Correlation between venous stump pressure and brain damage after cortical vein occlusion: an experimental study

The Superficial Anastomosing Veins of the Human Brain Cortex: A Microneurosurgical Anatomical Study

Introduction: In this microneurosurgical and anatomical study, we characterized the superficial anastomosing veins of the human brain cortex in human specimens.

Material and Methods: We used 21 brain preparations fixed in formalin (5%) that showed no pathological changes and came from the autopsy sections. The superficial veins were dissected out of the arachnoid with the aid of a surgical microscope.

Results: We dissected nine female and 12 male brain specimens, with an average age of 71 ± 11 years (range 51–88 years). We classified the superficial veins in five types: (I) the vein of Trolard as the dominat vein; (II) the vein of Labbé as the dominant vein; (III) a dominant sylvian vein group, and the veins of Trolard and Labbé nonexistent or only rudimentary present without contact to the Sylvian vein group; (IV) very weak sylvian veins with the veins of Trolard and Labbé codominant; and V) direct connection of Trolard and Labbé bypassing the Sylvian vein group. The vein of Trolard was dominant (Type I) in 21.4% and the vein of Labbé (Type II) in 16.7%. A dominant sylvian vein group (Type III) was found in 42.9%. Type IV and Type V were found in 14.3 and 4.7% respectively.

Conclusion: No systematic description or numerical distribution of the superior anastomotic vein (V. Trolard) and inferior anastomotic vein (V. Labbé) has been found in the existing literature. This study aimed to fill this gap in current literature and provide data to neurosurgeons for the practical planning of surgical approaches.

Matrix Metalloproteinase-9 Levels are Associated with Brain Lesion and Persistent Venous Occlusion in Patients with Cerebral Venous Thrombosis

BACKGROUND

 Elucidating mechanisms of brain damage in cerebral venous thrombosis (CVT) would be instrumental to develop targeted therapies and improve prognosis prediction. Matrix metalloproteinase-9 (MMP-9), a gelatinase that degrades major components of the basal lamina, has been associated to blood-brain barrier disruption. We aimed to assess, in patients with CVT, the temporal change in serum concentrations of MMP-9 and its association with key imaging and clinical outcomes.

METHODS

 Pathophysiology of Venous Infarction-PRediction of InfarctiOn and RecanalIzaTion in CVT (PRIORITy-CVT) was a multicenter prospective cohort study of patients with newly diagnosed CVT. Serial collection of peripheral blood samples performed on day 1, 3, and 8, and standardized magnetic resonance imaging on day 1, 8, and 90. MMP-9 was quantified using enzyme-linked immunosorbent assay in 59 patients and 22 healthy controls. Primary outcomes were parenchymal brain lesion, early evolution of brain lesion, early recanalization, and functional outcome on day 90.

RESULTS

 CVT patients with parenchymal brain lesion had higher baseline concentrations of MMP-9 compared with controls (adjusted p = 0.001). The area under receiver operating characteristic curve value for MMP-9 for predicting brain lesion was 0.71 (95% confidence interval [CI]: 0.57-0.85, p = 0.009). Patients with venous recanalization showed early decline of circulating MMP-9 and significantly lower levels on day 8 (p = 0.021). Higher MMP-9 on day 8 was associated with persistent venous occlusion (odds ratio: 1.20 [per 20 ng/mL], 95% CI: 1.02-1.43, p = 0.030).

CONCLUSION

 We report a novel relationship among MMP-9, parenchymal brain damage, and early venous recanalization, suggesting that circulating MMP-9 is a dynamic marker of brain tissue damage in patients with CVT.

Early Recanalization in Patients With Cerebral Venous Thrombosis Treated With Anticoagulation

Background and Purpose—

The hypothesis that venous recanalization prevents progression of venous infarction is not established in patients with cerebral venous thrombosis (CVT). Evidence is also scarce on the association between residual symptoms, particularly headache, and the recanalization grade. We aimed to assess, in patients with CVT treated with standard anticoagulation, (1) the rate of early venous recanalization, (2) whether lack of early recanalization was predictor of parenchymal brain lesion progression, and (3) the prevalence and features of persistent headache according to the recanalization grade achieved.

Methods—

PRIORITy-CVT (Pathophysiology of Venous Infarction – Prediction of Infarction and Recanalization in CVT) was a multicenter, prospective, cohort study including patients with newly diagnosed CVT. Standardized magnetic resonance imaging was performed at inclusion (≤24 hours of therapeutic anticoagulation), days 8 and 90. Potential imaging predictors of recanalization were predefined and analyzed at each anatomical segment. Primary outcomes were rate of early recanalization and brain lesion progression at day 8. Secondary outcomes were headache (days 8 and 90) and functional outcome (modified Rankin Scale at days 8 and 90).

