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 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.

Median and Ulnar 14-cm Antidromic Sensory Studies to the Third and Fifth Digits-A Comparison of Amplitude

There are multiple reports of peripheral nerve injury following the implantation or removal of surgical hardware. Electrodiagnostic testing can be useful in assessing the chronicity, severity, and recovery of such a nerve injury. The purpose of this study is to establish a normative data set to allow for comparison of median and ulnar antidromic sensory peak-to-peak amplitude values. Median and ulnar antidromic sensory studies to digits 3 and 5 are commonly performed in electrodiagnosis to aid in the diagnosis of a variety of clinical conditions. Numerous studies have examined normal latency and amplitude values for these studies. To our knowledge there has been one other study that compared the relationship between median and ulnar sensory amplitude results taken from the same limb. That study had limited generalizability to the population at large. One hundred-nineteen volunteers were tested with antidromic sensory technique to digits 3 and 5 at 14-cm stimulation distance. Peak latency and peak-to-peak amplitude were recorded. Possible relationships between age, gender, height, weight, BMI, and median and ulnar amplitude were examined through simple linear regressions. Age, weight, height, and BMI were all found to negatively correlate with both median and ulnar amplitude. Female subjects were found to have statistically greater median and ulnar amplitudes than male subjects. Factors were said to be statistically significant at the P </= 0.05 level. The mean median peak latency was 3.2 +/- 0.3 ms. The mean ulnar peak latency was 3.2 +/- 0.4 ms. The mean median peak-to-peak amplitude was 87 +/- 36 muV. The mean ulnar peak-to-peak amplitude was 72 +/- 34 muV. The upper limit of normal difference (2.5th percentile) in median-versus-ulnar amplitude was a 56% drop from median-to-ulnar amplitude, or a 59% drop from ulnar-to-median amplitude. This allows for amplitude comparisons to be made between these two nerves.

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%.

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.

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.

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.

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 </= 0.5 ms. Overall, the lower limit of normal (LLN) amplitude was 2.2 mV. However, this decreased to 1.5 mV in the over-50 age group. To the flexor carpi radialis: The ULN motor latency was 3.6 ms (2.8 +/- 0.4 ms). The side-to-side latency difference was </= 0.7 ms. Overall, the LLN amplitude was 2.3 mV. However, this decreased to 1.7 mV in the over-50 group. This study produced a large database of normal results for the median motor nerve conduction to the pronator teres and to the flexor carpi radialis. The 10-cm techniques are easily reproducible and helpful when evaluating this portion of the median nerve.

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.

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.

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.

Childhood obesity: a simple equation with complex variables

The prevalence of childhood obesity is rising rapidly, as are the associated medical complications, including type 2 diabetes, hypertension, and coronary heart disease. This has significant medical and socioeconomic implications. The definition of obesity in adults is based on body mass index (BMI), which has been correlated with morbidity and mortality. Similarly, the definition of childhood obesity is currently based on BMI; however, there are currently no data to relate morbidity and mortality to BMI values in children. The known and potential causes of childhood obesity are many, but they can be categorized as genetic, endocrine, prenatal/early life, physical activity, diet, and socioeconomic. These factors influence the basic equation: energy input = energy output. Imbalances in this equation can result in obesity. Here we present a review of recent literature and highlight the etiologies, certain complications, and potential prevention and treatment strategies of childhood obesity.

The Sit & Stand chair. A revolutionary advance in adaptive seating systems

A major factor governing independence for the elderly and persons with disabilities is the ability to stand from a chair. Factors such as pain, reduced joint range of motion, stiffness, and muscle weakness frequently limit the ability to stand. Sit-to-stand position is even further reduced in patients whose hands and shoulders are afflicted with rheumatoid arthritis. When achieving a sit-to-stand position in the elderly and persons with disabilities, there is considerable risk of the individual falling and sustaining bone fracture. The purposes of this scientific report are to achieve the following goals: (1) to provide a narrative discussion of the senior author's contributions to furniture manufacturing as well as his successful patent application for the SIT & STAND chair, (2) to describe the steps involved in the development of the SIT & STAND prototype, and (3) to examine the performance of the SIT & STAND chair in assisting the elderly or persons with disabilities in achieving a sit-to-stand position. The invention of the SIT & STAND chair by the senior author, Michael Galumbeck, was a culmination of his lifelong interest in adaptive seating systems. His electrically operated chair has the unique ability to assist the occupant to achieve safely a sit-to-stand position. The rear portion of his chair remains in a fixed position to support the buttocks of the user during mechanical lift. The front portion of the seat folds down incrementally as the chair rises to allow the feet of the user to be positioned in a more posterior position firmly on the floor. Using its actuator, the height that the chair rises will vary with the length of the legs of the occupant. Using the drawing program Solid Works (Solid Works, Concord, Massachusetts), drawings of the chair were made. To visualize the operation and performance of the chair, separate drawings were made in the lateral position. The prototype of the SIT & STAND chair was manufactured with an electric actuator that allows elevation of the back portion of the seat. The design of this chair ensured that there were no pinch points that could endanger the user or assistant. Its framework ensured that it was stable and did not tip over. After the prototype chair is manufactured, it is being sent to Underwriters Laboratory Inc. (Los Angeles, California) for review and certification. The performance of the SIT & STAND chair was determined in a clinical study involving seven elderly or disabled individuals who complained of difficulty in rising from a chair from a seated position. During each performance evaluation, a mechanical chest and shoulder harness attached to an overhead sling encircled the individual to ensure that he/she would not fall. In the first part of the evaluation, these individuals were asked to achieve a standing position after being seated in the SIT & STAND chair without the use of the actuator. Three individuals were unable to achieve a standing position, while four achieved this standing position with considerable difficulty and potential instability. When these participants used the SIT & STAND chair with the use of the electrical actuator, all individuals achieved a standing position without difficulty or instability. All individuals expressed disappointment that the SIT & STAND chair was not commercially available for them to purchase and use in their homes. Because the SIT & STAND chair allows the individual to achieve a standing position without assistance, the SIT & STAND chair has other potential benefits not evaluated in this study. The beneficial effects of standing have been documented by comprehensive scientific studies. These benefits include reduction of seating pressure, decreased bone demineralization, increased bladder pressure, enhanced circulatory regulation, reduction in muscular tone, decrease in upper extremity muscle stress, and participation in activities of daily living. Another irrefutable benefit of the SIT & STAND chair is that the chair eliminates the need for physical assistance from family members or health care personnel, preventing the development of disabling back injuries in personal care assistants. In addition, the SIT & STAND chair entirely removes the risk of pain or harm to the individual, which sometimes occurs with manual assist to stand, such as dislocation or fracture of frail shoulders with the under-axilla lift. Realizing the medical benefits of the SIT & STAND chair, Aetna completed a clinical policy bulletin that states that the seat lift mechanism is a medically necessary durable medical product. On the basis of this extensive product and performance evaluation, we recommend the SIT & STAND chair for the elderly as well as persons with disability to safely achieve a sit-to-stand position.

