Determination of the clinical growth index in unilateral vestibular schwannoma.

OBJECTIVES: To analyze factors associated with the clinical growth index of sporadic unilateral vestibular schwannoma and to evaluate the validity of the index as an indicator of tumor growth.
DESIGN: A retrospective case review study. PATIENTS AND METHODS: A series of 118 patients with unilateral vestibular schwannomas. Clinical growth index was calculated by dividing tumor size by the length of clinical history. Clinical growth index, tumor size, symptoms, and symptom duration were tested for a relationship with tumor location, patient sex, and age. All tests were performed for the total group and separately for three subgroups: intrameatal tumors (IT group, n = 46), intrameatal and extrameatal tumors (IET group, n = 60), and extrameatal tumors (ET group, n = 12).
RESULTS: Vestibular schwannoma diameter ranged from 3 to 40 mm (mean size, 14.3 +/- 7.6 mm). The maximum tumor diameter was significantly greater for the IET group (17.9 +/- 6.5 mm) and the ET group (19.3 +/- 8.5 mm) than for the IT group (8.5 +/- 4.3 mm) (p < 0.001). The mean clinical growth index was determined as being 31.3 +/- 55.7 mm/yr for the total group. A significantly lower clinical growth index was found for the IT group (14.7 +/- 25.3 mm/yr) compared with the IET group (41.9 +/- 69.2 mm/yr) and the ET group (43.3 +/- 52.4 mm/yr) (p = 0.031). A significantly negative correlation between the clinical growth index and the age of the patients was noted for both the total group (p = 0.010) and the IET group (p = 0.017). A significantly negative correlation between the tumor size and the age of the patients was determined for the ET group (p = 0.22).
CONCLUSIONS: This study demonstrates a lower clinical growth index and smaller tumors in the older population, supporting data previously presented by extensive radiological studies. Our findings might provide a rationale for the consideration of the clinical growth index to estimate vestibular schwannoma growth rate.