Background and purpose A recent expansion of the neurointerventional workforce in the USA could lead to a trend toward cerebral aneurysms being increasingly treated at low volume centers. Such a trend could have a negative impact on patient care as higher volume centers are known to have better outcomes.

Methods Using the Nationwide Inpatient Sample, we evaluated trends in aneurysm treatment in the USA from 2001 to 2010. Annual volumes of both ruptured and unruptured aneurysms were counted, as well as annual percentages of cases treated at high volume centers (≥50 aneurysms/year clipped or coiled).

Results The number of ruptured aneurysms treated per year has fluctuated between 9000 and 12 000 from 2003 to 2010. In 2001–2002, 27.4% of intracranial aneurysm patients were treated with clipping or coiling at high volume centers, with a peak of 70.1% in 2007–2008. This proportion dropped to 61.8% in 2009–2010. The proportion of patients clipped at high volume centers was 23.3% in 2001–2002 and peaked at 65.0% in 2007–2008. In 2009–2010, the proportion dropped to 58.6%. For coiling patients, 46.4% were treated at high volume centers in 2001–2002, with a peak of 70.1% in 2007–2008, and a drop to 61.8% in 2009–2010.

Conclusion A trend toward less cerebral aneurysms being treated in high volume centers in 2009 and 2010 is worrisome because high volume centers are known to tend to have better outcomes. This trend is likely due to recent expansion of the neurointerventional workforce.