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Biomedical subjects

Timo Krings

Publications and source records attributed to Timo Krings.

At least 19 recordsLinked to original sources
PubMed2006

A report of two cases with dolichosegmental intracranial arteries as a new feature of PHACES syndrome.

BACKGROUND: We describe two previously unreported cases with complete or incomplete expression of PHACES syndrome, a rare congenital syndromal pediatric disorder, which is characterized by posterior cranial fossa malformations, large facial hemangiomas, arterial anomalies, coarctation of the aorta and cardiac defects, abnormalities of the eye, sternal and supraabdominal raphe defects. CASE REPORTS: These two children exhibited a feature not reviewed extensively in the literature, namely, segmental elongation and dilatation of intracranial arteries associated with intracranial occlusive arterial disease, predominantly on the anterior division of the internal carotid artery (ICA) and on the P2 segment of the posterior cerebral artery. This dolichoectasia was found at the distal cervical internal carotid artery, the intradural segment of the ICA before the division, the trigeminal artery, and the posterior division of the ICA. We presume that the different forms of arterial involvement in PHACES syndrome (arterial stenoses, segmental agenesis of vessels, and the dolichoectasia described in this study) constitute a spectrum of angiogenetic dysfunctions related to an embryonic event involving several cephalic neural crest segments of the dorsal aorta.

Brain↗
PubMed2006

Pathogenesis, diagnosis and management of pneumorrhachis.

Pneumorrhachis (PR), the presence of intraspinal air, is an exceptional but eminent radiographic finding, accompanied by different aetiologies and possible pathways of air entry into the spinal canal. By reviewing the literature and analysing a personal case of traumatic cervical PR after head injury, we present current data regarding the pathoanatomy, clinical and radiological presentation, diagnosis and differential diagnosis and treatment modalities of patients with PR and associated pathologies to highlight this uncommon phenomenon and outline aetiology-based guidelines for the practical management of PR. Air within the spinal canal can be divided into primary and secondary PR, descriptively classified into extra- or intradural PR and aetiologically subsumed into iatrogenic, traumatic and nontraumatic PR. Intraspinal air is usually found isolated not only in the cervical, thoracic and, less frequently, the lumbosacral regions but can also be located in the entire spinal canal. PR is almost exceptional associated with further air distributions in the body. The pathogenesis and aetiologies of PR are multifold and can be a diagnostic challenge. The diagnostic procedure should include spinal CT, the imaging tool of choice. PR has to be differentiated from free intraspinal gas collections and the coexistence of air and gas within the spinal canal has to be considered differential diagnostically. PR usually represents an asymptomatic epiphenomenon but can also be symptomatic by itself as well as by its underlying pathology. The latter, although often severe, might be concealed and has to be examined carefully to enable adequate patient treatment. The management of PR has to be individualized and frequently requires a multidisciplinary regime.

Craniocerebral Trauma↗
PubMed2006

The hyperdense posterior cerebral artery sign: a computed tomography marker of acute ischemia in the posterior cerebral artery territory.

BACKGROUND AND PURPOSE: In the anterior circulation, the hyperdense middle cerebral artery (MCA) sign is a well-established marker for early ischemia. Similarly, the hyperdense basilar artery sign or the MCA "dot" sign may be a diagnostic clue for basilar artery or distal MCA branch thrombosis. The purpose of this study was to define the hyperdense posterior cerebral artery (PCA) sign and determine its incidence, diagnostic value, and reliability as a marker for ischemia in the territory of the PCA. METHODS: Cranial computed tomographies (CCTs) of 48 patients with proven acute ischemia (<12 hours) in the PCA territory were compared by 3 independent and blinded readers to the CCTs of 86 age-matched patients without PCA infarction. Using follow-up imaging, the correlation of the hyperdense PCA (HPCA) with infarct size, thalamic infarction, and bleeding were investigated. RESULTS: An HPCA was found in 35.4% of all patients with PCA infarction, typically within the ambient cistern, with a specificity of 95.4%. The thalamus was affected significantly more often (P=0.009) and the size of the infarct was significantly more often large than medium (P=0.018) or small (P<0.001) when an HPCA was present. Hemorrhagic transformation tended to occur more often when the HPCA was present. CONCLUSIONS: An HPCA was detected in more than one third of all patients with PCA ischemia, suiting the incidence of the hyperdense MCA. Based on our results, this sign may not only be helpful in the early diagnosis of PCA infarction but might also act as a prognostic marker in acute PCA territory ischemic stroke.

