|Year : 2014 | Volume
| Issue : 1 | Page : 7-9
Medial and lateral antebrachial nerve conductions: Orthodromic or antidromic?
Kunam Sanjeeva Reddy1, Karkal Ravishankar Naik2, Aralikatte Onkarappa Saroja2
1 Department of Neurology, KLE University's Jawaharlal Nehru Medical College, Belgaum, Karnataka, India
2 KLE University's Jawaharlal Nehru Medical College and KLES Dr. Prabhakar Kore Hospital, Belgaum, Karnataka, India
|Date of Web Publication||7-Feb-2014|
Kunam Sanjeeva Reddy
Department of Neurology, KLE University's Jawaharlal Nehru Medical College, Nehru Nagar, Belgaum 590 010. Karnataka
Source of Support: None, Conflict of Interest: None
Introduction: Antidromic stimulation is usually used in the evaluation of lateral antebrachial cutaneous nerve (LABCN) and medial antebrachial cutaneous nerve (MABCN). This study was conducted to evaluate the relationship between orthodromic and antidromic stimulations of these nerves. Materials and Methods: Medial and lateral antebrachial conduction studies by antidromic and orthodromic stimulation. Results: Sensory nerve action potential (SNAP) amplitudes were larger with antidromic stimulation in the majority of subjects. The lateral antebrachial SNAP amplitude was 20.5 ± 9.29 μV with antidromic stimulation and 14.6 ± 6.13 μV with orthodromic stimulation (P < 0.001). Medial antebrachial SNAP amplitudes were 12.8 ± 4.93 μV using antidromic stimulation and 6.5 ± 3.84 μV with orthodromic stimulation (P < 0.001). Sensory conduction velocities were faster with orthodromic lateral antebrachial stimulation (P = 0.002) whereas velocities were similar in medial antebrachial nerve. Supramaximal stimulation of MABCN was not possible in half of the nerves sampled to avoid the muscle artifact. Conclusion: Orthodromic stimulation of LABCN and MABCN are easy to perform and can be supplanted for antidromic stimulation in which Supramaximal stimulation may not be possible in some individuals.
Keywords: Antidromic stimulation, lateral antebrachial cutaneous nerve, medial antebrachial cutaneous nerve, orthodromic stimulation, sensory nerve conductions
|How to cite this article:|
Reddy KS, Naik KR, Saroja AO. Medial and lateral antebrachial nerve conductions: Orthodromic or antidromic?. J Sci Soc 2014;41:7-9
| Introduction|| |
Sensory nerve conduction studies of lateral antebrachial cutaneous nerve (LABCN) and medial antebrachial cutaneous nerve (MABCN) supplement the clinical assessment and provide the key information in the evaluation of disorders of brachial plexus, cervical roots, and neurogenic thoracic outlet syndrome.  Published literature of normative data in LABCN and MABCN are relatively sparse. Antidromic stimulation has been utilized in most of the studies on LABCN ,,, and MABC; ,,, orthodromic stimulation has been used in some studies. ,, Antidromic and orthodromic stimulations have been evaluated in few studies. ,
We undertook this study to compare the orthodromic and antidromic stimulations for conductions of the LABCN and MABCN in healthy subjects.
| Materials and Methods|| |
Healthy volunteers consenting for the study were included. Subjects were included if they did not have any symptoms of neurological diseases or systemic disorders that could cause neuropathy. The study was approved by the institutional review board.
