Electrodiagnostic reference values for upper and lower limb nerve conduction studies in adult populations.

INTRODUCTION: To address the need for greater standardization within the field of electrodiagnostic medicine, the Normative Data Task Force (NDTF) was formed to identify nerve conduction studies (NCS) in the literature, evaluate them using consensus-based methodological criteria derived by the NDTF, and identify those suitable as a resource for NCS metrics. METHODS: A comprehensive literature search was conducted of published peer-reviewed scientific articles for 11 routinely performed sensory and motor NCS from 1990 to 2012. RESULTS: Over 7,500 articles were found. After review using consensus-based methodological criteria, only 1 study each met all quality criteria for 10 nerves. CONCLUSION: The NDTF selected only those studies that met all quality criteria and were considered suitable as a clinical resource for NCS metrics. The literature is, however, limited and these findings should be confirmed by larger, multicenter collaborative efforts. Muscle Nerve 54: 371-377, 2016.

Establishing high-quality reference values for nerve conduction studies: A report from the normative data task force of the American Association Of Neuromuscular & Electrodiagnostic Medicine.

INTRODUCTION: There are not uniform standards for nerve conduction testing across the United States. The objective of this study is to present a set of methodologically sound criteria to evaluate the literature for the purpose of identifying high-quality normative nerve conduction studies (NCS) suitable for widespread use. METHODS: The Normative Data Task Force (NDTF) was formed to review published studies on methodological issues related to NCS. A set of criteria was then developed to evaluate the literature. These criteria and their rationale are described. RESULTS: We identified 7 key issues that reflect high quality in NCS. For each issue, specific review criteria were developed. CONCLUSION: Rigorous criteria enable identification of high-quality studies dealing with nerve conduction reference values. This represents the first step toward the overarching goal of recommending NCS techniques and reference values for electrodiagnostic medicine. Muscle Nerve 54: 366-370, 2016.

Ulnar motor study to first dorsal interosseous: Best reference electrode position and normative data.

INTRODUCTION: Reference electrode position affects nerve conduction study results. This study was undertaken to determine the optimal reference electrode position for ulnar motor recording from the first dorsal interosseous (FDI) muscle and to develop normative data. METHODS: Fifty-one subjects were tested using reference electrode positions on the thumb, index, and little fingers. Latencies were compared with a needle recording from the FDI. Analysis was performed to determine the surface placement that most closely matched the needle recording latency. A normative database was then derived on 100 healthy subjects. RESULTS: Placing the reference electrode on the thumb yielded results closest to the "gold standard" needle recording latency. The 97th percentile (upper limit of normal) for latency was 4.0 ms. The 3rd percentile values (lower limit of normal) for amplitude were 9.0 mV for men and 9.3 mV for women. CONCLUSIONS: The reference position on the thumb yields latencies that most closely approximate needle recording. Normative data are presented.

Prevalence and risk factors for musculoskeletal injuries related to endoscopy.

BACKGROUND: There are limited data regarding work-related injury among endoscopists. OBJECTIVE: To define the prevalence of endoscopy-related musculoskeletal injuries and their impact on clinical practice and to identify physician and practice characteristics associated with their development. DESIGN: Survey. SETTING: Electronic survey of active members of the American Society for Gastrointestinal Endoscopy with registered e-mail addresses. PARTICIPANTS: Physicians who currently or ever performed endoscopy and responded to the survey between February 2013 and November 2013. INTERVENTION: A 25-question, self-administered, electronic survey. MAIN OUTCOME MEASUREMENTS: Prevalence, location, and ramifications of work-related injuries and endoscopist characteristics and workload parameters associated with endoscopy-related injury. RESULTS: The survey was completed by 684 endoscopists. Of those, 362 (53%) experienced a musculoskeletal injury perceived definitely (n = 204) or possibly (n = 158) related to endoscopy. Factors associated with a higher rate of endoscopy-related injury included higher procedure volume (>20 cases/week; P < .001), greater number of hours per week spent performing endoscopy (>16 hours/week; P < .001), and total number of years performing endoscopy (P = .004). The most common sites of injury were neck and/or upper back (29%) and thumb (28%). Only 55% of injured endoscopists used practice modifications in response to injuries. Specific treatments included medications (57%), steroid injection (27%), physiotherapy (45%), rest (34%), splinting (23%), and surgery (13%). LIMITATIONS: Self-reported data of endoscopy-related injury. CONCLUSION: Among endoscopists there is a high prevalence of injuries definitely or potentially related to endoscopy. Higher procedure volume, more time doing endoscopy per week, and cumulative years performing endoscopy are associated with more work-related injuries.

