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Poster 13 A volume conducted response resembling anomalous innervation
ACADEMY ANNUAL ASSEMBLY ABSTRACTS
amplitudes and peak latencies were recorded, as well as visual analogue pain scale (VAS) scores. The results showed no significant differences in median and ulnar mean amplitudes or peak latencies for EMLA compared to placebo. There were no significant differences in mean VAS scores between the studies. We conclude that there is no effect by EMLA on SNCS amplitudes or peak latencies in the upper extremities. Although there were no significant differences in VAS scores in normal adults using EMLA verses placebo, this many not be true in patients with hyperpathic syndromes. Further studies on the use of EMLA cream for electrodiagnostic evaluations in these patients may benefit this population.
Poster 11 "Spastic Paresis Score: Quantifying the Upper Motor Neuron Syndrome." Pamela O. Black, MD (University of Wisconsin, Madison, WI); Arthur Alfred Rodriquez, MD. The upper motor neuron syndrome (UMNS) is easy to recognize clinically but is difficult to quantify. We have shown previously that a ratio (CR) of antagonist to agonist surface EMG activity is a reliable and valid measure of UMNS. The purpose of this study was to use CR to validate a new clinical scale, the Spasti c Paresis Score (SPS), which assesses motor tone, deep tendon reflexes, and muscle strength. Eight UMNS subjects performed maximum isometric voluntary knee extension. Peak torque (MVC) and surface EMG of quadriceps and hamstrings were simultaneously measured. Before testing, the affected limb was examined for motor tone, using the Ashworth scale, for muscle strength using the Medical Research Council (MRC) scale, and for knee and ankle reflexes using a 0-4 scale. The MRC scale was then inverted so that scores increased with increasing weakness. A composite score (SPS) was compiled by summing the Ashworth scale, the inverted MRC score, and knee and ankle reflex scores. CR was determined as the ratio of hamstring to quadriceps root mean squared EMG. Analysis was by Pearson Product correlation. There was a significant (p < .05) positive correlation between CR and SPS (R = .83) and a significant (p < .05) negative correlation between SPS and MVC (R = -.85). These findings support validity of SPS in quantifying UMNS.
Poster 12 "Screening for Cervical Radiculopathy in Patients Referred for Electrodiagnostic Evaluation of Carpal Tunnel Syndrome." Margaret M. Snow, MD (Medical College of Wisconsin, Milwaukee, WI); Tracy A. Park, MD. The purpose of this study was to investigate whether it is useful to perform needle electromyographic (EMG) screens for cervical radiculopathy on patients referred for electrodiagnostic evaluation of carpal tunnel syndrome (CTS). We reviewed all 242 upper extremity studies performed at our EMG lab over a 14-month period. Of 181 patients who received radiculopathy screens, 13% (24/181) were positive. Referral for radiculopathy or for neck pain had the highest incidence of positive screens, with 21% (9/43) and 27% (3/11) respectively. Of patients referred for CTS, only 4% (1/24) had a positive radiculopathy screen. The coexistence of CTS and cervical radiculopathies was noted in 29% of radiculopathies and 10% of those with median neuropathy. Our results suggest that screening for cervical radiculopathy is of limited value in patients referred for CTS unless they have additional symptoms suggestive of cervical radiculopathy.
