Reproducibility of image-based analysis of cerebral aneurysm geometry and hemodynamics: an in-vitro study of magnetic resonance imaging, computed tomography, and three-dimensional rotational angiography.

BACKGROUND AND STUDY AIMS: Image-based computational fluid dynamics (CFD) provides a means for analysis of biofluid mechanical parameters of cerebral aneurysms. This may enable patient-specific rupture risk analysis and facilitate treatment decisions. Application of different imaging methods may, however, alter the geometrical basis of these studies. The present study compares geometry and hemodynamics of an aneurysm phantom model acquired by means of magnetic resonance imaging (MRI), computed tomography (CT), and rotational angiography (3DRA). MATERIALS AND METHODS: The phantom model of a basilaris artery aneurysm was fabricated based on data generated by CT angiography. This model underwent imaging by means of CT, MRI, and 3DRA. We compared the geometrical reconstructions using the original dataset with those obtained from CT, MRI, and 3DRA. Similarly, CFD analyses were performed using the four reconstructions (3DRA, MRI, CT, and original dataset). RESULTS: MRI and the 3DRA-based reconstructions yield mean reconstruction errors of 0.097 mm and 0.1 mm, which are by a factor of 2.5 better than the CT reconstruction. The maximal error for the aneurysm radius (7.11 mm) measurement was found in the 3DRA reconstruction and was 3.8% (0.28 mm). A comparison of calculated time-averaged wall shear stress (WSS) shows good correlations for the entire surface and, separately, for the surface of the aneurysmal sack. The maximal error of 8% of the mean WSS calculation of the whole surface was found for the CT reconstruction. The calculations of the aneurysmal sack mean WSS from the MRI reconstruction were estimated to have a maximal error of 7%. CONCLUSION: All three imaging techniques (CT, MRI, 3DRA) adequately reproduce aneurysm geometry and allow meaningful CFD analyses.

Statistical wall shear stress maps of ruptured and unruptured middle cerebral artery aneurysms.

Haemodynamics and morphology play an important role in the genesis, growth and rupture of cerebral aneurysms. The goal of this study was to generate and analyse statistical wall shear stress (WSS) distributions and shapes in middle cerebral artery (MCA) saccular aneurysms. Unsteady flow was simulated in seven ruptured and 15 unruptured MCA aneurysms. In order to compare these results, all geometries must be brought in a uniform coordinate system. For this, aneurysms with corresponding WSS data were transformed into a uniform spherical shape; then, all geometries were uniformly aligned in three-dimensional space. Subsequently, we compared statistical WSS maps and surfaces of ruptured and unruptured aneurysms. No significant (p > 0.05) differences exist between ruptured and unruptured aneurysms regarding radius and mean WSS. In unruptured aneurysms, statistical WSS map relates regions with high (greater than 3 Pa) WSS to the neck region. In ruptured aneurysms, additional areas with high WSS contiguous to regions of low (less than 1 Pa) WSS are found in the dome region. In ruptured aneurysms, we found significantly lower WSS. The averaged aneurysm surface of unruptured aneurysms is round shaped, whereas the averaged surface of ruptured cases is multi-lobular. Our results confirm the hypothesis of low WSS and irregular shape as the essential rupture risk parameters.

In vitro study of near-wall flow in a cerebral aneurysm model with and without coils.

BACKGROUND AND PURPOSE: Coil embolization procedures change the flow conditions in the cerebral aneurysm and, therefore, in the near-wall region. Knowledge of these flow changes may be helpful to optimize therapy. The goal of this study was to investigate the effect of the coil-packing attenuation on the near-wall flow and its variability due to differences in the coil structure. MATERIALS AND METHODS: An enlarged transparent model of an ACA aneurysm was fabricated on the basis of CT angiography. The near-wall flow was visualized by using a recently proposed technique called Wall-PIV. Coil-packing attenuation of 10%, 15%, and 20% were investigated and compared with an aneurysmal flow without coils. Then the flow variability due to the coil introduction was analyzed in 10 experiments by using a packing attenuation of 15%. RESULTS: A small packing attenuation of 10% already alters the near-wall flow significantly in a large part of the aneurysmal sac. These flow changes are characterized by a slow flow with short (interrupted) path lines. An increased packing attenuation expands the wall area exposed to the altered flow conditions. This area, however, depends on the coil position and/or on the 3D coil structure in the aneurysm. CONCLUSIONS: To our knowledge, this is the first time the near-wall flow changes caused by coils in an aneurysm model have been visualized. It can be concluded that future hydrodynamic studies of coil therapy should include an investigation of the coil structure in addition to the coil-packing attenuation.

