Motivation alters response bias and neural activation patterns in a perceptual decision-making task.

Motivation has been demonstrated to affect individuals' response strategies in economic decision-making, however, little is known about how motivation influences perceptual decision-making behavior or its related neural activity. Given the important role motivation plays in shaping our behavior, a better understanding of this relationship is needed. A block-design, continuous performance, perceptual decision-making task where participants were asked to detect a picture of an animal among distractors was used during functional magnetic resonance imaging (fMRI). The effect of positive and negative motivation on sustained activity within regions of the brain thought to underlie decision-making was examined by altering the monetary contingency associated with the task. In addition, signal detection theory was used to investigate the effect of motivation on detection sensitivity, response bias and response time. While both positive and negative motivation resulted in increased sustained activation in the ventral striatum, fusiform gyrus, left dorsolateral prefrontal cortex (DLPFC) and ventromedial prefrontal cortex, only negative motivation resulted in the adoption of a more liberal, closer to optimal response bias. This shift toward a liberal response bias correlated with increased activation in the left DLPFC, but did not result in improved task performance. The present findings suggest that motivation alters aspects of the way perceptual decisions are made. Further, this altered response behavior is reflected in a change in left DLPFC activation, a region involved in the computation of perceptual decisions.

Quantitative apparent diffusion coefficients in the characterization of brain tumors and associated peritumoral edema.

BACKGROUND: Conventional magnetic resonance (MR) imaging has a number of limitations in the diagnosis of the most common intracranial brain tumors, including tumor specification and the detection of tumoral infiltration in regions of peritumoral edema. PURPOSE: To prospectively assess if diffusion-weighted MR imaging (DWI) could be used to differentiate between different types of brain tumors and to distinguish between peritumoral infiltration in high-grade gliomas, lymphomas, and pure vasogenic edema in metastases and meningiomas. MATERIAL AND METHODS: MR imaging and DWI was performed on 93 patients with newly diagnosed brain tumors: 59 patients had histologically verified high-grade gliomas (37 glioblastomas multiforme, 22 anaplastic astrocytomas), 23 patients had metastatic brain tumors, five patients had primary cerebral lymphomas, and six patients had meningiomas. Apparent diffusion coefficient (ADC) values of tumor (enhancing regions or the solid portion of tumor) and peritumoral edema, and ADC ratios (ADC of tumor or peritumoral edema to ADC of contralateral white matter, ADC of tumor to ADC of peritumoral edema) were compared with the histologic diagnosis. ADC values and ratios of high-grade gliomas, primary cerebral lymphomas, metastases, and meningiomas were compared by using ANOVA and multiple comparisons. Optimal thresholds of ADC values and ADC ratios for distinguishing high-grade gliomas from metastases were determined by receiver operating characteristic (ROC) curve analysis. RESULTS: Statistically significant differences were found for minimum and mean of ADC tumor and ADC tumor ratio values between metastases and high-grade gliomas when including only one factor at a time. Including a combination of in total four parameters (mean ADC tumor, and minimum, maximum and mean ADC tumor ratio) resulted in sensitivity, specificity, positive (PPV), and negative predictive values (NPV) of 72.9, 82.6, 91.5, and 54.3% respectively. In the ROC curve analysis, the area under the curve of the combined four parameters was the largest (0.84), indicating a good test. CONCLUSION: Our results suggest that ADC values and ADC ratios (minimum and mean of ADC tumor and ADC tumor ratio) may be helpful in the differentiation of metastases from high-grade gliomas. It cannot distinguish high-grade gliomas from lymphomas, and lymphomas from metastases. ADC values and ADC ratios in peritumoral edema cannot be used to differentiate edema with infiltration of tumor cells from vasogenic edema when measurements for high-grade gliomas, lymphomas, metastases, and meningiomas were compared.

The human amygdala is involved in general behavioral relevance detection: evidence from an event-related functional magnetic resonance imaging Go-NoGo task.

The amygdala is classically regarded as a detector of potential threat and as a critical component of the neural circuitry mediating conditioned fear responses. However, it has been reported that the human amygdala responds to multiple expressions of emotions as well as emotionally neutral stimuli of a novel, uncertain or ambiguous nature. Thus, it has been proposed that the function of the amygdala may be of a more general art, i.e. as a detector of behaviorally relevant stimuli [Sander D, Grafman J, Zalla T (2003) The human amygdala: an evolved system for relevance detection. Rev Neurosci 14:303-316]. To investigate this putative function of the amygdala, we used event related functional magnetic resonance imaging (fMRI) and a modified Go-NoGo task composed of behaviorally relevant and irrelevant letter and number stimuli. Analyses revealed bilateral amygdala activation in response to letter stimuli that were behaviorally relevant as compared with letters with less behavioral relevance. Similar results were obtained for relatively infrequent NoGo relevant stimuli as compared with more frequent Go stimuli. Our findings support a role for the human amygdala in general detection of behaviorally relevant stimuli.

