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Immune-mediated neuropathies: immunotherapy and its monitoring
Society proceedings 9.
Immune-mediated neuropathies: immunotherapy and its monitoring. - L. Kiers (Department of Neurology, Royal Melbourne Hospital, Parkville, Victoria)
Immune-mediated damage to neural tissue involves both cellular and humoral immune responses and can target myelin, axons and cell bodies. The majority of immune-mediated neuropathies are acquired, inflammatory, demyelinating neuropathies. A variety of antibodies directed against components of neural tissue have been identified, but their pathogenic role remains uncertain. Identification of specific immune polyneuropathy syndromes, with the aid of electrophysiology and measurement of specific serum antibodies, provides guidance regarding immunosuppressive regimens that may be effective treatments. Specific indications exist for the use of plasma exchange, intravenous gammaglobulin, azathioprine, cyclophosphamide, cyclosporin A and corticosteroids. Objective, quantitative measures of therapeutic response are of prime importance, particularly for clinical trials. Clinical rating scales, myometry, nerve conduction studies, quantitative sensory testing and autonomic function tests provide a means for evaluating small and large motor and sensory nerve fibres. In future, it may be necessary to define patients on the basis of immunopathological in addition to clinical and electrophysiological criteria, in order to best select appropriate. immunotherapy.
10.
Facilitatory effect of thinking about movement on magnetic motor-evoked potentials. - L. Kiers, B. Fernando, D. Tomkins (Departments of Neurology and Clinical Neurophysiology, Royal Melbourne Hospital, Victoria)
To investigate the facilitatory effect of thinking about movement on motor evoked potential (MEP) amplitude we recorded MEPs in two test muscles during rest, with the subject thinking about contracting the test muscle but without subsequent contraction, and during 10% maximum voluntary contraction. Stimuli were delivered at 10% above resting motor threshold and at 90-100% stimulator output. H-reflexes, recorded in flexor carpi radialis, were obtained during rest and think conditions. MEP threshold was lower during the think condition (P = 0.004). At both stimulus intensities, median MEP amplitudes were significantly (P c 0.001) larg$r during the think paradigm compared with rest. This effect was greater at the lower stimulus intensity. There was no significant difference in latency (P = 0.15). In 4/8 subjects, Hreflex amplitudes were facilitated (P < 0.05) during the think condition. We conclude that thinking about movement without detectable EMG activity has a facilitatory effect on magnetic MEPs. The absence of a MEP latency shift between rest and think conditions and absence of a consistent increase in H-reflex amplitude suggests this effect occurs largely at the cortical level. In some subjects, however, an increase in spinal motoneuron excitability may also contribute.
11.
‘Beyond averaging’ of conventional ERPs in Parkinson’s disease. - J. Lagopoulos*, J.G.L. Morrisa, P. Cloustot?‘, C.L. Lima, W. Reida, F. Barbera, H. Bahramalib, E. Gordonb (aDepartment of Neurology, bCognitive Neuroscience Unit, Westmead Hospital, Sydney, NSW)
Most previous late component event related potential (ERP) studies in Parkinson’s disease (PD) have used the conventional average ERP measure and have focused on abnormalities of the P300 component. In the first stage of this study, we examined late component ERPs (NlOO, P200, N200 and P300) in 10 PD patients and 50 normal controls. A significant decrease in N200 amplitude (but not P300) was found in the PD group. However, the focus of our research into PD is to extend such conventional averaging. We present simultaneously recorded data of ‘orienting reflex’ (as measured by skin conductance response or SCR). ERPs and reaction time. We report on a quantitative model that allows examination of ERPs that were associated with an SCR versus ERPs which did not generate an SCR (Lim et al., 1996). The delineation of
61P
these sub-averaged ERPs, with and without orienting reflexes (SCRs), is presented in 50 normals. This template of data allows a physiological reflection of ‘automatic’ orienting (ERPs with SCR) and ‘controlled’ information processing (ERPs without SCR) from conventional averaged ERP data, in PD and normal controls.
12. A novel quantitative model of skin conductance response. C.L. Lima, C. Remdeb, J.G.L. Morrisa, P. Cloustona, H. Bahramalib, W.M. Leeb, E. Gordonb (BDepartment of Neurology, bCognitive Neuroscience Unit, Westmead Hospital, Sydney, NSW) Skin conductance response (SCR) is commonly used as a measure of autonomic nervous system function, because of its excellent signalto-noise ratio and ease of recording. Scoring SCR has often proved to be difficult for 3 reasons: it is superimposed on a tonic skin conductance level (SCL), consecutive responses tend to overlap, and it is sometimes contaminated by a non-specific response. Previous methods have been unable to resolve these problems. We have developed a quantitative 4-parameter mathematical model for SCR and also a method of decomposing the skin conductance into SCL, SCR(s) and the residual decline from the previous response. Our software implementation of the method enables precise scoring of these SCR parameters, including gain (g), rise time, decay time constant (rd), SCR onset latency, peak latency, peak amplitude and other derived variables. The method has been used successfully to score more than 1500 detectable responses behveen 1 and 3 s following 40 target tones presented pseudo-randomly to 50 normal adult subjects and also to 10 patients with Parkinson’s disease (PD). Compared with the normal group, the PD patients showed a significantly larger g (P < 0.05) and a smaller td (P < 0.07) which approached significance. 13.
