W12 Prion disease

Workshops / Clinical Neurophysiology 117 (2006) S25–S31

W10 Motor unit assessment M. Bromberg University of Utah, Neurology, USA Background: Quantitative EMG (QEMG) represents a variety of techniques that extract specific information from the electromyographic signal that can be processed by quantitative and statistical methods. The techniques may be tailored for specific or unique information, and examples include neuromuscular junction transmission (jitter), degree of reinnervation (fiber density), content of the interference pattern (decomposition and turns/amplitude analysis), and number of motor units (motor unit number estimation – MUNE). The motor unit is an important element of the electromyogram, and this talk focuses on techniques to obtain specific and clinically useful information. Aims/objectives: Review technical aspects of QEMG and clinical applications. Methods: Data from normal and subjects with chronic denervating conditions have been obtained from a variety of quantitative EMG techniques. Results: (1) Decomposition EMG: Extraction of individual motor unit action potential (MUAP) waveforms relies on computer algorithms for decomposition of the interference pattern, averaging and waveform marking. There are no standards for algorithm performance and performance varies among algorithms. (2) Optimizing MUAP waveform analysis: routine EMG focuses on assessment of MUAP metrics, including the number of turns. Efforts to extract more MUAP information include reducing the amplitude criterion for counting a turn and increasing the high pass (low frequency) filter. (3) MUNE: MUNE is unique among QEMG techniques in estimating the number of motor units innervating a muscle. There are a variety of MUNE techniques available. Specific information from MUNE in motor neuron disease, spinal muscular atrophy and Charcot-Marie-Tooth neuropathies includes rates of motor unit loss. MUNE also provides information on the capacity for reinnervation. Discussion: Electromyographic signal analysis is greatly aided by signal processing, which in based on computer algorithms. However, caution is warranted in using these approaches to ensure that accurate information is extracted. When issues are understood, useful information can be obtained from simple adjustments to routine EMG studies and unique information from more specific algorithms. doi:10.1016/j.clinph.2006.07.078

W11 Peripheral nerve excitability D. Burke University of Sydney and Royal Prince Alfred Hospital, Institute of Clinical Neurosciences, Australia

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In this workshop we will discuss: (i) the distribution of ion channels in large myelinated axons in human peripheral nerve and their contribution to the action potential and to axonal excitability; (ii) the major determinants of resting membrane potential; (iii) the balance between the tendency to ectopic impulse generation and liability to conduction block; (iv) the differences between large myelinated axons of different modality and between axons of similar modality innervating different regions; (v) the security of impulse conduction in normal axons and how peripheral nerve disease can impair conduction; (vi) how different indices of axonal excitability can be measured rapidly in human subjects; and (vii) findings in different disease states. Participants can expect to gain a better understanding of impulse conduction in normal subjects and disease states and the utility of recently developed techniques for the rapid measurement of different indices of axonal excitability as an add-on to conventional nerve conduction studies. doi:10.1016/j.clinph.2006.07.079

W12 Prion disease R. Will NCJDSU, UK Background: Variant Creutzfeldt-Jakob disease (vCJD) is a zoonosis caused by transmission of bovine spongiform encephalopathy (BSE) to the human population. There have been fears of a major epidemic in the UK and in other European countries. Methods: A national surveillance programme for CJD was established in the UK in 1990 and aims to identify all cases of human prion disease. Data on the mortality rates for vCJD are analysed quarterly. Risk factors for vCJD are identified through observational data and a case-control study. Results: The clinical and investigative features of vCJD have been established and there is evidence of improved diagnosis and case identification with time in the UK. The numbers of deaths and clinical onsets have declined since a peak in 1999/2000, although there remains uncertainty about the future course of the epidemic. Risk factors for vCJD include residence in the UK and methionine homozygosity at codon 129 of the human prion protein gene, although neither of these factors is necessary for disease. A case-control study has shown some evidence of an increased risk through exposure to dietary beef products, the presumed mechanism of transmission of BSE to humans, but no relation with occupation, prior medical and surgical exposures or social class. There is now evidence of secondary transmission of vCJD through blood transfusion and a range of measures has been introduced to minimise the risk of transmission of vCJD through blood or blood products. There is currently no evidence of transmission of vCJD

