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ORIGINAL ARTICLE

NERVE CONDUCTION STUDY AMONG HEALTHY MALAYS. THEINFLUENCE OF AGE, HEIGHT AND BODY MASS INDEX ON

MEDIAN, ULNAR, COMMON PERONEAL AND SURAL NERVES

Mohamed Saufi Awang*, Jafri Malin Abdullah*, Mohd Rusli Abdullah**, John Tharakan*, AtulPrasad*, Zabidi Azhar Husin*, Ahmad Munawir Hussin*, Adnan Tahir* and Salmi Abdul Razak*

Department of Neurosciences*, Department of Community Medicine**School of Medical Sciences, Universiti Sains Malaysia

16150 Kubang Kerian, Kelantan, Malaysia

Nerve conduction study is essential in the diagnosis of focal neuropathies and diffusepolyneuropathies. Age, height and body mass index (BMI) can affect nerve velocitiesas reported by previous studies. We studied the effect of these factors on median,ulnar, common peroneal and sural nerves among healthy Malay subjects. Weobserved slowing of nerve conduction velocities (NCVs) with increasing age andBMI (except ulnar sensory velocities). No demonstrable trend can be seen acrossdifferent height groups except in common peroneal nerve.

Key words : nerve conduction velocity (NCV), nerve conduction study (NCS)

Introduction

Nerve conduction velocities (NCVs) can beeasily measured on peripheral nerves. Sufficientstimuli from an electrical stimulator can trigger nerveimpulses. Once the action potential threshold of anerve fiber is reached, its electrical impulses will

propagate at a rate of hundred metres per second(1,2). The velocity is directly dependent on thediameter of fibre myelination and temperature(8,15).

Nerve conduction study (NCS) helps indelineating the extent and distribution of neurallesions. It enables clinicians to differentiate the two

Submitted-10.10.2004, Accepted-24.11.2005

Malaysian Journal of Medical Sciences, Vol. 13, No. 2, July 2006 (19-23)

Table 1 : Showing different age, BMI and height groupsAge (years)

BMI(kg/m2)

Height(cm)

Group 1. 20-29Group 2. 30-39Group 3. 40-49Group 4. 50-59

Group 1. < 18.9Group 2. 19-24.9Group 3. 25-29.9Group 4. > 30

Group 1. < 160Group 2. 160-169Group 3. 170-179Group 4. > 180

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major groups of peripheral diseases: demyelinationand axonal degeneration (9)

Orthodromic is when the propagation ofaction potential is recorded in the physiologicaldirection whereas antidromic is when the recordingis opposite to the physiological direction (7).

Median and ulnar nerves are two importantnerves in the upper limb. They are responsible forthe movements as well as sensation of the hand.Entrapment of these nerves will cause reduction inthese modalities, for instance in carpal tunnelsyndrome. Nerve conduction study (NCS) helps inlocalizing the site of the lesion (6, 17). The common

peroneal and sural nerves are among the nervescommonly studied in the lower limbs. They supplysome of the muscles and cutaneous sensation of thelower limbs (4).

There are many studies which evaluate theinfluence of specific personal factors such as age,height and body mass index on nerve velocities(5,16,20). However, the majority of these studiesare based on Caucasian subjects.

Therefore, this study is designed to study theeffect of these specific factors (age, height and BMI)on NCVs of median, ulnar, common peroneal andsural nerves among healthy Malay subjects.

Table 2 : The sites of stimulation and recording of the nerves

Table 3 : Conduction velocities of median and ulnar nerves for both motor and sensory, across differentages, BMIs and height groups

Mohamed Saufi Awang, Jafri Malin Abdullah et. al

Nerve

Median

Stimulation Recording

MotorSensory

Wrist, ElbowWrist

Thenar muscleIndex finger

UlnarMotorSensory

Wrist, ElbowWrist

Hypothenar muscleLittle finger

Common PeronealMotor Ankle, Fibula Head Extensor digitorum brevis

SuralSensory Calf Lateral malleolus

Median Ulnar

Age Groups

ConductionMotor (m/s)

