Decompressive craniectomy: past, present and future

Decompressive craniectomy (DC)--a surgical procedure that involves removal of part of the skull to accommodate brain swelling--has been used for many years in the management of patients with brain oedema and/or intracranial hypertension, but its place in contemporary practice remains controversial. Results from a recent trial showed that early (neuroprotective) DC was not superior to medical management in patients with diffuse traumatic brain injury. An ongoing trial is investigating the clinical and cost effectiveness of secondary DC as a last-tier therapy for post-traumatic refractory intracranial hypertension. With regard to ischaemic stroke (malignant middle cerebral artery infarction), a recent Cochrane review concluded that DC improves survival compared with medical management, but that a higher proportion of DC survivors experience moderately severe or severe disability. Although many patients have a good outcome, the issue of DC-related disability raises important ethical issues. As DC and subsequent cranioplasty are associated with a number of complications, indiscriminate use of this surgery is not appropriate. Here, we review the evidence and present considerations regarding surgical technique, ethics and cost-effectiveness of DC. Prospective clinical trials and cohort studies are essential to enable optimization of patient care and outcomes.

Stenting venous outflow gives symptomatic improvement in a patient with an inoperable brainstem arteriovenous malformation

The extent to which arterial steal or venous hypertension contributes to symptoms in patients with high flow brain arteriovenous malformations (AVMs) is not always clear. We describe a patient with an inoperable AVM of the pons, presenting with headache and neurological deficit where improving venous outflow by stenting produced substantial clinical benefit.

Cerebral autoregulation after subarachnoid hemorrhage: comparison of three methods

In patients after subarachnoid hemorrhage (SAH) failure of cerebral autoregulation is associated with delayed cerebral ischemia (DCI). Various methods of assessing autoregulation are available, but their predictive values remain unknown. We characterize the relationship between different indices of autoregulation. Patients with SAH within 5 days were included in a prospective study. The relationship between three indices of autoregulation was analyzed: two indices calculated using spontaneous blood pressure fluctuations, Sxa (based on transcranial Doppler) and TOxa (based on near-infrared spectroscopy); and transient hyperemic response test (THRT) where a brief compression of the common carotid artery is used. The predictive value of indices was assessed using data from the first 5 days. Overall there was only moderate correlation between indices. However, both Sxa and TOxa showed good accuracy in predicting impaired autoregulation evidenced by a negative THRT (area under the curve (AUC): 0.788, 95% CI: 0.723 to 0.854 and AUC: 0.827, 95% CI: 0.769 to 0.885, respectively). All indices proved accurate in predicting DCI when 0- to 5-day data were used (AUC: 0.801, 95% CI: 0.660 to 0.942; AUC: 0.857, 95% CI: 0.731 to 0.984, AUC: 0.796, 95% CI: 0.658 to 0.934 for THRT, Sxa, and TOxa, respectively). Combining all three indices had 100% specificity for predicting DCI. While multiple colinearities exist between the assessed methods, multimodal monitoring of cerebral autoregulation can aid in predicting DCI.

Monitoring cerebral autoregulation after head injury. Which component of transcranial Doppler flow velocity is optimal?

BACKGROUND

Cerebral autoregulation assessed using transcranial Doppler (TCD) mean flow velocity (FV) in response to various physiological challenges is predictive of outcome after traumatic brain injury (TBI). Systolic and diastolic FV have been explored in other diseases. This study aims to evaluate the systolic, mean and diastolic FV for monitoring autoregulation and predicting outcome after TBI.

METHODS

300 head-injured patients with blood pressure (ABP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), and FV recordings were studied. Autoregulation was calculated as a correlation of slow changes in diastolic, mean and systolic components of FV with CPP (Dx, Mx, Sx, respectively) and ABP (Dxa, Mxa, Sxa, respectively) from 30 consecutive 10 s averaged values. The relationship with age, severity of injury, and dichotomized 6 months outcome was examined.

RESULTS

Association with outcome was significant for Mx and Sx. For favorable/unfavorable and death/survival outcomes Sx showed the strongest association (F = 20.11; P = 0.00001 and F = 13.10; P = 0.0003, respectively). Similarly, indices derived from ABP demonstrated the highest discriminatory value when systolic FV was used (F = 12.49; P = 0.0005 and F = 5.32; P = 0.02, respectively). Indices derived from diastolic FV demonstrated significant differences (when calculated using CPP) only when comparing between fatal and non-fatal outcome.

