Vitamin B6, vitamin C, and carpal tunnel syndrome.
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Ascorbic Acid Deficiency↗
Biomedical subjects
R A Werner
Publications and source records attributed to R A Werner.
Fire and insects in northern and boreal forest ecosystems of North America.
Fire and insects are natural disturbance agents in many forest ecosystems, often interacting to affect succession, nutrient cycling, and forest species composition. We review literature pertaining to effects of fire-insect interactions on ecological succession, use of prescribed fire for insect pest control, and effects of fire on insect diversity from northern and boreal forests in North America. Fire suppression policies implemented in the early 1900s have resulted in profound changes in forest species composition and structure. Associated with these changes was an increased vulnerability of forest stands to damage during outbreaks of defoliating insects. Information about the roles that both fire and insects play in many northern forests is needed to increase our understanding of the ecology of these systems and to develop sound management policies.
Journal Article↗
The effect of gabapentin on neuropathic pain.
OBJECTIVE: To evaluate the effects of gabapentin on pain scores and opiate use. DESIGN: Retrospective review of patients charts who received gabapentin for at least 30 days. Data were collected concerning patients' diagnosis, current drug use, concurrent drug use, gabapentin dose, pain scores, and patient-reported side effects. Patients were divided into three groups based on their pain diagnosis; low back, neuropathic, and myofascial pain. The neuropathic group was subdivided into postherpetic neuralgia, diabetic neuropathy, sympathetically maintained pain, and phantom pain. SETTING: Two tertiary referral teaching hospitals in southeastern Michigan. RESULTS: A total of 122 charts were reviewed and included in this study. A significant decrease in pain scores with gabapentin was seen in the neuropathic pain group (paired t-test, p < .0001) but not in the low back pain group. Of the neuropathic pain group, patients with postherpetic neuralgia had the greatest decrease in pain scores. Ten patients showed a > 75% decrease in pain scores, of these: nine had a direct nerve injury, and one had postherpetic neuralgia. Opiate use was unchanged in all groups. Patients who were taking opiates had significantly less benefit with gabapentin use in terms of pain score. Patient-reported side effects were similar to those reported in a nonchronic pain population. CONCLUSION: Gabapentin may be a useful adjunct for treating neuropathic pain with a minimum of side effects. Particular advantage may be gained with the use of this drug for postherpetic neuralgia and direct peripheral nerve injuries.
Acetates↗
Use of screening nerve conduction studies for predicting future carpal tunnel syndrome.
OBJECTIVE: To determine if an abnormal sensory nerve conduction study consistent with median mononeuropathy in asymptomatic workers was predictive of future complaints of the hand or finger suggestive of carpal tunnel syndrome. METHODS: This was a case-control study of over 700 active workers at five different work sites: four sites involved manufacturing workers and one site represented clerical workers. Patients' reports of symptoms of pain, numbness, tingling, or burning in the hand or finger that lasted more than one week or occurred three or more times after the initial screening were investigated. 77 cases were defined as asymptomatic workers with electrodiagnostic findings of median mononeuropathy in either hand based on a comparison of median and ulnar sensory evoked peak latencies. A difference > or = 0.5 ms was defined as abnormal; a normal difference was < or = 0.2 ms. Controls were asymptomatic age, and sex matched workers with normal nerve conduction studies in both hands. Follow up questionnaires were completed 17 (SD 6) months later. RESULTS: The follow up participation rate was 72%. Cases had a 12% risk of developing symptoms during the follow up period compared with 10% in the control group, chi 2 = 0.12, P = 0.73. CONCLUSIONS: Abnormal median sensory nerve conduction studies in asymptomatic workers were not predictive of future hand or fingers complaints and if used for preplacement screening among active workers this should be done with caution.
Adolescent↗
Influence of body mass index and work activity on the prevalence of median mononeuropathy at the wrist.
OBJECTIVE: To determine which proposed risk factor, work activity (industrial v clerical), body mass index (BMI), or other demographic factors had the most influence on the prevalence of median mononeuropathy at the wrist, and if there was an interaction between the risk factors. METHODS: This was a cross sectional study of active workers at five different worksites; four were industrial sites and one was clerical. 527 workers were recruited--164 clerical and 363 industrial. The presence of a median mononeuropathy in either hand was measured by electrodiagnostic techniques comparing median and ulnar sensory latencies. RESULTS: 30% of workers had an abnormality of the median sensory nerve at the wrist (34% of the industrial v 21% of the clerical workers). The adjusted risk for industrial workers was twice that of clerical workers. Obese workers (BMI > 29) were four times more likely to present with a median mononeuropathy than workers who were normal or slender (BMI < 25). There was no significant interaction between BMI and worksite in relation to median mononeuropathy. Increasing age was also related to an increased risk of median mononeuropathy. CONCLUSIONS: Obesity, industrial work, and age are independent risk factors that influence the prevalence of median mononeuropathies among active workers.