Fluoroscopy-guided sacroplasty: special focus on preoperative planning from three-dimensional computed tomography.

BACKGROUND: Osteoporotic sacral insufficiency fractures are usually spontaneous or caused by discrete traumas. The fluoroscopic anatomy of the sacrum can be difficult to understand, and this is why sacroplasty is considered more challenging than ordinary vertebroplasties. PURPOSE: To demonstrate the planning of the procedure and the effectiveness of treatment with sacroplasty by means of three-dimensional computed tomography (3D CT) by combining multiplanar reconstructions (MPR) and volume-rendering technique (VRT). MATERIAL AND METHODS: Five elderly, osteoporotic patients with intense pelvic and hip pain underwent weeks of inconclusive clinical and radiological diagnostic efforts. Correct diagnosis was finally attained with magnetic resonance imaging (MRI) and CT. Plain radiographs rarely show fractures, and MR or CT examinations are necessary to demonstrate longitudinal fractures. The procedures were performed with digital biplane equipment using preoperative 3D CT planning procedures. Polymethyl methacrylate (PMMA) was injected to fill the fracture sites. RESULTS: The fractures were successfully treated with sacroplasty using PMMA. A new technique, which involves placing the needles along the long axis of the sacrum, was optimized to the individual patients' fractures and sacral anatomy by meticulous planning on a workstation with 3D CT data sets. It was technically successful in all five cases. Four of the five patients had sustained pain relief. CONCLUSION: Sacral insufficiency fractures are not uncommon and should be considered in the elderly population with low back pain. Sacroplasty using the optimized "long-axis technique" gave almost immediate pain relief for all five patients in our study material. No complications were observed.

Traumatic cervical injuries in ankylosing spondylitis.

PURPOSE: To demonstrate the importance of magnetic resonance (MR) and computed tomography (CT) in the evaluation of cervical traumas in patients suffering from ankylosing spondylitis. MATERIAL AND METHODS: Eleven patients with advanced ankylosing spondylitis were admitted to neurosurgical treatment after trauma to the neck region. All had neurological symptoms and were evaluated with plain X-ray, CT, and MR. RESULTS: CT with reformation sagittal and coronal plane was superior to plain X-ray films in demonstrating fractures and dislocations. MR was considered mandatory when evaluating changes in medulla and epidural hematomas, which were detected in 4 patients. The clinical outcome was poor in 5 patients and good in 6. The poorest outcome was seen in patients with cord contusion and epidural hematoma. CONCLUSION: We conclude that plain X-ray is of no greater importance in the acute phase of highest value in follow-up evaluation of the healing process and final position of the fractured vertebrae. Our protocol in the acute phase in traumatized ankylopoetic patients consists of lateral conventional X-ray, CT with reformatted images, and MR, the last-mentioned being important in detecting epidural hematoma that reduces the clinical outcome further if not removed. In our opinion, MR must be part of the radiological protocol following neck traumas in all patients with ankylosing spondylitis.

MR angiography in the follow-up of coiled cerebral aneurysms after treatment with Guglielmi detachable coils.

PURPOSE: Intra-arterial digital subtraction angiography (DSA) has been considered the gold standard examination in the follow-up of patients treated with Guglielmi detachable coils (GDCs). However, DSA is an invasive and expensive investigation and results in exposure to ionising radiation to both patient and operator. The aim of this study was to compare MR angiography (MRA) with DSA with regard to patency of the occlusion of aneurysms following GDC treatment. MATERIAL AND METHODS: We performed 75 MRA and DSA examinations on 51 patients treated with GDCs. The examinations were performed 3-36 months after embolisation and the interval between MRA and DSA was less than 1 week. Hard copies of both studies were interpreted retrospectively and independently for residual flow within the aneurysm, residual aneurysmal neck, and parent and branch vessel flow. RESULTS: Patency status of parent and branch vessel flow was correctly identified with MRA in all patients except 1. The sensitivity of MRA in revealing residual flow within the aneurysm was 97%. The specificity in ruling out residual flow within the aneurysm was 91%. CONCLUSION: MRA may replace DSA in the long-term follow-up of coiled cerebral aneurysms. The initial follow-up examination should, however, include both modalities.

