Randolf Klingebiel

Differential activation of the dorsal striatum by high-calorie visual food stimuli in obese individuals

The neural systems regulating food intake in obese individuals remain poorly understood. Previous studies applied positron emission tomography and manipulated hunger and satiety to investigate differences in appetitive processing between obese and normal-weight individuals. However, it is not known whether manipulation of stimulus value may yield different neural activity in obese as compared to control subjects when intrinsic physiological states are kept constant. We used functional magnetic resonance imaging to investigate 13 obese and 13 normal-weight subjects and manipulated food motivation by presenting visual food stimuli differing in their caloric content and energy density. In contrast to controls, obese women selectively activated the dorsal striatum while viewing high-caloric foods. Moreover, in the high-calorie condition body mass index (BMI) predicted activation in the dorsal striatum, anterior insula, claustrum, posterior cingulate, postcentral and lateral orbitofrontal cortex. The results indicate that in obese individuals simple visual stimulation with food stimuli activates regions related to reward anticipation and habit learning (dorsal striatum). Additionally, high-calorie food images yielded BMI-dependent activations in regions associated with taste information processing (anterior insula and lateral orbitofrontal cortex), motivation (orbitofrontal cortex), emotion as well as memory functions (posterior cingulate). Collectively, the results suggest that the observed activation is independent of the physiological states of hunger and satiation, and thus may contribute to pathological overeating and obesity. Some of the observed activations (dorsal striatum, orbitofrontal cortex) are likely to be dopamine-mediated.

Gray matter abnormalities in subjects at ultra-high risk for schizophrenia and first-episode schizophrenic patients compared to healthy controls

Neuroimaging studies have revealed gray matter abnormalities in schizophrenia in various regions of the brain. It is, however, still unclear whether such abnormalities are already present in individuals at ultra-high risk (UHR) for transition into psychosis. We investigated this issue using voxel-based morphometry of structural magnetic resonance images (MRI) and compared UHR patients with first-episode patients with schizophrenia and healthy controls. Gray matter volume maps from high-resolution MR T1-weighted whole brain images were analyzed in a cross-sectional study in 30 UHR patients, 23 first-episode schizophrenic patients and 29 controls. UHR patients showed significantly lower gray matter volume in the cingulate gyrus bilaterally, in the right inferior frontal and right superior temporal gyrus, as well as in the left and right hippocampus in comparison to healthy subjects. First-episode patients with schizophrenia showed smaller gray matter volume in the cingulate cortex bilaterally, in the left orbitofrontal gyrus, in the right inferior frontal and superior temporal gyrus, in the right temporal pole, in the left and right hippocampus, in the left parahippocampus, left amygdala, and in the left fusiform gyrus compared to the UHR patients. This study provides further evidence that gray matter brain volume, especially in the anterior cingulate cortex, is already reduced in the prodromal state of schizophrenia.

In vivo viscoelastic properties of the brain in normal pressure hydrocephalus

Nearly half a century after the first report of normal pressure hydrocephalus (NPH), the pathophysiological cause of the disease still remains unclear. Several theories about the cause and development of NPH emphasize disease‐related alterations of the mechanical properties of the brain. MR elastography (MRE) uniquely allows the measurement of viscoelastic constants of the living brain without intervention. In this study, 20 patients (mean age, 69.1 years; nine men, 11 women) with idiopathic (n = 15) and secondary (n = 5) NPH were examined by cerebral multifrequency MRE and compared with 25 healthy volunteers (mean age, 62.1 years; 10 men, 15 women). Viscoelastic constants related to the stiffness (µ) and micromechanical connectivity (α) of brain tissue were derived from the dynamics of storage and loss moduli within the experimentally achieved frequency range of 25–62.5 Hz. In patients with NPH, both storage and loss moduli decreased, corresponding to a softening of brain tissue of about 20% compared with healthy volunteers (p < 0.001). This loss of rigidity was accompanied by a decreasing α parameter (9%, p < 0.001), indicating an alteration in the microstructural connectivity of brain tissue during NPH. This disease‐related decrease in viscoelastic constants was even more pronounced in the periventricular region of the brain. The results demonstrate distinct tissue degradation associated with NPH. Further studies are required to investigate the source of mechanical tissue damage as a potential cause of NPH‐related ventricular expansions and clinical symptoms. Copyright

Internal jugular vein valve incompetence and intracranial venous anatomy in transient global amnesia

