Redescription of Besnoitia bennetti (Protozoa: Apicomplexa) from the donkey (Equus asinus)

Besnoitia bennetti tissue cysts were found in four naturally-infected donkeys (Equus asinus) from the USA. Infectivity of its bradyzoites and tachyzoites to animals and cell culture was studied. The bradyzoites were not infectious to out-bred Swiss Webster mice, rabbits or gerbils. When fed tissue cysts, cats did not excrete oocysts. However, the parasite was infectious to interferon-gamma gene knock out mice. The parasite from tissues of two donkeys was grown successfully in bovine monocyte monolayers for the first time. Non-dividing, uninucleate tachyzoites were approximately 6 x 1.5 microm in size. Longitudinally-cut bradyzoites in tissue sections measured 8.7 x 1.9 microm. Ultrastructurally, tachyzoites and bradyzoites were similar to those in other Besnoitia species, and in particular to parasites described from cattle (Besnoitia besnoiti) and reindeer (Besnoitia tarandi), in that their bradyzoites lacked enigmatic bodies. Based on comparative analysis of three portions of nuclear ribosomal DNA (the small and large subunits and the first internal transcribed spacer) B. bennetti was found to be more closely related to the other congeners described from ungulates. The parasite was formally redescribed and specimens deposited in the US National Parasite Collections.

Evaluation of an MRI-based protocol for cell implantation in four patients with Huntington's disease

The purpose of this study was to evaluate our surgical protocol for the preparation and delivery of suspensions of fetal tissue into the diseased human brain. We implanted suspensions of human fetal striatal anlage into the right caudate and putamen of four patients with Huntington's disease. Postoperative 3 tesla MR imaging confirmed accurate graft placement. Variability in graft survival was noted and the MR signal changes over 6 months revealed persistent hyperintense signal on T2-weighted images. Our results are consistent with those described by other groups and indicate that our surgical protocol is safe, accurate, and reproducible.

Acute ketamine administration alters the brain responses to executive demands in a verbal working memory task: an FMRI study

We have used functional MRI to determine the effects of ketamine on brain systems activated in association with a working memory task. Healthy volunteers received intravenous infusions of placebo, ketamine at 50 ng/ml plasma concentration, and ketamine at 100 ng/ml. They were scanned while carrying out a verbal working memory task in which we varied the executive requirements (manipulation vs maintenance processes) and the mnemonic load (three vs five presented letters). We previously showed that ketamine produces a specific behavioral impairment in the manipulation task. In the current study, we modified tasks in order to match performance across drug and placebo conditions, and used an event-related fMRI design, allowing us to remove unsuccessful trials from the analysis. Our results suggest a task-specific effect of ketamine on working memory in a brain system comprising frontal cortex, parietal cortex, and putamen. When subjects are required to manipulate presented letters into alphabetical order, as opposed to maintaining them in the order in which they were presented, ketamine is associated with significantly greater activity in this system, even under these performance-matched conditions. No significant effect of ketamine was seen in association with increasing load. This suggests that our findings are not explicable in terms of a nonspecific effect of ketamine when task difficulty is increased. Rather, our findings provide evidence that the predominant effects of low, subdissociative doses of ketamine are upon the control processes engaged by the manipulation task. Furthermore, we have shown that ketamine's effects may be elucidated by fMRI even when overt behavioral measures show no evidence of impairment.

USE OF 18FDG-PET TO DISCRIMINATE BETWEEN INFECTION AND REJECTION IN LUNG TRANSPLANT RECIPIENTS

18F-fluorodeoxyglucose (18FDG) uptake measured by positron emission tomography (PET) allows assessment of neutrophil activity in vivo and is increased in patients with airway inflammation or infection. Because infection but not rejection elicits a highly neutrophilic response, we assessed the ability of this non-invasive technique to differentiate these two events in lung transplant recipients. 18FDG-PET was measured in 15 patients classified by clinical, radiologic, and pathologic criteria. 18FDG-PET signal was increased with proven infection but not when no infection was identified (mean [standard error of mean]: 8.00 [1.81] and 3.16 [0.61], respectively [P = 0.021]. Rejection alone did not increase the signal. These data confirm that neutrophil activation is not a feature of acute rejection and indicate that a high 18FDG-PET signal is indicative of infection but not rejection in lung transplant recipients. This non-invasive and repeatable test could reduce the number of transbronchial biopsies required during episodes of breathlessness after lung transplantation.

