Carotid compression: investigation of cerebral autoregulative reserve in rats

Easy-to-perform, reversible techniques to analyse cerebral autoregulation are still missing in animal research. The carotid compression technique has been established to investigate dynamic cerebral autoregulation in humans. Adapting the carotid compression technique, we compared data from the new application with that of a classical exsanguination method. Compressing the ipsilateral carotid artery with a non-traumatic clip device for 10s modulated cerebral perfusion pressure. After clip release, the peaking laser-Doppler flow velocity increase over the somatosensory cortex allowed calculation of the transient hyperaemic response ratio (THRR) in relation to baseline. Modulating blood-pressure levels maintenance of cerebral blood-flow velocity was compared with THRR responses. With decreasing blood-pressure levels, the THRR first increased (29+/-16% at 95+/-10 mmHg to 39+/-13% at 75+/-10 mmHg) before it returned to baseline values at 54+/-10 mmHg (27+/-14%). THRR significantly dropped to 11+/-12% at 34+/-11 mmHg when resting cerebral blood-flow velocity levels also started to decline. Based on the close correlation between blood-flow velocity levels and THRR responses, we have concluded that carotid compression is an alternative technique that can be used to assess cerebral autoregulation in rats. The technique allows less invasive and reversible testing of dynamic autoregulation to be performed, and the technique can easily be applied in conjunction with functional tests to potentially allow deeper insights into cerebral vasoregulative mechanisms.

Autoimmune etiology of complex regional pain syndrome (M. Sudeck)

Sera of 12 patients with complex regional pain syndrome (CRPS) were tested for the occurrence of autoantibodies against nervous system structures. Immunohistochemistry revealed autoantibodies against autonomic nervous system structures in 5 of 12 (41.6%) of the patients. Western blot analysis showed neuronal reactivity in 11 of 12 (91.6%) patients. The authors hypothesize that CRPS can result from an autoimmune process against the sympathetic nervous system.

Acetylcholine esterase inhibitor donepezil improves dynamic cerebrovascular regulation in Alzheimer patients

BACKGROUND

Alzheimer's disease (AD) leads to a degeneration of the nucleus basalis of Meynert and thus to decreased cholinergic tonus in the brain. The transcription of endothelial nitric oxide synthase depends on an adequate cholinergic innervation of microvessels and vasoregulative abnormalities have been reported in AD. We investigated activation-flow coupling to study the role of acetylcholine esterase inhibition (AChEI) on vasoregulative function.

METHODS

A functional transcranial Doppler approach was used to measure the visually evoked flow velocity response in the posterior cerebral artery in AD patients who had no vascular risk factors. The diagnosis of AD was made according to the ICD10/DSMIIIR-criteria. After baseline recording the effect of four weeks 5mg donepezil and then four weeks 10 mg was investigated. Doppler data were evaluated with a control system approach to obtain dynamic properties of vasoregulation and were compared with a healthy control group.

RESULTS

AD patients showed an increased damping (0.64 +/- 0.2; p = 0.007 vs. control) in evoked responses and lower resting flow velocity levels (40 +/- 13 cm/s; p = 0.06 vs. control), which were restored in a dose-dependent manner under AChEI (0.4 +/- 0.2; 44 +/- 11 cm/s).

CONCLUSIONS

AD is associated with a functional vasoregulative deficit possibly due to decreased levels of the endothelial nitric oxide synthase. Augmenting levels with AChEI normalized flow regulation possibly leading to a better blood supply to active neurons.

Surface-binding autoantibodies to cerebellar neurons in opsoclonus syndrome

Childhood opsoclonus-myoclonus syndrome can occur with or without associated neuroblastoma. An autoimmune pathogenesis has been discussed for both forms. We show here that the majority of children with opsoclonus-myoclonus syndrome (10/14) have autoantibodies binding to the surface of isolated rat cerebellar granular neurons. In some patients, these antibodies are masked by IgG binding to ubiquitous surface antigens, which could be removed by preincubation with the nonneuronal control cell line HEK 293. A newly introduced competitive binding assay showed that the surface binding is directed against the same autoantigen in different patients. Therefore, we hypothesize that opsoclonus-myoclonus syndrome may be the result of an autoimmune process against a neuronal surface protein.

