Acoustic neuroma epidemiology and demographics

Overview
The true incidence of Acoustic neuromas has been difficult to estimate. The incidence has been reported to range from 1 to 20 per million per year. A study of acoustic neuromas in a review of 24,000 brain MRIs reported a prevalence of 0.07%. When comparing the clinical incidence of acoustic neuromas to the prevalence of occult acoustic neuromas ascertained from histopathological studies of temporal bones, it can be concluded that the vast majority of tumors that exist are never clinically manifested. Acoustic neuromas are most commonly diagnosed between the ages of 30 and 68. Reported cases of acoustic neuroma in childhood are rare and in such patients other evidence of NF2 should be investigated. In a study of 146 cases of acoustic neuromas, the median age of cases was 52 years. In a second study of 793 cases of Acoustic neuroma, the median age of the cases was 54 years. The sex ratio (females/males) for acoustic neuromas has been reported to be >1 However, data from the Central Brain Tumor Registry of the United States (CBTRUS) do not support a female/male difference Nevertheless,some of the studies that analyzed Swedish data, the sex ratio (females/males) of acoustic neuromas in the Nordic counties has been shown to be >1. This sex ratio may indicate that hormones play a role in the etiology of acoustic neuromas The tumor has been reported to be higher in whites than in non-whites as well as being uncommon in individuals of African ancestry According to some studies the incidence of acoustic neuromas has been increasing. This may be due to several factors. Steady improvements in diagnosis, such as the introduction of auditory brainstem response, CT, and MRI could explain part of the increased incidence. Increased awareness among physicians and patients of the symptoms of acoustic neuromas may have caused an increase in the reporting of the tumor. Changes in classification or coding may also explain some of the trend, whereby registries may have misclassified nonvestibular schwannomas as acoustic neuromas. Or, there may be a true increase in the incidence of these tumors. The trend may also lend support to the emerging hypotheses regarding an environmental cause of these tumors. Established and hypothesized risk factors have been reported extensively in the literature and include ionizing radiation exposure, cellular telephone use, specific occupations, a possible hormonal cause, and loud noise exposure.

Average annual incidence rates, overall and by gender and race, CBTRUS (1995–1999) and LACCSP (1995–1998) Rates are per 100,000 person-years and are age adjusted to the year 2000 U.S. standard population. Abbreviations: CBTRUS, Central Brain Tumor Registry of the United States; CI, confidence interval; LACCSP, Los Angeles County Cancer Surveillance Program.