Detection or decision errors? Missed lung cancer from the posteroanterior chest radiograph

A test bank of verified chest radiographs was compiled for visual search experiments to investigate radiology performance in the detection of early lung cancer. A measure of the physical characteristics of the lesions was derived to determine the conspicuity (chi) of the nodules and to investigate possible causes of failed detection. Observer performance was measured by alternate free response operating characteristic (AFROC) methodology and was supplemented with visual search recording. Correlation of AFROC scores and the chi values was poor but inspection of the visual search recordings showed that most nodules were fixated. Fixations on missed lesions produced average dwell times greater than three times the minimum duration thought to be associated with detection. We conclude that the majority of errors were failures of decision rather than detection and comment on the implications of this for strategies to improve diagnostic effectiveness.

Stereotactic MR imaging for planning neural transplantation: a reliable technique at 3 Tesla?

The purpose of this study was to assess the accuracy of high field (3 Tesla) MR in target localization for stem cell transplantation. Three patients with Huntington's disease were imaged with a stereotactic frame in place for both MRI and CT. Quality assurance procedures and manual shimming were performed before each MRI study to minimize image distortion. The images were fused using multi-modality rigid body image registration software. Image fusion demonstrated the MR images to be in agreement with CT to within 1.5 mm, as assessed by measuring the coordinates of markers on the frame and on the shape and size of the lateral ventricles. Target coordinates for transplantation were selected from the MR images. Postoperative imaging confirmed accurate graft placement.

Long-term oral sensitivity and feeding skills of low-risk pre-term infants

This study examined the oral sensitivity and feeding skills of low-risk pre-term infants at 11-17 months corrected age. Twenty pre-term infants (PT) born between 32 and 37 weeks at birth without any medical comorbidities were assessed. All of this PT group received supplemental nasogastric (NG) tube feeds during their birth-stay in hospital. A matched control group of 10 healthy full-term infants (FT) was also assessed. Oral sensitivity and feeding skills were assessed during a typical mealtime using the Royal Children's Hospital Oral Sensitivity Checklist (OSC) and the Pre-Speech Assessment Scale (PSAS). Results demonstrated that, at 11-17 months corrected age, the PT group displayed significantly more behaviours suggestive of altered oral sensitivity and facial defensiveness, and a trend of more delayed feeding development than the FT group. Further, results demonstrated that, relative to the FT group, pre-term infants who received greater than 3 weeks of NG feeding (PT>3NG) displayed significantly more facial defensive behaviour, and displayed significant delays across more aspects of their feeding development than pre-term infants who received less than 2 weeks of NG feeding (PT<2NG). The information from this preliminary study suggests that low-risk pre-term infants, particularly those who receive supplemental NG feeding for greater than 3 weeks, may be at risk for displaying long-term altered oral sensitivity and facial defensiveness, as well as feeding delays. These observations warrant further investigation on this topic.

Normal pressure hydrocephalus and cerebral blood flow: a PET study of baseline values

Regional cerebral blood flow (CBF) was studied with O(15)-water positron emission tomography and anatomic region-of-interest analysis on co-registered magnetic resonance in patients with idiopathic (n = 12) and secondary (n = 5) normal pressure hydrocephalus (NPH). Mean CBF was compared with values obtained from healthy volunteers (n = 12) and with clinical parameters. Mean CBF was significantly decreased in the cerebrum and cerebellum of patients with NPH. The regional analysis demonstrated that CBF was reduced in the basal ganglia and the thalamus but not in white matter regions. The results suggest that the role of the basal ganglia and thalamus in NPH may be more prominent than currently appreciated. The implications for theories regarding the pathogenesis of NPH are discussed.

