Background: Nerve conduction study (NCS) is the simple noninvasive technique to assess the functional status of peripheral nerves. Physiological variables such as age, sex, anthropometric indices influence the functional status of peripheral nerves. Hence, this study was designed to assess the effect of age on motor NCS. Materials and Methods: A cross-sectional study was done among healthy adults of different age group to observe the effect of age on nerve conduction. Ninety-eight healthy study participants were selected for this study after getting due approval from ethics committee of the institution. Motor NCS was performed with the standard procedure by trained technician under supervision of neurologists. Median, ulnar, posterior tibial, and common peroneal nerve (CPN) were studied for compound motor action potential. All study participants were classified into three groups according to their age, i.e., Group A (20–35 years), Group B (36–50 years), and Group C (>50 years). Statistical test one way ANOVA was used to analyze the data. Results: Distal latency of older age group participants was prolonged than younger age group. Amplitude in older age group participants was less than younger age group only in median and CPN. Conduction velocity in older age group is less in comparison to younger age group. Conclusion: This study opined age has substantial role in NCS of healthy subjects. Hence, age reference data of motor NCS are helpful for the evaluation of functional status of motor nerves.
Keywords: Amplitude and conduction velocity, compound motor action potential, distal latency
|How to cite this URL:|
Jena SK, Acharya M. Age variation of motor nerve conduction study in healthy adults: A physiological reference. APIK J Int Med [Epub ahead of print] [cited 2022 Sep 25]. Available from: https://www.ajim.in/preprintarticle.asp?id=353265
| Introduction|| |
Peripheral nerves behave like electric wires which carry signals or impulses from one part to other parts of the body. The functional status of peripheral nerves and their disorders is determined by nerve conduction studies. Physiological factors such as age, sex, height, weight, and temperature affects different parameters of nerve conduction studies.,,, Aging process is accompanied by slowness of muscle contraction, muscle metabolism reduction, and conduction velocity (CV). Scientists have reported that the conduction velocities of both motor and sensory nerves in newborn were 40%–50% of adult values. Adult value of CV is attained at 3 years of age both in motor and sensory nerves. Nerve conduction study (NCS) is a very simple non-invasive technique, on routine basis, it is used for diagnosis and evaluation of prognosis of nerve injury and neuropathies. Several studies have reported normative data according to age and gender. Body composition of population varies from one region to other according to their demographic profile. Hence, normative reference data have their own importance to evaluate functional status of peripheral nerves. Most of studies have reported that ageing can alter the parameters of nerve conduction studies, but at which age this alteration occurs has not been mentioned.,, Hence, this study aimed to determine the impact of age on nerve conduction parameters and to provide normative reference data of nerve conduction studies in the eastern part of India.
| Materials and Methods|| |
This study included 98 apparently healthy study participants (58 males and 40 females) of the age group between 20 and 60 years. Apparently healthy means neither they had any complain of symptoms of disease nor any clinical findings were recorded on examination. This study was a collaboration study between the Department of Neurology and Physiology in a Health Institute in Eastern India. Institutional Ethics Committee Approved this prospective cross-sectional study and completed between September 2020 and August 2021. Study participants were well explained the protocol and the output of study very well. Study participants had signed the written consent form before enter into the study. Accompanying healthy persons with patients to neurology department, patients' relatives and volunteers of local public were selected as study participants for this study. The screening of study population was done by routine general and clinical examination and study participants were selected. Persons having normal general and neurological examination, no sensory abnormalities, intact sensory system, and no past history of long-term treatment which can cause neuropathy were selected as study participants. Persons having habit of sitting cross-legged on the floor for long-duration, history of diabetes mellitus, lumbosacral radiculopathy, trauma, history of sensory abnormalities, and on drug history were excluded from the study. The study participants were classified into three groups by their age, i.e., Group A – 20–35 years, Group B – 36–50 years, and Group C – >50 years. Minimum sample size was estimated using the standard formula for the estimation of population mean.
