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New solutions to methodological problems in brain electrical activity mapping
ble we used the following procedure: 8-16 channel EEG for better localization of abnormalities and planning of next procedures: then drug dose was increased (e.g. thiopental) until burst suppression occurred; next, a two-channel CSA monitor was added. We draw the following conclusions: (1) with CSA help it was possible to detect the recurrence of crisis, as electrographical crisis may precede the clinical onset; (2) it is simple to assess CNS drug effects, thus monitoring the dosage required to attain EEG burst suppression; (3) intensive care staff can easily follow the procedure and actively participate in the monitoring; (4) control of crisis was generally attained with doses far exceeding those recommended.
LONG-LOOP
REFLEXES
IN MOVEMENT
DISORDERS.
C.H. Liicking and G. Deuschl
(Freiburg
University,
Freiburg,
F.R.G.)
Activation of muscle afferents by stretch elicits reflex activity of short and long latency (Ml, M2, M3). Electrical stimulation of peripheral mixed nerves also evokes early and late muscle responses: the Hoffmann Reflex (HR) as a pure spinal reflex, and long-latency reflexes (LLR I, II, III) which may be mediated by transcortical loops (!ong-loop reflexes). The enhancement of the M2 response in Parkinson’s disease is related to the amount of rigidity rather than to tremor. On the other hand there is often an enhanced early component of the long-loop reflexes (LLR I) in a certain tremor type of parkinsonian patients as well as in essential tremor with a reciprocal alternating burst activity in antagonistic muscles. In Huntington’s chorea. M2 and LLR II are reduced or abolished without any clear correlation to duration and severity of the disease. Antidopaminergic treatment has no influence on LLR despite clinical improvement. Healthy relatives and patients with symptomatic choreatic syndrome revealed normal LLR in all cases. Patients with focal or generalized dystonia do not present a consistent pathological feature of LLR. In essential myoclonus LLR are normal, whereas in reflex myoclonus the EMG bursts correspond to LLR I or LLR III. It remains open to discussion whether the modification of LLR is related to the pathophysiology of the movement disorders or whether it is only due to common underlying processes.
NOCTURNAL
to carbamazepine (C‘BZ). Because of the association with othclclearly epileptic seizures, and for the clinical feature:; of the attack, we suggest that NPD with short-lasting attacks may represent a variety of epilepsy. probably artsing from deep sited frontal foci. Other varieties of NPD are represented hi. short-lasting paroxysmal behavioural arousals during NREM sleep. often with abnormal motor pattern and without EEG epileptic discharges: atypical periodic movements in sleep. w 1111 fragments of a dystonic attack occurring periodically every 20 set-2 min during NREM sleep, both may respond to CBZ: and NPD with intermediate duration attacks (2-5 min), occurring in children during NREM sleep and wakefulness with peculiar jerky puppet-like movements. and refractory to treatment.
PAROXYSMAL DYSTONIA.
NEW SOLUTIONS TO METHODOLOGICAL PROBLEMS IN BRAIN ELECTRICAL ACTIVITY MAPPING. B. Lumeau
(CNRS,
and G. Rondouin
Gif-sur-Yvette,
France)
Brain mapping of EEG activity (BEAM) was recently proposed as a new tool in the exploration of brain function. Basic assumptions are the random characteristics of EEG signals and the quasi-stationary property of the EEG over a short period. The last assumption is only true for periods of 6-10 sec. so that longer durations of analysis must be used very carefully. Major problems resulting from signal acquisition and conditioning methods must be kept in mind: the characteristics of electrodes, choice of reference, amplifier characteristics and analogue-to-digital conversion may all induce severe errors. Rigorous choice of hardware may contribute to solving this first group of difficulties. Additional problems result from signal processing and interpolation methods. To estimate the power spectral density we propose a method of automatic determination of the convolution window, minimising the bias and variance used to smooth the periodogram. Moreover. the accuracy of EEG mapping is increased by a polynomial interpolation method. The value of these solutions is illustrated with clinical applications.
HIGH RESOLUTION METHODS AS AN APPROACH TO THE LOCALIZATION OF EVOKED POTENTIAL GENERATORS. B. Lumeau, G. Rondouin
and H. Clergeot
E. Lugaresi
(CNRS, (University
of Bologna,
Bologna,
Gif-sur-Yvette,
France)
Italy)
Nocturnal paroxysmal dystonia (NPD) represents a syndrome of paroxysmal dystonic-dyskinetic attacks arising during NREM sleep. NPD with long-lasting attacks (from 2 min to 1 h) is refractory to therapy. NPD with short-lasting (15 set to 2 min) attacks is much more common, and often responds well
High resolution methods have been defined and developed in the fields of spatial processing, in order to localize sources, and spectral analysis, to determine the spectral density of signals. Numerous methods of spatial processing are based on properties of the eigenspace of the spectral density matrix. It is within this framework that the localization of generators relating to
LONG-LOOP
REFLEXES
IN MOVEMENT
DISORDERS.
