Search PubMed⌕ Search

Biomedical subjects

T Krings

Publications and source records attributed to T Krings.

At least 37 records · Page 2Linked to original sources
PubMed2004

Functional MRI in healthy subjects during acupuncture: different effects of needle rotation in real and false acupoints.

The cerebral activation pattern due to acupuncture is not completely understood. Although the effect of acupuncture on cerebral haemodynamics has been studied, no previous report has focused on different puncture and stimulation methods. We used functional MRI (fMRI) in 15 healthy subjects to investigate cortical activation during stimulation of two real acupoints (Liv3 and G40) and one sham point, needled in a random and, for the subjects, blinded order employing rotating and non-rotating methods, using a blocked paradigm on a 1.5 tesla imager. Compared to the non-rotating stimulation method, during rotating stimulation of the real acupoints, we observed an increase in activation in both secondary somatosensory cortical areas, frontal areas, the right side of the thalamus and the left side of the cerebellum; no such effects of the needling technique were seen while stimulating the sham point. The observation that rotating the needle strengthened the effects of acupuncture only at real acupoints suggests that, as claimed in Chinese traditional medicine, stimulation of these acupoints has a specific effect on cortical neuronal activity, absent with sham acupoints. These specific cerebral activation patterns might explain the therapeutic effects of acupuncture in certain subjects.

Acupuncture Therapy↗
PubMed2004

Double spinal dural arteriovenous fistulas: case report and review of the literature.

Spinal dural arteriovenous fistula (SDAVF) is the most common spinal vascular malformation. It mainly affects men after the fifth decade and is usually an acquired lesion with an unknown etiology. We report on a patient with the unusual finding of two separate SDAVFs at the level of L1 on the right and L2 on the left side. Initial selective spinal digital subtraction angiography (DSA) was terminated with demonstration of a SDAVF at the level of L1 but incomplete demonstration of all segmental arteries. Due to a recurrent deterioration of the patient's neurological status, and persistent pathological vessels seen on MRI, a second spinal DSA was performed 6 years later, demonstrating the second fistula at the level of L2 on the left side with a separate venous drainage pattern. A retrospective analysis of the angiographic films suggested that both fistulas had already been present 6 years previously. This conclusion is justified because of a transient and faint opacification of the left L2 fistula demonstrated on the films after injection of the right L2 segmental artery. We conclude that in the case of incomplete angiography and persistent clinical and MR findings not only reopening of the treated SDAVF has to be taken into account but also the existence of a second fistula. Since this is the first case of a double fistula in our series of 129 SDAVFs, and given the few reported cases of double SDAVFs, we do not think that completion of selective spinal DSA has to be postulated routinely after a fistula has been found. However, repeat angiography should be performed in patients who continue to deteriorate, fail to improve with persisting MRI pathologies, or demonstrate delayed deterioration after a period of improvement.

Angiography, Digital Subtraction↗
PubMed2004

Haemorrhagic tracheal necrosis as a lethal complication of an aneurysm model in rabbits via endoluminal incubation with elastase.

BACKGROUND: We describe a lethal complication of an aneurysm model in rabbits for saccular aneurysmal creation via endoluminal incubation with elastase. METHOD: In 24 anaesthetized female New Zealand White rabbits, the right common carotid artery (CCA) was ligated distally to the arteriotomy. A 4F sheath was then placed retrograde into the CCA, and its origin was occluded endoluminally using a 2F Fogarty balloon. Elastase was incubated above the balloon in the separated vessel lumen for the duration of 20 minutes. Two weeks later, digital subtraction angiography was performed for aneurysm control. Two animals were then sacrificed and the aneurysm studied on histology. All animals that died within the experiment were examined post-mortem. FINDINGS: Following this protocol, an aneurysm with a mean size of 7.6 x 3.2 mm could be created in 11 out of 24 animals. 9 out of 13 animals with lethal outcome died from haemorrhagic necrosis of the trachea with subsequent pulmonary complications. DSA releaved an arterial branch originating from the proximal CCA in a near 90 degree-angle aiming at the trachea. INTERPRETATION: The endoluminal incubation with elastase is suitable for aneurysm creation of reproducible size that are suited to test new endovascular devices such as stents and new coils. One should always be aware of an arterial branch of the CCA supplying the trachea. In case of elastase instillation into this branch, lethal haemorrhagic necrosis of the trachea occurs. Bearing this complication in mind, we have experienced a minimal loss of animals in subsequent studies.