CONCLUSIONS

Systolic flow indices (Sx and Sxa) demonstrated a stronger association with outcome than the mean flow indices (Mx and Mxa), irrespective of whether CPP or ABP was used for calculation.

Impairment of cerebral autoregulation predicts delayed cerebral ischemia after subarachnoid hemorrhage: a prospective observational study

BACKGROUND AND PURPOSE

Delayed cerebral ischemia (DCI) is a recognized contributor to unfavorable outcome after subarachnoid hemorrhage (SAH). Recent data challenge the concept of vasospasm as the sole cause of ischemia and suggest a multifactorial process with dysfunctional cerebral autoregulation as a component. We tested the hypothesis that early autoregulatory failure, detected using near-infrared spectroscopy-based index, TOxa and transcranial Doppler-based index, Sxa, can predict DCI.

METHODS

In this prospective observational study we enrolled consecutive patients with aneurysmal SAH that occurred <5 days from admission. The primary end point was the occurrence of DCI within 21 days of ictus. The predictive value of autoregulatory disturbances detected in the first 5 days was assessed using univarate proportional hazards model and a multivariate model.

RESULTS

Ninety-eight patients were included. Univariate analysis demonstrated increased odds of developing DCI when early autoregulation failure was detected (odds ratio [OR], 7.46; 95% confidence interval [CI], 3.03-18.40 and OR, 4.52; 95% CI, 1.84-11.07 for Sxa and TOxa, respectively) but not TCD-vasospasm (OR, 1.36; 95% CI, 0.56-3.33). In a multivariate model Sxa and TOxa remained independent predictors of DCI (OR, 12.66; 95% CI, 2.97-54.07 and OR, 5.34; 95% CI, 1.25-22.84 for Sxa and TOxa, respectively).

CONCLUSIONS

Disturbed autoregulation in the first 5 days after SAH significantly increases the risk of DCI. Autoregulatory disturbances can be detected using near-infrared spectroscopy and transcranial Doppler technologies.

Outcome following evacuation of acute subdural haematomas: a comparison of craniotomy with decompressive craniectomy

BACKGROUND

Acute subdural haematomas (ASDH) occur commonly following traumatic brain injury and may be evacuated by either craniotomy (CR) or decompressive craniectomy (DC). We reviewed a series of consecutive patients undergoing evacuation of a traumatic ASDH at a regional centre, comparing observed clinical outcomes (assessed by Glasgow Outcome Scale at six months) with those predicted by the CRASH-CT prognostic model.

METHODS

Retrospective review of prospectively collected data.

RESULTS

Ninety-one patients were identified (51 DC and 40 CR ). Eighty-five had available admission data sets from which predicted outcome could be calculated. The DC group were younger than the CR group (p = 0.015). The DC group also had a greater proportion of patients whose pre-intubation GCS was ≤8 (p = 0.001), with significant extracranial injuries (p = 0.001) and obliterated basal cisterns (p = 0.001) on their pre-operative CT scan. Bone flaps in the DC group (n = 45) were longer (mean 11.6 cm; 95 % CI: 11.1-12.1) in comparison to bone flaps in the CR (n = 34) group [(mean 10.2 cm; 95 % CI: 9.35 - 10.9); p = 0.0024] The mean CRASH-CT predicted risk of 14-day mortality and of unfavourable outcome at six months was significantly higher in the DC group compared with the CR group. Eighty-eight patients had available 6-month Glasgow Outcome Scale scores. Favourable outcomes were observed in 42 % of DC versus 45 % of CR (p = 0.83). The overall mortality rate was 38 % in DC versus 32 % in CR (p = 0.65). The standardised morbidity ratio (observed/expected unfavourable outcomes) was 0.75 (95 % CI: 0.51-1.07) for DC and 0.90 (95 % CI: 0.57-1.35) for CR.

CONCLUSIONS

CR and DC for traumatic ASDH are both commonly used for primary evacuation of ASDH. Primary DC may be more effective than CR for selected patients with ASDH. Class I evidence is required in order to refine the indications for DC following evacuation of ASDH.