Dual Antiplatelet Therapy With Clopidogrel and Aspirin in Symptomatic Carotid Stenosis Evaluated Using Doppler Embolic Signal Detection

Background— Evidence for efficacy of dual antiplatelet therapy in stroke is limited. Symptomatic carotid stenosis patients are at high risk of early recurrent stroke. In this group, asymptomatic microembolic signals (MES), detected by transcranial Doppler ultrasound (TCD), are markers of future stroke and transient ischemic attack (TIA) risk. They offer a surrogate marker to evaluate antiplatelet therapy, but no multicenter study has evaluated the feasibility of this approach.

Methods and Results— Clopidogrel and Aspirin for Reduction of Emboli in Symptomatic Carotid Stenosis (CARESS) is a randomized, double-blind study in subjects with recently symptomatic ≥50% carotid stenosis. Patients were screened with TCD, and if MES were detected, they were randomized to clopidogrel and aspirin or aspirin monotherapy. Repeated TCD recordings were made on days 2 and 7. MES were detected in 110 of 230 patients by online analysis at baseline, of whom 107 were randomized. Intention-to-treat analysis revealed a significant reduction in the primary end point: 43.8% of dual-therapy patients were MES positive on day 7, as compared with 72.7% of monotherapy patients (relative risk reduction 39.8%; 95% CI, 13.8 to 58.0; P =0.0046). The secondary end point of MES frequency per hour was reduced (compared with baseline) by 61.4% (95% CI, 31.6 to 78.2; P =0.0013) in the dual-therapy group at day 7 and by 61.6% (95% CI, 34.9 to 77.4; P =0.0005) on day 2. There were 4 recurrent strokes and 7 TIAs in the monotherapy group versus no stroke and 4 TIAs in the dual-therapy group that were treatment emergent and ipsilateral to the qualifying carotid stenosis; 2 additional ipsilateral TIAs occurred before treatment started. MES frequency was greater in the 17 patients with recurrent ipsilateral events compared with the 90 without (mean±SD: 24.4±27.7 versus 8.9±11.5 per hour; P =0.0003).

Conclusions— In patients with recently symptomatic carotid stenosis, combination therapy with clopidogrel and aspirin is more effective than aspirin alone in reducing asymptomatic embolization. Doppler MES detection is a feasible method to evaluate the efficacy of antiplatelet therapy in multicenter studies.

Identification of Embolic Stroke Patterns by Diffusion-Weighted MRI in Clinically Defined Lacunar Stroke Syndromes

BACKGROUND

A number of clinical syndromes describing the presentation of deep brain infarcts are called lacunar syndromes resulting from small vessel occlusion (SVO). To verify the reliability of the clinical diagnosis "lacunar syndrome," the value was investigated with diffusion-weighted MRI (DWI).

METHODS AND RESULTS

A total of 73 patients (mean age 66 years; range 35 to 83 years) with sudden onset of a classical lacunar syndrome were enrolled. On the basis of the DWI findings, patients were divided into 3 groups: group 1, single subcortical lesion (<15-mm lesion; 43 patients; 59%); group 2, large (> or =15 mm) or scattered lesions in 1 vascular territory (16 patients; 22%); and group 3, multiple lesions in multiple vascular territories (14 patients; 19%). A stroke mechanism other than SVO could be identified in 17 (23%) patients. Cardiac work-up revealed a cardiac embolic source in 8 patients (11%). Duplex sonography revealed symptomatic stenosis in 9 patients (12%). Based on the work-up information, 29 patients (40%) were found to have a potential cause of stroke other than SVO. A significant correlation with >1 single lesion on DWI-MRI and a clinical proven embolic source was observed (P=0.002). In 9 patients with MRI suspicious for a pathomechanism other than SVO, no embolic source was found.

CONCLUSIONS

The use of DWI-MRI improves the accuracy of the subtype diagnosis of stroke. Inaccuracy has to be expected in approximately one third if lacunar diagnosis is based on clinical and computed tomography findings. Most of these "false-positive" cases are attributable to large artery or cardiogenic embolic stroke.