Sensory nerve conductions were performed in Nihon Kohden Neuropack MEB 9208 system. Signals were recorded with disc electrodes of 10 mm diameter and band-passed at 20 Hz to 2 KHz with a sampling interval of 50 μs. Antidromic stimulation of LABCN was performed at cubital fossa just lateral to the biceps tendon and the active recording electrode was placed 12 cm distally. Antidromic stimulation of MABCN was performed at mid arm and the recording electrode place 14 cm distally in the forearm with the active electrode placed 4 cm distal to the elbow crease in the line joining pisiform bone to the midpoint between biceps tendon and medial epicondyle. Recording electrode position was moved horizontally to obtain the maximum amplitude of sensory nerve action potential (SNAP). The positions of stimulating and recording electrodes were interchanged for the orthodromic stimulation. Inter-electrode distance of 4 cm was used between the active and reference recording electrodes. Bipolar stimulator with fixed inter-electrode distance of 23 mm was used and the stimulus duration was 0.2 ms, Stimulus intensity of 4 times the threshold was used. Lower stimulus intensity was used if there was large myogenic artifact arising from stimulus spread. Latency was measured from stimulus to the first positive peak. The data were analyzed using the SPSS software (version 10). Student's t-test, Pearson's correlation coefficient were used for analysis.
| Results|| |
Forty subjects were included in the study among whom there were 24 males and 16 females with age ranging from 10 to 60 (35.13 ± 9.94) years. Their height ranged from 148 to 180 cm (162.35 ± 9.07). Orthodromic and antidromic conductions were performed on 80 lateral and medial cutaneous nerves in these 40 subjects. SNAP could be recorded in all individuals. Findings of the nerve conductions are given in the [Table 1].
Stimulus intensity of 4 times the threshold for MABCN could be achieved in 50% of the nerves with antidromic stimulation. Stimulus intensity of 4 times the threshold was possible in all the MABCN orthodromic stimulations and both stimulations in LABCN. The SNAP amplitudes and velocities were not significantly related to the age, gender and height. The mean amplitudes of LABCN and MABCN were significantly larger with antidromic stimulation [Table 1]. In the majority of the subjects, the antidromic stimulation produced larger SNAP amplitudes. However, the orthodromic SNAP amplitude was larger in eight limbs for LABCN and two limbs in MABCN. There was no significant side-to-side difference in the mean amplitude and velocity for both orthodromic and antidromic stimulation. Conduction velocities were significantly higher with orthodromic than antidromic stimulation in the LABCN. No significant difference was observed between the orthodromic and antidromic velocities of MABCN. The negative peak duration did not significantly differ between two stimulations for both nerves [Table 1].
|Table 1: Antidromic and orthodromic conduction parameters of lateral and medial antebrachial nerves. Amplitudes are in microvolts, duration in milliseconds, velocity as m/s. Values in parenthesis depict the normal limits |
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| Discussion|| |
Nerve conduction studies of LABCN and MABCN are commonly performed in the routine electrodiagnostic evaluation of the peripheral nervous system. These nerves are usually tested in the disorders of brachial plexus, spinal roots and when the distal upper limb nerves are not excitable or not available for testing. Nerve conduction studies of the LABCN and MABCN are relatively sparse and have preferentially used antidromic stimulation, ,,,, whereas few had used orthodromic stimulation ,, [Table 2].
|Table 2: Summary amplitude data in the earlier publications on LABCN and MABCN sensory nerve |
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Kimura and Ayyar used antidromic stimulation of the LABCN by stimulating at elbow crease lateral to the biceps tendon for antidromic stimulation and recording 10 cm distally.  MABCN was stimulated at medial forearm and SNAP recorded at the elbow crease.  Seror reported the findings of orthodromic and antidromic stimulation of the forearm segment of MABCN with recording electrode placed 8-12 cm away.  Fixed length of forearm segment of MABCN and LABCN was evaluated by antidromic stimulation by Benatar et al. 
As the course of the cutaneous nerves can be variable, the stimulating and recording electrode placements need to be modified to obtain maximal response. , Recently a two-step technique to optimize the recording of SNAP of MABCN to reduced effects of anatomical variation in the nerve course. 