Cancer rehabilitation: increasing awareness and removing barriers.

It has been more than 30 years since Lehman et al. published research identifying rehabilitation problems encountered at different cancer sites, the need for rehabilitation services, and gaps in the delivery of rehabilitation care. The lack of identification of patient problems and the lack of appropriate referral by physicians unfamiliar with the concept of rehabilitation were identified as primary barriers to optimal delivery of rehabilitation care. These are frustratingly the same barriers to cancer rehabilitation we see today. Recommendations have been made for finding better methods for identifying and managing the broader effects of cancer and its treatment and for integrating a more holistic interdisciplinary approach during and after the treatment of patients with cancer. The purpose of this supplement was to increase awareness of the role of rehabilitation in cancer care among the public and among medical professionals, as well as to stimulate further interest and training in the field of cancer rehabilitation.

Normal motor nerve conduction studies using surface electrode recording from the supraspinatus, infraspinatus, deltoid, and biceps.

OBJECTIVE: Proximal peripheral nerve conduction studies can provide useful information to the clinician. The difficulty of measuring the length of the proximal nerve as well as a frequent inability to stimulate at 2 points along the nerve adds a challenge to the use of electrodiagnosis for this purpose. The purpose of this article is to present normal values for the suprascapular, axillary, and musculocutaneous nerves using surface electrodes while accounting for side-to-side variability. DESIGN: Prospective, observational study. SETTING: Patients were evaluated in outpatient, private practices affiliated with tertiary care systems in the United States and Malaysia. PARTICIPANTS: One hundred volunteers were recruited and completed bilateral testing. Exclusion criteria included age younger than 18 years; previous shoulder surgery/atrophy; symptoms of numbness, tingling, or abnormal sensations in the upper extremity; peripheral neuropathy; or presence of a cardiac pacemaker. METHODS: Nerve conduction studies to bilateral supraspinatus, infraspinatus, deltoid, and biceps brachii muscles were performed with documented technique. Distal latency, amplitude, and area were recorded. Side-to-side comparisons were made. A mixed linear model was fit to the independent variables of gender, race, body mass index, height, and age with each recorded value. MAIN OUTCOME MEASUREMENTS: Distal latency, amplitude, area, and side-to-side variability of nerve conduction studies of the suprascapular, axillary, and musculocutaneous nerves with correlation to significant independent variables. RESULTS: Data are presented showing normal distal latency, amplitude, and area values subcategorized by clinically significant variables, as well as acceptable side-to-side variability. Increased height correlated with increased distal latency in all the nerves tested. Amplitudes were larger in the infraspinatus recordings from women, while the amplitudes from the biceps and deltoid were greater in men. A larger body mass index was associated with a smaller amplitude in the deltoid in men. No correlations were seen with age or race. CONCLUSION: Normative values for distal latency, amplitude, duration, and area were developed for proximal nerve conductions to the axillary, musculocutaneous, and suprascapular nerves. Simple surface electrode placement allows for easy reproduction of the authors' techniques. This is a useful standard to facilitate evaluation of these proximal peripheral nerves.

Sacroiliac joint pain: anatomy, biomechanics, diagnosis, and treatment.

