Progression from selective to general involvement of hippocampal subfields in schizophrenia.

Volume deficits of the hippocampus in schizophrenia have been consistently reported. However, the hippocampus is anatomically heterogeneous; it remains unclear whether certain portions of the hippocampus are affected more than others in schizophrenia. In this study, we aimed to determine whether volume deficits in schizophrenia are confined to specific subfields of the hippocampus and to measure the subfield volume trajectories over the course of the illness. Magnetic resonance imaging scans were obtained from Data set 1: 155 patients with schizophrenia (mean duration of illness of 7 years) and 79 healthy controls, and Data set 2: an independent cohort of 46 schizophrenia patients (mean duration of illness of 18 years) and 46 healthy controls. In addition, follow-up scans were collected for a subset of Data set 1. A novel, automated method based on an atlas constructed from ultra-high resolution, post-mortem hippocampal tissue was used to label seven hippocampal subfields. Significant cross-sectional volume deficits in the CA1, but not of the other subfields, were found in the schizophrenia patients of Data set 1. However, diffuse cross-sectional volume deficits across all subfields were found in the more chronic and ill schizophrenia patients of Data set 2. Consistent with this pattern, the longitudinal analysis of Data set 1 revealed progressive illness-related volume loss (~2-6% per year) that extended beyond CA1 to all of the other subfields. This decline in volume correlated with symptomatic worsening. Overall, these findings provide converging evidence for early atrophy of CA1 in schizophrenia, with extension to other hippocampal subfields and accompanying clinical sequelae over time.

Progression of subcortical atrophy in mild Parkinson's disease and its impact on cognition.

BACKGROUND AND PURPOSE: Mild cognitive impairment (MCI) is associated with pronounced grey matter atrophy in various brain regions. However, the association between atrophy patterns and progression from no cognitive impairment (NCI) to Parkinson's disease (PD)-MCI is not clearly known. We investigated the pattern and progression of atrophy in subcortical structures and its impact on cognition in patients with mild PD. METHODS: Sixty-five patients with mild PD with baseline and longitudinal clinical and neuropsychological assessments, and structural magnetic resonance imaging scans were studied. Movement Disorder Society Task Force criteria were used to classify patients with PD into PD-NCI (n = 54) and PD-MCI (n = 11). Based on progression over time, those who remained without cognitive impairment were classified as PD-stable (n = 42) and those who converted to MCI over 18 months were classified as PD-converters (n = 12). FreeSurfer was used to measure cortical thickness and subcortical volumes at baseline and follow-up. RESULTS: Parkinson's disease-MCI showed baseline thalamus atrophy and progressive atrophy in the thalamus, caudate, presubiculum, cornu ammonis 1 and 2-3, and significant memory and executive dysfunction compared with PD-NCI. PD-converters had greater accumbens atrophy at baseline and progressive atrophy in the thalamus, caudate and accumbens with dysfunctions in memory and executive domains. CONCLUSIONS: Progression of cognitive impairment in non-demented PD is associated with a specific pattern of subcortical atrophy. Findings from this study will allow future studies to investigate in the role of subcortical structures as a biomarker for PD dementia.

Post-stroke subjective cognitive impairment is associated with acute lacunar infarcts in the basal ganglia.

