Edema and elasticity of a fronto-temporal decompressive craniectomy

Abstract

Background: Decompressive craniectomy is undertaken for relief of brain herniation caused by acute brain swelling. Brain stiffness can be estimated by palpating the decompressive cranial defect and can provide some relatively subjective information to the neurosurgeon to help guide care. The goal of the present study was to objectively evaluate transcutaneous stiffness of the cranial defect using a tactile resonance sensor and to describe the values in patients with a decompressive window in order to characterize the clinical association between brain edema and stiffness.

Methods: Data were prospectively collected from 13 of 37 patients who underwent a decompressive craniectomy in our hospital during a 5-year period. Transcutaneous stiffness was measured as change in frequency and as elastic modulus.

Results: Stiffness variables of the decompressive site were measured without any adverse effect and subsequent calculations revealed change in frequency = 101.71 ± 36.42 Hz, and shear elastic modulus = 1.99 ± 1.11 kPa.

Conclusions: The elasticity of stiffness of a decompressive site correlated with brain edema, cisternal cerebrospinal fluid pressure, and brain shift, all of which are related to acute brain edema.

Keywords: Brain edema; decompressive craniectomy; elasticity; palpation; shear elastic modulus; tactile.

Figure 1

The tactile resonance sensor and CT parameters. (a) CT findings. Brain edema was evaluated on the basis of CT findings that included brain shift (1: CT_shift), width (2: CT_width), scalp protrusion (3: CT_scalp), dura protrusion (4: CT_dura), and swelling distance (5: SwD). (b) Use of the sensor. The tip of the hand-held probe with its guide attachment is shown. The position of the probe tip was adjusted to maintain non-pressurized contact with the skin surface by marking three footplates. The probe movement was restricted to within a depth of 3.0 mm

Figure 2

Agar phantom study. (a) The relationship between dF_maxDp and four concentrations of agar. The variance of dF-value at 5 and 10% agar was larger than that of 15 and 20% agar. (b) The relationship between G_maxDp and four concentrations of agar. The variance of G-value was smaller than that of dF-value

Figure 3

Time course of the G-value. Scattergrams of the relationship between G_maxDp and measurement day from onset are shown. Patients were divided according to (a) G_maxDp < 3.0 and (b) G_maxDp > 3.0. Patients who survived (green) and those who died (red) are depicted in the graphs of G_maxDp > 3.0. Survival was higher in patients with G < 3.0 (n = 9) than in those with G > 3.0 (n = 4)

Figure 4

Correlation between cisternal pressure and stiffness variables. Scattergrams of the relationship between stiffness variables and cisternal pressure obtained using 11 data sets from patients with subarachnoid hemorrhage in whom a drain had been placed in the basal cistern. A linear fit line was calculated. The G-values were significantly correlated with cisternal pressure. (a) The scattergram of dF_maxDp and cisternal pressure. (b) The scattergram of G_maxDp and cisternal pressure

Figure 5

Representative case. Serial changes in the features revealed by head CT and the association between edema and G-values were assessed. Therapeutic intervention was determined on the basis of CT findings, whose timing was determined using digital palpation and stiffness variables at the decompression site. G-value of number 8 was measured before cranioplasty, and the CT image shown was taken immediately after cranioplasty

Figure 6

Correlation between pressure and change in frequency. We plotted the scattergrams for the individual 35 sample data between the Pr-value and dF-value. They showed a high linear correlation in the individual data sets. (a) The chart of subgroups with G_maxDp > 3.0 is shown (n = 5). The peak Pr-value was more than 140 (gf). (b) The chart of subgroups with G_maxDp < 3.0 is shown (n = 30). The peak Pr-value was less than 160 (gf)