Animals↗
PubMed2004

Course of brain shift during microsurgical resection of supratentorial cerebral lesions: limits of conventional neuronavigation.

BACKGROUND: The authors have conducted a prospective study to evaluate the amount and course of brain shift during microsurgical removal of supratentorial cerebral lesions, and to assess factors which potentially influence these shifts. METHOD: In 61 patients the displacement of 2-3 cortical landmarks on the cerebral surface was dynamically quantified during surgery, i.e. during dissection of the tumour at the estimated half-time of surgery, and at the end of microsurgical removal of the cerebral lesion using the neuronavigation system EasyGuide Neuro. In 14 of these patients the displacement of a subcortical landmark was additionally analysed. Age of the patients, preoperative midline shift, location of the lesion, lesion volume, depth of the lesion below the cortical surface, presence or absence of oedema, and size of the craniotomy were analysed for potential influence on the amount of brain shift. Correlations were analysed for all patients together and for the subgroups of vault meningiomas (n=10), gliomas (n=30), and nonglial intra-axial lesions (n=21). FINDINGS: The mean displacement of the cortical landmarks ranged between 0.8 and 14.3 mm (mean: 6.1 mm, standard deviation: 3.4 mm) during surgery (10-210 minutes [mean: 50.7 minutes, standard deviation: 34.5 minutes] after dura opening) and between 2.4 and 15.2 mm (mean: 6.6 mm, standard deviation: 3.2 mm) at the end of microsurgical removal of the tumourous cerebral lesions (20-375 minutes [mean: 107.2 minutes, standard deviation: 65.6 minutes] after dura opening). Significant correlations (p<0.01) for the entire patient group were found between brain shift and tumour volume, midline shift, and size of the craniotomy, respectively. For the subgroup of vault meningiomas a significant correlation (p<0.01) between brain shift and patient age was found. For the subgroup of gliomas a significant correlation (p<0.01) between brain shift and tumour volume, midline shift and size of the craniotomy, respectively, was found. For the subgroup of nonglial intra-axial lesions a significant correlation (p<0.01) between brain shift and midline shift and between brain shift and size of the craniotomy was found. The quantity of shared common variance ranged between 10-50%. Performing a discriminant analysis, lesion volume was the only certain factor influencing brain shift intra-operatively as well as at the end of lesion removal. 58.5% of the extent of brain shift could be correctly classified by the tumour volume as the only discriminating variable during dissection of the tumour and at the end of surgery. Comparing superficial with subcortical brain shift over the same time period, a mean superficial shift of 4.6 mm (1.6-10.8 mm, standard deviation: 2.8 mm) and a mean subcortical shift of 3.5 mm (1.0-7.7 mm, standard deviation: 2.3 mm) was found. A highly significant Spearman correlation (Rho:.97, p<0.001) between superficial and subcortical brain shift emerged. Shifting of superficial landmarks exceeded shifting of subcortical structures in all patients. CONCLUSIONS: The data demonstrate the dynamics of brain shift and the limits of conventional neuronavigation and add additional support for the unavoidable inaccuracy of contemporary neuronavigational systems once the cranium is opened. Brain shift leads to a significant loss of reliability of neuronavigation systems during microsurgical removal of intracranial lesions and there are differences of the course and the amount of brain shift in relation to special subgroups of supratentorial cerebral lesions. However, because of the heterogeneous nature of lesions neurosurgeons have to remove, the modest quantity of shared common variance, and the differences between superficial and subcortical brain shift, it seems unlikely that the amount and course of brain shift become exactly predictable pre-operatively. Only an intra-operative update of image data should have the capacity to overcome this fundamental problem of modern neuronavigation.