The relationship between cerebral blood flow autoregulation and cerebrovascular pressure reactivity after traumatic brain injury

BACKGROUND

Cerebrovascular pressure reactivity is the principal mechanism of cerebral autoregulation. Assessment of cerebral autoregulation can be performed by using the mean flow index (Mx) based on transcranial Doppler ultrasonography. Cerebrovascular pressure reactivity can be monitored by using the pressure reactivity index (PRx), which is based on intracranial pressure monitoring. From a practical point of view, PRx can be monitored continuously, whereas Mx can only be monitored in short periods when transcranial Doppler probes can be applied.

OBJECTIVE

To assess to what degree impairment in pressure reactivity (PRx) is associated with impairment in cerebral autoregulation (Mx).

METHODS

A database of 345 patients with traumatic brain injury was screened for data availability including simultaneous Mx and PRx monitoring. Absolute differences, temporal changes, and association with outcome of the 2 indices were analyzed.

RESULTS

A total of 486 recording sessions obtained from 201 patients were available for analysis. Overall a moderate correlation between Mx and PRx was found (r = 0.58; P < .001). The area under the receiver operator characteristic curve designed to detect the ability of PRx to predict impaired cerebral autoregulation was 0.700 (95% confidence interval: 0.607-0.880). Discrepancies between Mx and PRx were most pronounced at an intracranial pressure of 30 mm Hg and they were significantly larger for patients who died (P = .026). Both Mx and PRx were significantly lower at day 1 postadmission in patients who survived than in those who died (P < .01).

CONCLUSION

There is moderate agreement between Mx and PRx. Discrepancies between Mx and PRx are particularly significant in patients with sustained intracranial hypertension. However, for clinical purposes, there is only limited interchangeability between indices.

The SILVER (Silver Impregnated Line Versus EVD Randomized Trial)

BACKGROUND:

Cerebrospinal fluid (CSF) infections associated with external ventricular drain (EVD) placement attract major consequences. Silver impregnation of catheters attempts to reduce infection.

OBJECTIVE:

To assess the efficacy of silver catheters against CSF infection.

METHODS:

We performed a randomized, controlled trial involving 2 neurosurgical centers (June 2005 to September 2009). A total of 356 patients requiring an EVD were assessed for eligibility; 325 patients were enrolled and randomized (167 plain, 158 silver); 278 patients were analyzed (140 plain, 138 silver). The primary outcome measure was CSF infection as defined by organisms seen on Gram stain or isolated by culture. Secondary outcome measures included ventriculoperitoneal (VP) shunting.

RESULTS:

There was a significant difference in infection risk between the 2 study arms: 21.4% (30/140) for plain catheters vs 12.3% (17/138) for silver catheters (P = .0427; 95% confidence interval [CI]: 1.015-3.713). Patients who had an EVD infection had more than double the risk of requiring a VP shunt compared with patients without an EVD infection (45.7% [21/46] vs 19.7% [45/229], respectively, P = .0002; 95% CI: 1.766-6.682). There was also a significant difference in VP shunt risk with infection: plain (55.2%; 16/29) vs the silver arm (29.4%; 5/17); P = .0244 (95% CI: 1.144-11.695). A multivariate analysis demonstrated that infection risk was increased by duration of EVD placement (odds ratio: 1.160), spontaneous intracranial hemorrhage (odds ratio 4.958) and decreased by silver catheters (odds ratio: 0.423).

CONCLUSION:

The study provides Class I evidence that silver-impregnated catheters reduce CSF infection.

Vasospasm shortens cerebral arterial time constant

BACKGROUND

Cerebrovascular time constant (τ) estimates how fast cerebral blood arrives in cerebral arterial bed after each heart stroke. We investigate the pattern of changes in τ following subarachnoid hemorrhage (SAH), with specific emphasis on the temporal profile of changes in relation to the development of cerebral vasospasm.