Adult↗
PubMed2006

Long-term histological and scanning electron microscopy results of endovascular and operative treatments of experimentally induced aneurysms in the rabbit.

OBJECTIVE: Treatment strategies of cerebral aneurysms include surgical clipping and endovascular therapies. To determine the long-term results of these therapeutic strategies, the vessel wall reaction close to the former aneurysm was studied according to the assumption that an intact endothelial layer over the former aneurysm neck constitutes complete vessel wall reconstruction and stable aneurysm obliteration. METHODS: Aneurysms were created in 40 rabbits by intraluminal elastase incubation of the common carotid artery. Five animals each were assigned to the following groups: untreated, porous stents, polyurethane covered stentgrafts, porous stents with subsequent coiling. Ten animals were treated with coils alone, 10 with clips. After 6 months, angiography, histology, and scanning electron microscopy was performed. RESULTS: Porous stents did not obliterate the aneurysm, whereas stentgrafts did; in-stent stenosis of up to 60% was present because of neointimal multilayer proliferation. After coiling, the aneurysm dome was occluded with fibrinous and collagenous material, whereas the aneurysm neck was not covered by an endothelial lining. Coil loops lay bare within the vessel, with fresh thrombus material on their surface. After clipping, a thin layer of endothelial lining bridging the two attached vessel walls was present, thereby completely obliterating the aneurysm and reconstructing the vessel wall. CONCLUSION: This study demonstrates complete and stable aneurysm obliteration with vessel wall reconstruction after clipping, a sufficient obliteration of the aneurysm dome using endovascular techniques, but a failed healing response of the aneurysm neck that might correlate to its associated higher risk of rebleed. Whether or not this is counterbalanced by the better immediate outcome after endovascular treatment remains a matter of debate.

Animals↗
PubMed2006

Spinal dural arteriovenous fistula associated with a spinal perimedullary fistula: case report.

Among spinal cord vascular malformations, dural arteriovenous fistulas (DAVFs) must be distinguished from intradural malformations. The concurrence of both is extremely rare. The authors report the case of a 35-year-old man who suffered from progressive myelopathy and who harbored both a DAVF and an intradural perimedullary fistula. During surgery, both fistulas were identified, confirmed, and subsequently obliterated. The fistulas were located at two levels directly adjacent to each other. Although the incidence of concurrent spinal DAVFs is presumed to be approximately 2%, the combination of a dural and an intradural fistula is exceedingly rare; only two other cases have been reported in the literature. One can speculate whether the alteration in venous drainage caused by the (presumably congenital) perimedullary fistula could possibly promote the production of a second dural fistula due to elevated pressure with concomitant venous stagnation and subsequent thrombosis. The authors conclude that despite the rarity of dual pathological entities, the clinician should be aware of the possibility of the concurrence of more than one spinal fistula in the same patient.

Adult↗
PubMed2006

Spinal epidural arteriovenous fistula with perimedullary drainage. Case report and pathomechanical considerations.

The classic angiographically demonstrated features of spinal dural arteriovenous fistulas are shunts of radiculomeningeal branches with radicular veins draining exclusively in the direction of perimedullary veins and thereby causing venous congestion. These shunts are located at the point where the radicular vein passes the dura mater. Spinal epidural arteriovenous shunts, however, normally do not drain into the perimedullary veins and are, therefore, asymptomatic, presumably because of a postulated reflux-impeding mechanism between the dural sleeves. The authors report on a patient in whom an epidural arteriovenous shunt showed delayed retrograde drainage into perimedullary veins, leading to the classic clinical (and magnetic resonance imaging-based) findings of venous congestion. Intraoperatively the angiographically established diagnosis was confirmed. Coagulation of both the epidural shunt zone and the radicular vein resulted in complete obliteration of the fistula, as confirmed on repeated angiography. This rare type of fistula should stimulate considerations on the role of valvelike mechanisms normally impeding retrograde flow from the epidural plexus to perimedullary veins and suggest that, in certain pathological circumstances, epidural fistulas can drain retrogradely into perimedullary veins as an infrequent variant of spinal arteriovenous shunts.

Aged↗
PubMed2005

Intracranial arterial aneurysm vasculopathies: targeting the outer vessel wall.