Adolescent↗
PubMed2004

New developments in MRA: time-resolved MRA.

For many clinical questions, less invasive angiography methods have at least in part already replaced digital subtraction angiography (DSA) as a routine diagnostic procedure. However, temporal resolution achievable with DSA is still indispensable in some patients. Recent advances in MR hardware performance and imaging techniques permit sub-second frame rate MR angiographies to be performed using a rapidly repeated fast T1 weighted gradient echo sequence during administration of a contrast bolus, and subsequent complex subtraction in k-space to emphasise the difference in phase between stationary tissue and contrast-enhanced blood. This technique allows two-dimensional projection angiograms to be obtained at a temporal frame rate of three images per second and with a spatial in-plane resolution of about one square millimetre. This time-resolved information is important for (a) the detection and follow-up of arteriovenous malformations, including their arterial feeders, the size of the nidus and their venous drainage patterns, (b) the demonstration of dural arteriovenous fistulas, recognised as an early filling of a dural sinus during the early arterial phase, and (c) the characterization of the vascularisation of brain tumours. With regards to vascular malformations, the direction of venous drainage and therefore the most pressing clinical questions concerning the need for therapeutic intervention can be ascertained. This technique is the only MR imaging method able to provide dynamic information on the cerebral vasculature. It therefore constitutes a helpful adjunct to the imaging armentarium in many clinical situations.

Angiography, Digital Subtraction↗
PubMed2004

Playing piano in the mind--an fMRI study on music imagery and performance in pianists.

Reading of musical notes and playing piano is a very complex motor task which requires years of practice. In addition to motor skills, rapid and effective visuomotor transformation as well as processing of the different components of music like pitch, rhythm and musical texture are involved. The aim of the present study was the investigation of the cortical network which mediates music performance compared to music imagery in 12 music academy students playing the right hand part of a Bartok piece using functional magnetic resonance imaging (fMRI). In both conditions, fMRI activations of a bilateral frontoparietal network comprising the premotor areas, the precuneus and the medial part of Brodmann Area 40 were found. During music performance but not during imagery the contralateral primary motor cortex and posterior parietal cortex (PPC) bilaterally was active. This reflects the role of primary motor cortex for motor execution but not imagery and the higher visuomotor integration requirements during music performance compared to simulation. The notion that the same areas are involved in visuomotor transformation/motor planning and music processing emphasizes the multimodal properties of cortical areas involved in music and motor imagery in musicians.

Adult↗
PubMed2004

Functional and diffusion-weighted magnetic resonance imaging for visualization of the postthalamic visual fiber tracts and the visual cortex.

Diffusion-weighted magnetic resonance imaging (MRI) offers the possibility to study the course of the cerebral white matter tracts whereas functional MRI (fMRI) provides information about the specific functions of cortical areas. We evaluated the combination of fMRI and diffusion-weighted MRI to detect cortical visual areas with their corresponding visual fiber tracts in 15 healthy controls (age: 23 - 53 years, male : female = 8 : 7). We demonstrated activation within the primary visual cortex and white matter bundles connecting the lateral geniculate body and the striate cortex in all subjects investigated. Additional activation could be appreciated in some subjects within the lateral geniculate bodies (n = 2) and the motion-sensitive area V5 (n = 3). The combination of diffusion-weighted and functional imaging allows visualization of the origin, direction and functionality of large white matter tracts. This will prove helpful for imaging structural connectivity within the brain during functional imaging. Moreover, this technique might provide important information for neurosurgical patients presenting with space-occupying lesions close to the cortical and subcortical visual system since this technique can -- in contrast to diffusion tensor imaging -- easily be adopted into a neuronavigation system and can be performed on all MR scanners capable of diffusion-weighted imaging without specific post-processing programs.