METHODS

Simultaneous recordings of arterial blood pressure (ABP) and transcranial Doppler (TCD) blood flow velocity (CBFV) in MCA were performed daily in patients after SAH. In 22 patients (10 males and 12 females; median age: 48 years, range: 34-84 years) recordings done before spasm were compared to those done during spasm. Vasospasm was confirmed with TCD (mean CBFV in MCA > 120 cm/s and Lindegaard ratio > 3). τ was estimated as a product of compliance of cerebral arteries (C (a)) and cerebrovascular resistance (CVR). C (a) and CVR were estimated using mathematical transformations of ABP and CBFV waveforms.

RESULTS

Vasospasm caused shortening of τ on both the spastic (before: 0.20 ± 0.05 s vs. spasm: 0.14 ± 0.04 s, P < 0.0008) and contralateral side (before: 0.22 ± 0.05 s vs. spasm: 0.16 ± 0.04 s, P < 0.0008). Before TCD signs of vasospasm were detected, τ demonstrated asymmetry with lower values on ipsilateral side to aneurysm, in comparison to contralateral side (P < 0.009),

CONCLUSIONS

Cerebral vasospasm causes shortening of τ. Shorter τ at the side of aneurysm can be observed before formal TCD signs of vasospasm are observed, therefore, potentially reducing time to escalation of treatment.

Magnetic microparticles for endovascular aneurysm treatment: in vitro and in vivo experimental results

OBJECTIVE

Endovascular treatment of intracranial aneurysms employing endosaccular coiling can be associated with aneurysm perforation, coil herniation or incomplete obliteration fueling the interest to investigate novel endovascular techniques. We aimed to test a novel embolization material in experimental aneurysms in vitro and in vivo whereby intra-arterially administered magnetic microparticles (MMPs) are navigated into the lumen of vascular aneurysms with assistance from an external magnetic field.

METHODS

MMPs are core-shell particles suspended in saline that have a shell made of a polymeric material and a core made of magnetite (Fe3O4). They have a diameter of 1.4 μm. During MMP administration via a microcatheter, a magnetic field was applied externally to direct the particles with the use of a solid-state neodymium magnet. Experiments were performed in a perfused silicone vessel and aneurysm model to evaluate application techniques and fluid dynamics and in the elastase aneurysm model in rabbits to evaluate in vivo compatibility, including multiorgan histological examinations and long-term stability of aneurysm embolization.

RESULTS

It was possible to steer and hold the MMPs within the aneurismal cavity where they occluded the lumen progressively. After removal of the external magnetic field, the results remained stable in vivo for the remainder of the observational period (30 minutes); after a 12-week observational period, recanalization of the aneurysm occurred.

CONCLUSION

MMPs can be magnetically directed into aneurysms, allowing short-term obliteration. Although the method has yet to show reliable long-term stability, these experiments provide proof of concept, encouraging further investigation of intravascular magnetic compounds.

Signal-to-noise ratio increase in carotid atheroma MRI: a comparison of 1.5 and 3 T

OBJECTIVES

This study reports quantitative comparisons of signal-to-noise ratio (SNR) at 1.5 and 3 T from images of carotid atheroma obtained using a multicontrast, cardiac-gated, blood-suppressed fast spin echo protocol.

METHODS

18 subjects, with carotid atherosclerosis (>30% stenosis) confirmed on ultrasound, were imaged on both 1.5 and 3 T systems using phased-array coils with matched hardware specifications. T(1) weighted (T(1)W), T(2) weighted (T(2)W) and proton density-weighted (PDW) images were acquired with identical scan times. Multiple slices were prescribed to encompass both the carotid bifurcation and the plaque. Image quality was quantified using the SNR and contrast-to-noise ratio (CNR). A phantom experiment was also performed to validate the SNR method and confirm the size of the improvement in SNR. Comparisons of the SNR values from the vessel wall with muscle and plaque/lumen CNR measurements were performed at a patient level. To account for the multiple comparisons a Bonferroni correction was applied.

RESULTS

One subject was excluded from the protocol owing to image quality and protocol failure. The mean improvement in SNR in plaque was 1.9, 2.1 and 2.1 in T(1)W, T(2)W and PDW images, respectively. All plaque SNR improvements were statistically significant at the p<0.05 level. The phantom experiment reported an improvement in SNR of 2.4 for PDW images.