ConductionSensory (m/s)

ConductionSensory (m/s)

ConductionMotor (m/s)

BMI (kg/m2)

Height (cm)

1234

1234

1234

57.56 ± 5.7055.97 ± 4.3254.21 ± 5.2650.95 ± 5.28

57.00 ± 5.3654.81 ± 5.6753.89 ± 5.3752.15 ± 6.09

54.09 ± 5.8555.68 ± 4.7953.89 ± 6.4255.05 ± 5.63

56.49 ± 6.1554.55 ± 7.4652.73 ± 5.6752.30 ± 7.90

56.16 ± 6.3553.79 ± 6.8153.66 ± 7.2952.78 ± 8.36

52.45 ± 7.8853.90 ± 6.0454.77 ± 6.7855.03 ± 7.27

62.15 ± 4.6860.78 ± 6.0960.25 ± 4.4359.05 ± 4.13

61.39 ± 5.1460.92 ± 5.2459.39 ± 7.2959.00 ± 4.76

61.38 ± 5.5859.89 ± 4.9460.58 ± 4.6660.55 ± 4.78

53.87 ± 6.3352.99 ± 7.1352.87 ± 4.7852.74 ± 4.97

52.21 ± 5.2452.47 ± 6.1153.92 ± 5.6754.15 ± 6.17

52.19 ± 5.7952.40 ± 5.2653.37 ± 5.3653.78 ± 7.07

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Methods

Two hundred and fifty subjects were recruitedin this study . They were hospital staff includingdoctors, nurses, medical assistants and attendants.The age, sex, height and weight of the subjects wererecorded. Subjects were divided into different age,body mass index (BMI) and height groups as shownin Table 1. All the subjects do not suffer from anyknown neuromuscular or musculoskeletal diseases.The ethical approval for the study was obtained fromthe ethical committee.

The nerves tested were the median ,ulnar,common peroneal and sural nerves (both right andleft). The sites of stimulation and recording areshown in the Table 2. In each subject, orthodromicmotor and antidromic sensory parameters of thenerves were measured.

We used surface electrodes. The recordingelectrodes were fixed to the subject’s skin usingadhesive tape. No special skin preparation wasneeded. The targeted nerve was supramaximallystimulated using a square wave current with aduration of 0.2ms and the action potential was pickedup by the recording electrode. The length of eachnerve was estimated with a flexible measuring tape.For safety, a ground electrode was placed in betweenthe stimulating and recording electrodes. The roomtemperature was kept constant above 29º C for upperextremities and 27º C for lower extremities andmeasured using a room thermometer.

Results

Of 250 subjects, 137 subjects (55%) weremale and 112 (45%) were females. The average age,height and BMI were 34.38 ± 10.79, 159.45± 8.53(cm) and 24.01± 4.20 (kg/ m2 ) respectively.

The mean velocities for median and ulnarnerves both motor and sensory were: 54.71± 5.69m/s (motor) and 54.04±7.02m/s for the median nerveand 60.57± 5.00 m/s (motor) and 52.92± 5.89 m/sfor the ulnar nerve. The mean velocities for thecommon peroneal (motor) and sural (sensory) nerveswere 50.73± 4.60m/s and 47.97± 4.48m/srespectively.

The conduction velocities of median and ulnarnerves, both motor and sensory across different age,BMI and height groups are summarized in Table 3and for common peroneal and sural nerves, theconduction velocities are tabulated in Table 4.