Adult↗
PubMed2003

Lumbar nerve root avulsion following trauma: balanced fast field-echo MRI.

Lumbosacral nerve root avulsion uncommonly complicates major trauma. Most patients also have pelvic or lumbar fractures. We present a patient who had a high-velocity vehicle accident with traumatic hip dislocation without fractures of the spine or pelvis. MRI demonstrated lumbosacral traumatic pseudomeningoceles. We used balanced fast field echo and MR myelography to make the diagnosis and show the extent of the pseudomeningocele.

Adult↗
PubMed2003

MRI and intraoperative findings in cavernous haemangiomas of the spinal cord.

More sensitive imaging techniques, such as MRI, have led to an increase in the number of reported cases of spinal cord cavernous haemangioma (SCCH). Complete surgical resection has been performed with good outcomes. However, operative findings do not always confirm preoperative MRI as to the size and site (superficial or deep) of the lesion. We evaluated whether MRI can be used to predict whether or not SCCH reach the surface of the spinal cord, since this has an impact on surgical strategy. We reviewed the preoperative MRI, case-notes and video recordings of 12 patients who underwent surgery, at which five superficial and seven deep-seated lesions were identified. T1-weighted images correctly indicated the site of the lesion in ten, T2-weighted images in only eight. One deep lesion was thought to be superficial on both T1- and T2-weighted images. Intravenous contrast medium was not helpful in diagnosis or localisation. In no case was a surgically proven superficial lesion interpreted as deep in the spinal cord.

Adult↗
PubMed2003

Endovascular treatment of experimentally induced aneurysms in rabbits using stents: a feasibility study.

Although Guglielmi detachable coil (GDC) systems have been generally accepted for treatment of intracranial aneurysms, primary stenting of aneurysms using porous stents or implantation of coils after stent placement remains experimental. Testing of these new methods requires an animal model which imitates human aneurysms in size, configuration and neck morphology. We assessed in detail the technical requirements of and steps for transfemoral stent treatment of experimentally induced aneurysms at the top of the brachiocephalic trunk in rabbits. We created aneurysms in ten rabbits by distal ligation and intraluminal digestion of the right common carotid artery with elastase. We treated five animals with porous stents alone, and five with stents plus coiling via the meshes of the stent, which permitted dense packing of coils. No complications related to the procedures occurred. In all animals, even in those treated solely with porous stents, total occlusion of the aneurysm was achieved. Our animal model can be suitable for testing the biocompatibility and occlusion rate of new methods and devices for the treatment of experimental aneurysms.

Aneurysm↗
PubMed2003

[Cerebral contrast medium extravasation after coronary angioplasty].

We report on an 82-year-old woman who suffered a sudden loss of consciousness, right-sided hemiparesis, and aphasia during a coronary angiographic procedure. Computed tomography (CT) of the brain performed immediately revealed an edema and extravascularly localized contrast media in the left hemisphere. Within 6 h, neurological symptoms had disappeared, and a second CT after 48 h revealed normal results. Usually, extravasation of contrast media affects the posterior circulation with cortical blindness. This case demonstrates that contrast media may affect the blood-brain barrier also outside the posterior circulation. If neurological symptoms occur during angiography, contrast media extravasation must be distinguished from embolism or vasospasm induced by the angiographic procedure.

Aged↗
PubMed2003

[Diffusion Weighted Imaging Combined with Intraoperative 3D-Ultrasound and fMRI for the Resection of an Optic Radiation Cavernoma].

A 17-year-old patient with a symptomatic cavernoma of the optic radiation underwent surgery supported by functional magnetic resonance imaging (fMRI), diffusion weighted magnetic resonance imaging (DWI) and navigated 3D-ultrasound. The primary visual cortex was visualized with fMRI. The optic radiation was delineated by means of DWI. The diffusion weigthed images were used for 3-dimensional reconstruction of the optic radiation. During surgery, the information of the localisation of functional brain regions were used together with the 3D-ultrasound, enabling the surgeon to remove the cavernoma without morbidity. This is the first report of the combined use of fMRI, fiber tract imaging and 3D-ultrasound for the safe resection of an optic radiation lesion.

