The role of mechanical factors in the pathogenesis of short-term and prolonged spasm of the cerebral arteries

Neurovascular Interventions for Neurotrauma: From Treatment of Injured Vessels to Treatment of the Injured Brain?

Traumatic brain injury is often associated with a direct or secondary neurovascular pathology. In this review, we present recent advancements in endovascular neurosurgery that enable accurate and effective vessel reconstruction with emphasis on its role in early diagnosis, the expanding use of flow diversion in pseudoaneurysms, and traumatic arteriovenous fistulas. In addition, future directions in which catheter-based interventions could potentially affect traumatic brain injury are described: targeting blood brain barrier integrity using the advantages of intra-arterial drug delivery of blood brain barrier stabilizers to prevent secondary brain edema, exploring the impact of endovascular venous access as a means to modulate venous outflow in an attempt to reduce intracranial pressure and augment brain perfusion, applying selective intra-arterial hypothermia as a neuroprotection method mitigating some of the risks conferred by systemic cooling, trans-vessel wall delivery of regenerative therapy agents, and shifting attention using multimodal neuromonitoring to post-traumatic vasospasm to further characterize the role it plays in secondary brain injury. Thus, we believe that the potential of endovascular tools can be expanded because they enable access to the "highways" governing perfusion and flow and call for further research focused on exploring these routes because it may contribute to novel endovascular approaches currently used for treating injured vessels, harnessing them for treatment of the injured brain.

Reversible cerebral vasoconstriction syndrome following intracranial hypotension in a postpartum patient: a case report and literature review

Introduction

Reversible cerebral vasoconstriction syndrome (RCVS) is a potentially life-threatening neurological disorder, rarely linked to intracranial hypotension. The presentation showed a patient with intracranial hypotension after peridural anesthesia who experienced RCVS during the early postpartum period, suggesting a potential involvement of intracranial hypotension in RCVS occurrence.

Case report

A young female of 29 years of age initially developed an orthostatic headache after undergoing a painless delivery with lumbar epidural anesthesia. Intracranial hypotension was considered the underlying cause. Her headache was partially resolved after intravenous fluid therapy and strict bed rest. After 2 days, the patient had a new onset thunderclap headache with generalized seizures, cortical blindness, and elevated blood pressure. An MRI scan revealed high signal intensity within the temporal, parietal, and occipital lobes, left caudate nucleus, and right cerebellum on T2-FLAIR imaging with vasogenic edema. MR angiography indicated multifocal, segmental, diffuse narrowing affecting the cerebral arteries that are large and medium. An RCVS2 score was six, and the patient was diagnosed with RCVS. She was managed conservatively, quickly improving her symptoms. After 10 days, a follow-up MRI indicated a significant reduction in the abnormal signal, and a substantial resolution of the constriction of the cerebral artery constriction was confirmed by MR angiography.

Conclusion

Intracranial hypotension could potentially lead to RCVS in postpartum patients, and it may be triggered by cerebral vasospasm secondary to intracranial hypotension.

Predisposing factors for the deformation of parent artery of anterior circulation saccular aneurysm after stent-assisted embolization: A retrospective cohort study

BACKGROUND

It has been previously reported in several studies that deformation of parent artery (DPA) occurs after stent-assisted coil embolization (SACE) for intracranial aneurysms (IAs).

OBJECTIVE

To investigate the predisposing factors of stent-induced DPA, as well as its effect on the follow-up of aneurysm embolization.

METHODS

Clinical and imaging data were collected from 198 patients (201 aneurysms). Angles of the stent-covered parental artery were measured before treatment and during follow-up. Cases in which the angle had changed more than 5 degrees, were defined as DPA. The related factors of DPA were analyzed. The relation between DPA and follow-up results was also studied.

RESULTS

Univariate analysis revealed that sex (p = 0.014), age (p = 0.017), aneurysm location (p < 0.001), stent type (p < 0.001), aneurysm size (p = 0.019), and pretreatment angle (p = 0.002) correlated with DPA. On the other hand, multivariate analysis revealed that aneurysms located in the anterior communicating artery (ACOA) (OR = 4.559, p = 0.013) and middle cerebral artery (MCA) (OR = 9.474, p < 0.001) were independent predisposing factors for DPA after stent implantation, whereas a braided stent (OR = 0.221, p = 0.030), flow diverter (FD) device (OR = 0.100, p = 0.028) were negative factors to develop DPA. The complete occlusion rate in the DPA group was higher (p = 0.035) than in the non-DPA group.

CONCLUSIONS

Aneurysms located in ACOA and MCA are more prone to DPA after SACE than aneurysms at other locations in the anterior circulation, braided stents and FD devices do not predispose to induce vascular deformation. DPA may be beneficial for the long-term cure of IAs after SACE.

Postpartum posterior reversible encephalopathy syndrome secondary to preeclampsia and cerebrospinal fluid leakage: A case report and literature review

BACKGROUND

Postpartum posterior reversible encephalopathy syndrome (PRES) is not uncommon. Its mechanisms and risk factors are not clear.

CASE SUMMARY

A 28-year-old woman underwent cesarean section but had inadvertent dural puncture during epidural anesthesia. To manage the symptoms of intracranial hypotension, crystalloid fluid was infused. However, the patient developed postpartum preeclampsia and PRES. The patient was treated with diazepam and dehydration therapy. The signs of cerebral lesions on magnetic resonance imaging disappeared on postpartum day 7.

CONCLUSION

Postpartum preeclampsia and PRES can develop concomitantly. Treating postdural puncture headaches with infusion of crystalloid fluid may precipitate the development of PRES.

Development of cerebral vasospasm following traumatic intracranial hemorrhage: incidence, risk factors, and clinical outcomes

OBJECTIVE

Limited evidence exists characterizing the incidence, risk factors, and clinical associations of cerebral vasospasm following traumatic intracranial hemorrhage (tICH) on a large scale. Therefore, the authors sought to use data from a national inpatient registry to investigate these aspects of posttraumatic vasospasm (PTV) to further elucidate potential causes of neurological morbidity and mortality subsequent to the initial insult.

METHODS

Weighted discharge data from the National (Nationwide) Inpatient Sample from 2015 to 2018 were queried to identify patients with tICH who underwent diagnostic angiography in the same admission and, subsequently, those who developed angiographically confirmed cerebral vasospasm. Multivariable logistic regression analysis was performed to identify significant associations between clinical covariates and the development of vasospasm, and a tICH vasospasm predictive model (tICH-VPM) was generated based on the effect sizes of these parameters.

