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Biomedical subjects

H Brückmann

Publications and source records attributed to H Brückmann.

At least 73 records · Page 4Linked to original sources
PubMed1987

The subcortical generated somatosensory evoked potentials in non-cephalic, cephalic, and anterior neck referenced recordings in a patient with a cervico-medullary lesion: a clue to the identification of the P14/N14 and N13 generators.

Median nerve somatosensory evoked potentials (SEPs) were studied in a patient before and after the development of a cervico-medullary lesion. The first examination demonstrated normal subcortical generated potentials N13 and N14. The second examination, following a subarachnoid haemorrhage at the cervico-medullary junction, displayed a delayed and reduced amplitude P14/N14 peak on both sides. P14/N14 showed the same latency in all montages, using non-cephalic, cephalic and anterior neck references. The N13 component was not significantly changed in latency compared with the first examination. The latencies of the N13 peak were variable in the different montages. They increased from the lower (C7) to the upper (C2) neck, whereas the latency of the N13 onset was identical in all montages. This alteration might be caused by a delayed near-field activity at C2 overlapping the N13 component. These results fit the hypothesis of two major generators responsible for subcortical SEPs; a near-field N13 component at the level of the lower neck and a far-field P14 component arising from the level of the cervico-medullary junction. An additional minor near-field activity generated by the cuneate nucleus is suspected.

Adult↗
PubMed1987

Carotid endarterectomy: factors influencing perioperative complications.

Early carotid surgery has been suggested to be an important cause of perioperative deterioration due to secondary haemorrhage into a recent brain infarction. It has also been suggested that the existence of preoperative neurological deficits may worsen the prognosis of surgical treatment in carotid disease. Neither of these observations could be confirmed; severe perioperative complications (5%) in this study of carotid endarterectomy were strongly related to the degree of carotid stenosis. This aspect of carotid surgery has not been previously studied. Even though technical difficulties may play an exaggerated role in a training hospital system, it is nevertheless necessary to assess the impact of surgical procedures of different extent when the "acceptable risk" for carotid surgery is calculated.

Adult↗
PubMed1987

"Distal stump" of the internal carotid artery with ascending pharyngeal artery collateralisation. A potential source for further embolic ischemia.

In 2 patients, clinically exhibiting recent amaurosis fugax and small cortical infarction, carotid occlusion had been shown by means of doppler ultrasound. IA-DSA showed a collateral circulation within the distal carotid artery in the base of the skull via the ascending pharyngeal artery. The slowly perfused stump of a distal carotid artery is supposed to be a potential source of emboli into the retinal or intracranial territories.

Carotid Artery Diseases↗
PubMed1987

[Significance of vertebral angiography for the diagnosis and therapy of vertebrobasilar occlusive disorders with special reference to vascular recanalizing procedures].

Between 1980 and 1985 a total of 912 vertebral angiographies were performed in 793 patients, 198 of whom had ischemic symptoms attributable to the hindbrain circulation. The complication rate was 6%. With due consideration for the clinical findings and those recorded by Doppler ultrasound and computed tomography, vertebral angiography is indicated in vertebrobasilar occlusive disease if anticoagulation, percutaneous transluminal angioplasty (PTA) or local intraarterial fibrinolytic therapy (LIF) of the hindbrain circulation is intended, and also if there is a discrepancy between the clinical findings and the results of computed tomography or Doppler ultrasound examination. With today's sophisticated angiographic techniques (e.g. DSA) and the possibilities opened up by modern interventional neuroradiological techniques, the complication rate of vertebral angiography now seems to be lower than previously.

Angioplasty, Balloon↗
PubMed1987

[Dependence of the risk of brain infarct on the degree of severity of occlusive internal carotid artery lesions].

This retrospective study was performed in order to evaluate the relationship between the risk of brain infarction and the severity of 274 internal carotid artery (ICA) stenoses in 218 patients. Clinical, vascular and brain-morphological findings were compared. Of 106 occluded ICAs, 59% had induced a completed stroke with visible hemispheric infarction in 77%, most of them of the territorial type (35%). 32% of 85 high-grade stenoses had led to completed strokes, with territorial, low-flow and microangiopathic patterns of infarction occurring equally frequent. CT was normal in two-thirds of 83 low-grade ICA-stenoses, whereas 14% showed microangiopathic brain lesions. We conclude that (1) asymptomatic ICA stenoses should not be operated on, as long as they are not of very high degree and (2) even symptomatic ICA stenoses should not undergo endarterectomy, if the patient's stroke was due to lacunar infarctions of typical site and size.

