Resident Physician University of Colorado Department of Neurosurgery
Introduction: Tumor Apparent Diffusion Coefficient (ADC) value on diffusion MRI has previously been shown to be correlated with postoperative House-Brackmann (HB) scores in patients with vestibular schwannoma undergoing resection. In this study, we query a relationship between ADC value and tumor volume and re-analyze the utility of ADC as a predictive value for extent of resection and clinical outcomes including facial nerve function, hearing class, hospital length of stay, and post-operative complication.
Methods: A retrospective review of patients who underwent surgical resection of vestibular schwannoma at our institution from 2014-2020 yielded 151 patients. 125 met inclusion criteria. Review of electronic medical records was performed for clinical data. MRI data including volumetric analysis and ADC values were obtained in a blinded fashion.
Results: Mean ADC value was associated with greater tumor volume (p=0.003). Tumor volume was independently predictive of lower rates of gross total resection (p < 0.0001), post-operative complication (p=0.04), and longer length of stay (p=0.003). The relationship between ADC value and hospital length of stay approached significance (p=0.09). There was no independent statistical difference in extent of resection, post-operative cranial nerve deficit, or complication by ADC value. Regression tree analysis identified 3 mean ADC categories with different average change in post-operative compared to pre-operative HB scores: >/= 1468 x 10-6 mm2/s (net change in HB = 1.46); 1000.23-1468.43 x 10-6 mm2/s (net change in HB = 1.08); and < 1000.23 x 10-6 mm2/s (net change in HB = 0.8).
Conclusion : The ranges formulated by regression tree analysis of change in HB scores are similar to those in our prior study. However here, higher range pre-operative ADC was predictive of less favorable HB outcome as well as greater tumor volume and trended toward longer hospital length of stay. Pre-operative ADC serves as an additional radiographic marker in prognosticating vestibular schwannomas being considered for surgical resection.
