In the framework of competency-based education (CBE) in neurosurgery, traditional time-based milestones are replaced by objective demonstrations of skill acquisition and procedural mastery. CUSUM (Cumulative Sum) analysis offers a powerful tool to track these competencies with precision and fairness.

CUSUM analysis provides:

• Continuous, case-by-case tracking of individual surgical performance
• Real-time visualization of learning curves
• Detection of early plateaus, regressions, or accelerations in skill acquisition
• Data to support entrustment decisions and promotion through competency milestones

Rather than relying solely on supervisor impressions or fixed rotation durations, CUSUM allows for quantitative validation of surgical growth.

Each case is scored as:

• 0 = success (meets expected standard)
• 1 = failure (complication or performance below expected standard)

Using a reference value (k)—typically derived from acceptable failure rates in the literature or institutional data—CUSUM builds a performance trajectory over time.

Key applications:

• Tracking procedural competence (e.g., EVD insertion, lumbar laminectomy)
• Identifying when competence is reached (flat or declining CUSUM curve)
• Flagging when additional training is needed (rising CUSUM curve)
• Differentiating individual learning speeds and adapting supervision accordingly

• Reference complication rate (k) = 0.10
• Resident performs 20 cases:
  1. Early rising trend → additional simulation and direct supervision
  2. Plateau after case #12 → learning curve stabilizes
  3. Competency declared after 15 successful placements without new complications

• Ensures fair, data-driven evaluation of all trainees
• Promotes self-reflection and encourages ownership of learning
• Documents procedural proficiency for boards, credentialing, and promotion
• Enables structured feedback based on trends, not isolated incidents

CUSUM data can be embedded in:

• Individual learning portfolios
• Clinical Competency Committee (CCC) evaluations
• Entrustable Professional Activities (EPAs)
• Surgical logbooks with performance analytics

By aligning CUSUM with competency-based curricula, neurosurgical programs can transition from time-based progression to outcome-driven excellence. gery