Adolescent↗
Test-retest reliability of an upper-extremity discomfort questionnaire in an industrial population.
OBJECTIVES: Efforts to understand or to monitor upper-extremity musculoskeletal disorders among workers have usually involved the use of questionnaires. The goal of this study was to assess the test-retest reliability of an upper-extremity discomfort questionnaire among industrial workers. METHODS: Test-retest agreement among 148 workers was analyzed using the kappa coefficient for categorical outcomes. Values of kappa greater than 0.75 are considered excellent, values between 0.40 and 0.75 are fair to good, and values of less than 0.40 represent poor agreement beyond chance alone. Test-retest results of continuous measures (eg, visual analogue scale responses) were compared with paired t-tests. RESULTS: The test-retest reliability of the questionnaire used to elicit demographic information, medical history, exercise participation, and information on musculoskeletal symptoms among industrial workers appears to be good to excellent in most instances. CONCLUSIONS: These results suggest that most results of this discomfort questionnaire are reliable and suitable for use in epidemiologic studies. For reassurance of the robustness of these findings, similar studies should be carried out in other worker populations with this, and other, questionnaire instruments.
Adult↗
Hand dominance effect on median and ulnar sensory evoked amplitude and latency in asymptomatic workers.
OBJECTIVE: To examine the relative effect of hand dominance on the median and ulnar sensory evoked responses and grip strength in active workers. DESIGN: A cross-sectional or survey design. SETTING: Workers from 4 different sites underwent on-site testing of the median and ulnar sensory nerves in both hands (antidromic stimulation, 14 cm), and testing of bilateral grip strength. PATIENTS: 224 workers, asymptomatic of hand, wrist, or finger pain, numbness, or tingling: 87% were right handed. MAIN OUTCOME MEASURES: Amplitude and latency of the median and ulnar sensory response and the grip strength of each hand. RESULTS: The amplitude of the median sensory response in the dominant hand was significantly lower in right handed individuals (34.6 microm V versus 38.8 microm V) but not in left handed workers (34.2 microm V versus 34.3 microm V). A similar relationship held for the ulnar evoked responses and the grip strength. Median and ulnar sensory latencies in right handed individuals did not differ side to side, whereas left handed workers had a slightly shorter latency on the left. CONCLUSIONS: The left hand of a right handed worker may not be exposed to as much trauma, resulting in relative protection of the nerves in the hand and a higher amplitude of the left median and ulnar evoked response. Left handed individuals may be more likely to use both hands equally and thus expose the nerves in each hand to an equal amount of trauma, resulting in their sensory amplitudes being equivalent (and also equal to the dominant hand of a right handed individual).
Adult↗
The relationship of vitamin B6 status to median nerve function and carpal tunnel syndrome among active industrial workers.
Case reports and small case series suggest that vitamin B6 deficiency is an important etiologic factor in carpal tunnel syndrome (CTS). This hypothesis has never examined in a randomly selected study population, particularly among active workers. We examined 125 randomly selected active workers from two industrial plants. Each worker completed a self-administered symptom questionnaire and underwent electrodiagnostic testing of the median and ulnar sensory nerves. Laboratory biochemical analyses of vitamin B6 status were also performed using the erythrocyte glutamic pyruvic transaminase assay, and quantification of plasma pyridoxal-5'-phosphate. Measurements of vitamin B6 status were unrelated to self-reported symptoms potentially consistent with CTS, electrophysiologically determined median or ulnar nerve function, and CTS defined on the basis of self-reported symptoms and electrophysiologic measurements. These results suggest that CTS among active industrial workers is unrelated to vitamin B6 status. Furthermore, in our opinion, empiric prescription of vitamin B6 to patients with CTS is unwarranted and potentially hazardous.
Adult↗
Relation between needle electromyography and nerve conduction studies in patients with carpal tunnel syndrome.
Four hundred eighty cases of electrodiagnostically confirmed carpal tunnel syndrome were reviewed to determine if the findings on nerve conduction studies could predict the presence or absence of fibrillation potentials or motor unit changes on the needle examination of the abductor pollicis brevis (APB). The needle examination is more uncomfortable and the ability to predict the findings in this setting from standard nerve conduction studies (NCS) would make the test more acceptable to patients. All patients had median and ulnar nerves (both sensory and motor) tested, as well as the needle evaluation of the APB. Two hundred thirty-one patients had an abnormal needle evaluation as defined by presence of one of the following conditions: abnormal spontaneous activity, increased motor unit action potential (MUAP) amplitude, or increased MUAP polyphasia. One hundred five patients had fibrillation potentials. The mean median motor and sensory amplitudes and latencies, as well as age, did differ in the normal and abnormal needle examination groups, but the sensitivity for predicting an abnormality ranged from 57% to 68%. The ratio of the median to the ulnar amplitudes did not improve the sensitivity of predicting the abnormal needle findings. Motor and sensory evoked potential latencies were the most important predictors of an abnormal needle examination.