Devastating Injuries in Healthcare Workers: Description of the Crisis and Legislative Solution to the Epidemic of Back Injury from Patient Lifting

The purpose of this report is to describe a crisis in healthcare, disabling back injuries in US healthcare workers. In addition, outlined is the proven solution of safe, mechanized, patient lifting, which has been shown to prevent these injuries. A "Safe Patient Handling--No Manual Lift" policy must be immediately instituted throughout this country. Such a policy is essential to halt hazardous manual patient lifting, which promotes needless disability and loss of healthcare workers, pain and risk of severe injury to patients, and tremendous waste of financial resources to employers and workers' compensation insurance carriers. Healthcare workers consistently rank among top occupations with disabling back injuries, primarily from manually lifting patients. Back injury may be the single largest contributor to the nursing shortage. Reported injuries to certified nursing assistants are three to four times that of registered nurses. A national healthcare policy for "Safe Patient Handling--No Manual Lift" is urgently needed to address this crisis. Body mechanics training is ineffective in prevention of back injury with patient lifting. Mandated use of mechanical patient lift equipment has proven to prevent most back injury to nursing personnel and reduce pain and injury to patients associated with manual lifting. With the national epidemic of morbid obesity in our country, innovative devices are available for use in emergency medical systems and hospitals for patient lifting and transfer without injury to hospital personnel. The US healthcare industry has not voluntarily taken measures necessary to reduce patient handling injury by use of mechanical lift devices. US healthcare workers who suffer disabling work-related back injuries are limited to the fixed, and often inadequate, relief which they may obtain from workers' compensation. Under workers' compensation law, healthcare workers injured lifting patients may not sue their employer for not providing mechanical lift equipment. Discarding healthcare workers disabled by preventable back injuries is an abuse which legislators must remedy. In addition, Medicare reimbursement policies must also be updated to allow the disabled community to purchase electrically operated overhead ceiling lifts. The US lags far behind countries with legislated manual handling regulations and "No Lifting" nursing policies. England and Australia have had "No Lifting" nursing policies in place since 1996 and 1998, respectively. The National Occupational Research Agenda (NORA) recognized a model in 2003 for reduction of back injuries to nursing staff in US healthcare facilities. Also in 2003, the American Nurses Association called for elimination of manual patient handling because it is unsafe and causes musculoskeletal injuries to nurses. The first state legislation for safe patient handling passed both houses in California but was vetoed by the Governor in September 2004. California and other states are preparing to (re)introduce legislation in January 2005. A national, industry-specific policy is essential to quell the outflow of nursing personnel to disability from manual patient lifting.

Technological advances in powered wheelchairs

During the last 40 years, there have been revolutionary advances in power wheelchairs. These unique wheelchair systems, designed for the physically immobile patient, have become extremely diversified, allowing the user to achieve different positions, including tilt, recline, and, more recently, passive standing. Because of this wide diversity of powered wheelchair products, there is a growing realization of the need for certification of wheeled mobility suppliers. Legislation in Tennessee (Consumer Protection Act for Wheeled Mobility) passed in 2003 will ensure that wheeled mobility suppliers must have Assistive Technology Supplier certification and maintain their continuing education credits when fitting individuals in wheelchairs for long-term use. Fifteen other legislative efforts are currently underway in general assemblies throughout the US. Manufacturers, dealers, hospitals, and legislators are working toward the ultimate goal of passing federal legislation delineating the certification process of wheeled mobility suppliers. The most recent advance in the design of powered wheelchairs is the development of passive standing positions. The beneficial effects of passive standing have been documented by comprehensive scientific studies. These benefits include reduction of seating pressure, decreased bone demineralization, increased bladder pressure, enhanced orthostatic circulatory regulation, reduction in muscular tone, decrease in upper extremity muscle stress, and enhanced functional status in general. In February 2003, Permobil, Inc., introduced the powered Permobil Chairman 2K Stander wheelchair, which can tilt, recline, and stand. Other companies are now manufacturing powered wheelchairs that can achieve a passive standing position. These wheelchairs include the Chief SR Powerchair, VERTRAN, and LifeStand Compact. Another new addition to the wheelchair industry is the iBOT, which can elevate the user to reach cupboards and climb stairs but has no passive standing capabilities. In addition, the physically immobile patient must be seated on an ERGODYNAMIC Seating System 2000, which is inflated by the alternating pressure compressor 8080. This seating system has a deep center seam between the two ischial-support chambers, which provides a recess for the coccyx. The pre-ischial crossbar compartment inflates during each cycle to prevent the pelvis from slipping forward. It is essential that the physician of the immobile patient order two ERGODYNAMIC Seating Systems 2000 because the patient must have an additional seating system in the case one leaks. Moreover, two compressors are necessary because each compressor must be serviced after 2500 hours of use. For the protection of the consumer, these pressure relief systems must be supplied and serviced by a Certified Rehabilitation Technology Supplier such as Wheelchair Works Inc. Despite the indisputable scientific evidence of the medical benefits of passive standing for the immobile user, few individuals have access to these revolutionary wheelchairs. Consequently, it is mandatory that the medical community, headed by specialists in physical and occupational therapy as well as rehabilitation medicine, CRTS, and manufacturers collaborate in a national education campaign to convince Medicare/Medicaid and all commercial insurance companies to approve immediately these assisted technologies. This program is essential so that the physically immobilized patient can achieve the undisputed physical benefits of passive standing.