Poster 13 "A Volume Conducted Response Resembling Anomalous Innervation." Stanley R. Jacobs, MD (Thomas Jefferson University Hospital, Philadelphia, PA); Jeffrey M. Friedman, MD. The purpose of this study was to describe the unrecognized electrophysiological findings of an initial deflection negative volume conducted compound muscle action potential (CMAP). If a volume conducted response has an initial negative deflection, it can be mistaken for anomalous innervation. Twenty healthy men and women were studied using the Nicolet Viking. The deep peroneal and tibial nerves were stimulated. Recording electrodes were placed on the motor points of the extensor digitorum brevis (EDB) and abductor hallucis (AH), as well as off the motor points of the AH. In all subjects, stimulating the deep peroneal nerve (DPN) and recording over the AH and EDB produced an initial deflection negative CMAP. Stimulating the DPN and recording anterior
1045
and posterior to the AH motor point also resulted in an initial deflection negative CMAP. Needle recording in the AH was confirmed as volume conduction in the three subjects studied in this manner. All standard peroneal and tibial nerve conductions were normal. An anomalous innervation should have produced an initial deflection positive CMAP when recording off the motor point. In our subjects, when recording off the motor point, the CMAP remained initial deflection negative. This proves that this is a volume conducted phenomenon, and this is further supported by the results of needle recording in the AH. In conclusion, our study illustrates that in healthy subjects, this initial deflection negative CMAP is volume conducted and is a normal electrophysiological finding. In addition, this response can be misinterpreted as a distal anomalous innervation with adverse clinical consequences.
Poster 14 "Neck Flexion Effect on F-Wave and H-Reflex." Jenny M. Lai, MD (Baylor College of Medicine, Houston, TX); Faye Chiou-Tan, MD; Stephen M. Tuel, MD. H-reflex and F-wave are known to be affected by spinal cord excitability. Facilitative maneuvers such as the Jendrassik maneuver, clenching teeth, and neck flexion can affect the magnitude of the stretch reflex. Our hypothesis was that these maneuvers would have an effect on the latency or the amplitude of H-reflexes or F-waves. Ten neurologically normal subjects (5 men and 5 women) were recruited. H-reflexes and F-waves were measured in the nondominant tibial nerve. Each trial consisted of three H-reflexes 30 seconds apart and 10 F-waves five seconds apart. Five trials were performed: baseline control, Jendrassik, clenched teeth, neck flexion, and postmaneuver control. Anthropomorphic measurements were obtained and temperature controlled. Statistical analysis was performed with a two-tailed, paired t test and ANOVA. A 1.5ms increase in the latency of the H-reflex in neck flexion (p < .005), and a 18% and 11% increase in the amplitude of the H-reflex and the F-wave, respectively, were found for the neck flexion trial (p < .05). There were no significant changes in the Jendrassik or jaw clench trials (p > 0.1). The neurophysiology and possible etiology of the results are discussed.
Poster 15 "Generators of Early and Late Hypothenar Premotor Potentials: Eiectrophysiology Inching and Cadaveric Dissection." Kathleen C. Jurell, M D (The Medical College of Wisconsin, Milwaukee, WI); Tracy A. Park, MD; William Dzwierzynski, MD; David R. Del Toro, MD. The generator sources of ulnar hypothenar premotor potentials (PMPs) have been explored with previous studies but have not been clearly identified. Using a variety of bipolar and referential recording montages to study the ulnar nerve in 10 hands, we examined the possible nearfield and far-field sources of these potentials. The results of this study suggest that the early ulnar PMP is a near-field potential recorded by G~ and generated by the ulnar nerve as it passes near the Gt electrode. The late ulnar PMP represents a far-field potential generated by the ulnar digital nerves as they pass from the hand volume to the finger volume containing G2. These generator sources of the ulnar PMPs parallel those of the early and late median PMPs, which are more easily discerned because of the greater separation between the late median PMP and the trailing tbenar compound muscle action potential (CMAP). This greater separation was explained by cadaveric dissection of 3 hands, which showed that the motor branch (responsible for the trailing CMAP) is longer in the median nerve than in the ulnar nerve relative to each nerve's corresponding digital sensory branch (responsible for the preceding late PMP).
