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Biomedical subjects

H J Steiger

Publications and source records attributed to H J Steiger.

At least 91 records · Page 5Linked to original sources
PubMed1989

Radical resection of superior sagittal sinus meningioma with venous interposition graft and reimplantation of the rolandic veins. Case report.

A case of a 48 year old women is reported in whom a haemangiopericytic meningioma involving the middle third of the superior sagittal sinus was radically excised. The sinus was replaced by a saphenous vein graft and the Rolandic veins were reinserted. During clamping of the sinus the patient was heparinized and hypothermia, hypotension and barbiturates were used to prevent swelling of the brain. The postoperative course was uncomplicated and patency of the graft was demonstrated 2 weeks after the operation by Doppler sonography performed through a midline burr hole. The technical details of the operation and the pertinent physiology of cerebral venous flow are discussed.

Cranial Sinuses↗
PubMed1989

Results of microsurgical carotid endarterectomy. A prospective study with transcranial Doppler and EEG monitoring, and elective shunting.

100 consecutive carotid endarterectomies in a total of 93 patients were performed using the operative microscope. Cerebral perfusion and activity were monitored with simultaneous transcranial Doppler (TCD) and EEG. Thiopentone for cerebral protection was given prior to carotid clamping in 11 cases when an insufficient collateral circulation was suspected on the basis of the pre-operative TCD or angiography and if temporary intraluminal shunting was to be avoided because of a high bifurcation, long stenosis or associated carotid artery kinking. A temporary intraluminal shunt was inserted electively if the mean middle cerebral artery flow velocity fell after cross-clamping below 30-40%. Direct closure of the arteriotomy was preferred over a patch graft, which was performed only in cases with concomitant stricture of the arterial wall. No peri-operative strokes occurred in the present series. Two patients died due to medical complications in the post-operative period. During the mean follow-up of 15 months, 1 patient suffered a lethal stroke ipsilateral to the treated carotid artery and another patient had a minor contralateral stroke. Two patients died of unrelated causes during follow-up. Two patients suffered a single reversible neurologic deficit corresponding to the treated carotid territory. Four other patients had a single contralateral hemispheric or retinal reversible ischaemic attack during follow-up.

Adult↗
PubMed1989

Growth of aneurysms can be understood as passive yield to blood pressure. An experimental study.

The strength of aneurysm walls obtained intraoperatively or at autopsy immediately after death was evaluated by measurements of the force response to one-directional stretch and compared to the walls of intracranial arteries. The maximum stress that aneurysm tissue could tolerate was found slightly lower than in arteries, which is most probably due to the amount of immature forms of collagen. The stress resistance of aneurysms and arterial tissue decayed over a period of several hours. The relaxation curve could be approximated by the sum of 2 exponential terms. The half decay times of these terms were found identical in aneurysms and arteries, they appear to be collagen characteristics. The strength measured in vitro was compared to the stress in vivo, which was calculated on the basis of blood pressure and aneurysm radius. The stress tolerated by aneurysm walls over a period of 24 hours was found to be in the range of the stress that is imposed in vivo by the mean blood pressure. Arteries resisted stresses corresponding to pressures 10 to 20 times higher than physiological values. The thickness of the aneurysm walls correlated with the aneurysm radius in a linear fashion. It is suggested that aneurysm growth can be understood as passive yield to blood pressure, and reactive healing and thickening of the wall with increasing aneurysm diameter.

Biomechanical Phenomena↗
PubMed1989

Strength, elasticity and viscoelastic properties of cerebral aneurysms.

Tissue strength and stiffness of cerebral aneurysm walls obtained intraoperatively or at autopsy were evaluated by uniaxial strain/stress measurements. For comparison, corresponding measurements were also made on autopsy specimens of intracranial arteries. The maximum stress that the aneurysm tissue could tolerate, the yield stress, was found to be slightly lower than in arteries, which is likely due to the content of immature forms of collagen. The material stiffness, as determined by division of the yield stress by the corresponding strain, was also smaller in aneurysms than in arteries. The stress resistance of aneurysms and arterial tissue decreased over a period of several hours. The relaxation curves were found to be identical in aneurysms and arteries. The stress tolerated by aneurysm walls was found to be in the range of the stress that is imposed in vivo by the blood pressure. Arteries resisted stresses corresponding to pressures 5-10 times higher than physiological values. It is suggested that the balance of tissue strength and the stress imposed by the blood pressure is causally related to aneurysm growth.

