Using a database of patients diagnosed with vestibular schwannoma (VS) in Denmark, Stangerup et al identified 156 patients with intracanalicular vestibular schwannomas followed over a 10-year period with serial magnetic resonance imaging and audiograms. Their main objectives were to determine the proportion of intracanalicular VS that grow over time, as well as the long-term hearing outcomes.
It is not clear if the authors actually reviewed the images themselves with access to the source data or whether measurements were simply entered into their national database from individual centers. This is not to be critical, but the latter is a weaker methodology that can be prone to error and bias. Their criterion for growth was an increase in tumor growth in any dimension equal to or greater than 2 mm. Their argument is that the contemporary error of linear measurement is up to 2 mm. They did not measure tumor volumes. Most would agree that an increase in maximal diameter is a crude indicator for growth of a 3-dimensional structure. This is not to be critical, since radiologists do not measure such volumes routinely. However, for a robust research analysis, volumetric measurements are more appropriate; tumors may expand in volume yet appear “stable” with linear measurements. Often this is correlated with a clinical decline such as hearing loss, and the patient is surprised because the tumor “did not grow.”
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