Spinal cord inhibitory mechanisms in Parkinson's disease.

We studied two spinal cord inhibitory mechanisms, recurrent (Renshaw) inhibition and reciprocal inhibition, in seven patients with asymmetric Parkinson's disease in order to determine their contribution to the pathogenesis of rigidity. Recurrent inhibition, studied in the leg, did not differ from that found in normal subjects. All three periods of reciprocal inhibition, studied in the forearm, were present but reduced in magnitude compared with those observed in normal subjects. The arms, whether more symptomatic or less symptomatic, gave similar results. The diminution of all three periods of reciprocal inhibition is similar to the findings in patients with dystonia and is apparently indicative of an abnormal supraspinal influence on spinal mechanisms in these two disorders of basal ganglia function.

H-reflex in nonhomonymous muscles in the human forearm.

In 6 healthy volunteers, stimulation of the median nerve at the elbow elicited H-reflexes in muscles innervated by the ulnar nerve (flexor digitorum profundus of the 4th and 5th digits of the hand) as well as the median nerve (flexor carpi radialis). This finding offers direct physiologic evidence in humans of monosynaptic excitation from group Ia afferents to nonhomonymous muscles, a phenomenon for which only limited indirect evidence existed previously.

H-reflex recovery curve and reciprocal inhibition of H-reflex in different kinds of dystonia.

We studied the H-reflex recovery curve and reciprocal inhibition of the H-reflex bilaterally in the upper limb of 5 patients with generalized dystonia, 5 patients with blepharospasm, 10 patients with spasmodic torticollis, and 14 patients with writer's cramp. We compared the results with those obtained from a group of healthy volunteers. The recovery curve of the H-reflex was normal in patients with writer's cramp or blepharospasm, but showed an increase of the physiologic recovery at a 200 msec delay in patients with spasmodic torticollis or generalized dystonia. Reciprocal inhibition of the H-reflex showed a decrease in the amount of inhibition in all the patient groups and a facilitation of the H-reflex during the 3rd period of inhibition in the patients with spasmodic torticollis or generalized dystonia.

Reciprocal inhibition in patients with hand cramps.

We studied inhibition of median nerve H-reflex produced by radial nerve stimulation in both arms of 14 patients with hand cramps and 15 normal volunteers. Median nerve stimulation was delivered 1 and 0.5 msec before and 0, 0.5, 1, 2, 10, 20, 30, 50, 75, 100, 200, 500, and 1,000 msec after radial nerve stimulation. Recordings were from surface electrodes positioned over flexor carpi radialis. We identified three periods of attenuation of median nerve H-reflex amplitude in the control group. When radial nerve conditioning stimuli were delivered simultaneously, 10 and 75 msec before median nerve test stimuli, H-reflex amplitude diminished to 47%, 61%, and 69%. In the patient group we also found three periods of attenuation at the same delays, but the amount of attenuation was significantly less than in controls. Dividing the patients into two groups, dystonic hand cramp and simple hand cramp, both showed less inhibition than the control group, but the abnormality was greater in the dystonic cramp group. This test is the first to demonstrate physiologic disturbance in patients with hand cramps.

Changes in tetrodotoxin-resistant action potentials after passive transfer of myasthenia gravis patient sera.

Muscle electrical activity has been studied in mice after intraperitoneal injection of sera from myasthenia gravis (MG) patients. Myasthenic serum did not modify the electrical properties of innervated muscle fibres. The resting membrane potential and the action potential parameters remained unchanged. However, tetrodotoxin (TTX)-resistant action potentials of denervated muscles were reduced by myasthenic serum, possibly in association with receptor endocytosis induced by the immunoglobulin. However, a direct effect of MG serum on TTX-resistant sodium channels cannot be ruled out.

Computer-aided determination of the silent period.