[Aneurysmal bone cyst of the ethmoid sinus and skull base in a 3-year old child: a rare location of a benign bone lesion]. / Aneurysmatische Knochenzyste der Rhinobasis bei einem 3-jährigen Kind: Seltene Lokalisation einer benignen Knochenläsion.

Aneurysmal bone cyst is a benign osteolytic lesion in childhood and adolescence which primarily arises in metaphyseal long bones. Its presence in bones of the skull base is very rare. In a 3-year old girl presenting with proptosis, MRI demonstrated a well-defined displacing growing mass in the ethmoid sinus, orbita and anterior fossa. The histopathologic examination of biopsy specimens confirmed an aneurysmal bone cyst. Despite radical surgery the child suffered from two recurrences of the lesion in the first year after initial diagnosis. There has been no subsequent recurrence during the last 3 years. Since this lesion is rarely seen at the skull base, is difficult to differentiate clinically and by histopathology and may take an abnormal course, it is described in this case report to emphasize that it should be included in the differential diagnosis of ENT tumors at this location.

Completely ossified pseudomeningocele, a rare complication after spinal surgery.

BACKGROUND: We report the rare case of an ossified pseudomeningocele following laminectomy. The extradural pseudocyst has completely ossified without an overt communication to the subarachnoid space. CASE REPORT: In 1986, a 41 year-old woman suffered from spinal stenosis at levels L3-5 and was treated by laminectomy. A cerebrospinal fluid (CSF) leakage was observed postoperatively. A follow-up CT scan eleven years after surgery showed an ossified pseudomeningocele in the operated region. However, in our case no surgical resection was performed since the patient suffered only from diffuse back pain without sciatica or any neurological deficit. In 2009 the patient continues to be neurologically intact without a change in clinical complaints. Hence, the file was closed after 23 years without neurosurgical intervention. DISCUSSION: Seven cases of ossified pseudomeningocele have been previously described in the literature and all were operated on. However, our case shows that ossified extradural pseudocysts do not require operation in every case.

Embolization of indirect carotid-cavernous sinus fistulas using the superior ophthalmic vein approach.

OBJECTIVES: In indirect carotid-cavernous sinus fistulas (CCF), abnormal connections exist between tiny dural branches of the external and/or internal carotid system and the cavernous sinus. Usually this kind of fistula occurs spontaneously and is characterized by a low shunt volume. Alternative vascular approaches for embolization are required when standard interventional neuroradiological access via arterial or transfemoral venous routes is not feasible. PATIENTS AND METHODS: Two symptomatic patients with indirect CCFs are described. Transarterial and transfemoral venous approach was unsuccessful or resulted in incomplete occlusion of the CCF. Therefore, the superior ophthalmic vein (SOV) was surgically exposed and retrograde catheterized to allow the delivery of platinum coils to the fistula point via a microcatheter. RESULTS: Complete fistula obliteration was accompanied by recovery of the clinical symptoms. CONCLUSION: The surgical SOV approach might be sufficient when standard neuroradiological procedures do not succeed. The technique is safe and effective when performed by an interdisciplinary team.

[Blood flow in cerebral aneurysms]. / Strömung in cerebralen Aneurysmen.

Saccular aneurysm of the cerebral arteries occur in 1 to 5% of the population; the major risk of this disease is aneurysm rupture causing subarachnoid hemorrhage associated with a mortality rate of 50 to 60%. Two methods exist to treat cerebral aneurysms: neurosurgical clipping at the base of the aneurysm and endovascular introduction of a platin coils. Both methods have advantages and disadvantages. With the knowledge of the flow in an aneurysm it is easier to choose the appropriate method. In this study we simulated the flow in four different aneurysms. The shape of the aneurysms are gained from computertomographic data. The simulated flow in four aneurysms shows the great variability of possible flow patterns.

Treatment of carotid tandem stenosis by combined carotid endarterectomy and balloon angioplasty: technical case report.