Electrodiagnosis of thoracic outlet syndrome. - R.A.L. Macdonell (Department of Neurology, Austin and Repatriation Medical Centre, Heidelberg, Victoria)
Neurogenic thoracic outlet syndrome (TOS) can be a controversial diagnosis. Conventional median and ulnar nerve conduction studies and EMG can show evidence of neurological disturbance but the frequency of abnormalities in these tests is low compared with the number of patients referred for electrodiagnosis with a provisional diagnosis of TOS. A case is presented to illustrate that less commonly studied nerves should be used to aid the diagnosis. A 16 year old girl presented complaining of pain and numbness along the medial border of the left forearm. Median and ulnar nerve conduction studies and needle EMG in the arm were normal. The only abnormality was an absent sensory nerve action potential (SNAP) from the medial antebrachial cutaneous nerve. A chest X-ray demonstrated bilateral cervical ribs. The patient was restudied 12 months later because of persisting symptoms. On this occasion, there was wasting and evidence of active denervation in the intrinsic muscles of the left hand and a marked reduction in the ulnar SNAP amplitude compared with the previous study. The patient was referred for surgery. The medial cord of the brachial plexus is the most commonly compromised structure in neurogenic TOS. Evaluation of all its branches should be used in the electrodiagnosis of this condition. 14.
evoked potentials and the site of cerebral ischaemia. - R.A.L. Macdonell, G.A. Donnan, P.F. Bladin (Department of Neurology, Austin and Repatriation Medical Centre, Heidelberg, Victoria)
Somatosensory
Somatosensory evoked potentials (SEPs) were performed in 79 patients after acute cerebral infarction confirmed on CT scan. Infarcts were subdivided into those involving the cerebral cortex on CT (cortical infarcts) and those restricted to the subcortex (subcortical infarcts). SEPs were absent on the side of infarction in 29% of cortical and 27% subcortical infarcts. Cortical infarction was accompanied by
Immune-mediated neuropathies: immunotherapy and its monitoring. - L. Kiers (Department of Neurology, Royal Melbourne Hospital, Parkville, Victoria)
Immune-mediated damage to neural tissue involves both cellular and humoral immune responses and can target myelin, axons and cell bodies. The majority of immune-mediated neuropathies are acquired, inflammatory, demyelinating neuropathies. A variety of antibodies directed against components of neural tissue have been identified, but their pathogenic role remains uncertain. Identification of specific immune polyneuropathy syndromes, with the aid of electrophysiology and measurement of specific serum antibodies, provides guidance regarding immunosuppressive regimens that may be effective treatments. Specific indications exist for the use of plasma exchange, intravenous gammaglobulin, azathioprine, cyclophosphamide, cyclosporin A and corticosteroids. Objective, quantitative measures of therapeutic response are of prime importance, particularly for clinical trials. Clinical rating scales, myometry, nerve conduction studies, quantitative sensory testing and autonomic function tests provide a means for evaluating small and large motor and sensory nerve fibres. In future, it may be necessary to define patients on the basis of immunopathological in addition to clinical and electrophysiological criteria, in order to best select appropriate. immunotherapy.
10.
Facilitatory effect of thinking about movement on magnetic motor-evoked potentials. - L. Kiers, B. Fernando, D. Tomkins (Departments of Neurology and Clinical Neurophysiology, Royal Melbourne Hospital, Victoria)
To investigate the facilitatory effect of thinking about movement on motor evoked potential (MEP) amplitude we recorded MEPs in two test muscles during rest, with the subject thinking about contracting the test muscle but without subsequent contraction, and during 10% maximum voluntary contraction. Stimuli were delivered at 10% above resting motor threshold and at 90-100% stimulator output. H-reflexes, recorded in flexor carpi radialis, were obtained during rest and think conditions. MEP threshold was lower during the think condition (P = 0.004). At both stimulus intensities, median MEP amplitudes were significantly (P c 0.001) larg$r during the think paradigm compared with rest. This effect was greater at the lower stimulus intensity. There was no significant difference in latency (P = 0.15). In 4/8 subjects, Hreflex amplitudes were facilitated (P < 0.05) during the think condition. We conclude that thinking about movement without detectable EMG activity has a facilitatory effect on magnetic MEPs. The absence of a MEP latency shift between rest and think conditions and absence of a consistent increase in H-reflex amplitude suggests this effect occurs largely at the cortical level. In some subjects, however, an increase in spinal motoneuron excitability may also contribute.
