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Publication History View all

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    ABSTRACT: Pain perception can be altered by activity in the periaqueductal gray (PAG). The PAG can decrease the incoming nociceptive signals at the level of the spinal dorsal horn, but it is not clear whether the PAG can also affect the sensory thalamus, ventral posterolateral and ventral posteromedial thalamic nuclei, to modulate pain. However, the PAG and the thalamus have direct connections with each other; so we postulated that the PAG may also modulate pain by inhibiting the sensory nuclei in the thalamus, and that these may also reciprocally influence the PAG. Here, by analyzing the local field potentials recorded from the sensory thalamus and the PAG in chronic pain patients with deep brain stimulation electrodes, we show that PAG stimulation inhibited the sensory thalamus with decreasing thalamic delta, theta, alpha and beta power, and sensory thalamus stimulation excited the PAG with increasing PAG delta and theta power. We demonstrate that the PAG and the sensory thalamus interact reciprocally at short latency, which may be related to pain modulation.
    Experimental Brain Research 11/2013;
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    ABSTRACT: Abstract Background Obtaining renal access is one of the most important and complex steps in learning PCNL. Ideally this skill should be practiced outside the operating room. There is a need for anatomically accurate and cheap models for simulated training. Objective To develop a cost-effective, anatomically accurate, non-biological training model for simulated percutaneous nephrolithotomy (PCNL) access under fluoroscopic guidance. Methods Collecting systems from routine CT urograms were extracted and reformatted using specialised software. These images were printed in a water-soluble plastic on a 3D printer to create bio-models. These models were embedded in silicone and then the models were dissolved in water to leave a hollow collecting system within a silicone model. These PCNL models were filled with contrast medium and sealed. A layer of dense foam acted as a spacer to replicate the tissues between skin and kidney. Results 3D printed models of human collecting systems are a useful adjunct in planning PCNL access. The PCNL access training model is relatively low cost and reproduces the anatomy of the renal collecting system faithfully. A range of models reflecting the variety and complexity of human collecting systems can be reproduced. The fluoroscopic triangulation process required to target the calyx of choice can be practiced successfully in this model. Conclusions This silicone PCNL training model accurately replicates the anatomical architecture and orientation of the human renal collecting system. It provides a safe, clean and effective model for training in accurate fluoroscopic PCNL access.
    Journal of endourology / Endourological Society 10/2013;
  • International Journal of Surgery (London, England) 10/2013;
  • World Neurosurgery 10/2013;
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    ABSTRACT: Provision rates for surgery vary widely in relation to identifiable need, suggesting that reduction of this variation might be appropriate. The definition of unwarranted variation is difficult because the boundaries of acceptable practice are wide, and information about patient preference is lacking. Very little direct research evidence exists on the modification of variations in surgery rates, so inferences must be drawn from research on the alteration of overall rates. The available evidence has large gaps, which suggests that some proposed strategies produce only marginal change. Micro-level interventions target decision making that affects individuals, whereas macro-level interventions target health-care systems with the use of financial, regulatory, or incentivisation strategies. Financial and regulatory changes can have major effects on provision rates, but these effects are often complex and can include unintended adverse effects. The net effects of micro-level strategies (such as improvement of evidence and dissemination of evidence, and support for shared decision making) can be smaller, but better directed. Further research is needed to identify what level of variation in surgery rates is appropriate in a specific context, and how variation can be reduced where desirable.
    The Lancet 09/2013; 382(9898):1130-9.
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    ABSTRACT: Chronic otitis media (OM) is common in Down syndrome (DS), but underlying aetiology is unclear. We analysed the entire available mouse resource of partial trisomy models of DS looking for histological evidence of chronic middle-ear inflammation. We found a highly penetrant OM in the Dp(16)1Yey mouse, which carries a complete trisomy of MMU16. No OM was found in the Dp(17)1Yey mouse or the Dp(10)1Yey mouse, suggesting disease loci are located only on MMU16. The Ts1Cje, Ts1RhR, Ts2Yah, and Ts65Dn trisomies and the transchomosomic Tc1 mouse did not develop OM. On the basis of these findings, we propose a two-locus model for chronic middle-ear inflammation in DS, based upon epistasis of the regions of HSA21 not in trisomy in the Tc1 mouse. We also conclude that environmental factors likely play an important role in disease onset.
