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Are the fibres of the human vagus nerve excitable by magnetic stimulation?
S124 MYOBIOFEEDBACK IN MOTOR RE-EDUCATION OF WRIST AND FINGERS AFTER HEMISPHERIC STROKE.
ARE THE FIBRES OF THE HUMAN VAGlJS EXCITABLE BY MAGNETIC STIMULATION?
NERVE:
G. Reichel and ‘I’. Rabe D. Rathkolb,
St. Baykoushev
and V. Baykousheva (College
(I.P. Pavlov Higher
Medical
Institute,
Plovdiv,
Bulgaria)
Thirty-two patients with different grades of hemiparesis, in the first weeks after a cerebral vascular accident, were treated by means of EMG-feedback during volar and dorsal flexion of the wrist, flexion and extension of the fingers, and opposition of the thumb to the second and other fingers. EMG was recorded from suitable muscles of the paretic limb. Attempted volitional movement of the paretic side was conditioned with a reinforced mirror synergia from the healthy to the damaged side. The patient observed the effect on the EMG screen. After 3-6 conditioning sessions the patient performed the volitional movement alone. In 25 patients (78.1%) improvements were obtained at least in EMG. A good correlation was found between effect of procedures and severity of paresis (x2 = 7.35, P < 0.05).
STANDARDIZED STIMULATION
FACILITATION DURING OF THE CORTEX.
M. Raunborg, M. Blinkenberg
(Rigshospitalet,
Copenhagen,
MAGNETIC
and K. Dahl
Denmark)
of Medicine,
East Germany)
Magnetic fields penetrate human tissue without decrease. thus providing an advantage over electrical stimulation in the examination of deep-seated nerves. However, in investigation of the nerves of the neck there is the danger that disturbances of cardiac rhythm could be produced by unintentional stimulation of the vagus nerve. We have recorded from 20 healthy volunteers to discover whether or not this is a real possibility. The centre point of the coil of a magnetic stimulator was placed at the front edge of the sternocleidomastoid muscle and supramaximal stimuli (referred to phrenic nerve) were delivered at random intervals. Potentials of the diaphragm were recorded from stick-on electrodes at the 8th intercostal space and the ECG was continuously recorded using a conventional technique. After establishing the stimulus intensity which evoked the maximum potential at the diaphragm, 20 intervals of the R-wave of the ECG were measured before (A). during (B) and after (C) magnetic stimulation. Average R-wave intervals (and standard deviations) were A: 1.015 (0.136), B: 1.016 (0.117) and C: 1.000 (0.107) sec. Thus, we conclude that in healthy adults aged 20 to 40 years magnetic stimulation of cervical nerves does not produce any change in cardiac rhythm.
STATE SPACE DISPLAY
OF EEG CHAOTIC
DYNAMICS.
S.A. Reid, F.S. Ku and J. Principe (University
The relation between central motor conduction time (CMCT) and the facilitation of the target muscles was studied in 16 healthy volunteers and 16 multiple sclerosis patients, using magnetic stimulation of the cerebral cortex and the spinal roots. The aim was to define optimal facilitation levels for 5 selected muscles by studying the effect of increasing voluntary background contraction on the CMCT. The results of the two groups were compared. The facilitation was standardized by the root mean square (RMS) of the EMG at the moment of stimulation. The RMS range studied was O-408 of the maximal RMS (RMS,,,,). Surface recordings were made from the following muscles: the biceps bra&ii (BB), the radial flexor (FCR), the first dorsal interosseus (FDI), the anterior tibia1 (AT) and the abductor hallucis (AH). In the control group significant reductions of CMCTs were seen in all the muscles as RMS increased from 0 to 5-10s. The upper confidence limits of the CMCTs (mean + 2 standard deviations) fell to a minimum in the RMS range of 5-208. At higher RMS levels the CMCTs became less reproducible. No difference was found in the effect of facilitation on CMCT between healthy and demyelinated motor pathways.
Erfurt.
of Florida,
Gainesville,
FL, USA)
Analysis of EEG has changed little since the days of the string galvanometer. Modern electroencephalographers scrutinize voltage plots in the time domain to identify relationships between EEG events and physiologic states. Our display program maps EEG data to a state space. A dynamical system, dX(t)/dt = f(X;k), described by N-coupled non-linear differential equations can often be reduced to an N order non-linear differential equation with respect to the measured variable, X. It can be proved that the state-space description with coordinates given by X(t) (the signal) and its N-l time derivatives is topologically equivalent to the state description of the original system. Using the sampled X(t), one can create a topologically equivalent state space description with coordinates X(nT), X(nT+ t), X[(nT+ (N - l)t], where t is an arbitrary time lag. If the order of the dynamical system is N, and the lag t is set equal to the sampling period, then the values of the points of the time series X(nT) can be used to construct the N dimensional state space portrait. Many traditional time-domain EEG events have distinctive. easily recognizable state space portraits. We will show a video-
s125 tape of 3-dimensional tions of several normal
projections of state space representaand pathological EEG events.