Technique of recording compound motor action potential
Study participants were well explained detail about the technique of recording nerve conduction for their cooperation. To reduce the impedance of skin, the stimulating and recording sites were cleaned by rectified spirit. Medicaid Neurostim machine was used for NCS. Filters were set between 20 Hz and 2 kHz, sensitivity was 5 mV/divisions and sweep duration was 5 ms. The temperature of the laboratory was maintained between 21°C and 23°C and skin temperature of limbs was maintained at 34°C approximately. Trained technicians under the guidance of neurologists conducted the test. Supramaximal stimulus was applied to obtain the recording of compound motor action potential (CMAP). The latency in milliseconds was recorded from the onset of sweep to the onset of negative peak of CMAP wave form. The amplitude of CMAP in millivolt was obtained from peak to peak. CV was calculated from distance and time recording of CMAP.
Recording of median nerve compound motor action potential
Recording electrode was put halfway between 1st metacarpophalangeal joint and midpoint of distal wrist crease. Reference electrode was put just distal to 1st metacarpophalangeal joint. Ground electrode was put on dorsum of hand. First stimulation point was at 8 cm proximal to recording electrode in a line to the midpoint of distal wrist crease. Second stimulation point was at anticubital fossa just medial to brachial artery.
Recording of ulnar nerve compound motor action potential
Recording electrode was put on the ulnar surface of hypothenar eminence halfway between pisiform bone and 5th metacarpophalangeal joint. Reference electrode was put immediate distal to 5th metacarpophalangeal joint. Ground electrode was put on dorsum of hand. First stimulation point was at 8 cm proximal to recording electrode along the line slightly radial to flexor carpi ulnaris tendon. Second stimulation point was at 4 cm distal to medial epicondyle.
Recording of common peroneal nerve compound motor action potential
Recording electrode was put at midpoint of extensor digitorum brevis on the dorsum of foot. Reference electrode was put just distal to 5th metatarsophalangeal joint. Ground electrode was put over the dorsum of foot. First stimulation point was 8 cm proximal to recording electrode lateral to tendon of tibialis anterior. Second stimulation was just posterior and inferior to fibular head.
Recording of posterior tibial nerve compound motor action potential
Recording electrode was put on medial side of foot just anterior and inferior to navicular tubercle. Reference electrode was put distal to 1st metatarsophalangeal joint on medial side. Ground electrode was put on dorsum of foot. First stimulation point was 8 cm proximal to recording electrode just posterior to medial malleolus. Second stimulus was at mid popliteal fossa.
Data were analyzed using IBM SPSS 20 version (IBM Corporation, Armonk, New York, USA). Data of distal latency (DL), amplitude (Amp) and CV of CMAP of median, ulnar, PTN, and common peroneal nerve (CPN) were analyzed between group A, B, and C. Statistical test one-way ANOVA was used for this study. P < 0.05 was considered to be statistically significant.
| Results|| |
This study comprised 98 healthy study participants of both male and female gender. We analyzed different components of CMAP of median, ulnar, common peroneal, and posterior tibial nerve (PTN) of study participants.
[Table 1] represents the DL of CMAP of motor NCS. Mean latency of median nerve was 2.80 ± 0.63, 2.87 ± 0.51, 3.04 ± 0.66 ms in Group A, B and C respectively at significant variation (P = 0.04). Mean latency of ulnar nerve was 1.90 ± 0.36, 2.25 ± 0.44, and 2.37 ± 0.64 ms in Group A, B, and C, respectively, at significant variation (P = 0.024). The mean latency of PTN was 3.85 ± 0.96, 4.25 ± 1.00, 4.77 ± 1.11 ms in Group A, B, and C, respectively, at significant variation (P = 0.03). Mean latency of CPN was 3.32 ± 0.78, 3.32 ± 1.08, and 4.21 ± 1.41 ms in Group A, B, and C, respectively, at significant variation (P = 0.04).
