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Dorsal ulnar cutaneous nerve conduction studies in an asymptomatic population
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Dorsal Ulnar Cutaneous Nerve Conduction Studies in an Asymptomatic Population Sherry H-Y Young, MD, Anathal Kalantri, MD ABSTRACT. Young SH-Y, Kalantri A. Dorsal ulnar cutaneous nerve conduction studies in an asymptomatic population. Arch Phys Med Rehabil 2000;81:1171-2. Objectives: To establish the average distal sensory latency and amplitude of the dorsal ulnar cutaneous nerve under controlled temperature and settings. Design: Dorsal ulnar cutaneous nerve conduction studies were performed with a bar electrode between the fourth and fifth metacarpals. The nerve was stimulated at 8 and 10cm from the active electrode. The temperature of the limbs under study was kept at 32°C to 35°C. Participants: Fifty-four arms of 27 subjects were studied. Results: Results showed that distal sensory latencies were normally distributed. The average distal sensory latencies at 8cm and 10cm were 1.84 ⫾ .20msec and 2.09 ⫾ .21msec, respectively, with average amplitudes of 26.5 ⫾ 9.7µV and 23.5 ⫾ 8.8µV. Comparison with a previously reported study in which the limb temperature was not controlled showed a statistically significant difference. Conclusion: It is important to use standardized technique and to measure and maintain optimal temperature of the arm under study to prevent erroneous results and misdiagnosis. Key Words: Ulnar nerve; Temperature; Nerve conduction; Rehabilitation. r 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
T
HE DORSAL ULNAR cutaneous sensory branch of the ulnar nerve is frequently used to localize ulnar nerve lesions to the distal forearm or wrist. This sensory branch leaves the main nerve trunk at an average of 6.4cm from the distal aspect of the head of the ulna and 8.3cm from the proximal border of the pisiform. It becomes subcutaneous on the medial aspect of the forearm at a mean distance of 5.0cm from the proximal edge of the pisiform.1 It most commonly supplies sensation to the dorsoulnar aspect of the wrist and the hand, as well as the dorsal surface of the fifth digit and ulnar half of the fourth digit. Two previous studies have documented the average distal sensory latency and amplitude of the dorsal ulnar cutaneous nerve.2,3 However, in the study by Kim et al,3 the distance from the active electrode to the site of stimulation was
From the Department of Rehabilitation Medicine, University of Texas Health Science Center, San Antonio, TX (Young, Kalantri). Dr. Young is currently affiliated with the Department of Rehabilitation Medicine, Changi General Hospital, Singapore. Accepted January 31, 2000. Presented as a poster presentation at the American Academy of Physical Medicine and Rehabilitation’s 60th Annual Assembly, November 1998, Seattle. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Sherry H-Y Young, MD, Department of Rehabilitation Medicine, Changi General Hospital, 2 Simei St 3, Singapore 529-889, Republic of Singapore. 0003-9993/00/8109-5736$3.00/0 doi:10.1053/apmr.2000.7163
not controlled. Because the distal sensory latency is the time required for the electric stimulus to travel a certain distance, the variable distance is expected to produce nonuniform results. In Jabre’s study,2 the surface temperature of the limb under investigation was not measured and maintained during the study. Temperature effects on nerve conduction velocity are well documented: nerve impulses are conducted faster at higher body temperatures. The conduction velocity increases almost linearly, by 1.6m/sec/°C for ulnar sensory nerves, as the surface temperature measured near the nerve increases from 26°C to 33°C.4 The goals of this study were to establish the average distal sensory latency and amplitude of the dorsal ulnar cutaneous nerve in an asymptomatic population under optimal conditions, that is, with a fixed stimulus/active electrode distance and a limb surface temperature of greater than 32°C. METHODS The study tested the 54 arms of 27 healthy adults who did not have signs or symptoms of ulnar neuropathy. Subjects were recruited from health care providers and from among our patients. There were 10 women and 17 men, ages from 22 to 71 years, with a mean age of 40.7 ⫾ 13 years. Temperature of the palm of the hand was measured by a surface thermistor before the study, and it ranged from 32°C to 34.5°C. Routine nerve conduction studies of one sural and one peroneal nerve were performed to rule out subclinical peripheral neuropathy. Subjects with abnormal sural and/or peroneal nerve conduction study results were excluded. An averager was used only if the amplitude was lower than 5µV. The primary investigator used