Upper cranial nerve palsy resulting from spontaneous carotid dissection

INTRODUCTION

Upper cranial nerve palsy has a variety of causes such as cerebral and nerve ischemia, diabetes, infectious and non-infectious meningitis, subarachnoid hemorrhage and intracranial aneurysm. CASE 1 : A 45-year-old man suffered from holocephalic headaches and a right-sided neck pain for two weeks. He presented to our emergency department because of a sudden ptosis of the right eye. On admission neurological examination revealed a right sided Horner's syndrome and hypesthesia of the right side of the face. Magnetic resonance angiography identified a circumscribed dissection of the right extracranial internal carotid artery originating from the carotid bifurcation. Conventional angiography 2 weeks later showed a nearly recanalized artery. CASE 2 : A 55-year-old previously healthy man without cardiovascular risk factors developed right sided neck pain when loading a seeder with several sacks of crop. A few hours later he noticed a left-sided weakness. On admission a severe left sided hemiparesis and a mild neglect were present. Duplex sonography revealed a right-sided distal internal carotid artery (ICA) occlusion. The next morning the patient complained of double vision; he had a right-sided pupil-sparing oculomotor palsy. The diagnosis of ICA dissection was confirmed by conventional angiography, at that time showing a partially recanalized ICA without involvement of the cavernous region by the dissection.

CONCLUSION

ICA dissection must be included in the differential diagnosis of upper cranial nerve palsy and should be assessed by duplex ultrasound and magnetic resonance imaging. A possible explanation is nerve ischemia due to a transient or permanent interruption of the blood supply by compression of the vasa nervorum originating from the intracranial carotid artery.

Interferon-beta 1b leads to a short-term increase of soluble but long-term stabilisation of cell surface bound adhesion molecules in multiple sclerosis

Adhesion molecules (AMs) are believed to regulate the transmigration of blood leukocytes across the blood-brain barrier (BBB), which is an essential step in the pathogenesis of multiple sclerosis (MS). Previous studies have investigated changes of the soluble forms of AM during interferon-beta1b (IFN-beta1b) treatment in MS patients. In this study, we analysed the influence of IFN-beta1b treatment on the cell surface bound forms of the AMs cICAM-1 and cICAM-3 on blood mononuclear cells (MNC). Sixty-eight patients with relapsing-remitting MS were enrolled in this open study; thirty of them were treated with IFN-beta1b. Blood samples were collected every three months over a period of 18 months. The expression levels of cell surface bound forms of AM on blood MNC were measured by two colour flow cytometry analysis. sVCAM-1, sICAM-1 and sICAM-3 were determined by ELISA. We found a short-term induction effect on the serum concentrations of sICAM-1 and sVCAM-1 after three months of IFN-beta1b treatment. The expression levels of cell surface bound AMs on blood MNC remained stable during treatment. Untreated MS patients, however, showed a continuous decrease in the expression of cell surface bound AM expression over 18 months. Stabilisation of the expression of cell surface bound AMs on blood MNC may indicate the beneficial effects of IFN-beta1b therapy in MS patients.

Reversible MR imaging abnormalities following cerebral venous thrombosis

BACKGROUND AND PURPOSE

Although rare, cerebral venous thrombosis (CVT) is being diagnosed more frequently owing to improved imaging techniques. The venous infarcts caused by CVT in 50% of patients are largely reversible and differ from arterial stroke. Our purpose was to study the time-dependent changes of venous infarcts on MR images and to define the variables that influence lesion volume in humans.

METHODS

MR images and venous angiograms were evaluated in 15 consecutive patients with venous infarcts due to CVT of sinus, cortical, or internal veins. All patients were treated with intravenous dose-adjusted heparin followed by oral anticoagulation for 12 months. Reduction of signal intensity changes on T1- and T2-weighted images was correlated to the degree of recanalization, age, initial absolute lesion size, and hemorrhage.

RESULTS

Within the first 30 days, we found a significant correlation between the volume of the lesion on T1-weighted images and recanalization. However, early recanalization did not influence the final lesion volume after 12 months. Eleven patients showed complete resolution of changes on T1- and T2-weighted images. Age of the patients influenced initial absolute volume of brain damage.

CONCLUSION

In venous stroke, even large parenchymal changes can resolve completely independent from recanalization of the thrombosed veins and sinuses. A plausible hypothesis is that venous infarcts largely consist of a persistent edema and that the lesion volume is influenced by the development of collateral veins. However, further investigations are necessary to understand the underlying abnormal mechanisms.