Adult↗
PubMed1988

[Cerebral cavernoma as a cause of recurrent cerebral hemorrhage and epileptic insults].

Cerebral cavernous angiomas or cavernomas have been increasingly diagnosed in recent years as a cause of recurrent cerebral hemorrhage or epilepsy. Some cavernomas exhibit a tumorous growth tendency. On CT-scan, cavernomas appear as variably cystic lesions often with focal calcifications. The lesion may be masked by a surrounding hematoma. Seventeen cases were observed initially or on follow-up within 3 years. Examination of the surgical specimens allowed differentiation of the lesions into several subtypes correlating to the different clinical courses. The diagnosis of cavernomas is important since these lesions can be cured surgically. The spontaneous clinical course, however, is usually progressive.

Adolescent↗
PubMed1988

Haemodynamic stress in terminal aneurysms.

The flow velocities in glass and silastic aneurysm models located at bifurcations were quantitatively determined using the non-invasive laser-Doppler method. The geometrical relation between aneurysm and parent vessels was found to be the primary factor governing the intra-aneurysmal flow pattern. Flow was stagnant in straight terminal models, with the aneurysm forming an extension of the afferent vessel, as long as the outflow through the branches of the bifurcation was balanced. Average flow velocities in the fundus were small but turbulent flow fluctuations of high amplitudes were observed. Asymmetric outflow through the branches of the bifurcation induced a rotatory intra-aneurysmal circulation from the dominant to the subordinate branch. The circulation in angled terminal aneurysms with the aneurysmal axis at a 45 degree angle to the plane of the bifurcation was a vortex, which was a natural consequence of the excentric inflow from the afferent vessel. Maximum flow velocities measured in the centre plane of the angled terminal aneurysms were in the range of 50 to 80% of the axial velocity in the afferent vessel. The elasticity of the models did not affect the global turnover rates but it damped the intra-aneurysmal pulse wave. On the basis of the measured velocity gradients near the walls maximum shear stresses on the wall of human terminal aneurysms were estimated to be in the order of 50 dynes/cm2 (5 Pascal), a value that is similar to the maximum wall shear stresses estimated for lateral aneurysms.

Brain↗
PubMed1988

Hemodynamic stress in terminal saccular aneurysms: a laser-Doppler study.

The flow conditions and the related stresses in glass and silastic model aneurysms located at bifurcations were quantitatively determined by means of laser-Doppler-anemometry. The flow velocities in straight terminal models with the aneurysm forming an extension of the afferent vessel were unstable if the outflow through the branches of the bifurcation was balanced. Average flow velocities in the fundus were small, but irregular flow fluctuations of high amplitudes were observed. Asymmetrical outflow through the branches of the bifurcation induced a rotatory intra-aneurysmal circulation from the dominant to the subordinate branch. The circulation in angled terminal aneurysms with the aneurysmal axis at a 45 degree angle to the plane of the bifurcation was a vortex caused by the eccentric inflow from the afferent vessel. Maximum flow velocities measured in the center plane of the angled terminal aneurysms were in the range 50%-80% of the axial velocity in the afferent vessel. The present results indicate that the geometrical relation between aneurysm and parent vessels is the primary factor governing the intra-aneurysmal flow pattern. The elasticity of the models did not affect the average flow velocities, but the intra-aneurysmal pulse wave was damped in elastic models. On the basis of the measured velocity gradients near the walls, maximum shear stresses on the wall of a typical human terminal aneurysm were estimated to be in the order of 50 dyne/cm2 (5 Pascal), a value that is similar to the shear stresses that occur at the flow divider of a cerebral artery bifurcation. This is based on absolute flow velocity measurements in patients [8, 13].