[Table 2] represents the amplitude of CMAP motor NCS. Mean amplitude of median nerve was 14.1 ± 4.8, 14 ± 3.3, and 9.2 ± 3.5 mili volt in Group A, B, and C, respectively, at significant variation (P = 0.007). Mean amplitude of ulnar nerve was 9 ± 3.5, 8.5 ± 3.4, and 8.3 ± 2.7 mili volt in Group A, B, and C, respectively, which was not significant (P = 0.84). Mean amplitude of PTN was 6.08 ± 3.7, 6.14 ± 4, and 8.09 ± 5 mili volt in group A, B, and C, respectively, which was not significant. Mean amplitude of CPN was 2.99 ± 1.3, 4.77 ± 3.1, and 6.07 ± 3.5 mili volt in Group A, B, and C, respectively, at significant variation (P = 0.046).
[Table 3] represents the CV of CMAP motor NCS. Mean CV of median nerve was 54.4 ± 6.3, 53.6 ± 6.2, and 51.6 ± 4.9 m/s in group A, B, and C, respectively, at significant variation (P = 0.043). Mean CV of ulnar nerve was 60.2 ± 10, 58 ± 4.9, 57 ± 6 m/s in Group A, B, and C, respectively, at significant variation (P = 0.031). Mean CV of PTN was 46.9 ± 4.5, 44 ± 5.3, and 40 ± 5.7 m/s in Group A, B, and C, respectively, at significant variation (P = 02). Mean CV of CPN was 48.7 ± 3.3, 47.3 ± 6.1, and 47.5 ± 4.0 m/s in Group A, B, and C, respectively, at significant variation (P = 0.041).
| Discussion|| |
Several factors such as age, height, and body mass index influence the CMAP as reported by several researchers.,, Aging is a natural process of life associated with body function impairment leading to age-related diseases. Due to several effects of aging, there is chance of nerve conduction variation with respect to age. Our study aimed to find the effect of aging on nerve conduction.
We analyzed CMAP study of median nerve, ulnar nerve, PTN, and CPN. In our study, we found the trend of increasing latency duration with age significantly. The latency duration of older age group was more than the younger age group in all four nerves we studied. There was a trend of decreasing amplitude with age in median nerve and CPN at a significant level. The amplitude of older age group was less than the younger age group in median nerve and CPN. The CV of all the four nerves was in the trend of decreasing with age. The CV of older age group was lower than the younger age group.
Kumari et al. in their study reported that there was a prolongation of latency with aging. A similar result was obtained in our study. In aging prolongation of latency was due to loss of nerve fibers (both myelinated and unmyelinated) in peripheral nerves. Previous studies suggested that the CV of motor nerves decrease when a person attend about an age of 40 years which simulates to our studies.,, Some other studies reported that CV of motor nerves decrease by the age of 30–40 years which simulates to our studies.,,, Other researchers found that CV decreases at about 60–80 years of age.,, This finding was not supportive to our study as we got a trend of decreasing CV at an early age of about 40 years. One study reported negative correlation between age and parameters of NCS. In another study, researchers reported negative correlation between age and amplitude of NCS and this result is in similar trend to our study. Age has substantial contribution toward the duration of motor nerve action potential. Each nerve has specific timing of ageing. Hence, adjustment of age is necessary to get a satisfactory result of sensitivity and specificity of nerve conduction studies when applied the same reference data to patients of different age groups.,, During the process of aging, oxygen-free radicals increase leading to damage the enzyme system in mitochondria causing less ATP formation which contributes to altered motor nerve functioning.,, Loss of myelinated as well as unmyelinated nerve fibers in peripheral nerves play crucial role in alteration of different parameters of CMAP.
Limitations of study
This study could not able to find the effect of other demographic factors such as sex, height, weight on nerve conduction studies. Linear regression analysis could be applied for better analysis.
| Conclusion|| |
This study suggested age is one of the most important factors which influence the motor nerve conduction. Hence, age reference data are essential to diagnose the peripheral nerve diseases and their prognosis.
Authors are very much thankful to laboratory technicians of the neurology department of the institute for their support toward this study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Sunil Kumar Jena,
Department of Physiology, Veer Surendra Sai Institute of Medical Sciences and Researches, Burla - 768 017, Odisha
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2], [Table 3]