BACKGROUND AND PURPOSE: While recent studies have examined neuroimaging correlates of post-stroke mild cognitive impairment (MCI), no studies have examined neuroimaging correlates of post-stroke subjective cognitive impairment (SCI). METHODS: Consecutive patients with magnetic resonance imaging-confirmed acute lacunar strokes at a tertiary institute were recruited for this cross-sectional study. All patients underwent cognitive testing, and those with MCI were excluded from these analyses. Two independent neuroradiologists ascertained data on the number and location of any infarcts, as well as the degree of white matter hyperintensities. Multivariate logistic regression analyses were performed to study the association between neuroimaging markers and SCI. Only variables that were significant in the univariate stage and clinically relevant potential confounders were included in multivariable analyses. RESULTS: Of 145 patients evaluated, 48 patients with MCI were excluded from the study. Of the remaining 97 patients, 30 patients had SCI. In multivariable analyses, only mini-mental state examination (OR 0.61; CI 0.38-0.98) and basal ganglia infarcts (OR 8.19; CI 1.18-56.6) were significant predictors of SCI. CONCLUSION: In patients with acute lacunar strokes, we find that basal ganglia infarcts are associated with SCI. As the basal ganglia have been previously shown to be involved with learning of tasks, we hypothesize that infarcts in basal ganglia may affect learning speeds thereby contributing to the development of SCI. Larger studies are needed to confirm these results.

Surgical planning for microsurgical excision of cerebral arterio-venous malformations using virtual reality technology.

BACKGROUND: To evaluate the feasibility of surgical planning using a virtual reality platform workstation in the treatment of cerebral arterio-venous malformations (AVMs) METHODS: Patient-specific data of multiple imaging modalities were co-registered, fused and displayed as a 3D stereoscopic object on the Dextroscope, a virtual reality surgical planning platform. This system allows for manipulation of 3D data and for the user to evaluate and appreciate the angio-architecture of the nidus with regards to position and spatial relationships of critical feeders and draining veins. We evaluated the ability of the Dextroscope to influence surgical planning by providing a better understanding of the angio-architecture as well as its impact on the surgeon's pre- and intra-operative confidence and ability to tackle these lesions. FINDINGS: Twenty four patients were studied. The mean age was 29.65 years. Following pre-surgical planning on the Dextroscope, 23 patients underwent microsurgical resection after pre-surgical virtual reality planning, during which all had documented complete resection of the AVM. Planning on the virtual reality platform allowed for identification of critical feeders and draining vessels in all patients. The appreciation of the complex patient specific angio-architecture to establish a surgical plan was found to be invaluable in the conduct of the procedure and was found to enhance the surgeon's confidence significantly. CONCLUSION: Surgical planning of resection of an AVM with a virtual reality system allowed detailed and comprehensive analysis of 3D multi-modality imaging data and, in our experience, proved very helpful in establishing a good surgical strategy, enhancing intra-operative spatial orientation and increasing surgeon's confidence.

Classification of gait patterns in the time-frequency domain.

This paper describes the classification of gait patterns among descending stairs, ascending stairs and level walking activities using accelerometers arranged in antero-posterior and vertical direction on the shoulder of a garment. Gait patterns in continuous accelerometer records were classified in two steps. In the first step, direct spatial correlation of discrete dyadic wavelet coefficients was applied to separate the segments of gait patterns in the continuous accelerometer record. Compared to the reference system, averaged absolute error 0.387 s for ascending stairs and 0.404 s for descending stairs were achieved. The overall sensitivity and specificity of ascending stairs were 98.79% and 99.52%, and those of descending stairs were 97.35% and 99.62%. In the second step, powers of wavelet coefficients of 2 s time duration from separated segments of vertical and antero-posterior acceleration signals were used as features in classification. Our results proved a reliable technique of measuring gait patterns during physical activity.

Early experiences with diffusion tensor imaging and magnetic resonance tractography in stroke patients.

INTRODUCTION: Recent advances in magnetic resonance (MR) diffusion tensor imaging technique enable evaluation of the anisotropy of white matter tracts in-vivo, as well as the integrity of fibre tracts and their orientation. We describe our initial experiences with diffusion tensor imaging and MR tractography techniques to evaluate the structural degeneration of white matter tracts following stroke. METHODS: Diffusion tensor imaging data were acquired in 11 cases with stroke on a 3T MR imaging scanner, with three-dimensional diffusion tensor imaging-based colour maps and MR tractography performed offline. We evaluated the spatial relationships of the eloquent white matter tracts to the infarcts and areas of haemorrhage, and classified therewith the tracts as either disrupted or displaced. We compared these with the clinical severity of the neurological deficits and prognosis. RESULTS: A good correlation was found between tractography findings and patient's clinical recovery. All the patients with disruption of white matter tracts had residual deficits on clinical follow-up, whereas the patients with displaced tracts had near complete neurological recovery. CONCLUSION: Diffusion tensor imaging and MR tractography provide a novel and useful method to directly visualise changes in the white matter tracts in stroke. This can potentially allow clinical-imaging correlation with prognostic potential.