a Cadwell 5200A electromyographic machinea and performed all the studies. With the subject in the supine position with arm alongside the body and forearm fully pronated, a bar-type bipolar electrode with a 3cm interelectrode distance was placed between the fourth and fifth metacarpals. A ground was placed between the stimulating and recording electrodes. The dorsal ulnar cutaneous nerve was then stimulated 8 and 10cm from the active electrode between the ulna and the flexor carpi ulnaris tendon.2 Responses were recorded at 20µV/division gain and with 10Hz to 2kHz bandwidths. The distal sensory latencies were measured to the peak of the responses, and the amplitudes were measured from baseline to negative peak. This study was approved by the institutional review board and all subjects gave written consent before participation. RESULTS Results showed the average distal sensory latency obtained at 8cm to be 1.84 ⫾ .20msec with an average amplitude of 26.5 ⫾ 9.7µV. Average distal sensory latency obtained at 10cm was 2.09 ⫾ .21msec with an average amplitude of 23.5 ⫾ 8.8µV (table 1). Only on one occasion was the distal sensory latency not obtained at both the 8cm and 10cm distances in the right arm in one subject. With the inching technique, distances of 4 to 12cm were tried without success in the same object. There was no Arch Phys Med Rehabil Vol 81, September 2000
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DORSAL ULNAR CUTANEOUS NERVE CONDUCTION STUDY, Young
Table 1: Dorsal Ulnar Cutaneous Nerve Conduction Study Results
8cm Mean ⫾ SD Range 10cm Mean ⫾ SD Range
Distal Sensory Latency*
Sensory Amplitude†
1.84 ⫾ .20 1.51-2.35
26.5 ⫾ 9.7 9.0-48.0
2.09 ⫾ .21 1.76-2.68
23.5 ⫾ 8.8 7.0-43.0
Abbreviation: SD, standard deviation. * Measured to negative peak, in milliseconds. † Measured from baseline to negative peak, in microvolts.
difficulty obtaining the contralateral responses. The lowest sensory amplitude obtained was 7µV. Comparison of our results obtained at 8cm with the results from Jabre’s study,2 which were also obtained at 8cm, showed that the average distal sensory latency with the arm temperature controlled is 1.84msec instead of 2.0msec. Application of the one-sample Kolmogorov-Smirnov test to our data confirmed that our sample had a normal distribution.5 Comparison of our results at 8cm with the results obtained from Jabre’s study, which used the chi-square test, showed the difference to be statistically significant with a p value of ⬍.001. DISCUSSION AND CONCLUSION Use of the bar electrode has a disadvantage because the interelectrode distance is less than the optimal 4cm. This has been shown to reduce the amplitudes of the sensory nerve action potentials.4 With the bar electrode, however, the technique can easily be standardized and reproduced. It may not be possible to maintain the 4cm distance in subjects with small hands. The one instance in which the sensory nerve action potential
Arch Phys Med Rehabil Vol 81, September 2000
was not obtained could have resulted from anomalous innervation of the area by the superficial radial nerve, as suggested by a previous study.6 Our results from the 8cm distance, when compared with the results obtained from Jabre’s study,2 showed our average distal sensory latencies to be shorter, which is statistically significant. This result is not unexpected because keeping the limb temperature closer to the core body temperature gives faster responses. This highlights the importance of keeping the limb under study at optimal temperatures. Our results showed that it is important to measure and maintain optimal temperature of the arm under study to prevent erroneous results and misdiagnosis. We also conclude that with our technique, it is easy to obtain the distal sensory responses of the dorsal ulnar cutaneous nerve. The average distal sensory latencies and amplitudes are as presented. References 1. Botte MJ, Cohen M, Lavernia CJ, von Schroeder HP, Gellman H, Zinberg EM. The dorsal branch of the ulnar nerve: an anatomic study. J Hand Surg [Am] 1990;15:603-7. 2. Jabre JF. Ulnar nerve lesions at the wrist: new technique for recording from the sensory dorsal branch of the ulnar nerve. Neurology 1980;30:873-6. 3. Kim DJ, Kalantri A, Guha S, Wainapel SF. Dorsal cutaneous ulnar nerve conduction. Diagnostic aid in ulnar neuropathy. Arch Neurol 1980;38:321-2. 4. Dumitru D. Electrodiagnostic medicine. Philadelphia: Hanley & Belfus; 1995. 5. Daniel WW. Biostatistics: a foundation for analysis in the health sciences. 5th ed. New York: John Wiley; 1991. 6. Peterson AR, Giuliani M, McHugh M, Shipe CC. Variations in dorsomedial hand innervation: electrodiagnostic implications. Arch Neurol 1992;49:870-3. Supplier a. Cadwell Laboratories, 909 N Kellogg St, Kennewick, WA 99336.