CONCLUSIONS

Significant gains in SNR can be obtained for carotid atheroma imaging at 3 T compared with 1.5 T. There was also a trend towards increased CNR. However, this was not significant after the application of the Bonferroni correction.

Coiling of a residual internal carotid artery aneurysm via an extracranial-intracranial bypass graft following parent vessel occlusion

We report the case of a ruptured internal carotid artery (ICA) aneurysm that demonstrated significant persistent filling despite management with a common carotid to middle cerebral artery saphenous vein extracranial-intracranial bypass and subsequent permanent ICA balloon occlusion. The residual aneurysm was successfully embolised with detachable coils using a novel endovascular approach via the bypass graft.

Fixed, dilated pupils following traumatic brain injury: historical perspectives, causes and ophthalmological sequelae

Pupillary abnormalities are commonly seen in patients presenting with severe traumatic brain injury (TBI). The objectives of this study were to determine the underlying condition responsible, the natural history of recovery of third nerve palsy and the ultimate clinical outcome in 60 patients admitted to a regional neurosurgical centre with a diagnosis of TBI and unilateral or bilateral fixed, dilated pupils (FDP). In approximately three-quarters of cases, some form of road traffic incident was the mechanism of injury. In patients presenting with a unilateral FDP, the CT-defined condition was most commonly diffuse brain injury (49%) with no obvious lateralising condition. In 34% of cases CT demonstrated a lateralising condition ipsilateral to the side of the FDP and in 9% cases the FDP was contralateral to the side of the CT abnormality. Of those patients who survived an FDP, 72% were left with some form of ophthalmological deficit. Most patients with bilateral FDP did not survive (88%); however, of those who did survive, none was left in a persistent vegetative state or with any ophthalmological sequelae. A FDP is a grave prognostic sign following TBI commonly resulting in long term ophthalmological sequelae; however, a favourable outcome is still attainable.

What comes first? The dynamics of cerebral oxygenation and blood flow in response to changes in arterial pressure and intracranial pressure after head injury

BACKGROUND

Brain tissue partial oxygen pressure (Pbt(O(2))) and near-infrared spectroscopy (NIRS) are novel methods to evaluate cerebral oxygenation. We studied the response patterns of Pbt(O(2)), NIRS, and cerebral blood flow velocity (CBFV) to changes in arterial pressure (AP) and intracranial pressure (ICP).

METHODS

Digital recordings of multimodal brain monitoring from 42 head-injured patients were retrospectively analysed. Response latencies and patterns of Pbt(O(2)), NIRS-derived parameters [tissue oxygenation index (TOI) and total haemoglobin index (THI)], and CBFV reactions to fluctuations of AP and ICP were studied.

RESULTS

One hundred and twenty-one events were identified. In reaction to alterations of AP, ICP reacted first [4.3 s; inter-quartile range (IQR) -4.9 to 22.0 s, followed by NIRS-derived parameters and CBFV (10.9 s; IQR: -5.9 to 39.6 s, 12.1 s; IQR: -3.0 to 49.1 s, 14.7 s; IQR: -8.8 to 52.3 s for THI, CBFV, and TOI, respectively), with Pbt(O(2)) reacting last (39.6 s; IQR: 16.4 to 66.0 s). The differences in reaction time between NIRS parameters and Pbt(O(2)) were significant (P<0.001). Similarly when reactions to ICP changes were analysed, NIRS parameters preceded Pbt(O(2)) (7.1 s; IQR: -8.8 to 195.0 s, 18.1 s; IQR: -20.6 to 80.7 s, 22.9 s; IQR: 11.0 to 53.0 s for THI, TOI, and Pbt(O(2)), respectively). Two main patterns of responses to AP changes were identified. With preserved cerebrovascular reactivity, TOI and Pbt(O(2)) followed the direction of AP. With impaired cerebrovascular reactivity, TOI and Pbt(O(2)) decreased while AP and ICP increased. In 77% of events, the direction of TOI changes was concordant with Pbt(O(2)).

CONCLUSIONS

NIRS and transcranial Doppler signals reacted first to AP and ICP changes. The reaction of Pbt(O(2)) is delayed. The results imply that the analysed modalities monitor different stages of cerebral oxygenation.