Adolescent↗
The relationship between body mass index and the diagnosis of carpal tunnel syndrome.
Increased weight and, more recently, body mass index (BMI), have been suggested as risk factors for carpal tunnel syndrome (CTS). In an effort to determine the relative risk (RR) of obesity in the development of CTS, 949 patients who had an evaluation of the right upper extremity that included motor and sensory conduction studies of the median and ulnar nerves were reviewed. Of these patients, 261 were diagnosed with a median mononeuropathy at the wrist. Those individuals who were classified as obese (BMI > 29) were 2.5 times more likely than slender individuals (BMI < 20) to be diagnosed with CTS. Forty-three percent of obese women and 32% of obese men had the diagnosis of CTS compared to 21% of slender women and 0% of slender men.
Adult↗
Quantitative vibrometry and electrophysiological assessment in screening for carpal tunnel syndrome among industrial workers: a comparison.
Vibrometry has been demonstrated to be an effective adjunct to electrophysiological evaluation of nerve integrity in diffuse peripheral neuropathies but there is controversy over its value in the diagnosis of isolated compression neuropathy such as carpal tunnel syndrome (CTS). One hundred thirty factory workers were screened for peripheral nerve impairment using both vibrometry and electrophysiologic testing of digits 2 and 5 in both hands. Vibrometry had a low sensitivity in identifying individuals with symptoms of CTS or a median mononeuropathy defined by nerve conduction studies (NCS). The correlation of vibratory and the sensory evoked latencies were modest in the median nerve distribution (r = 0.297 to 0.370, p = 0.001). Using a comparison between vibration thresholds from digit 2 to 5 was not helpful in identifying cases of CTS and the difference in thresholds did not correlate with the difference in sensory evoked latencies. CTS is primarily a demyelinating process and can be easily detected with NCS. Because vibration threshold sensation is related to axonal loss it is not as sensitive in early CTS. Our results do not support the use of quantitative vibrometry as a screening tool median nerve impairment among industrial workers.
Adult↗
Evaluation of current perception threshold testing as a screening procedure for carpal tunnel syndrome among industrial workers.
Eighty-four workers participated in a work-site screening program designed, in part, to estimate the prevalence of carpal tunnel syndrome (CTS). Each worker completed a discomfort survey, limited electrodiagnostic testing of the median and ulnar sensory nerves in each wrist, and current perception threshold (CPT) testing in the right 2nd digit using the NEUROMETER CPT device. A subset of study participants also completed CPT testing in digit 5 on the right (n = 33). Comparisons were made among the CPT results, symptoms consistent with CTS, and electrophysiologic findings. The CPT results correlated poorly with electrophysiologic parameters from the same nerve distribution, and CPT results were statistically unrelated to self-reported symptoms that may be suggestive of CTS. The test performance characteristics of CPT testing (sensitivity, specificity, positive predictive value, and negative predictive value) were low in comparison with electrodiagnostic measurements and self-reported symptoms consistent with CTS. The electrophysiologic results were significantly associated with the constellation of symptoms that are consistent with CTS. On the basis of these results, CPT testing cannot be recommended as a screening procedure for identification of possible cases of CTS among active industrial workers.
Adult↗
Reverse Phalen's maneuver as an aid in diagnosing carpal tunnel syndrome.
A reverse Phalen's maneuver involves wrist and finger extension held for 1 minute. We showed that this maneuver results in a significantly higher intracarpal canal hydrostatic pressure as compared to a traditional Phalen's or a modified Phalen's maneuver. Additionally, 31 individuals with complaints of carpal tunnel syndrome symptoms and 20 normal controls were evaluated to see what effect the reverse Phalen's maneuver would have on median sensory latency and amplitude. Both groups demonstrated a prolongation of the median sensory revoked response after 1 minute of this maneuver. The control group had a prolongation of 0.05 ms compared to 0.13 ms in the carpal tunnel syndrome group. The difference between the two groups was significant at a p = 0.05 level. This may add to the sensitivity of conventional screening methods.
Adult↗
Effects of permethrin on aquatic organisms in a freshwater stream in south-central Alaska.