RESULTS

Among 5880 identified patients with tICH, 375 developed PTV corresponding to an incidence of 6.4%. Multivariable adjusted modeling determined that the following clinical covariates were independently associated with the development of PTV, among others: age (adjusted odds ratio [aOR] 0.98, 95% CI 0.97–0.99; p < 0.001), admission Glasgow Coma Scale score < 9 (aOR 1.80, 95% CI 1.12–2.90; p = 0.015), intraventricular hemorrhage (aOR 6.27, 95% CI 3.49–11.26; p < 0.001), tobacco smoking (aOR 1.36, 95% CI 1.02–1.80; p = 0.035), cocaine use (aOR 3.62, 95% CI 1.97–6.63; p < 0.001), fever (aOR 2.09, 95% CI 1.34–3.27; p = 0.001), and hypokalemia (aOR 1.62, 95% CI 1.26–2.08; p < 0.001). The tICH-VPM achieved moderately high discrimination, with an area under the curve of 0.75 (sensitivity = 0.61 and specificity = 0.81). Development of vasospasm was independently associated with a lower likelihood of routine discharge (aOR 0.60, 95% CI 0.45–0.78; p < 0.001) and an extended hospital length of stay (aOR 3.53, 95% CI 2.78–4.48; p < 0.001), but not with mortality.

CONCLUSIONS

This population-based analysis of vasospasm in tICH has identified common clinical risk factors for its development, and has established an independent association between the development of vasospasm and poorer neurological outcomes.

Transvascular in vivo microscopy of the subarachnoid space

BACKGROUND

The micro-architectonics of the subarachnoid space (SAS) remain partially understood and largely ignored, likely the result of the inability to image these structures in vivo. We explored transvascular imaging with high-frequency optical coherence tomography (HF-OCT) to interrogate the SAS.

METHODS

In vivo HF-OCT was performed in 10 dogs in both the posterior and anterior cerebral circulations. The conduit vessels used were the basilar, anterior spinal, and middle and anterior cerebral arteries through which the perivascular SAS was imaged. The HF-OCT imaging probe was introduced via a microcatheter and images were acquired using a contrast injection (3.5 mL/s) for blood clearance. Segmentation and three-dimensional rendering of HF-OCT images were performed to study the different configurations and porosity of the subarachnoid trabeculae (SAT) as a function of location.

RESULTS

Of 13 acquisitions, three were excluded due to suboptimal image quality. Analysis of 15 locations from seven animals was performed showing six distinct configurations of arachnoid structures in the posterior circulation and middle cerebral artery, ranging from minimal presence of SAT to dense networks and membranes. Different locations showed predilection for specific arachnoid morphologies. At the basilar bifurcation, a thick, fenestrated membrane had a unique morphology. SAT average thickness was 100 µm and did not vary significantly based on location. Similarly, the porosity of the SAT averaged 91% and showed low variability.

CONCLUSION

We have demonstrated the feasibility to image the structures of the SAS with transvascular HF-OCT. Future studies are planned to further map the SAT to increase our understanding of their function and possible impact on neurovascular pathologies.

The "Valva Cerebri": Morphometry, Topographic Anatomy and Histology of the Rhomboid Membrane at the Craniocervical Junction

The arachnoid membranes' anatomy is a controversial topic in the literature, and the rhomboid membrane at the craniovertebral junction is an element of this system that has been described poorly. Hence, the objective of our study was to examine this membrane's anatomy and histology. A total of 45 fresh formalin-fixed human cadaveric heads were examined, and anatomic dissections and histologic examinations using standard staining methods were performed. The membrane was found to be a constant structure. It has a rhomboid shape and is located on the medulla oblongata and upper cervical spine's ventral surface within the subarachnoid space. Its average craniocaudal length is 49 mm and the short axis is 26 mm. The cranial apex is attached to the vertebral arteries' junction, and the caudal apex reaches the level of C4. The lateral apices are attached to the dura mater at the level of the denticulate ligament's second insertion. The C1 spinal nerves perforate the membrane, while the C2 roots are located dorsal to it. The membrane is attached strongly to the underlying pia mater. Histologically, it has a typical arachnoid structure, in which its adhesions to the vertebral arteries as well as to the pia mater could be verified histologically. This is the first detailed examination of the rhomboid membrane. Our results suggest that the membrane serves a valve-like function between the spinal and cranial subarachnoid spaces. Based on our findings, further hydrodynamic studies should clarify the membrane's physiological role. Clin. Anat. 32:56-65, 2019. © 2019 Wiley Periodicals, Inc.

The Effect of the Relationship of APOE Polymorphisms and Cerebral Vasospasm on Functional Outcomes in Children With Traumatic Brain Injury

BACKGROUND

Pediatric traumatic brain injury (TBI) is a leading cause of death and disability. Polymorphisms in the apolipoprotein E ( APOE) gene have been linked to cerebral vasospasm (CV) and poor outcomes in adults with TBI, yet these associations remain poorly defined in children.

OBJECTIVE

We examined the effect of the relationship between APOE polymorphisms and CV on functional outcomes in children with a TBI.

METHOD

This prospective, descriptive study examined 60 children (aged 10 days to 15 years) with a TBI. Data included demographic information, genetic sampling for the APOE gene and single-nucleotide polymorphisms (SNPs; rs405509, rs429358, rs7412), and daily transcranial Doppler ultrasounds to evaluate for CV. We examined Glasgow Outcome Scale-Extended Pediatrics (GOS-E Peds) scores at the time of discharge and 4-6 weeks after discharge.

RESULTS

More than half (56.7%) of the 60 children ( M_age = 5.9 years) were male. Twenty-six participants (43.3%) experienced an occurrence of CV. There were significant differences in injury mechanism (unadjusted p = .048) and age (unadjusted p = .02) between those with and without CV. Also, the noncoding promoter SNP rs405509 T/T, when considered with injury severity, appeared to modify the relationship of APOE genotype to CV. The relationship between APOE and CV had no significant effect on GOS-E Peds scores.

CONCLUSION

Injury severity and the APOE noncoding promoter SNP rs405509 may modify the relationship between APOE and CV in children with TBI. More studies are needed to understand the role of APOE polymorphisms in outcomes in children with TBI.

Traumatic brain injury and intracranial hemorrhage–induced cerebral vasospasm: a systematic review

OBJECTIVE

Little is known regarding the natural history of posttraumatic vasospasm. The authors review the pathophysiology of posttraumatic vasospasm (PTV), its associated risk factors, the efficacy of the technologies used to detect PTV, and the management/treatment options available today.

METHODS

The authors performed a systematic review in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using the following databases: PubMed, Google Scholar, and CENTRAL (the Cochrane Central Register of Controlled Trials). Outcome variables extracted from each study included epidemiology, pathophysiology, time course, predictors of PTV and delayed cerebral ischemia (DCI), optimal means of surveillance and evaluation of PTV, application of multimodality monitoring, modern management and treatment options, and patient outcomes after PTV. Study types were limited to retrospective chart reviews, database reviews, and prospective studies.

RESULTS

A total of 40 articles were included in the systematic review. In many cases of mild or moderate traumatic brain injury (TBI), imaging or ultrasonographic studies are not performed. The lack of widespread assessment makes finding the true overall incidence of PTV a difficult endeavor. The clinical consequences of PTV are important, given the morbidity that can result from it. DCI manifests as new-onset neurological deterioration that occurs beyond the timeframe of initial brain injury. While there are many techniques that attempt to diagnose cerebral vasospasm, digital subtraction angiography is the gold standard. Some predictors of PTV include SAH, intraventricular hemorrhage, low admission Glasgow Coma Scale (GCS) score (< 9), and young age (< 30 years).