Blood Flow Velocity↗
PubMed1988

[Treatment of traumatic carotid dissection].

Twelve traumatic internal carotid artery dissections were seen within a three-year period. All dissections were diagnosed upon onset of neurological deficits, although, seen retrospectively, there had been warning signs such as partial Horner's syndrome and neck pain, in the majority of cases prior to the neurological deficits. Panangiography and transcranial Doppler ultrasound were used to assess the cerebral haemodynamic situation. In only 3 of the 12 cases evidence of insufficient collateral circulation to the compromised carotid artery distribution was found, but radiological and Doppler sonographic signs of embolism to the middle cerebral artery were seen in the majority of patients. All patients were anticoagulated immediately following diagnosis. No primary reconstructive surgical procedures were performed. Five patients died within few days of massive cerebral infarction and the remaining 7 patients made a partial or complete recovery. Autoptic evidence for thrombo-embolic deposits in the middle cerebral or internal carotid artery was found in all 5 fatal cases at post mortem examination. Recanalisation of the dissected artery occurred within weeks in the majority of the surviving patients. The present series suggests that early diagnosis and immediate anticoagulation is the most important single factor for prognosis in traumatic carotid artery dissections.

Adolescent↗
PubMed1988

Outcome of aneurysmal subarachnoid hemorrhage in a hospital population: a prospective study including early operation, intravenous nimodipine, and transcranial Doppler ultrasound.

A total of 153 consecutive patients with proven aneurysmal subarachnoid hemorrhages (SAHs) admitted immediately after diagnosis regardless of clinical condition were managed according to the same protocol. The initial evaluation included computed tomography (CT), transcranial Doppler ultrasound (TCD), angiography-CT, and/or angiography. Intravenous nimodipine (2 mg/hour) was started after confirmation of the diagnosis. The timing of operation was determined individually according to age, clinical course, and CT and TCD findings. Twenty-one Grade V patients treated with intensive care and ventriculostomy died or did not improve within 24 hours after SAH. Three patients with life-threatening intracerebral hematomas underwent emergency operation. Operation was early in 55 good risk patients and late in 57 patients because of poor initial grade, late admission, or logistic reasons. Seventeen patients had no operation because of old age, persistent poor clinical condition, medical complication, or lethal rebleeding before operation. In the total series, 90 patients (59%) made a full recovery, the overall morbidity rate was 14% (21 of 153 cases), and the mortality rate was 27% (42 of 153). Postoperative mortality including emergency evacuation of hematomas was 7.8% and mortality after elective operation was 6.2%. The causes of disability and death were the initial effect of the hemorrhage in 25 patients (16.3%), rebleeding in 15 (9.8%), delayed cerebral infarction in 8 (5.2%), surgical complications in 7 (4.5%), hydrocephalus in 4 (2.6%), and medical complications in 4 (2.6%).

Adolescent↗
PubMed1987

Accuracy of high resolution computed tomography in direct diagnosis of cerebral aneurysms.

With high resolution computed tomography (CT) of the skull, performing rapid series of 1.5 mm slices during an intravenous bolus injection of contrast medium, an angiography-like image (angio-CT) of the basal cerebral arteries can be obtained. From 76 consecutive angiographically or autopsy-verified cerebral aneurysms of various size down to 3 mm in diameter, 74 (97.4%) were shown up by the angio-CT. One ruptured and one incidental aneurysm escaped CT visualization. Besides the correct localization of the aneurysms, angio-CT provides information concerning the size and main direction of the aneurysms and yields, in addition, a coronal view of the aneurysms and their surrounding structures. Pitfalls for mis-diagnosis can be the following: Aneurysms of below 5 mm in diameter, located at the supraclinoid part of the carotid artery, multiple or non-ruptured aneurysms, bony or movement artefacts, poorly contrasted vessels due to wrong injection technique of contrast medium or vasospasm, and incorrect interpretation.

Cerebral Angiography↗
PubMed1987

Haemodynamic stress in lateral saccular aneurysms. An experimental study.

