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Electrophysiological abnormalities in myotonic dystrophy
SlOl corticospinal is necessary
tract fibres. Spatiotemporal summation of I-waves for depolarisation of the alpha motoneuron. Thus,
in addition to processes such as demyelination which cause actual slowing of conduction in large myelinated corticospinal axons, any disorder which reduces the size or increases dispersion of the I-wave volley can cause delay in or failure of anterior horn cell discharge. Abnormalities of central motor conduction (CMC) are therefore not specific to any pathophysiological process, though marked prolongation of CMC time is suspicious of demyelination whereas loss of corticomotoneurons or their axons tends to cause low amplitude responses with less delay. CMC studies are abnormal in over 70% of patients with multiple sclerosis and may be helpful for quantification and follow-up purposes, as well as for confirmation of mild motor signs. CMC is less effective than SEPs for demonstrating subclinical lesions of their respective pathways, perhaps reflecting the greater sensitivity of clinical motor testing. CMC studies performed within a few days of acute stroke are of prognostic value, very small responses predicting poor outcome, but are of less value for localisation of the site of the lesion.
ELECTROPHYSIOLOGICAL MYOTONIC DYSTROPHY.
L. Murri, R. Massetani,
(University
ABNORMALITIES
IN
B. Rossi and F. Sartucci
of Pisa, Pisa, Italy)
The involvement of the nervous system in myotonic dystrophy (MD) is supported by numerous data, both clinical and laboratory. We report findings of a multimodal electrophysiological evaluation of the peripheral as well as central nervous system in patients with MD. Brain-stem auditory evoked potentials (BAEPs) were performed in 18 patients, somatosensory evoked potentials (SEPs) in 16 patients and visual evoked potentials (VEPs) in 6 (without retinopathies or cataract). Evoked potentials were found abnormal in 53%, 62.5% and 71.4% of these cases. In 9 the maximal and minimal motor nerve conduction and the percentage of fibres with intermediate velocity using Hopfs technique in the posterior tibial nerve were evaluated. A reduction of maxima1 and minimal conduction velocities was found; the distribution of fibres with intermediate velocity was nearly identical to that of the control group and the dispersion values were normal. Moreover, topographic EEG analysis and brain mapping during wakefulness showed a significant increase of theta band over the entire scalp in 12 patients. The EEG polygraphic recording during sleep showed an apnoea syndrome in 1 case. The various abnormalities observed using different electrophysiological approaches reveal a diffuse involvement of the nervous system in patients with MD.
EEG MAPPING STROKE.
IN
VASCULAR
DISORDERS
AND
K. Nagata (Brain Research
Institute,
Akita,
Japan)
Previous studies in stroke patients suggested a close relationship between reduction of cerebral blood flow (CBF) and slowing of the background EEG as evaluated by visual inspection. Correlation studies have been performed utilizing both topographic quantitative EEG mapping and positron emission tomography (PET) providing quantitative three-dimensional images of CBF and metabolism. The topographic focus of slow-wave activity and the depression of background EEG activity correlated well with the localization of ischemic lesions as shown on CT as well as on PET images in patients with neurological disorders. In the present report, topographic EEG data was compared statistically with cortical CBF and oxygen metabolism (CMRO,) as measured by PET. Confirming the previous knowledge, delta and theta activities increased as CBF and CMRO,, whereas alpha and beta activities decreased. In the acute stage, EEG slowing may reflect reduced CBF more closely than reduced CMRO,. In contrast, in the subacute stage, EEG slowing tends to correlate more closely with CMRO, than with CBF. In the chronic stage, highly significant correlations are seen with both CBF and CMRO,. When the pathophysiological characteristics and stage of discrete cerebra1 infarction are taken into consideration, quantitative EEG mapping provides useful information reflecting the depressed cortical blood flow and/or metabolism of ischemic brain tissue.
SIMULATION OF EARLY CORTICAL SEPs WITH GAUSSIAN DISTRIBUTIONS. R. Nakanishi, M. Harada, Yonemitsu and T. Ideta
H. Yamanaga,
(Kumamoto
Kumamoto,
Kino Hospital,
N. Murayama,
H.
