Normal median near nerve potential

In routine studies of sensory nerve conduction, only fibers 37 mum in diameter are analyzed. The late components which originate from thinner fibers are not detected. This explains why a normal sensory action potential (SAP) may be recorded in patients with peripheral neuropathies and sensory loss. In the present study we investigated the late component of the median SAP with a near nerve needle electrode technique in 14 normal volunteers (7 men and 7 women), aged 34.5 + 14.8 years. The stimulus consisted of rectangular pluses of 0.2-ms duration at a frequency of 1 Hz with an intensity at least 6 times greater than the threshold value for the main component. Five hundred to 2000 sweep averagings were performed. The duration of analysis was 40 or 50 ms and the wave analysis frequency was 200 (-6 dB/oct) to 3000 Hz (-12 dB/oct). We used an apparatus with a two-channel amplifier system, 200 MW or more of entry impedance and a noise level of 0.7 muVrms or less. The main component mean amplitude, conduction velocity and lactency and the late component mean amplitude, conduction velocity and latency were respectively (mean + SD): 26.5 + 5.42 muV, 56.8 + 5.42 m/s, 3.01 + 0.31 ms, 0.12 + 0.04 muV, 16.4 + 2.95 m/s and 10.6 + 2.48 ms. More sophisticated equipment has an internal noise of 0.6 muVrms. These data demonstrate that the technique can now be employed study thin fiber neuropathies, like in leprosy, using commercial electromyographs, even in non-academic practices.

Normal median near nerve potential.

In routine studies of sensory nerve conduction, only fibers > or = 7 microns in diameter are analyzed. The late components which originate from thinner fibers are not detected. This explains why a normal sensory action potential (SAP) may be recorded in patients with peripheral neuropathies and sensory loss. In the present study we investigated the late component of the median SAP with a near nerve needle electrode technique in 14 normal volunteers (7 men and 7 women), aged 34.5 +/- 14.8 years. The stimulus consisted of rectangular pulses of 0.2-ms duration at a frequency of 1 Hz with an intensity at least 6 times greater than the threshold value for the main component. Five hundred to 2000 sweep averagings were performed. The duration of analysis was 40 or 50 ms and the wave analysis frequency was 200 (-6 dB/oct) to 3000 Hz (-12 dB/oct). We used an apparatus with a two-channel amplifier system, 200 M omega or more of entry impedance and a noise level of 0.7 microVrms or less. The main component mean amplitude, conduction velocity and latency and the late component mean amplitude, conduction velocity and latency were respectively (mean +/- SD): 26.5 +/- 5.42 microV, 56.8 +/- 5.42 m/s, 3.01 +/- 0.31 ms, 0.12 +/- 0.04 microV, 16.4 +/- 2.95 m/s and 10.6 +/- 2.48 ms. More sophisticated equipment has an internal noise of 0.6 microVrms. These data demonstrate that the technique can now be employed to study thin fiber neuropathies, like in leprosy, using commercial electromyographs, even in non-academic practices.

Regenerative changes in median nerve defects using various rabbit skeletal muscles.

We examined the morphological changes of median nerve regeneration which situated to pass through degenerative latissimus dorsi and brachial triceps muscles in rabbits. Morphological observation was performed at 7, 14, 28, 45, 60 and 180 days after the creation of defect of the bilateral median nerves. Regenerative nerve fibers were observed in the residual tubes of left degenerative muscle bridges. In this respect the regenerative effect of the latissimus dorsi was better than that of the brachial triceps. These results suggest that regular and longer muscle fibers as those of latissimus dorsi may contribute to the effective regeneration of nerve.

Electrophysiological correlates of hanseniasis.

Sensory nerve action potentials (SNAPs) and compound nerve action potentials (CNAPs) were recorded from 25 normal subjects and 21 hanseniasis patients following electrical stimulation of the median nerve at the wrist. The various nerve conduction parameters from the affected nerves of the patients were compared with those from the clinically normal nerves of patients as well as data from healthy individuals. Analysis of the data and clinical correlation studies indicate the suitability of amplitudes of the SNAPs and CNAPs rather than the nerve conduction velocities in better characterizing the neuropathy of the patients. Significantly reduced amplitudes of responses from clinically unaffected nerves of patients indicate an early stage of neuropathy, thus being of predictive value. Further, a discriminant classifier, trained on data from clinically affected nerves of patients, classified most of the data from clinically unaffected nerves of patients as abnormal. This indicates that clinical neurophysiological studies can reveal leprous neuropathy much before it becomes clinically evident by means of sensory or motor loss. A discriminant score involving only the parameters of motor threshold, amplitude of digit potential and palm nerve conduction velocity is able to classify almost all of the normal and abnormal responses. The authors hope that further confirmative studies might ultimately lead to the use of the study of distal sensory conduction in the upper limbs in possible screening of a population exposed to Mycobacterium leprae. On the other hand, misclassification of a normal person occurred and suggests that further refinement of the methods is necessary in order to facilitate wider use of the methods under field conditions.

Comparaçäo de técnicas de monitoraçäo da neuropatia hanseniana: teste de sensibilidade e estudo de conduçäo nervosa / Comparison of monitoring techniques of leprosy neuropathy: sensibility test and study of neural conduction

O trabalho compara os testes de sensibilidade e estudos de conduçao nervosa em 30 nervos, 06 medianos e 24 ulnares em pacientes com Neuropatia Hanseniana. Utilizou-se neste estudo, um "Kit"com 05 (cinco) monofilamentos de Semmes-Weinstein e um eletromiógrafo. Na avaliaçao inicial, foi detectado se os nervos avaliados apresentavam ou nao alteraçao. E nas avaliaçoes de seguimento se havia melhora, piora ou condiçao funcional inalterada. Os Estudos Estatísticos realizados demonstraram que os testes apresentam a mesma eficiência na detecçao de déficits funcionais neurológicos e monitoraçao da neuropatia hanseniana.