The flow velocities in lateral glass and silastic aneurysm models were quantitatively measured with the non-invasive laser Doppler method. The influences of the elasticity of the wall, the pulse wave and the properties of the perfusion medium on the intra-aneurysmal circulation were investigated. As shown previously, the inflow into the aneurysm arose from the downstream lip and was directed toward the centre of the fundus. Backflow to the parent vessel took place along the walls of the fundus. With non-pulsatile perfusion, flow velocities in the centre of the standardized aneurysms varied between 0.4 and 2% of the maximum velocity in the parent vessel. With pulsatile perfusion, flow velocities in the centre of the fundus ranged between 8 and 13% of the flow velocity in the axis of the parent vessel. Flow velocities in the aneurysms were slower with a macromolecular perfusion medium with blood like properties compared to a glycerol/water solution. Flow velocity measurements near the aneurysmal wall allowed the estimation of the shear stresses at critical locations. The maximum shear stresses at the downstream lip of the aneurysm were in the range of the stresses measured at the flow divider of an arterial bifurcation. The present results suggest that in human saccular aneurysms intra-aneurysmal flow and shear stress on the wall are directly related to the pulsatility of perfusion, i.e. the systolic/diastolic pressure difference and that the tendency to spontaneous thrombosis depends on the viscoelastic properties of the blood, namely the haematocrit.

Blood Flow Velocity↗
PubMed1987

Basic flow structure in saccular aneurysms: a flow visualization study.

Basic flow patterns were investigated in a set of glass aneurysm models by means of flow visualization methods. Dye injection and streaming double refraction were used to visualize flow. The circulation inside lateral aneurysms arising at a 90 degree angle from a straight parent conduit could not be visualized by the dye-injection technique but could be demonstrated by streaming double refraction. The inflow was seen to arise from the downstream lip of the orifice and to project to the dome of the aneurysm. Backflow to the parent conduit took place along the walls of the aneurysm. In aneurysms located at bifurcations, flow characteristics depended on the geometry of the bifurcation and the flow ratio between the branches. Relatively little intra-aneurysmal flow was demonstrated in side branch-related aneurysms arising distal to an asymmetric 90 degrees bifurcation of the type encountered at the junction of the internal carotid and posterior communicating arteries. Stagnation of flow at the neck and little intra-aneurysmal circulation were found with terminal aneurysms of the basilar bifurcation type if the outflow through the branches was symmetric. With asymmetric outflow, however, or if the axis of the aneurysm did not coincide with that of the afferent vessel, an active rotation developed in these aneurysms. The size of the aneurysm had no influence on the basic pattern of intra-aneurysmal circulation. The use of pulsatile perfusion did not significantly alter the basic flow patterns observed with steady flow. Locally disturbed laminar flow was observed in certain models at physiological Reynold's numbers, but there were no signs of fully developed turbulence.

Coloring Agents↗
PubMed1987

Clinicopathological relations of cerebral cavernous angiomas: observations in eleven cases.

Eleven cases of cerebral cavernous angiomas (cavernomas) were observed within a period of 3 years. Two patients presented with cerebral hemorrhage, five with epilepsy, three each with a progressive focal neurological deficit, and one with papilledema. The unruptured lesions had a heterogeneous density on computed tomography with relatively little contrast enhancement. Two lesions contained major cysts. In one of these cases, the cyst measured 5.5 cm in diameter, had an enhancing membrane, and was surrounded by brain edema. Angiography did not show hypervascularity in any instance. During exploration and histological processing, special attention was paid to signs of previous silent hemorrhages and to the degree of encapsulation of the lesion. Iron deposits (signs of previous hemorrhages) were seen to varying degrees inside all cavernomas as well as in the surrounding gliotic cerebrum, and a causal relation between iron deposits and epileptic seizures seems likely. Encapsulation was minimal with the ruptured cavernomas and particularly prominent with the cystic lesions. The membrane of the giant cystic lesion with peripheral brain edema had a histological structure similar to that of the membranes of chronic subdural hematomas. It is suggested that continuous growth of cavernoma cysts is the result of recurrent hemorrhages from sinusoids of the malformation and from the neocapillary network of the cyst membranes.

