Decompressive craniectomy is indispensible in the management of severe traumatic brain injury

Evaluation of decompressive craniectomy in mice after severe traumatic brain injury

Decompressive craniectomy (DC) is of great significance for relieving acute intracranial hypertension and saving lives after traumatic brain injury (TBI). In this study, a severe TBI mouse model was created using controlled cortical impact (CCI), and a surgical model of DC was established. Furthermore, a series of neurological function assessments were performed to better understand the pathophysiological changes after DC. In this study, mice were randomly allocated into three groups, namely, CCI group, CCI+DC group, and Sham group. The mice in the CCI and CCI+DC groups received CCI after opening a bone window, and after brain injury, immediately returned the bone window to simulate skull condition after a TBI. The CCI+DC group underwent DC and contused tissue removal 6 h after CCI. The mice in the CCI group underwent the same anesthesia process; however, no further treatment of the bone window and trauma was performed. The mice in the Sham group underwent anesthesia and the process of opening the skin and bone window, but not in the CCI group. Changes in Modified Neurological Severity Score, rotarod performance, Morris water maze, intracranial pressure (ICP), cerebral blood flow (CBF), brain edema, blood–brain barrier (BBB), inflammatory factors, neuronal apoptosis, and glial cell expression were evaluated. Compared with the CCI group, the CCI+DC group had significantly lower ICP, superior neurological and motor function at 24 h after injury, and less severe BBB damage after injury. Most inflammatory cytokine expressions and the number of apoptotic cells in the brain tissue of mice in the CCI+DC group were lower than in the CCI group at 3 days after injury, with markedly reduced astrocyte and microglia expression. However, the degree of brain edema in the CCI+DC group was greater than in the CCI group, and neurological and motor functions, as well as spatial cognitive and learning ability, were significantly poorer at 14 days after injury.

Modelling of Brain Deformation After Decompressive Craniectomy

Hyperelastic finite element models, with either an idealized cylindrical geometry or with realistic craniectomy geometries, were used to explore clinical issues relating to decompressive craniectomy. The potential damage in the brain tissue was estimated by calculating the volume of material exceeding a critical shear strain. Results from the idealized model showed how the potentially damaged volume of brain tissue increased with an increasing volume of brain tissue herniating from the skull cavity and with a reduction in craniectomy area. For a given herniated volume, there was a critical craniectomy diameter where the volume exceeding a critical shear strain fell to zero. The effects of details at the craniectomy edge, specifically a fillet radius and a chamfer on the bone margin, were found to be relatively slight, assuming that the dura is retained to provide effective protection. The location in the brain associated with volume expansion and details of the material modeling were found to have a relatively modest effect on the predicted damage volume. The volume of highly sheared material in the realistic models of the craniectomy varied roughly in line with differences in the craniectomy area.

Decompressive craniectomy in severe traumatic brain injury: prognostic factors and complications

OBJECTIVE

To analyze the clinical characteristics, complications and factors associated with the prognosis of severe traumatic brain injury among patients who undergo a decompressive craniectomy.

METHODS

Retrospective study of patients seen in an intensive care unit with severe traumatic brain injury in whom a decompressive craniectomy was performed between the years 2003 and 2012. Patients were followed until their discharge from the intensive care unit. Their clinical-tomographic characteristics, complications, and factors associated with prognosis (univariate and multivariate analysis) were analyzed.

RESULTS

A total of 64 patients were studied. Primary and lateral decompressive craniectomies were performed for the majority of patients. A high incidence of complications was found (78% neurological and 52% nonneurological). A total of 42 patients (66%) presented poor outcomes, and 22 (34%) had good neurological outcomes. Of the patients who survived, 61% had good neurological outcomes. In the univariate analysis, the factors significantly associated with poor neurological outcome were postdecompressive craniectomy intracranial hypertension, greater severity and worse neurological state at admission. In the multivariate analysis, only postcraniectomy intracranial hypertension was significantly associated with a poor outcome.

CONCLUSION

This study involved a very severe and difficult to manage group of patients with high morbimortality. Intracranial hypertension was a main factor of poor outcome in this population.

A new improved method for assessing brain deformation after decompressive craniectomy

Background

Decompressive craniectomy (DC) is a surgical intervention used following traumatic brain injury to prevent or alleviate raised intracranial pressure. However the clinical effectiveness of the intervention remains in doubt. The location of the craniectomy (unilateral or bifrontal) might be expected to change the brain deformation associated with the operation and hence the clinical outcome. As existing methods for assessing brain deformation have several limitations, we sought to develop and validate a new improved method.