Optimal interelectrode distance in sensory and mixed compound nerve action potentials: 3- versus 4-centimeter bar electrodes

OBJECTIVE

To evaluate the amplitude and latency for 3-cm versus 4-cm distance between the active and reference electrodes (electrode separation) used to obtain normative sensory and mixed compound nerve action potential data.

DESIGN

Prospective, unblinded clinical test evaluating 3 nerves: mixed median and ulnar across wrist (8 cm), and radial antidromic sensory (10 cm).

SETTING

University and private practice electrodiagnostic laboratories.

PARTICIPANTS

One hundred six adult volunteers without known neuropathy.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Peak-to-peak amplitude and onset and peak latencies.

RESULTS

Mean onset latencies +/- standard deviation (SD) were equal for 3-cm and 4-cm separations (median, 1.6+/-0.2 ms; radial, 1.7+/-0.2 ms; ulnar, 1.5+/-0.2 ms). Mean peak latencies were also equal for 3-cm and 4-cm separation for radial (2.2+/-0.2 ms) and ulnar (1.9+/-0.2 ms) studies but differed for the median study (3 cm, 2.0+/-0.3 ms; 4 cm, 2.1+/-0.3 ms; P<.0001). Mean amplitudes +/- SD with 3-cm and 4-cm separations were, respectively, 101+/-39 microV and 103+/-39 microV (P=.0434) for the median, 47+/-17 microV and 48+/-16 microV (P=.0209) for the radial, and 52+/-28 microV and 55+/-29 microV (P=.0001) for the ulnar study. These differences were statistically significant but clinically insignificant.

CONCLUSIONS

The results support a hypothesized difference in amplitude but not latency between 3- and 4-cm separation. Clinically, however, the magnitude was insignificant.

Strategies to Reduce Hyperthermia in Ambulatory Multiple Sclerosis Patients

Approximately 400,000 Americans have multiple sclerosis. Worldwide, multiple sclerosis affects 2.5 million individuals. Multiple sclerosis affects two to three times as many women as men. The adverse effects of hyperthermia in patients with multiple sclerosis have been known since 1890. While most patients with multiple sclerosis experience reversible worsening of their neurologic deficits, some patients experience irreversible neurologic deficits. In fact, heat-induced fatalities have been encountered in multiple sclerosis patients subjected to hyperthermia. Hyperthermia can be caused through sun exposure, exercise, and infection. During the last 50 years, numerous strategies have evolved to reduce hyperthermia in individuals with multiple sclerosis, such as photoprotective clothing, sunglasses, sunscreens, hydrotherapy, and prevention of urinary tract infections. Hydrotherapy has become an essential component of rehabilitation for multiple sclerosis patients in hospitals throughout the world. On the basis of this positive hospital experience, hydrotherapy has been expanded through the use of compact aquatic exercise pools at home along with personal cooling devices that promote local and systemic hypothermia in multiple sclerosis patients. The Multiple Sclerosis Association of America and NASA have played leadership roles in developing and recommending technology that will prevent hyperthermia in multiple sclerosis patients and should be consulted for new technological advances that will benefit the multiple sclerosis patient. In addition, products recommended for photoprotection by The Skin Cancer Foundation may also be helpful to the multiple sclerosis patient's defense against hyperthermia. Infections in the urinary tract, especially detrusor-external sphincter dyssynergia, are initially managed conservatively with intermittent self-catheterization and pharmacologic therapy. In those cases, refractory to conservative therapy, transurethral external sphincterotomy followed by condom catheter drainage is recommended. However, if external urethral sphincterotomy fails to reduce residual urine and detrusor pressure, urinary diversion or bladder reconstruction may be necessary.