Background: Recently a causal relation between internal jugular vein valve incompetence (IJVVI) and transient global amnesia (TGA) has been suggested. IJVVI is postulated to provoke a transient mesiotemporal ischaemia by venous congestion. This mechanism requires a patent venous pathway from the affected IJV through the transverse sinus, confluens, straight sinus (SS), vein of Galen into the basal vein of Rosenthal and the internal cerebral veins. Objective: To study IJVVI in TGA patients in relation to the intracranial venous anatomy. Methods: IJVVI was defined if a repeated Valsalva manoeuvre (VM) led to a retrograde jugular flow detected by extracranial duplex ultrasound. Non-contrast venous MR angiography (MRA) was performed to analyse intracranial drainage patterns of the SS in relation to the side of the IJVVI. SS drainage was differentiated into three groups: predominantly right, left, and bilateral drainage. Ultrasound studies were performed in 25 TGA patients and 85 age matched controls. Twenty patients underwent venous MRA. Results: Sixty eight per cent of patients and 33% of controls showed unilateral or bilateral IJVVI (p  =  0.0025). In 36% of patients a TGA preceding VM was reported. Drainage pattern of SS and side of IJVVI corresponded in five of eight patients (63%) with VM and four of 12 patients without VM (33%, p  =  0.0994). Conclusion: Our study confirms the significantly higher prevalence of IJVVI in TGA patients. However, no specific IJVVI related intracranial venous drainage patterns could be found to further support the hypothesis of a direct causal relation between IJVVI and TGA.

4-D Imaging in Cerebrovascular Disorders by Using 320-Slice CT: Feasibility and Preliminary Clinical Experience

RATIONALE AND OBJECTIVES The authors report study protocols and initial clinical experience in assessing patients with acute and chronic cerebrovascular disorders using the recently introduced technique of volume computed tomography (VCT). MATERIALS AND METHODS Thirteen patients with presumptive cerebrovascular insufficiency underwent VCT using a 320-slice scanner (detector width, 160 mm), including time-resolved whole-brain perfusion and cerebral angiography (four-dimensional computed tomographic angiography [CTA] and computed tomographic perfusion [CTP]). Unenhanced cranial CT (cCT) and helical cervicocranial CT (three-dimensional CTA) were added according to clinical requirements. Study protocols are presented, and image quality, data management, and radiation exposure issues are discussed. RESULTS In 12 of 13 patients, the procedure was performed successfully on admission; in the other patient, the study was aborted for clinical reasons and repeated. Total scan time amounted to about 5 minutes, and data reconstruction times were up to 10 minutes. About 9000 primary images were generated, partially in the enhanced Digital Imaging and Communications in Medicine format, thus requiring new data postprocessing and management strategies. Image artifacts restricted the use of single-rotation cCT and incremental VCT (three-dimensional CTA). Overall exposure figures (computed tomographic dose index and dose-length product) were increased by 65% on average when three-dimensional CTA was added to volume cCT and four-dimensional CTA and CTP (5.0 mSv and 2178 mGy . cm, respectively). CONCLUSION Preliminary clinical experience indicates that whole-brain four-dimensional CTA and CTP is a robust technique that provides relevant clinical information with respect to whole-brain perfusion as well as cerebral hemodynamics. The exposure benefit of deriving time-resolved perfusion and vessel images from one source data set is compromised when adding three-dimensional CTA to the protocol. Other acquisition techniques specific to VCT, such as single-rotation cCT and incremental three-dimensional CTA, suffer from restrictions in terms of image quality at present.

Lumbar spinal stenosis: syndrome, diagnostics and treatment

Lumbar spinal stenosis (LSS) comprises narrowing of the spinal canal with subsequent neural compression, and is frequently associated with symptoms of neurogenic claudication. To establish a diagnosis of LSS, clinical history, physical examination results and radiological changes all need to be considered. Patients who exhibit mild to moderate symptoms of LSS should undergo multimodal conservative treatment, such as patient education, pain medication, delordosing physiotherapy and epidural injections. In patients with severe symptoms, surgery is indicated if conservative treatment proves ineffective after 3–6 months. Clinically relevant motor deficits or symptoms of cauda equina syndrome remain absolute indications for surgery. The first randomized, prospective studies have provided class I–II evidence that supports a more rapid and profound decline of LSS symptoms after decompressive surgery than with conservative therapy. In the absence of a valid paraclinical diagnostic marker, however, more evidence-based data are needed to identify those patients for whom the benefit of surgery would outweigh the risk of developing complications. In this Review, we briefly survey the underlying pathophysiology and clinical appearance of LSS, and explore the available diagnostic and therapeutic options, with particular emphasis on neuroradiological findings and outcome predictors.