Carotid Artery Diseases↗
PubMed1986

Percutaneous transluminal angioplasty of the vertebral artery. A therapeutic alternative to operative reconstruction of proximal vertebral artery stenoses.

Percutaneous transluminal angioplasty (PTA) of the proximal vertebral artery was performed in 13 patients with stenosis of the proximal vertebral arteries. All of these patients had symptoms indicating vertebrobasilar insufficiency. PTA was performed only if an extreme reduction of the total diameter of both vertebral arteries was present. Only 13 patients have fulfilled the strict selection criteria in the last 3 years. All patients were monitored during the procedure by means of continuous-wave Doppler ultrasound and electrophysiological techniques. After PTA their neurological and vascular conditions were serially examined. Of the 13 patients, 8 showed marked improvement of both subjective and objective clinical symptoms. During an observation period of 2-25 months (average: 15 months) reocclusion of the angioplasty was observed in only 2 cases, without any additional neurological sequelae. Electrophysiological and Doppler sonographic monitoring during PTA helped to minimize the risk of angioplasty.

Angioplasty, Balloon↗
PubMed1986

[Atraumatic diagnosis and semi-invasive therapy of subclavian steal syndrome using percutaneous transluminal angioplasty. A current concept].

Percutaneous transluminal angioplasty (PTA) is a semiinvasive, non-operative transvascular technique for dilatation of stenosed vessel segments by help of balloon catheters. This technique was applied to 30 out of 42 patients with a subclavian steal mechanism due to highgrade proximal subclavian artery (PSA) lesions. The transfemoral, transaxillary or both approaches were used. A staging of the severity of the subclavian steal mechanism on the basis of the pre-interventional Doppler ultrasound findings (Grade I-IV) was proposed for adequate selection of patients for angioplasty. During balloon dilatation of the subclavian artery permanent CW Doppler monitoring of the ipsilateral vertebral blood flow velocity was performed at the mastoid. Balloon dilatation failed to be effective in 4 patients with complete subclavian artery occlusions (Stage IV). In 26 patients with high-grade stenoses of the proximal subclavian artery (Stage II/III), angioplasty led to recanalisation of the vessel and abolishment of the steal mechanism. However, relief or improvement of the concomitant subclavian steal syndrome could not be achieved except in one-third or two-thirds of the patients, respectively. Long term follow-up with repeat Doppler sonography indicated a complete removal of the subclavian lesions in 50% of the cases, whereas the remaining patients produced some kind of re-stenosis. However, repeat angioplasty became necessary in only 5 cases and was permanently successful in two of them. If patients with complete subclavian artery occlusions were excluded, the complication rate due to angioplasty was very low. Embolism into the finger arteries could only be observed once. In another case, accidental dissection and complete occlusion of the distal subclavia artery occurred but underwent spontaneous recanalisation. Doppler monitoring of vertebral flow velocity was very useful for both control of the effectiveness of the dilatation procedure and deeper insight into the pathophysiology of the subclavian steal mechanism. An unexpected delay phenomenon concerning the re-establishment of cephalad vertebral flow direction was observed immediately after recanalisation of the subclavian artery and was thought to protect the posterior circulation against early embolism due to mobilisation of plaque debris within the proximal subclavian segment. From an angiological point of view, the outcome of percutaneous transluminal angioplasty does not yet meet the success rates of various modern extra-thoracic surgical procedures for operative treatment of subclavian steal mechanism. However, the rate of improvement of clinical signs and symptoms is equal with both methods.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Acute vertebral-basilar thrombosis. Angiologic-clinical comparison and therapeutic implications.

