Current perception threshold: reaction times to 5, 250 and 2000 Hz sinusoidal electrical stimulation

Objective: to measure reaction times (RT) to different frequencies of electrical sinusoidal current stimulation. Methods: RTs were measured from 20 healthy volunteers (7 men). Electrical sinusoidal currents of 5, 250 and 2000 Hz at 1.1 sensory thresholds (ST) and also at 2ST for 5 Hz, were applied to the left index finger; responses were measure through the EMG responses of the right indicis proprius muscle. Results: The mean RT (range) obtained from fastest responses were significantly different, 0.57 (0.16 to 1.60) s, 0.34 (0.12 to 0.71) s and 0.22 (0.08 to 0.35) s, for responses to 5, 250 and 2000 Hz respectively and for 5 Hz at 2ST 0.22 (0.11 to 0.34) s. Conclusion: At. 1.1ST the RT elicited by sinusoidal electrical currents at different frequencies are mediated by different spectrum of fibers suggesting that 2000 Hz stimulates Aâ fibers, 250 Hz Aâ or Aä fibers, 5 Hz Aâ, Aä or C fibers and 5 Hz at 2ST stimulates Aâ fibers. Significance: Different frequencies of stimulation may activate different fibers: 2000 Hz (1.1ST) and 5 Hz (2ST) Aâ fibers, 250 Hz (1.1ST) Aâ or Aä fibers and 5 Hz (1.1ST) Aâ, Aä or C fibers. What fiber is initially stimulated by the lower frequencies depended on the subject studied. Key words: sensations, electrical stimulation, current perceptions threshold (CPT)Objetivo: diferenciar qual tipo de fibra nervosa esta sendo estimulada por correntes eletricas senoidais com frequencias de 5, 250 e 2000 Hz atraves da mensuracao do tempo de reacao (TR). Metodos: TRs foram medidos em 20 individuos voluntarios saudaveis (7 homens). Correntes eletricas senoidais de 5, 250 e 2000 Hz a 1,1 vezes o limiar de percepcao de corrente eletrica (LS) e tambem a 2,0LS para 5 Hz, obtidos atraves dos metodos de limites e de escolha forcada, foram aplicados no dedo indicador esquerdo; respostas foram medidas atraves do registro eletromiografico (EMG) no musculo extensor proprio do indicador direito. Resultados: os TRs medios obtidos das respostas mais rapidas foram significativamente diferentes, 0,57 (0,16 a 1,60), 0,34 (0,12 a 0,71) e 0,22 (0,08 a 0,35) segundos, para respostas a 5, 250 e 2000 Hz respectivamente, e para 5 Hz a 2,0LS foi de 0,22 (0,11 a 0,34) segundos. Conclusao: a 1,1LS os TRs obtidos por correntes eletricas senoidais em diferentes frequencias sao mediadas por diferentes espectros de fibras, sugerindo que 2000 Hz estimula fibras AƒÀ, 250 Hz fibras AƒÀ ou AƒÂ, 5 Hz AƒÀ, AƒÂ ou C, e 5 Hz 2,0LS estimula fibras AƒÀ. Significancia: diferentes frequencias de estimulacao podem ativar diferentes fibras: 2000 Hz (1,1LS) e 5 Hz (2,0LS) fibras AƒÀ, 250 Hz (1,1LS) fibras AƒÀ ou AƒÂ e 5 Hz (1,1LS) fibras AƒÀ, AƒÂ ou C. Qual fibra e inicialmente estimulada por frequencias baixas dependem do individuo avaliado.TEDEBV UNIFESP: Teses e dissertaçõe

Cerebral venous thrombosis and homocystinuria: case report

Homocystinuria presenting as cerebral venous thrombosis is not usual. We report on a 13-year-old boy who was admitted to the hospital due to severe headache, nausea, vomiting and fever (38ºC). The patient was Marfan like and presented left hemiparesis and meningeal irritation sings. He was mentally retarded, had severe myopia, and had right lens dislocation one month before. Cranial CT scan was suggestive of cerebral venous infarct. MRI and magnetic resonance angiography showed venous infarcts more prominent in the right thalamic projection with hemorrhagic transformation and multiple foci of cortical (occipital and parietal bilaterally) deep parietal and left capsular bleeding, secondary of thrombosis of the transverse and sigmoid venous sinuses. High levels of homocysteine were detected in the blood and urine. Homocystinuria is an autossomal recessive inborn error of methionine metabolism caused by cystathione-ß-synthase defect in most cases. We discuss the clinical and radiological findings in this patient, analyzing the pathophysiology of the thrombotic events related to homocystinuria.Homocistinúria apresentando-se como trombose venosa cerebral é incomum. Relatamos o caso de um adolescente com características fenotípicas de homocistinúria que foi admitido por cefaléia intensa, vômitos e sonolência. Investigação diagnóstica com tomografia computadorizada de crânio, ressonância magnética e angiorressonância foi compatível com trombose dos seios transversos e sigmóides. Altos níveis de homocisteína foram detectados no sangue e na urina. Apresentamos os aspectos clínicos e radiológicos deste caso discutindo a controversa fisiopatologia da tendência trombofílica associada a homocistinúria.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Disciplina de Neurologia ClínicaUNIFESP, EPM, Disciplina de Neurologia ClínicaSciEL

Moving ear syndrome: The role of botulinum toxin

We report a 30-year-old man with moving ear syndrome caused by focal myoclonic jerks of the right temporal muscle. This focal myoclonus would disappear while the patient was sleeping, swallowing, or speaking. He was treated with botulinum toxin type A with a favorable outcome. Previous reports of this condition and possible therapeutic approaches are discussed. (c) 2007 Movement Disorder Society

Sensations and reaction times evoked by electrical sinusoidal stimulation

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 reaction times to 5, 250 and 2000 Hz currents were determined at 1.1xST and reaction subjects, times to 5 Hz currents were also determined at 2xST.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 1.5xST. 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 4xST. 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 0.22 s (0.08 to 0.35) for 5, 250 and 2000 Hz, respectively, and 0.22 s (0.11 to 0.34) for 5 Hz at 2xST.Conclusions. - Sinusoidal electrical stimulation of 5 Hz and 2000 Hz evoke different sensations. At juxta-threshold intensities, RT measurements suggest that 2000 Hz stimulates A beta-fibers, 250 Hz A beta- or A partial derivative-fibers, 5 Hz A beta-, A partial derivative- or C-fibers. the fiber type, which was initially stimulated by the lower frequencies, depended on inter-individual differences. (C) 2009 Elsevier Masson SAS. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Federal de São Paulo, BR-04120050 São Paulo, BrazilUniversidade Federal de São Paulo, BR-04120050 São Paulo, BrazilFAPESP: 05337-6CNPq: 478476/2004-3Web of Scienc