Effects of Plateau Time on Cervical Vestibular Evoked Myogenic Potential (cVEMP) elicited by 500-Hz Tone Burst / Jurnal Sains Kesihatan Malaysia

Cervical Vestibular Evoked Myogenic Potential (cVEMP) is a routine vestibular test which checks the integrity of vestibulocollic reflex (VCR) pathway. Clinically, 500-Hz tone burst is widely used stimulus to evoke a cVEMP. Although several studies have suggested different plateau times (PT) for eliciting cVEMPs, but not many have reported the optimal PT for evoking cVEMP using 500 Hz tone burst stimuli. Therefore, the present study aimed to investigate the effect of PT on cVEMPs elicited by 500 Hz tone burst at 95 dBnHL using four different PT (0, 2, 4 and 10 ms). Thirty healthy adults with normal hearing and vestibular systems participated in this study. Results revealed that the P1 latency was significantly longer for PT 10 ms compared to other PTs. N1 latency was significantly prolonged for long PT of 10 ms compared to PT 2 ms. P2 latency showed no significant differences among PTs. The P1-N1 inter-amplitude values however revealed no significant difference across all PTs. It was found that the P1-N1 inter-amplitude was severely affected after 4 ms of PT. This study concluded that the PT of either 0 or 2 ms yielded the most robust cVEMP.

Visual Evoked Potential Study in Amblyopia and Normal Groups

OBJECTIVE: The purpose of this study was to evaluate the relationship between the visual acuity and visual evoked potentials of the amblyopia patients and normal persons for the demonstration of the visual disability. METHOD: We performed visual evoked potential study, in 49 eyes of the 43 amblyopia patients and in 76 eyes of 38 normal young adults. Our study was carried out to evaluate the relationship of the visual acuity with N1, P1, N2, P2 latency, P1-N2 amplitude and to compare the latency of N1, P1, N2, P2, and P1-N2 amplitude in amblyopia patients and normal young adults. RESULTS: The mean values of N1, P1, N2, P2 latency were prolonged in amblyopia patients compared to normal young adults (p 0.05), but significant correlation was noted between the visual acuity and P1-N2 amplitude (p <0.05). CONCLUSION: These results showed prolonged latency of N1, P1, N2, P2 in amblyopia group as well as significant correlation between visual acuity and P1-N2 amplitude in both groups. So, P1 latency and P1-N2 amplitude are good parameters in evaluating the visual disability.

Clinical Applications of Visual Evoked Potentials

Visual evoked potentials were elicited by flash in 29 patients with a variety of cerebral lesions and in 10 normal controls. In 12 patients with focal brain lesions, no wave form could be recorded in one side. Of the remaining 23 sides, the average P1 latency showed no difference from that of the normal controls. In 17 patients with diffuse brain lesions no wave form could be elicited in 12 sides. Average P1 latency of remaining 22 sides showed statistlcally significant difference from that of normal controls. In this study it appears that delayed P1 latencies are associated with diffuse cerebral lesions rather than with localized lesions.