Outline of Literature Review
- DEFINE LITERATURE REVIEW
- A literature review is a summary of the main ideas in the various literature that have been done in a particular subject area.
- Conducting a literature review is a good way of conducting a research.
- The literature review gives the reader an overview of what the research that is being conducted is looking to address (Booth et al., 2012).
- The literature review also helps the researcher not to duplicate already known information.
- Basically, a complete literature review looks to document what is already known in a particular subject area, the knowledge gaps that still exist in the area, the faults of previous studies, and what the researcher thinks future studies should be addressing.
- CAUSES, PATHOGENESIS, MANAGEMENT
- In terms of noise-induced hearing loss (NHIL), the information that is already known can be divided into three categories: the cause and risk factors for NIHL; the pathogenesis and pathogenesis of NHIL; and the diagnosis, management, and prevention of NHIL.
- Toppila et al., (2000) assert that NIHL is caused continuous exposure to sounds of large frequency and intensity. The frequency quoted is 3 to 6 kHz while the loudness quoted by many sources is more than 100 decibels (Toppila et al., 2000).
- Occupational exposures, environmental factors, and individual genetic factors are the main risk factors of NIHL that are identified by Toppila and his colleagues. Other risk factors that have been identified by other sources include advanced age, male gender, low socioeconomic status, low educational status, and white race.
- THE ROLE OF GENETICS IN DETERMINING THE RISK PROFILE FOR NIHL.
- It is not clear if genetic factors influence the occurrence of NIHL; moreover, it is not known what these influential genetic factors actually.
- Future studies should look to determine the importance of genetic factors in NIHF. Most importantly, such studies should look to establish if ways of catching these genetic factors early so as to start preventing NIHL in the most susceptible individuals much earlier and, more vigorously.
- Moreover, the point of race as a risk factor for the development of NIHL is still a contentious issue. Studies that have been done only compared whites to blacks; it is prudent to have studies which will look to see how the other races compare and to try and explain these differences.
- SUDDEN OR CHRONIC NIHL.
- Sudden NIHL is mainly transient but can also be permanent.
- It mainly occurs following a sudden loud noise whose intensity is sufficient enough to damage the acoustic membrane.
- A ruptured or otherwise damaged acoustic membrane cannot generate sufficient vibrations for transmission of sound through the middle ear.
- Chronic NIHL develops as a result of frequent assault.
- Henderson et al., (2006) argue that the continuous sound assault leads to the production of reactive oxygen species (ROS) within the middle ear. These ROSs then lead to continuous apoptotic and necrotic death of the hair cells of the cochlear which are important in the perception of sound. Chronic NIHL thus as little to do with the state and functionality of the acoustic membrane.
- Destruction of cochlear cells summarizes the pathophysiology of NIHL. Furthermore, research has incriminated a reduction in blood flow to the inner ear in the pathogenesis of NIHL (Le Prell et al., 2007).
- Destruction of other sensorineural structures in the ear following lengthened exposure to hazardous sound levels explains the tinnitus that usually accompanies NIHL.
- PRODUCTION OF ROS,
- Even though it has been established that exposure to loud sounds is associated with the increase in ROS in the internal ear, the exact mechanism of this production is yet to be established.
- Future studies should look to establish this mechanism as it could be a window for an extra therapeutic intervention.
- EFFECTIVENESS OF VARIOUS INTERVENTIONS FOR NIHL.
- For diagnosis of the condition, use of audiogram is known to be the most effective method. Inconsistencies on the audiogram appear as notches; notches at 3-6 kHz indicate NIHL.
- Various pharmacotherapeutic interventions which target the various steps in the pathogenesis have been tested and some confirmed to be working. Recent advances look mainly to explore the possibility of reducing ROSs production following exposure to sound (Le Prell et al., 2007). The effectiveness of this method is reliant on the fact that these ROSs are mainly produced late in the after exposure to loud sound (Le Prell et al., 2007).
- The most important preventive mechanisms include avoidance of exposure totally or use of ear muffs and other dampening equipment in anticipation of exposure to loud sound. Future studies should focus on the development of simpler non-pharmacological interventions for NIHL.
References
Booth, A., Papaioannou, D., & Sutton, A. (2012). Systematic approaches to a successful literature review.
Henderson, D., Bielefeld, E. C., Harris, K. C., & Hu, B. H. (2006). The role of oxidative stress in noise-induced hearing loss. Ear and hearing, 27(1), 1-19.
Le Prell, C. G., Yamashita, D., Minami, S. B., Yamasoba, T., & Miller, J. M. (2007). Mechanisms of noise-induced hearing loss indicate multiple methods of prevention. Hearing research, 226(1), 22-43.
Toppila, E., Pyykko, I., Starck, J., Kaksonen, R., & Ishizaki, H. (2000). Individual risk factors in the development of noise-induced hearing loss. Noise and Health, 2(8), 59.