Japan)
In five normal subjects, 16-channel recordings of cortical SEPs evoked by median nerve stimulation were simulated with some Gaussian distribution curves. We kept the peak latency and width of each curve fixed for each individual, changing only the amplitude. Simulations were done by using a computer to the extent of 40 msec in SEPs. Four negative and four positive elements were needed for each simulation. In all five subjects the peak latencies, widths and topographical distributions of each element were similar. Therefore, we named each Gaussian distribution for three factors: electric polarity (N or P), mean peak latency (msec) and mean half width (msec). P14-4, N17-3 and P19-2 were distributed widely on the scalp with low amplitudes. N20-4 and N32-9 were localized in the parietal area contralateral to the stimulation. P22-4 was located in the frontal area and P24-7 was localized in the central area. N24-8
tract fibres. Spatiotemporal summation of I-waves for depolarisation of the alpha motoneuron. Thus,
in addition to processes such as demyelination which cause actual slowing of conduction in large myelinated corticospinal axons, any disorder which reduces the size or increases dispersion of the I-wave volley can cause delay in or failure of anterior horn cell discharge. Abnormalities of central motor conduction (CMC) are therefore not specific to any pathophysiological process, though marked prolongation of CMC time is suspicious of demyelination whereas loss of corticomotoneurons or their axons tends to cause low amplitude responses with less delay. CMC studies are abnormal in over 70% of patients with multiple sclerosis and may be helpful for quantification and follow-up purposes, as well as for confirmation of mild motor signs. CMC is less effective than SEPs for demonstrating subclinical lesions of their respective pathways, perhaps reflecting the greater sensitivity of clinical motor testing. CMC studies performed within a few days of acute stroke are of prognostic value, very small responses predicting poor outcome, but are of less value for localisation of the site of the lesion.
ELECTROPHYSIOLOGICAL MYOTONIC DYSTROPHY.
L. Murri, R. Massetani,
(University
ABNORMALITIES
IN
B. Rossi and F. Sartucci
of Pisa, Pisa, Italy)
The involvement of the nervous system in myotonic dystrophy (MD) is supported by numerous data, both clinical and laboratory. We report findings of a multimodal electrophysiological evaluation of the peripheral as well as central nervous system in patients with MD. Brain-stem auditory evoked potentials (BAEPs) were performed in 18 patients, somatosensory evoked potentials (SEPs) in 16 patients and visual evoked potentials (VEPs) in 6 (without retinopathies or cataract). Evoked potentials were found abnormal in 53%, 62.5% and 71.4% of these cases. In 9 the maximal and minimal motor nerve conduction and the percentage of fibres with intermediate velocity using Hopfs technique in the posterior tibial nerve were evaluated. A reduction of maxima1 and minimal conduction velocities was found; the distribution of fibres with intermediate velocity was nearly identical to that of the control group and the dispersion values were normal. Moreover, topographic EEG analysis and brain mapping during wakefulness showed a significant increase of theta band over the entire scalp in 12 patients. The EEG polygraphic recording during sleep showed an apnoea syndrome in 1 case. The various abnormalities observed using different electrophysiological approaches reveal a diffuse involvement of the nervous system in patients with MD.
EEG MAPPING STROKE.
IN
VASCULAR
DISORDERS
AND
K. Nagata (Brain Research
Institute,
Akita,
Japan)
Previous studies in stroke patients suggested a close relationship between reduction of cerebral blood flow (CBF) and slowing of the background EEG as evaluated by visual inspection. Correlation studies have been performed utilizing both topographic quantitative EEG mapping and positron emission tomography (PET) providing quantitative three-dimensional images of CBF and metabolism. The topographic focus of slow-wave activity and the depression of background EEG activity correlated well with the localization of ischemic lesions as shown on CT as well as on PET images in patients with neurological disorders. In the present report, topographic EEG data was compared statistically with cortical CBF and oxygen metabolism (CMRO,) as measured by PET. Confirming the previous knowledge, delta and theta activities increased as CBF and CMRO,, whereas alpha and beta activities decreased. In the acute stage, EEG slowing may reflect reduced CBF more closely than reduced CMRO,. In contrast, in the subacute stage, EEG slowing tends to correlate more closely with CMRO, than with CBF. In the chronic stage, highly significant correlations are seen with both CBF and CMRO,. When the pathophysiological characteristics and stage of discrete cerebra1 infarction are taken into consideration, quantitative EEG mapping provides useful information reflecting the depressed cortical blood flow and/or metabolism of ischemic brain tissue.
SIMULATION OF EARLY CORTICAL SEPs WITH GAUSSIAN DISTRIBUTIONS. R. Nakanishi, M. Harada, Yonemitsu and T. Ideta
H. Yamanaga,
(Kumamoto
Kumamoto,
Kino Hospital,
N. Murayama,
H.
Japan)
In five normal subjects, 16-channel recordings of cortical SEPs evoked by median nerve stimulation were simulated with some Gaussian distribution curves. We kept the peak latency and width of each curve fixed for each individual, changing only the amplitude. Simulations were done by using a computer to the extent of 40 msec in SEPs. Four negative and four positive elements were needed for each simulation. In all five subjects the peak latencies, widths and topographical distributions of each element were similar. Therefore, we named each Gaussian distribution for three factors: electric polarity (N or P), mean peak latency (msec) and mean half width (msec). P14-4, N17-3 and P19-2 were distributed widely on the scalp with low amplitudes. N20-4 and N32-9 were localized in the parietal area contralateral to the stimulation. P22-4 was located in the frontal area and P24-7 was localized in the central area. N24-8