Pressure Ulcer Prevention

The purpose of this collective review is to outline the predisposing factors in the development of pressure ulcers and to identify a pressure ulcer prevention program. The most frequent sites for pressure ulcers are areas of skin overlying bony prominences. There are four critical factors contributing to the development of pressure ulcers: pressure, shearing forces, friction, and moisture. Pressure is now viewed as the single most important etiologic factor in pressure ulcer formation. Prolonged immobilization, sensory deficit, circulatory disturbances, and poor nutrition have been identified as important risk factors in the development of pressure ulcer formation. Among the clinical assessment scales available, only two, the Braden Scale and Norton Scale, have been tested extensively for reliability and/or validity. The most commonly used risk assessment tools for pressure ulcer formation are computerized pressure monitoring and measurement of laser Doppler skin blood flow. Pressure ulcers can predispose the patient to a variety of complications that include bacteremia, osteomyelitis, squamous cell carcinoma, and sinus tracts. The three components of pressure ulcer prevention that must be considered in any patient include management of incontinence, nutritional support, and pressure relief. The pressure relief program must be individualized for non-weight-bearing individuals as well as those that can bear weight. For those that can not bear weight and passively stand, the RENAISSANCE Mattress Replacement System is recommended for the immobile patient who lies supine on the bed, the stretcher, or operating room table. This alternating pressure system is unique because it has three separate cells that are not interconnected. It is specifically designed so that deflation of each individual cell will reach a ZERO PRESSURE during each alternating pressure cycle. The superiority of this system has been documented by comprehensive clinical studies in which this system has been compared to the standard hospital bed as well as to two other commercially available pressure relief mattresses. The most recent advance in pressure ulcer prevention is the development of the ALTERN8* seating system. This seating system provides regular periods of pressure relief and stimulation of blood flow to skin areas while users are seated. By offering the combination of pressure relief therapy and an increase in blood flow, the ALTERN8* reportedly creates an optimum pressure ulcer healing environment. Foam is the most commonly used material for pressure reduction and pressure ulcer prevention and treatment for the mobile individual. For those immobilized individuals who can achieve a passive standing position, a powered wheelchair that allows the individual to achieve a passive standing position is recommended. The beneficial effects of passive standing have been documented by comprehensive scientific studies. These benefits include reduction of seating pressure, decreased bone demineralization, increased blander pressure, enhanced orthostatic circulatory regulation, reduction in muscular tone, decrease in upper extremity muscle stress, and enhanced functional status in general. In the absence of these dynamic alternating pressure seating systems and mattresses, there are enormous medicolegal implications to the healthcare facility. Because there is not sufficient staff to provide pressure relief to rotate the patient every 2 hours in a hospital setting, with the exception of the intensive care unit, the immobile patient is prone to develop pressure ulcers. The cost of caring for these preventable pressure ulcers may now be as high as 60,000 dollars per patient. The occupational physical strain sustained by nursing personnel in rotating their patients has led to occupational back pain in nurses, a major source of morbidity in the healthcare environment.

Sural and saphenous 14-cm antidromic sensory nerve conduction studies

OBJECTIVE

To create a large database of normal values for the sural and saphenous nerve conduction studies and to compare the results for the two nerves.

DESIGN

Using a 14-cm antidromic technique, data were collected for onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, duration, side-to-side variability, and between-nerve variability. A total of 230 subjects were included in the study.

RESULTS

For the sural nerve, the upper limits of normal, defined as the 97th percentile of observed values, for onset latency, peak latency, and duration were 3.6, 4.5, and 2.1 msec, respectively. The comparable values for the saphenous nerve were 3.8, 4.4, and 1.9 msec, respectively. The lower limits of normal (third percentile) for sural onset-to-peak amplitude and peak-to-peak amplitude were 4 and 4 microV. The comparable values for the saphenous study were 2 and 1 microV. The upper limit of normal difference in onset latency between the two nerves was: saphenous 0.7 msec longer than sural or sural 0.3 msec longer than saphenous. The corresponding values for peak latency were: 0.6 and 0.5 msec.

CONCLUSION

Normal ranges are presented for a large database of subjects for the sural and saphenous nerve conduction studies.

Reference values for peroneal nerve motor conduction to the tibialis anterior and for peroneal vs. tibial latencies

OBJECTIVE

To generate a large normative database for the peroneal study to the tibialis anterior and to analyze differences between the peroneal latency to the extensor digitorum brevis and the tibial latency to the abductor hallucis.

DESIGN

A total of 244 asymptomatic subjects without risk factors for neuropathy were tested for latency, amplitude, area, duration, and nerve conduction velocity to the tibialis anterior. For the peroneal/tibial analysis, 221 subjects were included. Temperature control was used, and demographic characteristics were recorded.

RESULTS

Latency to the tibialis anterior increased and nerve conduction velocity decreased with increasing height. Amplitudes, area, and nerve conduction velocity were lower in older persons. The upper limits of normal (97th percentile) were 4.9 msec (latency) and 15.0 msec (duration). The lower limits of normal (3rd percentile) were 1.7 mV (amplitude), 6.8 microV/sec (area), and 43 m/sec (nerve conduction velocity). The upper limits of normal side-to-side difference was 1.2 msec (latency), 6.3 msec (duration), 50% (amplitude), 47% (area), and 20% (nerve conduction velocity). The upper limits of normal drop from below- to above-fibular-head stimulation was 36% (amplitude) and 43% (area). For the peroneal/tibial comparison, the upper limits of normal latency increase of peroneal over tibial was 1.8 msec and tibial over peroneal was 1.5 msec.

CONCLUSION

A large normative database was collected. Upper and lower limits of normal were calculated, and side-to-side differences were analyzed. For the peroneal/tibial comparison, an upper limits of normal difference was described.

An Introduction to Electromyography: An Invited Review

Electromyography is a complex diagnostic test that is useful in diagnosing many neuromuscular and musculoskeletal conditions. Physiatrists and neurologists become familiar with this test during their training, while other physicians have minimal or no exposure, outside of perhaps some basic physiology lectures. A review of the anatomy, physiology, and physics upon which electrodiagnostic testing is based and of the various techniques used during a study provides the necessary foundation for understanding and using study results. A discussion of the conditions for which electrodiagnostic testing is useful, including carpal tunnel syndrome, radiculopathy, peripheral neuropathy, and disorders of the neuromuscular junction, is included both to review these disorders and to encourage appropriate referral for electrodiagnostic study.