Dorsal Ulnar Cutaneous Nerve Conduction Studies in an Asymptomatic Population Sherry H-Y Young, MD, Anathal Kalantri, MD ABSTRACT. Young SH-Y, Kalantri A. Dorsal ulnar cutaneous nerve conduction studies in an asymptomatic population. Arch Phys Med Rehabil 2000;81:1171-2. Objectives: To establish the average distal sensory latency and amplitude of the dorsal ulnar cutaneous nerve under controlled temperature and settings. Design: Dorsal ulnar cutaneous nerve conduction studies were performed with a bar electrode between the fourth and fifth metacarpals. The nerve was stimulated at 8 and 10cm from the active electrode. The temperature of the limbs under study was kept at 32°C to 35°C. Participants: Fifty-four arms of 27 subjects were studied. Results: Results showed that distal sensory latencies were normally distributed. The average distal sensory latencies at 8cm and 10cm were 1.84 ⫾ .20msec and 2.09 ⫾ .21msec, respectively, with average amplitudes of 26.5 ⫾ 9.7µV and 23.5 ⫾ 8.8µV. Comparison with a previously reported study in which the limb temperature was not controlled showed a statistically significant difference. Conclusion: It is important to use standardized technique and to measure and maintain optimal temperature of the arm under study to prevent erroneous results and misdiagnosis. Key Words: Ulnar nerve; Temperature; Nerve conduction; Rehabilitation. r 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
T
HE DORSAL ULNAR cutaneous sensory branch of the ulnar nerve is frequently used to localize ulnar nerve lesions to the distal forearm or wrist. This sensory branch leaves the main nerve trunk at an average of 6.4cm from the distal aspect of the head of the ulna and 8.3cm from the proximal border of the pisiform. It becomes subcutaneous on the medial aspect of the forearm at a mean distance of 5.0cm from the proximal edge of the pisiform.1 It most commonly supplies sensation to the dorsoulnar aspect of the wrist and the hand, as well as the dorsal surface of the fifth digit and ulnar half of the fourth digit. Two previous studies have documented the average distal sensory latency and amplitude of the dorsal ulnar cutaneous nerve.2,3 However, in the study by Kim et al,3 the distance from the active electrode to the site of stimulation was
From the Department of Rehabilitation Medicine, University of Texas Health Science Center, San Antonio, TX (Young, Kalantri). Dr. Young is currently affiliated with the Department of Rehabilitation Medicine, Changi General Hospital, Singapore. Accepted January 31, 2000. Presented as a poster presentation at the American Academy of Physical Medicine and Rehabilitation’s 60th Annual Assembly, November 1998, Seattle. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Sherry H-Y Young, MD, Department of Rehabilitation Medicine, Changi General Hospital, 2 Simei St 3, Singapore 529-889, Republic of Singapore. 0003-9993/00/8109-5736$3.00/0 doi:10.1053/apmr.2000.7163
not controlled. Because the distal sensory latency is the time required for the electric stimulus to travel a certain distance, the variable distance is expected to produce nonuniform results. In Jabre’s study,2 the surface temperature of the limb under investigation was not measured and maintained during the study. Temperature effects on nerve conduction velocity are well documented: nerve impulses are conducted faster at higher body temperatures. The conduction velocity increases almost linearly, by 1.6m/sec/°C for ulnar sensory nerves, as the surface temperature measured near the nerve increases from 26°C to 33°C.4 The goals of this study were to establish the average distal sensory latency and amplitude of the dorsal ulnar cutaneous nerve in an asymptomatic population under optimal conditions, that is, with a fixed stimulus/active electrode distance and a limb surface temperature of greater than 32°C. METHODS The study tested the 54 arms of 27 healthy adults who did not have signs or symptoms of ulnar neuropathy. Subjects were recruited from health care providers and from among our patients. There were 10 women and 17 men, ages from 22 to 71 years, with a mean age of 40.7 ⫾ 13 years. Temperature of the palm of the hand was measured by a surface thermistor before the study, and it ranged from 32°C to 34.5°C. Routine nerve conduction studies of one sural and one peroneal nerve were performed to rule out subclinical peripheral neuropathy. Subjects with abnormal sural and/or peroneal nerve conduction study results were excluded. An averager was used only if the amplitude was lower than 5µV. The primary investigator used a Cadwell 5200A electromyographic machinea and performed all the