Adolescent↗
PubMed1987

Hemodynamic stress in lateral saccular aneurysms.

The flow velocities in glass and silastic lateral aneurysm models were quantitatively measured with the non-invasive laser Doppler method. The influences of the elasticity of the wall, the pulse wave and the properties of the perfusion medium on the intra-aneurysmal circulation were investigated. As shown previously, the inflow into the aneurysm arose from the downstream lip and was directed toward the center of the fundus. Backflow to the parent vessel took place along the walls of the fundus. With non-pulsatile perfusion, flow velocities in the center of the standardized aneurysms varied between 0.4 and 2% of the maximum velocity in the parent vessel. With pulsatile perfusion, flow velocities in the center of the fundus ranged between 8 and 13% of the flow velocity in the axis of the parent vessel. Flow velocities in the aneurysms were slower with a polymer suspension with blood-like properties compared to a glycerol/water solution. Flow velocity measurements near the aneurysmal wall allowed the estimation of the shear stresses at critical locations. The maximum shear stresses at the downstream lip of the aneurysm were in the range of the stresses measured at the flow divider of an arterial bifurcation. The present results suggest that in human saccular aneurysms intra-aneurysmal flow and shear stress on the wall are directly related to the pulsatility of perfusion, i.e. the systolic/diastolic pressure difference and that the tendency to spontaneous thrombosis depends on the viscoelastic properties of the blood, namely the hematocrit.

Blood Flow Velocity↗
PubMed1986

[Headache and the somatotopic organization of Gasser's ganglion].

Some headaches of organic nature can be readily attributed to excitation of nerve terminals or receptors located in distinct intracranial structures. The trigeminal system mediates most of the intracranial pain sensation. Modern tracer methods have investigated the somatotopic organization of meningeal sensation in the Gasserian ganglion. The dura mater is supplied by the trigeminal divisions sectorially, in a similar manner to the face. Although the notion of somatotopic representation of the meninges in the Gasserian ganglion may suggest possible surgical intervention for intractable headache at the level of the Gasserian ganglion, separation of the facial and corneal representation from the meningeal cell pool is not sharp enough to avoid facial dysesthesias.

Animals↗
PubMed1986

Low frequency flow fluctuations in saccular aneurysms.

Intra-operative Doppler recordings were carried out on cerebral saccular aneurysms in 12 patients. Distinct fluctuations of flow superimposed on the pulse wave were seen in 6 patients. The fluctuations appeared to be periodic with measured period lengths of 60 to 150 msec. In 3 other patients flow irregularities could be discerned acoustically but a definite periodicity could not be visualized on screen. In 3 patients flow appeared smooth during the entire pulse cycle, acoustically as well as visually. Concomitant flow observations in glass model aneurysms also revealed flow instabilities in certain aneurysm types at a Reynold's number of 300. All observed irregularities of flow were observed in zones of deceleration of flow in the models. Signs of fully developed turbulence were not found, neither in human aneurysms nor in the glass models. It appears likely that the fluctuations of flow induce vibrations of the aneurysmal wall and contribute to aneurysm progression and eventual rupture.

Cerebrovascular Circulation↗
PubMed1986

High resolution CT angiography in the direct diagnosis of cerebral aneurysms.

By performing a rapid series of 1.5 mm slices, with high resolution CT angiography (angio-CT), after intravenous bolus injection of 100 ml of contrast medium, an image of the basal arteries similar to that of conventional angiography may be obtained. A consecutive series of 102 patients with suggested cerebral aneurysms were examined by angio-CT and, as a control, were also studied with selective four-vessel angiography and/or at autopsy. In 33 patients angiography or autopsy revealed no aneurysm; 69 patients were shown to have 76 aneurysms. The angio-CT was correctly negative in 30 patients (91%), falsely suggested in 2 (6%), and falsely positive in 1 patient (3%). Sixty-eight aneurysms (89%) of down to 3 mm in size were correctly demonstrated by angio-CT, 6 (8%) were correctly suggested, and 2 aneurysms (3%) escaped CT demonstration.

Cerebral Angiography↗