no significant difference was seen in peak-to-peak amplitude ratio (p = 0.89). There was a significant difference between males and females in rectified amplitude (p = 0.03*) in the left ear, but in the right ear, there was no significant difference. On group descriptive analysis the mean value of male P1 latency right ear (9.51 ± 1.10), P1 latency in left ear (9.59 ± 1.12), N1 latency in right ear (18.46 ± 1.80), N1 latency in left ear (17.82 ± 1.45), interpeak latency (right ear: 8.95 ± 1.84; left ear: 8.23 ± 1.36), rectified amplitude in right ear (1.30 ± 0.37) was higher than for females P1 latency in right ear (9.28 ± 1.10), P1 latency in left ear (9.02 ± 0.85), N1 latency in right ear (17.29 ± 1.97), N1 latency in left ear (16.78 ± 2.50), interpeak latency (right ear: 8.01 ± 1.83; left ear: 7.91 ± 2.06), rectified amplitude in right ear (1.17 ± 0.18). The mean asymmetry ratio (P1-N1) was found to be greater in females (10.40 ± 21.40) than males (9.47 ± 7.60).

Descriptive statistics were done to obtain the mean and standard deviation of P1 latency, N1 latency, interpeak amplitude, and rectified amplitude of the right and left ears. To find out the level of significance (p-value), a paired t-test and Cohen’s d were done. Data were collected from a total of 40 ears and are presented in Table 2. On analysing these data, it shows that there was no statistically significant difference between right ear and left ear in P1 latency (p = 0.63) and N1 latency (p = 0.20). On comparison of interpeak latency (p = 0.43) and rectified amplitude (p = 0.61) between right and left ear also shows no statistical difference.

Descriptive statistical analysis was conducted on data from all 40 ears of the participants instead of analysing the right and left ears separately. However, the amplitude asymmetry ratio was analysed from data collected from all 20 participants. The mean, median, standard deviation, minimum, and maximum values of P1 latency, N1 latency, interpeak latency, and rectified amplitude for both ears’ response parameters of tVEMP using a chirp stimulus in healthy young adults were listed in Table 3. The mean values of P1 latency, N1 latency, and interpeak latency were numerically higher, with increased amplitudes observed in the right ear compared to the left ear; however, these differences were not statistically significant.

The study results reveal no significant difference between males and females, but the rectified amplitude of the left ear shows a significant difference, with males exhibiting higher values than females. These findings align with a previous study comparing evoked potentials recorded from different muscles. Ferber-Viart, et al. [9] compared the VEMP findings obtained from the sternocleidomastoid and trapezius muscles, which showed that latencies were shorter and amplitudes were lower in the sternocleidomastoid than trapezius muscle. This indicates that the selection of the muscle for recordings can also have an influence. Regarding gender difference, similar to that of this study’s findings, no significant differences were found in latency or amplitude in a study done by Oliveira, et al. [10]. Later in 2005, Ge, et al. [11] conducted a study to investigate the gender differences in pain modulation evoked by repeated injections of glutamate into the trapezius muscle and found that males and females exhibit different pain responses, which suggests that gender may influence muscle characteristics. On consideration of additional factors, including muscle mass, tone, and hormonal influences is necessary to understand the impact of gender on VEMP responses in detail [12].

The findings of this study show no significant differences between right and left ears in P1 latency, N1 latency, interpeak latency, and rectified amplitude, which consistently correlate with previous studies done on VEMP. A study by Ferber-Viart, et al. [9] found that latencies and amplitude of VEMP recorded from sternocleidomastoid and trapezius muscles were symmetrical in normal subjects, with no significant differences between ears. Similarly, a study by de Oliveira, et al. [13] reported no significant interaural difference in VEMP parameters in healthy individuals. The absence of ear-related differences in this study may be attributed to the use of chirp stimuli, which are due to compensate for the frequency-dependent delays in the cochlea, leading to more synchronous activation of the auditory pathway. This synchronization could minimize potential interaural differences in neural processing times [14].

The analysis revealed that the mean P1 latency, N1 latency, and interpeak latency were longer, and the rectified amplitude was higher in the right ear compared to the left ear. These findings suggest subtle interaural differences in tVEMP parameters, which may be influenced by various factors. For instance, a study by Özgür, et al. [15] found that chirp stimuli resulted in shorter latencies and larger amplitudes compared to tone bursts in the SCM recorded VEMP. Also, they reported no significant interaural asymmetry ratios, suggesting that chirp stimuli may reduce ear-related differences in VEMP parameters. These differences may be influenced by several factors, which may include individual variations in muscle tone and contraction strength [15]. These factors can affect the amplitude of VEMP response, as the vestibular-cervical reflex stabilizes the head during unexpected translation [12]. Monitoring the contraction state of the SCM is crucial for accurately interpreting VEMP tests, as variation in muscle tone and mass can lead to significant interpersonal differences in response [12]. Additionally, anatomical differences between right and left vestibular pathways, like variations in length and myelination of neural fibres, could also contribute to these findings. Despite its potential, it remains robust and reliable; it lacks information and investigation on origin of its potential in the vestibular apparatus, normative in larger populations with different age groups, and to implement this test, frequency tuning has to be done on larger population. Even though this study gives the normative data for chirp stimuli tVEMP, the sample size is small and this could be a drawback of this study. Much more research is needed with a large sample size to establish definitive normative data.

This study helps in establishing the normative data for trapezius placed tVEMP using a chirp stimulus in young adults. The findings highlight the feasibility and reliability of this muscle for vestibular evoked responses. No significant gender ear-related differences were observed across most parameters, with the exception of higher rectified amplitude in the left ear between males and females. These results were consistent with previous research, indicating factors such as selection of muscle response for recording, individual physiological variations, and type of stimulus used for evoked responses.