The pathogenesis of intracranial arterial aneurysms (AA) remains unclear, despite their clinical importance. An improved understanding of this disease is important in choosing therapeutic options. In addition to the "classical" berry-type aneurysm, there are various other types of intracranial AA such as infectious, dissecting or giant, partially-thrombosed aneurysms. From the clinician's perspective, the hypothesis that some of these intracranial AA might be due to abluminal factors has been proposed for several years. Indeed, this hypothesis and the empirical use of anti-inflammatory drugs in giant intracranial aneurysms have been confirmed by recent studies reporting that an enzyme involved in the inflammatory cascade (5-lipoxygenase or 5-LO) promotes the pathogenesis of specific aneurysms in humans. 5-LO generates different forms of leukotrienes which are potent mediators of inflammation. Adventitial inflammation leads to a weakening of the media from the abluminal part of the vessel wall due to the release of proinflammatory factors that invade the media, thereby degrading the extracellular matrix, the elastic lamina of the vascular wall, and, finally, the integrity of the vessel lumen. This in turn results in a dilation of the vessel and aneurysm formation. Moreover, neoangiogenesis of vasa vasorum is found in close proximity to 5-LO activated macrophages. In addition to this biological cascade, we argue that repeated subadventitial haemorrhages from the new vasa vasorum play an important role in aneurysm pathogenesis, due to a progressive increase in size mediated by the apposition of new layers of intramural haematoma within the vessel wall. Intracranial giant AA can therefore be regarded as a proliferative disease of the vessel wall induced by extravascular activity. Considering certain aneurysmal vasculopathies as an abluminal disease might alter current therapeutic strategies. Therapy should not only be aimed at the intraluminal repair of the artery, but also cross the vessel wall to reach the vasa vasorum. Drug-eluting stents placed proximal to the lesion and targeted to the origin of the vasa vasorum could be considered as a potential future option. "Intelligent" MRI contrast agents (i.e., macrophage marking) could be used to detect vasa vasorum proliferation and weakening of the vessel wall in vivo.

Anti-Inflammatory Agents↗
PubMed2005

Prospective demonstration of short-term motor plasticity following acquired central pareses.

The effect of newly acquired central pareses on functional MRI (fMRI) signal pattern is not known, since up to now all investigated patients were examined while they already experienced the motor weakness. We describe the first prospective and controlled study demonstrating the impact of new, acquired central pareses on fMRI motor activation pattern. Six patients suffering from a new central paresis after resection of a brain tumor infiltrating the central region were prospectively compared with a control group of five patients without postoperative paresis and a group of six healthy, age-matched controls who were investigated at two time points. fMRI signal was postoperatively analyzed during the performance of hand motor tasks and compared to the preoperative fMRI results. The relative signal change between rest and activation was evaluated for five cortical regions: the primary motor cortex (M1) and the ipsilateral primary motor cortex (M1i), the supplementary motor area (SMA), the premotor area (PMA), and the superior parietal lobule (SPL). In the patients with new postoperative central pareses, significant (P = 0.0313) decreases in fMRI activation were found in M1, whereas significant (P = 0.0313) increases were found in SMA and PMA. For M1i and SPL, there was a signal increase on average as well, but it failed to reach significance (P = 0.1250). In both control groups, no significant changes between both examinations were seen. Even though the number of investigated patients is too small to draw definite conclusions, our results support the concept of short-term motor plasticity being mediated by redundant systems that may take over function after damage of the primary motor cortex. The findings potentially also reflect increased functional demands imposed upon the motor network subsequent to a loss of dexterity.

Adult↗
PubMed2005

Effects of long-term practice and task complexity in musicians and nonmusicians performing simple and complex motor tasks: implications for cortical motor organization.

Motor practice induces plastic changes within the cortical motor system. Whereas rapidly evolving changes of cortical motor representations were the subject of a number of recent studies, effects of long-term practice on the motor system are so far poorly understood. In the present study pianists and nonmusicians were investigated using functional magnetic resonance imaging. Both groups performed simple and complex movement sequences on a keyboard with the right hand, the tasks requiring different levels of ordinal complexity. The aim of this study was to characterize motor representations related to sequence complexity and to long-term motor practice. In nonmusicians, complex motor sequences showed higher fMRI activations of the presupplementary motor area (pre-SMA) and the rostral part of the dorsal premotor cortex (PMd) compared to simple motor sequences, whereas musicians showed no differential activations. These results may reflect the higher level of visuomotor integration required in the complex task in nonmusicians, whereas in musicians this rostral premotor network was employed during both tasks. Comparison of subject groups revealed increased activation of a more caudal premotor network in nonmusicians comprising the caudal part of the PMd and the supplementary motor area. This supports recent results suggesting a specialization within PMd. Furthermore, we conclude that plasticity due to long-term practice mainly occurs in caudal motor areas directly related to motor execution. The slowly evolving changes in M1 during motor skill learning may extend to adjacent areas, leading to more effective motor representations in pianists.