CONCLUSIONS

Given these results, clinicians should suspect PTV in young patients presenting with intracranial hemorrhage (ICH), especially SAH and/or intraventricular hemorrhage, who present with a GCS score less than 9. Monitoring and regulation of CNS metabolism following TBI/ICH-induced vasospasm may play an important adjunct role to the primary prevention of vasospasm.

Cerebrovascular dysfunction following subfailure axial stretch

Cerebral blood vessels are vital to maintaining the health of the brain. Traumatic brain injury (TBI) commonly results in autoregulatory dysfunction and associated failure of cerebral vessels to maintain homeostasis in the brain. While post-injury changes to brain biochemistry are known to contribute to this dysfunction, tissue deformation may also directly alter vascular smooth muscle cell (SMC) function. As a first step toward understanding stretch-induced dysfunction, this study investigates the effect of overstretch on the contractile behavior of SMCs in middle cerebral arteries (MCAs). We hypothesized that vessel function is altered above a threshold of stretch and strain rate. Twenty-four MCAs from Sprague Dawley rats were tested. Following development of basal SMC tone, vessels were subjected to increasing levels of isosmotic extracellular potassium (K⁺). Samples were then subjected to an axial overstretch of either 1.2*λ_IV or 1.3*λ_IV at strain rates of 0.2 or 20s^-1. Following overstretch, SMC contractile behavior was measured again, both immediately and 60min after overstretch. Control vessels were subjected to the same protocol but without overstretch. SMC contractile behavior was characterized using both percent contraction (%C) relative to the fully dilated inner diameter and the K⁺ dose required to evoke the half maximal contractile response (EC50). Control vessels exhibited increased sensitivity to K⁺ in successive characterization tests, so all effects were quantified relative to the time-matched control response. Samples exhibited the typical biphasic response to extracellular K⁺, dilating and contracting in response to small and large K⁺ concentrations, respectively. As hypothesized, axial overstretch altered SMC contractile behavior, as seen in a decrease in %C for sub-maximal contractile K⁺ doses (p<0.05) and an increase in EC50 (p<0.01), but only for the test group stretched rapidly to 1.3*λ_IV. While the change in %C was only significantly different immediately after overstretch, the change to EC50 persisted for 60min. These results indicate that deformation can alter SMC contractile behavior and thus potentially play a role in cerebrovascular autoregulatory dysfunction independent of the pathological chemical environment in the brain post-TBI.

Modification of cerebral vascular anatomy induced by Leo stent placement depending on the site of stenting: A series of 102 cases

BACKGROUND AND PURPOSE

Recent studies demonstrated the capacity of stents to modify cerebral vascular anatomy. This study evaluates arterial anatomy deformation after Leo stent placement according to the stenting site and the impact on the immediate postoperative and six-month degree of aneurysmal occlusion.

MATERIALS AND METHODS

A total of 102 stents were placed against the neck of aneurysms situated in the anterior cerebral circulation. Aneurysms were classified into two groups: The first was called the distal group (n = 62) and comprised aneurysms situated in the middle cerebral and anterior communicating arteries and the second was called the proximal group (n = 40) and comprised aneurysms in other sites. The stented arterial segment was classified as deformed or non-deformed by blinded review and superimposition of anonymised films before and after stenting. The degree of occlusion was determined immediately postoperatively and at six months.

RESULTS

Significantly, anatomical deformity was observed in the distal group compared to the proximal group (85% vs 28%). No significant difference was observed between the two groups in terms of postoperative degree of occlusion. At six months, a significant difference was observed between the two groups: three recurrences in the distal group vs 10 recurrences in the proximal group. Two (3%) recurrences were observed in the deformed group vs 11 (31%) recurrences in the non-deformed group.

CONCLUSIONS

Arterial deformity induced by stenting is even more marked for distal aneurysms. The recurrence rate is smaller when the stent placement results in an arterial anatomical change. The percentage of recurrence is lower when anatomy was amended by stent implantation.

[Surgical anatomy of spinal cord tumors]

In this article, we respectively describe the morphology of the spinal cord, spinal meningeal layers, main fiber tracts, and both arterial and venous distribution in order to explain signs of spinal cord compression. We will then describe a surgical technique for spinal cord tumor removal.

The epidemiology of vasospasm in children with moderate-to-severe traumatic brain injury

OBJECTIVE

To gain a description of the prevalence and time course of vasospasm in children suffering moderate-to-severe traumatic brain injury.

DESIGN

A prospective, observational study was performed. Children with a diagnosis of traumatic brain injury, a Glasgow Coma Score less than or equal to 12, and abnormal head imaging were enrolled. Transcranial Doppler ultrasound was performed to identify and follow vasospasm. Diagnostic criteria included flow velocity elevation more than or equal to 2 sd above age and gender normal values for the middle cerebral and basilar arteries. Additional criteria required for vasospasm diagnosis in the middle cerebral artery was a ratio of flow in the middle cerebral artery to extracranial internal carotid artery more than or equal to 3.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sixty-nine children were included. The prevalence of middle cerebral artery vasospasm in children with moderate traumatic brain injury (Glasgow Coma Score, 9-12) was 8.5% and was 33.5% in those with severe traumatic brain injury (Glasgow Coma Score, ≤ 8). The prevalence of basilar artery vasospasm in children with moderate traumatic brain injury was 3% and with severe traumatic brain injury was 21%. Mean time to onset of vasospasm was 4 days (± 2 d) in the middle cerebral arteries and 5 days (± 2.5 d) in the basilar artery. Mean duration of vasospasm in the middle cerebral artery was 2 days (± 2 d) and 1.5 days (± 1 d) in the basilar artery. Children in whom vasospasm developed were more likely to have been involved in motor vehicle accidents, had higher Injury Severity Scores, had fever at admission, and had lower Glasgow Coma Score scores. Good neurologic outcome (Glasgow Outcome Score Extended Pediatric version of ≥ 4) at 1 month from injury was seen in 76% of those with moderate traumatic brain injury without vasospasm and in 40% of those with vasospasm. In those with severe traumatic brain injury, good neurologic outcome was seen in 29% of those children without vasospasm and in 15% of those with vasospasm.

CONCLUSIONS

Vasospasm occurs in a sizeable number of children with moderate and severe traumatic brain injury. Children in whom vasospasm developed were more likely to have been involved in a motor vehicle accident, had higher Injury Severity Scores, had fever at admission, and had lower Glasgow Coma scores than in those whom vasospasm did not develop. Based on these findings, we recommend aggressive screening for posttraumatic vasospasm in these patients. Future studies should establish the relationship between vasospasm and long-term functional outcomes and should also evaluate potential preventative or therapeutic options for vasospasm in these children.

Posterior reversible encephalopathy syndrome after depletive lumbar puncture: a case report

Introduction

Posterior reversible encephalopathy syndrome is a rare entity. Its pathophysiology is still poorly understood.

