Effect of Hospital Volume on Acoustic Neuroma Surgery Outcomes in the Modern Treatment Era

Background As with many complex surgical pathologies, the effect of hospital case volume of acoustic neuroma (AN) surgery on patient outcomes has previously been investigated through analyses of the National Inpatient Sample (NIS) of the late 1990s and late 2000s. In the 1990s, stereotactic radiosurgery (SRS) became an accepted treatment modality for acoustic neuromas, and since that time, the usage of this treatment option has spread across the United States, especially for smaller tumors demonstrating growth. We seek to investigate the implications of the proliferation of SRS as a treatment of acoustic neuromas in the United States on hospital surgical volume and its subsequent effect on postsurgical outcomes over time.

Methods A cohort of patients who underwent surgical resection or SRS for an AN was compiled from the Healthcare Cost and Utilization Project (HCUP) database from 2009 to 2013. States included were Iowa, Washington, New York, and Florida to collect a geographically and demographically diverse sample of the United States. Generalized linear mixed effects models were used to estimate the odds of experiencing any of five postoperative outcomes as a function of univariable and multivariable case volume and comorbidities (Charlson Comorbidity Index [CCI]). Primary outcome measures included length of stay, rate of CSF leak, facial nerve palsy, infection, and tracheostomy or gastrostomy tube placement.

Results During this time period, 6,297 patients with the primary diagnosis of AN were identified amongst 361 hospitals, including 1,638 patients who underwent surgical resection (26%) and 47 who underwent stereotactic radiosurgery (0.7%). After adjusting for CCI, at high volume centers, patients were 11% less likely to have a gastrostomy tube placed (OR: 0.89, 95% CI: 0.80–0.99, p = 0.03), marginally less likely to have a tracheostomy placed (OR: 0.82, 95% CI: 0.67–1.01, p = 0.07), or suffer from a postoperative infection (OR: 0.82, 95% CI: 0.66–1.02, p = 0.07). Length of stay was significantly decreased at high volume centers after surgical resection.

Conclusion In the modern era of AN treatment with multimodality treatment options available, hospital case volume continues to play an important role in surgical outcomes. Interestingly, although access to SRS has grown nationally, its application for this indication is not as robust as hypothesized, which is corroborated by the previously published national use of SRS for AN (565 cases) over a 12-year period (1999–2011). While the inherent limitations of a retrospective administrative database study are acknowledged, important insights into national trends can be interpreted. Given the current climate in healthcare, it is as important as ever to achieve ideal outcomes for our patients, while also taking steps toward improvements of value metrics, including decreased length of stay and complication mitigation. As there has been a push to consider focusing resources to certified high performing institutions for other complex neurosurgical pathologies, including subarachnoid hemorrhage and ischemic stroke, it may be prudent to further investigate the application of this structure to complex skull base surgery.