studies. With the subject in the supine position with arm alongside the body and forearm fully pronated, a bar-type bipolar electrode with a 3cm interelectrode distance was placed between the fourth and fifth metacarpals. A ground was placed between the stimulating and recording electrodes. The dorsal ulnar cutaneous nerve was then stimulated 8 and 10cm from the active electrode between the ulna and the flexor carpi ulnaris tendon.2 Responses were recorded at 20µV/division gain and with 10Hz to 2kHz bandwidths. The distal sensory latencies were measured to the peak of the responses, and the amplitudes were measured from baseline to negative peak. This study was approved by the institutional review board and all subjects gave written consent before participation. RESULTS Results showed the average distal sensory latency obtained at 8cm to be 1.84 ⫾ .20msec with an average amplitude of 26.5 ⫾ 9.7µV. Average distal sensory latency obtained at 10cm was 2.09 ⫾ .21msec with an average amplitude of 23.5 ⫾ 8.8µV (table 1). Only on one occasion was the distal sensory latency not obtained at both the 8cm and 10cm distances in the right arm in one subject. With the inching technique, distances of 4 to 12cm were tried without success in the same object. There was no Arch Phys Med Rehabil Vol 81, September 2000
1172
DORSAL ULNAR CUTANEOUS NERVE CONDUCTION STUDY, Young
Table 1: Dorsal Ulnar Cutaneous Nerve Conduction Study Results
8cm Mean ⫾ SD Range 10cm Mean ⫾ SD Range
Distal Sensory Latency*
Sensory Amplitude†
1.84 ⫾ .20 1.51-2.35
26.5 ⫾ 9.7 9.0-48.0
2.09 ⫾ .21 1.76-2.68
23.5 ⫾ 8.8 7.0-43.0
Abbreviation: SD, standard deviation. * Measured to negative peak, in milliseconds. † Measured from baseline to negative peak, in microvolts.
difficulty obtaining the contralateral responses. The lowest sensory amplitude obtained was 7µV. Comparison of our results obtained at 8cm with the results from Jabre’s study,2 which were also obtained at 8cm, showed that the average distal sensory latency with the arm temperature controlled is 1.84msec instead of 2.0msec. Application of the one-sample Kolmogorov-Smirnov test to our data confirmed that our sample had a normal distribution.5 Comparison of our results at 8cm with the results obtained from Jabre’s study, which used the chi-square test, showed the difference to be statistically significant with a p value of ⬍.001. DISCUSSION AND CONCLUSION Use of the bar electrode has a disadvantage because the interelectrode distance is less than the optimal 4cm. This has been shown to reduce the amplitudes of the sensory nerve action potentials.4 With the bar electrode, however, the technique can easily be standardized and reproduced. It may not be possible to maintain the 4cm distance in subjects with small hands. The one instance in which the sensory nerve action potential
Arch Phys Med Rehabil Vol 81, September 2000
was not obtained could have resulted from anomalous innervation of the area by the superficial radial nerve, as suggested by a previous study.6 Our results from the 8cm distance, when compared with the results obtained from Jabre’s study,2 showed our average distal sensory latencies to be shorter, which is statistically significant. This result is not unexpected because keeping the limb temperature closer to the core body temperature gives faster responses. This highlights the importance of keeping the limb under study at optimal temperatures. Our results showed that it is important to measure and maintain optimal temperature of the arm under study to prevent erroneous results and misdiagnosis. We also conclude that with our technique, it is easy to obtain the distal sensory responses of the dorsal ulnar cutaneous nerve. The average distal sensory latencies and amplitudes are as presented. References 1. Botte MJ, Cohen M, Lavernia CJ, von Schroeder HP, Gellman H, Zinberg EM. The dorsal branch of the ulnar nerve: an anatomic study. J Hand Surg [Am] 1990;15:603-7. 2. Jabre JF. Ulnar nerve lesions at the wrist: new technique for recording from the sensory dorsal branch of the ulnar nerve. Neurology 1980;30:873-6. 3. Kim DJ, Kalantri A, Guha S, Wainapel SF. Dorsal cutaneous ulnar nerve conduction. Diagnostic aid in ulnar neuropathy. Arch Neurol 1980;38:321-2. 4. Dumitru D. Electrodiagnostic medicine. Philadelphia: Hanley & Belfus; 1995. 5. Daniel WW. Biostatistics: a foundation for analysis in the health sciences. 5th ed. New York: John Wiley; 1991. 6. Peterson AR, Giuliani M, McHugh M, Shipe CC. Variations in dorsomedial hand innervation: electrodiagnostic implications. Arch Neurol 1992;49:870-3. Supplier a. Cadwell Laboratories, 909 N Kellogg St, Kennewick, WA 99336.