Silence of electromyographic (EMG) activity after an evoked muscle twitch has been studied extensively. However, different criteria have been used to determine the level at which the silence of muscle activity ends, and the purpose of this work was to develop an objective method able to determine the silent period even when data were acquired using different EMG instruments. The silent period evoked by transcranial magnetic stimulation was determined bilaterally from abductor pollicis brevis (APB) muscles in 11 subjects, from trapezius muscles in 9 subjects, and from sternocleidomastoid muscles in 11 subjects. All subjects were healthy controls and gave their informed consent to participate in the study. Muscle activity was recorded via surface electrodes. Recordings from 10 stimuli were rectified, averaged, and plotted logarithmically by dividing the mean of the prestimulus EMG activity into the whole trace. Plotted in this way, the one-level represents the mean rectified EMG amplitude of the prestimulus activity. The end of the silent period was measured automatically as the moment at which Student's t test was no longer significantly different, when testing the window of mean prestimulus EMG activity with respect to a 4-ms window centered around the assumed end of the silent period (resolution 0.1 ms). The mean silent periods were 183.7 +/- 49.8 ms for APB, 194.2 +/- 28.8 ms for trapezius, and 194.8 +/- 73.6 ms for sternocleidomastoid muscles, measured from the M-response latency (mean latency: APB 19.7 +/- 1.9 ms, trapezius 7.8 +/- 0.6 ms, and sternocleidomastoid 6.7 +/- 0.8 ms). Computer-aided measurement proved to be a fast and objective tool able to standardize determination of the silent period.

Optimal focal transcranial magnetic activation of the human motor cortex: effects of coil orientation, shape of the induced current pulse, and stimulus intensity.

We studied the effects of coil orientation, stimulus intensity, and shape of the induced current pulse on the amplitudes of motor evoked potentials in the left abductor pollicis brevis of 10 normal adults who had transcranial magnetic stimulation. The optimal direction of currents induced in the brain is approximately perpendicular to the central sulcus, flowing diagonally from back to front. The most effective coil orientation depends on the shape of the induced current pulse and, when the first and second phases of the pulse are of similar size, also on the intensity of stimulation. Optimal mapping of the human motor cortex with magnetic stimulation requires knowledge of the influences of all these factors.

A volume-conduction analysis of magnetic stimulation of peripheral nerves.

Magnetic stimulation is a method to study several nervous disorders as well as the intact nervous system in humans. Interest in magnetic stimulation of peripheral nerves has grown rapidly, but difficulties in locating the site of excitation have prevented it from becoming a routine clinical tool. It has been reasoned that the activating function of long and straight nerves is the first spatial derivative of the electric field component parallel to the nerves. Therefore, to predict the site of activation, one has to compute this field feature. We describe here an analytical mathematical model and investigate the influence of volume-conductor shape on the induced field. Predictions of the site of activation are given for typical stimulation coil arrangements and these results are compared with experimental and literature data. Comparisons suggest that the activating function is not simply the spatial gradient of the induced electric field, but that other mechanisms are also involved. The model can be easily utilized in the search for more efficient coil constructions and improved placements with respect to the target nerves.

Removal of organic pollutants from industrial wastewater by electrogenerated Fenton's reagent.

This study was performed to investigate the treatment of an industrial wastewater mainly containing naphthalene- and anthraquinone-sulphonic acids, by electrogenerated Fenton's reagent. The hydrogen peroxide was produced in situ by electrochemical reduction of oxygen on graphite-felt cathodes and the Fe2+ ions were also regenerated by cathodic reduction of Fe3+. The influence of cathode potential, Fe2+ concentration and electrode surface pre-treatment on chemical oxygen demand (COD) removal and colour fading were studied. Results indicated that the higher COD removal was obtained in the presence of 3 mM of ferrous ions working at a constant potential of -1 V vs. SCE. Moreover, it was shown that both chemical and electrochemical pre-treatments of the cathode surface resulted in a decrease of COD depletion.

Functional and clinical changes in upper limb spastic patients treated with botulinum toxin (BTX).

Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks. In order to study the usefulness of botulinum toxin type A (BTX) as a therapy for spasticity, we studied 15 patients affected by spasticity secondary to stroke. Tests included: clinical evaluation of tone (Ashworth scale); active angles of extension and flexion at elbow and wrist; Hmax/Mmax ratio from flexor carpi radialis (FCR); Hreflex presynaptic inhibition from FCR during vibration; Task score; and video recording. Patients were injected with BTX into one or more muscles with total doses not exceeding 200 International Units (IU). The tests were performed immediately prior to injection and repeated 2 weeks afterwards. Furthermore, in eight patients, testing was also performed one month after BTX injection. Between two weeks and one month after BTX there were no statistically significant differences. A statistically significant difference in the Task and Ashworth scores before and after treatment emerged (p < 0.0014), but only 6 patients showed a clear improvement in motor performance. Overall, we observed an improvement in the angle of active extension and flexion at the wrist and elbow. There were no significant changes in the Hmax/Mmax ratio and the Hreflex presynaptic inhibition during vibration. All the patients reported a subjective improvement. The results suggest that subjective benefits can be gained from the use of BTX in patients affected by spasticity, and that the degree of motor improvement seems to depend on the motor recovery obtained before treatment.