Results—

Sixty eight patients with CVT were included, of whom 30 (44%) had parenchymal lesions. At the early follow-up (n=63; 8±2 days), 68% (n=43) of patients had partial recanalization and 6% (n=4) full recanalization. Early recanalization was associated both with early regression ( P =0.03) and lower risk of enlargement of nonhemorrhagic lesions ( P =0.02). Lesions showing diffusion restriction (n=12) were fully reversible in 66% of cases, particularly in patients showing early venous recanalization. Evidence of new or enlarged hemorrhagic lesions, headache at days 8 and 90, and unfavorable functional outcome at days 8 and 90 were not significantly different in patients achieving recanalization.

Conclusions—

Venous recanalization started within the first 8 days of therapeutic anticoagulation in most patients with CVT and was associated with early regression of nonhemorrhagic lesions, including venous infarction. There was an association between persistent venous occlusion at day 8 and enlargement of nonhemorrhagic lesions.

Sturge-weber syndrome: a unified pathophysiologic mechanism

According to a new, unifying view of the pathogenesis of Sturge-Weber syndrome and related syndromes, signs and symptoms all arise from localized primary venous dysplasia, with effects of venous hypertension transmitted to nearby areas via persisting communicating venous passageways and compensatory collateral venous channels. Port-wine stains result from a vascular disorder rather than a neural disorder. Symptoms depend upon the extent and location of the venous dysplasia. This hypothesis is supported by published data and by original observations and Doppler ultrasonographic studies of orbital venous flow in patients with the Sturge-Weber syndrome. This new understanding of underlying pathophysiology also elucidates the mechanism for tissue hypertrophy. Therapies aimed at obliterating port-wine stains to minimize the cosmetic blemish will reduce collateral venous blood-flow passageways. In some instances, this reduction may worsen blood stasis within the brain and potentially exacerbate neurologic symptoms.

Brain perfusion abnormalities in patients with compromised venous outflow

Elevated intracranial intravenous pressure is not routinely measured in clinical practice. Indirect evidence of increased venous pressure is reflected in the size change of the cerebral sinuses and the presence of venous infarctions. The purpose of this study is to evaluate the role of brain perfusion venous time-density curves in the diagnosis of cerebral venous hypertension. A retrospective review of four cases in which increased cerebral intravenous pressure was reflected in abnormal time-density curves on CT brain perfusion studies was completed. The abnormal venous time-density curves correlated with clinically increased intravenous pressure and normalized after treating the underlying pathology. Abnormal venous outflow affects brain perfusion. This could be identified on a CT brain-perfusion study based on characteristic venous time-density curves. These curves may appear quite similar even when the underlying etiologies are different. Normalization of the venous time-density curves may be observed after the underlying pathology was treated.

Microvascular repair of an injured cortical draining vein

BACKGROUND

Cortical venous injury can occur during any intracranial procedure with potentially severe consequences. We describe a simple technique that allowed for successful repair of a large cortical draining vein.

CASE DESCRIPTION

A 43-year-old, right-handed woman presented with 6 months of headaches and progressive difficulty with right-sided hemiparesis. She had significant loss of hand coordination and writing ability. Computed tomography and MR imaging revealed a parasagittal meningioma in the left, posterior frontal region. The patient underwent craniotomy with resection of the lesion.

CONCLUSION

When a cortical vein is injured, collateral drainage pathways may prevent the development of a clinical problem. Because of the unpredictability of these collateral channels, venous reconstruction may be feasible and even straightforward in some cases.

Paroxysmal coughing, subdural and retinal bleeding: a computer modelling approach

Unexplained subdural and retinal haemorrhages in an infant are commonly attributed to 'shaking', the mechanism of which is believed to be traumatic venous rupture. However, the haemorrhagic retinopathy reported as a result of Valsalva manoeuvres and the subdural bleeding that is a rare complication of pertussis together demonstrate that if a sustained rise in intrathoracic pressure is transmitted to cerebral and retinal vessels, it may result in bleeding, similar to that reported in inflicted injury. Such haemorrhages would be expected to occur whenever severe paroxysmal coughing were induced, whatever the cause. This study used a computer modelling approach to investigate feeding accidents as the trigger for bleeding. A dynamic circulatory model of a 3-month-old infant was induced to 'cough', and the response to changes in physiological variables monitored. It showed that coughing causes intracranial pressures to build up exponentially to approach a maximum, proportional to the amount of pressure the musculature of the thorax can produce, as venous return is impeded. They do not have time to become dangerous during individual coughs, as blood quickly returns after the cough is over, reestablishing normal pressures. Paroxysmal coughing, however, does not allow blood to return between coughs, with the result that very high luminal pressures may be generated, sufficient to damage veins. A history of coughing, vomiting or choking is not uncommon in otherwise normal infants with retinal and subdural bleeding. Our findings suggest that paroxysmal coughing could account for such bleeding in some cases.

