Simulating Expansion of the Intracranial Space to Accommodate Brain Swelling after Decompressive Craniectomy: Volumetric Quantification in a 3D CAD Skull Model with Contour Elevation

Abstract

Background: Decompressive craniectomy (DC) can be used to augment intracranial space and halt brainstem compromise. However, a widely adopted recommendation for optimal surgical extent of the DC procedure is lacking. In the current study, we utilized three-dimensional (3D) computer-assisted design (CAD) skull models with defect contour elevation for quantitative assessment. Methods: DC was performed for 15 consecutive patients, and 3D CAD models of defective skulls with contour elevations (0–50 mm) were reconstructed using commercial software. Quantitative assessments were conducted in these CAD subjects to analyze the effects of volumetric augmentation when elevating the length of the contour and the skull defect size. The final positive results were mathematically verified using a computerized system for numerical integration with the rectangle method. Results: Defect areas of the skull CAD models ranged from 55.7–168.8 cm2, with a mean of 132.3 ± 29.7 cm2. As the contour was elevated outward for 6 mm or above, statistical significance was detected in the volume and the volume-increasing rate, when compared to the results obtained from the regular CAD model. The volume and the volume-increasing rate increased by 3.665 cm3, 0.285% (p < 0.001) per 1 mm of contour elevation), and 0.034% (p < 0.001) per 1 cm2 of increase of defect area, respectively. Moreover, a 1 mm elevation of the contour in Groups 2 (defect area 125–150 cm2) and 3 (defect area >150 cm2, as a proxy for an extremely large skull defect) was shown to augment the volume and the volume-increasing rate by 1.553 cm3, 0.101% (p < 0.001) and 1.126 cm3, 0.072% (p < 0.001), respectively, when compared to those in Group 1 (defect area <125 cm2). The volumetric augmentation achieved by contour elevation for an extremely large skull defect was smaller than that achieved for a large skull defect. Conclusions: The 3D CAD skull model contour elevation method can be effectively used to simulate the extent of a space-occupying swollen brain and to quantitatively assess the extent of brainstem protection in terms of volume augmentation and volume-increasing rate following DC. As the tangential diameter (representing the degree of DC) exceeded the plateau value, volumetric augmentation was attenuated. However, an increasing volumetric augmentation was detected before the plateau value was reached.

Comparison of Brain Volume Increase in Patients with Intracranial Hypertension after Decompressive Craniotomy and Augmentative Craniotomy

“…The larger volume increase observed post-AC could be attributed to several factors 10 . One key factor is the reduced elastic tension exerted by the soft tissues (skin and temporalis muscle) on the dura mater in AC.…”

Development of a Novel Device for Decompressive Craniectomy: An Experimental and Cadaveric Study and Preliminary Clinical Application

“…The amount of lifting required to ensure adequate intracranial volume expansion was derived by taking into account data collected from both a series of clinical cases (unpublished data) and the literature. [9][10][11][12] Clinical studies have shown that an expansion of the brain parenchyma of at least 5 mm, which allowed for an average herniation volume of 39.5 ± 23.6 mL, is sufficient to reduce intracranial pressure in cases of DC for malignant middle cerebral artery cerebral ischemia and traumatic brain injury. 11,12 We also analyzed our case series of patients who underwent DC and found similar values of brain herniation (not yet published data).…”