Methods

Computed tomography (CT) scans were taken from 27 patients who underwent DC (17 bifrontal patients and 10 unilateral patients). Pre-operative and post-operative images were processed and registered to determine the change in brain position associated with the operation. The maximum deformation in the herniated brain, the change in volume and estimates of the craniectomy area were determined from the images. Statistical comparison was made using the Pearson’s correlation coefficient r and a Welch’s two-tailed T-test, with statistical significance reported at the 5% level.

Results

There was a reasonable correlation between the volume increase and the maximum brain displacement (r = 0.64), a low correlation between the volume increase and the craniectomy area (r = 0.30) and no correlation between the maximum displacement and the craniectomy area (r = −0.01). The maximum deformation was significantly lower (P  = 0.023) in the bifrontal patients (mean = 22.5 mm) compared with the unilateral patients (mean = 29.8 mm). Herniation volume was significantly lower (P = 0.023) in bifrontal (mean = 50.0 ml) than unilateral patients (mean = 107.3 ml). Craniectomy area was not significantly different for the two craniectomy locations (P = 0.29).

Conclusions

A method has been developed to quantify changes in brain deformation due to decompressive craniectomy from CT images and allow comparison between different craniectomy locations. Measured displacement is a reasonable way to characterise volume changes.

Decompressive craniectomy for severe traumatic brain injury: the relationship between surgical complications and the prediction of an unfavourable outcome

OBJECT

To assess the impact that injury severity has on complications in patients who have had a decompressive craniectomy for severe traumatic brain injury (TBI).

METHODS

This prospective observational cohort study included all patients who underwent a decompressive craniectomy following severe TBI at the two major trauma hospitals in Western Australia from 2004 to 2012. All complications were recorded during this period. The clinical and radiological data of the patients on initial presentation were entered into a web-based model prognostic model, the CRASH (Corticosteroid Randomization After Significant Head injury) collaborators prediction model, to obtain the predicted risk of an unfavourable outcome which was used as a measure of injury severity.

RESULTS

Complications after decompressive craniectomy for severe TBI were common. The predicted risk of unfavourable outcome was strongly associated with the development of neurological complications such as herniation of the brain outside the skull bone defects (median predicted risk of unfavourable outcome for herniation 72% vs. 57% without herniation, p=0.001), subdural effusion (median predicted risk of unfavourable outcome 67% with an effusion vs. 57% for those without an effusion, p=0.03), hydrocephalus requiring ventriculo-peritoneal shunt (median predicted risk of unfavourable outcome 86% for those with hydrocephalus vs. 59% for those without hydrocephalus, p=0.001), but not infection (p=0.251) or resorption of bone flap (p=0.697) and seizures (0.987). We did not observe any associations between timing of cranioplasty and risk of infection or resorption of bone flap after cranioplasty.

CONCLUSIONS

Mechanical complications after decompressive craniectomy including herniation of the brain outside the skull bone defects, subdural effusion, and hydrocephalus requiring ventriculo-peritoneal shunt were more common in patients with a more severe form of TBI when quantified by the CRASH predicted risk of unfavourable outcome. The CRASH predicted risk of unfavourable outcome represents a useful baseline characteristic of patients in observational and interventional trials involving patients with severe TBI requiring decompressive craniectomy.

The influence of clinical evidence on surgical practice

Given the considerable interest in the use of evidence-based medicine to guide clinical practice, it is surprising that the results of a recent randomized controlled trial have been met with such a limited response. The DECompressive CRAniectomy study investigators have recently published the results of a landmark trial in neurosurgery, comparing early decompressive craniectomy with standard medical therapy in patients who developed intracranial hypertension after diffuse closed traumatic brain injury (TBI). This is the first ever randomized controlled trial investigating the surgical management of adult patients with severe TBI. The trial clearly demonstrated that early decompression did not provide clinical benefit; however, rather than having a significant impact on clinical practice, it has been almost uniformly criticized. While there were some problems with randomization and crossover, we feel that the trial has been somewhat misinterpreted and in this article we address some of the key issues.

Organic bioelectrodes in clinical neurosurgery

BACKGROUND

Clinical neurosurgery deals with surgical procedures and intensive care of illnesses in the human central and peripheral nervous system. Neurosurgery should be looked upon as a high-tech specialty and very much dependent on new technological innovations aiming at improvements of patient's treatment and outcome. During the last decades neurosurgery has improved substantially thanks to the introduction of applied imaging technologies such as computerized tomography and magnetic resonance tomography, and new surgical modalities such as the microscope, brain navigation and neuroanesthesiology. Neurosurgical disorders, which should have the potential to benefit from conductive organic bioelectrodes, include traumatic brain and spinal cord injury and peripheral nerve injuries due to external violence in the restoration of healthy communication. This holds true also for cerebral nerves altered in their functions due to benign and malignant brain and spinal cord tumors. Further, new innovative devices in the field of functional nervous tissue disorders make the use of organic conductive electrodes attractive by considering the electrical neurochemical properties of neural interfaces.