Using simulated patients in a multiprofessional communications skills programme: reflections from the programme facilitators

This paper discusses a multiprofessional, 4-day communication skills programme in which participants explore the challenges of communicating with cancer patients and their families. Effective communication and skilled emotional support are essential prerequisites for high quality care in oncology and palliative care settings. This aspect of care presents major challenges to nurses and other health care professionals. It is acknowledged that health professionals often lack the requisite skills to communicate meaningfully with this patient group and that tangible benefits accrue from training in this area. Using simulated patients, structured feedback and small group discussions, this multiprofessional programme seeks to provide a forum that enables participants to acquire confidence and competence in a safe, comfortable and non-threatening environment. The programme structure presents several challenges in terms of providing a learning experience that addresses the diverse educational of a heterogeneous learning group. Participants' comments and programme facilitators reflections suggest that the programme is successful in addressing these challenges and providing a meaningful learning experience.

Cerebrovascular pressure reactivity is related to global cerebral oxygen metabolism after head injury

BACKGROUND

After head injury, impaired cerebrovascular autoregulation has been associated with abnormally high or low cerebral blood flow. The physiological relevance of cerebral blood flow levels is difficult to assess in these patients, whose cerebral metabolic rate for oxygen (CMRO(2)) is known to be abnormal. Investigation of these relations requires quantitative measures of cerebral blood flow and CMRO(2), to allow assessment of oxygen supply and demand relations.

OBJECTIVES

To investigate the relation between dysautoregulation and global cerebral oxygen metabolism following head injury.

METHODS

Using positron emission tomography, global cerebral blood flow, CMRO(2), and oxygen extraction fraction were determined in 22 patients who were investigated in 26 examinations on days 1 to 11 (mean (SD), 3.5 (2.3)) after head injury. Cerebrovascular pressure reactivity was assessed using a pressure reactivity index, calculated as the moving linear correlation coefficient between mean arterial blood pressure and intracranial pressure. Outcome was assessed six months after injury using the Glasgow outcome scale.

RESULTS

Low CMRO(2) was associated with disturbed pressure reactivity (inverse function, R(2) = 0.21, p = 0.018) and there was a correlation between disturbed pressure reactivity and oxygen extraction fraction (quadratic function, R(2) = 0.55, p = 0.0001). There was no significant relation between pressure reactivity and cerebral blood flow. An unfavourable outcome was associated with disturbed pressure reactivity. There was no significant relation between outcome and CMRO(2) or oxygen extraction fraction.

CONCLUSIONS

There is a close relation between dysautoregulation and abnormal cerebral metabolism but not blood flow. Further studies are needed to determine whether metabolic dysfunction is a result of or a cause of disturbed pressure reactivity, and to establish if there is a relation between cerebral oxygen metabolism and outcome.

Diffusion tensor imaging of brain tumours at 3T: a potential tool for assessing white matter tract invasion?

AIM

To determine whether diffusion tensor imaging (DTI) of brain tumours can demonstrate abnormalities distal to hyperintensities on T2-weighted images, and possibly relate these to tumour grade.

MATERIALS AND METHODS

Twenty patients with histologically confirmed supratentorial tumours, both gliomas (high and low grade) and metastases, were imaged at 3T using T2-weighted and DTI sequences. Regions of interest (ROI) were drawn within the tumour, in white matter at various distances from the tumour and in areas of abnormality on DTI that appeared normal on T2-weighted images. The relative anisotropy index (RAI)-a measure of white matter organization, was calculated for these ROI.