VISUAL EVOKED POTENTIALS IN GRAVES DISEASE. F. Reisecker, Eber (Hospital
P. Koltringer,
P. Lind,
W. Langsteger
Brueder,
Barmherzige
de Leon. V.I. Ruggieri
Dr. J.P. Garraham,
Buenos Aires, Argentma)
Graz, Austria)
THE INFLUENCE OF PATIENT VARIABLES ON LATENCIES OF MOTOR EVOKED POTENTIALS FOLLOWING MAGNETIC STIMULATION. K. Mahr,
L. Sanchez
and 0.
Optomotoric dysfunction is very often observed in Graves’ disease, whereas visual disturbances are a rarity. Visual evoked potentials (VEP) may detect subclinical dysfunctions of optic nerve. 14 patients (12 female, mean age 56 years) suffering from proven Graves’ disease were investigated with VEP on both eyes. VEP was evoked by pattern reversal stimulation. PlOO latency was evaluated and compared to healthy controls (n = 33, mean: 100.1 msec, SD: 4.1). Latency deviations of more than 2.5 SD were considered as pathological. Significantly prolonged PlOO latencies were found bilaterally in 10 patients and in the right eye only for another. According to these results in most cases of Graves’ disease a dysfunction of the optic nerve can be found. Pathogenetic mechanisms such as compression or an endocrine neuropathy should be considered.
(Hospital
R. C. Reisin, M.E. Massaro, and C. Medina (Hospital
Barmherzige
F. Reisecker,
BRAIN-STEM AUDITORY EVOKED POTENTIAL ABNORMALITIES IN CHILDREN WITH NEUROFIBROMATOSIS TYPE I.
P. Koeltringer,
and J. Morocutti
We report 4 children with neurofibromatosis (NF) type I and unilaterally delayed I-V interpeak latency ( > 4.6 msec) in their brain-stem auditory evoked responses (BAER). None had brain-stem signs or symptoms and the BAER changes have remained stable for 1 and 4 years in 2 patients. MRI, performed in 2 patients. showed small focal areas of increased signal within the brain parenchyma, on T2-weighted images, in both. None of the four had acoustic neuromas or other extra-axial lesions compressing the brain-stem. The four presented abnormalities in their visual pathways: two had chiasmatic tumors and the other two had unilaterally delayed VEP with normal orbital CT. These BAER abnormalities, in the absence of extrinsic brain-stem compression, as well as the recently reported “unidentified bright objects” on MRI probably represent the widespread distribution of haematomas in this disorder. Close follow-up and repeated examinations are needed for early identification of those lesions that may undergo neoplastic transformation. The association of optic nerve abnormalities in all our patients may indicate an increased predisposition to develop dysgenetic or neoplastic lesions in this subgroup of NF with abnormal BAER.
Briider, Graz, Austria)
Motor evoked potentials following transcranial, spinal and peripheral magnetic stimulation were recorded from 20 healthy volunteers (17 male, mean age 42 years, SD 13.1). The contralateral precentral region, the 7th cervical vertebra and the ipsilateral Erb’s point were used as stimulation sites. Recording leads from biceps bra&ii, extensor digitorum communis and abductor digiti V on either side of the body were connected in a bipolar montage. Latencies from each muscle were evaluated according to stimulation site and side of recording. The central motor conduction time, taken as the difference between cortical and spinal latencies, and the peripheral transmission time, taken as the difference between spinal and peripheral latencies. were also analysed. By analogy with the assessment of somatosensory evoked potentials the above measures were correlated with subject height, arm length and age. There was a good correlation between the response times in different leads and there were no differences between latencies recorded from the left and right sides. However, in contrast with findings for the somatosensory evoked potential, the patient variables of height, arm length and age did not correlate with conduction times. This finding might be related to the high standard deviation of the data.
CHANGES OF SHORT-LATENCY SOMATOSENSORY EVOKED POTENTIALS DURING SLEEP IN CHILDREN. R.C. Reisin, (Hospital
I. Sanchez
de Leon and C. Medina
Dr. J.P. Garraham,
Buenos
Aires, Argentina)
We compared the latency and amplitude of the cervical and cortical responses to median nerve stimulation during wakefulness and chloral hydrate (30 mg/kg) induced sleep in 9 children. The cervical responses showed no change in latency but an increment in the amplitude during sleep, the latter, probably reflecting the reduction of muscle artefact. The main findings in the study were the changes of the N20 cortical response which showed increased latency and marked attenuation or complete disappearance of the response during sleep. Latency and amplitude of the N20 potential reverted to waking values during REM sleep. The cortical responses of 7/9 patients awakened during the study immediately returned to their pre-sleep latency and amplitude.