Cerebral Venous Infarction: The Pathophysiological Concept

Cerebral venous occlusion represents an often underdiagnosed cause for acute or slowly progressive neurological deterioration. The underlying pathophysiological basis is not well understood, but is different from those of arterial occlusion reflecting therefore different anatomical and physiological features of the cerebral venous system. Extensive collateral circulation within the cerebral venous system allows for a significant degree of compensation in the early stages of venous occlusion. Elevated cerebral venous pressure due to cerebral venous occlusion can result in a spectrum of phenomena including a dilated venous and capillary bed, development of interstitial edema, increased cerebrospinal fluid production, decreased cerebrospinal fluid absorption and rupture of venous structures (hematoma). All of these pathophysiological changes may explain the clinical observation that cerebral venous occlusion, if promptly diagnosed and adequately managed, contains reversible alterations and need not always lead to venous infarction. The present review outlines this different pathophysiological behavior of venous compared to arterial occlusion in the cerebral vasculature; special reference is given to the effect of these changes on the therapeutic impact.

Cerebral venous steal: blood flow diversion with increased tissue pressure

PURPOSE

Flow in areas with increased tissue pressure is described by a Starling resistor and is determined by the inflow pressure (P(i)), the external pressure (P(e)), and the outflow or venous pressure (P(v)). Flow is in Zone 1 at P(e) > P(i) > P(v), Zone 2 at P(i) > P(e) > P(v), and Zone 3 at P(i) > P(v) > P(e). A focal tissue pressure increase after stroke or trauma may lead to a transition from Zone 1 or 2 in the center to Zone 3 in the periphery. We hypothesize that the coexistence of different zones may lead to steal-like blood flow diversion in the perifocal area.

CONCEPT

We used a lumped-parameter model of two parallel Starling resistors with a common inflow. The first resistor, with higher P(e), represented the area with increased tissue pressure. The second resistor, with P(e)' = 0, represented the surrounding area. We evaluated the effects of venous pressure on the flow distribution between the two Starling resistors.

RATIONALE

The model demonstrated blood flow diversion toward the second Starling resistor with low external pressure. High inflow resistance facilitates this "steal." Flow diversion is caused by effective outflow pressure differences for the Starling resistors (P(e) for the first and P(v) for the second). The venous pressure increase equilibrates the effective backpressure and decreases flow diversion. When the venous pressure equals the external tissue pressure, blood flow diversion (cerebral venous steal) is abolished. Although increased venous pressure causes global flow reduction, it may restore flow to more than 50% of baseline values in areas of increased tissue pressure.

DISCUSSION

Cerebral venous steal is a potential cause of secondary brain injury in areas of increased tissue pressure. It can be eliminated with increased venous pressure. Increased venous pressure may recruit the collapsed vascular network and correct perifocal perfusion maldistribution. This resembles how positive end expiratory pressure recruits collapsed airways and decreases the ventilation/perfusion mismatch.

Role of venous drainage in cerebral arteriovenous malformation surgery, as related to the development of postoperative hyperperfusion injury

OBJECTIVE

To elucidate the role of venous drainage in cerebral arteriovenous malformation (AVM) surgery, with respect to the development of postoperative hyperperfusion injury.

METHODS

For 52 patients with supratentorial AVMs, cortical capillary oxygenation (SaO(2)) was assessed intraoperatively, before and after resection, in the vicinity of the AVMs, by using a microspectrophotometric method. Assessed areas were defined as being related to feeding arteries or draining veins or as distant areas. Patients were divided into three groups on the basis of postoperative angiographic findings, as follows: Group 1, all former draining veins preserved (8 patients); Group 2, > or =1 former draining vein visible (12 patients); Group 3, no former draining veins visible (32 patients). Patients and SaO(2) values were pooled and compared by using paired and unpaired t tests (P < 0.05). Venous circulation times were calculated from digital subtraction angiography films.