RESULTS

The abnormality on DTI was larger than that seen on T2-weighted images in 10/13 patients (77%) with high-grade gliomas. New abnormalities were seen in the contralateral white matter in 4/13 (30%) of these cases. In these high-grade tumours the RAI in areas of white matter disruption with normal appearance on T2-weighted images was reduced (0.19+/-0.04). Even excluding patients with previous radiotherapy this difference remains significant. In all non high-grade tumours (WHO grade II gliomas and metastases) the tumour extent on DTI was identical to the abnormalities shown on T2-weighted imaging and RAI measurements were not reduced (0.3+/-0.04).

CONCLUSIONS

Subtle white matter disruption can be identified using DTI in patients with high-grade gliomas. Such disruption is not identified in association with metastases or low-grade gliomas despite these tumours producing significant mass effect and oedema. We suggest the changes in DTI may be due to tumour infiltration and that the DTI may provide a useful method of detecting occult white matter invasion by gliomas.

The sacroiliac joints: evaluation using nuclear scintigraphy. Part 1: The normal horse

REASONS FOR PERFORMING STUDY

Sacroiliac (SI) disease is recognised as a cause of poor hindlimb action but differential diagnosis is often difficult.

HYPOTHESES

That in clinically normal horses there would be a significant difference in the ratio of radiopharmaceutical uptake (RU) between the fifth lumbar vertebra (L5) and each tuber sacrale (TS) and between L5 and each SI joint; and that these ratios would alter with age, but ratios would be bilaterally symmetrical.

METHODS

Dorsal scintigraphic images of the SI region of 15 horses, selected randomly from the clinic database, were analysed by 2 of the authors, comparing noncorrected and motion-corrected images. To determine scintigraphic anatomy, the scintigraphic images of 10 Thoroughbred horses were superimposed over a ventrodorsal radiographic image of an isolated pelvis. Dorsal scintigraphic images of 40 clinically normal horses age 3-16 years were evaluated using subjective examination, profile analysis and quantification using regions of interest.

RESULTS

The tubera sacrale were seen as 2 well-defined oval regions immediately to the left and right of the midline, abaxial to which were larger, approximately oval areas with less RU, representing uptake in the SI joints. The definition between the SI region and the TS was more obvious in younger horses. Nonmotion-corrected images were often not of diagnostic quality or could be misinterpreted as abnormal. There were significant differences in RU between the TS and SI joints compared to L5, and decreased RU in the tubera sacrale with increasing age, but no change of uptake in the SI joint region and no effect of gender on RU. There was a high degree of left-right symmetry of the TS and SI joint regions.

CONCLUSIONS AND POTENTIAL RELEVANCE

The scintigraphic images of horses with suspected sacroiliac joint disease should be compared with images of normal horses of comparable age. In normal horses, there was a high degree of symmetry; therefore, marked left-right asymmetry is likely to be abnormal.

Assessment of the Ventrix parenchymal intracranial pressure monitoring probe (NL950-P) and Monitor (NL950-100) in a 3 Tesla magnetic resonance scanner

Magnetic resonance (MR) imaging and spectroscopy provide important information in patients with acute head injury. However, optimal patient management requires intracranial pressure (ICP) monitoring. There are few reports on the use of ICP sensors in an MR environment. We tested the Ventrix parenchymal intracranial pressure monitoring probe and monitor (Integra Neurosciences, USA), modified by the use of a fibre-optic extension cable, within a 3 Tesla MR system. The device performed well in the MR environment, but one element within the fibre-optic extension was significantly ferromagnetic. The ICP probe produced a small susceptibility artefact on spin echo images, and a larger artefact on gradient echo images. The MR safety of the integrated system is probably acceptable, but could be easily improved with minor modifications. Although the system is MR compatible and produces generally acceptable imaging even at 3 Tesla, there is significant degradation of image quality during gradient echo sequences.

A resurgence of congenital rubella in Australia?

