Medical Bionics - Research Publications
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ItemNo Preview AvailableObjective measures of efficacy of Deep Brain Stimulation for treatment of tremor(Frontiers, 2012)Patients with intractable tremor not alleviated by pharmaceutical therapies can be successfully treated using Deep Brain Stimulation of subcortical areas such as the Subthalamic Nucleus (STN). Current DBS devices produce constant-current or constant-voltage biphasic pulse trains and offer a range of pulse rate and pulse duration options as well as different current or voltage levels. The clinical method of setting the parameters by observation is non-ideal, firstly because of the number of possible parameter combinations, and a current lack of knowledge of how the parameters interact with each other, and secondly because subjective clinical observation is prone to observer error and bias. In this study, we aimed to develop an objective method of recording the severity of tremor and to use it to explore the effect on tremor of stimulus parameters. Six patients with Essential Tremor who had been fitted with a DBS device in the Posterior Subthalamic Area (PSA) participated in the study. Tremor was measured by position sensors attached to the arms and wrists while the patient was holding both arms stretched out in front of them and when performing a finger-nose pointing task. Clinical rating of tremor was also performed. Results of the experiments showed that the optimal stimulus parameters were subject specific and the effects of each parameter were non-monotonic, often with a very specific range providing therapeutic benefit (for example, Fig. 1). The objective measures were more sensitive than clinical judgement and show that an objective fitting method could improve benefits in individual patients.
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ItemNo Preview AvailableOptimising speech outcomes in Deep Brain Stimulation for essential tremor(Australasian Cognitive Neuroscience Society (ACNS), 2013)Deep Brain Stimulation (DBS) is rapidly emerging as a safe and effective treatment option for mitigating the effects of tremor. Despite the relative success of DBS for treating tremor, a common and typically unquantified adverse effect of treatment is dysarthria (slurred speech). Current assessment protocols are driven by the qualitative judgements of treating clinicians and lack the sensitivity and objectivity required to make reliable decisions about treatment optimisation. Therefore we aimed to pilot a speech evaluation procedure that would form the basis of an objective clinical DBS optimisation tool for use in patients with tremor. Six patients diagnosed with essential tremor receiving treatment via deep brain stimulation of the posterior sub-thalamic nucleus were recruited. Electrical stimulation parameters (i.e., pulse rate, pulse duration, and current amplitude) were systematically adjusted and speech samples recorded to identify the patient-specific settings required for optimal therapeutic benefit (reduced tremor) with minimal adverse effects (dysarthria). Altered speech production between stimulation parameters was quantified via acoustic analysis. Measures of timing (e.g., speech rate), intonation (e.g., pitch variation) and quality (e.g., noise-to-harmonics ratio) reflected increasing/decreasing levels of dysarthria (see associated figure). Via this protocol we aim to understand the inter-relationship between the effects of the parameters as well as to develop a real-time objective system for surgeons to optimise these parameters for each patient. A secondary outcome is to increase our understanding of how electrical parameter settings are related to movement and speech, and how the optimal parameters are related to the nature of the individual’s pathology.
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ItemNo Preview AvailableIssues in binaural hearing in bilateral cochlear implant users(ASA, 2013-06-19)
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ItemNo Preview AvailableConnectivity in Language Areas of the Brain in Cochlear Implant Users as Revealed by fNIRS(SPRINGER-VERLAG BERLIN, 2016-01-01)Many studies, using a variety of imaging techniques, have shown that deafness induces functional plasticity in the brain of adults with late-onset deafness, and in children changes the way the auditory brain develops. Cross modal plasticity refers to evidence that stimuli of one modality (e.g. vision) activate neural regions devoted to a different modality (e.g. hearing) that are not normally activated by those stimuli. Other studies have shown that multimodal brain networks (such as those involved in language comprehension, and the default mode network) are altered by deafness, as evidenced by changes in patterns of activation or connectivity within the networks. In this paper, we summarise what is already known about brain plasticity due to deafness and propose that functional near-infra-red spectroscopy (fNIRS) is an imaging method that has potential to provide prognostic and diagnostic information for cochlear implant users. Currently, patient history factors account for only 10 % of the variation in post-implantation speech understanding, and very few post-implantation behavioural measures of hearing ability correlate with speech understanding. As a non-invasive, inexpensive and user-friendly imaging method, fNIRS provides an opportunity to study both pre- and post-implantation brain function. Here, we explain the principle of fNIRS measurements and illustrate its use in studying brain network connectivity and function with example data.
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ItemPeripheral electrophysiological measures predict high rate behavioural thresholds of cochlear implant users(Audiology Australia, 2016)