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Arquivos de Neuro-Psiquiatria

Print version ISSN 0004-282X

Arq. Neuro-Psiquiatr. vol.46 no.1 São Paulo Mar. 1988

http://dx.doi.org/10.1590/S0004-282X1988000100005 

Estudio electrofisiológico de la funcion neuromuscular en una poblacion intoxicada con plomo

 

An electrophysiological study of the skeletal muscle and the peripheral nerve in patients with lead intoxication

 

 

O. M. GenoveseI; Marcela PanizzaI; Honorina ContiII; Alcira BattleIII; R. E. P. SicaI

ISección de Electroneurofisiologia Clínica, Servicio de Neurología - Hospital J.M. Ramos Mejía, Buenos Aires
IIDivisión de Clínica Médica - Hospital J.M. Ramos Mejía, Buenos Aires
IIICentro de Investigaciones sobre Porfirinas y Porfirias, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Buenos Aires - Hospital J.M. Ramos Mejía, Buenos Aires

 

 


RESÚMEN

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.


SUMMARY

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.


 

 

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Sección Electroneurofisiologia Clínica, División Neurología, Hospital J. M. Ramos Mejía - Urquiza 609 - Buenos Aires - Argentina.

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