Concentric Needle Jitter in 97 Myasthenia Gravis Patients.

Objectives: To estimate the jitter parameters (single-fiber electromyography) in myasthenia gravis patients mostly by electrical activation in Frontalis, Orbicularis Oculi, and Extensor Digitorum muscles using a concentric needle electrode. Methods: Between 2009 and 2019, a total of 97 myasthenia gravis patients, 52 male, and mean age 54 years were included. Results: Any abnormal jitter parameter in individual muscles was 90.5% (Frontalis), 88.5% (Orbicularis Oculi), and 86.6% (Extensor Digitorum). Any jitter parameter combining Orbicularis Oculi and Frontalis muscle was abnormal in 100% for the ocular, and in 92.9% for the generalized myasthenia gravis. The most abnormal muscle was Orbicularis Oculi for the generalized, and Frontalis for the ocular myasthenia gravis. The decrement was abnormal in 78.4%, 85.9% for the generalized, and 25% for the ocular myasthenia gravis. The mean jitter ranged from 14.2 to 86 µs (mean 33.3 µs) for the ocular myasthenia gravis and from 14.4 to 220.4 µs (mean 66.3 µs) for the generalized myasthenia gravis. The antibody titers tested positive in 86.6%, 91.8% for the generalized, and 50% for the ocular myasthenia gravis. Thymectomy was done in 48.5%, thymoma was found in 19.6%, and myasthenic crisis occurred by 21.6%. Conclusion: The jitter parameters achieved a 100% abnormality in ocular myasthenia gravis if both the Orbicularis Oculi and Frontalis muscles were tested. There was a high jitter abnormality in generalized myasthenia gravis cases with one muscle tested, with about a 2% increase in sensitivity when a second is added. Concentric needle electrode jitter had high sensitivity similar to the single fiber electrode (93.8%), followed by antibody titers (86.6%), and abnormal decrement (78.4%).

Problems in Comparing Jitter Values Obtained with Voluntary Activation and Electrical Stimulation.

Comparing results from jitter studies performed with voluntary and electrical activation is difficult to perform quantitatively, particularly in complex signals as seen in reinnervation. High jitter values in individual spikes in these multispike signals can be missed with both activation methods, which introduces a bias towards more normal values.With voluntary activation, triggering on a spike from an abnormal end-plate in multispike potentials will overestimate individual jitter values and the number of abnormal jitter values.With electrical stimulation, artefactually-increased jitter may be caused by subliminal stimulation, which causes uncertainty at the stimulation point. Electrical stimulation also may activate many axons, causing signal summation, with erroneous or impossible jitter estimation.Awareness of such pitfalls can improve the correct performance and interpretation of jitter recordings. Quantitative comparisons of results can be made between studies in reinnervated muscle performed with the same activation method, but not between results obtained with different activation methods.

Time perception and age.

UNLABELLED: Our internal clock system is predominantly dopaminergic, but memory is predominantly cholinergic. Here, we examined the common sensibility encapsulated in the statement: "time goes faster as we get older". OBJECTIVE: To measure a 2 min time interval, counted mentally in subjects of different age groups. METHOD: 233 healthy subjects (129 women) were divided into three age groups: G1, 15-29 years; G2, 30-49 years; and G3, 50-89 years. Subjects were asked to close their eyes and mentally count the passing of 120 s. RESULTS: The elapsed times were: G1, mean = 114.9 ± 35 s; G2, mean = 96.0 ± 34.3 s; G3, mean = 86.6 ± 34.9 s. The ANOVA-Bonferroni multiple comparison test showed that G3 and G1 results were significantly different (P < 0.001). CONCLUSION: Mental calculations of 120 s were shortened by an average of 24.6% (28.3 s) in individuals over age 50 years compared to individuals under age 30 years.

Time perception and age / Percepção do tempo e idade

ABSTRACT Our internal clock system is predominantly dopaminergic, but memory is predominantly cholinergic. Here, we examined the common sensibility encapsulated in the statement: “time goes faster as we get older”. Objective To measure a 2 min time interval, counted mentally in subjects of different age groups. Method 233 healthy subjects (129 women) were divided into three age groups: G1, 15-29 years; G2, 30-49 years; and G3, 50-89 years. Subjects were asked to close their eyes and mentally count the passing of 120 s. Results The elapsed times were: G1, mean = 114.9 ± 35 s; G2, mean = 96.0 ± 34.3 s; G3, mean = 86.6 ± 34.9 s. The ANOVA-Bonferroni multiple comparison test showed that G3 and G1 results were significantly different (P < 0.001). Conclusion Mental calculations of 120 s were shortened by an average of 24.6% (28.3 s) in individuals over age 50 years compared to individuals under age 30 years.

RESUMO Nosso sistema de relógio interno é predominantemente dopaminérgico, mas a memória é predominantemente colinérgica. Neste estudo, examinamos a assertiva comum que “o tempo passa mais rápido para pessoas mais velhas”. Objetivo Medir o intervalo de tempo 2 min contados mentalmente em pessoas de diferentes faixas etárias. Método 233 pessoas saudáveis (129 mulheres) foram divididos em três grupos: G1, 15-29 anos; G2, 30-49 anos; e G3, 50-89 anos. Foi solicitado que contassem mentalmente, com os olhos fechados, a passagem de 120 s. Resultados Os tempos aferidos foram: G1, média = 114,9 ± 35 s; G2, média = 96,0 ± 34,3 s; G3, média = 86,6 ± 34,9 s. A comparação entre os tempos de G3 e G1 (teste de comparação múltipla ANOVA-Bonferroni) foi muito significante (P < 0,001). Conclusão Cálculo mental de 120 s foi encurtado em média 24,6% (28,3 s) em pessoas maiores que 50 anos quando comparado com pessoas menores que 30 anos.