Determination of electric current perception threshold in a sample of normal volunteers

Reference values using the instrument Neurometer® were determined and compared with those suggested by the manufacturer; the sensory thresholds for the different frequencies in different body segments were determined; the influence of age, level of education, gender and the reutilization of the electrodes in the different sites were also evaluated. Sensory threshold was determined in 101 normal volunteers (68 women), ages ranged from 17 to 87 years old. The procedure was fully automated with the sensory threshold being determined by the method of limits followed by the forced choice method. Analysis of the results revealed that: there was a significant difference between the values obtained for the index fingers and the halux; no difference was detected between both index fingers; gender and level of instruction had no effect on the results, age had a small influence after stimulation with 2000Hz and 250Hz; three reutilizations of the electrodes did not affect the results on the index fingers, however at the halux, the third utilization deteriorated the results from the 2000Hz stimulation. Except for the 2000Hz stimulation, significant differences were suggested between the values reported here and those provided by the manufacturer.Determinaram valores de referência para limiares de percepção de corrente elétrica senoidal em indivíduos normais, utilizando-se o instrumento Neurometer®; contrastaram-se os resultados com os fornecidos pelo fabricante; analisaram-se os limiares em diferentes segmentos corporais e avaliou-se o efeito da idade, sexo, grau de escolaridade e reutilização dos eletrodos. Estudou-se uma amostra de 101 voluntários normais (68 mulheres), com idades entre 17 e 87 anos. O procedimento foi completamente automatizado utilizando o método de límites e o de escolha forçada. Houve diferença significante entre os limiares obtidos no dedo indicador e no hálux nas três freqüências. Não houve diferenças significantes em relação ao sexo e grau de escolaridade; a idade apresentou discreta relação em algumas medidas. A reutilização dos eletrodos por três vezes nos dedos indicadores não comprometeu a confiabilidade, porém no hálux direito a reutilização por mais de duas vezes comprometeu a determinação do limiar para 2000Hz. Os valores obtidos diferiram das referências fornecidas pelo fabricante, nas freqüências 250Hz e 5Hz.Universidade Federal de São Paulo (UNIFESP) Setor de Neurofisiologia ClínicaUNIFESP, Setor de Neurofisiologia ClínicaSciEL

Reproducibility in nerve conduction studies and F-wave analysis

Objective: Reproducibility testing of nerve conduction studies and F-wave latencies in a group of healthy volunteers.Methods: A total of 32 healthy volunteers underwent sensory and motor nerve conduction studies of the ulnar and tibial nerves, including F-waves, elicited by 32 stimuli, repeated in two different days by the same examiner.Results: the F-wave latencies showed less variability than the other parameters of conduction studies, and, among them, the F-wave mean latency of the tibial nerve has been the one with the higher reproducibility.Conclusions: F-wave latencies were the parameters with best reproducibility, followed by conduction velocities and amplitudes.Significance: Our data showed that the F-wave mean latency is a parameter with a high reliability, considering the reproducibility, for sequential studies. (c) 2008 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.Universidade Federal de São Paulo, Dept Neurol & Neurosurg, Setor Pesquisa & Posgrad Neurofisiol Clin, SEPENC, BR-04002010 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Neurol & Neurosurg, Setor Pesquisa & Posgrad Neurofisiol Clin, SEPENC, BR-04002010 São Paulo, BrazilWeb of Scienc

Expression of praxis induction on cortical excitability in juvenile myoclonic epilepsy

Objective: This study aimed to evaluate the effects of praxis induction on sensorimotor cortical and transcallosal excitability in juvenile myoclonic epilepsy (JME). Methods: A total of 36 subjects (18-62 years) were included. The JME group was screened by video-electroencephalography neuropsychological protocol and divided into JME without praxis induction [JME-WI (n = 12)], JME with praxis-induced seizures or epileptiform discharges [JME-PI (n = 10)], and healthy controls (n = 14). Motor and somatosensory cortical excitability and transcallosal pathways were evaluated through single-pulse transcranial magnetic stimulation (sTMS) and somatosensory evoked potentials (SEPs). Results: Motor and transcallosal excitabilities tested with sTMS were not different in the motor-dominant or non-dominant hemisphere among groups. Significant differences were found in cortical SEP amplitudes in the P27 component of the non-dominant hemisphere (p = 0.03, Cohen's d = 0.98), N35 in the dominant hemisphere (p = 0.04, Cohen's d = 0.96), and P27-35 interpeak amplitude in both somatosensory cortices of the JME-PI group (p = 0.03, Cohen's d = 0.96p = 0.02, Cohen's d = 1.05) when compared with healthy controls. Giant SEPs were observed in two (16.7%) and five (50%) patients of the JME-WI and JME-PI groups, respectively. Cortical latencies did not reveal differences. Conclusions: Praxis induction was associated with enhanced excitability in the somatosensory cortex of JME patients. Significance: These findings may help clarifying the less favorable therapeutic response in the JME-PI group and indicate identifying praxis induction as an important determinant in differentiating between JME patients. (C) 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.FAPESP, Sao Paulo, BrazilUniv Fed Sao Paulo UNIFESP, Div Neurol, Dept Neurol & Neurosurg, Sao Paulo, BrazilUniv Fed Sao Paulo UNIFESP, Div Neurol, Dept Neurol & Neurosurg, Clin Neurophysiol Sect, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Neurol & Neurosurg, Unidade Pesquisa & Tratamento Epilepsias UNIPETE, BR-04024002 Sao Paulo, BrazilUniv Fed Sao Paulo UNIFESP, Div Neurol, Dept Neurol & Neurosurg, Sao Paulo, BrazilUniv Fed Sao Paulo UNIFESP, Div Neurol, Dept Neurol & Neurosurg, Clin Neurophysiol Sect, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Neurol & Neurosurg, Unidade Pesquisa & Tratamento Epilepsias UNIPETE, BR-04024002 Sao Paulo, BrazilWeb of Scienc