The evolution of glutathione metabolism in phototrophic microorganisms

Of the many roles ascribed to glutathione (GSH) the one most clearly established is its role in the protection of higher eucaryotes against oxygen toxicity through destruction of thiol-reactive oxygen byproducts. If this is the primary function of GSH then GSH metabolism should have evolved during or after the evolution of oxygenic photosynthesis. That many bacteria do not produce GSH is consistent with this view. In the present study we have examined the low-molecular-weight thiol composition of a variety of phototrophic microorganisms to ascertain how evolution of GSH production is related to evolution of oxygenic photosynthesis. Cells were extracted in the presence of monobromobimane (mBBr) to convert thiols to fluorescent derivatives, which were analyzed by high-pressure liquid chromatography. Significant levels of GSH were not found in the green bacteria (Chlorobium thiosulfatophilum and Chloroflexus aurantiacus). Substantial levels of GSH were present in the purple bacteria (Chromatium vinosum, Rhodospirillum rubrum, Rhodobacter sphaeroides, and Rhodocyclus gelatinosa), the cyanobacteria [Anacystis nidulans, Microcoleus chthonoplastes S.G., Nostoc muscorum, Oscillatoria amphigranulata, Oscillatoria limnetica, Oscillatoria sp. (Stinky Spring, Utah), Oscillatoria terebriformis, Plectonema boryanum, and Synechococcus lividus], and eucaryotic algae (Chlorella pyrenoidsa, Chlorella vulgaris, Euglena gracilis, Scenedesmus obliquus, and Chlamydomonas reinhardtii). Other thiols measured included cysteine, gamma-glutamylcysteine, thiosulfate, coenzyme A, and sulfide; several unidentified thiols were also detected. Many of the organisms examined also exhibited a marked ability to reduce mBBr to syn-(methyl,methyl)bimane, an ability that was quenched by treatment with 2-pyridyl disulfide or 5,5'-bisdithio-(2-nitrobenzoic acid) prior to reaction with mBBr. These observations indicate the presence of a reducing system capable of electron transfer to mBBr and reduction of reactive disulfides. The distribution of GSH in phototrophic eubacteria indicates that GSH synthesis evolved at or around the time that oxygenic photosynthesis evolved.

Preliminary electrophysiological characterization of functionally vestigial muscles of the head: potential for command signaling

In devastating neurological disorders, such as quadriplegia resulting from high-level spinal cord injury, it is essential to focus on functions that have been spared and optimally exploit them to enhance the individual's quality of life. It follows that certain muscles, which prior to the paralysis of much of the rest of the body seemed to have no useful function, might be used to provide unique signals to control assistive devices. This report presents preliminary electrophysiological data demonstrating potentially useful myoelectrical signals from 3 functionally vestigial muscles in humans; the posterior, anterior, and superior auricular muscles. In phylogenetically lower species, these muscles serve to position the ear to enhance hearing. The auricular muscles receive their major innervation from cranial nerve VII and should not be compromised by even high-level spinal cord lesions. In this study, it was found that the muscles could be voluntarily activated and, by standard surface-electrode recording, had potentials ranging to 680 microV in amplitude. Posterior auricular muscle potentials were used to command a paddle in a computer ping-pong task that employed a CyberLink interface. The t values for accuracy scores and ball hits were both significant at the p = .0001 level. These facts indicate that the auricular muscles may be useful for controlling assistive devices.

Ulnar 14-cm and 7-cm antidromic sensory studies to the fifth digit: reference values derived from a large population of normal subjects

The ulnar antidromic sensory conduction study to the fifth digit is commonly performed in clinical electrodiagnosis. Several authors have published normal ranges for this study, but these published reports have been limited by generally small sample sizes. The purpose of this article is to present a large database of normal ranges for this nerve study. After obtaining Institutional Review Board approval, 258 asymptomatic subjects were tested bilaterally with an ulnar antidromic sensory technique recording from the fifth digit. Stimulation was performed 7 cm and 14 cm proximal to the recording electrode. Onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, duration, and rise time were recorded. Side-to-side and 14- to 7-cm comparisons were made. A repeated measures analysis of variance was performed to determine whether any of the subjects' demographic characteristics of age, race, gender, height, or body mass index (kg/m2) were associated with different results for the nerve conduction measures. Increasing age and body mass index were found to correlate with decreasing amplitude and area. No other correlations were noted between the results and the physical characteristics. Mean onset latency was 1.4 +/- 0.2 ms at 7-cm and 2.6 +/- 0.2 ms at 14-cm stimulation. Mean peak latency was 2.0 +/- 0.2 ms at 7-cm and 3.4 +/- 0.3 ms at 14-cm stimulation. Mean onset-to-peak amplitude was 32 +/- 20 microV at 7-cm and 33 +/- 17 microV at 14-cm stimulation. Mean negative-to-positive-peak amplitude was 55 +/- 36 microV at 7-cm and 50 +/- 32 microV at 14-cm stimulation. Mean side-to-side difference for onset latency was 0 +/- 0.2 ms. Additional data is presented in the study.

Median nerve F-wave latencies recorded from the abductor pollicis brevis

This study was performed to create a normative database for median nerve F-wave responses for a large subject population so normal ranges could be created for subsets of the general population and the effect of various physical characteristics on F-wave results could be determined. One hundred ninety-five asymptomatic subjects without risk factors for neuropathy were recruited. Ten consecutive supramaximal stimuli were applied to the wrists of each arm to obtain median nerve F-wave results. The shortest F-wave latency (Fmin), mean latency (Fmean), range of latencies (Frange), and number of stimuli that resulted in F-wave recordings (Fpersist) were recorded. An analysis of variance revealed that age, gender, and height were associated with different results for Fmin and Fmean. For all subjects taken together, the mean Fmin was 26.8 +/- 2.4 ms. The mean Fmean was 28.3 +/- 2.6 ms, and the mean Frange was 3.4 +/- 1.9 ms. Five or more F-waves were elicited in 94% of the subjects. The mean side-to-side difference in Fmin was 0.2 +/- 1.2 ms. Additional findings are presented in the article.

