Vestibular schwannoma classification
Small vestibular schwannoma (<1,5 cm)
Medium vestibular schwannoma (1.5 cm to 2.5 cm)
Large vestibular schwannoma (2.5 cm to 4 cm).
Giant vestibular schwannoma (greater than 4 cm).
Tumors are described by a combination of their location and size.
An intracanalicular tumor is small and in the internal auditory canal.
Koos grading scale
see Koos grading scale.
Hannover grading scale
A cisternal tumor extends outside the auditory canal. A compressive tumor infringes upon the cerebellum or brainstem. Very large tumors may obstruct cerebrospinal fluid drainage.
The tumor may develop within the auditory canal, where the vestibulocochlear nerve which supplies the inner ear penetrates the skull (intracanalicular neuroma) or outside the canal (extra-canalicular neuroma).
see Cystic vestibular schwannoma.
The growth patterns of the tumors were divided into three groups according to their growth rate: a regression group, a “no-growth” group (growth rates from 0-0.11 cm/year) and a progression group (growth rates from 0.19-1.72 cm/year). An additional operation was required in all patients whose growth rate was more than 0.38 cm/year. A statistical study on the factors associated with an increased growth rate showed that the three histopathologic factors most significantly associated with a postoperative growth rate were hyaline degeneration (p < 0.05), cell density (p < 0.005), and PCNA labeling index (p < 0.005). CONCLUSIONS These results strongly suggest that acoustic tumors can be subdivided into several groups, based upon different biologic activities and tumor growth rates 1).