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Workshops / Clinical Neurophysiology 117 (2006) S25–S31

from person to person either vertically or though exposure to potentially contaminated surgical instruments. Cases of vCJD have been identified in a number of countries outside the UK, including France, Ireland, Italy, the USA, Canada and more recently Japan, Saudi Arabia, the Netherlands, and Spain. Some of these cases were not exposed to BSE through residence in the UK, implying BSE exposure in the country of origin. Discussion: BSE and vCJD have been the subject of intense public concern and have had a major economic impact. The numbers of cases of vCJD are currently limited and are in decline in the UK. However, there is uncertainty about future numbers of cases because of the possibility of susceptible populations with distinct genetic backgrounds and because of secondary transmission. The identification of vCJD in an increasing number of countries is also a cause for concern. doi:10.1016/j.clinph.2006.07.080

W13 Intraoperative monitoring 2: Brain and cranial nerves M. Nuwer UCLA, Department of Neurology, USA When surgery risks injury to the brain or cranial nerves, intraoperative monitoring (IOM) can provide early warning of impending injury. This can provide surgeons an opportunity to intervene and prevent postoperative neurological deficits. Such IOM uses many types of neurophysiologic procedures. EEG and SEP monitor hemisphere function. SEP, MEP, and BAEP monitor brainstem function. EMG and BAEP monitor cranial nerve function. VEPs have not been useful in surgery. Direct electrical stimulation can map cortical structures or identify nerves. Language regions of cortex can be mapped in awake patients during craniotomy. These techniques are applied during tumor resections and other procedures. In carotid endarterectomy, carotid balloon occlusion, and aneurysm clipping, IOM warns of critical ischemia. Those techniques are highly accurate in predicting deficits. Seemingly benign maneuvers, such as surgical cerebellar retraction, can injury critical structures; IOM can warn of such injury. The variety of applications and techniques will be reviewed. doi:10.1016/j.clinph.2006.07.081

W14 Assessment of the urogenital system D.B. Vodusek University Medical Center, Slovenia Background: Neurological patients often have uroanogenital problems which deteriorate their quality of life and

alter prognosis. Assessment allows rational management and needs to clarify the dysfunction, and the neural lesion. Aim: To review diagnostics in neurological patients with uroanogenital problems. Discussion: Assessment requires knowledge of pathophysiology of uroanogenital systems. Dysfunction is partly disclosed by history, clinical exam contributes little; therefore, testing is important. In patients with urinary symptoms postvoid residual urine needs to be determined, further urodynamic or anorectal testing is necessary only in patients with complex dysfunction; videocystourethrography or defecography may be required. Clinical exam provides data on reflex and sensory function of lower sacral segments. Further electrophysiologic testing (concentric needle EMG, sacral reflex studies) contributes particularly in patients with suspected involvement of peripheral reflex arc. Electrophysiological testing is more sensitive to test motor and reflex dysfunction than clinical examination; on the other hand electrophysiological tests are less sensitive in assessment of sensory dysfunction. Tests for autonomic fibre dysfunction are as yet only emerging; for the time being only sympathetic skin responses are accepted as a valid contribution to assessment in selected patients. Conclusion: Assessment focused on symptoms allows management in the majority of neurological patients with uroanogenital dysfunction; only some patients need complex diagnostics. Clarification of the neurological lesion contributes to treatment decisions of uroanogenital dysfunction only in selected patients, but may be relevant for other aspects of patient management. doi:10.1016/j.clinph.2006.07.082

W15 Improved estimation of human cortical activity and connectivity with the multimodal integration of high resolution EEG recordings and hemodynamic data F. Babiloni University of Rome ‘‘La Sapienza’’, Department of Human Physiology and Pharmacology, Italy Background: Nowadays, several types of brain imaging device are available to provide images of the functional activity of the cerebral cortex based on hemodynamic, metabolic, or electromagnetic measurements. However, static images of brain regions activated during particular tasks do not convey the information of how these regions communicate with each other. Objectives: In this study, advanced methods for the estimation of cortical activity and connectivity from combined high-resolution electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data are presented. Methods: Methodological approach includes a subject’s multicompartment head models (scalp, skull, dura mater, cortex) constructed from individual magnetic res-