ARE THE FIBRES OF THE HUMAN VAGlJS EXCITABLE BY MAGNETIC STIMULATION?
NERVE:
G. Reichel and ‘I’. Rabe D. Rathkolb,
St. Baykoushev
and V. Baykousheva (College
(I.P. Pavlov Higher
Medical
Institute,
Plovdiv,
Bulgaria)
Thirty-two patients with different grades of hemiparesis, in the first weeks after a cerebral vascular accident, were treated by means of EMG-feedback during volar and dorsal flexion of the wrist, flexion and extension of the fingers, and opposition of the thumb to the second and other fingers. EMG was recorded from suitable muscles of the paretic limb. Attempted volitional movement of the paretic side was conditioned with a reinforced mirror synergia from the healthy to the damaged side. The patient observed the effect on the EMG screen. After 3-6 conditioning sessions the patient performed the volitional movement alone. In 25 patients (78.1%) improvements were obtained at least in EMG. A good correlation was found between effect of procedures and severity of paresis (x2 = 7.35, P < 0.05).
STANDARDIZED STIMULATION
FACILITATION DURING OF THE CORTEX.
M. Raunborg, M. Blinkenberg
(Rigshospitalet,
Copenhagen,
MAGNETIC
and K. Dahl
Denmark)
of Medicine,
East Germany)
Magnetic fields penetrate human tissue without decrease. thus providing an advantage over electrical stimulation in the examination of deep-seated nerves. However, in investigation of the nerves of the neck there is the danger that disturbances of cardiac rhythm could be produced by unintentional stimulation of the vagus nerve. We have recorded from 20 healthy volunteers to discover whether or not this is a real possibility. The centre point of the coil of a magnetic stimulator was placed at the front edge of the sternocleidomastoid muscle and supramaximal stimuli (referred to phrenic nerve) were delivered at random intervals. Potentials of the diaphragm were recorded from stick-on electrodes at the 8th intercostal space and the ECG was continuously recorded using a conventional technique. After establishing the stimulus intensity which evoked the maximum potential at the diaphragm, 20 intervals of the R-wave of the ECG were measured before (A). during (B) and after (C) magnetic stimulation. Average R-wave intervals (and standard deviations) were A: 1.015 (0.136), B: 1.016 (0.117) and C: 1.000 (0.107) sec. Thus, we conclude that in healthy adults aged 20 to 40 years magnetic stimulation of cervical nerves does not produce any change in cardiac rhythm.
STATE SPACE DISPLAY
OF EEG CHAOTIC
DYNAMICS.
S.A. Reid, F.S. Ku and J. Principe (University
The relation between central motor conduction time (CMCT) and the facilitation of the target muscles was studied in 16 healthy volunteers and 16 multiple sclerosis patients, using magnetic stimulation of the cerebral cortex and the spinal roots. The aim was to define optimal facilitation levels for 5 selected muscles by studying the effect of increasing voluntary background contraction on the CMCT. The results of the two groups were compared. The facilitation was standardized by the root mean square (RMS) of the EMG at the moment of stimulation. The RMS range studied was O-408 of the maximal RMS (RMS,,,,). Surface recordings were made from the following muscles: the biceps bra&ii (BB), the radial flexor (FCR), the first dorsal interosseus (FDI), the anterior tibia1 (AT) and the abductor hallucis (AH). In the control group significant reductions of CMCTs were seen in all the muscles as RMS increased from 0 to 5-10s. The upper confidence limits of the CMCTs (mean + 2 standard deviations) fell to a minimum in the RMS range of 5-208. At higher RMS levels the CMCTs became less reproducible. No difference was found in the effect of facilitation on CMCT between healthy and demyelinated motor pathways.
Erfurt.
of Florida,
Gainesville,
FL, USA)
Analysis of EEG has changed little since the days of the string galvanometer. Modern electroencephalographers scrutinize voltage plots in the time domain to identify relationships between EEG events and physiologic states. Our display program maps EEG data to a state space. A dynamical system, dX(t)/dt = f(X;k), described by N-coupled non-linear differential equations can often be reduced to an N order non-linear differential equation with respect to the measured variable, X. It can be proved that the state-space description with coordinates given by X(t) (the signal) and its N-l time derivatives is topologically equivalent to the state description of the original system. Using the sampled X(t), one can create a topologically equivalent state space description with coordinates X(nT), X(nT+ t), X[(nT+ (N - l)t], where t is an arbitrary time lag. If the order of the dynamical system is N, and the lag t is set equal to the sampling period, then the values of the points of the time series X(nT) can be used to construct the N dimensional state space portrait. Many traditional time-domain EEG events have distinctive. easily recognizable state space portraits. We will show a video-
s125 tape of 3-dimensional tions of several normal
projections of state space representaand pathological EEG events.
