Most Roads Lead to Cushing: Mapping Neurosurgical Training Lineages in the United States

Mentorship and training relationships shape the careers and influence of neurosurgeons. Network analysis can reveal structural characteristics and key individuals who support network connectivity and drive the field's development. This endeavor analyzed the US-based neurosurgical training network derived from NeurosurGen.com. A network graph was constructed representing neurosurgical training relationships, including chairperson-trainee, program director-trainee, and co-resident connections. Graph- and node-level metrics, with a focus on centrality measures, were calculated for a trainer-trainee subgraph. The network consisted of 8840 neurosurgeons represented as nodes, and 382,143 relationships represented as edges. It evolved from an early small-world structure to a hierarchical and decentralized structure dominated by local clusters. Demographic shifts over time reflected increasing diversity and inclusion, with greater representation of female, Hispanic, Asian, and Black trainees across 285 training programs. Nodes were preferentially connected via residency, and the connectivity among underrepresented populations improved in concert with increased representation. Harvey Cushing was the quintessential neurosurgeon-influencer in the US, ranking highly across most centrality measures over time. The neurosurgical training network is sparse but interconnected, typical of large real-world professional networks. While many small groups of neurosurgeons are closely tied within their immediate training hierarchy and peer group, in modern neurosurgery, each surgeon is only connected to a small fraction of the total network. Highly central individuals have played critical roles in linking disparate groups and shaping network structure. Increasing diversity in recent decades indicates progress toward inclusivity, although overall representation remains low.