[Improved localization of spinal AV fistulas using contrast-enhanced MR angiography at 3 T]. / Verbesserte Lokalisationsdiagnostik der spinalen duralen AV-Fistel durch die CE-MRA bei 3 T.

PURPOSE: The standard for the detection and localization of spinal dural and perimedullary AV fistulas has been digital subtraction angiography. The purpose of this study was to correctly locate dural AV fistulas using high-resolution (hr), contrast-enhanced (ce) MRA at 3 T or at least to estimate the site within a range of two to three segments. As a result, the radiation exposure, contrast dose and risk of complications were able to be reduced. METHODS: Five patients with typical clinical symptoms and the characteristic signs in spinal MRI were examined at 3 T (GE Signa Excite HD). Hr, ce MR angiography and a time-resolved sequence (TRICKS) were compared and correlated with the subsequent DSA and the operation record with respect to the site of the fistula. In addition, the amount of contrast agent and the number of selectively catheterized segmental arteries in DSA were analyzed. RESULTS: In all patients, a dural AV fistula was able to be demonstrated by hr, ce MRA, and the side and the segmental level of the point of the fistula were correctly predicted and confirmed in subsequent DSA as well as in the operation record. In time-resolved MRA the determined location was correct in one of the five cases. In the remaining 4 cases no definitive mapping was possible. CONCLUSION: In hr, ce MRA at 3 T the localization of the point of the fistula in a spinal AVF is highly reliable so that the radiation time and the amount of contrast medium can be reduced. Hr, ce MRA is superior to the time-resolved sequence (TRICKS).

Hydrated silicate minerals on Mars observed by the Mars Reconnaissance Orbiter CRISM instrument.

Phyllosilicates, a class of hydrous mineral first definitively identified on Mars by the OMEGA (Observatoire pour la Mineralogie, L'Eau, les Glaces et l'Activitié) instrument, preserve a record of the interaction of water with rocks on Mars. Global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy (Fe/Mg and Al smectite clays). This was interpreted to indicate that phyllosilicate formation occurred during the Noachian (the earliest geological era of Mars), and that the conditions necessary for phyllosilicate formation (moderate to high pH and high water activity) were specific to surface environments during the earliest era of Mars's history. Here we report results from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) of phyllosilicate-rich regions. We expand the diversity of phyllosilicate mineralogy with the identification of kaolinite, chlorite and illite or muscovite, and a new class of hydrated silicate (hydrated silica). We observe diverse Fe/Mg-OH phyllosilicates and find that smectites such as nontronite and saponite are the most common, but chlorites are also present in some locations. Stratigraphic relationships in the Nili Fossae region show olivine-rich materials overlying phyllosilicate-bearing units, indicating the cessation of aqueous alteration before emplacement of the olivine-bearing unit. Hundreds of detections of Fe/Mg phyllosilicate in rims, ejecta and central peaks of craters in the southern highland Noachian cratered terrain indicate excavation of altered crust from depth. We also find phyllosilicate in sedimentary deposits clearly laid by water. These results point to a rich diversity of Noachian environments conducive to habitability.

The positive predictive value of O-(2-[18F]fluoroethyl)-L-tyrosine (FET) PET in the diagnosis of a glioma recurrence after multimodal treatment.

OBJECTIVE: To explore prospectively the positive predictive value of O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET)-PET in selected patients with a magnetic resonance imaging (MRI)-based suspicion of a glioma recurrence or progression. Methods Patients with a supratentorial glioma (initial World Health Organization (WHO) grade II, III or IV) were considered eligible if they had both an MRI-(new/progressive contrast-enhancing lesion) and FET-PET-based diagnosis of a recurrence/progression after various forms and combinations of irradiation and chemotherapy. Criterion for tumour recurrence/progression in FET-PET was a standardized uptake value (SUVmax)/Background (BG) ratio of >2.0 in the late uptake phase. All patients underwent multimodal (MRI, FET-PET) imaging-guided stereotactic biopsy. The positive predictive value was defined as the proportion of MRI and FET-PET findings indicating glioma recurrence/progression that also tested positive for tumour recurrence/progression after stereotactic biopsy. RESULTS: Thirty-one patients with initially WHO grade II (17), WHO grade III (6), and grade IV glioma (8) were included. In 26 patients FET-PET results indicating tumour recurrence/progression were concordant with the biopsy results. In five patients histopathologic evaluation failed to reveal a "vital" tumour. FET-PET findings were also discordant with the radiographic and clinical follow-up in these five patients. The positive predictive value of FET-PET was 84%. CONCLUSION: The positive predictive value of FET-PET using the standard ratio method is high, but not high enough to replace stereotactic biopsy in this highly selected study cohort. Whether the calculation of FET uptake in the early phase and/or the evaluation of uptake kinetics will improve the positive predictive value of FET-PET deserves prospective evaluation.