The sacroiliac joint is an underappreciated cause of low back and buttock pain. It is thought to cause at least 15% of low back pain. It is more common in the presence of trauma, pregnancy, or in certain athletes. The pelvic anatomy is complex, with the joint space being variable and irregular. The joint transmits vertical forces from the spine to the lower extremities and has a role in lumbopelvic dynamic motion. History and physical examination findings can be helpful in screening for sacroiliac joint pain, but individual provocative maneuvers have unproven validity. Fluoroscopically guided injections into the joint have been found to be helpful for diagnostic and therapeutic purposes. Conservative treatment, which also can include joint mobilization, antiinflammatory medicines, and sacroiliac joint belts, generally is effective. Surgical arthrodesis should be considered a procedure of last resort.

Fencing.

Fencing is a sport in which two people attempt to score points by making their weapon (epee, foil, or saber) contact their opponent. The most common types of injury seen in fencing are weapon injuries; strains, sprains, and trauma; and nontraumatic injuries, the pathologic findings of which are discussed in this article.

Revolutionary advances in medical waste management. The Sanitec system.

It is the purpose of this collective review to provide a detailed outline of a revolutionary medical waste disposal system that should be used in all medical centers in the world to prevent pollution of our planet from medical waste. The Sanitec medical waste disposal system consists of the following seven components: (1) an all-weather steel enclosure of the waste management system, allowing it to be used inside or outside of the hospital center; (2) an automatic mechanical lift-and-load system that protects the workers from devastating back injuries; (3) a sophisticated shredding system designed for medical waste; (4) a series of air filters including the High Efficiency Particulate Air (HEPA) filter; (5) microwave disinfection of the medical waste material; (6) a waste compactor or dumpster; and (7) an onboard microprocessor. It must be emphasized that this waste management system can be used either inside or outside the hospital. From start to finish, the Sanitec Microwave Disinfection system is designed to provide process and engineering controls that assure complete disinfection and destruction, while minimizing the operator's exposure to risk. There are numerous technologic benefits to the Sanitec systems, including environmental, operational, physical, and disinfection efficiency as well as waste residue disinfection. Wastes treated through the Sanitec system are thoroughly disinfected, unrecognizable, and reduced in volume by approximately 80% (saving valuable landfill space and reducing hauling requirements and costs). They are acceptable in any municipal solid waste program. Sanitec's Zero Pollution Advantage is augmented by a complete range of services, including installation, startup, testing, training, maintenance, and repair, over the life of this system. The Sanitec waste management system has essentially been designed to provide the best overall solution to the customer, when that customer actually looks at the total cost of dealing with the medical waste issue. The Sanitec system is the right choice for healthcare and medical waste professionals around the world.

Reference values for median nerve conduction to the pronator quadratus.

OBJECTIVE: To derive a normative database for nerve conduction values of the median nerve to the pronator quadratus using a large and varied subject population. DESIGN: Descriptive study. SETTING: Private office or university-based clinic. PARTICIPANTS: Volunteers (N=207), recruited, without risk factors for neuropathy. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Onset latency, duration, amplitude, and area were recorded for all subjects. Side-to-side variability was calculated and the normative ranges were derived (97th percentile of observed values). RESULTS: Because the latencies increased with longer distances (longer forearms), the data were divided into 3 categories. The mean latency for those subjects whose distance from stimulator to recording electrode was 23 cm or less was 3.8+/-0.4 ms; the comparable values for those subjects with distances of 23.5 to 24.5 cm was 4.0+/-0.4 ms; and for those with distances of 25 cm and more, 4.5+/-0.4 ms. The amplitude and area varied with age. The mean amplitude for those subjects under 60 years of age was 4.4+/-1.8 mV, while those 60 years and over had an amplitude of 3.7+/-1.7 mV. The upper limit of normative side-to-side variability for latency was 0.6 ms, and the upper limit decrease in amplitude from 1 side to the other was 37%. CONCLUSIONS: This study establishes normative values for the median motor nerve conduction to the pronator quadratus.

Establishing improved normal values for nerve conduction studies.