Effect of Guglielmi detachable coil placement on intraaneurysmal pressure: experimental study in canines.

BACKGROUND AND PURPOSE: Treatment of ruptured aneurysms with Guglielmi detachable coils (GDCs) has been shown to prevent repeat bleeding. To assess whether GDC coiling alters aneurysmal pressure, we measured intraaneurysmal pressure in two canine types of carotid artery aneurysms before and after GDC placement. METHODS: A 0.014-inch guidewire with a pressure transducer was inserted into parent arteries and domes of surgically created aneurysms. Intravascular static pressures were recorded before and during saline power injections (10, 20, and 30 mL over 1 and 2 s), before and after GDC placement. Common femoral arterial pressure was monitored. RESULTS: Saline power injections reproducibly and abruptly increased pressure in parent arteries and aneurysms. Mean intraaneurysmal pressure varied (18 +/- 4 [10 mL] to 75 +/- 15 mm Hg [30 mL]), independent of injection duration. Intraaneurysmal baseline pressures were higher after GDC placement (111 +/- 10 versus 93 +/- 15 mm Hg; P =.05). Aneurysmal pressure increases with saline injections were slightly higher after GDC placement, which dampened intraaneurysmal pressure amplitude at baseline (26.5 +/- 5.6 versus 19.6 +/- 7.4 mm Hg; P =.003) and during hypertension (25.3 +/- 5.4 versus 19.8 +/- 7.5 mm Hg, P =.002). The pressure increase slope with saline injection was delayed with GDC placement (0.24 +/- 0.1 versus 0.38 +/- 0.19 s; P <.001). CONCLUSION: Graded saline power injections into parent arteries can rapidly increase intraaneurysmal pressure. GDC treatment did not attenuate mean intraaneurysmal pressures, but both dampened the pressure amplitude and delayed pressure increases during locally induced hypertension.

Large middle cerebral artery infarctions and the hyperdense middle cerebral artery sign in patients with atrial fibrillation.

PURPOSE: Strokes in patients with atrial fibrillation are often due to large middle cerebral artery (MCA) infarctions, caused by cardiogenic emboli. The purpose of this study was to characterise the large MCA infarctions and to describe the prevalence and prognostic value of the hyperdense middle cerebral artery sign (HMCAS) in patients with atrial fibrillation. MATERIAL AND METHODS: The patient material comprised all 449 patients included in a randomised clinical trial of low molecular-weight heparin versus aspirin in patients with acute ischaemic stroke and atrial fibrillation. Patients with Scandinavian Stroke Scale score <8 were excluded. CT was performed on admission and at day 7, and was evaluated blinded to clinical data. The CT findings on admission were related to functional outcome at 14 days and 3 months, and incidence of cerebral haemorrhage within 7 days. RESULTS: Altogether 66/449 (15%) of the patients had large MCA infarctions. These patients had poorer clinical outcomes, and a higher frequency of haemorrhage on control CT within 7 days (15/59, 26% vs. 43/368, 12%). The HMCAS was found in 32/449 (7%) of the patients. It was significantly more frequent in patients with large MCA infarctions (17/66, 26% vs. 15/383, 4%), and was found most frequently within the first few hours following stroke onset. The HMCAS was associated with poor clinical outcomes and a higher frequency of cerebral haemorrhage, but these effects were partially explained by a preponderance of other risk factors in the HMCAS group. CONCLUSION: Large MCA infarction is a frequent finding in patients with atrial fibrillation. These patients have a high prevalence of the HMCAS, which is an early infarction sign and a marker of a poor prognosis.

Post-traumatic cerebral infarction. Neuroimaging findings, etiology and outcome.