RESULTS

The postresectional relative increases in SaO(2) values were highest in draining vein areas (+40.8%, compared with +25% in feeder areas and +25.5% in distant areas). Five postoperative hyperemic complications occurred (9.6%), none in Group 1 (with all draining veins preserved), two (16.7%) in Group 2, and three (9.4%) in Group 3 (with all draining veins occluded). The lowest preresectional SaO(2) values (31.7 +/- 6.2%) were measured in the drainer areas of the five patients who subsequently developed hyperperfusion injuries. Among those patients, postresectional increases in SaO(2) values were significantly greater in drainer areas (+167.8%) than in feeder areas (+28.3%) or distant areas (+25.8%). Postoperative venous circulation times in former draining veins in Group 2 were significantly greater than those in Group 1 (8.9 +/- 1.5 s versus 6.3 +/- 0.6 s). Circulation times in normal veins in the five patients with hyperperfusion injury increased from 5.6 +/- 1.0 seconds (preoperatively) to 8.4 +/- 1.9 seconds (postoperatively).

CONCLUSION

Postoperative hyperperfusion injury after resection of cerebral AVMs can be explained on the basis of unconstrained arterial inflow into cortical areas, which are rendered hypoxic/ischemic by longstanding preoperative venous hypertension. The risk for postoperative breakthrough complications seems higher in the presence of multiple draining veins, which also participate in the physiological venous drainage system of the ipsilateral hemisphere.

The transsylvian approach is "minimally invasive" but not "atraumatic"

OBJECTIVE

In light of the competition between microneurosurgery and alternative methods such as stereotactic radiosurgery, we tested the hypothesis that changes in the cerebral circulation after microneurosurgery are common among patients without evidence of cerebrovascular or neoplastic disease.

METHODS

Blood flow velocities (BFVs) were recorded with transcranial Doppler ultrasonography, before surgery and every other day after surgery, for a group of 50 patients who underwent transsylvian selective amygdalohippocampectomies for treatment of hippocampal sclerosis. Hexamethylpropylene amine oxime-single-photon emission computed tomographic testing, including acetazolamide testing of cerebrovascular reactivity, was performed during the second postoperative week for 20 of the 50 patients.

RESULTS

BFVs in basal arteries ipsilateral to the surgical approach increased significantly (P < 0.001) from preoperative baseline values of approximately 52 +/- 13 cm/s (mean +/- standard deviation) to values of approximately 86 +/- 27 cm/s on postoperative Day 3 and reached their maximal values of approximately 115 +/- 37 cm/s after a median of 7 days. BFVs in contralateral vessels exhibited a similar but somewhat attenuated pattern. Hexamethylpropylene amine oxime-single-photon emission computed tomography demonstrated ipsilateral regions of hypoperfusion in 100.0% of the cases and contralateral hypoperfusion in 80.0%. Cerebrovascular reactivity was impaired in 83.3% of the cases ipsilaterally and in 33.3% contralaterally.

CONCLUSION

A significant proportion of patients who undergo microneurosurgical procedures develop bilateral alterations of their cerebral circulation. The elevations in mean BFV values represent cerebral vasospasm. Because these changes remain asymptomatic for the majority of patients, the transsylvian approach can be considered "minimally invasive" but not "atraumatic." Alternative surgical routes and alternative treatment modalities should be investigated in a similar manner.

Impairment of autoregulation following cortical venous occlusion in the rat

Recent experiments showed an upward shift of the lower limit of autoregulation (AR) following photochemical occlusion of cortical veins in the rat. The goal of the present study was to prove the hypothesis that occlusion of cortical veins will be associated with impairment of the upper limit of autoregulation as well. In n = 28 Wistar rats unilateral frontoparietal cranial windows were drilled for transdural assessment of regional cerebral blood flow (rCBF) by laser Doppler scanning. The animals were allotted to two groups: (1) Group A (n = 5), control group for determination of the upper limit of autoregulation with stepwise induced arterial hypertension by intravenous administration of the alpha adrenergic drug methoxamine under continuous monitoring of mean arterial blood pressure (MABP); (2) Group B (n = 23), in which two cortical veins were photochemically occluded with rose bengal dye and fiberoptic illumination upon baseline CBF measurement. This was followed by repeated rCBF measurements under AR testing. Loss of AR in control Group A with passive increase of rCBF occurred at MABP of 147.5 +/- 2.9 mmHg. In Group B venous occlusion was followed by an initial phase of reduced rCBF, and then by pressure passive increases, thereby indicating loss of AR. Statistically significant changes of rCBF when compared to baseline MABP occurred at MABPbaseline + 10% (112.7 +/- 6.6 mmHg). We conclude that AR is impaired upon cortical venous occlusion with the propensity for hyperperfusion injury at a lower level of MABP when compared with a control group. In the context with earlier findings this may lead to narrowing of the corridor for MABP management following intra-operative occlusion of large cortical veins.