Tibial nerve F-waves recorded from the abductor hallucis

The purpose of this study was to develop a large database of normal values for the tibial nerve F-wave. A total of 159 asymptomatic subjects without risk factors for neuropathy were recruited and had ten tibial F-waves performed on each leg. Data were collected for the shortest F-wave (Fmin), the mean F-wave (Fmean), and the range of F-waves (Frange). Age, gender, and height were associated with differences in the results. The mean Fmin was 50.8 +/- 5.3 ms. Mean Fmean was 53.0 +/- 5.6 ms and mean Frange was 4.5 +/- 2.4 ms. The mean side-to-side difference for Fmin was 0.6 +/- 2.3 ms and the mean side-to-side difference for Fmean was 0.4 +/- 2.5 ms.

Median 14-cm and 7-cm antidromic sensory studies to digits two and three

The purpose of this study was to derive a normative database for the median digital sensory conduction study using a large and varied subject population. Two hundred fifty-eight asymptomatic volunteers were tested with antidromic sensory technique at 14- and 7-cm distances to digits 2 and 3. Onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, rise time, and duration were recorded. A repeated analysis of variance was performed, with the nerve conduction study measures as the dependent variables and age, race, gender, body mass index, and height as the independent variables. Factors that were significant at the P < or = 0.01 level were used to create separate normal ranges. Both increasing age and increasing body mass index correlated with decreasing amplitudes and area. No other correlations were noted between the results and the physical characteristics. For digit 3, the mean 14-cm onset latency was 2.7 +/- 0.3 ms and mean peak latency was 3.4 +/- 0.3 ms. The mean onset-to-peak amplitude was 41 +/- 20 microV for all subjects taken together. Mean rise time was 0.7 +/- 0.1 ms and mean duration was 2.1 +/- 0.4 ms. Mean side-to-side difference in onset and peak latencies was 0.0 +/- 0.2 ms. The upper limits of normal side-to-side differences in amplitudes and area were approximately 50%-60%.

Median nerve motor conduction to the abductor pollicis brevis

The median motor conduction study to the abductor pollicis brevis is one of the most commonly performed electrodiagnostic studies, yet there is a need for a more comprehensive normative database for this test. Demographic subgroups of age, gender, and height need to be evaluated with a large enough sample size using modern statistical and electrodiagnostic techniques. In this study, 249 subjects were tested and the following were recorded: latency, amplitude, area, duration, and nerve conduction velocity (NCV). A repeated measures analysis of variance was performed with the waveform measures as the dependent variables and age, gender, and height as the independent variables. Factors that were significant at the P < or = 0.01 level were used to create separate normative databases. Gender was found to be associated with different results for latency and NCV. Age was found to be associated with different results for latency, amplitude, area, and NCV. Once these statistically significant factors were determined, Tukey adjusted pair-wise comparisons of least squares means were used to collapse categories (by decade for age) that were not significantly different from each other at the P < or = 0.05 level. Categories for measures that differed by clinically insignificant amounts (defined as 0.2 ms or less for time measures, 2 m/s or less for NCV, or 5% or less for amplitude and area) were combined as well. Side-to-side and proximal-to-distal differences were analyzed. The normal range was derived as mean +/- 2 standard deviations and at the 97th (third) percentiles of observed values. The findings are presented in this article but include a mean latency of 3.7 +/- 0.5 ms, a mean amplitude of 10.2 +/- 3.6 mV, and a mean nerve conduction velocity of 57 +/- 5 m/s. Subgroupings based on demographic characteristics, percentile distributions, side-to-side, and proximal-to-distal variations are presented.

Ulnar nerve F-wave latencies recorded from the abductor digiti minimi

This study was performed to create a large database of normal values for the ulnar F-wave study and to investigate the effect of various demographic factors on F-wave results. The study was designed to incorporate a standard distance measure and temperature control, which are lacking in some previous studies. One hundred ninety-three asymptomatic volunteers without risk factors for neuropathy were recruited and had ten F-waves performed on each arm. Data were collected for the shortest F-wave (Fmin), mean F-wave (Fmean), the number of F-waves present out of ten stimuli (Fpersist), and the range of latencies (Frange). An analysis of variance statistical procedure was applied, and the Fmin and Fmean were found to correlate with age, gender, and height, although the gender effect was relatively weak. For all subjects taken together, the mean Fmin was 26.5 +/- 2.5 ms. The Fmean was 27.7 +/- 2.5 ms, and the mean Frange was 2.6 +/- 1.2 ms. Ninety-seven percent of subjects had an Fpersist of five or more. Mean side-to-side difference for Fmin was 0.2 +/- 1.1 ms.

Ulnar nerve motor conduction to the abductor digiti minimi

Ulnar motor study to the abductor digiti minimi is commonly performed, but a more extensive database of normative values using modern electrodiagnostic and statistical techniques and temperature control is needed for this test. Demographic subgroups of age, gender, and height should be evaluated using a large subject population to determine whether separate normal ranges should be created for subsets of the general population. In this study, 248 volunteers were tested to measure ulnar motor latency, amplitude, area, duration, and nerve conduction velocity. Side-to-side and distal-to-proximal variability was analyzed. A repeated measures analysis of variance was performed with the waveform measures as the dependent variables and age, gender, and height as independent variables. None of the results were found to vary significantly (at the P < or = 0.01 level) with the subjects' physical characteristics, and thus, the data for all subjects were pooled to create a normative database. The normal range was derived as mean +/- 2 standard deviations and at the 97th (third) percentile of observed values. Mean latency was 3.0 +/- 0.3 ms, and amplitude was 11.6 +/- 2.1 mV. Mean nerve conduction velocity was 61 m/s across all segments tested. The upper limit of normal side-to-side variability (mean + 2 standard deviations) for latency was 0.6 ms; for amplitude, it was 3.6 mV. The upper limit of normal drop in conduction velocity across the elbow was 15 m/s (at the 97th percentile). Additional data are presented for all variables measured, as well as for side-to-side variability and distal-to-proximal change.

