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 hsitological 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.

Durante la observacion de 50 pacientes con Myasthenia gravis entre los anos 1974 y 1987 se encontro un predominio del sexo femenino en la proporcion de 2,5 a 1 y mayor frecuencia de presentacion en Ias 3ª y 5ª décadas de la vida. Luego de la evaluacion clínica, el diagnóstico fué confirmado mediante: (1) prueba dei edrofonio, (2) estímulo nervioso repetitivo, (3) dosaje de anticuerpos antirreceptor colinérgico y (4) transferencia pasiva del suero al raton con ulterior niedicion de la amplitud de mepp's. La positividad diagnostica vario entre el 90 y el 100%, segun el tipo de prueba empleada. El estúdio radiológico del timo fué hecho con neumomediastinografía. obteniendose excelente correlación con la descripcion histológica de la glândula, y con tomografia computada, que demostro menor eficiência diagnostica. El tratamiento fué implementado en base a anticolinesterásicos, timectomía y corticoterapia inmunosupresora, evidenciandose con esta última mejores resultados. Nueve pacientes desarrollaron peoria transitória del cuadro muscular al iniciarse el tratamiento esteroideo, 6 de ellos exhibieron posteriormente evolucion desfavorable. Esta observacion aparenta tener valor pronóstico en la evolucion de la MG.

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 décrémentai 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. Only a slight relationship was found between timing of toxication and diminished sensory conduction velocity of the median nerve and motor conduction velocity of the radial nerve. Biochemical determination and timing of toxication did not prove to be useful tools for predicting peripheral nervous system damage. The findings suggest that the neuropathy which develops in lead intoxication is probably related mainly to individual predisposition rather than to lead blood levels and ALA D erythrocytes concentration.

Un grupo de 12 pacientes con cifras elevadas de plombemia y disminuidas de ALA D fueron estudiados electrofisiológicamente. Se efectuaron las siguientes determinaciones: amplitud de potencial evocado muscular; latencia distal motora; velocidad de conducción motora en los nervios mediano, ciático poplíteo externo y radial; velocidad de conducción sensitiva y amplitud del potencial evocado sensitivo de nervio en el mediano; exploración electromiográfica convencional; estudio de la transmisión neuromuscular, mediante estimulación repetitiva del nervio ciático popliteo externo a diversas frecuencias, con registro de la amplitud del potencial en músculo tibial anterior. Los datos obtenidos fueron comparados con controles. Se buscaron correlaciones entre las determinaciones bioquímicas y los diferentes hallazgos electrofisiológicos que a su vez se correlacionaron entre si y también con el tiempo de evolución de la intoxicación. Los hallazgos pusieron de manifiesto la presencia de neuropatía axonal junto a moderada desmielinización. La exploración de la transmisión neuromuscular mostró ocasional decremento o incremento de la amplitud del potencial muscular evocado, hechos que suponen cierta participación de la unión neuromuscular. Se halló correlación solamente entre disminución de ALA D y la disminución de las amplitudes del potencial sensitivo del mediano y el evocado muscular del mismo nervio y con la disminución de la VCM del nervio radial. Una débil relación se observó entre el tiempo de exposición y la disminución de la VCS del nervio mediano y VCM del radial. Las determinaciones bioquímicas y el tiempo de exposición transcurridos no probaron ser parámetros sensibles para determinar el grado de afectación del sistema nervioso periférico. El conjunto do hallazgos sugiere que el desarrollo de la neuropatía puede estar ligado a factores individuales de predisposición al daño nervioso.

Um grupo de pacientes com paralisia de Bell foi estudado com o objetivo de descobrir a presença de comprometimento nervoso periférico subclínico. 20 pacientes, 8 homens e 12 mulheres com paralisia de Bell recente como única enfermidade, foram examinados. Em todos os casos outras causas de polineuropatia foram excluídas. Os pacientes foram estudados com exames de líquido cefalorraqueano; latência distal nos nervos faciais do lado afetado e do lado sadio e velocidade de condução motora máxima; latência distal dos nervos mediano e peroneiro direitos. O exame de LCR foi normal em tcdos os casos. A latência do nervo facial foi anormal em todos os pacientes no lado afetado e, no lado clinicamente sadio, diferia significativamente do grupo controle. A metade dos pacientes mostrou valores anormais na velocidade motora máxima e/ou na latência distal de ambos os nervos, como sejam: mediano e peroneiro. Esses resultados estão de acordo com publicações anteriores nas quais se afirma que outros nervos craneanos podem estar afetados na paralisia de Bell. Temos encontrado uma elevada frequência de polineuropatia nesta enfermidade. Estes achados nos levam a crer que, em alguns enfermos, a paralisia de Bell é um componente de uma doença mais disseminada afetando outros nervos craneanos e periféricos.

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.

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.

Para evaluar algunos de los componentes de la fatiga muscular en el daño piramidal, se seleccionó un grupo de 15 pacientes con hemiparesia faciobraquiocrural de severidad variable, los cuales fueron sometidos a un esfuerzo muscular, durante el cual se evaluaron los cambios de la frecuencia y duración de los potenciales positivos y negativos del EMG, asi como los sufridos por la onda M máxima al principio y fin del mismo. El estudio fue realizado en el lado parético, el contralateral y en un grupo control de voluntarios sanos, comparándose los resultados de los 3 grupos. Las curvas de frecuencia y duración del lado parético, el sano y el control mantuvieron las mismas tendencias, así como fue homologable el comportamiento de la onda M máxima en los 3 casos, lo cual indica que en la espasticidad, debido a daño de la vía piramidal, al igual que en la población normal, bajo las presentes condiciones de estudio, es el factor central el condicionante principal en el desarrollo de fatiga muscular.

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 occuring in fatigue.

Utilizando un método de cuantificación del electromiograma, se investigaron parte de los mecanismos centrales y periféricos responsables de la fatiga muscular en enfermos crónicamente denervados y en pacientes con compromiso muscular primitivo. Se observó en los denervados que los mecanismos de fatiga muscular, no difieren mayormente de los observados en el grupo de sujetos sanos, por el contrario, en los miopáticos a más del componente central, existen otros de orden periférico, tales como la pérdida de unidades motoras funcionantes durante el esfuerzo y el bloqueo temporario de la transmisión neuromuscular, que contribuye al desarrollo de la fatiga.

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 main responsible for the development of muscular fatigue.

Se estúdio la fatiga muscular en 13 sujetos normales; para ello, fueron sometidos a un esfuerzo sostenido durante 10 minutos previo y posterior, al cual se realizo la medición de la onda M máxima. Durante el esfuerzo y cada 2 minutos, se obtuvieron cuantificaciones de la frecuencia y duración de las ondas positivas y negativas del EMG. Los resultados, mostraron diferencias significativas de estos valores, en función del tiempo de esfuerzo realizado, mientras que las mediciones de la onda M máxima inicial y final, no fueron diferentes, todo lo cual lleva a jerarquizar el factor central como el más importante en el desarrollo de fatiga, bajo nuestras condiciones de estudio, que son además de sencilla aplicación clínica.