The clinical-angiologic data and the clinical outcome in 66 patients with acute vertebro-basilar thrombosis treated with antiplatelet agents, anticoagulants, or fibrinolytic agents are presented. Forty-three patients were treated with local intraarterial infusion of streptokinase or urokinase proximal to the thrombotic occlusion; 14 patients in this group (33%) survived, only one of whom was in deep coma when therapy was started. Twenty-three patients did not receive fibrinolytic therapy; 4 of these patients (17%) who exhibited mild brainstem-related symptoms survived. This study implies that early diagnosis and treatment in vertebrobasilar stroke in progression may achieve improved survival.

Acute Disease↗
PubMed1986

[Neuroradiologic and surgical treatment of a recurrent angiofibroma supplied by the internal carotid artery].

If blood supply to the brain hemisphere is disturbed following closure of internal homolateral carotid artery tumors of the skull base with involvement of this artery should not be operated on radically. The authors describe the electrophysiological monitoring of cortical evoked somato-sensory potentials. If there is no alteration of the evoked potentials after preliminary reversible blockade of the internal carotid artery this vessel can be definitely closed using a detachable balloon. Thereafter the whole tumor including the carotid artery can be removed. The authors describe a case of juvenile angiofibroma operated on in this way. The combined interventional-neuroradiological and surgical management widens the range of skull base surgery.

Adult↗
PubMed1986

[Validity of early acoustically-evoked potentials in the diagnosis of brain death].

Brainstem acoustic evoked potentials (BAEP) in clinically proven brain death are already described in the literature. In most cases there were no reproducable BAEP or only wave I ipsilateral. In a few cases, shortly after the onset of brain death, wave I and a wave II ipsilateral have been detected. 40 Patients were examined during developing brain death and in brain death. Using an ipsilateral and contralateral montage (mastoid/vertex) four different patterns of BAEP in brain death could be distinguished: Wave I ipsilateral and wave II ipsilateral, reduced in amplitude and delayed in latency and a wave I-contralateral, Wave I ipsilateral and wave I-contralateral, Only wave I ipsilateral, No reproducable BAEP. In clinically not brain dead patients, three different patterns of BAEP are recorded which should be known in order to comment on the validity of the method in the diagnosis of brain death: Only wave I and a flat and late wave, only recordable using several reproductions and with a low rate of artefacts. Only wave I recordable while the patient is still breathing spontaneously (false positive results). Reversible loss of wave I. Ignoring the results, the BAEP may lead to false positive results in the diagnosis of brain death.

Brain Death↗
PubMed1985

Balloon embolization in the treatment of basilar aneurysms.

Some vertebro-basilar aneurysm may not be treatable at a reasonable risk by direct clipping. A possible alternative is transvascular obliteration, using the means of modern interventional neuroradiology in combination with neurophysiological monitoring. These possibilities and related difficulties are outlined and discussed and the example of two cases with different types of vertebrobasilar aneurysms (top of the basilar artery and basilar trunk aneurysm) which have been treated by balloon embolization.

Adult↗
PubMed1985

Transcranial Doppler sonography as a non-invasive guide for the transvascular treatment of an inoperable basilar-artery aneurysm.

This report deals with the successful treatment of a giant aneurysm located at the caudal basilar trunk in a 19-yr old boy. The aneurysm had been declared to be inoperable by several authorities in the field of neurosurgery. A series of neuroradiological interventions was performed in order to block the aneurysm with the help of a detachable balloon or, at least, to induce spontaneous thrombosis of the aneurysm sac by reducing blood flow within the caudal basilar artery. Transcranial Doppler sonography proved to be a helpful guide for therapeutic decision-making from one interventional step to the next in this adventurous field of treatment. The changing sonographic findings of the vertebrobasilar system during the course of the treatment and during the functional tests, as well as the favourable outcome, have made this case worth reporting.

Adult↗
PubMed1980

Carbon, a promising material in endoprosthetics. Part 1: the carbon materials and their mechanical properties.