Microcirculatory alterations in a Mongolian gerbil sinus-vein thrombosis model

BACKGROUND AND PURPOSE

The pathophysiology of sinus vein thrombosis (SVT) is still controversial in patients and experimental animals, the microcirculatory alterations in particular. This study was designed to develop a new sinus vein thrombosis model and to further elucidate pathophysiological events such as the relationship between local and regional cerebral blood flow and haemoglobin oxygen saturation (HbSO2), changes of the microvasculature, leukocyte behaviour and brain tissue damage.

METHODS

In a first experimental series, animals were divided into two groups which resulted from different procedures of inducing SVT. In the SSS middle occlusion group (SMO group), SVT was induced by the ligation of the superior sagittal sinus right in the middle between the bregma and the confluence sinum. In the SSS posterior occlusion group (SPO group) the ligation was performed close to the confluence sinum. Regional cerebral blood flow (rCBF) was assessed at 36 identical locations by laser Doppler flowmetry together with regional haemoglobin oxygen saturation (HbSO2). In a second series of experiments SVT was induced by ligation of the SSS close to the confluence sinum (SVT group) to study effects on the cortical microcirculation. A sham operation was performed in six animals (sham group). In both groups, an intravital microscopic double tracing technique was utilised for evaluating microvessel structures and leukocyte behaviour. The images were recorded on videotape for evaluating alterations of microvessel (venules, arterioles and capillaries) diameters and numbers of leukocyte rollers and stickers by a digital video analyser. Animals were sacrificed for histological evaluation after 5 days.

RESULTS

The posterior sinus ligation caused a significant decrease of rCBF and HbSO2 and brain tissue damage which was not seen in the SMO group. Alteration of rCBF and HbSO2 were positively correlated with infarct size in the SPO group only, where venous infarction was easily reproduced. Therefore, it is suggested that this model is suitable for studying SVT in Mongolian gerbils. Intravital microscopy of the cortical microcirculation revealed no significant changes of vessels diameter in the sham group, whereas a significant dilation of veins and capillaries was seen in the SVT group. Numbers of leukocyte rollers and stickers were positively correlated with infarct size.

CONCLUSION

Microcirculatory alterations and brain tissue damage from SVT in the Mongolian gerbil depend on the SSS occlusion site. The newly established mongolian gerbil sinus-vein thrombosis model has advantages compared to previously reported sinus-vein thrombosis models such as easy handling, easy technique, highly reproducibility, and good observation of microcirculatory event. The model allows for studies of cerebral low-flow conditions such as expected to occur in an ischaemic penumbra zone.

Postoperative cortical venous infarction in tumours firmly adherent to the cortex

It is sometimes difficult to separate extra-axial tumours from the cortical veins in case of tumours attaching tightly to the cortex and the cortical veins. We present two patients having a postoperative cortical venous infarction. A 59 year old female had convexity meningioma above the motor cortex where abnormal cortical anastomotic veins developed. Transient hemiparesis occurred after total removal of the tumour because of venous infarction and cyst formation resulting from sacrifice of these veins which were tightly adherent to the tumour surface. A 15 year old boy with immature teratoma of the pineal region, showing several draining veins around the vascular-rich tumour, presented transient drowsiness, diplopia and partial impairment of bilateral visual acuity postoperatively because of localised cortical brain and venous damage. It is important to make an effort to preserve main cortical veins during operation as much as possible, even if the tumour adheres to the cortical surface.

Intracranial endoscopy

Since 1910, when Lespinasse [73] in Chicago was the first surgeon to use an endoscopic device for the treatment of a neurologic disease, various methods of endoscopy have evolved into accepted diagnostic and therapeutic adjuncts of modern neurosurgery. Nevertheless, until recently technical shortcomings of the available endoscopes have prevented the widespread use of neuroendoscopy. However, now, at the end of the 20th century, endoscopes can be regarded as some of the most important instruments for the development of microneurosurgery into the 3rd millennium. The aim of this review of intracranial endoscopy in neurosurgery, which admittedly might not be completely objective in the authors' personal assessment of various endoscopic techniques, is first to depict the historical evolution of neuroendoscopy, second to describe the technical equipment used in intracranial endoscopic neurosurgery, third to characterize the most frequent endoscopic methods in brain surgery, and fourth to indicate how neuroendoscopy might develop in the near future. It will be shown that this ongoing evolutionary process in neuroendoscopy was only possible with the mutual influence of improved diagnostic techniques, increased microanatomical knowledge, refined neurosurgical instrumentation--especially the introduction of the surgical microscope, and endoscopic diagnostic and therapeutic strategies.