Effect of late-onset blindness on cervical vestibular evoked myogenic potentials.

PURPOSE: Approximately 1.3 billion people worldwide have vision impairment. The aim of the present study was to investigate the influence of Late-Onset blindness on cervical vestibular evoked myogenic potentials (cVEMP) responses. Accordingly, this study was performed to investigate and compare the parameters of the cVEMP test in sighted and late-onset blind individuals. MATERIALS AND METHOD: In this cross-sectional- comparative study, cVEMP was recorded by presenting a tone burst stimulus of 500 Hz with an intensity of 95 dBnHL in 20 sighted and 20 late-onset blind individuals aged between 18 and 30 years old. RESULTS: cVEMP was observed in all the individuals (100%). The average latency of P13 and N23, amplitude, amplitude ratio, and VEMP threshold did not differ significantly between the two groups (p > 0.05). CONCLUSION: The findings of the study revealed that the formation of the neural pathway and reflex arch of cVEMP is similar between late-onset blind and sighted individuals. Thus, cVEMP can be a suitable test for assessing the vestibular function of late-onset blind people.

Effects of aging on spatial hearing.

BACKGROUND: Aging has several effects on auditory processing with the most important effect known as speech perception impairment in noise. AIMS: The aim of the present study was to investigate the effects of aging on spatial hearing using quick speech in noise (QSIN) and binaural masking level difference (BMLD) tests and speech, spatial, and qualities of hearing scale (SSQ) questionnaire. METHODS: The study was carried out on 34 elderly people, aged 60-75 years, with normal peripheral hearing and 34 young participants, aged 18-25 years. Using SSQ questionnaire and QSIN and BMLD tests, the spatial auditory processing ability was compared between the two groups. RESULTS: Comparison of mean scores using independent t test showed that there was a significant difference in the mean scores of QSIN, BMLD tests and SSQ questionnaire between the two groups (p < 0.001). Sex was not found to have any effect on the results (p > 0.05). DISCUSSION: Structural and neurochemical changes that occur in different parts of the central nervous system by aging affect various aspects of spatial auditory processing, such as localization, the precedence effect, and speech perception in noise. CONCLUSIONS: Lower scores of older adults with normal hearing in SSQ questionnaire and behavioral tests, compared with younger participants, may be considered as their weak performance in spatial auditory processing. The results of the present study reconfirm the effects of aging on spatial auditory processing, such as localization and speech perception in noise.

Vestibulo-Ocular Reflex Abnormalities in Posterior Semicircular Canal Benign Paroxysmal Positional Vertigo: A Pilot Study.

INTRODUCTION: Benign paroxysmal positional vertigo (BPPV), involving the semicircular canals, is one of the most common diseases of the inner ear. The video head impulse test (vHIT) is a new test that examines the function of the canals. This study aimed to investigate the vestibulo-ocular reflex (VOR) gain, gain asymmetry and saccades after stimulating all six canals in patients definitively diagnosed with posterior semicircular canal BPPV (PSC-BPPV). MATERIALS AND METHODS: Twenty-nine unilateral PSC-BPPV patients with normal oculographic and caloric results were enrolled in this study. vHIT was performed on six canals, and VOR gain, gain asymmetry and saccades were measured. RESULTS: Sixteen (55.17%) patients had abnormal posterior canal VOR gains in the ipsilesional ear. VOR gains in both horizontal canals were within normal limits. Superior canal VOR gains were mostly lower than normal and were not correlated to PSC abnormalities (P>0.05). No corrective saccades could be observed. CONCLUSION: VOR gain in the direction of the posterior semicircular canal may be reduced in PSC-BPPV patients. Evaluation of PSC-VOR parameters could be beneficial, although superior canal measurements should be interpreted with caution.

Noisy galvanic vestibular stimulation enhances spatial memory in cognitive impairment-induced by intracerebroventricular-streptozotocin administration.

There are several anatomical connections between vestibular system and brain areas construct spatial memory. Since subliminal noisy galvanic vestibular stimulation (GVS) has been demonstrated to enhance some types of memory, we speculated that application of noisy GVS may improve spatial memory in a rat model of intracerebroventricular streptozotocin (ICV-STZ)-induced cognitive impairment. Moreover, we attempted to determine the effect of repeated exposure to GVS on spatial memory performance. The spatial memory was assessed using Morris water maze test. The groups received 1 (ICV-STZ/GVS-I) or 5 (ICV-STZ/GVS-II) sessions, each lasting 30 min, of low amplitude noisy GVS, or no GVS at all (Control, ICV-saline, ICV-STZ/noGVS). Hippocampal morphological changes investigated with cresyl violet staining and the immediate early gene product c-Fos, as a neuronal activity marker, was measured. Hippocampal c-Fos positive cells increased in both GVS stimulated groups. We observed significantly improved spatial performance only in ICV-STZ/GVS-II group. Histological evaluation showed normal density in ICV-STZ/GVS-II group whereas degeneration observed in ICV-STZ/GVS-I group similar to ICV-STZ/noGVS. The results showed the improvement of memory impairment after repeated exposure to GVS. This effect may be due in part to frequent activation of the vestibular neurons and the hippocampal regions connected to them. Our current study suggests the potential role of GVS as a practical method to combat cognitive decline induced by sporadic Alzheimer disease.

Amplitude changes of the electrically evoked compound action potential in children with cochlear implants: preliminary results.

OBJECTIVE: Use of electrical instead of acoustical stimulation has made much objective electrophysiological evaluation possible. This is useful for management process of young children before and after the cochlear implant. These evaluations have been used for assessment of neuronal survival before cochlear implant and for monitoring of prosthesis function during and after the surgery. Electrically evoked compound action potential is one of these tests which makes a valid and reliable objective evaluation possible. The aim of this study was to evaluate the potential's amplitude changes three months after receiving the device in pediatric cochlear implant recipients. METHODS: In this longitudinal study, changes of the potential's amplitude in four given electrodes in four sessions after receiving the device are evaluated by approximately one month intervals in children implanted in Amir Alam and Hazrat-e-Rasoul hospitals, Tehran in July to December 2007. FINDINGS: The mean amplitude of the electrodes did not significantly change in different sessions, while there was significant difference between the first and the other electrodes' responses in every session (P<0.05). CONCLUSION: Due to high reliability of the responses, the clinician can fit the speech processor for a long time. Better responses in apical electrodes may lead to develop an effective coding strategy.