Nerve conduction studies are commonly performed to diagnose injuries of the peripheral nerves. In the past, normal ranges have been derived on relatively small samples of normal subjects. These ranges were often suboptimal for clinical use. Therefore, this series of articles was created to establish an improved database of normative values. It highlights the key contributions of a number of authors. In this foreword, the contributions of the various authors to the special issue on the development of an improved database for nerve conduction studies are described. The authors are introduced, including their training, gifts, and which articles they were involved in writing. In addition, there is a brief review of each of the articles in this special supplement. The fundamentals of ulnar motor nerve conduction to the first dorsal interosseous muscle are described, as is the contribution of Nate Prahlow, MD. In addition, the median motor nerve conduction to the pronator teres muscle and flexor carpi radialis muscle is highlighted including the contributions of Brian Foley, MD. The radial sensory nerve and dorsal ulnar cutaneous sensory nerve studies are described, as well as the contributions of Van Evanoff, Jr., MD, in creating this research. Median motor conduction to the lumbrical muscles and ulnar motor conduction to the palmar interosseous muscles are described, again highlighting the contributions of Dr. Foley. In addition, medial and lateral antebrachial cutaneous nerve studies are described, along with the contributions of Dr. Nathan Prahlow. Median and ulnar sensory conduction studies recording from the fourth digit, as well as median and radial sensory conduction to the first digit, are described, as are the contributions of James Lohman, MD, and Andrew Berkson, DO. The side-to-side differences in median and ulnar sensory conduction studies and the importance of performing such studies are described, as are the contributions in this research of Dr. Nathan Prahlow and Elizabeth Grossart, MD. Lastly, median and ulnar sensory amplitude differences are described, including the contributions of Dr. Zaliha Omar, Dr. Andrew Berkson, and Doug Mottley, MD.

Ulnar nerve motor conduction to the first dorsal interosseous muscle.

The ulnar motor study to the abductor digiti minimi (ADM) is commonly performed, but does not test the terminal deep palmar branch of the ulnar nerve. Although damage to the ulnar nerve most often occurs at the elbow, the damage may occur elsewhere along the course of the nerve, including damage to the deep palmar branch. Ulnar conduction studies of the deep branch have been performed with recording from the first dorsal interosseous (FDI) muscle. These studies have used differing methodologies and were mostly limited by small sample size. The aim of this study was to develop a normative database for ulnar nerve conduction to the FDI. A new method of recording from the FDI was developed for this study. It utilizes recording with the active electrode over the dorsal first web space, with the reference electrode placed at the fifth metacarpophalangeal joint. This technique reliably yields negative takeoff measurements. An additional comparison was made between ulnar motor latency with recording at the ADM and with recording at the FDI. For this study, 199 subjects with no risk factors for neuropathy were tested. The latency, amplitude, area, and duration were recorded. The upper limit of normal (ULN) was defined as the 97th percentile of observed values. The lower limit of normal (LLN) was defined as the 3rd percentile of observed values. For the FDI, mean latency was 3.8 +/- 0.5 ms, with a ULN of 4.7 ms for males, 4.4 ms for females, and 4.6 ms for all subjects. Mean amplitude was 15.8 +/- 4.9 mV, with a LLN of 5.1 for all subjects. Side-to-side differences in latency to the FDI, from dominant to nondominant hands, was -0.1 +/- 0.4 ms, with a ULN of 0.8 ms. For the amplitude, up to a 52% decrease from side to side was normal. For the same-limb comparison of the FDI and ADM, the mean latency difference was 0.6 +/- 0.4 ms, with a ULN increase of 1.3 ms for latency to the ADM versus the FDI.

Establishing normal values of the proximal median motor nerve-a study of the pronator teres and flexor carpi radialis in healthy volunteers.

The importance of normative peripheral nerve data is increasing due to advances in medical implantation, microsurgical suturing, and tubulization repair techniques. Because the median nerve is often affected, its normal values must be reliable. Although the distal portion of the median nerve has been well studied using electrodiagnostic methods, the proximal forearm segment has not. This study establishes a normative database for median nerve conduction to the pronator teres (PT) and to the flexor carpi radialis (FCR). Two hundred-eight asymptomatic subjects were studied using proximal median motor stimulation at 10 cm. Latencies, amplitudes, areas, and durations were recorded. To the pronator teres: The upper limit for normal (ULN) motor latency was 3.5 ms (2.9 +/- 0.3 ms). The side-to-side latency difference was

Radial versus dorsal ulnar cutaneous sensory studies.

