Biomedical subjects

H Henkes

Publications and source records attributed to H Henkes.

At least 37 records · Page 2Linked to original sources

PubMed2000

[Diagnostic imaging in viral encephalitis].

The diagnostic procedure in viral encephalitis is based on the synopsis of clinical signs and symptoms, serological data, CSF analysis and diagnostic imaging findings. This article summarizes the findings of those viral encephalitides most frequently encountered in Western Europe. MRI is more sensitive than CT for the detection of inflammatory brain lesions due to the higher contrast resolution. The pattern of parenchymal damage is highly specific in only some viral encephalitides (e.g., the frequently hemorrhagic lesions of structures of the limbic system in herpes simplex virus type I encephalitis; the symmetric and confluent lesions of the frontal white matter of progressive diffuse leukoencephalopathy in AIDS). In the majority of viral encephalitides MRI demonstrates the location and extension of parenchymal damage. The specific diagnosis in terms of the causative agent is based on serological studies.

Brain↗

PubMed2000

[Septic-embolic and septic metastatic brain abscess].

The hematogenous spread of bacteria, fungi and protozoa may also reach the brain vessels, which happens mostly through septic emboli. From such an embolus a metastatic focal encephalitis and later a septic-embolic brain abscess may arise. The most frequently underlying infections that may cause septic emboli are bacterial endocarditis as well as bacterial infections of artificial heart valve prostheses. Congenital heart malformations with a right-to-left shunt also play here a certain role. Basically, however, all septic conditions and bacteriemias may cause septic-embolic brain abscesses. They occur frequently as multiple lesions. MRI is superior to CT in depicting the different stages of evolution from focal encephalitis, through the hardly encapsulated early abscess, to the formation of a membrane and later a dense fibrous capsule. The medical treatment of a brain abscess requires properly performed CT or MRI follow-up examinations in order to realize early enough a possible growing of such a lesion.

Brain↗

PubMed2000

[Clinical aspects and diagnostic imaging in sarcoidosis of the nervous system].

The central nervous system is frequently affected during the course of sarcoidosis. Many of these lesions remain without clinical correlates. Unenhanced and contrast enhanced CT and MRI play an important role during the diagnostic work-up of patients with sarcoidosis and suspected or proved CNS involvement. This article summarizes the most frequent manifestations of neurosarcoidosis and provides illustrative examples of MRI findings.

Brain↗

PubMed2000

Combined endovascular-microsurgical treatment of tentorial-incisural dural arteriovenous malformations. Report of five cases.

Dural arteriovenous malformations of the tentorial edge are rare lesions with an unfavorable clinical course if left untreated. As yet no optimum treatment has been established. We retrospectively evaluated the results of our therapy concept, which consists of endovascular embolization followed by microsurgical obliteration, and compared the results to the relevant literature in order to clarify which therapeutic regimen seems to be optimum at the present time. In all of our five patients the lesion was completely obliterated, as proven by angiography, with favorable clinical results and low morbidity. Several other clinical series confirm our results, so we conclude that combined endovascular therapy and microsurgery is the optimum treatment for these lesions.

Aged↗

PubMed2000

Torquability of microcatheter guidewires: the resulting torsional moment.

Guidewires for microcatheters used for the subselective catheterization of small vessels must meet high quality requirements in regard to handling, steerability, radiopacity and physical properties. The aim of this paper is to classify one of the factors that determine the physical and mechanical parameters of a number of existing microcatheter guidewires. A torsion-testing equipment for guidewires was devised. Nitinol wires were tested and compared with the austenitic stainless steel variants. 13 different commercial wires were tested. Tensile strength, shear modulus and wire diameter are the determining factors of the torsional rigidity of guidewires. By interpreting the measured torsional momentums various statements concerning the torsional rigidity of different wires can be made. The properties of guidewires are characteristic features of a system and friction and flexible strength examinations have to be carried out to design new variants of wires to meet the requirements of interventional physicians.

Algorithms↗

PubMed2000

Intracranial vertebrobasilar stenosis: angioplasty and follow-up.