Discussion

Nerve conduction study is an importantmethod used in clinical practice and has beenthoroughly validated (1,2,3,11,14).There are manystudies and reviews on nerve conduction studies thathave been published. These include the factors thataffect nerve velocities. These factors can be dividedinto biological factors (age, height, gender) andphysical factors which are related to the physical

NERVE CONDUCTION STUDY AMONG HEALTHY MALAYS. THE INFLUENCE OF AGE, HEIGHT AND BODY MASS INDEX ON MEDIAN, ULNAR, COMMON PERONEAL AND SURALNERVES

Table 4 : Conduction velocities of common peroneal (motor) and sural (sensory) nervesacross different ages, BMIs and height groups

Common Peroneal Sural

Age Groups

Conduction Motor (m/s)

Conduction Sensory (m/s)

BMI (kg/m2)

Height (cm)

1234

1234

1234

51.95 ± 4.1151.69 ± 4.2850.17 ± 4.3749.13 ± 4.01

51.00 ± 5.1050.97 ± 4.2150.43 ± 3.7950.20 ± 5.12

51.46 ± 4.7950.78 ± 4.0550.65 ± 4.1850.15 ± 4.29

48.29 ± 3.8648.22 ± 4.5848.06 ± 4.5347.32 ± 4.47

49.00 ± 4.7048.63 ± 4.0048.17 ± 4.7248.00 ± 4.69

47.90 ± 4.4548.13 ± 4.9847.85 ± 3.8848.02 ± 4.07

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state of the nerve and muscle (10, 15,16). Our focuswas on the effect of biological factors (age, heightand BMI) on NCV. Other factors like temperaturefor instance was kept at the recommended level bymost neurophysiology laboratories in order to reducevariabilities.

Flack et al (7) described that age has asignificant effect on sensory nerve conduction. Theconduction velocity in newborns is approximately50% of adult values and progressively increases andreaches the adult value at the age of three. Later inadulthood , the nerve velocity decreases with age,more so in the lower than upper limbs. A similarobservation was made by Stalberg and Flack (15)for motor nerve conduction.Tong et al (19) in theirstudy on the effect of aging on sensory NCV notedthat the rate of change in parameters wassignificantly greater in the median nerve than withulnar nerve.

Our study showed slowing of nerve velocitieswith increasing age in the median nerve. Similarobservations were noted both in the motor andsensory velocities of the ulnar nerve. We alsoobserved a similar trend of velocities with increasingage in both the common peroneal and sural nerves.

Many studies have shown that NCV bothmotor and sensory are relatively slower in tallersubjects. It is estimated that the velocity decreasesby 2-3 m/s per 100mm in height (7,8,13,16,21, 22).

Soudmand et al (18) found that peroneal andsural nerves conduction velocities were correlatedinversely with height and no significant relationshipcould be seen in median nerve(both motor andsensory) NCV. In comparison, we could notdemonstrate any obvious trend of NCVs in medianand ulnar nerves across different height groups. Weobserved slowing of NCVs in common peronealnerve with increasing height. However, nodemonstrable patterns were seen for the sural nerve.

Buschbacher (1) performed a study todetermine the effect of body mass index on NCV.The investigator concluded that there was nocorrelation note between BMI and NCV plus Hreflex latency. We found slowing of NCVs acrossdifferent BMI groups. In median nerve, both motorand sensory conduction showed reduction in thevelocities with increasing BMI. The motorconduction velocities in the ulnar nerve also showedsimilar pattern. However, no observable trend canbe seen in the sensory conduction velocities of theulnar nerve. We observed slowing of conductionvelocities with increasing BMI for both commonperoneal and sural nerves.

In conclusion, age and BMI can affect theconduction velocities. We observed reduction invelocities of the median, ulnar (except sensoryconduction), common peroneal and sural nervesacross different age and BMI groups. Further studiesare needed to clarify the inconsistency in the patternof conduction velocities across different heightgroups in these subjects.

Acknowledgements:

Research project was supported by IRPA shortresearch grant 304/PPSP/6131231

Correspondence :

Dr. Mohamed Saufi Awang MBBSDepartment of NeurosciencesSchool of Medical Sciences,Universiti Sains Malaysia, Health Campus,16150 Kubang Kerian, Kelantan, MalaysiaTel: + 609-766 4240Fax: +609-764 8613Email: deptneurosciencesppspusm@yahoo.com

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NERVE CONDUCTION STUDY AMONG HEALTHY MALAYS. THE INFLUENCE OF AGE, HEIGHT AND BODY MASS INDEX ON MEDIAN, ULNAR, COMMON PERONEAL AND SURALNERVES