    Mammalian Genome 09/2013;
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    ABSTRACT: The periaqueductal/periventricular grey area (PAG/PVG) is a midbrain nucleus with an important role in pain signalling and autonomic control. We present the case of an initially hypertensive man who developed a presumed neurodegenerative disorder over a decade, characterised by progressive right-sided chronic pain, extra-pyramidal symptoms and autonomic dysfunction including postural hypotension, sleep apnoea, and bladder instability. He underwent a variety of treatments for his symptoms, including deep brain stimulation (DBS) of the PAG/PVG. 24-h blood pressure monitoring was carried out 1 and 5 years after implantation. Although the DBS initially produced a significant reduction in blood pressure, the effect was significantly reversed when the same tests were repeated 5 years after surgery. This may imply a functional involvement of the PAG/PVG in the neurodegenerative process.
    Clinical Autonomic Research 06/2013;
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    ABSTRACT: Background: Somatosensory homunculi have been demonstrated in primary somatosensory cortex and ventral posterior thalamus but not periaqueductal and periventricular grey matter (PAVG), a therapeutic target for deep brain stimulation (DBS) in chronic pain. Aims: The study is an investigation of somatotopic representation in PAVG and assessment for a somatosensory homunculus. Methods: Five human subjects were investigated using electrical somatosensory stimulation and deep brain macroelectrode recording. DBS were implanted in the contralateral PAVG. Cutaneous arm, leg and face regions were stimulated while event-related potentials were recorded from deep brain electrodes. Electrode contact positions were mapped using MRI and brain atlas information. Results: Monopolar P1 somatosensory evoked potential amplitudes were highest and onset latencies shortest in contralateral caudal PAVG with facial stimulation and rostral with leg stimulation, in agreement with reported subjective sensation during intra-operative electrode advancement. Conclusions: A rostrocaudally inverted somatosensory homunculus exists in the human PAVG region. Objective human evidence of PAVG somatotopy increases understanding of a brainstem region important to pain and autonomic control that is a clinical target for both pharmacological and neurosurgical therapies. Such knowledge may assist DBS target localisation for neuropathic pain syndromes related to particular body regions like brachial plexopathies, anaesthesia dolorosa and phantom limb pain.
    Stereotactic and Functional Neurosurgery 06/2013; 91(5):290-297.
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    ABSTRACT: Tumour volume (Tv) measurements obtained from pre-treatment CT and MRI have increasingly shown to be more reliable predictors of outcome than TNM stage. The aim of this study was to determine the correlation of MRI calculated maxillary complex tumour volume with patient outcome. METHODS: The medical records of 39 patients with squamous cell carcinoma involving the maxillary sinus, maxilla, hard palate and maxillary alveolus were reviewed and tumour volume measurements completed on pre-treatment MRI. RESULTS: The mean tumour volume was 12.79 ± 24.31 cm(3). Independent samples t test was significant for increasing overall all-cause survival and decreasing tumour volume (1 year: p = 0.003; 5-year: p = 0.031). Cox regression was significant for stratified tumour volume, nodal involvement and peri-neural invasion for predicting disease-free survival. CONCLUSIONS: MRI measured tumour volume assessment appears to be a reliable predictor of survival in patients with maxillary complex SCC treated by surgical resection.
    Journal of cranio-maxillo-facial surgery: official publication of the European Association for Cranio-Maxillo-Facial Surgery 06/2013;
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    ANZ Journal of Surgery 06/2013; 83(6):404-8.
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