Case presentation

We report the case of a 69-year-old White European woman who presented complete and proportional right hemiplegia, confusion, deviation of her head and eyes to the right, cortical blindness, and generalized tonic-clonic seizure 12 hours following a depletive lumbar puncture. Emergency cerebral magnetic resonance imaging showed bioccipital and left-side basal ganglia hyperintensities in the fluid attenuated inversion recovery and the diffusion-weighted images suggesting a radiological diagnosis of posterior reversible encephalopathy syndrome.

Conclusions

The diagnosis is established on clinical and radiological signs. This is the first report of this kind in the literature. We present a case of posterior reversible encephalopathy syndrome after depletive lumbar puncture and we discuss the pathophysiology.

Post-traumatic cerebral infarction following low-energy penetrating craniocerebral injury caused by a nail

Post-traumatic cerebral infarction (PTCI) is a secondary insult which causes global cerebral hypoxia or hypoperfusion after traumatic brain injury, and carries a remarkable high mortality rate. PTCI is usually caused by blunt brain injury with gross hematoma and/or brain herniation. Herein, we present the case of a 91-year-old male who had sustained PTCI following a low-energy penetrating craniocerebral injury due to a nail without evidence of hematoma. The patient survived after a decompressive craniectomy, but permanent neurological damage occurred. This is the first case of profound PTCI following a low-energy penetrating craniocerebral nail injury and reminds clinicians of possibility this rare dreadful complication for care of head-injured patients.

Comprehensive assessment of isolated traumatic subarachnoid hemorrhage

Recent studies have shown that isolated traumatic subarachnoid hemorrhage (tSAH) in the setting of a high Glasgow Coma Scale (GCS) score (13-15) is a relatively less severe finding not likely to require operative neurosurgical intervention. This study sought to provide a more comprehensive assessment of isolated tSAH among patients with any GCS score, and to expand the analysis to examine the potential need for aggressive medical, endovascular, or open surgical interventions in these patients. By undertaking a retrospective review of all patients admitted to our trauma center from 2003-2012, we identified 661 patients with isolated tSAH. Only four patients (0.61%) underwent any sort of aggressive neurosurgical, medical, or endovascular intervention, regardless of GCS score. Most tSAH patients without additional systemic injury were discharged home (68%), including 53% of patients with a GCS score of 3-8. However, older patients were more likely to be discharged to a rehabilitation facility (p<0.01). There were six (1.7%) in-hospital deaths, and five patients of these patients were older than 80 years old. We conclude that isolated tSAH, regardless of admission GCS score, is a less severe intracranial injury that is highly unlikely to require aggressive operative, medical, or endovascular intervention, and is unlikely to be associated with major neurologic morbidity or mortality, except perhaps in elderly patients. Based upon our findings, we argue that impaired consciousness in the setting of isolated tSAH should strongly compel a consideration of non-traumatic factors in the etiology of the altered neurological status.

Cerebral vasospasm after aneurysmal subarachnoid hemorrhage and traumatic brain injury

OPINION STATEMENT

Cerebral vasospasm (cVSP) consists of the vasoconstriction of large and small intracranial vessels which can lead to cerebral hypoperfusion, and in extreme cases, delayed ischemic deficits with stroke. While most commonly observed after aneurysmal subarachnoid hemorrhage (aSAH), cVSP can also occur after traumatic brain injury (TBI) as we have described in detail in this review. For the past decades, the research attention has focused on cVSP because of its association with delayed cerebral ischemia, which is the largest contributor of morbidity and mortality after aSAH. New discoveries in the cVSP pathophysiology involving multifactorial complex cascades and pathways pose new targets for therapeutic interventions in the prevention and treatment of cVSP. The goal of this review is to demonstrate the commonalities and differences in epidemiology and pathophysiology of both aSAH and TBI-associated cVSP, and highlight the more recently discovered pathways of cVSP. Finally, the latest cVSP surveillance methods and treatment options are illustrated.

Gender influences the initial impact of subarachnoid hemorrhage: an experimental investigation

Aneurysmal subarachnoid hemorrhage (SAH) carries high early patient mortality. More women than men suffer from SAH and the average age of female SAH survivors is greater than that of male survivors; however, the overall mortality and neurological outcomes are not better in males despite their younger age. This pattern suggests the possibility of gender differences in the severity of initial impact and/or in subsequent pathophysiology. We explored gender differences in survival and pathophysiology following subarachnoid hemorrhage induced in age-matched male and female rats by endovascular puncture. Intracranial pressure (ICP), cerebral blood flow (CBF), blood pressure (BP) and cerebral perfusion pressure (CPP) were recorded at and after induction of SAH. Animals were sacrificed 3 hours after lesion and studied for subarachnoid hematoma size, vascular pathology (collagen and endothelium immunostaining), inflammation (platelet and neutrophil immunostaining), and cell death (TUNEL assay). In a second cohort, 24-hour survival was determined. Subarachnoid hematoma, post-hemorrhage ICP peak, BP elevation, reduction in CPP, intraluminal platelet aggregation and neutrophil accumulation, loss of vascular collagen, and neuronal and non-neuronal cell death were greater in male than in female rats. Hematoma size did not correlate with the number of apoptotic cells, platelet aggregates or neutrophil. The ICP peak correlated with hematoma size and with number of apoptotic cells but not with platelet aggregates and neutrophil number. This suggests that the intensity of ICP rise at SAH influences the severity of apoptosis but not of inflammation. Mortality was markedly greater in males than females. Our data demonstrate that in rats gender influences the initial impact of SAH causing greater bleed and early injury in males as compared to females.

Traumatic subarachnoid hemorrhage: our current understanding and its evolution over the past half century

Traumatic brain injury (TBI) is a common cause of morbidity and mortality in the US, especially among the young. Primary injury in TBI is preventable, whereas secondary injury is treatable. As a result, considerable research efforts have been focused on elucidating the pathophysiology of secondary injury and determining various prognosticators in the hopes of improving final outcome by minimizing secondary injury. One such variable, traumatic subarachnoid hemorrhage (tSAH), has been the focus of many discussions over the past half century as numerous clinical studies have shown tSAH to be associated with adverse outcome. Whether the relationship of tSAH with poorer outcome in TBI is merely an epiphenomenon or a result of direct cause and effect is unclear. Some investigators believe that tSAH is merely a marker of severer TBI, while others argue that it directly causes deleterious effects such as vasospasm and ischemia. At the present time, no proven treatment regimen aimed specifically at decreasing the detrimental effects of tSAH exists, although calcium channel blockers traditionally thought to target vasospasm have shown some promises. Given that tSAH may primarily be an early indicator of associated and evolving brain injury, vigilant diagnostic surveillance including serial head CT and prevention of secondary brain damage owing to hypotension, hypoxia and intracranial hypertension may be more cost-effective than attempting to treat potential adverse sequelae associated with tSAH.

