A New Electrophysiological Method for the Diagnosis of Extraforaminal Stenosis at L5-S1

STUDY DESIGN: A retrospective study. PURPOSE: To examine the effectiveness of using an electrodiagnostic technique as a new approach in the clinical diagnosis of extraforaminal stenosis at L5-S1. OVERVIEW OF LITERATURE: We introduced a new effective approach to the diagnosis of extraforaminal stenosis at the lumbosacral junction using the existing electrophysiological evaluation technique. METHODS: A consecutive series of 124 patients with fifth lumbar radiculopathy were enrolled, comprising a group of 74 patients with spinal canal stenosis and a second group of 50 patients with extraforaminal stenosis at L5-S1. The technique involved inserting a pair of needle electrodes into the foraminal exit zone of the fifth lumbar spinal nerves, which were used to provide electrical stimulation. The compound muscle action potentials from each of the tibialis anterior muscles were recorded. RESULTS: The distal motor latency (DML) of the potentials ranged from 11.2 to 24.6 milliseconds in patients with extraforaminal stenosis. In contrast, the DML in patients with spinal canal stenosis ranged from 10.0 to 17.2 milliseconds. After comparing the DML of each of the 2 groups and at the same time comparing the differences in DML between the affected and unaffected side of each patient, we concluded there were statistically significant differences (p<0.01) between the 2 groups. Using receiver operating characteristic curve analysis, the cutoff values were calculated to be 15.2 milliseconds and 1.1 milliseconds, respectively. CONCLUSIONS: This approach using a means of DML measurement enables us to identify and localize lesions, which offers an advantage in diagnosing extraforaminal stenosis at L5-S1.

Efeito de supressão nas vias auditivas: um estudo com os potenciais de média e longa latência / Effect of suppression in the auditory pathways: a study with middle and long latency potentials

OBJETIVO: avaliar o efeito de supressão no Potencial Evocado Auditivo de Média e Longa Latência em indivíduos sem alterações auditivas, com presença de emissões otoacústicas (EOA) transientes em ambas as orelhas. MÉTODOS: foram avaliados 25 indivíduos (50 orelhas) de 18 a 30 anos de idade, de ambos os sexos, utilizando-se os Potenciais Evocados Auditivos de Média e Longa latência sem e com ruído branco contralateral. Os sujeitos não apresentavam queixa relacionada ao Processamento Auditivo. Foram verificados e comparados os valores numéricos das latências e amplitudes das ondas na avaliação convencional sem ruído e com ruído contralateral. RESULTADOS: a média aritmética da amplitude de resposta na situação com ruído (mascaramento) reduziu em todas as posições (C3/A1, C4/A1, C3/A2 e C4/A2), porém estes achados foram estatisticamente significantes nas posições C4/A1, C3/A2 e C4/A2. CONCLUSÃO: a diminuição da amplitude pode ter relação com o número de sinapses realizadas. O efeito de supressão na amplitude pode estar relacionado à ação do sistema eferente que suprime o número de sinapses neuronais.

PURPOSE: to evaluate the suppression effect of the Middle Latency Response (MLR) and Long Latency Potential on normal hearing individuals. METHODS: twenty-five individuals of both genders between 18 and 30-year old were evaluated (50 ears), with presence of OAE in both ears (thus, excluding any middle ear problem or hearing loss that could compromise the final evaluation). The individuals did not present any complain on the Auditory Processing. We used MLR and P300 with and with no contralateral white noise. The latency and amplitude of the waves were evaluated (with and with no noise) and the results were compared. RESULTS: we found reduction in the median amplitude in the situation with noise (masking) in all positions (C3/A1, C4/A1, C3/A2 and C4/A2). However, these findings had no statistically significant difference in the positions C3/A1. CONCLUSION: the effect of the suppression on the amplitude could be linked to the efferent system that decreases the number of neuronal synapses.