OBJECTIVE AND IMPORTANCE: Cervical internal carotid artery disease associated with high-grade carotid siphon stenosis poses a therapeutic challenge. This report describes the combination therapy of carotid end-arterectomy and intraoperative transluminal balloon angioplasty of the carotid siphon. CLINICAL PRESENTATION: A 67-year-old man sustained repeated left hemispheric and retinal transient ischemic attacks. Results of a diagnostic examination, including angiography, disclosed a 70% ulcerative stenosis of the left extracranial internal carotid artery as well as a 90% stenosis of the left intracavernous carotid artery. The decision was made for combined open and endovascular therapy. INTERVENTION: After standard endarterectomy, an introducer for the dilation catheter was placed into the common carotid artery before final closure of the arteriotomy and recirculation. Under intraoperative fluoroscopy, a 3-mm dilation balloon was navigated into the carotid siphon stenosis and inflated several times. A 30% residual stenosis in the carotid siphon was obtained as a final result. The intervention was completed without complications. No further neurological symptoms were observed during the follow-up period of 30 months. CONCLUSION: Carotid endarterectomy, combined with intraoperative transluminal angioplasty of carotid siphon stenosis, is a feasible procedure for selected patients with carotid tandem stenosis.

Herpes simplex encephalitis after brain surgery: case report and review of the literature.

Intracranial infection after neurosurgical intervention most often is caused by bacteria. A rare case of fatal herpes simplex encephalitis after removal of a meningioma is described and similar cases reported in the literature are reviewed. Recent diagnostic tools, including detection of herpes viral DNA sequences by polymerase chain reaction, complement clinical suspicion and facilitate mandatory early diagnosis, because herpes encephalitis, without rapid initiation of treatment, may lead to severe disability or death.

[Calculation of absolute cerebral blood volume and cerebral blood flow by means of electron-beam computed tomography (EBT) in acute ischemia]. / Berechnungen des absoluten zerebralen Blutvolumens und des zerebralen Blutflusses mit der Elektronenstrahltomographie (EBT) bei akuten Ischämien.

The utility of electron beam computed tomography (EBT) to estimate cerebral blood volume (CBV) and cerebral blood flow (CBF) was evaluated. Eleven patients with suspected acute cerebral ischemia were investigated. The EBT was performed with an acquisition time of 50 ms per slice at eight parallel levels. To compare signal/noise and contrast/noise ratios the data from the EBT investigation were compared to a similar examination on a spiral CT. The signal/noise ratio with EBT was about 30%, the contrast/noise ratio 25% of that with spiral CT. The absolute values of CBV were 4.9 +/- 1.2 ml/100 g (EBT); CBF was 50.5 +/- 7.0 ml/100 g/min in normal contralateral brain tissue. In four patients with proven infarcts on follow-up, the ischemic areas had a CBV ranging from 1.7 to 3.8 ml/100 g, while CBF ranged from 9.4 to 24.5 ml/100 g/min. Using a bolus injection of contrast material, calculation of absolute CBV and CBF is feasible using EBT. Advantages of EBT are the absolute measurements possible and it's multislice capability. Disadvantages, however, are caused by the high image noise, limiting the demarcation of ischemic tissue.

Saccadic dysmetria and "intact" smooth pursuit eye movements after bilateral deep cerebellar nuclei lesions.

Two patients with well defined lesions of midline cerebellar structures including the fastigial nuclei on both sides presented with saccadic hypermetria but well preserved smooth pursuit eye movements. This is a remarkable finding as the oculomotor vermis (lobules VI, VII) and the fastigial nucleus are known to play a part in the control of smooth pursuit eye movements and unilateral fastigial lesions lead to a smooth pursuit deficit to the contralateral side (besides saccadic dysmetria). The results are discussed with regard to related deficits seen in patients with Wallenberg's syndrome and after lesions of the pontine reticular formation.

K+ channel openers suppress myotonic activity of human skeletal muscle in vitro.

Isolated fibre bundles from myotonic human skeletal muscle showed after-contractions and spontaneous mechanical activity. The K+ channel openers cromakalim (10-100 mumols/l) and EMD 52962 (1-10 mumols/l) completely suppressed these abnormalities in mechanical activity. Voltage-clamp experiments revealed that cromakalim (100 mumols/l) increased the membrane K+ conductance of isolated, non-myotonic human skeletal muscle fibres 4-fold; Cl- conductance was not altered. The data show that myotonia is suppressed by an increase in in membrane K+ conductance.

Cytosolic calcium during glucose deprivation in hippocampal pyramidal cells of rats.