Cerebral vasospasm in traumatic brain injury

Vasospasm following traumatic brain injury (TBI) may dramatically affect the neurological and functional recovery of a vulnerable patient population. While the reported incidence of traumatic vasospasm ranges from 19%–68%, the true incidence remains unknown due to variability in protocols for its detection. Only 3.9%–16.6% of patients exhibit clinical deficits. Compared to vasospasm resulting from aneurysmal SAH (aSAH), the onset occurs earlier and the duration is shorter. Overall, the clinical course tends to be milder, although extreme cases may occur. Traumatic vasospasm can occur in the absence of subarachnoid hemorrhage. Surveillance transcranial Doppler ultrasonography (TCD) has been utilized to monitor for radiographic vasospasm following TBI. However, effective treatment modalities remain limited. Hypertension and hypervolemia, the mainstays of treatment of vasospasm associated with aSAH, must be used judiciously in TBI patients, and calcium-channel blockers have offered mixed clinical results. Currently, the paucity of large prospective cohort studies and level-one data limits the ability to form evidence-based recommendations regarding the diagnosis and management of vasospasm associated with TBI.

The importance of early brain injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency that accounts for 5% of all stroke cases. Individuals affected are typically in the prime of their lives (mean age 50 years). Approximately 12% of patients die before receiving medical attention, 33% within 48 h and 50% within 30 days of aSAH. Of the survivors 50% suffer from permanent disability with an estimated lifetime cost more than double that of an ischemic stroke. Traditionally, spasm that develops in large cerebral arteries 3-7 days after aneurysm rupture is considered the most important determinant of brain injury and outcome after aSAH. However, recent studies show that prevention of delayed vasospasm does not improve outcome in aSAH patients. This finding has finally brought in focus the influence of early brain injury on outcome of aSAH. A substantial amount of evidence indicates that brain injury begins at the aneurysm rupture, evolves with time and plays an important role in patients' outcome. In this manuscript we review early brain injury after aSAH. Due to the early nature, most of the information on this injury comes from animals and few only from autopsy of patients who died within days after aSAH. Consequently, we began with a review of animal models of early brain injury, next we review the mechanisms of brain injury according to the sequence of their temporal appearance and finally we discuss the failure of clinical translation of therapies successful in animal models of aSAH.

Risk factors for posttraumatic vasospasm

OBJECT

Posttraumatic vasospasm (PTV) is an underrecognized cause of ischemic damage after severe traumatic brain injury (TBI) that independently predicts poor outcome. There are, however, no guidelines for PTV screening and management, partly due to limited understanding of its pathogenesis and risk factors.

METHODS

A database review of 46 consecutive cases of severe TBI in pediatric and adult patients was conducted to identify risk factors for the development of PTV. Univariate analysis was performed to identify potential risk factors for PTV, which were subsequently analyzed using a multivariate logistic regression model to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Fever on admission was an independent risk factor for development of PTV (OR 22.2, 95% CI 1.9-256.8), and patients with hypothermia on admission did not develop clinically significant vasospasm during their hospital stay. The presence of small parenchymal contusions was also an independent risk factor for PTV (OR 7.8, 95% CI 0.9-69.5), whereas the presence of subarachnoid hemorrhage or other patterns of intracranial injury were not. Other variables, such as age, sex, ethnicity, degree of TBI severity, or admission laboratory values, were not independent predictors for the development of clinically significant PTV.

CONCLUSIONS

Independent risk factors for PTV include parenchymal contusions and fever. These results suggest that diffuse mechanical injury and activation of inflammatory pathways may be underlying mechanisms for the development of PTV, and that a subset of patients with these risk factors may be an appropriate population for aggressive screening. Further studies are needed to determine if treatments targeting fever and inflammation may be effective in reducing the incidence of vasospasm following severe TBI.

Metamorphosis of subarachnoid hemorrhage research: from delayed vasospasm to early brain injury

Delayed vasospasm that develops 3–7 days after aneurysmal subarachnoid hemorrhage (SAH) has traditionally been considered the most important determinant of delayed ischemic injury and poor outcome. Consequently, most therapies against delayed ischemic injury are directed towards reducing the incidence of vasospasm. The clinical trials based on this strategy, however, have so far claimed limited success; the incidence of vasospasm is reduced without reduction in delayed ischemic injury or improvement in the long-term outcome. This fact has shifted research interest to the early brain injury (first 72 h) evoked by SAH. In recent years, several pathological mechanisms that activate within minutes after the initial bleed and lead to early brain injury are identified. In addition, it is found that many of these mechanisms evolve with time and participate in the pathogenesis of delayed ischemic injury and poor outcome. Therefore, a therapy or therapies focused on these early mechanisms may not only prevent the early brain injury but may also help reduce the intensity of later developing neurological complications. This manuscript reviews the pathological mechanisms of early brain injury after SAH and summarizes the status of current therapies.

Posttraumatic vasospasm detected by continuous brain tissue oxygen monitoring: treatment with intraarterial verapamil and balloon angioplasty

INTRODUCTION

Posttraumatic vasospasm (PTV) is a relatively common event following traumatic brain injury (TBI) that has been strongly correlated with worse neurological outcome in many studies. However, vasospasm continues to be an under-recognized source of secondary injury following TBI, and currently published guidelines do not address screening or management strategies for PTV. Brain tissue oxygen (P(bt)O(2)) monitoring probes allow for continuous screening for cerebral hypoxia following TBI, but their use as a monitor for PTV has not been previously described.

METHODS

Case report and literature review.

RESULTS

We present a case of PTV identified by persistent low P(bt)O(2) despite aggressive medical therapy. Computed tomography and digital subtraction angiography confirmed severe cerebral arterial vasospasm involving both anterior and posterior circulations. The patient was successfully treated with serial intraarterial therapy including balloon angioplasty and verapamil infusion.

CONCLUSION

Posttraumatic vasospasm should be included in the differential diagnosis of cerebral hypoxia (e.g., low P(bt)O(2)) following TBI. Management strategies for PTV may include early, aggressive intraarterial therapies including drug infusion and balloon angioplasty.

Posterior Reversible Encephalopathy Syndrome with Vasospasm in a Postpartum Woman After Postdural Puncture Headache Following Spinal Anesthesia

We describe a postpartum woman who, after an uneventful pregnancy, developed posterior reversible encephalopathy syndrome after spinal anesthesia, complicated by postdural puncture headache.

Posttraumatic vasospasm: the epidemiology, severity, and time course of an underestimated phenomenon: a prospective study performed in 299 patients

OBJECT

The purpose of this prospective study was to evaluate the cumulative incidence, duration, and time course of cerebral vasospasm after traumatic brain injury (TBI) in a cohort of 299 patients.