Is heparin treatment the optimal management for cerebral venous thrombosis? Effect of abciximab, recombinant tissue plasminogen activator, and enoxaparin in experimentally induced superior sagittal sinus thrombosis

BACKGROUND

Based on a newly developed model of reversible superior sagittal sinus (SSS) thrombosis in the rat, we investigated the effect of thrombolytic and anticoagulant treatment on recanalization, brain parenchymal changes, and motor deficits.

METHODS

Thrombosis of the SSS was induced by topical application of ferric chloride. Occlusion was confirmed by magnetic resonance angiography (MRA). Six hours after operation, single treatment with 10 mg recombinant tissue plasminogen activator (rtPA)/kg and 6 mg abciximab/kg or subcutaneous injection of 450 IU/kg enoxaparin twice daily was started, each group containing 10 rats. Follow-up MRI with T2- and diffusion-weighted images was performed on the first, second, and seventh postoperative day.

RESULTS

Control and enoxaparin-treated animals developed diffuse brain edema without infarction or intracerebral bleeding. This was indicated by an increase of T2 relaxation time and a decrease of the apparent diffusion coefficient in the parasagittal and lateral cortex. In these groups, the degree of recanalization after 7 days was comparable (48% versus 52%). Enoxaparin-treated animals showed significant amelioration of functional deficits. Clinical outcome was best in the abciximab-treated group, with a residual sinus occlusion of 36% after 1 week. Highest recanalization was achieved by lysis with rtPA (85%).

CONCLUSIONS

Enoxaparin treatment in rats with cerebral venous thrombosis significantly influences clinical outcome. However, it has no effect on recanalization. GPIIb/IIIa antagonists and rtPA accelerate thrombolysis. They may represent an alternative in treatment of cerebral venous thrombosis.

Cerebral venous thrombosis: an all or nothing disease?

BACKGROUND

There is insufficient data on short- and especially long-term prognosis of cerebral venous thrombosis (CVT).

METHODS

In 79 consecutive patients, we analyzed factors for acute death and functional outcome at hospital discharge and after 6 months as well as long-term prognosis >/=12 months. Neurological deficits were graded on the National Institute of Health Stroke Scale (NIHSS), functional outcome on the modified Rankin Scale (mRS). Primary outcome was defined as mRS >/= 3 at 6 months, secondary outcomes were death during hospital treatment and number as well as type of complications during follow-up >/=12 months after hospital discharge. Forty-two patients were recruited prospectively, 37 were identified by chart review. Information on outcome was based on neurological examinations at our outpatient clinic.

RESULTS

Factors significantly related to acute death were age, the NIHSS on admission, more than two seizures despite antiepileptic treatment, venous infarct, and hemorrhagic transformation of the venous infarct. Primary outcome after 6 months in 74 patients was excellent with 73% of patients reaching a mRS 0-1, 4% a mRS of 2, and 23% a mRS 3-6, including 12 deaths in the acute stage of illness. Factors significantly related to a mRS >/= 3 at 6 months in a logistic regression analysis were age and items 1a-c of the NIHSS on admission related to consciousness. Fifty-eight surviving patients had a follow-up >/= 12 months (median: 31; mean: 52 +/- 61 months). Most frequent complication on long-term follow-up was epilepsy in nine patients and recurrent venous thrombosis in seven patients.

CONCLUSIONS

When the acute stage of illness has been survived, CVT has a good prognosis unlike arterial ischemic stroke.

Sinus thrombosis after a jump from a small rock and a sneezing attack: minor endothelial trauma as a precipitating factor for cerebral venous thrombosis?

Cerebral venous thrombosis (CVT) associated with minor or trivial head trauma has only been described in a few cases so far. We report two patients who developed CVT after a sudden intracranial pressure increase and head acceleration. A 49-year-old woman jumped from a small rock, 1 m in height, and developed instantaneous occipital headaches. Magnetic resonance imaging (MRI) confirmed confluens sinuum thrombosis. Risk factors consisted of smoking and oral contraceptives. Our second patient, an 18-year-old woman, experienced instantaneous headaches after a sneezing attack. Superior sagittal and right-sided transverse sinus thrombosis were confirmed by venous computed tomography angiography. She took oral contraceptives as an additional risk factor. In about 20% of CVT cases the cause remains unclear. As minor head trauma may not have been recognized during history taking, this may represent a so far under-recognized precipitating factor for CVT.

