RESUMO
OBJECTIVE: To determine whether 5 Hz and 2000 Hz sinusoidal electric currents evoke different sensations and to indirectly evaluate which peripheral nerve fibers are stimulated by these different frequencies. METHODS: One hundred and fifty subjects chose three among eight descriptors of sensations evoked by 5 Hz and 2000 Hz currents and the results were submitted to factor analysis. In 20 subjects, reaction times to 5, 250 and 2000 Hz currents were determined at 1.1 x ST and reaction times to 5 Hz currents were also determined at 2 x ST. RESULTS: Responses were grouped in four factors: Factor 1, which loaded mainly in descriptors related to tweezers stimulation, was higher than the other factors during 2000 Hz stimulation at 1.5 x ST. Factor 2, which loaded mainly in descriptors related to needle stimulation, was higher than the other factors during 5 Hz stimulation. Factor 1 increased and Factor 2 decreased with an increase in 5 Hz intensity from 1.5 to 4x ST. Reaction times measured from the fastest responses were significantly different: 0.57 s (0.16 to 1.60), 0.34 s (0.12 to 0.71) and 0.22s (0.08 to 0.35) for 5, 250 and 2000 Hz, respectively, and 0.22s (0.11 to 0.34) for 5 Hz at 2 x ST. CONCLUSIONS: Sinusoidal electrical stimulation of 5 Hz and 2000 Hz evoke different sensations. At juxta-threshold intensities, RT measurements suggest that 2000 Hz stimulates Abeta-fibers, 250 Hz Abeta- or A partial differential-fibers, 5 Hz Abeta-, A partial differential- or C-fibers. The fiber type, which was initially stimulated by the lower frequencies, depended on inter-individual differences.
Assuntos
Estimulação Elétrica/métodos , Fibras Nervosas Mielinizadas/fisiologia , Fibras Nervosas Amielínicas/fisiologia , Tempo de Reação , Tato/fisiologia , Adolescente , Adulto , Estimulação Elétrica/efeitos adversos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dor/etiologia , Dor/fisiopatologia , Parestesia/etiologia , Parestesia/fisiopatologia , Pressão , Valores de Referência , Limiar Sensorial , Vibração , Adulto JovemRESUMO
OBJECTIVE: The aim was to compare the background activity, through quantitative EEG analysis, of patients with rolandic spikes and normal age-matched controls. MATERIAL AND METHODS: Twenty-one channel EEG of 23 children with rolandic spikes and 39 normal children, with ages ranging from 7 to 12 years, were submitted to quantitative analysis (FFT) of discharge-free epochs. Patients and controls were divided in groups according to age (7-9 and 10-12 years old). Delta, theta, alpha and beta frequency ranges were compared between groups for all electrode positions. RESULTS: Comparing normals, the 7-9 years old group showed power reduction in the alpha and beta ranges. Comparing patients and normal age-matched groups, the patients showed power increase, at all frequency ranges in the 7-9 years old group and at delta and theta frequency ranges in the 10-12 years old group. CONCLUSIONS: Our findings agree with recent evidences that these children may differ from normal (besides the eventual occurrence of seizures); but they also suggest that these differences can be related to immaturity and not necessarily related to the epileptiform discharge.
Assuntos
Encéfalo/fisiopatologia , Epilepsia Rolândica/fisiopatologia , Criança , Eletroencefalografia , HumanosRESUMO
Digital EEG (DEEG) and quantitative EEG (QEEG) are recently developed tools present in many clinical situations. Besides showing didactic and research utility, they may also have a clinical role. Although a considerable amount of scientific literature has been published related to QEEG, many controversies still subsist regarding its clinical utilization. Clinical applications are: 1. DEEG is already an established substitute for conventional EEG, representing a clear technical advance. 2. Certain QEEG techniques are an established addition to DEEG for: 2a) screening for epileptic spikes or seizures in long-term recordings; 2b) Operation room and intensive care unit EEG monitoring. 3. Certain QEEG techniques are considered possible useful additions to DEEG: 3a) topographic voltage and dipole analysis in epilepsy evaluations; 3b) frequency analysis in cerebrovascular disease and dementia, mostly when other tests have been inconclusive. 4. QEEG remains investigational for clinical use in postconcussion syndrome, learning disability, attention disorders, schizophrenia, depression, alcoholism and drug abuse. EEG brain mapping and other QEEG techniques should be clinically used only by physicians highly skilled in clinical EEG interpretation and as an adjunct to traditional EEG work.
Assuntos
Mapeamento Encefálico , Eletroencefalografia/métodos , Potenciais Evocados , Protocolos Clínicos , HumanosRESUMO
Brazilian Clinical Neurophysiology Society guidelines and pertaining comments concerning electroencephalogram (EEG) recording in suspected brain death are presented. EEG is not intended as a substitute, rather as a complement to neurologic evaluation.
Assuntos
Morte Encefálica/diagnóstico , Eletroencefalografia/métodos , Protocolos Clínicos , HumanosRESUMO
The HIV is responsible for important metabolic and structural alterations of the brain. This affected brain must react to continuous systemic metabolic fluctuations. We search for possibly resulting cerebral electric disturbance that could be found by EEG exploration. Sixty-three AIDS patients ranked as CDC group IV had their EEG background rhythm measured, and were appointed to mutually exclusiding groups delimited by medians' values of urea (24 mg/dl) and creatinine (0.9 mg/dl) seric concentrations. These groups were independently formed for each of the parameters utilized, and each data pair generated therefrom were compared between themselves to verify whether there were differences in background rhythm and the occurrence of paroxysmal activity. Background rhythm and paroxysmal activities have not statistically differed between the group whose creatinine values were lower than 0.9 mg/dl and the group whose creatinine values were equal or higher than 0.9 mg/dl. Background rhythm has not statistically differed between the group whose urea values were < 24 mg/dl and the group whose urea values were = 24 mg/dl; contrariwise, the occurrence of paroxysmal activities in these groups has significatively differed, being higher in the patient group whose otherwise normal urea values exceeded 24 mg/dl (p = 0.02).
Assuntos
Síndrome da Imunodeficiência Adquirida/metabolismo , Química Encefálica/fisiologia , Creatinina/sangue , Eletroencefalografia , Epilepsia/metabolismo , Ureia/sangue , Síndrome da Imunodeficiência Adquirida/fisiopatologia , Sistema Nervoso Central/fisiopatologia , HumanosRESUMO
Até recentemente o registro do EEG convencional era feito quase exclusivamente em papel, com a análise sendo executada visualmente. Considerando apenas a gravaçäo (aquisiçä) do EEG, pode-se atualmente dividi-la de forma arbitrária em: 1) sistemas convencionais de registro de EEG em papel; 2) sistemas híbridos com registro em papel e a presença de processadores, porém sem registro digital; os processadores podem permitir, por exemplo, a alteraçäo de programas; 3) sistemas do tipo "paperless" näo digital, com registro através de sistema de modulaçäo em "tape"; 4) sistemas de registro digital do EEG (DEEG). A análise do EEG continua sendo feita da forma visual clássica, porém o registro digital permite também executar diferentes tipos de processamento do sinal do DEEG. Estas recomendaçöes, envolvendo apenas aspectos referentes ao registro clínico digital do EEG, representam o trabalho de uma comissäo organizada pelo departamento de mapeamento topográfico da SBNC e visam näo somente delinear requisitos mínimos como também comentá-los do ponto de vista didático