METHODS

Transcranial Doppler (TCD) ultrasonography studies of blood flow velocity in the middle cerebral and basilar arteries (VMCA and VBA, respectively) were performed at regular intervals during the first 2 weeks posttrauma in association with 133Xe cerebral blood flow (CBF) measurements. According to current definitions of vasospasm, five different criteria were used to classify the patients: A (VMCA > 120 cm/second); B (VMCA > 120 cm/second and a Lindegaard ratio [LR] > 3); C (spasm index [SI] in the anterior circulation > 3.4); D (VBA > 90 cm/second); and E (SI in the posterior circulation > 2.5). Criteria C and E were considered to represent hemodynamically significant vasospasm. Mixed-effects spline models were used to analyze the data of multiple measurements with an inconsistent sampling rate. Overall 45.2% of the patients demonstrated at least one criterion for vasospasm. The patients in whom vasospasm developed were significantly younger and had lower Glasgow Coma Scale scores on admission. The normalized cumulative incidences were 36.9 and 36.2% for patients with Criteria A and B, respectively. Hemodynamically significant vasospasm in the anterior circulation (Criterion C) was found in 44.6% of the patients, whereas vasospasm in the BA-Criterion D or E-was found in only 19 and 22.5% of the patients, respectively. The most common day of onset for Criteria A, B, D, and E was postinjury Day 2. The highest risk of developing hemodynamically significant vasospasm in the anterior circulation was found on Day 3. The daily prevalence of vasospasm in patients in the intensive care unit was 30% from postinjury Day 2 to Day 13. Vasospasm resolved after a duration of 5 days in 50% of the patients with Criterion A or B and after a period of 3.5 days in 50% of those patients with Criterion D or E. Hemodynamically significant vasospasm in the anterior circulation resolved after 2.5 days in 50% of the patients. The time course of that vasospasm was primarily determined by a decrease in CBF.

CONCLUSIONS

The incidence of vasospasm after TBI is similar to that following aneurysmal subarachnoid hemorrhage. Because vasospasm is a significant event in a high proportion of patients after severe head injury, close TCD and CBF monitoring is recommended for the treatment of such patients.

Risk factors for the development of post-traumatic cerebral vasospasm

BACKGROUND

Post-traumatic vasospasm is a well-recognized sequela of head injury. The risk factors associated with post-traumatic vasospasm have not been well defined. We studied 119 consecutive patients with head injury to determine the risk factors for post-traumatic vasospasm.

METHODS

Twenty-nine (27.1%) patients were excluded from the study because of poor insonation (n = 12) or a hospital stay of less than 72 hours (n = 17). Seventy (77.8%) of 90 patients suffered severe head injury. Sixteen (17.8%) patients sustained moderate head injury and four (4.4%) patients sustained mild head injury. All patients were monitored with transcranial Doppler (TCD) ultrasonography daily.

RESULTS

Post-traumatic vasospasm was detected in 32 (35.6%) of 90 patients. Among these patients, 29 (90.6%) had severe head injury, and three (9.4%) had moderate head injury. None of the patients with mild head injury suffered post-traumatic vasospasm. In most cases, the onset of post-traumatic vasospasm began on the fifth day and lasted 1 to 9 days. In 8 (25%) patients, post-traumatic vasospasm began within the first three days of the head injury. Among 32 patients with post-traumatic vasospasm, 10 (31.2%) patients had mild vasospasm, 20 (65.5%) had moderate vasospasm, and 2 (6.3%) had severe post-traumatic vasospasm. Clinical deterioration was documented in two (2.5%) patients.

CONCLUSIONS

Development of post-traumatic vasospasm correlated only with severe subarachnoid hemorrhage on initial computed tomographic scan. There was an increased incidence of post-traumatic vasospasm in patients with epidural hematomas, subdural hematomas, and intracerebral hemorrhages. The Glasgow Coma Scale (GCS) score on admission was inversely related to the development of post-traumatic vasospasm. In most cases, the period of vasospasm was short and clinical deterioration was rare. Probably, two varieties of post-traumatic vasospasm exist, one that lasts a shorter time and does not correlate with the presence of SAH, and a second that correlates with the presence of SAH, lasts longer, and resembles aneurysmal vasospasm.

Posttraumatic cerebral vasospasm: clinical and morphological presentations

Head injury is one of the leading causes of morbidity and mortality in the young population. Many factors complicate head injury and worsen an outcome. One of these factors is posttraumatic cerebral vasospasm. We studied 75 patients admitted to the University of Mississippi Medical Center with head injury. Their ages ranged from 14 to 67 years (mean 30 years, SD 11.63). Eighty percent of the patients were men, and 20% were women. Of these patients, 53 (70.6%) suffered severe blunt trauma, and 4 patients suffered gunshot wounds to the head. Four patients had mild head injury, and 14 had moderate head injury. Posttraumatic vasospasm was detected in 24 (32%) patients. Among these patients, 19 (79.2%) had severe closed head injury, 3 patients had moderate head injury, and 2 suffered gunshot wounds. The severity of the patient's respective condition was correlated with the development of posttraumatic cerebral vasospasm: 50% of the patients with Glasgow Coma Scale (GCS) 3-4 developed PTV, and only 30% with GCS 9-11, and none of the patients with GCS > 12 developed PTV. Overall, posttraumatic vasospasm started earlier and had a shorter course than did aneurysmal vasospasm. Morphologically, posttraumatic vasospasm resembled the features of aneurysmal vasospasm. We found increased corrugation of the internal elastic lamina and increased amounts of connective tissue in the subendothelial layer. These findings show that posttraumatic vasospasm, although clinically more mild, demonstrates the same morphological changes as aneurysmal vasospasm.

Traumatic subarachnoid hemorrhage as a predictable indicator of delayed ischemic symptoms

This report provides findings of an investigation of the influence of traumatic subarachnoid hemorrhage on the development of delayed cerebral ischemia caused by vasospasm. The authors prospectively studied 130 patients with closed-head trauma, who exhibited subarachnoid blood on admission computerized tomography (CT) scans. Ten (7.7%) of these patients developed delayed ischemic symptoms between Days 4 and 16 after the head injury. They consisted of three (3.0%) of 101 patients with small amounts of subarachnoid blood and seven (24.1%) of 29 patients with massive quantities of subarachnoid blood on admission CT scans. In each of the 10 patients, severe vasospasm was demonstrated by angiography performed soon after development of ischemic symptoms. There was a close correlation between the main site of the subarachnoid blood and the location of severe vasospasm. In seven of the patients, follow-up CT scans showed development of focal ischemic areas in the cerebral territories corresponding to the vasospastic arteries. These results demonstrate that traumatic subarachnoid hemorrhage, especially if massive, is a predictable indicator of delayed ischemic symptoms.

Impact of traumatic subarachnoid hemorrhage on outcome in nonpenetrating head injury. Part I: A proposed computerized tomography grading scale

The presence of traumatic subarachnoid hemorrhage (tSAH) on admission computerized tomography (CT) scans obtained from patients suffering from severe, nonpenetrating head injury has been shown to be associated with a worse outcome than the injury alone would warrant. However, no previous study has provided a simple means of relating the amount of tSAH, its location, or other abnormal findings on initial head CT scans to outcome in patients with non-penetrating head injury. In this study, admission head CT scans from 252 patients with tSAH, treated at a single institution, were reviewed to ascertain thickness of the tSAH; its location; evidence of mass lesion(s); shift of midline structures (< or = 5 mm vs. > 5 mm); basal cistern effacement; and cortical sulcal effacement. The CT scans were then organized into Grades 1 to 4 with 1 indicating thin tSAH (< or = 5 mm); 2, thick tSAH (> 5 mm); 3, thin tSAH with mass lesion(s); and 4, thick tSAH with mass lesion(s). A stepwise regression analysis of CT features ranked them in descending order of contribution to Glasgow Outcome Scale (GOS) scores at the time of discharge from acute hospitalization as follows: basal cistern effacement, thickness of tSAH, cortical sulcal effacement, presence of mass lesion(s), and location of tSAH. A shift of midline structures was not found to be a significant variable. Further analysis comparing CT grades and admission postresuscitation Glasgow Coma Scale (GCS) scores was highly significant. Patients with lower CT grades had better admission GCS values and discharge GOS scores than those with higher CT grades. From their experience, the authors conclude that their CT grading scale is simple and reliable and relates significantly to outcome at the time of discharge from acute hospitalization.