11.
‘Beyond averaging’ of conventional ERPs in Parkinson’s disease. - J. Lagopoulos*, J.G.L. Morrisa, P. Cloustot?‘, C.L. Lima, W. Reida, F. Barbera, H. Bahramalib, E. Gordonb (aDepartment of Neurology, bCognitive Neuroscience Unit, Westmead Hospital, Sydney, NSW)
Most previous late component event related potential (ERP) studies in Parkinson’s disease (PD) have used the conventional average ERP measure and have focused on abnormalities of the P300 component. In the first stage of this study, we examined late component ERPs (NlOO, P200, N200 and P300) in 10 PD patients and 50 normal controls. A significant decrease in N200 amplitude (but not P300) was found in the PD group. However, the focus of our research into PD is to extend such conventional averaging. We present simultaneously recorded data of ‘orienting reflex’ (as measured by skin conductance response or SCR). ERPs and reaction time. We report on a quantitative model that allows examination of ERPs that were associated with an SCR versus ERPs which did not generate an SCR (Lim et al., 1996). The delineation of
61P
these sub-averaged ERPs, with and without orienting reflexes (SCRs), is presented in 50 normals. This template of data allows a physiological reflection of ‘automatic’ orienting (ERPs with SCR) and ‘controlled’ information processing (ERPs without SCR) from conventional averaged ERP data, in PD and normal controls.
12. A novel quantitative model of skin conductance response. C.L. Lima, C. Remdeb, J.G.L. Morrisa, P. Cloustona, H. Bahramalib, W.M. Leeb, E. Gordonb (BDepartment of Neurology, bCognitive Neuroscience Unit, Westmead Hospital, Sydney, NSW) Skin conductance response (SCR) is commonly used as a measure of autonomic nervous system function, because of its excellent signalto-noise ratio and ease of recording. Scoring SCR has often proved to be difficult for 3 reasons: it is superimposed on a tonic skin conductance level (SCL), consecutive responses tend to overlap, and it is sometimes contaminated by a non-specific response. Previous methods have been unable to resolve these problems. We have developed a quantitative 4-parameter mathematical model for SCR and also a method of decomposing the skin conductance into SCL, SCR(s) and the residual decline from the previous response. Our software implementation of the method enables precise scoring of these SCR parameters, including gain (g), rise time, decay time constant (rd), SCR onset latency, peak latency, peak amplitude and other derived variables. The method has been used successfully to score more than 1500 detectable responses behveen 1 and 3 s following 40 target tones presented pseudo-randomly to 50 normal adult subjects and also to 10 patients with Parkinson’s disease (PD). Compared with the normal group, the PD patients showed a significantly larger g (P < 0.05) and a smaller td (P < 0.07) which approached significance. 13.
Electrodiagnosis of thoracic outlet syndrome. - R.A.L. Macdonell (Department of Neurology, Austin and Repatriation Medical Centre, Heidelberg, Victoria)
Neurogenic thoracic outlet syndrome (TOS) can be a controversial diagnosis. Conventional median and ulnar nerve conduction studies and EMG can show evidence of neurological disturbance but the frequency of abnormalities in these tests is low compared with the number of patients referred for electrodiagnosis with a provisional diagnosis of TOS. A case is presented to illustrate that less commonly studied nerves should be used to aid the diagnosis. A 16 year old girl presented complaining of pain and numbness along the medial border of the left forearm. Median and ulnar nerve conduction studies and needle EMG in the arm were normal. The only abnormality was an absent sensory nerve action potential (SNAP) from the medial antebrachial cutaneous nerve. A chest X-ray demonstrated bilateral cervical ribs. The patient was restudied 12 months later because of persisting symptoms. On this occasion, there was wasting and evidence of active denervation in the intrinsic muscles of the left hand and a marked reduction in the ulnar SNAP amplitude compared with the previous study. The patient was referred for surgery. The medial cord of the brachial plexus is the most commonly compromised structure in neurogenic TOS. Evaluation of all its branches should be used in the electrodiagnosis of this condition. 14.
evoked potentials and the site of cerebral ischaemia. - R.A.L. Macdonell, G.A. Donnan, P.F. Bladin (Department of Neurology, Austin and Repatriation Medical Centre, Heidelberg, Victoria)
Somatosensory
Somatosensory evoked potentials (SEPs) were performed in 79 patients after acute cerebral infarction confirmed on CT scan. Infarcts were subdivided into those involving the cerebral cortex on CT (cortical infarcts) and those restricted to the subcortex (subcortical infarcts). SEPs were absent on the side of infarction in 29% of cortical and 27% subcortical infarcts. Cortical infarction was accompanied by