C.H. Liicking and G. Deuschl
(Freiburg
University,
Freiburg,
F.R.G.)
Activation of muscle afferents by stretch elicits reflex activity of short and long latency (Ml, M2, M3). Electrical stimulation of peripheral mixed nerves also evokes early and late muscle responses: the Hoffmann Reflex (HR) as a pure spinal reflex, and long-latency reflexes (LLR I, II, III) which may be mediated by transcortical loops (!ong-loop reflexes). The enhancement of the M2 response in Parkinson’s disease is related to the amount of rigidity rather than to tremor. On the other hand there is often an enhanced early component of the long-loop reflexes (LLR I) in a certain tremor type of parkinsonian patients as well as in essential tremor with a reciprocal alternating burst activity in antagonistic muscles. In Huntington’s chorea. M2 and LLR II are reduced or abolished without any clear correlation to duration and severity of the disease. Antidopaminergic treatment has no influence on LLR despite clinical improvement. Healthy relatives and patients with symptomatic choreatic syndrome revealed normal LLR in all cases. Patients with focal or generalized dystonia do not present a consistent pathological feature of LLR. In essential myoclonus LLR are normal, whereas in reflex myoclonus the EMG bursts correspond to LLR I or LLR III. It remains open to discussion whether the modification of LLR is related to the pathophysiology of the movement disorders or whether it is only due to common underlying processes.
NOCTURNAL
to carbamazepine (C‘BZ). Because of the association with othclclearly epileptic seizures, and for the clinical feature:; of the attack, we suggest that NPD with short-lasting attacks may represent a variety of epilepsy. probably artsing from deep sited frontal foci. Other varieties of NPD are represented hi. short-lasting paroxysmal behavioural arousals during NREM sleep. often with abnormal motor pattern and without EEG epileptic discharges: atypical periodic movements in sleep. w 1111 fragments of a dystonic attack occurring periodically every 20 set-2 min during NREM sleep, both may respond to CBZ: and NPD with intermediate duration attacks (2-5 min), occurring in children during NREM sleep and wakefulness with peculiar jerky puppet-like movements. and refractory to treatment.
PAROXYSMAL DYSTONIA.
NEW SOLUTIONS TO METHODOLOGICAL PROBLEMS IN BRAIN ELECTRICAL ACTIVITY MAPPING. B. Lumeau
(CNRS,
and G. Rondouin
Gif-sur-Yvette,
France)
Brain mapping of EEG activity (BEAM) was recently proposed as a new tool in the exploration of brain function. Basic assumptions are the random characteristics of EEG signals and the quasi-stationary property of the EEG over a short period. The last assumption is only true for periods of 6-10 sec. so that longer durations of analysis must be used very carefully. Major problems resulting from signal acquisition and conditioning methods must be kept in mind: the characteristics of electrodes, choice of reference, amplifier characteristics and analogue-to-digital conversion may all induce severe errors. Rigorous choice of hardware may contribute to solving this first group of difficulties. Additional problems result from signal processing and interpolation methods. To estimate the power spectral density we propose a method of automatic determination of the convolution window, minimising the bias and variance used to smooth the periodogram. Moreover. the accuracy of EEG mapping is increased by a polynomial interpolation method. The value of these solutions is illustrated with clinical applications.
HIGH RESOLUTION METHODS AS AN APPROACH TO THE LOCALIZATION OF EVOKED POTENTIAL GENERATORS. B. Lumeau, G. Rondouin
and H. Clergeot
E. Lugaresi
(CNRS, (University
of Bologna,
Bologna,
Gif-sur-Yvette,
France)
Italy)
Nocturnal paroxysmal dystonia (NPD) represents a syndrome of paroxysmal dystonic-dyskinetic attacks arising during NREM sleep. NPD with long-lasting attacks (from 2 min to 1 h) is refractory to therapy. NPD with short-lasting (15 set to 2 min) attacks is much more common, and often responds well
High resolution methods have been defined and developed in the fields of spatial processing, in order to localize sources, and spectral analysis, to determine the spectral density of signals. Numerous methods of spatial processing are based on properties of the eigenspace of the spectral density matrix. It is within this framework that the localization of generators relating to