Poster 16 "Locafization of the Neuromuscular Junction through Needle Electromyography." Laura Beth Ottaviani, DO (University of Missouri Hospital and Clinics, Columbia, MO); Martin K. Childers, DO. The purpose of this study was to determine if needle electromyugraphy can accurately localize the neuromuscular junction in skeletal muscle. The right rear gastrocnemius muscle was studied in five anesthetized dogs using needle EMG. The neuromuscular junction was identified by systematically searching for endplate potential and then mapping the positive findings onto a three-dimensional grid. Previous histological studies localized the neuromuscular junction in the middle of the muscle
Arch Phys Med Rehabil Vol 75, November 1995
amplitudes and peak latencies were recorded, as well as visual analogue pain scale (VAS) scores. The results showed no significant differences in median and ulnar mean amplitudes or peak latencies for EMLA compared to placebo. There were no significant differences in mean VAS scores between the studies. We conclude that there is no effect by EMLA on SNCS amplitudes or peak latencies in the upper extremities. Although there were no significant differences in VAS scores in normal adults using EMLA verses placebo, this many not be true in patients with hyperpathic syndromes. Further studies on the use of EMLA cream for electrodiagnostic evaluations in these patients may benefit this population.
Poster 11 "Spastic Paresis Score: Quantifying the Upper Motor Neuron Syndrome." Pamela O. Black, MD (University of Wisconsin, Madison, WI); Arthur Alfred Rodriquez, MD. The upper motor neuron syndrome (UMNS) is easy to recognize clinically but is difficult to quantify. We have shown previously that a ratio (CR) of antagonist to agonist surface EMG activity is a reliable and valid measure of UMNS. The purpose of this study was to use CR to validate a new clinical scale, the Spasti c Paresis Score (SPS), which assesses motor tone, deep tendon reflexes, and muscle strength. Eight UMNS subjects performed maximum isometric voluntary knee extension. Peak torque (MVC) and surface EMG of quadriceps and hamstrings were simultaneously measured. Before testing, the affected limb was examined for motor tone, using the Ashworth scale, for muscle strength using the Medical Research Council (MRC) scale, and for knee and ankle reflexes using a 0-4 scale. The MRC scale was then inverted so that scores increased with increasing weakness. A composite score (SPS) was compiled by summing the Ashworth scale, the inverted MRC score, and knee and ankle reflex scores. CR was determined as the ratio of hamstring to quadriceps root mean squared EMG. Analysis was by Pearson Product correlation. There was a significant (p < .05) positive correlation between CR and SPS (R = .83) and a significant (p < .05) negative correlation between SPS and MVC (R = -.85). These findings support validity of SPS in quantifying UMNS.
Poster 12 "Screening for Cervical Radiculopathy in Patients Referred for Electrodiagnostic Evaluation of Carpal Tunnel Syndrome." Margaret M. Snow, MD (Medical College of Wisconsin, Milwaukee, WI); Tracy A. Park, MD. The purpose of this study was to investigate whether it is useful to perform needle electromyographic (EMG) screens for cervical radiculopathy on patients referred for electrodiagnostic evaluation of carpal tunnel syndrome (CTS). We reviewed all 242 upper extremity studies performed at our EMG lab over a 14-month period. Of 181 patients who received radiculopathy screens, 13% (24/181) were positive. Referral for radiculopathy or for neck pain had the highest incidence of positive screens, with 21% (9/43) and 27% (3/11) respectively. Of patients referred for CTS, only 4% (1/24) had a positive radiculopathy screen. The coexistence of CTS and cervical radiculopathies was noted in 29% of radiculopathies and 10% of those with median neuropathy. Our results suggest that screening for cervical radiculopathy is of limited value in patients referred for CTS unless they have additional symptoms suggestive of cervical radiculopathy.
Poster 13 "A Volume Conducted Response Resembling Anomalous Innervation." Stanley R. Jacobs, MD (Thomas Jefferson University Hospital, Philadelphia, PA); Jeffrey M. Friedman, MD. The purpose of this study was to describe the unrecognized electrophysiological findings of an initial deflection negative volume conducted compound muscle action potential (CMAP). If a volume conducted response has an initial negative deflection, it can be mistaken for anomalous innervation. Twenty healthy men and women were studied using the Nicolet Viking. The deep peroneal and tibial nerves were stimulated. Recording electrodes were placed on the motor points of the extensor digitorum brevis (EDB) and abductor hallucis (AH), as well as off the motor points of the AH. In all subjects, stimulating the deep peroneal nerve (DPN) and recording over the AH and EDB produced an initial deflection negative CMAP. Stimulating the DPN and recording anterior
1045
and posterior to the AH motor point also resulted in an initial deflection negative CMAP. Needle recording in the AH was confirmed as volume conduction in the three subjects studied in this manner. All standard peroneal and tibial nerve conductions were normal. An anomalous innervation should have produced an initial deflection positive CMAP when recording off the motor point. In our subjects, when recording off the motor point, the CMAP remained initial deflection negative. This proves that this is a volume conducted phenomenon, and this is further supported by the results of needle recording in the AH. In conclusion, our study illustrates that in healthy subjects, this initial deflection negative CMAP is volume conducted and is a normal electrophysiological finding. In addition, this response can be misinterpreted as a distal anomalous innervation with adverse clinical consequences.