Glucose deprivation (GD) results in a hyperpolarization by turning on a potassium conductance (gK,GD) in hippocampal CA3 pyramidal cells. We used combined intracellular and microfluorometric recording techniques to evaluate whether gK,GD is activated by a rise in the concentration of intracellular calcium ([Ca2+]i). We found that the activation of gK,GD is only followed, but not preceded by a rise in [Ca2+]i. Furthermore, gK,GD is not blocked by the sulfonylurea glibenclamide, a blocker of ATP-regulated potassium conductance. We conclude that activation of gK,GD does not simply reflect breakdown of the calcium of ATP homeostasis, but on the contrary might represent an active restoring mechanism which delays the pathological consequences of sustained glucose deficiency.

Acetylcholinesterase reactivators antagonize epileptiform bursting induced by paraoxon in guinea pig hippocampal slices.

The electrophysiological actions of paraoxon, an irreversible blocker of acetylcholinesterase, and their antagonism by a series of organophosphate cholinesterase reactivators, were studied in area CA1 of the guinea pig hippocampus in vitro. To avoid indirect effects elicited by excitation of CA3 neurons, the CA2/3 regions were removed routinely before the recording of extracellular field potentials in CA1. Under these conditions, paraoxon (1 microM) induced regular burst activity (rate, 2-10/min; amplitude, 0.2-1 mV; duration, 100-500 msec). The antagonism of this burst activity by atropine (0.3-1.0 microM) and pirenzepine (1.0 microM) suggested the involvement of muscarinic cholinoceptors in the mediation of this response. The reduction in frequency of paraoxon-induced bursting by the cholinesterase reactivators was taken as an index of their efficacies. The four oxime compounds tested were all active in the low micromolar range (rank order of potencies: obidoxime greater than HGG 12 = HLö 7 greater than Hl 6). In experiments without paraoxon, these oximes did not depress either evoked population spikes in normal artificial cerebrospinal fluid or bursts induced by superfusion with Mg++-free artificial cerebrospinal fluid. Thus, an unspecific inhibitory effect of oximes can be excluded. It is concluded that the in vitro hippocampus provides a suitable system for the quantitative electrophysiological evaluation of cholinesterase reactivators in the central nervous system.

Adenosine, 'pertussis-sensitive' G-proteins, and K+ conductance in central mammalian neurones under energy deprivation.

There is a striking similarity between the effects of adenosine and of hypoxia or glucose depletion on membrane potential and conductance of hippocampal neurones in tissue slices of rat brain. Both induce a membrane hyperpolarization by an increase in potassium conductance. It seemed likely, therefore, that a rise in extracellular adenosine concentration during energy deprivation may link neuronal metabolism with membrane K+ conductance. To test this hypothesis, we have now investigated the effects of hypoxia/glucose deprivation on hippocampal neurones from pertussis toxin-treated rats. In such slices adenosine had no effect on postsynaptic membrane potential and input resistance. Nevertheless, hypoxia or glucose depletion were as effective as in controls. These data provide evidence against adenosine as the main mediator between cell metabolism and potassium conductance.

Cromakalim (BRL 34915) restores in vitro the membrane potential of depolarized human skeletal muscle fibres.

The purpose of the present study was to analyze the effects of cromakalim (BRL 34915), a potent drug from a new class of drugs characterized as "K+ channel openers", on the electrical activity of human skeletal muscle. Therefore, intracellular recordings were used to measure the effects of cromakalim on the membrane potential and input conductance of fibres from human skeletal muscle biopsies. Cromakalim in a concentration above 1 mumol/l induced an increase in membrane K+ conductance. This effect resulted in a membrane hyperpolarization. The magnitude of this polarization depended on the difference between resting and K+ equilibrium potential. The effect had a rapid onset and was quickly reversible after washing. Fibres from two patients with hyperkalaemic periodic paralysis showed an excessive membrane depolarization during and also after exposure to an slightly elevated extracellular K+ concentration. In the latter situation, cromakalim repolarized the fibres to the normal resting potential. Tolbutamide (1 mmol/l) and Ba2+ (3 mmol/l) strongly antagonized the effect of cromakalim. The data show that cromakalim hyperpolarizes depolarized human skeletal muscle fibres maintained in vitro. The underlying mechanism is probably an activation of otherwise "silent", ATP-regulated K+ channels. Such an effect may be of therapeutic benefit in a situation in which a membrane depolarization causes muscle paralysis.