A multivariate regression model predicted falls in residents living in intermediate hostel care.

BACKGROUND AND OBJECTIVE: To evaluate whether individual falls risk could be predicted in a frail elderly population. STUDY DESIGN AND SETTING: We developed and tested an assessment tool and falls risk score for predicting falls based on a multivariate regression model in a prospective cohort study of intermediate care residents. RESULTS: During the follow-up period, 1,736 falls by 1,107 subjects were recorded with an average of 170 falls per 100 person-years. Fifty percent of the study population had at least one fall within a year. Significant independent risk factors were poor balance, cognitive impairment, incontinence, higher illness severity rating, and older age. Twenty-two percent of participants with a falls risk score > or =7 accounted for 42% of the total falls, with a falls rate of 317 per 100 person-years. This rate was a sixfold increase from the falls rate of 52 per 100 person-years observed in participants with a score < 3. A high score (> or =7) indicated almost a 2 in 3 chance of falling, while a low score (<3) indicated approximately a 1 in 7 chance of falling within 6 months. CONCLUSION: The assessment tool and falls risk score could identify individuals in this frail elderly population at high risk of falls.

Normal variants of the intracranial circulation demonstrated by MR angiography at 3T.

Magnetic resonance angiography (MRA) at 3T offers increased signal to noise ratio with better background suppression, leading to exquisite depiction of the intracranial circulation. We present a pictorial review of the normal variations and anomalies of the intracranial circulation detected on MRA performed on a high field 3T clinical scanner using parallel imaging techniques. The salient imaging features of these anomalies and normal variations are discussed with relevance to clinical practice.

Reversible splenial lesion in clinically mild encephalitis.

Clinically mild encephalitis with a reversible lesion in the central splenium of the corpus callosum (SCC) is a recently-described clinicoradiological entity. We report a 20-year-old man presenting with fever and a single episode of generalised seizures. Initial magnetic resonance (MR) images showed an ovoid lesion with T1 and T2 signal prolongation, restricted diffusion and decreased apparent diffusion coefficient values in the centre of the SCC, which resolved completely on a repeat MR imaging done three months later. Clinically, the patient had a mild clinical course and made a full recovery. This clinicoradiological entity with an excellent prognosis is elaborated with possible differential diagnoses given. Emphasis is placed on avoiding unnecessary invasive investigation or therapeutic intervention.

Hippocampal involvement in dengue fever.

Flaviviruses are among the most important emerging viruses known to man. Dengue is the most common flavivirus infection in Singapore, and is transmitted between humans by the Aedes mosquito. We report a 25-year-old man with dengue fever complicated by selective hippocampal involvement manifesting as amnesia. This has not been described in the literature previously. Dengue polymerase chain reaction and serology were positive. Magnetic resonance imaging of the brain showed bilateral hippocampal involvement.

The relationship between postoperative complications and outcomes after hip fracture surgery.