Prediction of facial nerve function after surgery for cerebellopontine angle tumors: use of a facial nerve stimulator and monitor

A series of 18 patients undergoing surgery for cerebellopontine angle tumors is reported. Patients were grouped according to size of tumor (0 to 2.5 cm, 11 cases; more than 2.5 cm, 7 cases). In all, the facial nerve was identified and conductance assessed by monitoring the facial electromyographic response to facial nerve stimulation. Postoperative facial nerve function was graded clinically after 3 months according to the House scale. Tumor removal was complete in all cases. In patients with tumors up to 2.5 cm the facial nerve was intact to visual inspection at the end of the procedure in all but one, where partial division was evident. In this group intraoperative facial nerve stimulation indicated electrical integrity in 8 of the 11 cases, all of which regained good facial nerve function postoperatively (House grades I and II). Nerve conduction was lost during the operation in the remaining three patients with small tumors; two subsequently developed a moderately severe (grade IV) dysfunction and the third, a total paralysis (grade VI). In the large (more than 2.5 cm) tumor group the facial nerve was anatomically intact in five of the seven cases, partially divided in one, and completely sectioned in the remaining case. Facial nerve stimulation indicated functional integrity in three patients, two of whom developed moderate (grade III) and the third a severe (grade V) dysfunction. In the other four cases nerve function could not be detected at operation; three of these developed a moderate facial nerve dysfunction (grade III/IV) and the final case a complete paralysis (grade VI). Intraoperative facial nerve monitoring appeared to predict eventual facial function accurately in the small tumor group, but did not predict facial nerve recovery reliably following surgery for larger tumors.

Neurenteric cyst of the anterior cranial fossa: case report and literature review

Intracranial neurenteric cysts are rare congenital lesions that typically occur in the posterior fossa. We report a case of a 70-year-old gentleman presenting with gait disturbance, found to have a neurenteric cyst primarily arising from and expanding the sella turcica. A review of the literature revealed 27 reports of supratentorial neurenteric cysts. Clinical presentation, radiological characteristics, treatment, prognosis and embryological origin are discussed. Intracranial neurenteric cysts should be included in the differential with any well-demarcated cystic lesion without enhancement on magnetic resonance imaging (MRI). Complete surgical excision is the treatment of choice, with good prognosis.

Interaction between brain chemistry and physiology after traumatic brain injury: impact of autoregulation and microdialysis catheter location

Bedside monitoring of cerebral metabolism in traumatic brain injury (TBI) with microdialysis is gaining wider clinical acceptance. The objective of this study was to examine the relationship between the fundamental physiological neuromonitoring modalities intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygen (P(bt)O(2)), and cerebrovascular pressure reactivity index (PRx), and cerebral chemistry assessed with microdialysis, with particular focus on the lactate/pyruvate (LP) ratio as a marker of energy metabolism. Prospectively collected observational neuromonitoring data from 97 patients with TBI, requiring neurointensive care management and invasive cerebral monitoring, were analyzed. A linear mixed model analysis was used to account for individual patient differences. Perilesional tissue chemistry exhibited a significant independent relationship with ICP, P(bt)O(2) and CPP thresholds, with increasing LP ratio in response to decrease in P(bt)O(2) and CPP, and increase in ICP. The relationship between CPP and chemistry depended upon the state of PRx. Within the studied physiological range, tissue chemistry only changed in response to increasing ICP or drop in P(bt)O(2)<1.33 kPa (10 mmHg). In agreement with previous studies, significantly higher levels of cerebral lactate (p<0.001), glycerol (p=0.013), LP ratio (p<0.001) and lactate/glucose (LG) ratio (p=0.003) were found in perilesional tissue, compared to "normal" brain tissue (Mann-Whitney test). These differences remained significant following adjustment for the influences of other important physiological parameters (ICP, CPP, P(bt)O(2), P(bt)CO(2), PRx, and brain temperature; mixed linear model), suggesting that they may reflect inherent tissue properties related to the initial injury. Despite inherent biochemical differences between less-injured brain and "perilesional" cerebral tissue, both tissue types exhibited relationships between established physiological variables and biochemistry. Decreases in perfusion and oxygenation were associated with deteriorating neurochemistry and these effects were more pronounced in perilesional tissue and when cerebrovascular reactivity was impaired.