RESUMO
Motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) increase in amplitude when obtained immediately after a period of exercise of the target muscle (postexercise facilitation). We studied postexercise facilitation of MEPs to TMS after periods of voluntary activation of either the ipsilateral or contralateral primary motor cortex (simple finger movements) or supplementary motor area (complex finger movements). Postexercise facilitation of the first dorsal interosseous MEPs occurred ipsilaterally even after simple, unilateral finger movements of the dominant hand. The findings are taken to suggest transcallosal transfer of excitability from the dominant to nondominant cerebral hemisphere, perhaps related to mechanisms involved in bimanual motor coordination.
Assuntos
Potencial Evocado Motor/fisiologia , Exercício Físico/fisiologia , Contração Muscular/fisiologia , Adolescente , Adulto , Estimulação Elétrica , Eletromiografia , Feminino , Antebraço/inervação , Antebraço/fisiologia , Lateralidade Funcional/fisiologia , Mãos/inervação , Mãos/fisiologia , Humanos , Magnetoencefalografia , Masculino , Nervo Ulnar/fisiologiaRESUMO
Sympathetic skin responses (SSRs) have been increasingly used as tests for autonomic function in the clinical setting. In spite of the known circadian rhythmicity of sympathetic function, however, normative studies have not addressed the possibility of circadian variability of SSR parameters. Ten normal volunteers (7 men, 3 women, aged 19 to 43) had SSR testing performed in the morning, at noon, and in the early evening, and response latencies and amplitudes were compared for the different day periods. Although amplitude values varied in a random fashion, regardless of the time of testing, there was a statistically significant variability in response latencies, which were, on the average, approximately 150 ms shorter in the morning trials, as compared to the early evening ones. This difference was statistically significant (ANOVA, p < 0.01). We propose that circadian variability of SSR latencies should be taken into account in normative studies of SSR parameters.
Assuntos
Ritmo Circadiano/fisiologia , Pele/inervação , Sistema Nervoso Simpático/fisiologia , Adulto , Campos Eletromagnéticos , Eletrofisiologia , Feminino , Humanos , Masculino , Valores de ReferênciaRESUMO
The author reviews the literature on electromyography and nerve conduction velocity studies in leprosy. It is concluded that these studies can be helpful in the early diagnosis of neural involvement, in the elucidation of pathophysiological mechanisms, and in the follow-up of patients under medical and/or surgical treatment.
Assuntos
Hanseníase/complicações , Doenças do Sistema Nervoso Periférico/diagnóstico , Eletromiografia , Humanos , Hanseníase/fisiopatologia , Condução Nervosa/fisiologia , Doenças do Sistema Nervoso Periférico/etiologia , Sensibilidade e EspecificidadeRESUMO
Report on the results of regression analysis studies concerning median nerve somatosensory evoked potentials (SEPs) latencies, as dependent variables, and subject height, limb length and nerve conduction velocity (NCV), as independent variables. The tests were performed on 23 normal volunteers. Absolute SEP latencies could be predicted by a linear regression model when the independent variable was arm length; when it was subject height, however, both exponential and polynomial models proved better, the latter showing the best coefficients of determination, R 2. Multiple linear regression with two independent variables (arm length and NCV) was found to be better than simple linear regression for predicting P/N13 latency. The regression line for EP-P/N13 latency on height was found to be a polynomial curve; although the regression was found to be significant by the "F" test (alpha = 1%), the model had a low R 2 value (0.41). The same applies to the P/N13-N19 interpeak latency regression curve, but the regression was significant for alpha = 5% in that case. Although interwave latencies are the most useful parameters for clinical interpretation of median SEPs, absolute latencies may occasionally be important, and should be corrected for body size. In unusually tall subjects, it might be useful to double-check EP-P/N13 interwave latency prolongation by estimating the maximum expected P/N13 latency, using a model that takes into account both limb length and NCV.
Assuntos
Potenciais Somatossensoriais Evocados/fisiologia , Nervo Mediano/fisiologia , Constituição Corporal , Extremidades/anatomia & histologia , Humanos , Condução Nervosa , Análise de RegressãoRESUMO
Description of main abnormal findings in eight patients with a suspected diagnosis of multiple sclerosis who underwent multimodality evoked potentials studies at HDAL-SARAH--Hospital for Diseases of the Locomotor System, in Brasilia--, during three years (1987-1989). Four of those patients have also been studied with magnetic resonance imaging techniques, and in all of them the results were also typical of demyelinating disease of the central nervous system. The most useful evoked potentials were pattern-shift visual (VEP) and somatosensory (SSEP), which yielded much more information than did brainstem auditory (BAEP) components. This is in agreement with results previously described in the literature. It is concluded that multimodality evoked potentials studies are an easily obtainable and valuable diagnostic tool in multiple sclerosis.
Assuntos
Potenciais Evocados/fisiologia , Esclerose Múltipla/fisiopatologia , Adulto , Brasil , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Potenciais Somatossensoriais Evocados/fisiologia , Potenciais Evocados Visuais/fisiologia , Feminino , Humanos , Pessoa de Meia-IdadeRESUMO
The authors report the results of normative studies of pattern-shift visual, brainstem auditory and somatosensory evoked potentials of upper and lower limbs carried out in a sample of 51 normal subjects of a Brazilian population. Normal values were thus established for the main components of each modality of evoked potentials, with special emphasis on those having more clinical utility. The results were compared to the data available in the literature.
Assuntos
Potenciais Evocados/fisiologia , Adolescente , Adulto , Brasil , Eletrofisiologia , Potenciais Evocados Auditivos/fisiologia , Potenciais Somatossensoriais Evocados/fisiologia , Potenciais Evocados Visuais/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valores de ReferênciaRESUMO
The authors report a case of bilateral ptosis with miosis, paralysis of upward gaze and of smooth pursuit movements to the right, as well as a slowly regressive state of lassitude. This syndrome followed a haemorrhagic brain stem infarction. After a review of the pathophysiology of ptosis and of vertical eye movements, together with analysis of data provided by computerized tomography studies--since the case was not fatal--explanations are offered for each clinical sign and it is proposed that the lesion, a paramedian, slightly deviated to the right haemorrhagic focus in the midbrain, with a diameter of 15 mm, might have involved several structures, namely the rostral interstitial nucleus of the medial longitudinal fasciculus, the mesencephalic reticular formation, as well as cortico-nuclear and sympathetic pathways.