Progress in endoprosthetics depends to a large extent on the availability of materials. Carbon is known for its excellent biocompatibility. Carbon materials can also be manufactured with a great variety of properties. The application of carbon materials has been restricted to some special cases like heart valves or tooth roots. Construction of high-loaded endoprosthetic joints has been impossible due to insufficient mechanical strength or manufacturable size of the materials. Three new carbon materials have been developed which seem to offer new possibilities: (1) a high strength isotropic carbon, (2) a silicon carbide/carbon composite (SiC/C) and (3) a carbon fibre reinforced carbon (CFRC). The mechanical properties of these materials were investigated including size effects (length / to thickness d ratio of samples) and manufactured parameters (final heat treatment temperature, fibre volume content and fibre orientation). Flexural strength of the first two materials, which are both isotropic, increases with decreasing l/d ratio, whereas the CFRC behaves contrarily. In the latter case, failure at low l/d ratios is caused by shear failure. The Wöhler diagram of all three materials demonstrates limits of fatigue even after only 10(3) to 10(4) cycles. The fatigue strength of the isotropic C and the SiC/C is between 70 and 80% of the static strength, even in Ringer's solution. The Young's modulus of the isotropic C is comparable to that of femoral bone. The modulus of the SiC/C is still appreciably low. It follows that both isotropic materials are applicable for sliding parts like ball and socket. Their tribological properties are described in a following paper. The CFRC finally combines high fatigue strength (approximately 400 MN/m2) with a moderate Young's modulus (approximately 150 X 10(3) MN/m2). These properties indicate application for shafts and pins.

Biomechanical Phenomena↗
PubMed1980

Carbon, a promising material in endoprosthetics. part 2: tribological properties.

In a previous three types of carbon materials were presented. A basic study of their mechanical properties showed that two of these materials might be applicable for sliding parts of artificial joints such as ball and acetabular cup of a hip joint endoprosthesis. The materials are: (1) a high strength isotropic carbon and (2) a silicon carbide/carbon composite material. The results of relevant tribological investigations are given in this paper. Experimental methods applied consisted of ring-on-disc and ball-in-socket tests. Ring-on-disc tests were performed with specific loads of 10, 20 and 30 MN/m2. In the ball-in-socket tests the gap width was 0.075 and 0.1 mm but the load was adjusted in such a way that the compression stress in the contact area was constant at 6.6 MN/m2. The latter was experimentally measured and theoretically calculated with good accordance. Ringer's solution was used as a lubricant. In ring-on-disc tests the ring was made of the SiC/C and the disc of the isotropic carbon. In ball-in-socket tests balls of SiC/C and sockets os isotropic carbon were chosen. For comparison the combination CoCrMo alloy or Al2O3 as ball, and HDPE as socket, were tested under corresponding conditions. It is shown, that the special carbon materials can withstand the extreme tribological conditions of high specific load and low sliding velocity. Neither material suffers from fatigue wear. The coefficient of friction is below 0.1 even at a specific load of 30 MN/m2. The wear rate as determined with ring-on-disc test is lower than those of all known and proposed material combinations. The data with the carbon materials combination indicate a penetration of the ball into the acetabular cup of only 1 micrometer per year.

Biocompatible Materials↗
PubMed1979

Carbon as an implant material in orthopaedic surgery.

Carbon is a material of proven value in many fields of medicine. It has only minor reactions compared with other materials, but does have unfavourable mechanical characteristics. New kinds of carbon with similar physical characteristics to other materials, e.g. steel and ceramic, have now been developed.

Animals↗
PubMed1977

[Mechanical properties of carbon as implant material in orthopedic surgery (author's transl)].

Among others material problems are come to the fore in endoprothetic with growing biochemical knowledge, also because of the realisation that in different parts of the same prothesis functionally different mechanical demands must be set. Technological progress in carbon production has lead to the development of a spectrum of different carbon specialities with various mechanical properties. In orthopaedic surgery of endoprothetic high strengh isotropic carbon, impregnated carbon and fibrereinforced carbon-carbon-composites are of particular interest, because of their physical properties and unchanged favourable chemical and biological properties of carbon. Thereby it is on one side a question of carbon material with extraordinary tribological qualities, on the other side of carbons with nearly isoelastic behaviour towards the bone, respectively with equal quotient of breaking strength and young's modulus. Therefore in future the manufacture of components with functional approbiate material using the same basic material carbon seems to be possible for the production of endoprothesis with different working parts.

Biomechanical Phenomena↗