CONCLUSIONS

Although in its infancy, conducting organic polymers as bioelectrodes have several potential applications in clinical neurosurgery. The time it takes for new innovations and basic research to be transferred into clinical neurosurgery should not take too long. However, a prerequisite for successful implementation is the close interdisciplinary collaboration between engineers and clinicians. This article is part of a Special Issue entitled Organic Bioelectronics-Novel Applications in Biomedicine.

What can be learned from the DECRA study

BACKGROUND

There has been a resurgence of interest in the use of decompressive craniectomy for severe traumatic brain injury (TBI). Numerous studies have shown that the procedure can consistently reduce intracranial pressure (ICP), and a significant number of patients achieve a good long-term functional recovery. However, there has been debate regarding clinical indications and patient selection.

METHODS

The DECRA (Decompressive Craniectomy in Patients with Severe Traumatic Brain Injury) study compared patients who underwent early decompressive craniectomy for diffuse TBI with patients who received standard medical therapy. Of patients, 70% in the craniectomy group had an unfavourable outcome versus 51% in the standard care group (odds ratio 2.21 [95% confidence interval 1.14-4.26]; P=0.02). Based on these results, the authors concluded that decompressive craniectomy was associated with more unfavorable outcomes and that by adopting standard medical therapy rather than surgical decompression the health care system would save millions of dollars. These conclusions are not really supported by closer examination of the basic data. There were problems with randomization such that the patients in the surgical arm appeared to have sustained a more severe primary TBI, the ICP threshold of >20 mm Hg for >15 minutes did not reflect clinical practice, and there was a high crossover rate from the standard care arm to the surgical arm. Because of these problems, the DECRA trial has received a great deal of criticism, and some authorities have claimed that the results should have no influence on clinical practice. This claim is perhaps unfair, and an alternative interpretation is offered.

RESULTS

Overall, the results of the DECRA study showed that a relatively transient and mild increase in ICP (>20 mm Hg for 15 minutes as recruitment criterion) does not imply that there is significant ongoing secondary brain injury, and any potential improvement obtained by surgical decompression may well be offset by surgical morbidity.

CONCLUSIONS

The role of decompressive craniectomy when ICP continues to increase ≥20 mm Hg remains to be established. The ongoing RESCUEicp (Randomised Evaluation of Surgery with Craniectomy for Uncontrollable Elevation of Intra-Cranial Pressure) study hopes to address this issue.

Increased strain levels and water content in brain tissue after decompressive craniotomy

BACKGROUND

At present there is a debate on the effectiveness of the decompressive craniotomy (DC). Stretching of axons was speculated to contribute to the unfavourable outcome for the patients. The quantification of strain level could provide more insight into the potential damage to the axons. The aim of the present study was to evaluate the strain level and water content (WC) of the brain tissue for both the pre- and post-craniotomy period.

METHODS

The stretching of brain tissue was quantified retrospectively based on the computerised tomography (CT) images of six patients before and after DC by a non-linear image registration method. WC was related to specific gravity (SG), which in turn was related to the Hounsfield unit (HU) value in the CT images by a photoelectric correction according to the chemical composition of brain tissue.

RESULTS

For all the six patients, the strain level showed a substantial increase in the brain tissue close to the treated side of DC compared with that found at the pre-craniotomy period and ranged from 24 to 55 % at the post-craniotomy period. Increase of strain level was also observed at the brain tissue opposite to the treated side, however, to a much lesser extent. The mean area of craniotomy was found to be 91.1 ± 12.7 cm(2). The brain tissue volume increased from 27 to 127 ml, corresponding to 1.65 % and 8.13 % after DC in all six patients. Also, the increased volume seemed to correlate with increased strain level. Specifically, the overall WC of brain tissue for two patients evaluated presented a significant increase after the treatment compared with the condition seen before the treatment. Furthermore, the Glasgow Coma Scale (GCS) improved in four patients after the craniotomy, while two patients died. The GCS did not seem to correlate with the strain level.

CONCLUSIONS

We present a new numerical method to quantify the stretching or strain level of brain tissue and WC following DC. The significant increase in strain level and WC in the post-craniotomy period may cause electrophysiological changes in the axons, resulting in loss of neuronal function. Hence, this new numerical method provides more insight of the consequences following DC and may be used to better define the most optimal size and area of the craniotomy in reducing the strain level development.