Two infants with congenital rubella defects (congenital rubella syndrome) have been reported from Queensland in 2003, after an increase in rubella in that State in 2001-2002. The national Measles Control Campaign in 1998 aimed to give measles-mumps-rubella (MMR) vaccine to all unvaccinated preschoolers and a second dose to primary schoolchildren. Following the Campaign no children with congenital rubella defects were born to Australian-born mothers during the five years 1998 to 2002, according to reports to the Australian Paediatric Surveillance Unit. However, three imported cases occurred. Broad immunisation coverage and detection and vaccination of susceptible women of child-bearing age before they become pregnant are necessary to prevent further cases.

Effect of hyperventilation on cerebral blood flow in traumatic head injury: clinical relevance and monitoring correlates

OBJECTIVE

To investigate the effect of hyperventilation on cerebral blood flow in traumatic brain injury.

DESIGN

A prospective interventional study.

SETTING

A specialist neurocritical care unit.

PATIENTS

Fourteen healthy volunteers and 33 patients within 7 days of closed head injury.

INTERVENTIONS

All subjects underwent positron emission tomography imaging of cerebral blood flow. In patients, PaCO2 was reduced from 36 +/- 1 to 29 +/- 1 torr (4.8 +/- 0.1 to 3.9 +/- 0.1 kPa) and measurements repeated. Jugular venous saturation (SjvO2 ) and arteriovenous oxygen content differences (AVDO2 ) were monitored in 25 patients and values related to positron emission tomography variables.

MEASUREMENTS AND MAIN RESULTS

The volumes of critically hypoperfused and hyperperfused brain (HypoBV and HyperBV, in milliliters) were calculated based on thresholds of 10 and 55 mL.100g(-1).min(-1), respectively. Whereas baseline HypoBV was significantly higher in patients ( p<.05), baseline HyperBV was similar to values in healthy volunteers. Hyperventilation resulted in increases in cerebral perfusion pressure (p <.0001) and reductions in intracranial pressure (p <.001), whereas SjvO2 (>50%) and AVDO2 (<9 mL/mL) did not exceed global ischemic thresholds. However, despite these beneficial effects, hyperventilation shifted the cerebral blood flow distribution curve toward the hypoperfused range, with a decrease in global cerebral blood flow (31 +/- 1 to 23 +/- 1 mL.100g(-1).min(-1); p<.0001) and an increase in HypoBV (22 [1-141] to 51 [2-428] mL; p<.0001). Hyperventilation-induced increases in HypoBV were apparently nonlinear, with a threshold value between 34 and 38 torr (4.5-5 kPa).

CONCLUSIONS

Hyperventilation increases the volume of severely hypoperfused tissue within the injured brain, despite improvements in cerebral perfusion pressure and intracranial pressure. Significant hyperperfusion is uncommon, even at a time when conventional clinical management includes a role for modest hyperventilation. These reductions in regional cerebral perfusion are not associated with ischemia, as defined by global monitors of oxygenation, but may represent regions of potentially ischemic brain tissue.

Assessment of the Caradyne WhisperFlow for administration of continuous positive airway pressure in a 3 Tesla magnetic resonance scanner

Demand for magnetic resonance investigations in critically ill patients is increasing. While these patients frequently need ventilatory support, not all of them require controlled ventilation and many may be treated with continuous positive airway pressure. Controlled ventilation, with the concurrent need for sedation, may be inappropriate when airway physiology is being studied and may retard weaning. No commercially available ventilator designed for the magnetic resonance environment can deliver high flow continuous positive airway pressure. We tested the Caradyne Whisperflow flow generator and five Whisperflow valves (2.5-15 cmH2O airway pressure) within a 3 Tesla environment for safety and possible dysfunction. All components had minimal ferromagnetic properties and tests showed no clinically relevant change in flow delivery or oxygen concentration in the magnetic field. In addition, the airway pressure generated by the valves was not affected by the magnetic field. We conclude that the tested system can be safely used in a 3 Tesla magnetic resonance environment.