CD45RA+ ICAM-3+ lymphocytes in interferon-beta1b-treated and -untreated patients with relapsing-remitting multiple sclerosis

OBJECTIVES

Multiple sclerosis (MS) is believed to be an autoimmune disease of the human central nervous system mediated by autoreactive T cells. Interferon-beta1b (IFN-beta1b) has been shown to be effective in reducing disease activity defined by clinical and magnetic resonance imaging (MRI) criteria in relapsing-remitting MS (RRMS). Yet, the exact mechanisms by which these benefits are achieved remain unknown. CD45RA is a marker for naive T lymphocytes and intercellular adhesion molecule-3 (ICAM-3) is expressed on resting lymphocytes.

MATERIAL AND METHODS

Forty-eight patients with RRMS, 24 of them treated with recombinant IFN-beta1b and 24 untreated, were enrolled in this prospective study over 18 months. We investigated the percentage of CD45RA+ ICAM-3+ cells within the total lymphocyte subset in the peripheral blood serially every 3 months and in CSF once at baseline. Detailed clinical examination including Expanded Disability Status Scale (EDSS) score was performed every 3 months and cranial MRI scans were assessed every 6 months.

RESULTS

We found a temporary increase in the CD45RA+ ICAM-3+ lymphocyte ratio in peripheral blood of both untreated and IFN-beta1b-treated RRMS patients. Moreover, we determined a significant negative correlation (r = -0.5874; P < 0.01) between age as well as the EDSS score (r = -0.3629; P < 0.05) and the percentages of CD45RA+ ICAM-3+ lymphocytes in peripheral blood but a positive correlation between EDSS score and the CD45RA+ ICAM-3+ ratio (r = 0.3913; P < 0.05) in the CSF at baseline.

CONCLUSION

CD45RA+ ICAM-3+ lymphocyte ratio in peripheral blood might indicate immunosenescence in MS. However, from our data it cannot be finally concluded whether it is also influenced by IFN-beta1b treatment.

Complications and pitfalls in rat stroke models for middle cerebral artery occlusion: a comparison between the suture and the macrosphere model using magnetic resonance angiography

BACKGROUND AND PURPOSE

Investigating focal cerebral ischemia requires animal models that are relevant to human stroke. Complications and side effects are common among these models. The present study describes potential pitfalls in 3 techniques for middle cerebral artery occlusion (MCAO) in rats using magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA).

METHODS

Rats were subjected to temporary MCAO for 90 minutes using the suture technique (group I; n=10) or to permanent MCAO using the suture technique (group II; n=10) or the macrosphere technique (group III; n=10). Clinical evaluation was performed after 3 hours and 24 hours. After 24 hours, animals underwent MRI and MRA to determine lesion size and the intracranial vascular status.

RESULTS

Hemispheric lesion volume was significantly smaller in group I (14.6%) compared with groups II (35.2%; P<0.01) and III (21.3%; P<0.05). Two animals (1 each in group II and III) did not demonstrate neurological deficits and had no lesion on MRI and a patent MCA main stem on MRA. Subarachnoid hemorrhage was detected in 2 animals (1 each in group I and II). MRA indicated a patent MCA main stem in 2 animals (group II), although both rats displayed neurological deficits. Hypothalamic infarction with subsequent pathological hyperthermia was detected in all animals in group II and in 1 rat in group III.

CONCLUSIONS

Model failures occurred frequently in all groups. MRI and MRA helps to identify animals that need to be excluded from experimental stroke studies.