Tibial nerve conduction to the flexor digiti minimi brevis

This study was performed to create an improved database of normative data for tibial motor conduction to the flexor digiti minimi brevis. A total of 205 volunteers were tested to measure lateral tibial motor latency, amplitude, area, and duration. Side-to-side variability was analyzed. A repeated measures analysis of variance was performed with the waveform measures as the dependent variables and age, gender, height, and bimalleolar width as independent variables. An association was noted between increasing age and decreasing amplitude and area. The normal range was derived as mean +/- 2 SD and at the 97th (third) percentile of observed values. Mean onset latency was 6.4 ms (SD, 1.0). Mean amplitude varied by age and ranged from 4.7 mV to 7.8 mV (SD, 3.1-3.2). The upper limit of side-to-side latency variation was 1.8 ms (at mean + 2 SD) or 1.5 ms (at the 97th percentile). The upper limit of normal variation in amplitude from one side to the other was 4.6 mV (by mean + 2 SD) or 6.3 mV (at the 97th percentile). This corresponded to a 58% drop in amplitude. The upper limit of normal difference between the medial and lateral branches was an increase of 3.5 ms of the lateral over the medial latency or a medial latency that was within 0.3 ms of the lateral latency (or longer). The other measures are presented in the article.

Peroneal nerve motor conduction to the extensor digitorum brevis

Peroneal motor studies to the extensor digitorum brevis are commonly performed in electrodiagnosis. They have been investigated by many authors to derive the normal ranges for latency, amplitude, and nerve conduction velocity. Many of these studies, particularly the older ones, have methodological limitations, especially in light of modern technique and statistical applications. They often used small sample sizes. The objective of this study was to generate an expanded database of normative values for the peroneal nerve. In this study, 242 asymptomatic subjects without risk factors for neuropathy were tested, and their peroneal motor response was analyzed for latency, amplitude, area, duration, and nerve conduction velocity. Side-to-side and proximal-to-distal variation was recorded. Mean +/- 2 standard deviations (SD) and percentiles of normality are presented. Mean onset latency was 4.8 ms (SD, 0.8). Mean amplitude was 6.8 mV (SD, 2.5) and 5.1 mV (SD, 2.5) for the younger and older than 40-yr age groups, respectively. Mean nerve conduction velocity ranged from 44 to 49 m/s, depending on the demographic group (SD, 4-5). The upper limit of normal side-to-side latency variation was 1.4 ms (mean + 2 SD). The upper limit of normal drop in nerve conduction velocity from the low leg to the across knee segment was 10 m/s (mean - 2 SD) or 12% (97th percentile). The upper limit of normal amplitude difference from side to side was 61 % (at the 97th percentile), and the upper limit of normal drop in amplitude from below to above the fibular head stimulation was 25% (at the 97th percentile). The other measures are presented in the article.

Mixed nerve conduction studies of the median and ulnar nerves

The median mixed nerve conduction study, using an 8-cm technique across the wrist, has been described as a particularly sensitive test for carpal tunnel syndrome. This test is usually performed along with a similar ulnar study to detect relative slowing of one nerve v the other. Several authors have investigated the normal range in nerve conductions of this test. Most of these studies were performed using relatively small numbers of subjects, and some did not use standardized distance measurement and temperature control. They also did not measure all the waveform variables that are easily obtained with modern equipment. The purpose of this study was to create a large database of normal values for the median and ulnar studies. Two hundred forty-eight subjects were tested bilaterally. Data were collected for onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, rise time, duration, side-to-side variability, and between-nerve variability. Increasing age, body mass index, and male gender correlated with decreasing amplitude and area values. For both nerves, the mean onset latency was 1.6 +/- 0.2 ms, and the mean peak latency was 2.1 +/- 0.2 ms. For the median nerve, the mean onset-to-peak amplitude was 75 +/- 47 microV, and the mean peak-to-peak amplitude was 80 +/- 48 microV. For the ulnar nerve, the mean onset-to-peak amplitude was 27 +/- 17 microV, and the mean peak-to-peak amplitude was 29 +/- 22 microV. Mean side-to-side difference for the median and ulnar onset and peak latencies was 0.0 +/- 0.2 ms. The mean difference between onset and peak latencies between the nerves was 0.0 +/- 0.2 ms. The other results are presented in the article.

Peroneal nerve F-wave latencies recorded from the extensor digitorum brevis

This study was performed to create a large database of normal peroneal F-wave latencies. A total of 180 subjects were tested bilaterally and had their shortest (Fmin), mean (Fmean), and latency range (Frange) of F-waves recorded. The number of F-waves present out of ten stimuli (Fpersist) was also recorded. Demographic characteristics were noted and an analysis of variance was performed to determine whether any of these characteristics were associated with different results for the F-wave measures. Age and height, and, to a lesser extent, gender correlated with differences in Fmin, and Fmean, but not Frange. Race and body mass index (weight divided by height squared) were not associated with any differences in results. The mean Fmin was 50.2 +/- 5.5 ms. Mean Fmean was 52.0 +/- 5.6 ms and mean Frange was 4.9 +/- 2.3 ms. Median Fpersist was between 5 and 6. Mean side-to-side difference for Fmin was 0.7 +/- 2.4 ms. All other results are provided in the article. This article presents a database for normal values and the upper limits of normal for Fmin, Fmean, Frange, and side-to-side differences. A low Fpersist does not seem particularly clinically useful for the peroneal nerve, although a high Fpersist seems to be a sign of normality.

