[Show abstract][Hide abstract] ABSTRACT: Cerebrospinal fluid pressure (CSFP) interacts with intraocular pressure (IOP) and blood pressure to exert a major influence upon the eye, particularly the optic nerve head region. There is increased interest regarding the influence of CSFP upon disorders affecting this region, in particular glaucoma and idiopathic intracranial hypertension. Additionally, a high proportion of astronauts develop features similar to idiopathic intracranial hypertension that persist for years after returning to Earth. The factors that affect the CSFP influence upon the optic nerve and globe are likely to influence the outcome of various ophthalmic disorders.
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Full-text · Article · Apr 2015 · The British journal of ophthalmology
[Show abstract][Hide abstract] ABSTRACT: Retinal venous pulsation detection is a subjective sign, which varies in elevated intracranial pressure, venous obstruction and glaucoma. To date no method can objectively measure and identify pulsating regions.
Using high resolution video-recordings of the optic disk and retina we measured fluctuating light absorption by haemoglobin during pulsation. Pulsation amplitude was calculated from all regions of the retinal image video-frames in a raster pattern. Segmented retinal images were formed by objectively selecting regions with amplitudes above a range of threshold values. These were compared to two observers manually drawing an outline of the pulsating areas while viewing video-clips in order to generate receiver operator characteristics.
216,515 image segments were analysed from 26 eyes in 18 research participants. Using data from each eye, the median area under the receiver operator curve (AU-ROC) was 0.95. With all data analysed together the AU-ROC was 0.89. We defined the ideal threshold amplitude for detection of any pulsating segment being that with maximal sensitivity and specificity. This was 5 units (95% confidence interval 4.3 to 6.0) compared to 12 units before any regions were missed. A multivariate model demonstrated that ideal threshold amplitude increased with increased variation in video-sequence illumination (p = 0.0119), but between the two observers (p = 0.0919) or other variables.
This technique demonstrates accurate identification of retinal vessel pulsating regions with no areas identified manually being missed with the objective technique. The amplitude values are derived objectively and may be a significant advance upon subjective ophthalmodynamometric threshold techniques.
[Show abstract][Hide abstract] ABSTRACT: We describe a rare case of vascularised orbital roof and calvarial erosions with an associated venous malformation. In the absence of infection, malignancy, trauma and eosinophillic granuloma, the closest previously described entity is vanishing bone disease. Computed tomography (CT), MRI, catheter angiography and pathology were all important in the diagnostic workup to enable surgical planning for biopsy and reconstruction. Ongoing CT and MRI follow-up imaging will determine future treatment planning.
No preview · Article · Jun 2014 · Journal of Medical Imaging and Radiation Oncology
[Show abstract][Hide abstract] ABSTRACT: Anterior lumbar surgery for degenerative disc disease (DDD) is a relatively novel technique that can
prevent damage to posterior osseous, muscular and ligamentous spinal elements. This study reports
the outcomes and complications in 286 patients who underwent fusion – with artificial disc implants
or combined fusion and artificial disc implants – by a single-operator neurosurgeon, with up to
24 months of follow-up. The visual analogue scale (VAS), Oswestry Disability Index (ODI), Short Form
36 (SF36) and prospective log of adverse events were used to assess the clinical outcome. Radiographic
assessments of implant position and bony fusion were analysed. Intraoperative and postoperative complications
were also recorded. Irrespective of pre-surgical symptoms (back pain alone or back and leg
pain combined), workers’ compensation status and type of surgical implant, clinically significant
improvements in VAS, ODI and SF36 were primarily observed at 3 and/or 6 month follow-up, and
improvements were maintained at 24 months after surgery. A 94% fusion rate was obtained; the overall
complication was 9.8% which included 3.5% with vascular complications. The anterior lumbar approach
can be used for treating DDD for both back pain and back and leg pain with low complication rates. With
appropriate training, single-operator neurosurgeons can safely perform these surgeries.