Poster 14 "Neck Flexion Effect on F-Wave and H-Reflex." Jenny M. Lai, MD (Baylor College of Medicine, Houston, TX); Faye Chiou-Tan, MD; Stephen M. Tuel, MD. H-reflex and F-wave are known to be affected by spinal cord excitability. Facilitative maneuvers such as the Jendrassik maneuver, clenching teeth, and neck flexion can affect the magnitude of the stretch reflex. Our hypothesis was that these maneuvers would have an effect on the latency or the amplitude of H-reflexes or F-waves. Ten neurologically normal subjects (5 men and 5 women) were recruited. H-reflexes and F-waves were measured in the nondominant tibial nerve. Each trial consisted of three H-reflexes 30 seconds apart and 10 F-waves five seconds apart. Five trials were performed: baseline control, Jendrassik, clenched teeth, neck flexion, and postmaneuver control. Anthropomorphic measurements were obtained and temperature controlled. Statistical analysis was performed with a two-tailed, paired t test and ANOVA. A 1.5ms increase in the latency of the H-reflex in neck flexion (p < .005), and a 18% and 11% increase in the amplitude of the H-reflex and the F-wave, respectively, were found for the neck flexion trial (p < .05). There were no significant changes in the Jendrassik or jaw clench trials (p > 0.1). The neurophysiology and possible etiology of the results are discussed.
Poster 15 "Generators of Early and Late Hypothenar Premotor Potentials: Eiectrophysiology Inching and Cadaveric Dissection." Kathleen C. Jurell, M D (The Medical College of Wisconsin, Milwaukee, WI); Tracy A. Park, MD; William Dzwierzynski, MD; David R. Del Toro, MD. The generator sources of ulnar hypothenar premotor potentials (PMPs) have been explored with previous studies but have not been clearly identified. Using a variety of bipolar and referential recording montages to study the ulnar nerve in 10 hands, we examined the possible nearfield and far-field sources of these potentials. The results of this study suggest that the early ulnar PMP is a near-field potential recorded by G~ and generated by the ulnar nerve as it passes near the Gt electrode. The late ulnar PMP represents a far-field potential generated by the ulnar digital nerves as they pass from the hand volume to the finger volume containing G2. These generator sources of the ulnar PMPs parallel those of the early and late median PMPs, which are more easily discerned because of the greater separation between the late median PMP and the trailing tbenar compound muscle action potential (CMAP). This greater separation was explained by cadaveric dissection of 3 hands, which showed that the motor branch (responsible for the trailing CMAP) is longer in the median nerve than in the ulnar nerve relative to each nerve's corresponding digital sensory branch (responsible for the preceding late PMP).
Poster 16 "Locafization of the Neuromuscular Junction through Needle Electromyography." Laura Beth Ottaviani, DO (University of Missouri Hospital and Clinics, Columbia, MO); Martin K. Childers, DO. The purpose of this study was to determine if needle electromyugraphy can accurately localize the neuromuscular junction in skeletal muscle. The right rear gastrocnemius muscle was studied in five anesthetized dogs using needle EMG. The neuromuscular junction was identified by systematically searching for endplate potential and then mapping the positive findings onto a three-dimensional grid. Previous histological studies localized the neuromuscular junction in the middle of the muscle
Arch Phys Med Rehabil Vol 75, November 1995