The surface recorded SNAP amplitudes with antidromic stimulation are usually larger than with orthodromic stimulation.  However, in median and ulnar digital nerves conduction, no differences were found between antidromic and orthodromic studies when the interelectrode distance was the same.  Antidromic and orthodromic SNAP amplitudes were similar in a recent study.  In the present study, amplitudes of the antidromic stimulation were larger with orthodromic stimulation in most of the individuals. However, in few subjects orthodromic amplitudes were more than antidromic stimulation. Myogenic artifacts from the spread of stimulus precluded adequate antidromic stimulation for MABCN in half of the nerves stimulated [Figure 1].
|Figure 1: Lateral (A = antidromic, B = orthodromic) and medial (C = antidromic, D = orthodromic) antebrachial cutaneous nerve conductions. Sensory nerve action potential amplitudes are 17.60 uV (antidromic) and 9.30 uV (orthodromic) in lateral antebrachial cutaneous nerve; 17.30 (antidromic) and 3.8 uV (orthodromic) in medial antebrachial nerve|
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Reduction in the amplitude with increasing age and body mass index was found in some studies. , However, such variation was not seen in an earlier study.  In the present study, there was no difference of amplitudes of the nerves with age, sex and height for both nerves. Correlation with body mass index, arm circumference, and skin fold thickness could have provided clues to marked reduction orthodromic SNAP amplitudes' in MABCN.
The velocities of the MABCN and LABCN are comparable to earlier publications. , Mild increase in orthodromic conduction velocity was noted in MABCN by Seror similar to our findings.  In the LABCN, we found a significant increase in orthodromic velocity could be due to volume conduction. Literature survey did not reveal comparison of orthodromic and antidromic stimulation of LABCN in the same cohort of subjects.
| Conclusion|| |
Our study confirms the earlier reported differences in the SNAP amplitudes with antidromic and orthodromic stimulations of LABCN and MABCN. To the best of our knowledge, we report for the first time the findings of orthodromic and antidromic stimulations of lateral antebrachial nerve. Antidromic MABCN stimulation was suboptimal in half the nerves sampled due to myogenic artifacts.
| References|| |
|1.||Le Forestier N, Maisonobe T, Moulonguet A, Leger JM, Bouche P. True neurogenic thoracic outlet syndrome: Electrophysiological diagnosis in six cases .Muscle Nerve 1998;21:1129-34. |
|2.||Benatar M, Wuu J, Peng L. Reference data for commonly used sensory and motor nerve conduction studies. Muscle Nerve 2009;40:772-94. |
|3.||Izzo KI, Aravabhumi S, Jafri A, Sobel E, Demopoulos JT. Medial and lateral antebrachial cutaneous nerves: Standardization of technique, reliability and age effect on healthy subjects. Arch Phys Med Rehabil 1985;66:592-7. |
|4.||Kimura I, Ayyar DR. Sensory nerve conduction study in the medial antebrachial cutaneous nerve. Tohoku J Exp Med 1984;142:461-6. |
|5.||Ralph B, Koch J, Emsley C, Katz B. Electrodiagnostic reference values for the lateral antebrachial cutaneous nerve: Standardization of a 10cm distance. Arch Phys Med Rehabil 2000;81:1563-6. |
|6.||Seror P. The Medial antebrachial cutaneous nerve: Antidromic and Orthodromic conduction studies. Muscle Nerve 2002;26:421-3. |
|7.||Buchthal F, Rosenfalck A. Evoked action potentials and conduction velocity in human sensory nerves. Brain Res 1966;3:1-122. |
|8.||Higashihara M, Sonoo M, Tsuji S. Two-step technique to optimize the medial antebrachial cutaneous nerve response. Clin Neurophysiol 2010;121:712-3. |
|9.||Cohn TG, Wertsch JJ, Pasupuleti DV. Nerve conduction studies: Orthodromic vs Antidromic latencies. Arch Phys Med Rehabil 1990;71:579-82. |
|10.||Reddy MP. Conduction studies of the medial cutaneous nerve of the forearm. Arch Phys Med Rehabil 1983;64:209-11. |
[Table 1], [Table 2]