Deconvolution of bolus-tracking data: a comparison of discretization methods.

Model-free measurement of perfusion from bolus-tracking data requires a discretization of the tracer kinetic model. In this study a classification is provided of existing approaches to discretization, and the accuracy of these methods is compared. Two methods are included which are delay invariant (circulant and time shift) and three methods which are not (volterra, singular and hybrid). Simulations of magnetic resonance imaging (MRI) in the brain are performed for two tissue types (plug flow and compartment) with variable delay and dispersion times, temporal resolution and signal to noise. Simulations were compared to measurements in a patient data set. Both delay-invariant methods are equally accurate, but the circulant method is sensitive to data truncation. Overall volterra produces highest estimates of perfusion, followed by hybrid, singular and delay-invariant methods. Volterra is most accurate except in plug-flow without delay or dispersion, which represents an unrealistic tissue type. Differences between methods vanish when delay or dispersion times increase above the temporal resolution. It is concluded that when negative delays cannot be avoided or when an accurate estimate of left-right perfusion ratios is required, the time shift is the method of choice. When delays are certain to be positive and absolute accuracy is the objective, the volterra method is to be preferred.

A closer look at water-related geologic activity on Mars.

Water has supposedly marked the surface of Mars and produced characteristic landforms. To understand the history of water on Mars, we take a close look at key locations with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter, reaching fine spatial scales of 25 to 32 centimeters per pixel. Boulders ranging up to approximately 2 meters in diameter are ubiquitous in the middle to high latitudes, which include deposits previously interpreted as finegrained ocean sediments or dusty snow. Bright gully deposits identify six locations with very recent activity, but these lie on steep (20 degrees to 35 degrees) slopes where dry mass wasting could occur. Thus, we cannot confirm the reality of ancient oceans or water in active gullies but do see evidence of fluvial modification of geologically recent mid-latitude gullies and equatorial impact craters.

Diagnostic value of multidetector-row CT angiography in the evaluation of thrombosis of the cerebral venous sinuses.

BACKGROUND AND PURPOSE: The diagnosis of cerebral venous and sinus thrombosis (CVST) as a rare but important cause of stroke is challenging. We aimed to investigate the diagnostic value of multidetector-row CT angiography (MDCTA) as a fast and cost-effective imaging tool in diagnosing CVST. MATERIALS AND METHODS: Nineteen patients who presented with clinical symptoms of a possible CVST were included. All patients had received both MDCTA and MR imaging with venous MR-angiography. Three blinded readers were asked to identify the cerebral sinuses and veins in MDCTA and to evaluate the presence of CVST in MDCTA. Consensus reading with interpretation of the MR imaging served to establish the definite diagnosis. RESULTS: The consensus reading revealed CVST in 10 of the 19 patients. With MDCTA, the venous sinuses could be identified in 99.2% and the cerebral veins in 87.6% of cases. The sensitivity and specificity of MDCTA for the diagnosis of CVST were 100%. CONCLUSION: Our study demonstrates that MDCTA provides excellent sensitivity and specificity for the diagnosis of CVST. Further studies are needed to evaluate the diagnostic potential of MDCTA in specific subsets of the general entity of CVST such as cortical venous thrombosis, thrombosis of the cavernous sinus, and thrombosis of the internal cerebral veins.

Intraprocedural thrombus formation during coil placement in ruptured intracranial aneurysms: treatment with systemic application of the glycoprotein IIb/IIIa antagonist tirofiban.

BACKGROUND AND PURPOSE: When using detachable coils to treat intracranial aneurysms, thromboembolism is the most feared and frequently reported complication during or after endovascular therapy. The purpose of this study was to document the therapeutic effect of tirofiban on patency of the parent vessel, rate of rebleedings, and outcome of the patients in the setting of acute subarachnoidal hemorrhage. METHODS: A patient data base was retrospectively reviewed to identify patients in whom thrombus occurred during endovascular treatment of ruptured cerebral aneurysms within a 34-month period and who were treated with tirofiban. All patients underwent anticoagulation with heparin during endovascular treatment procedures. Sixteen patients (age range, 52.9 +/- 10.7 years; 10 women, 6 men) were identified with intraprocedural thrombus formation. The patency of the parent vessel was assessed in a retrospective analysis blinded to outcome. Eight patients received ventriculostomy and had a follow-up CT. RESULTS: Local nonocclusive thrombus at the coil surface was detected in 5 patients, in all of whom the thrombus was dissolved. In 10 patients, partial or total occlusion of the parent vessel occurred during the intervention; in 8 of these, the vessel was recanalized completely and in 2 drug administration was assisted by mechanical means. In 1 patient, however, the occlusion persisted. No periprocedural rebleedings of the ruptured aneurysm occurred; 3 of 8 ventriculostomies had clinically silent small local bleedings. CONCLUSION: The use of tirofiban in the setting of endovascular treatment of ruptured intracranial aneurysms to dissolve platelet aggregation seems relatively safe and effective.

