Fenestration of bone flap during decompressive craniotomy for subdural hematoma

Persistent/recurrent extra-axial hemorrhage may occur after decompression of a subdural hematoma (SDH) followed by an immediate replacement of bone flap. A fenestration of the bone flap may encourage extra-axial fluid absorption; however, the literature has not explored this technique.

Forty-four consecutive patients who underwent surgical decompression of SDH with immediate replacement of bone flap were divided into two groups: Fenestration (F), n = 33, and no fenestration (NF), n = 11. Fenestration involves placement of twist drill holes 1-2 cm apart throughout the bone flap. Clinical data (age, sex, history of antiplatelet/anticoagulation [AA], and presence of drains) were collected. The size of bone flap, postoperative volume, and midline shift (MLS) were measured. A univariate analysis was performed for continuous variables; Fisher's exact test was performed for categorical variables.

For postoperative volume, NF group exhibited 94.4 ± 15.5 cm(3), while F group exhibited 47.3 ± 15.5 cm(3) (P = 0.04); no AA exhibited 62.9 ± 12.3 cm(3), while AA exhibited 100.5 ± 19.0 cm(3) (P = 0.07); no drains exhibited 110.1 ± 29.6 cm(3), while drains exhibited 63.0 ± 9.1 cm(3) (P = 0.14). For postoperative MLS, NF group exhibited 4.8 ± 1.1 mm, while F group exhibited 2.5 ± 1.1 mm (P = 0.16); no AA exhibited 2.3 ± 1.0 mm, while AA exhibited 5.8 ± 1.4 mm (P = 0.048); no drains exhibited 4.6 ± 2.2 mm, while drains exhibited 3.8 ± 0.7 mm (P = 0.70). Accounting for fenestration status and AA status: For F group, AA status did not correlate with postoperative volume or MLS significantly; for NF group, history of AA exhibited higher postoperative value 129.2 ± 26.5 cm(3), compared to no history of AA at 59.5 ± 16.2 cm(3) (P = 0.03).

Our results suggest that fenestration prior to the immediate replacement of bone flap after surgical decompression of SDH has the potential to reduce extra-axial fluid accumulation.