Adolescent↗
PubMed2003

Hypertrophic olivary degeneration following pontine haemorrhage: hypertensive crisis or cavernous haemangioma bleeding?

The clinical and magnetic resonance (MR) features of hypertrophic olivary degeneration are described, along with a rare but treatable cause of this entity-pontine cavernous haemangioma. Hypertrophic olivary degeneration occurs after focal lesions to the dentato-rubro-olivary pathway, typically following a pontine haemorrhage involving the ipsilateral central tegmental tract, the contralateral superior cerebellar peduncle, or the dentate nucleus. Clinically, there is palatal myoclonus and an uncontrollable tremor, presumably caused by loss of inhibitory control. On MR imaging, hypertrophic olivary degeneration is characterised by a non-enhancing T1 isointense, T2 hyperintense enlargement confined to the olivary nucleus. Typically, haemorrhages following a hypertensive crisis are responsible for hypertrophic olivary degeneration. However, in the three reported cases, imaging findings within the former bleeding cavity suggested a cavernous haemangioma as the source of the haemorrhage.

Cerebral Hemorrhage↗
PubMed2003

Focused high frequency repetitive transcranial magnetic stimulation for localisation of the unexposed primary motor cortex during brain tumour surgery.

OBJECTIVES: To investigate if intraoperative focused high frequency repetitive transcranial magnetic stimulation (rTMS) can localise the primary motor cortex without exposure of the cortical surface. METHODS: A high frequency train (357 Hz) of four suprathreshold magnetic stimuli was delivered transcranially to the region of the rolandic area during brain tumour operations in 12 patients. To induce a focal magnetoelectric field, the flat figure of eight coil (outer diameter of each loop 7 cm) was used. Motor evoked potentials (MEP) were recorded in eight muscles of the upper and lower contralateral extremities. The first stimulation site was 2.5 cm behind the bregma, the second site 2 cm, and the third site 4 cm dorsal to the first stimulation site. If no MEP were obtainable, stimulation was repeated in anteroposterior direction at more laterally located sites. Using neuronavigation, each positive stimulation site was correlated with the underlying cortical anatomy. RESULTS: Stimulation was performed at a total of 42 sites (in two patients, maximum stimulation at the three initial sites failed to evoke a motor response). In four patients, MEP were obtained only from one stimulation site. This site exactly overlayed the primary motor cortex. In eight patients, MEP could be elicited from more than one stimulation site. In seven of the eight patients, the site from which MEP with peak amplitudes were elicited, corresponded to the primary motor cortex. In total, the primary motor cortex was correctly identified on the basis of electrophysiological findings in 11 of 12 patients (92 %). In two patients, only the more lateral stimulation sites permitted MEP recording. CONCLUSION: Intraoperative focused rTMS is highly sensitive for localisation of the primary motor cortex. Focused rTMS as a localising instrument alleviates the need of motor cortex exposure and, thereby, can contribute to minimise the surgical approach to brain tumours in the rolandic area.

Adult↗
PubMed2002

Endovascular treatment of experimental aneurysms in rabbits using Guglielmi detachable coils -- a feasibility study.

The Guglielmi detachable coil (GDC) has been generally accepted for treatment of intracranial aneurysms. Preclinical testing of new coil developments requires animal models of aneurysms which imitate human aneurysms in size, configuration and neck morphology. We assessed in detail the technical requirements and steps for transfemoral treatment of experimentally induced aneurysms at the top of the brachiocephalic trunk (TBC) in rabbits. We created aneurysms in five rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. All animals were treated successfully 2-3 weeks after induction of the aneurysm, with dense packing of the coils. No complications related to the procedures occurred. The study demonstrates that our animal model can be a suitable method for testing the biocompatibility and occlusion rate of new embolic materials.

Aneurysm↗