EMGLAB: objective outcome measures in neurophysiological testing.

The aim of this work was to objectively measure and quantify the results of various neurophysiological tests and indirectly provide objective outcome measures for neurological therapy and rehabilitation. We have studied the silence of Electromyographic (EMG) activity after evoking motor potentials with magnetic cortical stimulation. Since different criteria were previously used to determine the level where the silence of muscle activity ends, an objective computer aided method was developed. This analysis was further developed to include objective testing of surface EMG, long latency reflexes, reciprocal inhibition of the H-reflex, H-reflex recovery curve and decrement testing. Responses were recorded at different sampling frequencies, depending on the application, time window, filter settings, etc. The developed software proved to be a fast and objective tool, able to standardize the determination of different neurophysiological tests, and as such a valuable tool facilitating multi-center studies and diminishing human bias. The software reduced the study time with each patient. Until date we have used the software with the Medtronic, Medelec and BTS EMG instruments.

Masked myoclonus in corticobasal degeneration: neurophysiological study of a case.

A single case study of a 58 year-old male with right asymmetric apraxia and akinetic-rigid syndrome is described. Brainimaging scans (MRI, SPECT) indicated asymmetric cortical atrophy compatible with the diagnosis of Corticobasal Degeneration. Reflex myoclonus was absent and myoclonic discharges only appeared in response to pharmacological treatment of limb dystonia and rigidity. Electromyographic evidence of jerky movements was recorded only in the affected right hand and forearm after muscle relaxation, and myoclonus was not preceded by an EEG paroxysm. The cortical components of the correspondent SEPs were not increased in amplitude while LLRs recordings showed a late response over the muscles of the affected side. Furthermore, the duration of post MEP silent period was bilaterally reduced. This single case study report points out that sometimes myoclonus in Corticobasal Degeneration can be masked by the presence of increased muscle tone.

[Electrophysiological study of neuromuscular function in a population poisoned by lead]. / Estudio electrofisiológico de la función neuromuscular en una población intoxicada con plomo.

A comprehensive electrophysiological examination of the peripheral nervous system was carried out in 12 patients who proved to be toxicated with lead (high lead blood levels, and diminished activity of the delta-aminolevulinate dehydratase, ALA D, in erythrocytes). Maximal motor nerve conduction velocities and terminal latencies were investigated in the median, radial and deep peroneal nerves. Also the amplitude of the evoked muscle response (M wave) was measured in thenar, extensor longus and extensor digitorium brevis muscles. Sensory conduction velocity and amplitude of the nerve compound action potential were measured at the median nerve. Tibialis anterior muscle responses to deep peroneal nerve repetitive stimulation were also explored. Conventional needle electromyogram was performed in the deltoid and tibialis anterior muscles. Slight diminished motor and sensory conduction velocities were found as well as a reduction of the amplitude of the evoked muscle response of the compound sensory action potential. Four out of the 12 patients tested showed either decremental or incremental amplitude of the muscle response with nerve repetitive stimulation. A electromyographical diminished interference pattern was found in all patients tested. Most of the remaining motor unit potentials were fragmented or polyphasic. Just one patient disclosed potentials of enhanced duration and amplitude. No relationship was found between blood lead levels or ALA D erythrocytes concentration and the different electrophysiological tests performed, except between reduced ALA D concentration and diminished amplitudes of the M wave and of the sensory compound action potential, and also between ALA D and diminished radial motor conduction velocity.(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of central and peripheral components of muscular fatigue in neuropathic and myopathic patients]. / Evaluación del componente central y periférico de fatiga muscular en pacientes neuropáticos y miopáticos.

In a group of patients chronically denervated and other with primary muscle involvement a search was made for mechanisms involved in the muscular fatigue. It was found that there was no major differences between patients chronically denervated and controls, while in those others with primary muscle disorders a loss of functional motor units during effort and a transient impairment of neuromuscular transmission play a role together with the central events normally occurring in fatigue.

[Evaluation of central and peripheral factors in muscular fatigue]. / Evaluación del factor central y periférico en fatiga muscular.