BACKGROUND AND PURPOSE: When medication fails to improve symptoms of atherosclerotic stenosis of the intracranial vertebral and basilar arteries, percutaneous transluminal angioplasty (PTA) is considered. However, because investigators disagree on the usefulness of this procedure, we conducted a retrospective study to evaluate the indications, efficacy, and safety of PTA. METHODS: Twenty patients underwent PTA of the vertebral (n = 14) or basilar (n = 6) artery, 18 for neurologic signs and symptoms of arterial stenosis that recurred or progressed despite pharmacotherapy and two prophylactically. Neurologic examinations were performed before and after the procedure and arterial patency was evaluated at follow-up by digital subtraction angiography and/or MR angiography. Imaging follow-up was available for 14 (70%) of the 20 patients, neurologic follow-up for 15 (75%). RESULTS: The stenosis was successfully dilated in all patients, and on follow-up neuroradiologic examinations, vessel patency could be seen in 12 (86%) of 14 patients. Only one (7%) of 15 patients who returned for a follow-up neurologic examination had new symptoms (caused by occlusion of the vertebral artery 4 months after the procedure). One patient had a reversible neurologic deficit and one had hemiparesis after PTA. No patient died as a result of PTA. CONCLUSION: In our study, PTA of intracranial vertebrobasilar arteries was associated with a low mortality and morbidity rate and with a high degree of patency. This technique may therefore be regarded as an effective means of improving the patency of stenotic arteries. In selective cases, it might be considered for use prophylactically.

Aged↗

PubMed1999

[Pseudoaneurysm of the extracranial internal carotid artery. Treatment by stent and coil implantation].

Pseudoaneurysms of the extracranial internal carotid artery (ICA) can be caused by external injury or may be due to spontaneous dissection. Pseudoaneurysms bear an increased risk of arterio-arterial embolism. Treatment of pseudoaneurysms is influenced by the location and the type of injury, associated injuries, collaterals to the ipsilateral hemisphere, neurological signs and symptoms, growth of the lesion and patient age. Potential treatment regimen include conservative and medical approaches with anticoagulation and antiplatelet therapy, extra-intracranial bypass, resection of the pseudoaneurysm with vessel reconstruction, ligation or endovascular balloon occlusion of the ICA. Pseudoaneurysms of the ICA adjacent to the skull base require a major surgical procedure. If there are contra-indications for vessel occlusion conservative or medical treatment used to be the only therapeutic alternatives. We report the treatment of two patients with extracranial ICA pseudoaneurysms after blunt injury with stent placement (in one case combined with coil embolization) as a further treatment option.

Adult↗

PubMed1999

Accuracy of intravascular microcatheter pressure measurements: an experimental study.

Intravascular pressure measurements are considered useful for the monitoring and assessment of endovascular treatment effects in intracranial vascular malformations. Experimental data on the accuracy of these measurements are limited. A flow phantom with defined intraluminal pressures and pulsatility flow waveforms was used in this study. Microcatheters commercially available for neuroendovascular procedures (length 140-155 cm), with different outer (0.5-0.83 mm) and inner (0.3-0.53 mm) diameters, were introduced into the phantom in the direction of flow. In a static experiment, pressure values from 0 to 75 mmHg were applied, and in the dynamic part of the experiment mean pressure values from 25 to 65 mmHg, with a pulsatile amplitude from 70 to 170 mmHg were employed. In the static experiment, there was a linear relationship between the pressure values obtained through the microcatheters and the local transducer of the flow phantom. The pulsatile experiments showed increased damping of the pressure waveforms with decreasing inner diameter of the microcatheters. However, the mean pressure values remained accurate. This experimental study has shown that mean pressure values can be accurately measured through microcatheters from 0.3-0.5 mm inner diameter and more than 140 cm in length. In vivo pressure measurements during interventional procedures are therefore reproducible and can be used for monitoring of embolization effects in patients.

Blood Flow Velocity↗

PubMed1998

Percutaneous transluminal angioplasty of intracranial artery stenosis: clinical results in 24 patients.