PURPOSE: To assess the radiological characteristics of post-traumatic cerebral infarctions (PTCIs), the etiology and site of infarction, and to provide neuroimaging indicators of a poor clinical outcome. MATERIAL AND METHODS: A retrospective study of 16 patients with the neuroimaging-based diagnosis of PTCI was carried out. All CT, MR examinations, cerebral angiograms and medical records of the patients were reviewed. RESULTS: Infarcts were diagnosed in the territory of the posterior cerebral artery in 9 patients, in the middle cerebral artery in 5, in the anterior cerebral artery in 3, lenticulostriate-thalamoperforating in 2, vertebrobasilar in 3, and cortical infarcts in 2 patients. Neuroimaging studies suggested focal mass effect and/or acquired intracranial herniations as the cause of infarction in 13/16 patients (81.2%). In 3/16 patients (18.8%), PTCI was due to vascular injury of which 2 were angiographically documented (carotid artery dissection). Eight of the 16 patients in this study died or were left in a persistent vegetative state. Patients with associated subdural hematoma, brain swelling/edema and traumatic subarachnoid hemorrhage (tSAH) exhibited the worst outcome. CONCLUSION: Gross mechanical shift of the brain and herniation across the falx and/or tentorium accounted for infarction in a majority of cases in our study. The overall death rate was 43.8% and this result suggests that PTCI is an indication of a poor clinical outcome, especially among patients with associated subdural hematoma, brain swelling/edema and tSAH.

CTA in patients with acute subarachnoid haemorrhage. A comparative study with selective, digital angiography and blinded, independent review.

PURPOSE: Minimal- or non-invasive methods replacing intra-arterial digital subtraction angiography (IA-DSA) would be of great importance in patients suffering from acute subarachnoid haemorrhage (SAH). The aims of this study were to compare CTA with IA-DSA in patients with acute SAH, to compare CTA interpretations with those of blinded, independent reviewers and to evaluate improvement in CTA diagnostics after 1 year of experience with CTA. MATERIAL AND METHOD: During 2 years 162 patients with SAH underwent CTA as well as IA-DSA. Independent blinded review of 77 patients was performed for 1 year. RESULTS: Totally 144 aneurysms were demonstrated in 119 patients at IA-DSA, while 43 patients had normal intracranial arteries. Initially 131 aneurysms were detected at CTA while 2 normal, tortuous arteries were misinterpreted as aneurysms, giving a sensitivity of 91% and a specificity of 95%. At independent blinded review the observer agreement was 87% and the kappa value 0.68. CONCLUSION: CTA in SAH is of great value in demonstrating vascular anatomy and the exact size of an aneurysm. However, IA-DSA is still needed for diagnostic evaluation in aneurysms smaller than 5 mm in diameter, especially in those located near bony structures.

Improving postoperative MR imaging of pituitary macroadenomas: comparison of full and reduced dose of gadopentetate dimeglumine.

The aim of this study was to evaluate the efficacy of contrast-medium (CM)-ehanced MR imaging of operated pituitary macroadenomas with reduced dose of gadopentetate dimeglumine. In a prospective study 18 patients were examined with coronal T1-weighted MR imaging prior to and following intravenous CM injections. Two sets of contrast-enhanced coronal images were obtained in each patient; the first set after 50% of the recommended dose of 0.1 mmol/kg body weight (b.w.) had been administered, and the second set immediately after additional CM had been given to make up a total dose of 0.1 mmol/kg b.w. The images were evaluated by three neuroradiologists. The SIPAP classification system was used to evaluate tumour extension, whereas tumour margin conspicuity was scored using an arbitrary scale of 1-5 (1 = indistinct, 5 = well defined). Signal intensity measurements obtained from the most enhancing part of the adenomas demonstrated increased enhancement with increased CM dose. Tumour delineation scores were significantly better on the reduced- and full-dose images than on pre-CM injection images, but, with one exception, tumour extension was identified as the same on all imaging sequences. Postoperative MR imaging of large macroadenoma residues can routinely be performed without intravenous CM. When CM is indicated a reduced dose of gadopentetate dimeglumine should provide sufficient diagnostic information.

Failure to confirm neurotoxic impairment using cerebral magnetic resonance imaging on solvent-exposed workers.

OBJECTIVES: The study aimed at assessing signs of nervous system impairment by cerebral magnetic resonance imaging (MRI) among workers with a history of long-term exposure to mixtures of organic solvents. METHODS: Thirty-six workers (mean age 44.1 years) with at least 10 (mean 23.9) years of occupational exposure to solvents and pair-matched referents with no former solvent exposure went through a blind, random-order investigation of cerebral MRI, performed with a 1.5-tesla scanner. RESULTS: Linear measurements of the MRI tomograms showed a slight tendency toward wider ventricles and broader cortical sulci in the reference group. Visual evaluation of the MRI by 2 experienced neuroradiologists showed no significant difference between the groups; however, there was substantial interobserver variability. CONCLUSIONS: The MRI findings of this study do not support the hypothesis that long-term low-level occupational exposure to organic solvents results in the development of brain atrophy, or specific MRI signal changes in the region of the basal ganglia and thalami.