Permethrin (0.5%) was applied to individual Lutz spruce, Picea x lutzii Little, to protect them from attack by spruce beetles, Dendroctonus rufipennis (Kirby). Residue levels were monitored in a freshwater stream above, adjacent to, and below the treatment site at intervals before, during, and after treatment. Maximum residue levels in the stream within the treatment site ranged from 0.05 +/- 0.01 ppb 5 h after treatment to 0.14 +/- 0.03 ppb 8-11 h after treatment, with a decrease to 0.02 +/- 0.01 ppb 14 h after treatment. Levels of permethrin in standing pools near the stream within the treatment site were 0.01 +/- 0.01 ppb. Numbers of drifting aquatic invertebrates increased 2-fold during treatment and 4-fold 3 h after treatment and declined to before spray numbers within 9 h. Terrestrial insects did not appear to respond to treatments because none was found in stream drift samples. Trout fry (Dolly Varden), aquatic insect larvae, and periphyton (attached algae) within and below the treatment site during and after treatment did not show signs of mortality compared with an upstream untreated control site.
Alaska↗
Osteoarthritis of the hand and wrist in the post poliomyelitis population.
People with a chronic motor disability of the legs become increasingly more dependent upon their upper limbs for mobility and self-care skills as they age. Many of them complain of hand and wrist pain. A cross-sectional study of 61 post-poliomyelitis survivors was done to determine the prevalence of osteoarthritis within this population and to determine any inherent risk factors. Each subject underwent a radiographic evaluation of both hands and wrist as well as a detailed physical examination. A questionnaire was used to ascertain a history of hand activity, use of canes/crutches, walkers and wheelchairs. The mean age of the population sample was 49 +/- 6 with a mean duration of disability of 35 +/- 4 years. The prevalence of moderate or severe osteoarthritis of either the hand or wrist was 13% whereas the prevalence was 68% when cases with mild arthritic changes were also included. The risk factors associated with hand and wrist osteoarthritis in this population included age, lower limb weakness, use of an assistive devices, and severity of disability.
Activities of Daily Living↗
Multimodality evoked potential testing in acute mild closed head injury.
Multimodality evoked potential (MEP) testing, including brainstem auditory, visual, and somatosensory evoked potentials, have been reported to be useful in predicting outcome in severe closed head injury. Brainstem auditory evoked potentials have been demonstrated to be abnormal in 10% to 40% of acute mild head injury. A prospective study of 18 patients with mild closed head injury was undertaken to determine the usefulness of MEP screening within two weeks of the acute event. Long latency event-related potentials (P300s), in response to auditory stimuli with an oddball paradigm, were included in the screening. The subjects had several symptoms consistent with the postconcussive syndrome at the time of the evoked potential testing. Only one patient had an abnormal evoked potential response (greater than three standard deviations from the mean) from all the testing done. The standard methods of MEP testing were insensitive to quantifying the possible physiologic changes that are associated with memory deficits, lethargy, and emotional irritability after mild closed head injury.
Adolescent↗
Peripheral neuropathy associated with the hypereosinophilic syndrome.
This case report documents the natural history of the peripheral polyneuropathy associated with persistent hypereosinophilia after treatment with corticosteroids. The neuropathy was documented by nerve conduction studies which revealed reduced amplitude of the sensory and motor evoked responses and slowed conduction velocities that were consistent with axon loss. Sural nerve biopsy revealed mild axonal loss distally without eosinophilic infiltration. The patient was treated with high-dose corticosteroids with a rapid normalization of his eosinophil count. Neurologic examination six months later revealed a slight improvement in his motor strength and reflexes but no change in sensory functions. Follow-up electromyographic evaluation demonstrated an average 89% improvement in evoked potential amplitudes and a slight improvement in distal latencies and conduction velocities. These findings suggest that the neuropathy associated with hypereosinophilia is axonal in nature and that there is a temporal relationship between reduction in the absolute eosinophil count and the improvement of the neuropathy.
Electromyography↗
Bilateral phrenic nerve palsy associated with open-heart surgery.
The incidence of phrenic nerve palsy after open-heart surgery has been estimated at 10%, but it is usually unilateral and does not cause symptoms. Bilateral phrenic nerve injury after coronary artery bypass surgery is a rare complication. This case report describes a patient who developed bilateral phrenic nerve palsies and required prolonged ventilatory support. Denervation of both hemidiaphragms was documented by needle electromyography four weeks after bypass surgery. The patient required total ventilatory support for three months and partial ventilatory support for an additional three months. This case demonstrates the usefulness of electromyographic screening for documentation and prognostication after phrenic nerve injury. The cause of the lesion was unclear, but hypothermia and stretch were leading hypotheses. This patient developed the phrenic nerve palsies despite using a cardiac insulation pad.
Aged↗