ABSTRACT
A negative deflection with a 3-4 ms latency period has been reported to exist within the auditory brainstem response of some patients with profound hearing loss following a strong acoustic stimulus. This deflection, namingly the n3 or the acoustically evoked short latency negative response is assumed to be a vestibular-evoked potential, especially of saccular origin. Since the myogenic potential is also saccular in origin, the purpose of the present study was to investigate the relationship between these two tests in adults with profound hearing loss. The present cross sectional study was performed on 20 profoundly deaf volunteers[39 ears] who aged between 18-40 years old, randomly selected from available deaf adults in Tehran. The auditory brainstem response of all subjects was recorded following a 1000 Hz tone burst in 70-100dB nHL. Subjects were also tested for vestibular evoked myogenic potential. Only 34 of 39 ears recorded myogenic potential that negative response was recorded in 27 of 34 ears with normal p13 and n23. In seven ears with normal p13 and n23, the negative response was absent. In 3 ears with no p13 and n23, the negative response was observed, and two none. In view of the high prevalence of the negative response in profoundly deaf ears with normal p13 and n23, it could be concluded that the negative response can be used when for any reason, it is not possible to record myogenic potential and be considered as a new test in vestibular test battery
ABSTRACT
Ocular vestibular-evoked myogenic potential [oVEMP] is a novel vestibular function test. This short-latency response can be recorded through contracting extraocular muscles by high-intensity acoustic stimulation and can be used to evaluate contralateral ocular-vestibular reflex. The aim of this study was to record and compare the amplitude, latency, asymmetry ratio and occurrence percentage of oVEMP [n10] and cervical VEMP [p13] responses in a group of normal adult subjects. We carried out a cross-sectional study on 20 adult subjects' mean age 22.18 years, SD=2.19 with normal hearing sensitivity and no history of vestibular diseases. oVEMP and cVEMP responses in both ears were recorded using air conducted stimuli 500 Hz short tone burst, 95 dB nHL via insert earphone and compared. cVEMP was recorded in all subjects but oVEMP was absent in two subjects. Mean amplitude and latency were 140.77 microv and 15.56 ms in p13; and 3.18 microv and 9.32 ms in n10. There were statistically significant differences between p13 and n10 amplitudes [p<0.001]. This study showed that occurrence percentage and amplitude of oVEMP were less than those of cVEMP. Since these two tests originate from different sections of vestibular nerve, we can consider them as parallel vestibular function tests and utilize them for evaluation of vestibular disorders.
ABSTRACT
One of the problems in urban areas is nitrate contamination of ground waters. High nitrate concentration can cause methemoglobinemia, appearing as a risk factor is provided by ground waters. More than 80% of drinking water of Gorgan, Iran. So this investigation was done to determine of nitrate level in ground waters in Gorgan. This study has been carried out for investigation of nitrate rate in drinking water supply networks and not drinking water ground water wells of Gorgan city. This discriptive study was done on 43 ground waters and surface water samples which collected in spring and winter, in Gorgan during 2005. K+, Cl-, NO21-, NO31- of samples were analyzed by spectrophotometery method. The chemical analysis of ground waters of drinking water resources of Gorgan city showed significant variation of nitrate between 3.52 to 69.52 mg/l. The rates of nitrate in certain ground waters wells in vicinity of landfills were between 84.48 to 145.2 mg/l which is more than drinking water standards. Nitrate concentration in agricultural lands such as Shast-kula and Garmabdasht aquifers is lower than Ziarate aquifer in vicinity of urban area. Nitrate contamination in aquifers in vicinity of urban area and unsanitary disposal of solid waste substance may result from house sewage effluents and infiltration of landfillleachs to ground water wells