Hearing loss in young men: possible aetiological factors.

In the present retrospective register study a very large data base consisting of screening audiograms obtained at military conscription of 18-year-old Swedish men was used. The study group comprised 450,175 men, aged 18 years, tested at conscription to military service. There were nine age groups covering a 24-year period, from 1971 to 1995. This database was compared with a number of different pre- and postnatal factors with possible influence on the hearing function. This ecologic methodology gives tentative clues (but no proof) of possible ototraumatic influences. The hearing capacity was fairly similar during the entire span of the study and only small variations were observed. There was a slight tendency of better hearing capacity in the later age groups, compared with the earlier ones. The mean thresholds of the frequencies 4 and 6 kHz were slightly elevated in 1971, 1976 and, to some extent also in 1992. We tried to calculate the levels of leisure noise exposure during the study period. There was no apparent tendency of reduced noise levels, on the contrary the noise levels seemed to increase. The treatment programmes for acute otitis media (AOM) underwent considerable changes during the period from the early fifties to the early eighties, when the participants were pre-school children. One possible explanation for the slight improvement of the hearing capacity could be less ototraumatic influence of AOM. Data about the occurrence of four common epidemic diseases, covering the periods preceding and succeeding the years when the participants were born indicated that influenza and possibly pertussis (whooping cough), constitute putative prenatal risk factors for mild to moderate high frequency hearing loss.

MRI evidence of exogenous vascular endothelial growth factor-enhanced transport across inner ear barriers in guinea pigs / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>Increased vascular endothelial growth factor (VEGF) and VEGF receptor expression is the important biological response under shear stress, ischemia and hypoxia conditions. Mechanical vibration induced cochlea shear stress and trauma obviously upregulate VEGF and VEGF receptor 2 (VEGFR2) expression in the cochlea. To evaluate the possibility of VEGF varying the transport in blood-labyrinth barrier and blood-perilymphatic barrier.</p><p><b>METHODS</b>Eleven guinea pigs, male and female, weighing from 300 g to 900 g were kept under general anaesthesia with xylazine (16 mg/kg) and ketamine (60 mg/kg) for both drug delivery and MRI measurement. VEGF (6 ears) and phosphate-buffered saline (PBS, 5 ears) were delivered to the inner ear via the round window membrane (soaked in gelfoam). The T1 contrast agent gadodiamide (Gd-DTPA-BMA) chelated bound paramagnetic gadolinium was used as the inner ear barrier transportation tracer. A Bruker Biospec Avance 47/40 experimental MRI system with a magnetic field strength of 4. 7 Tesla and a 40 cm bore was used for the 2-dimensional cochlea MRI evaluation. The Paravision software was used for image intensity measurement and the Adobe Photoshop 6.0 software was used for image presentation.</p><p><b>RESULTS</b>VEGF induced significant Gd uptake in the scala tympani and scala vestibuli, but had little effect on the uptake of Gd in the scala media.</p><p><b>CONCLUSIONS</b>VEGF significantly increased the transportation of blood-perilymphatic barrier and adapted the inner ear for compensation and repair.</p>