A late Eemian aridity pulse in central Europe during the last glacial inception.

Investigating the processes that led to the end of the last interglacial period is relevant for understanding how our ongoing interglacial will end, which has been a matter of much debate (see, for example, refs 1, 2). A recent ice core from Greenland demonstrates climate cooling from 122,000 years ago driven by orbitally controlled insolation, with glacial inception at 118,000 years ago. Here we present an annually resolved, layer-counted record of varve thickness, quartz grain size and pollen assemblages from a maar lake in the Eifel (Germany), which documents a late Eemian aridity pulse lasting 468 years with dust storms, aridity, bushfire and a decline of thermophilous trees at the time of glacial inception. We interpret the decrease in both precipitation and temperature as an indication of a close link of this extreme climate event to a sudden southward shift of the position of the North Atlantic drift, the ocean current that brings warm surface waters to the northern European region. The late Eemian aridity pulse occurred at a 65 degrees N July insolation of 416 W m(-2), close to today's value of 428 W m(-2) (ref. 9), and may therefore be relevant for the interpretation of present-day climate variability.

Restitution of visual functions in cerebrally blind children.

In adult patients who suffer from a visual field defect due to cerebral lesions, visual functions can be restored by systematic visual field training. Such visual field training is not feasible in young, brain-damaged children, who are unable to cooperate like adults. We have already shown earlier [Werth, R., and Moehrenschlager, M. (1999). The development of visual functions in cerebrally blind children during a systematic visual field training. Restorative Neurology and Neuroscience, 15, 229-241.] that systematic visual field training, which requires no ability to understand instructions or to cooperate, is successful in brain-damaged children and may lead to complete recovery of the visual field within 3 months. The present study provides more behavioral evidence and a control of intraocular light scatter. In addition to the earlier study, the luminance difference thresholds in the recovered visual field were compared with those of a normal control group. Seventeen children aged 1-4 years who had been blind for more than 1 year after perinatal asphyxia and two children suffering from homonymous hemianopia due to asphyxic-ischemic lesions participated in systematic visual field training. The functional visual field was assessed with a specially designed arc perimeter. Visual functions developed within a training period of 3 months in 11 children who received visual field training, whereas there was no recovery in the control group (N=37). The findings support the assumption that systematic visual field training facilitates the development of vision in cerebrally blind children. In two children who recovered from blindness, it was shown in functional magnetic resonance imaging (fMRI) that brain tissue in the area of the visual cortex contralateral to the blind visual hemifield was activated by light. In two children suffering from asphyxic-ischemic lesions who did not recover only brain tissue in the area of the visual cortex contralateral to the good visual hemifield could be activated by light. These results support the assumption that activity in spared tissue of the striate and extrastriate visual cortex are a necessary condition for recovery of the visual field in children suffering from cerebral blindness.

Hypersomnia associated with bilateral posterior hypothalamic lesion. A polysomnographic case study.

We examined an obese 58-year-old patient with a bilateral posterior hypothalamic lesion of unknown etiology. A 24-hour polysomnography revealed a markedly increased total sleep time (17.6 h). During daytime, only 3 continuous wake phases occurred. REM periods occurred only between 5 p.m. and 6 a.m. We conclude from our results that, similar to the results from animal experiments, the posterior hypothalamus in humans plays a critical role in the maintenance of wakefulness.

[Localized invasive intracranial aspergillosis with multiple cranial nerve failure -- case report and review of the literature]. / Lokalinvasive intrakranielle Aspergillose mit multiplen Hirnnervenausfällen. Fallbericht und Literaturübersicht.

Contrary to the more frequent hematogenously spread cerebral aspergillosis, localized invasive intracranial aspergillosis is a fungal infection that can also occur in patients who are not severely immunosuppressed. This illness can be effectively treated in some of these patients by early and rigorous therapy. Localized invasion of the fungus, generally from one of the nasal sinuses, causes intracranial growth mainly along the base of the skull and larger vessels,where fibrous, granulomatous tissue develops. This generally leads to damage of the cranial nerves (primarily I-VI) as well as localized pain syndromes. We report on the clinical course documented by MRI of a patient with localized invasive intracranial aspergillosis who had multiple failure of cranial nerves following surgery for an aspergilloma of the maxillary sinus. Clinical course, imaging findings, and treatment of the illness are discussed with a review of the relevant literature.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: decrease in regional cerebral blood volume in hyperintense subcortical lesions inversely correlates with disability and cognitive performance.