Peripheral nerves injuries are unfortunately common. Neuropathy may result from trauma, entrapment, metabolic or hereditary disturbances, inflammatory processes, iatrogenic injury from medical implants, and several other causes. We set out to create a large normative database for radial and dorsal ulnar cutaneous (DUC) sensory studies. Because comparison between two nerves of the same limb can be useful in detecting pathology, we also compared the latencies between the two nerves. Data were collected on both nerves using a 10-cm antidromic technique while controlling for temperature. Included subjects were asymptomatic: radial sensory studies were performed on 212 volunteers, DUC sensory studies were performed on 194 volunteers, and both studies were performed on 159 volunteers. Data were collected for onset and peak latencies, onset-to-peak and peak-to-peak amplitudes, area, rise time, and duration. Side-to-side differences were investigated. The data were analyzed to determine whether age, race, gender, height, weight, or body mass index (BMI) (kg/m2) correlated with different results. Differences in latencies between the nerves were analyzed as were side-to-side differences. Mean values for radial and DUC nerves, respectively, were found to be as follows: onset latency 1.9 +/- 0.2 ms and 1.8 +/- 0.3 ms, peak latency 2.4 +/- 0.2 ms and 2.3 +/- 0.4 ms, onset-to-peak amplitude 29 +/- 13 muV and 17 +/- 10 muV, peak-to-peak amplitude 33 +/- 14 muV and 20 +/- 13 muV, and area 18 +/- 7 nVs and 11 +/- 7 nVs. Mean rise time (0.5 +/- 0.1 ms) and duration (1.2 +/- 0.2 ms) were identical for both nerves. The upper limit of normal (ULN) side-to-side difference in peak latency was 0.3 ms for the radial and 0.4 ms for the DUC study. The ULN drop in peak-to-peak amplitude from one side to the other was 54% for the radial and 67% for the ulnar study. Increasing age, male gender, and increasing BMI (radial only) were associated with lower amplitudes and area, though the effects were clinically insignificant. The ULN increase in both radial-versus-DUC and DUC-versus-radial peak latency was 0.4 ms. In conclusion, a large normative database for the radial and DUC sensory studies has been derived that will assist in the diagnosis of peripheral neuropathy from a variety of etiologies. Side-to-side and internerve comparisons were also made.

Establishing normal nerve conduction values- lumbrical and interosseous responses.

OBJECTIVE: The importance of normative peripheral nerve data is increasing due to the advances in medical implantation, microsurgical suturing, and tubulization repair techniques. Because the median and ulnar nerves are often affected, their normal values must be reliable. The objective of this study was to create a larger database of normative values for the first and second lumbrical responses. The differences between the second lumbrical response and the interosseous response were also studied. BACKGROUND: The available literature is lacking in sample size and rigor, preventing reliable interpretations of normal values. METHODS: One hundred ninety-six asymptomatic subjects without risk factors for neuropathy were recruited and tested. Stimulations were performed with recording at the first lumbrical, second lumbrical, and interosseous muscles. RESULTS: Mean latency to the first lumbrical was 3.6 +/- 0.4 ms. Mean amplitude was 2.5 +/- 2.0 mV. The mean difference between latencies to the first lumbrical and second lumbrical was 0.1 +/- 0.3 ms, with the second lumbrical usually being the larger value. The mean difference between latencies to the abductor pollicic brevis (APB) and the first lumbrical was 0.2 +/- 0.4 ms, with the APB latency usually being the larger value. Mean latency to the second lumbrical was 3.7 +/- 0.4 ms and to the interosseous was 3.1 +/- 0.3 ms. Mean amplitude to the second lumbrical was 3.0 +/- 2.0 mV and to the interosseous was 6.9 +/- 2.3 mV. The mean difference between latencies to the second lumbrical and interosseous was 0.4 +/- 0.4 ms, with the second lumbrical usually being the larger value. The upper limit of normal increase of latency of the second lumbrical over the interosseous was 1.2 ms. The upper limit of normal increase of latency in subjects for which the interosseous latency exceeded the second lumbrical was 0.2 ms. CONCLUSIONS: This study provides a large normative database for nerve conduction studies to the first and second lumbricals, as well as to the second interosseous muscle.