[Show abstract][Hide abstract] ABSTRACT: Object:
The goal in this study was to assess the validity of the corticosteroid randomization after significant head injury (CRASH) collaborators prediction model in predicting mortality and unfavorable outcome at 18 months in patients with severe traumatic brain injury (TBI) requiring decompressive craniectomy. In addition, the authors aimed to assess whether this model was well calibrated in predicting outcome across a wide spectrum of severity of TBI requiring decompressive craniectomy.
This prospective observational cohort study included all patients who underwent a decompressive craniectomy following severe TBI at the two major trauma hospitals in Western Australia between 2004 and 2012 and for whom 18-month follow-up data were available. Clinical and radiological data on initial presentation were entered into the Web-based model and the predicted outcome was compared with the observed outcome. In validating the CRASH model, the authors used area under the receiver operating characteristic curve to assess the ability of the CRASH model to differentiate between favorable and unfavorable outcomes.
The ability of the CRASH 6-month unfavorable prediction model to differentiate between unfavorable and favorable outcomes at 18 months after decompressive craniectomy was good (area under the receiver operating characteristic curve 0.85, 95% CI 0.80-0.90). However, the model's calibration was not perfect. The slope and the intercept of the calibration curve were 1.66 (SE 0.21) and -1.11 (SE 0.14), respectively, suggesting that the predicted risks of unfavorable outcomes were not sufficiently extreme or different across different risk strata and were systematically too high (or overly pessimistic), respectively.
The CRASH collaborators prediction model can be used as a surrogate index of injury severity to stratify patients according to injury severity. However, clinical decisions should not be based solely on the predicted risks derived from the model, because the number of patients in each predicted risk stratum was still relatively small and hence the results were relatively imprecise. Notwithstanding these limitations, the model may add to a clinician's ability to have better-informed conversations with colleagues and patients' relatives about prognosis.
No preview · Article · Mar 2014 · Journal of Neurosurgery
[Show abstract][Hide abstract] ABSTRACT: Background: Acute convection-enhanced delivery (CED) is a neurosurgical delivery technique that allows for precise and uniform distribution of an infusate to a brain structure. It remains experimental due to difficulties in ensuring successful delivery. Real-time monitoring is able to provide immediate feedback on cannula placement, infusate distribution, and if the infusion is proceeding as planned or is failing due to reflux or catheter obstruction.
New method: Pressure gradient is the driving force behind CED, with the infusion pressure being directly proportional to the flow-rate. The aim of this study was to assess the feasibility of using infusion-line pressure profiling to distinguish in real-time between succeeding and failing CED infusions. To do so we delivered cresyl violet dye at 0.5, 1.0 and 2.0 μl/min via CED in vitro using 0.6% agarose gel and in vivo to the rat striatum.
Results: Infusions that failed in agarose gel models could only be differentiated late during the procedures. In the rat in vivo model, the infusion-line profiles of obstructed infusions were not distinctive from those of successful infusions.
Comparison with existing method: Intraoperative magnetic resonance imaging (MRI) is used for real-time visualisation of cannula placement and infusate distribution. Particularly for animal pre-clinical work, it would be advantageous to supplement MRI with a cheap, accessible technique to monitor infusions and provide a real-time measure of infusion success or failure.
Conclusions: Infusion-line pressure monitoring was of limited value in identifying successful CED with small volume infusions, whilst its utility for large volume infusion remains unknown.
Full-text · Article · Jan 2014 · Journal of Neuroscience Methods
[Show abstract][Hide abstract] ABSTRACT: The caudal zona incerta is the target of a recent modification of established procedures for deep brain stimulation (DBS) for Parkinson's disease and tremor. The caudal zona incerta contains a number of neuronal populations that are distinct in terms of their cytoarchitecture, connections, and pattern of immunomarkers and is located at a position where a number of major tracts converge before turning toward their final destination in the forebrain. However, it is not clear which of the anatomical features of the region are related to its value as a target for DBS. This paper has tried to identify features that distinguish the caudal zona incerta of rodents (mouse and rat) and primates (marmoset, rhesus monkey, and human) from the remainder of the zona incerta. We studied cytoarchitecture, anatomical relationships, the pattern of immunomarkers, and gene expression in both of these areas. We found that the caudal zona incerta has a number of histological and gene expression characteristics that distinguish it from the other subdivisions of the zona incerta. Of particular note are the sparse population of GABA neurons and the small but distinctive population of calbindin neurons. We hope that a clearer appreciation of the anatomy of the region will in the end assist the interpretation of cases in which DBS is used in human patients.
