Burr Hole Expansion Over Time
In healthy adults, burr holes do not naturally expand over time; however, the bone defect may appear to enlarge due to bone resorption at the margins, particularly when left unfilled or when filled with autologous bone dust.
Natural History of Burr Holes
Burr holes created during neurosurgical procedures remain stable in size in most healthy adults. The cranial bone does not regenerate to close these defects spontaneously after skeletal maturity. However, the appearance of enlargement can occur through edge resorption rather than true expansion 1.
Factors Affecting Burr Hole Size Over Time
Bone Resorption with Autologous Bone Dust
When burr holes are filled with autologous bone dust from skull trephination, partial or complete bone resorption occurs at 1 year in most cases, with 60% of patients developing visible and palpable cranial vault contour irregularities 1. This creates the clinical impression of an enlarging defect, though it represents material loss rather than hole expansion.
Synthetic Materials Provide Stability
Hydroxyapatite plugs demonstrate superior outcomes compared to autologous bone dust, with better maintenance of thickness and esthetic appearance at 12 months 1. These materials resist resorption and prevent the appearance of defect enlargement.
Special Populations and Conditions
Children
In pediatric patients, burr holes may demonstrate different behavior due to ongoing skull growth and remodeling. The diploe can generate granulation tissue when exposed through multiple trephinations, as demonstrated in scalp avulsion cases 2. However, this represents wound healing rather than hole expansion.
Pathological Conditions That May Affect Burr Holes
- Infection: Can cause bone destruction and apparent enlargement
- Poor wound healing: May lead to bone edge necrosis and defect widening
- Extensive scalp burns: Require careful wound management to prevent complications, though the burr hole itself remains stable 3
Clinical Implications
For optimal cosmetic and structural outcomes, consider using porous hydroxyapatite plugs rather than leaving burr holes unfilled or using autologous bone dust 1. This prevents the appearance of enlargement through edge resorption and provides superior patient satisfaction.
Common Pitfalls
- Assuming unfilled burr holes will remain cosmetically acceptable long-term
- Using autologous bone dust expecting permanent fill when resorption is the norm
- Failing to counsel patients about potential contour irregularities at 1 year
The evidence clearly demonstrates that while burr holes themselves do not actively expand, the clinical appearance of enlargement results from resorption of filling materials or bone edges, not from growth of the defect itself 1.