Middle cerebral artery occlusion during MR-imaging: investigation of the hyperacute phase of stroke using a new in-bore occlusion model in rats

Magnetic resonance imaging (MRI) provides insights into the dynamics of focal cerebral ischemia. Usually, experimental stroke is induced outside the magnet bore, preventing investigators from acquiring pre-ischemic images for later pixel-by-pixel comparisons and from studying the earliest changes in the hyperacute phase of ischemia. Herein, we introduce a new and easy to apply in-bore occlusion protocol based on the intraarterial embolization of ceramic macrospheres. PE-50 tubing, filled with saline and six macrospheres (0.315-0.355 mm in diameter), was placed into the internal carotid artery (ICA) of anesthetized Sprague-Dawley rats. The animals were transferred into an MRI scanner (7.0 T) and baseline diffusion-weighted imaging (DWI) and T2-imaging was performed. Then the macrospheres were injected into the internal artery to occlude the MCA. Post-ischemic DWI and T2-imaging was started immediately thereafter. The apparent diffusion coefficient (ADC) (a marker for cytotoxic brain edema) and T2-relaxation time (a marker for vasogenic brain edema) were determined in the ischemic lesions and compared to the unaffected hemisphere. ADC significantly declined within the first 5-10 min after stroke onset. T2-relaxation time increased as early as at the first T2-imaging time-point (20-35 min after embolization). After 150 min of ischemia, the lesions covered 18.0 +/- 7.4% of the hemispheres. The model failed in one out of nine animals (11%). This model allows MR-imaging from the initial minutes after permanent middle cerebral artery (MCA) occlusion. It does not permit reperfusion. This technique might provide information about the pathophysiological processes in the hyperacute phase of stroke.

Influence of stimulus duration on the neurovascular coupling response

AIM

The neurovascular coupling mechanism adapts cerebral blood flow in accordance with cortical activity. It reacts rapidly, reliably and in a finely tuned manner. Therefore, the question emerged at to whether this might be a linear mechanism. Recently, non-linearity was concluded from different time curves of flow regulation, resulting from stimulation of varying duration. Short lasting stimulation resulted in a peak response, whereas longer stimulation led to a peak and plateau characteristic of flow response. We suggest the different responses may be caused by dynamic properties of the coupling.

METHOD

A functional transcranial Doppler test was performed using a visual stimulation paradigm in 10 healthy volunteers (age 25.8 +/- 0.5 years, 7 men). Two tests with different stimulus duration were used (20 s versus 40 s). The short test was known to result in the dynamic pattern, and the long test in the static phase of flow regulation. The data from the long test were evaluated according to a control system approach. The resultant model was used to calculate data of an assumed 20 s stimulation. A paired t-test was used to compare the measured and calculated flow data for the short stimulation test.

RESULTS

The flow velocity responses were identical when comparing the first 20 s of stimulation. At the termination of stimulation in the short test, flow velocity returned to baseline leading to a peak response, whereas flow velocity stabilised at a constant level above baseline in the long stimulation paradigm, resulting in the peak and plateau characteristic.

CONCLUSION

The different flow responses due to different stimulus duration are caused by dynamic properties of the coupling mechanism and are not indicative of non-linearity.

Diffusion-Weighted Magnetic Resonance Imaging and Neurobiochemical Markers After Aortic Valve Replacement

Background and Purpose— Cardiac surgery carries a high risk of neurological complications; therefore, these patients would be an appropriate target population for neuroprotective strategies. In this study, we evaluated postoperative diffusion-weighted imaging (DWI) as a potential surrogate marker for brain embolism and its relationship to neurobiochemical markers of brain injury.

Methods— Of a total of 45 consecutive patients undergoing aortic valve replacement, 37 completed preoperative and postoperative MRI. At the time of the MRI studies, serum S100β and neuron-specific enolase concentrations were determined. Preexisting T2 and postoperative DWI lesion volumes were quantified. All patients had a blinded neurological examination before and after operation.

Results— New perioperative DWI lesions were present in 14 patients (38%), of whom only 3 developed focal neurological deficits. Eighteen small lesions were found in the white matter or vascular border zones in all but 2 patients with territorial stroke. The appearance of new DWI lesions correlated with age, pre-existing T2 lesion volume, and postoperative S100β concentrations on days 2 to 4 after surgery. In a forward stepwise canonical discrimination model, only T2 lesion volume was selected as a relevant variable.

Conclusions— The incidence of postoperative DWI lesions in aortic valve replacement is high, and a suitable marker for neuroprotective trials would be a reduction in the number of such lesions. The volume of preexisting T2 lesions is related to the development of perioperative DWI lesions.