Adult↗
PubMed2005

The neural correlate of very-long-term picture priming.

Repetition priming denotes a behavioural change caused by prior exposure to a stimulus. The effect is known to last for weeks. This study addresses the underlying neural mechanisms for very-long-term picture priming by using event-related functional magnetic resonance imaging complemented by a behavioural paradigm. Previous functional imaging studies with shorter retention intervals have shown that priming is associated with changes in the activity of both the occipital and posterior temporal cortex. In this study we compared retention intervals of 1 day and 6 weeks after initial exposure to a picture stimulus. Priming-related decreases in cortical activity in posterior extrastriate and dorsal left inferior frontal areas were found only for the shorter retention interval. In contrast, fMRI activation in the inferior posterior temporal and anterior left inferior frontal cortex was reduced following priming for both retention intervals. In the behavioural paradigm, the priming effect was stable over time. We conclude that the left inferior frontal and inferior posterior temporal cortex play a key role in the very-long-term priming effect.

Adult↗
PubMed2005

Sequential visualization of brain and fiber tract deformation during intracranial surgery with three-dimensional ultrasound: an approach to evaluate the effect of brain shift.

OBJECTIVE: We present a technique that allows intraoperative display of brain shift and its effects on fiber tracts. METHODS: Three patients had intracranial lesions (one malignant glioma, one metastasis, and one cavernoma) in contact with either the corticospinal or the geniculostriate tract that were removed microneurosurgically. Preoperatively, magnetic resonance diffusion-weighted imaging (DWI) was performed to visualize the fiber tract at risk. DWI data were fused with those obtained from anatomic T1-weighted magnetic resonance imaging. A single-rack three-dimensional ultrasound neuronavigation system, which simultaneously displays the MRI scan and the corresponding ultrasound image, was used intraoperatively for 1) navigation; 2) definition of fixed and potentially shifting ultrasound landmarks near the fiber tract; and 3) sequential image updating at different steps of resection. The result was time-dependent brain deformation data. With a standard personal computer equipped with standard image software, the brain shift-associated fiber tract deformation was assessed by use of sequential landmark registration. After surgery, DWI was performed to confirm the predicted fiber tract deformation. RESULTS: The lesions were removed without morbidity. Comparison of three-dimensional ultrasound with DWI and T1-weighted magnetic resonance imaging data allowed us to define fixed and potentially shifting landmarks close to the respective fiber tract. Postoperative DWI confirmed that the actual fiber tract position at the conclusion of surgery corresponded to the sonographically predicted fiber tract position. CONCLUSION: By definition and sequential intraoperative registration of ultrasound landmarks near the fiber tract, brain shift-associated deformation of a tract that is not visible sonographically can be assessed correctly. This approach seems to help identify and avoid eloquent brain areas during intracranial surgery.

Adolescent↗
PubMed2005

Treatment of experimentally induced aneurysms with stents.

OBJECTIVE: Although Guglielmi detachable coil systems have been widely accepted for treatment of intracranial aneurysms, primary stenting of aneurysms using porous stents, stent grafts, or implantation of coils after stent placement constitute emerging techniques in endovascular treatment. The aim of the present study was to use an animal model to investigate these different approaches to treat cerebral aneurysms with regard to the rate of closure and the histopathological changes within the aneurysm cavity and the parent vessel after stent placement. METHODS: We created aneurysms in 30 rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. Ten animals were treated with porous stents alone, 10 animals with stent grafts (covered stents), and 10 animals with stents and additional coiling via the interstices of the stent, which enabled dense packing of the coils. Five animals in each group were observed for 1 month and the other animals for 3 months. Histological analyses were performed, including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration. RESULTS: Covered stents led to a complete and stable aneurysm occlusion with only minimal proliferative carrier vessel wall changes. One covered stent was completely occluded with old thrombus, and the other 9 remained patent. Porous stents occluded two of five aneurysms in the 1-month follow-up group and four of five after 3 months. However, progressive sprouting of neointima inside the carrier vessel that resulted in a stenosis of up to 40% was present. In the Stent + Coil group, one aneurysm showed recanalization after 1 month, and three of five aneurysms were recanalized after 3 months after coil compaction. Moreover, in-stent stenosis of up to 30% was present. CONCLUSION: This study demonstrates the possible shortcomings and problems of emerging stent techniques to treat intracerebral aneurysms, shows where technical advances have to be made, and describes in which cases of aneurysm morphology caution has to be exercised when considering an endovascular approach using stents.