No preview · Article · Oct 2013 · Journal of Anatomy
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present a method to combine a Gaussian Process regression and a particle filter to track the 3D human pose in video sequences. We first build the probabilistic discriminative model that maps the silhouette descriptor to multiple 3D human poses using a Gaussian Process regression. The multimodal output distribution from the Gaussian Process regression is combined with the particle filter to track the 3D human pose in each frame of the video sequence. The predictions from the discriminative model are used to generate the hypothesis
space for the particle filter and to initialize the tracking. We evaluate our approach on the HumanEva-I dataset and on the video sequences of Parkinson’s patients. The evaluation results show that our approach does not require initialization and successfully tracks the 3D human pose over long video sequences.
[Show abstract][Hide abstract] ABSTRACT: Background:
There has been a resurgence of interest in the use of decompressive craniectomy for severe traumatic brain injury (TBI). Numerous studies have shown that the procedure can consistently reduce intracranial pressure (ICP), and a significant number of patients achieve a good long-term functional recovery. However, there has been debate regarding clinical indications and patient selection.
The DECRA (Decompressive Craniectomy in Patients with Severe Traumatic Brain Injury) study compared patients who underwent early decompressive craniectomy for diffuse TBI with patients who received standard medical therapy. Of patients, 70% in the craniectomy group had an unfavourable outcome versus 51% in the standard care group (odds ratio 2.21 [95% confidence interval 1.14-4.26]; P=0.02). Based on these results, the authors concluded that decompressive craniectomy was associated with more unfavorable outcomes and that by adopting standard medical therapy rather than surgical decompression the health care system would save millions of dollars. These conclusions are not really supported by closer examination of the basic data. There were problems with randomization such that the patients in the surgical arm appeared to have sustained a more severe primary TBI, the ICP threshold of >20 mm Hg for >15 minutes did not reflect clinical practice, and there was a high crossover rate from the standard care arm to the surgical arm. Because of these problems, the DECRA trial has received a great deal of criticism, and some authorities have claimed that the results should have no influence on clinical practice. This claim is perhaps unfair, and an alternative interpretation is offered.
Overall, the results of the DECRA study showed that a relatively transient and mild increase in ICP (>20 mm Hg for 15 minutes as recruitment criterion) does not imply that there is significant ongoing secondary brain injury, and any potential improvement obtained by surgical decompression may well be offset by surgical morbidity.
The role of decompressive craniectomy when ICP continues to increase ≥20 mm Hg remains to be established. The ongoing RESCUEicp (Randomised Evaluation of Surgery with Craniectomy for Uncontrollable Elevation of Intra-Cranial Pressure) study hopes to address this issue.
Full-text · Article · Sep 2012 · World Neurosurgery
[Show abstract][Hide abstract] ABSTRACT: In all fields of clinical medicine, there is an increasing awareness that outcome must be assessed in terms of quality of life and cost effectiveness, rather than merely length of survival. This is especially the case when considering decompressive craniectomy for severe traumatic brain injury. The procedure itself is technically straightforward and involves temporarily removing a large section of the skull vault in order to provide extra space into which the injured brain can expand. A number of studies have demonstrated many patients going on to make a good long-term functional recovery, however, this is not always the case and a significant number survive but are left with severe neurocognitive impairment. Unfortunately, many of these patients are young adults who were previously fit and well and are, therefore, likely to spend many years in a condition that they may feel to be unacceptable, and this raises a number of ethical issues regarding consent and resource allocation. In an attempt to address these issues, we have used the analytical framework proposed by Jonsen, that requires systematic consideration of medical indications, patient preferences, quality of life and contextual features.
Full-text · Article · Jul 2012 · Journal of medical ethics
[Show abstract][Hide abstract] ABSTRACT: As efforts to noninvasively measure intracranial pressure (ICP) increase, we thought it important to investigate the timing of retinal venous pulsation in relation to the intraocular and intracranial pressure pulses.