An antidromic study of the medial antebrachial cutaneous nerve, with a comparison of the differences between medial and lateral antebrachial cutaneous nerve latencies.

Electrodiagnostic study of the medial antebrachial cutaneous (MAC) and lateral antebrachial cutaneous (LAC) nerves is not routinely undertaken. Pathology of either nerve or of the brachial plexus may occur from a variety of causes. Iatrogenic injury of these nerves has been rarely reported, but potential exists for nerve damage with a number of medical procedures, implants, or surgeries in the flexor forearm. In any of these situations, nerve conduction studies on the MAC and the LAC can be of benefit. Previous studies have reported normal values and examined side- to-side differences in the LAC, but have not compared the latencies of the MAC to the LAC in the same limb. This study establishes normal nerve conduction study values for the MAC from 207 subjects with no risk factors for neuropathy, using a 10-cm distance and an antidromic technique. It also examines both side-to-side differences in the MAC and same-limb differences between the MAC and LAC. For this study, the upper limit of normal (ULN) was defined as the 97th percentile of observed values. The lower limit of normal (LLN) was defined as the 3rd percentile of observed values. The onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, rise time, and duration were recorded. For the MAC, the mean onset latency was 1.7 +/- 0.2 ms, with a ULN of 2.0 ms. Mean peak latency was 2.2 +/- 0.2 ms, with a ULN of 2.6 ms. Onset-to-peak amplitude was 13 +/- 7 muV, with a LLN of 4 muV. Peak-to-peak amplitude was 10 +/- 7 muV, with a LLN of 3 muV. Side-to-side differences in MAC onset and peak latencies were 0.0 +/- 0.2 ms, with a ULN of 0.3 ms. Up to a 67% side-to-side decrease in MAC onset-to-peak amplitude was within the normal range. A 78% side- to-side decrease in MAC peak-to-peak amplitude was within the normal range. For the same-limb comparison of the MAC and the LAC, both onset and peak latencies had a mean difference of 0.0 +/- 0.2 ms and a ULN of 0.3 ms, regardless of whether the MAC or the LAC had the longer latency.

Median and ulnar antidromic sensory studies to the fourth digit.

The literature documents multiple reports of neurological injury resulting from both the implantation and the removal of orthopedic devices. These injuries can be easily and objectively evaluated with nerve conduction studies. This study was undertaken to derive a normative database for median and ulnar sensory conduction studies to the fourth digit. Testing was done utilizing a 14-cm antidromic technique on 192 asymptomatic subjects with no risk factors for neuropathy. The subjects were studied bilaterally. Onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, rise time, and duration were recorded. Increasing age and body mass index were associated with decreasing amplitudes and area. No other demographic factors correlated with differences in waveform measurements. Mean onset latency was 2.7 +/- 0.3 ms for the median nerve and 2.6 +/- 0.2 for the ulnar nerve. Mean peak latency was 3.4 +/- 0.3 ms for the median nerve and 3.3 +/- 0.3 ms for the ulnar nerve. Mean onset-to-peak amplitude was 21 +/- 12 muV for the median nerve and 23 +/- 12muV for the ulnar nerve. Mean peak-to-peak amplitude was 34 +/- 20 muV for the median nerve and 36 +/- 23 muV for the ulnar nerve. Mean area was 25 +/- 17 nVs for the median nerve and 28 +/- 19 nVs for the ulnar nerve. Mean rise time was 0.7 +/- 0.1 ms for the median nerve and 0.7 +/- 0.2 ms for the ulnar nerve. Mean duration was 1.9 +/- 0.4 ms for the median nerve and 1.9 +/- 0.5 ms for the ulnar nerve. The mean difference in onset and peak latency between the median and ulnar nerves (median minus ulnar) was 0.1 +/- 0.2 ms. The upper limit of normal difference of median greater than ulnar onset and peak latency was 0.5 ms. The upper limit of normal difference of ulnar greater than median onset latency was 0.2 ms (0.3 ms for peak latency). The upper limit of normal drop in median peak-to-peak amplitude from one side to the other was 56%. For the ulnar nerve this value was 73%.

