In 2006, a landmark study from Denmark, entitled "The Natural History of Vestibular Schwannoma," initiated a significant trend toward observation for managing small VS. Researchers in Copenhagen had the advantage that data for all Danish patients diagnosed with VS since 1976 was entered into a national database. The 2006 study by Stangerup et al. looked at the data for 1,818 patients (1976–2004) comparing intrameatal VS (in the auditory canal) and extrameatal VS (into the cerebellopontine angle). Remarkably, for the 729 patients having observation management via interval MRI scans, tumor growth was observed in only 17% of intrameatal tumors and 29% of extrameatal tumors. The mean observation time was 3.6 years (range 1–15 years). The researchers concluded: "VS growth occurs within the first 5 years after diagnosis in a limited number of tumors, primarily in tumors with an extrameatal extension. These findings justify primary observation of small tumors." The medical community and VS patients responded positively to these findings. Patient Surveys in the U.S. by the national Acoustic Neuroma Association showed an increase in "Wait-and-Watch" from 4% of respondents in 1998 to 20% in 2012. An important study in 2015 entitled "The Changing Landscape of Vestibular Schwannoma Management in the United States – A Shift Toward Conservatism," predicted that half of all cases of VS would be managed initially with observation by 2026. Stangerup et al. have urged caution (2019): "Most studies show that if tumor growth occurs, it is usually detected within the first few years of diagnosis.
The incidence of NF2 is approximately 1 per 60,000 people. Tumor sizes
Patient surveys in the U.S. by the national Acoustic Neuroma Association (1998, 2007–08, 2012, 2014) showed that the percentage of diagnosed tumors 1.5 cm or less increased significantly from 23% to 47%. Researchers in Denmark reported (2004): "The size of diagnosed tumors has decreased from a median of 35 mm in 1979 to 10 mm in 2001." In general, tumor size (diameter) is described as small (less than 1.5 cm), medium (1.5 to 2.5 cm), large (2.5 to 4.0 cm) and giant (more than 4.0 cm). (Note: 1 inch = 2.54 cm) Radiologists reporting on MRI scans use the Koos Grading Scale which relates tumor size to its proximity to the brainstem and nearby cranial nerves. Thus Koos grade 1 is a purely intrameatal (IAC) tumor, 1–10 mm in size; Koos grade 2, 10–20 mm, has extended into the cerebellopontine angle (CPA), but with no brainstem contact; Koos grade 3, 20–30 mm, fills the CPA space and touches on the brainstem, but without compression; and Koos grade 4, more than 30 mm in size, compresses the brainstem and nearby nerves, and displaces critical arteries. Diagnosis
Preliminary diagnostic procedures include ear examination, hearing and vestibular testing.