Neurosurgical patients undergoing continuous direct ICP monitoring had video recordings of ICP, IOP, and retinal venous pulsation waveforms taken with constant timing relative to the cardiac cycle using pulse oximetry. Video frames of the maxima and minima of these parameters, including retinal vein diameter, were identified. The times from pulse oximetry "beep" to these parameters were measured and converted into a percentage of the respective cardiac cycle.
A total of 338 measurements from nine subjects with a mean age of 39 years, mean ICP of 4.4 mm Hg and IOP 15.1 mm Hg were taken. Vein diameter minima occurred an insignificant 0.6% of cardiac cycle before ICP minima (P = 0.6620) and a significant 3.2% after IOP minima (P = 0.0097) and significantly later than IOP (51%) and ICP maxima (74%, all P < 0.0001). Maximum vein diameter occurred an insignificant 2.0% before IOP maxima (P = 0.2267) and was significantly different from IOP and ICP minima (P < 0.00001). Mean venous pulsation pressure between the two eyes was significantly associated with ICP (r = 0.89, P = 0.0075).
During pulsation, central retinal vein collapse occurs in time with IOP and ICP diastole. Venous collapse is not induced by intraocular systole. These results suggest that ICP pulse pressure dominates the timing of venous pulsation.
No preview · Article · Jun 2012 · Investigative ophthalmology & visual science
[Show abstract][Hide abstract] ABSTRACT: The rubber hand illusion (RHI) is a perceptual experience which often occurs when an administered tactile stimulation of a person's real hand hidden from view, occurs synchronously with a corresponding visual stimulation of an observed rubber hand placed in full vision of the person in a position corresponding to where their real hand might normally be. The perceptual illusion is that the person feels a sense of "ownership" of the rubber hand which they are looking at. Most studies have focused on the underlying neural properties of the illusion and the experimental manipulations that lead to it. The illusion could also be used for exploring the sense of limb and prosthetic ownership for people after amputation. Cortical electrodes such as those used in sensorimotor stimulation surgery for pain may provide an opportunity to further understand the cortical representation of the illusion and possibly provide an opportunity to modulate the individual's sense of body ownership. Thus, the RHI might also be a critical tool for development of neurorehabilitative interventions that will be of great interest to the neurosurgical and rehabilitation communities.
No preview · Article · Dec 2011 · Journal of Clinical Neuroscience
[Show abstract][Hide abstract] ABSTRACT: Decompressive craniectomy has been traditionally used as a lifesaving rescue procedure for patients with refractory intracranial hypertension after severe traumatic brain injury (TBI), but its cost-effectiveness remains uncertain.
Using data on length of stay in hospital, rehabilitation facility, procedural costs, and Glasgow Outcome Scale (GOS) up to 18 months after surgery, the average total hospital costs per life-year and quality-adjusted life-year (QALY) were calculated for patients who had decompressive craniectomy for TBI between 2004 and 2010 in Western Australia. The Corticosteroid Randomisation After Significant Head Injury prediction model was used to quantify the severity of TBI.
Of the 168 patients who had 18-month follow-up data available after the procedure, 70 (42%) achieved a good outcome (GOS-5), 27 (16%) had moderate disability (GOS-4), 34 (20%) had severe disability (GOS-3), 5 (3%) were in vegetative state (GOS-2), and 32 (19%) died (GOS-1). The hospital costs increased with the severity of TBI and peaked when the predicted risk of an unfavorable outcome was about 80%. The average cost per life-year gained (US$671,000 per life-year) and QALY (US$682,000 per QALY) increased substantially and became much more than the usual acceptable cost-effective limit (US$100,000 per QALY) when the predicted risk of an unfavorable outcome was >80%. Changing different underlying assumptions of the analysis did not change the results significantly.
Severity of TBI had an important effect on cost-effectiveness of decompressive craniectomy. As a lifesaving procedure, decompressive craniectomy was not cost-effective for patients with extremely severe TBI.
No preview · Article · Dec 2011 · The Journal of trauma