VISUAL EVOKED POTENTIALS IN GRAVES DISEASE. F. Reisecker, Eber (Hospital
P. Koltringer,
P. Lind,
W. Langsteger
Brueder,
Barmherzige
de Leon. V.I. Ruggieri
Dr. J.P. Garraham,
Buenos Aires, Argentma)
Graz, Austria)
THE INFLUENCE OF PATIENT VARIABLES ON LATENCIES OF MOTOR EVOKED POTENTIALS FOLLOWING MAGNETIC STIMULATION. K. Mahr,
L. Sanchez
and 0.
Optomotoric dysfunction is very often observed in Graves’ disease, whereas visual disturbances are a rarity. Visual evoked potentials (VEP) may detect subclinical dysfunctions of optic nerve. 14 patients (12 female, mean age 56 years) suffering from proven Graves’ disease were investigated with VEP on both eyes. VEP was evoked by pattern reversal stimulation. PlOO latency was evaluated and compared to healthy controls (n = 33, mean: 100.1 msec, SD: 4.1). Latency deviations of more than 2.5 SD were considered as pathological. Significantly prolonged PlOO latencies were found bilaterally in 10 patients and in the right eye only for another. According to these results in most cases of Graves’ disease a dysfunction of the optic nerve can be found. Pathogenetic mechanisms such as compression or an endocrine neuropathy should be considered.
(Hospital
R. C. Reisin, M.E. Massaro, and C. Medina (Hospital
Barmherzige
F. Reisecker,
BRAIN-STEM AUDITORY EVOKED POTENTIAL ABNORMALITIES IN CHILDREN WITH NEUROFIBROMATOSIS TYPE I.
P. Koeltringer,
and J. Morocutti
We report 4 children with neurofibromatosis (NF) type I and unilaterally delayed I-V interpeak latency ( > 4.6 msec) in their brain-stem auditory evoked responses (BAER). None had brain-stem signs or symptoms and the BAER changes have remained stable for 1 and 4 years in 2 patients. MRI, performed in 2 patients. showed small focal areas of increased signal within the brain parenchyma, on T2-weighted images, in both. None of the four had acoustic neuromas or other extra-axial lesions compressing the brain-stem. The four presented abnormalities in their visual pathways: two had chiasmatic tumors and the other two had unilaterally delayed VEP with normal orbital CT. These BAER abnormalities, in the absence of extrinsic brain-stem compression, as well as the recently reported “unidentified bright objects” on MRI probably represent the widespread distribution of haematomas in this disorder. Close follow-up and repeated examinations are needed for early identification of those lesions that may undergo neoplastic transformation. The association of optic nerve abnormalities in all our patients may indicate an increased predisposition to develop dysgenetic or neoplastic lesions in this subgroup of NF with abnormal BAER.
Briider, Graz, Austria)
Motor evoked potentials following transcranial, spinal and peripheral magnetic stimulation were recorded from 20 healthy volunteers (17 male, mean age 42 years, SD 13.1). The contralateral precentral region, the 7th cervical vertebra and the ipsilateral Erb’s point were used as stimulation sites. Recording leads from biceps bra&ii, extensor digitorum communis and abductor digiti V on either side of the body were connected in a bipolar montage. Latencies from each muscle were evaluated according to stimulation site and side of recording. The central motor conduction time, taken as the difference between cortical and spinal latencies, and the peripheral transmission time, taken as the difference between spinal and peripheral latencies. were also analysed. By analogy with the assessment of somatosensory evoked potentials the above measures were correlated with subject height, arm length and age. There was a good correlation between the response times in different leads and there were no differences between latencies recorded from the left and right sides. However, in contrast with findings for the somatosensory evoked potential, the patient variables of height, arm length and age did not correlate with conduction times. This finding might be related to the high standard deviation of the data.
CHANGES OF SHORT-LATENCY SOMATOSENSORY EVOKED POTENTIALS DURING SLEEP IN CHILDREN. R.C. Reisin, (Hospital
I. Sanchez
de Leon and C. Medina
Dr. J.P. Garraham,
Buenos
Aires, Argentina)
We compared the latency and amplitude of the cervical and cortical responses to median nerve stimulation during wakefulness and chloral hydrate (30 mg/kg) induced sleep in 9 children. The cervical responses showed no change in latency but an increment in the amplitude during sleep, the latter, probably reflecting the reduction of muscle artefact. The main findings in the study were the changes of the N20 cortical response which showed increased latency and marked attenuation or complete disappearance of the response during sleep. Latency and amplitude of the N20 potential reverted to waking values during REM sleep. The cortical responses of 7/9 patients awakened during the study immediately returned to their pre-sleep latency and amplitude.