Immediate cerebrovascular responses to closed head injury in the rat

Changes in cerebrovascular dynamics were investigated immediately after closed head injury in the rat using a newly developed closed head injury model developed by Marmarou et al. Intracranial pressure (ICP) and mean arterial blood pressure (MABP) were monitored before and after trauma. Regional cerebral blood flow (rCBF), regional cerebral plasma volume (rCPV), and blood-brain barrier (BBB) permeability were measured autoradiographically with iodo[14C]antipyrine [14C]sucrose, and [alpha-14C]aminoisobutyric acid, respectively. rCBF responses to induced hypertension after trauma were measured by laser-Doppler flowmetry to investigate the status of autoregulation. Before injury, baseline ICP values ranged from 6 to 10 mm Hg in all animals. Immediately after trauma, ICP increased synchronously with MABP to > 100 mm Hg and then rapidly returned to baseline values: MABP increased rapidly by 20% after trauma and returned to baseline values within 30 sec. At 30 sec after injury, a significant increase in rCBF was observed in five subcortical regions (p < 0.05), and a significant increase in rCPV was observed in the frontal cortex, parietal cortex, thalamus, and hypothalamus (p < 0.05). At 10 min after injury, BBB permeability (the transfer constant for [alpha 14C]aminoisobutyric acid) was < 0.1 mL/kg/min for all regions except those with a relatively permeable BBB, for example, median eminence, choroidal plexus, pineal body, and pituitary gland. Induced hypertension resulted in a prolonged increase in rCBF after trauma. Thus, in this closed head injury model, which is not associated with marked hypertension or prolonged BBB disruption, widespread increases in rCBF and impaired cerebral autoregulation were apparent immediately after injury.

Pathways of fluid drainage from the brain--morphological aspects and immunological significance in rat and man

There is firm physiological evidence for the lymphatic drainage of interstitial fluid and cerebrospinal fluid from the brains of rats, rabbits and cats. The object of this review, is to describe firstly the morphological aspects of lymphatic drainage pathways from the rat brain and secondly, to explore through scanning and transmission electron microscope techniques, the possibility of similar lymphatic drainage pathways in man. Interstitial and oedema fluid spreads diffusely through the white matter in the rat and appears to drain into the ventricular cerebrospinal fluid. In grey matter, however, tracers pass along perivascular spaces to the surface of the brain and into the cerebrospinal fluid. Paravascular compartments in the subarachnoid space follow the course of major arterial branches to the circle of Willis and thence along the ethmoidal arteries to the cribriform plate of the ethmoid bone. Particulate tracers, such as Indian ink, enter channels in the arachnoid beneath the olfactory bulbs and connect directly with nasal lymphatics through channels which pass through holes in the cribriform plate. Proteins and other solutes may also drain along other cranial nerves. Thus, there is a bulk flow pathway for interstitial and cerebrospinal fluid from the rat brain into cervical lymphatics. In man, it is probable that diffuse interstitial drainage of fluid from the white matter occurs in a similar way to that in the rat. Furthermore, the anatomical pathways exist by which bulk drainage of fluid could occur along perivascular spaces from the grey matter into perivascular spaces of the leptomeningeal arteries and thence into the cerebrospinal fluid (CSF).(ABSTRACT TRUNCATED AT 250 WORDS)

Longitudinal time course of reversible and irreversible components of chronic cerebrovasospasm of the rabbit basilar artery

Multiple injections of autologous blood were made around the basilar artery of rabbits through a silicone catheter placed into the prepontine cistern. The total blood injected was 3 ml/kg in aliquots of 0.5 to 0.8 ml over a 4-hour period. Control angiograms were obtained 7 days before this procedure. Groups of animals were examined by angiography on each of 9 days after the injections of blood. An angiogram was obtained 15 minutes after the first injection of blood, 20 seconds after the intra-arterial injection of a maximum dilating dose of papaverine. All surviving animals showed basilar artery narrowing, which was greatest 24 hours after the hemorrhage, when the vessel diameter was reduced to 54% of the control value. The narrowing then decreased to a reduction of about 30%, which was maintained throughout the rest of the study period. A papaverine-resistant component of narrowing was not seen until the 3rd day. It increased progressively to Day 9 when it represented 63% of the total. This model has a number of features that are reminiscent of human cerebrovasospasm, including the fact that there is an initial phase of narrowing that is completely reversed by an intra-arterially administered vasodilator, and a second phase beginning on Day 3 which exhibits a progressively increasing papaverine-resistant component.

The fine anatomy of the human spinal meninges. A light and scanning electron microscopy study

The fine anatomy of the human spinal meninges was examined in five postmortem spinal cords taken within 12 hours after death from patients aged 15 months to 46 years. Specimens of spinal cord were viewed in transverse section and from the dorsal and ventral aspects by scanning electron microscopy. Transverse sections of spinal cord and meninges were also examined by light microscopy. The arachnoid mater was seen to be closely applied to the inner aspect of the dura. An intermediate fenestrated leptomeningeal layer was observed attached to the inner aspect of the arachnoid mater and was reflected ventrally to form a series of dorsal septa. As it arborized laterally over the surface of the cord to surround nerves and blood vessels, the intermediate layer became highly fenestrated but remained distinct from the pia and arachnoid mater. The pia mater appeared to form a continuous layer which was reflected off the surface of the cord to coat blood vessels within the subarachnoid space in a manner similar to that described in the leptomeninges over the human cerebral cortex. Each dentate ligament consisted of a collagenous core which was continuous with the subpial connective tissue and was attached at intervals to the dura; pia-arachnoid cells coated the surface of the dentate ligaments. The present study suggests that the fine anatomy of the human spinal meninges differs significantly from that described in other mammals.

The cranial arachnoid and pia mater in man: anatomical and ultrastructural observations

The objects of the present study were: (1) to define the relationships of the arachnoid mater to blood vessels in the subarachnoid space; (2) to establish the structure of leptomeningeal trabeculae and their relationships to the pia mater; and (3) to investigate the fine structure of the human pia mater. Intracranial portions of vertebral artery were taken at post mortem, and normal cerebral cortex and overlying leptomeninges were obtained from surgical lobectomies. Tissue from these specimens was examined by scanning and transmission electron microscopy, by light microscopy and by immunocytochemistry for the presence of basement membrane, desmosomal proteins and vimentin. Results of the study showed that as the vertebral artery pierced the posterior atlanto-occipital membrane and entered the subarachnoid space, it acquired a leptomeningeal coat as the arachnoid was reflected on to it. It has been demonstrated previously that as vessels enter the brain, the leptomeningeal coat is reflected on to the surface of the cortex as the pia mater. The arachnoid mater was seen to consist of a subdural mesothelial layer and a compact central layer as previously reported. From the inner layer of the arachnoid, collagen bundles coated by leptomeningeal cells extended as trabeculae across the subarachnoid space to fuse with the pia mater. The pia itself was composed of a delicate but apparently continuous layer of cells joined by desmosomes and gap junctions but no tight junctions were observed. It was possible to detect pia mater cells in the perivascular spaces of the brain by immunocytochemical techniques using light microscopy. The significance of the observed anatomical arrangement for cerebrospinal fluid physiology is discussed.

