Does Size and Site Matter in Therapeutic Decompressive Craniectomy? A Laboratory-Based Experimental Study

BACKGROUND: Therapeutic decompressive craniectomy (TDC) controls increased intracranial pressure (ICP). Its role was controversial until its successful introduction to treat malignant middle cerebral artery ischemia. However, standardization of size and site of TDC remains controversial. This study was designed to evaluate whether size and site matter in TDC. METHODS: A replica skull of a patient with refractory increased ICP and successful TDC was used. ICP was increased using an intracranial balloon modified to monitor ICP and permit progressive incremental increases in ICP. When a desired increased ICP was reached, segments of TDC were removed sequentially to increase its size until the ICP normalized. We also measured the volume of air required to raise the ICP back to the increased ICP value. RESULTS: The most effective TDC size to lower increased ICP was 8.3 cm in diameter (P < 0.001). However, a 7.5-cm TDC was sufficient to control increased ICP of 25-30 mm Hg (P < 0.01). There was strong correlation between TDC size and potential volume created to accommodate brain swelling postoperatively (Pearson correlation coefficient = 0.95928). The location of TDC did not matter when size was <= 3.5 cm or >= 7.5 cm; location mattered when size was 4.5 cm or 5.5 cm, where anteriorly located flaps were more effective in lowering increased ICP and increasing cranial volume (P < 0.05). CONCLUSIONS: The size of a TDC is very important in reducing increased ICP. The size should be tailored to the level of increased ICP and the likelihood of further brain swelling postoperatively. A smaller TDC should be located more anteriorly to control increased ICP. Although location is not as important when increased ICP is > 30 mm Hg and TDC size >= 8.3 cm is required.