Cerebral autoregulation among patients with symptoms of hydrocephalus

OBJECTIVE

To study the relationship between the resistance to cerebrospinal fluid (CSF) outflow and cerebral autoregulation.

METHODS

We examined 35 patients who presented with ventricular dilation and clinical symptoms of communicating hydrocephalus. For all of these patients, CSF compensatory reserve was investigated by using a computerized infusion test, with simultaneous recording of blood flow velocity wave forms (by using transcranial Doppler ultrasonography) and arterial blood pressure (with a Finapress finger cuff). The resistance to CSF outflow was calculated as the absolute increase in intracranial pressure (interpolated over vasogenic waves) divided by the infusion rate (1.5 ml/min in most cases). The index of autoregulation was assessed as a correlation coefficient (moving time window of 5 min) between slow waves (with periods of 20 s to 2 min) in mean blood flow velocity and cerebral perfusion pressure.

RESULTS

The mean intracranial pressure increased during the test, from 6 mm Hg (standard deviation, 6 mm Hg) to 20 mm Hg (standard deviation, 10 mm Hg) (P < 0.0001). The index of autoregulation was significantly correlated with the resistance to CSF outflow (r = -0.41, P < 0.03), indicating better autoregulation with greater resistance to CSF outflow.

CONCLUSION

Patients presenting with ventricular dilation may exhibit either decreased (atrophy) or increased (normal-pressure hydrocephalus) resistance to CSF outflow. Increased resistance is correlated with preserved autoregulation. Patients with low resistance, suggesting brain atrophy, more often have disturbed autoregulation in the middle cerebral artery territory, as assessed by transcranial Doppler ultrasonography.

Responses of human frontal cortex to surprising events are predicted by formal associative learning theory

Learning depends on surprise and is not engendered by predictable occurrences. In this functional magnetic resonance imaging (fMRI) study of causal associative learning, we show that dorsolateral prefrontal cortex (DLPFC) is associated specifically with the adjustment of inferential learning on the basis of unpredictability. At the outset, when all associations were unpredictable, DLPFC activation was maximal. This response attenuated with learning but, subsequently, activation here was evoked by surprise violations of the learned association. Furthermore, the magnitude of DLPFC response to a surprise event was sensitive to the relationship that had been learned and was predictive of subsequent behavioral change. In short, the physiological response properties of right DLPFC satisfied specific predictions made by associative learning theory.

Age dependence of cerebrospinal pressure-volume compensation in patients with hydrocephalus

OBJECT

The dynamics of both drainage and storage capacity become altered during the sequential pathological processes that lead to hydrocephalus. Cerebrospinal fluid (CSF) formation and drainage rate have been reported to be age dependent. The aim of this study was to investigate whether CSF compensatory parameters are dependent on age in patients who have symptoms of hydrocephalus and apparently normal intracranial pressure (ICP).

METHODS

Forty-six patients who presented with ventriculomegaly, the clinical symptoms of hydrocephalus, and normal ICPs underwent a computerized CSF infusion test. Parameters used to describe CSF compensation were calculated and correlated with the age of each patient. The mean ICPs were found to be independent of the age of the patient. Resistance to CSF outflow (Rcsf), however, demonstrated a nonlinear increase with advancing age (r = -0.57; p < 0.0001) and was associated with a decrease in the CSF production rate, which also occurred with increasing age (r = 0.49; p < 0.002). Both the pulse amplitude of the ICP waveform and the slope of the amplitude-ICP regression line increased significantly with advancing age (r = 0.39; p < 0.01 and r = 0.43, p < 0.004, respectively). The nonlinear increase in the elastance coefficient indicated increasing brain stiffness, which acompanies older ages (r = -0.31; p < 0.04).

CONCLUSIONS

In a study of patients with symptoms of hydrocephalus, but normal ICPs, the increase in Rcsf and decrease in CSF production were most pronounced in patients who were older than 56 years of age. This relationship was more significant than previously suggested.