Circumscribed stenotic lesions of the intracranial arteries can cause cerebral ischemia by hemodynamic and/or thromboembolic mechanisms. Anticoagulation therapy, antiplatelet therapy, and bypass surgery are treatment strategies that have no direct impact on the underlying lesion. This study summarizes the experience of a single institution at which percutaneous transluminal angioplasty (PTA) of intracranial atherosclerotic stenoses was performed. The authors performed a retrospective analysis of 24 consecutive patients. Their medical histories (cardiovascular risk factors, current clinical signs and symptoms and their duration, previous stroke[s], and medical treatment) were evaluated together with findings from previous imaging studies. The site and degree of the stenoses to be treated (target lesion) were identified with the use of ultrasound and angiography studies. Additional vascular stenoses were noted. Percutaneous transluminal angioplasty was performed using single-lumen balloon microcatheters with appropriate diameters. The results of PTA were correlated with angiographic and ultrasound findings and the clinical outcome. Significant cardiovascular risk factors and clinical signs and symptoms related to the target lesion that persisted despite medical treatment were identified in all patients except one. The duration of symptoms varied from several days to 8 months. Previous stroke had occurred in four patients. The degree of stenosis was classified as "high grade" in 10 patients and as "subtotal" in 14. The target lesion (stenosis) was located in the anterior circulation in eight patients (four in the internal carotid and four in the middle cerebral arteries). Stenoses of posterior circulation vessels were treated in 16 patients (nine vertebral, six basilar, and one posterior cerebral arteries). Recanalization was rated "complete" in 15 patients and sufficient in six patients. In three patients residual stenosis remained. Complications were encountered in seven patients: two asymptomatic dissections, one transient vessel occlusion, one vessel occlusion with subsequent stroke, and three ischemic lesions likely due to thromboembolism, two of which caused only transient neurological symptoms. Percutaneous balloon dilation proved effective in the treatment of intracranial atherosclerotic stenosis. There are, however, potential complications and experience with this procedure is only limited. Long-term results need to be determined. The authors conclude from their preliminary results that PTA may be an alternative to bypass surgery and conservative management and may be considered for patients in whom ischemic neurological symptoms persist despite medical treatment.

Journal Article↗

PubMed1998

[Clinical application of transcranial color-coded duplex ultrasound for detection of intracranial aneurysms].

We investigated 88 Patients with a total of 102 angiographically diagnosed intracranial aneurysms by means of transcranial colour coded Duplex sonography (TCCD) during a time period of 15 months. Both the size and the localization of the aneurysms were determined. Seventy aneurysms (77%) with a diameter of 16 +/- 8 mm (6-55 mm) were detectable, with excellent visualization in 36 (42%), moderate visualization in 34 (40%), and no sufficient visualization in 16 (16%) aneurysms, respectively. In another 16 cases (16%) there was no sufficient vone window. Thrombotic material inside the aneurysm was detectable in 16/20 cases (75%), visualization of coil embolized aneurysms in 12/25 patients (48%). TCCD allows the follow up of cerebral aneurysms, with the detection of thrombosis and treatment effects after embolization. The method is not valid for the detection of intracranial aneurysms.

Adolescent↗

PubMed1998

Toxic spongiform leucoencephalopathy after inhaling heroin vapour.

This is a report of clinical, CT and MRI findings in a patient with toxic spongiform leucoencephalopathy after heroin ingestion. The disease is observed in drug addicts who inhale pre-heated heroin. The clinical onset, which usually occurs some days or even longer after the last heroin consumption, is characterized by a cerebellar syndrome. The cerebellar hemispheres, the cerebellar and cerebral peduncles and the pyramidal tract may be affected. Spongiform demyelination is the morphological substrate of the lesions, which are not contrast enhancing, hypodense on CT and hyperintense on T2-weighted MRI. The frequently perfect symmetry of the affection of functional systems points to a toxic and/or metabolic pathophysiological mechanism.

Administration, Inhalation↗

PubMed1998

Endovascular therapy of brain AVMs prior to radiosurgery.

The purposes of this study were to determine the safety and efficacy of embolization of brain AVMs prior to radiosurgery and to evaluate the total obliteration rate achieved. The brain AVMs of 64 patients were subselectively embolized mainly with NBCA, platinum microcoils and/or PVA. The aim of embolization was the reduction of the target volume and/or the elimination of vascular structures bearing an increased risk of hemorrhage. Presenting symptoms were intracranial hemorrhage in 33 patients, a seizure disorder in 21 patients, and headache in 6 patients. Four AVMs had been detected as an incidental finding. The initial AVM volume was in the range of 0.5 to 84 cc (mean 17 cc). Grading of the AVMs according to the Spetzler-Martin scale showed the following distribution: grade I, 3x; II, 13x; III, 11x; IV, 17x; V, 4x; VI, 16x. A total of 300 endovascular procedures including 47 subselective catheterizations without and 253 with embolization were performed. A size reduction of the AVMs between 10% and 95% (mean 63%, median 70%) was achieved. Neurological symptoms due to treatment complications were transient in 12 patients, of minor clinical significance but permanent in 4 patients. Following radiosurgery, one patient died due to recurrent intracerebral hemorrhage. Three patients are doing well but refused final follow-up angiography. A total of 30 patients is currently within the latency interval after radiosurgery. Radiosurgery failed to obliterate the embolized AVMs in 16 patients. Angiography confirmed complete nidus obliteration in 14 patients. The endovascular treatment of brain AVMs prior to radiosurgery proved safe and effective and may be considered in either high grade or incidental AVMs. AVM obliteration after embolization and radiosurgery is less frequently achieved than after stereotactic irradiation of primarily small AVMs.