Comparison of median and radial sensory studies to the thumb.

There are multiple reports of neurological injury from both the implantation and the removal of devices utilized in orthopedics. Nerve conduction studies can be a valuable tool in evaluating the acuity, severity, and prognosis of these injuries, as well as in tracking their course. This study was undertaken in an effort to create a large normative database for examining median and radial sensory nerve conduction studies to the first digit. An antidromic technique was employed utilizing a 10-cm distance between the stimulating and recording electrodes. Two hundred three asymptomatic volunteers were tested. Onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, rise time, and duration of the waveforms were measured. Males, older subjects, and those with higher body mass index (BMI) were found to have lower amplitude and area on the median nerve studies. Age was the only variable which demonstrated significant correlation with differing results on the radial nerve studies. Mean onset latencies were 2.1 +/- 0.2 ms for the median nerve and 2.0 +/- 0.2 ms for the radial nerve. Mean peak latencies were 2.7 +/- 0.2 ms for the median nerve and 2.6 +/- 0.2 ms for the radial nerve. Mean peak-to-peak amplitude for the median nerve was 45 +/- 24 muV and for the radial nerve was 12 +/- 9 muV. The upper limit of normal difference in median-versus-radial onset latency was 0.5 ms (0.6 ms for peak latency). The upper limit of normal difference in radial-minus-median onset latency was 0.3 ms (0.4 ms for peak latency).

Acceptable differences in sensory and motor latencies between the median and ulnar nerves.

The median and ulnar nerves are often studied during the same electrodiagnostic examination. The sensory and motor latencies of these nerves have been compared to detect a common electrodiagnostic entity: median neuropathy at the wrist. However, this comparison could also be used to diagnose less common ulnar pathology. For this reason, it is important to establish normal values for comparing median and ulnar sensory and motor latencies. Previous research deriving these differences in latency has had some limitations. The purpose of this study was to derive an improved normative database for the acceptable differences in latency between the median and ulnar sensory and motor nerves of the same limb. Median and ulnar sensory and motor latencies were obtained from 219 and 238 asymptomatic risk-factor-free subjects, respectively. An analysis of variance was performed to determine whether physical characteristics, specifically age, race, gender, height, or body mass index (as an indicator of obesity), correlated with differences in latency. Differences in sensory latencies were unaffected by physical characteristics. The upper limit of normal difference between median and ulnar (median longer than ulnar) onset latency was 0.5 ms (97th percentile), whereas the peak latency value was 0.4 ms (97th percentile). The upper limit of normal difference between ulnar-versus-median (ulnar longer than median) onset latency was 0.3 ms (97th percentile), whereas the peak-latency value was 0.5 ms (97th percentile). The mean difference in motor latencies correlated with age, with older subjects having a greater variability. In subjects aged 50 and over, the mean difference in median-versus-ulnar latency was 0.9 ms +/- 0.4 ms. The upper limit of normal difference (median longer than ulnar) was 1.7 ms (97th percentile). The upper limit of normal ulnar motor latency is attained if the ulnar latency comes within 0.3 ms of the median latency. In individuals less than 50 years of age, the mean difference in latency was 0.6 ms +/- 0.4 ms, with the median latency usually being greater than the ulnar. The upper limit of normal difference (median longer than ulnar) was 1.4 ms (97th percentile), whereas the upper limit of ulnar latency relative to median latency was attained if the ulnar latency was equal to median latency.