INTRODUCTION: We studied the prevalence of postoperative complications in a series of consecutive patients who received surgery for hip fractures in a major public hospital in Singapore. We also studied the predictors for the occurrence of complications and the impact of these complications on patient outcomes. MATERIALS AND METHODS: A retrospective chart review of patients admitted with hip fracture, from March to November 2001, was carried out. Patients were classified as having postoperative complications if they developed any of the following conditions after surgery: dislocation of prosthesis, deep vein thrombosis, postoperative confusion, foot drop, stroke, cardiac arrhythmias or acute myocardial infarctions, urinary retention, urinary tract infection, pneumonia, wound infection and incident pressure sores. RESULTS: Of the 180 patients studied, 60 developed postoperative complications. Significant predictors of complications after logistic regression included being of female gender [odds ratio (OR), 2.79; 95% confidence interval (CI), 1.13 to 6.89] and pre-fracture mobility status (OR for independent ambulators 0.45; 95% CI, 0.23 to 0.87), but not the age of the patients. Postoperative complications significantly affected the length of stay within the acute hospital (beta coefficient, 6.42; 95% CI, 2.55 to 10.29), but were not associated with a decline in mobility status at 3 months post-fracture, eventual discharge destination or readmission within 1 year. CONCLUSION: Postoperative complications are common after surgery for hip fractures and result in significantly longer hospitalisation periods. Significant predictors for such complications include being of female gender and pre-fracture mobility. Age, in itself, does not result in a higher risk of complications and should not preclude older hip fracture patients from surgical management.

Serum parathyroid hormone predicts time to fall independent of vitamin D status in a frail elderly population.

Very frail older people constitute an increasing proportion of ageing populations and often have vitamin D deficiency. Falls are frequent in this population and have usually been associated with vitamin D deficiency. In this prospective study we measured serum 25-hydroxyvitamin D (25OHD), serum PTH, and falls in 637 ambulatory subjects living in institutional aged care facilities (intermediate-care hostels or nursing homes). The study sample comprised 121 men (mean age, 82.1 yr) and 516 women (mean age, 86.7 yr). Two hundred and seventy-four subjects fell one or more times over a mean duration of follow-up of 10.2 months. Vitamin D deficiency, defined as a serum 25OHD level below 39 nmol/liter was present in 73.6%. Baseline serum 25OHD and PTH were significantly associated with falls in univariate analyses. In multivariate analyses that also corrected for balance and health status, PTH remained a significant predictor of falls independent of 25OHD. Serum PTH is a predictor of time to first fall in the frail elderly independent of vitamin D status and measures of general health.

Spermine reduces infarction and neurological deficit following a rat model of middle cerebral artery occlusion: a magnetic resonance imaging study.

The role of nitric oxide (NO) in post-ischemic cerebral infarction has been extensively examined, but few studies have investigated its role on the neurological deficit. In the present study, we investigated the effect of spermine on the temporal evolution of infarct volume, NO production and neurological deficit using magnetic resonance imaging in a model of permanent focal cerebral ischemia in rats. Spermine given at 10 mg/kg 2 h after ischemia reduced the infarct volume by 40% and abolished brain NO production and improved the neurological score 24 h, 48 h and 72 h after ischemia. Spermine also reduced the neurological deficit as evaluated by rotamex, grip strength and neurological severity score tests.

Nipah viral encephalitis or Japanese encephalitis? MR findings in a new zoonotic disease.

BACKGROUND AND PURPOSE: An epidemic of suspected Japanese encephalitis occurred in Malaysia in 1998-1999 among pig farmers. In neighboring Singapore, an outbreak occurred among pig slaughterhouse workers. It was subsequently established that the causative agent in the outbreak was not the Japanese encephalitis virus but a previously unknown Hendra-like paramyxovirus named Nipah virus. METHODS: The brain MR images of eight patients with Nipah virus infection were reviewed. All patients tested negative for acute Japanese encephalitis virus. Seven patients had contrast-enhanced studies and six had diffusion-weighted examinations. RESULTS: All patients had multiple small bilateral foci of T2 prolongation within the subcortical and deep white matter. The periventricular region and corpus callosum were also involved. In addition to white matter disease, five patients had cortical lesions, three had brain stem involvement, and a single thalamic lesion was detected in one patient. All lesions were less than 1 cm in maximum diameter. In five patients, diffusion-weighted images showed increased signal. Four patients had leptomeningeal enhancement and four had enhancement of parenchymal lesions. CONCLUSION: The brain MR findings in patients infected with the newly discovered Nipah paramyxovirus are different from those of patients with Japanese encephalitis. In a zoonotic epidemic, this striking difference in the appearance and distribution of lesions is useful in differentiating these diseases. Diffusion-weighted imaging was advantageous in increasing lesion conspicuity.