Adolescent↗

PubMed1998

Detection of microemboli distal to cerebral aneurysms before and after therapeutic embolization.

PURPOSE: Recently developed interventional radiologic techniques, such as embolization with platinum coils, may induce thrombus formation within an aneurysm. The aim of the present study was to investigate the frequency of microemboli distal to untreated and treated cerebral aneurysms. METHODS: Among a total of 110 patients treated with platinum coil embolization, 35 patients (27 women and eight men, aged 50+/-10 years) who were at high risk of ischemic complications underwent emboli detection with a transcranial Doppler sonographic monitoring system. All patients were studied before and after coil embolization. The aneurysms were located at the internal carotid artery (n=14), the basilar artery (n=10), the middle cerebral artery (n=7), or the vertebral artery (n=4). Twenty-nine (85%) of 35 patients were monitored within 6 hours of the completion of treatment. RESULTS: Microemboli distal to the aneurysm were not detected in any of the patients before treatment. Microemboli were detected in 11 patients (31%) after embolization (mean, 16+/-21 per hour; range, 1-74 per hour). Microemboli were detected in five (71%) of seven patients in whom ischemic complications occurred after treatment, but in only six (21%) of 28 asymptomatic patients. This difference was statistically significant. The rate of occurrence of emboli in patients with ischemic complications (23+/-30 emboli per hour) was higher than in asymptomatic patients (10+/-7 emboli per hour), but this difference was not statistically significant. CONCLUSION: Microemboli were detected significantly more often in patients who suffered from cerebral ischemia after coil embolization of an intracranial aneurysm. This observation supports the definition of a high-risk group of patients with incomplete embolization or with a large-diameter, broad-neck aneurysm. The early detection of microemboli after treatment may be an indicator for excessive intraaneurysmal thrombus formation and could influence the decision for prophylactic treatment with heparin or aspirin.

Aneurysm↗

PubMed1996

Regional association of developmental venous anomalies with angiographically occult vascular malformations.

This study reviews the neuroradiological findings of 43 patients with a developmental venous anomaly in order to discuss the clinical significance of this entity. All patients underwent unenhanced and contrast-enhanced computer tomography and magnetic resonance tomography, as well as selective angiography, and were followed for at least 2 years. In 40% (17 of 43) of patients a cryptic vascular malformation was found in the proximity to the developmental venous anomaly. Neurological symptoms were present in 8 of 17 patients (47%) in this group. Patients with an isolated developmental venous anomaly had symptoms in 19% (5 of 26), but none of them had experienced a hemorrhage. Magnetic resonance was the most sensitive method for the diagnosis of both types of lesions and alterations of the adjacent parenchyma. These results further support that developmental venous anomalies represent a clinically benign entity. However, patients with an association of a developmental venous anomaly and a cryptic vascular malformation are at risk for hemorrhage from their angiographically occult vascular malformation. Magnetic resonance proved to be the imaging modality of choice for both entities and is appropriate for diagnosis and follow-up.

Adolescent↗

PubMed1996

Visualisation of intracranial aneurysms by transcranial duplex sonography.

We examined 72 patients with 89 angiographically confirmed intracranial aneurysms, using transcranial colour-coded duplex sonography (TCCD) to determine the location and size of the aneurysm. The patients were admitted for coil embolisation of their aneurysm following subarachnoid haemorrhage or because of a cranial nerve palsy. Using a 2/2.25 MHz transducer, 42 aneurysms (47%) were seen satisfactorily through the temporal bone window or foramen magnum. In 24 cases (27%) image quality was insufficient as a result of a poor bone window, of the aneurysm having a diameter of less than 6 mm or of its being in an unfavorable location. In 23 other cases (26%) it was not possible to detect the aneurysm. Thrombosed structures could be demonstrated using TCCD in 8 of 12 giant intracavernous or basilar artery aneurysms, and in 15 of 19 aneurysms treated by platinum coil embolisation. TCCD offers a noninvasive method for monitoring progressive intra-aneurysmal thrombosis following coil embolisation and for follow-up of patients with untreatable fusiform aneurysms, should this be required. Detection of small aneurysms is limited by spatial resolution and insonation angles.