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an arteriopathic syndrome related to a genetic defect on chromosome 19. Characteristic changes in CADASIL can be observed onT2-weighted MR images in the subcortical white matter. The purpose of this study was to measure changes of regional cerebral blood volume (rCBV) with dynamic contrast-enhanced MR imaging and to correlate the changes to disability and cognitive performance. METHODS: We obtained rCBV measurements of 24 individuals with proven CADASIL on a 1.5-T MR imaging unit. A susceptibility-weighted MR imaging sequence was used for bolus tracking. Principles of the indicator dilution theory were applied to estimate values of absolute rCBV (mL/100 g). Disability was determined by using the Rankin scale, and overall cognitive performance was assessed by using the Mini-Mental State Examination. RESULTS: The mean rCBV in the subcortical white matter that was hyperintense on the T2-weighted images (2.7 +/- 0.8 mL/100 g) was significantly lower than the rCBV in the white matter that appeared normal on the T2-weighted images (4.4 +/- 1.3 mL/100 g) (P <.05). The mean rCBV in the gray matter was within the normal range (8.3 +/- 1.7 mL/100 g). Both cognitive impairment and disability negatively correlated with rCBV in the subcortical white matter that was hyperintense (P <.05) but not with rCBV in the normal appearing white matter. rCBV did not correlate with age. CONCLUSION: rCBV measured in the hyperintense subcortical white matter in individuals with CADASIL was decreased and inversely correlated with disability and cognitive impairment.

[Parry-Romberg syndrome and Rasmussen syndrome: only an incidental similarity?]. / Parry-Romberg-Syndrom und Rasmussen-Syndrom: nur zufällige Ahnlichkeiten?

The Parry-Romberg syndrome is a rare and poorly understood disease characterized by slowly progressive, localized atrophy of the skin, subcutaneous tissue, muscles, and bones. The atrophy is typically localized in the face and begins in youth. In some patients, imaging can show the lesions and atrophy of the ipsilateral hemisphere of the brain. We report on a patient in whom the disease has lasted 36 years and discuss the possibility that the Parry-Romberg syndrome is related to known autoimmune disorders of the soft tissue (e.g., linear scleroderma) and Rasmussen's syndrome. There are some remarkable clinical similarities between these two syndromes, including age of onset, unilateral manifestation, and occurrence of focal seizures. It is most probable that both diseases have an autoimmunological background.

Identification and anatomic description of the anterior choroidal artery by use of 3D-TOF source and 3D-CISS MR imaging.

BACKGROUND AND PURPOSE: The importance of the anterior choroidal artery (AChA) is related to its supply of crucial anatomic structures, such as the internal capsule. Angiographically, the AChA can be detected in 71% to 98% of patients, but as yet, its visibility on MR images has not been evaluated. Our goal was to assess the sensitivity of MR imaging in the identification of the AChA and its anatomic characteristics. METHODS: Twenty volunteers underwent MR imaging with a 3D time-of-flight (3D-TOF) sequence, 10 of them additionally with a 3D Fourier transformation constructive interference in steady state (3D-CISS) sequence. The MR angiographic source images and the 3D-CISS images were analyzed independently by two neuroradiologists, who evaluated the ability to identify the different segments of the AChA and the posterior communicating artery (PComA) according to a previously defined scoring system (0 = not identified, 1 = most probably identified, 2 = identified with certainty). Additionally, three patients were examined who had an arteriovenous malformation (AVM) supplied by the AChA. RESULTS: In the volunteers, the PComA was identified with certainty in 87.5% on 3D-TOF sequences and in 95% on 3D-CISS sequences; the AChA was identified with certainty in 92.5% on 3D-TOF sequences and in 90% on 3D-CISS sequences. 3D-CISS images showed additional anatomic information in six of 20 vessels. In the three patients, the enlarged AChA was identified with certainty on both imaging sequences. CONCLUSION: The AChA can be reliably identified using both 3D-CISS sequences and the source images of the 3D-TOF sequence. MR imaging can be used to assess and follow-up AChA-related disorders, especially AVMs.

[Gliomatosis cerebri: two case reports with atypical clinical and neuroradiologic findings]. / Gliomatosis cerebri. Zwei Fallberichte mit atypischer klinischer und neuroradiologischer Befundkonstellation.

The diagnosis of the rare disease Gliomatosis cerebri requires the correlation of clinical, radiological, and pathological findings. We report on two patients with intravitally diagnosed gliomatosis cerebri. Due to the unusually high malignancy of the tumor cells, diagnosis was complicated by atypical findings such as gadolinium enhancement in MRI and raised intracranial pressure. The clinical course, differential diagnosis, and literature are summarized briefly.