Is there a role for heparin in the management of complications of subarachnoid hemorrhage?

Proven effective therapy to prevent ischemic deficits and other complications after subarachnoid hemorrhage is lacking despite extensive research efforts. A literature review documented both clinical and experimental evidence suggesting that heparin may be effective in preventing ischemic deficits after subarachnoid hemorrhage by reversing vasospasm, improving blood flow through narrowed vessels, and preventing the development of a proliferative angiopathy. Additional evidence suggests that heparinization of the cerebrospinal fluid following subarachnoid hemorrhage may prevent the development of hydrocephalus. In the only clinical trial using heparin after subarachnoid hemorrhage, the incidence of rebleeding in the heparinized patients was no higher than in the control group. We conclude that the existing preliminary data concerning a role for heparin in the management of the complications of subarachnoid hemorrhage is promising, but further controlled studies are needed prior to clinical application.

Anatomical relationships of the pia mater to cerebral blood vessels in man

Using scanning and transmission electron microscopy and light microscopy, the authors studied the human pia mater and its relationship to the entry of blood vessels into the normal cerebral cortex. The purpose of this investigation was to examine the long-established concept that the subarachnoid space communicates directly with the perivascular spaces of the cerebral cortex. Brains obtained post mortem from subjects with recent subarachnoid hemorrhage (SAH) and purulent leptomeningitis were studied by light microscopy to determine the permeability of the pia mater to red blood cells and inflammatory cells. Scanning electron microscopy showed that the normal pia mater is a flat sheet of cells that is reflected from the surface of the brain to form the outer coating of the meningeal vessels in the subarachnoid space. Transmission electron microscopy confirmed that the cells of the pia mater are joined by junctional complexes and form a continuous sheet that separates the subarachnoid space on one side from the subpial and perivascular spaces on the other. Thus, neither the pia mater nor the subarachnoid space extends into the brain beside blood vessels as they enter the cerebral cortex. The perivascular spaces were, in fact, found to be confluent with the subpial space and not with the subarachnoid space. In cases of recent SAH, red blood cells did not enter the perivascular spaces from the subarachnoid space; neither did India ink injected post mortem into the subarachnoid space pass into the perivascular spaces. The results of these crude tracer studies suggest that the pia mater is an effective barrier to the passage of particulate matter. Histological examination of brains of patients who had died with purulent leptomeningitis showed that inflammatory cells were present in the cortical perivascular spaces and in the contiguous subpial spaces. The presence of a large number of inflammatory cells in the subarachnoid space suggests that inflammatory cells readily penetrate the pia mater that separates the perivascular spaces from the subarachnoid space. The permeability of the pia mater to small molecular weight substances is briefly discussed.

Activity of peripheral sympathetic efferent nerves in experimental subarachnoid haemorrhage. Part II: Observations during the "early vasospasm" period

The efferent activity of the vertebral, cardiac and renal sympathetic nerves was recorded during the so-called "early vasospasm" period, 25-30 minutes after experimentally induced subarachnoid haemorrhage. Experiments were performed on 51 cats with methods described in Part I of our publication. The animals were held either in a sphynx-like position (Pos. I), or in head-down position (Pos. II), when the level of the cisterna magna was 2-3 cm below the level of the spinal cord, facilitating the injected blood to flow in to, and remain at the base of the brain. According to our results during the "early vasospasm" period, we could not observe such changes in the sympathetic efferent activity, which could be specific for this period. With the gradual decrease in the intracranial pressure, the sympathetic overactivity ceased, and in most cases the level of activity was similar to that of the preinjection period. Our results also indicate that because of the remarkable variability of the activity of the renal sympathetic nerve during the intracranial pressure elevation, recording the activity of one sympathetic nerve only may give misleading results concerning the activity of the whole sympathetic system.

Cerebral vasospasm as a complication of aneurysmal subarachnoid hemorrhage: a brief review

Cerebral vasospasm is one of the most dreaded consequences of a ruptured intracranial aneurysm. Although exceptions may be found, the relationship between angiographic narrowing of cerebral arteries and deterioration of clinical status is supported by many authors. The cause of cerebral vasospasm still remains obscure. Several substances such as serotonin, prostaglandins, catecholamines appear to have a vasoconstrictive effect on the cerebral vessels. Recent evidence indicates that erythrocyte lysis within the subarachnoid spaces may play a major role in the genesis of delayed clinically relevant cerebral vasoconstriction following aneurysmal subarachnoid hemorrhage (SAH). The pathophysiology of brain ischemia following aneurysmal rupture, and the correlation between angiographic vasospasm, neurological condition, intracranial pressure (ICP) value, cerebral blood flow and CT findings are briefly discussed. It is concluded that, at present, blood volume expansion and/or induced hypertension, and pharmacological control of increased ICP provide the best basis for clinical management of the cerebral ischemic complications of SAH. Preoperative antifibrinolytic therapy and delayed surgical obliteration of the bleeding aneurysm, i.e. the policy at present most frequently adopted, are currently undergoing critical review in the light of the fact that antifibrinolytic therapy seems to be accompanied by a higher rate of ischemic SAH complications and vasospasm, whilst there are very recent suggestions that the results of early intracranial aneurysm surgery may be better than those of delayed surgery, if account is taken of the patients lost because of recurrent SAH or ischemia during the waiting period.

Cerebral vasospasm after subarachnoid hemorrhage: an update

Symptomatic vasospasm, or delayed cerebral ischemia associated with arteriographic evidence of arterial constriction, is currently the most important cause of morbidity after acute subarachnoid hemorrhage. The development of vasospasm is directly correlated with the presence of thick blood clots in the basal subarachnoid cisterns, which can be detected by an early computed tomographic scan. Symptomatic vasospasm usually develops between 4 and 12 days after subarachnoid hemorrhage. The onset is gradual, occurring over hours or days. There is typically a gradual deterioration of the level of consciousness, accompanied by focal neurological deficits that are determined by the arterial territories involved. Hyponatremia frequently occurs and may exacerbate the symptoms. The patients are usually volume depleted, and therefore many authorities now treat them with replenishment and expansion of their intravascular volume with colloid and blood. Volume expansion, together with elevation of the systemic blood pressure and reduction of the intracranial pressure when elevated, constitute the only currently available effective therapy for symptomatic vasospasm. The cause of vasospasm remains obscure. Mechanisms of smooth muscle cell contraction and relaxation and experimental efforts to elucidate the nature of vasospasm are reviewed.