[Neurologic magnetic resonance tomography--indications and practical use]. / Nevroradiologisk magnetisk resonanstomografi--indikasjoner og bruksområder.

Magnetic resonance tomography is considered the most important technique in modern neuroradiology. This article demonstrates the importance of MR imaging in the diagnosis of diseases of the central nervous system. Modern neuroradiology is completely dependent upon this modality, and sections and departments of neuroradiology should have great responsibility for both diagnostic MR imaging and the day-to-day operation MR laboratories.

Low molecular-weight heparin versus aspirin in patients with acute ischaemic stroke and atrial fibrillation: a double-blind randomised study. HAEST Study Group. Heparin in Acute Embolic Stroke Trial.

BACKGROUND: Patients with acute ischaemic stroke and atrial fibrillation have an increased risk of early stroke recurrence, and anticoagulant treatment with heparins has been widely advocated, despite missing data on the balance of risk and benefit. METHODS: Heparin in Acute Embolic Stroke Trial (HAEST) was a multicentre, randomised, double-blind, and double-dummy trial on the effect of low-molecular-weight heparin (LMWH, dalteparin 100 IU/kg subcutaneously twice a day) or aspirin (160 mg every day) for the treatment of 449 patients with acute ischaemic stroke and atrial fibrillation. The primary aim was to test whether treatment with LMWH, started within 30 h of stroke onset, is superior to aspirin for the prevention of recurrent stroke during the first 14 days. FINDINGS: The frequency of recurrent ischaemic stroke during the first 14 days was 19/244 (8.5%) in dalteparin-allocated patients versus 17/225 (7.5%) in aspirin-allocated patients (odds ratio=1.13, 95% CI 0.57-2.24). The secondary events during the first 14 days also revealed no benefit of dalteparin compared with aspirin: symptomatic cerebral haemorrhage 6/224 versus 4/225; symptomatic and asymptomatic cerebral haemorrhage 26/224 versus 32/225; progression of symptoms within the first 48 hours 24/224 versus 17/225; and death 21/224 versus 16/225. There were no significant differences in functional outcome or death at 14 days or 3 months. INTERPRETATION: The present data do not provide any evidence that LMWH is superior to aspirin for the treatment of acute ischaemic stroke in patients with atrial fibrillation. However, the study could not exclude the possibility of smaller, but still worthwhile, effects of either of the trial drugs.

Interventional neuroradiology.

The purpose of this article is to provide an overview of all aspects concerning interventional neuroradiology of vascular central nervous diseases. Today, interventional neuroradiology can help many patients that, even until a few years ago, did not have any possibility for a safe cure. Complex cerebral arteriovenous malformations and fistulas, inoperable aneurysms and intravascular thromboses are often treated with interventional neuroradiology alone, while in other cases a combination of neurosurgery and radiation may help in reaching a good outcome for the patients. In the past few decades the efforts by neuroradiologists and collaborating clinicians to develop treatment strategies and methods for these and other high-risk diseases represent a vast, fascinating field of modern medicine. The article therefore focusses on the state-of-the-art and describes presently used methods for diseases that can be treated with interventional neuroradiology. Literature dealing with the historical development of interventional neuroradiology and important publications of recent scientific work are reviewed, providing the reader with an overview of the most pertinent material on each disease discussed. Aspects of training and ethics are discussed and emphasis is focussed on the importance of recognizing these aspects as essential in any case of interventional radiological treatment.

Bulbar myoclonus without palatal myoclonus. A hypothesis on pathophysiology.

A 40-year-old woman with myoclonic contractions bilaterally in the infrahyoid neck muscles, especially in the left cricothyroid muscle, was presented and successfully treated with botulinum toxin injections. The patient had a wide, aberrant vessel curving into the left dorsolateral reticular formation of the medulla oblongata. Based on our observations, we propose that symptomatic bulbar and palatal myoclonus is caused by pathology in the dorsolateral reticular formation, and not by inferior olivary dysfunction as is currently thought.

[Intraspinal hematoma after thoracic epidural analgesia]. / Intraspinal bløning etter torakal epidural smertebehandling.

In one year three patients were operated on for spinal haematomas following thoracic epidural analgesia. All three patients experienced back pain and developed progressive paraparesis, one in connection with insertion of the catheter and two after its removal. A spinal block was visualized using MRI in two patients and myelography in one. The patients were operated on with posterior decompression. In two patients an epidural haematoma was evacuated. Both patients recovered neurologic function, one completely. The third patient, who had a subarachnoidal hemorrhage and an intramedullar haematoma, remained paralytic.