Normal range for H-reflex recording from the calf muscles

This study was performed to derive the normal range for H-reflex latency, recording from the calf, on a large and varied subject population. Two hundred fifty-one asymptomatic subjects without risk factors for neuropathy were tested bilaterally. The results were analyzed to determine whether various demographic characteristics were associated with different results. A repeated measures analysis of variance was performed with the latency as the dependent variable and age, race, gender, body mass index (kg/m2), and height as the independent variables. A significance value of P < or = 0.01 level was used. Side-to-side variability was also examined, and, for this measure, a repeated measurements analysis was not necessary because there was only one measurement per subject; a simple analysis of variance was used. Age and height were noted to be associated with different mean latencies; race, gender, and body mass index were not. The mean H-reflex latency was 30.3 +/- 2.4 ms, and the upper limits of normal (mean + 2 SD) for the various categories of age and height ranged from 30.0 to 38.2 ms. In addition, the upper limits of normal were derived as the 97th percentiles of observed latency values. For all subjects taken together, this value was 35.0 ms, and, for the various subgroups, it ranged from 29.7 to 36.4 ms. Mean side-to-side variability was 0.2 +/- 1.0 ms, with an upper limit of normal of 2.2 ms as the mean + 2 SD or 2.0 ms as the 97th percentile.

Tibial nerve motor conduction to the abductor hallucis

Tibial motor studies to the abductor hallucis are commonly performed in electrodiagnosis. Numerous authors have investigated this nerve to derive the normal ranges for latency, amplitude, and nerve conduction velocity (NCV). Many of the studies were performed without regard to temperature control, fixed distance measurement, and demographic characteristics such as age, gender, and height, which are known to affect nerve conduction studies. They often used small sample sizes, and some did not use true normal controls. This study was performed to create an expanded database of normative values for the tibial nerve. In this study, 250 asymptomatic subjects without risk factors for neuropathy were recruited and tested for their tibial motor response. Latency, amplitude, area, duration, and NCV were recorded. A repeated measures analysis of variance was performed with the waveform measures as the dependent variables and age, gender, and height as independent variables. Factors that were significant at the P < or = 0.01 level were used to create separate normative databases. Age was found to be associated with different results for amplitude, area, and NCV. Height was found to be associated with different results for NCV. Once these statistically significant factors were determined, Tukey-adjusted pair-wise comparisons of least squares means were used to collapse categories (by decade for age) that were not significantly different from each other at the P < or = 0.05 level. Side-to-side and proximal-to-distal differences were analyzed. The normal range was derived as mean +/- 2 standard deviations (SD) and at the 97th (third) percentiles of observed values. Mean onset latency was 4.5 ms (SD, 0.8). Mean amplitude was 15.3 mV (SD, 4.5), 12.9 mV (SD, 4.5), and 9.8 mV (SD, 4.2) for the respective age groups of 19-29, 30-59, and 60-79 yr. Nerve conduction velocity ranged from a mean of 44 to 51 m/s depending on the demographic groups of various ages and heights. The upper limit of side-to-side latency variation was 1.4 ms (at the 97th percentile), and the upper limit of normal amplitude difference from side to side was 50% (at the 97th percentile). The other measures are presented in the article.

Race effect on nerve conduction studies: a comparison between 50 blacks and 50 whites

OBJECTIVE

To determine whether there are any differences in nerve conduction study results between blacks and whites.

DESIGN

The following studies were performed: median, ulnar, peroneal, and tibial motor studies; median and ulnar mixed motor/sensory studies; sural and radial sensory studies; and H-reflex studies.

SETTING

Private office or university-based clinic.

PARTICIPANTS

Fifty adult blacks and 50 adult whites who met inclusion criteria, recruited through advertisements.

MAIN OUTCOME MEASURES

Differences between blacks and whites were compared to determine whether they exceeded a cutoff of 0.2 msec for latencies, 20% difference for amplitudes, 5 m/sec for conduction velocity, and 1.2 msec for H-reflex times. A repeated analysis of variance was performed to detect statistically significant differences (defined as p< or =.01).

RESULTS

Only values for the mean peroneal and tibial motor latencies exceeded the cutoff times. The mean peroneal response was faster by 0.3 msec and the mean tibial response was slower by 0.3 msec in blacks than whites. These differences were not statistically significant at a level of p< or =.01.

CONCLUSION

There is no significant difference between blacks and whites in normal nerve conduction study findings in healthy adults.

Martial arts

The martial arts have a reputation for being a high-risk activity, but are generally practiced in a safe environment. This article presents the results of a survey which is used to calculate risk of injury per 1000 hours of practice. The injury rate compares favorably with other mainstream activities; in fact, the martial arts are generally considered safer than most. The most common injuries occur to the wrist, hand, finger, foot, knee, head, and thigh. Special issues of importance for prevention and treatment of these injuries are discussed.

Body mass index effect on common nerve conduction study measurements

This study was performed to determine whether there is a difference in nerve conduction study (NCS) measures based on body fat (body mass index; BMI). Two hundred fifty-three subjects had the following NCS tests performed on them: median, ulnar, peroneal, and tibial motor studies; median, ulnar, radial, and sural sensory studies; median and ulnar mixed nerve studies; and H-reflex studies. BMI was calculated as weight (kg) divided by height (m) squared. A repeated measures analysis of variance was run adjusting for age, sex, and height and using BMI as both a continuous variable and by dividing BMI into upper, middle, and lower thirds. The sensory and mixed nerve amplitudes correlated significantly (P < or = 0.01) with BMI for all nerves tested, with means being approximately 20-40% lower in the obese than in the thin subjects. No correlation was noted between BMI and nerve conduction velocity, H-reflex latency, or most of the other motor/sensory/mixed measures. The correlation between increased BMI and lower sensory/mixed nerve amplitudes should be taken into account in clinical practice.