Cerebral melioidosis in Singapore: a review of five cases.

A variety of neurological manifestations of infection with Burkholderia pseudomallei have been described including cerebral abscesses, which are a well-recognized form of neurological melioidosis. The optimal antibiotic therapy for this condition has not been defined; however, combinations of intravenous antibiotics are frequently used in the early stages. Five cases of melioidosis involving brain abscesses are described which presented in Singapore over the past 3 years (1997-2000), 4 of which cases had evidence of disseminated infection. Despite profound neurological deficits and low Glasgow Coma Scale scores at presentation in 3 of these cases, all survived after surgical drainage and prolonged courses of intravenous ceftazidime or imipenem, and only 2 of whom had residual neurological impairment. One incidental finding on computed tomography (CT) or magnetic resonance imaging (MRI) scans not described before as an association with cerebral melioidosis was sinusitis in 4 out of the 5 cases.

The limbic system. An overview of the anatomy and its development.

The limbic system has a pivotal role in attention, memory, and the emotions. The limbic lobe comprises four C-shaped arches stretching from the medial surface of the frontal lobe to the temporal pole. The anatomic relationships are elegantly demonstrated by MR imaging. This article provides an overview of the development and complex anatomy of the limbic system.

Anatomy and pathology of the septal region.

Comprising the septal area and the subcortical nuclei, the septal region is gray matter structures with widespread projection systems and different neurotransmitters. Although their function is poorly understood, lesions of the septal nuclei result in a syndrome of hyper-reactivity, amnesia, and hypersexuality. The pathologic processes affecting the septal region are discussed.

The Ottawa Ankle Rules in Asia: validating a clinical decision rule for requesting X-rays in twisting ankle and foot injuries.

This was a study to determine if the Ottawa Ankle Rules (OAR) for requesting x-ray studies in twisting ankle and foot injuries are applicable in our Asian population. Four hundred ninety-four consecutive eligible patients presenting to the emergency department with twisting injuries about the ankle were examined by emergency physicians for clinical criteria requiring ankle and foot x-ray studies according to the OAR. Four hundred eighty-eight of these patients underwent x-ray studies that were interpreted by a radiologist. The sensitivity and specificity of the OAR for predicting the presence of fracture were calculated to be 0.9 and 0.34, respectively. When the rules were modified to cast a wider screening net, sensitivity improved to 0.99. We conclude that the OAR are not applicable to our population because of inadequate sensitivity, but when modified become acceptable and can reduce the number of x-ray studies requested by 28%.

Clinics in diagnostic imaging (58). Chronic cerebral paragonimiasis.

A 36-year-old Korean man presented with a history of epilepsy. MR imaging of the brain revealed multiple conglomerated round nodules that were hypointense on both T1-and-T2 weighted images. These were located at the left temporal and occipital lobes and had surrounding encephalomalacia. CT scan confirmed the presence of large calcified nodules in the corresponding regions. These imaging findings were typical of chronic cerebral paragonimiasis. The clinical, CT and MR features of cerebral paragonimiasis are reviewed.

Spiral computed tomography demonstration of active haemorrhage in blunt abdominal trauma.

In blunt abdominal trauma, patients may still be actively bleeding despite being physiologically stable. Fast computed tomography scanning permits the detection of active haemorrhage by localising the site of extravasation of contrast enhanced blood. Though a specific sign of active bleeding, particularly arterial haemorrhage, it is insensitive to the slow, continuous venous oozing associated with retroperitoneal and pelvic skeletal injuries. However, its presence will have a critical influence on further surgical intervention. The imaging features of this uncommon entity are demonstrated in our case report.