Aneurysm↗
PubMed2004

MR-imaging of thrombus in extra- and intracranial arteries employing balanced fast-field echo MRI.

Causes of stroke in young adults include a variety of disorders that are less frequently seen in older patients. We report the case of a young patient, who suffered recurrent mild embolic infarctions from a free-floating thrombus formation of the internal carotid artery bulb. During preoperative preparation, the thrombus dislodged and led to middle cerebral artery occlusion and major stroke. Both during preoperative work-up and after thrombus displacement balanced fast field echo sequences were able to demonstrate thrombus with a high signal-to-noise ratio and a superior delineation of thrombus and flowing blood. The high contrast between blood and thrombus helped to establish the diagnosis, to plan subsequent treatment strategies and to follow closely the clinical course. Further studies have to show whether this technique might help in thrombus characterization.

Adult↗
PubMed2004

Spinal vascular malformations.

Spinal vascular malformations are rare diseases that consist of true inborn cavernomas and arteriovenous malformations (including perimedullary fistulae, glomerular and juvenile AVMs) and presumably acquired dural arteriovenous fistulae. This review article gives an overview of the imaging features both on MRI and angiography, the differential diagnoses, the clinical symptomatology and the potential therapeutic approaches to these diseases. It is concluded that MRI is the diagnostic modality of first choice in suspected spinal vascular malformation and should be complemented by selective spinal angiography. Treatment in symptomatic patients offers an improvement in the prognosis, but should be performed in specialized centers. Patients with spinal cord cavernomas and perimedullary fistulae type I are surgical candidates. Dural arteriovenous fistulae can either be operated upon or can be treated by an endovascular approach, the former being a simple, quick and secure approach to obliterate the fistula, while the latter is technically demanding. In spinal arteriovenous malformations, the endovascular approach is the method of first choice; in selected cases, a combined therapy might be sensible.

Angiography↗
PubMed2004

[Fulminant meningoencephalitis associated with Mycoplasma pneumoniae infection in adults. Aggressive treatment enabled a good outcome].

Mycoplasma pneumoniae (M. pn.) commonly causes respiratory tract infections in humans. In a certain percentage of cases it may also be associated with various peripheral and central nervous system manifestations. We report a case of a 38-year-old previously healthy man who presented with hemiplegia and somnolence after he had suffered from a febrile respiratory infection 10 days earlier. Clinical features and laboratory investigations supported the diagnosis of an acute M. pneumoniae-associated meningoencephalitis. He was treated by an aggressive antibiotic and immunomodulatory regimen over the course of several weeks in the neurocritical care unit. Decompressive hemicraniectomy was performed due to life-threatening raised intracranial pressure. However, the patient recovered almost completely and presented with a mild neurological deficit after 3 months. Based on this case we give a review of the literature and discuss potential pathomechanisms and diagnostic approaches.

Adult↗
PubMed2004

Diffusion-tensor imaging in septo-optic dysplasia.

One of the morphological correlates of septo-optic dysplasia is hypoplasia of the optic nerves. As of now, it remains unknown, in how far this disorder also affects the organization of the optic radiation. Using diffusion-tensor imaging (DTI), the non-invasive evaluation of large fiber tracts including the optic radiation has become possible. We have compared DTI-data from a patient suffering from septo-optic dysplasia with those of a group of eleven healthy control subjects. The anisotropy showed statistically significant reduction in the patient with septo-optic dysplasia within the visual fiber tracts and an unordered eigenvector map. A comparison of the anisotropy in the pyramidal tract showed no significant difference. Since the patient was congenitally blind, it remains unclear whether the findings are the results of the underlying disorder or occur in all congenitally blind patients. One might presume, that, in order for the optic radiation to fully develop, an afferent input to the lateral geniculate body is necessarry.

Adult↗
PubMed2004

Imaging of postthalamic visual fiber tracts by anisotropic diffusion weighted MRI and diffusion tensor imaging: principles and applications.

Diffusion weighted MRI offers the possibility to study the course of the cerebral white matter tracts. In the present manuscript, the basics, the technique and the limitations of diffusion tensor imaging and anisotropic diffusion weighted MRI are presented and their applications in various neurological and neurosurgical diseases are discussed with special emphasis on the visual system. A special focus is laid on the combination of fiber tract imaging, anatomical imaging and functional MRI for presurgical planning and intraoperative neuronavigation of lesions near the visual system.

Brain Diseases↗