Aneurysm, Ruptured↗

PubMed1996

Sumatriptan: vasoactive effect on human dural vessels, demonstrated by subselective angiography.

Sumatriptan, a selective 5-hydroxytryptamine (5HT1D)-receptor agonist, has recently been introduced in the pharmacotherapy of acute migrane attacks. The potential vasoactive effect of sumatriptan on human dural vessels in vivo, however, is still a matter of controversy. We investigated the effects of sumatriptan on dural vessels after subcutaneous or intra-arterial injection. During interventional angiography, the middle meningeal artery (MMA) of nine patients was catheterized with a microcatheter using the transfemoral route. Three MMA were entirely normal, two supplied a dural arteriovenous fistula (AVF) and four were transdural feeders to a brain arteriovenous malformation (AVM). Sumatriptan was injected either into the subcutaneous tissue of the right shoulder (6 mg, two patients) or into the catheterized MMA (2 mg, six patients). The substance caused a marked vasoconstriction of the three normal MMA, visible angiographically and confirmed by intravascular Doppler ultrasonography. Vasoconstriction was still present in the last angiogram obtained 15 min post-injection. Slightly hypertrophied feeders to dural AVF and to brain AVM showed some vasoconstriction in one and four patients, respectively. In two patients with markedly hypertrophied dural feeders to a dural AVF and to a brain AVM, respectively, rapid shunting probably prevented obvious vasoactive effects of sumatriptan. The data obtained by angiography and intravascular Doppler ultrasonography provide strong evidence that sumatriptan has a vasoconstrictive effect on normal as well as hypertrophied dural vessels.

Adult↗

PubMed1996

Endovascular laser detachment of platinum alloy microcoils: principle and initial experimental experience.

The aim of the investigation was the technical realization and approval of a new method for insertion and detachment of platinum alloy microcoils and other vascular implants via standard microcatheters. Flexible lightconducting fibers, 105 microns in diameter were connected to platinum alloy microcoils. It was examined whether an insertion wire, a lightconducting fiber and a platinum alloy microcoil could be advanced through a Tracker-18 (Target) microcatheter. The detachment of the attached coil from the lightconducting fiber was investigated. Platinum alloy microcoils can be attached to available lightconducting fibers in a reliable and reproduceable manner. Together with the fiber they can be advanced via a Tracker-18 microcatheter. Only extremely tortuous vessels may increase the friction to critical values. A Ho-YAG laser source was used. This allowed the instantaneous detachment of microcoils from laser fibers. In contrast to electrolytical detachment, no foreign substances are released to the blood stream. The detachment does not require waiting time and does not activate thrombus formation. Due to specific technical features, injuries of the vessel wall are avoided. After further miniaturization and adaption of the lightconducting fibers to the required characteristics, laster detachment may have the potential to replace current methods such as electrolytical and mechanical coil detachment.

Lasers↗

PubMed1995

Transcranial color-coded duplex sonography in cerebral arteriovenous malformations.

BACKGROUND AND PURPOSE: It is well known that significant changes in cerebral hemodynamics may occur during the treatment of cerebral arteriovenous malformations with the complication of intracerebral hemorrhage and parenchymal edema. We used transcranial color-coded duplex sonography to study alterations in blood flow velocities during staged embolization. METHODS: Forty-one patients aged 40 +/- 13 years (mean +/- SD) with angiographically proven cerebral arteriovenous malformations were studied. The blood flow velocities of the anterior, middle, and posterior cerebral arteries were measured in 16 patients with supratentorial arteriovenous malformations, both before the first and then after each successive embolization (three to seven treatments). RESULTS: In 29 of 41 patients (71%), transcranial color-coded duplex sonography satisfactorily revealed the malformations and their main feeders. After the final embolization, we found a reduction in the peak flow velocity in treated feeders of 23 +/- 28% compared with the values before the first embolization. The untreated feeders showed an increase in peak flow velocities of 12 +/- 23% as an expression of increased collateral flow. After the treatment of the supplying feeders, we observed a reduction in flow velocity of 25 +/- 13% in seven patients, with cross-filling of the arteriovenous malformation through the contralateral anterior cerebral artery and the anterior communicating artery. CONCLUSIONS: The technical advantage of transcranial color-coded duplex sonography compared with transcranial Doppler sonography is that it allows the exact identification of different feeding arteries in arteriovenous malformations. Repeated measurements during stepwise embolization with corrected insonation angle are easily achieved, and noninvasive quantification of hemodynamic changes is possible. The method may be helpful in the planning of the different steps of embolization.

Adult↗