The clinical utility of the middle latency and 40Hz auditory evoked potentials in audiological electrodiagnosis

The two elcctrophysiological tests currently favoured in the clinical measurement of hearing threshold arc the brainstorm evoked potential (BAEP) and the slow vertex response (SVR). However, both tests possess disadvantages. The BAEP is the test of choice in younger patients as it is stable at all levels of arousal, but little information has been obtained to date at a range of frequencies. The SVR is frequency specific but is unreliable in certain adult subjects and is unstable during sleep or in young children. These deficiencies have prompted research into a third group of potentials, the middle latency response (MLR) and the 40HZ responses. This research has compared the SVR and 40HZ response in waking adults and reports that the 40HZ test can provide a viable alternative to the SVR provided that a high degree of subject relaxation is ensured. A second study examined the morphology of the MLR and 40HZ during sleep. This work suggested that these potentials arc markedly different during sleep and that methodological factors have been responsible for masking these changes in previous studies. The clinical possibilities of tone pip BAEPs were then examined as these components were proved to be the only stable responses present in sleep. It was found that threshold estimates to 5OOHz, lOOOHz and 4000Hz stimuli could be made to within 15dBSL in most cases. A final study looked more closely at methods of obtaining frequency specific information in sleeping subjects. Threshold estimates were made using established BAEP parameters and this was compared to a 40HZ procedure which recorded a series of BAEPs over a 100msec. time sweep. Results indicated that the 40mHz procedure was superior to existing techniques in estimating threshold to low frequency stimuli. This research has confirmed a role for the MLR and 40Hz response as alternative measures of hearing capability in waking subjects and proposes that the 40Hz technique is useful in measuring frequency specific thresholds although the responses recorded derive primarily from the brainstem.

Exposing and addressing tobacco industry conduct in low-income and middle-income countries

The tobacco industry's future depends on increasing tobacco use in low-income and middle-income countries (LMICs), which face a growing burden of tobacco-related disease, yet have potential to prevent full-scale escalation of this epidemic. To drive up sales the industry markets its products heavily, deliberately targeting non-smokers and keeps prices low until smoking and local economies are sufficiently established to drive prices and profits up. The industry systematically flaunts existing tobacco control legislation and works aggressively to prevent future policies using its resource advantage to present highly misleading economic arguments, rebrand political activities as corporate social responsibility, and establish and use third parties to make its arguments more palatable. Increasingly it is using domestic litigation and international arbitration to bully LMICs from implementing effective policies and hijacking the problem of tobacco smuggling for policy gain, attempting to put itself in control of an illegal trade in which there is overwhelming historical evidence of its complicity. Progress will not be realised until tobacco industry interference is actively addressed as outlined in Article 5.3 of the Framework Convention on Tobacco Control. Exemplar LMICs show this action can be achieved and indicate that exposing tobacco industry misconduct is an essential first step.