Dose Exposure of Patients Undergoing Comprehensive Stroke Imaging by Multidetector-Row CT: Comparison of 320-Detector Row and 64-Detector Row CT Scanners

BACKGROUND AND PURPOSE: Recently introduced 320-detector row CT enables whole brain perfusion imaging compared to a limited scanning area in 64-detector row CT. Our aim was to evaluate patient radiation exposure in comprehensive stroke imaging by using multidetector row CT consisting of standard CT of the head, CTA of cerebral and cervical vessels, and CTP. MATERIAL AND METHODS: Organ doses were measured by using LiF-TLDs located at several organ sites in an Alderson-Rando phantom. Effective doses were derived from these measurements. Stroke protocols including noncontrast head CT, CTA of cerebral and cervical vessels, and CTP were performed on 320- and 64-detector row scanners. RESULTS: Measured effective doses for the different scanning protocols ranged between 1.61 and 4.56 mSv, resulting in an effective dose for complete stroke imaging of 7.52/7.54 mSv (m/f) for 64-detector row CT and 10.56/10.6 mSv (m/f) for 320-detector row CT. The highest organ doses within the area of the primary beam were measured in the skin (92 mGy) and cerebral hemispheres (69.91 mGy). Use of an eye-protection device resulted in a 54% decrease of the lens dose measured for the combo protocol for whole-brain perfusion with the 320-detector row CT scanner. CONCLUSIONS: Phantom measurements indicate that comprehensive stroke imaging with multidetector row CT may result in effective radiation doses from 7.52 mSv (64-detector row CT) to 10.6 mSv (320-detector row CT). The technique of 320-detector row CT offers additional information on the time course of vascular enhancement and whole-brain perfusion. Physicians should weigh the potential of the new technique against the higher radiation dose that is needed. Critical doses that would cause organ damage were not reached.

White matter abnormalities in subjects at ultra high-risk for schizophrenia and first-episode schizophrenic patients

Schizophrenia is associated with neuroanatomical abnormalities. Gray matter decrease seems to predate first schizophrenic episode. Whether white matter abnormalities predate the onset of psychotic symptoms is unclear. We investigated this issue using voxel-based morphometry (VBM) of structural magnetic resonance images to examine individuals with prodromal symptoms who were at ultra high-risk (UHR) of developing schizophrenia and compared them to first-episode schizophrenic patients and healthy controls. White matter volume maps from high-resolution magnetic resonance T1 weighted whole brain images were analyzed in a cross-sectional study using SPM2 in 30 UHR patients, 23 first-episode schizophrenic patients and 29 healthy controls. UHR patients showed significant lower white matter volume in the right superior temporal lobe compared to healthy controls. First-episode patients with schizophrenia showed widespread smaller white matter volume bilaterally compared to UHR patients. This study provides first evidence for smaller white matter volume in the right temporal lobe of UHR patients, one of the key structures in the pathophysiology of schizophrenia. Furthermore, white matter abnormalities seem to progress after transition into schizophrenia.

Opening of the blood-brain barrier preceding cortical edema in a severe attack of FHM type II

The authors report a patient with familial hemiplegic migraine type II who developed a long-lasting attack including fever, right-sided hemiplegia, aphasia, and coma. Quantitative analysis of early gadolinium-enhanced MRI revealed a mild but significant left-hemispheric blood-brain barrier (BBB) opening limited to the cortex and preceding cortical edema. The findings suggest that the delayed cortical edema was vasogenic in the severe migraine aura variant of this ATP1A2 mutation carrier.

Multi-slice CT angiography in the evaluation of patients with acute cerebrovascular disease – a promising new diagnostic tool

Abstract Single-slice computed tomographic angiography (CTA) is an established imaging method for the cerebrovascular system (CVS), but it suffers from technical limitations with respect to the coherent high resolution visualization of longer vascular segments, such as the extra- and intracranial CVS. The recently introduced multi-slice (MS) technology has been attributed with a superior imaging quality for angiographic procedures due to increased scan speed and improved spatial resolution. The purpose of this study was to evaluate the suitability of multi-slice CTA (MS-CTA) for the assessment of the arteriovenous CVS in patients with acute symptoms of either arterial or venous occlusive diseases. 41 patients with clinically suspected acute cerebral ischaemia (hemispheric in 29 and vertebrobasilar in 12 patients) and 4 patients with suspected cerebral venous thrombosis (CVT) underwent CTA in a MS-CT scanner. In addition, doppler ultrasonography (DUS) was performed in 34, magnetic resonance angiography (MRA) in 5 and digital subtraction angiography (DSA) in 6 patients. All findings were reviewed for stenoses or occlusion of the extra- and intracranial CVS and correlated with the clinical outcome. In 43 (96 %) of 45 patients, MS-CTA yielded images of diagnostic quality with comprehensive visualization of the arterial and venous CVS including the cervical carotid bifurcation, the third segment of the major cerebral arteries and the dural sinus as well as internal cerebral veins. In 2 patients, assessment of the carotid bifurcation was limited because of tooth artefacts. In all patients, in whom imaging and clinical follow-up proved a non-lacunar infarction (n=22), MS-CTA detected the underlying vascular pathology. Suspected CVT could be confirmed in 2 and ruled out in another 2 patients through MS-CTA. In conclusion, multi-slice CT angiography may be a promising new diagnostic tool for the rapid and comprehensive assessment of the arteriovenous CVS in patients with clinical signs of acute cerebrovascular diseases.