Muscular fatigue was investigated in 13 healthy people by employing a simple device which comprises a computer on line with a conventional EMG equipment able to automatically measure the frequency and duration of free-run EMG recording. The procedure was carried out in the extensor digitorum brevis muscle by using surface electrodes throughout 10 minutes of voluntary maximal effort. The maximal M wave as well as the muscle response to repetitive nerve maximal stimulation was also explored at the beginning and at the end of the experiment. It was observed a decrease of the potentials frequency discharge and an increase of their duration without major changes in the M wave amplitude neither in the muscle response to the repetitive nerve discharge. The findings pointed out to the central factors as the mean responsible for the development of muscular fatigue.

[Evaluation of central and peripheral factors in muscular fatigue in patients with pyramidal lesions]. / Evaluación del factor central y periférico en fatiga muscular en pacientes con daño piramidal.

Muscular fatigue mechanisms were partially analyzed in patients with pyramidal lesions by using a computer device on line with a conventional electromyograph. Both the normal and the affected side were compared with control groups. The recordings were done throughout a ten minutes period and the maximal M wave was also measured at the starting and at the end of the procedure. The findings suggested that central events play a major role in the development of muscular fatigue in spastic muscles due to pyramidal damage.

Peripheral nerve involvement in Bell's palsy.

A group of patients with Bell's palsy were studied in order to disclose the presence of subclinical peripheral nerve involvement. 20 patients, 8 male and 12 female, with recent Bell's palsy as their unique disease were examined. In all cases other causes of polyneuropathy were ruled out. Patients were investigated with CSF examination, facial nerve latencies in the affected and in the sound sides, and maximal motor nerve conduction velocities, as well as motor terminal latencies from the right median and peroneal nerves. CSF laboratory examination was normal in all cases. Facial nerve latencies were abnormal in all patients in the affected side, and they differed significantly from those of control group in the clinically sound side. Half of the patients showed abnormal values in the maximal motor nerve conduction velocities and motor terminal latencies of the right median and peroneal nerves. These results agree with previous reports which have pointed out that other cranial nerves may be affected in Bell's palsy. However, we have found a higher frequency of peripheral nerve involvement in this entity. These findings, support the hypothesis that in some patients Bell's palsy is the component of a more widespread disease, affecting other cranial and peripheral nerves.

[Diagnosis and treatment of myasthenia gravis: study of an inpatient population]. / Diagnóstico y tratamiento de la myasthenia gravis: estudio de una población hospitalaria.

Between 1974 and 1987 we have examined 50 patients with the diagnosis of myasthenia gravis. Female preponderance (2.5: 1) was found. Also, it was observed that most of the patients were aged between 20 and 49 years. Beside the clinical examination, the following tests were performed: (1) edrofonium test, (2) supramaximal repetitive nerve stimulation, (3) serum acetylcholine antibodies titers and (4) intraperitoneal passive transference of patient's sera to mice and recording of meepp's amplitude in the phrenic-diaphragm preparation in vitro. These four tests gave positive values for myasthenia in 90 to 100% of the cases. Thymus radiological examination was carried out by pneumomediastinography, which proved to correlate with the histological picture of the gland, and computed tomography, which disclosed some discrepances with the histology. Treatment was based on anticholinesterase drugs, corticosteroids and thymectomy, being the corticosteroids the most valuable therapeutical tool. Nine patients treated with steroids disclosed transitory worsening of their signs and symptoms at very early stages after onset of corticosteroid therapy, 6 of them had a disfavorable course in their follow-up. This observation seem to have value in the early prognosis of the disease.

Effect of passive transfer of myasthenic serum on mechanical, electrical and neuromuscular transmission properties of mouse skeletal muscle.

Neuromuscular transmission, muscle electrical activity and muscle mechanical properties have been studied in mice after the intraperitoneal transference of sera from myasthenic patients. Measurements of mepp's amplitude appear to be a suitable method for myasthenia gravis diagnosis since a high percentage of the sera from these patients caused a decrease in mepp's amplitude. The increase of the premenstrum weakness in myasthenic patients did not appear to be associated with greater fall of mepp's amplitude, since serum obtained in the premenstruum and far from it produced similar results. Myasthenic serum did not modify the electrical properties of innervated muscle sarcolemma. The resting membrane potential and the action potential parameters remained unchanged. However, tetrodotoxin resistant-action potentials of denervated muscles was reduced by myasthenic serum, possibly in association with receptor endocytosis process induced by the immunoglobulin. Muscle mechanical properties did not show alterations, even in the presence of positive titer of anti-striated muscle antibody.