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We evaluated the natural history of median nerve sensory conduction, hand/wrist symptoms, and carpal tunnel syndrome (CTS) in an 11-year longitudinal study of 289 workers from four industries. Twenty hands which had carpal tunnel release surgery were excluded, leaving 558 hands for the primary study group. Overall, the trend was for mean sensory latencies and prevalence of slowing to increase, the prevalence of symptoms to decrease, and the prevalence of CTS to remain unchanged. Among individual hands, nerve conduction abnormalities tended to persist (82% 11-year persistence), while symptoms fluctuated widely (13% 11-year persistence). There was a strong, direct linear correlation between initial severity of slowing and subsequent development of CTS; however, most workers who developed de novo slowing did not develop symptoms or CTS. We conclude that changes in conduction status of the median nerve occur naturally with increasing age and do not necessarily lead to symptoms and CTS.

We investigated the effects of three legal drugs (tobacco, caffeine, and alcohol) on the prevalence of carpal tunnel syndrome (CTS) confirmed by nerve conduction studies (definite CTS) in two groups of American industrial workers: 656 nonclaimant workers and 808 working patients referred for upper extremity symptoms. Comparing workers with definite CTS to workers without definite CTS revealed 26% greater current use of tobacco, 19% greater lifetime use of tobacco, 5% greater current use of caffeine, 14% lesser current use of alcohol, and 75% greater history of alcohol abuse in the workers with definite CTS. All these differences were statistically significant. Those who currently used alcohol but not tobacco or caffeine were at the lowest risk for slowing, symptoms, and definite CTS. Those who currently used caffeine alone or in combination with tobacco were at the highest risk. In female workers, current smoking, current caffeine use, and current coffee consumption independently predicted 5.0% of the explainable risk for definite CTS. In male workers, history of alcohol abuse and current beer consumption independently predicted 3.0% of the explainable risk for definite CTS. Prevalence of slowing, symptoms, and definite CTS in 12 specific job categories correlated directly with current tobacco use. We conclude that the use of legal drugs affects the prevalence of median nerve slowing, symptoms, and carpal tunnel syndrome, but the effects of the drugs independently explain only a small portion of the total risk. Nevertheless, legal drug use or abuse may serve as a marker for increased CTS risk.

Cubital tunnel syndrome is the second most common entrapment neuropathy of the upper limb. This paper presents the experience of treating cubital tunnel syndrome with simple decompression in 131 patients (164 ulnar nerves) over the past 12 years. 85% of these patients had mild or moderate ulnar nerve disease. In 146/164 ulnar nerves (89%), simple decompression resulted in good or excellent immediate post-operative relief of symptoms. After an average follow-up of 4.3 years (range, 0.8–12.0 years), 130/164 (79%) still reported good or excellent relief. The independent predictors of a better long-term outcome were absence of post-operative subluxation, greater body weight, normal pre-operative two-point discrimination (2-PD), and a more recent date of operation. A physical therapy rehabilitation program generally began on the day after surgery. Active participation in this predicted a rapid return to work or activities of daily living. The average time to return to work with simple decompression was 20 workdays.

We compared the predictive values of three measurements of sensory conduction of the median nerve at the carpal tunnel (maximum latency difference [MLD], 8-cm latency [S8], and 14-cm latency [S14]) in 2334 hands of industrial workers, workers' compensation patients, and students. The MLD was determined by the centimetric technique. The MLD was the most sensitive and efficient measurement for predicting carpal tunnel syndrome (CTS). An MLD > or = 0.40 ms correctly identified 86.3% of 753 hands with CTS. The MLD correlated best with CTS and with the primary diagnostic category (CAT). MLD was the second factor selected in stepwise regression analysis for CAT (numbness was first and S8 was third). The MLD was the most important factor for predicting persistent or de novo CTS in a 5-year follow-up of 630 hands. Thus, the MLD was the most reliable nerve conduction study measurement for predicting current or future CTS in these subjects' hands.

As part of an ongoing study of carpal tunnel syndrome (CTS) in industry, we measured plasma concentrations of pyridoxal 5'-phosphate (PLP, a measure of vitamin B6 status) and total ascorbate (ASC, a measure of vitamin C status) in 441 adult volunteers from six industries and a university exercise study. In the entire study group and in non-vitamin users (n = 218), there were no significant differences in mean plasma PLP or ASC concentrations between controls (neither symptoms nor slowing), subjects with symptoms only, subjects with median nerve slowing only, or subjects with CTS (symptoms + slowing). In male non-vitamin users (n = 137), there were significant inverse univariate associations between plasma PLP concentration and the prevalence of pain, the frequency of tingling and nocturnal awakening, and the Phalen test result. In this same subgroup, the ASC/PLP ratio was directly associated with the prevalence of pain and nocturnal awakening, and with the frequency of pain, tingling, and nocturnal awakening. In multivariate analyses, plasma ASC concentration predicted more median nerve slowing and confirmed CTS, and vitamin or vitamin interaction variables were independent predictors of 20 CTS-related outcomes. These multivariate relationships often occurred only after adjustment for age, gender, body mass index, serum alkaline phosphatase activity, or tobacco use. We conclude that there are significant relationships between plasma vitamin levels and both components of CTS (specific symptoms and median nerve slowing). The interaction between plasma PLP and ASC appears to be particularly important with respect to symptoms.

As part of a continuing study of the causes of carpal tunnel syndrome (CTS) in industry, we measured sensory conduction of the median nerve in 101 Japanese furniture factory workers. We used the maximum latency difference (MLD) with a critical value of ≥0.40 msec to indicate abnormal slowing of nerve conduction. The prevalence of slowing in the Japanese workers was 17.8%, while the prevalence of probable CTS (based on symptoms only) was 2.5%, and the prevalence of definite CTS (probable CTS confirmed by slowing) was 2.0%. The most important factor predicting the MLD was the body mass index. The MLD was the most important factor predicting probable CTS. The prevalence of slowing in the Japanese workers was not significantly different from the prevalence of slowing in 316 American workers from four industries (22.0%), but the prevalences of probable CTS and definite CTS were much lower in the Japanese. The meaning of these findings is discussed.

One goal of surgery for carpal tunnel syndrome is to return the patient to work or full-time activities in the shortest possible period of time. The authors evaluated the effectiveness of two incisions, a short incision less than 2.5 cm and an incision greater than 2.5 cm, both combined with a program of active postoperative hand therapy in a group of 216 patients (293 releases). When compared to other techniques with or without active physical therapy, our combined program achieved as short a median return-to-work interval as any other method, both for workers' compensation patients (21 days) and for private/Medicare/welfare patients (10 days). The operating time averaged 7 minutes, and postoperative complications were few. The findings suggest that early hand therapy is more important than the short incision for minimizing the interval for regaining normal function and for decreasing the time-loss cost.

Anterior transposition and/or medial epicondylectomy are often considered procedures of choice for ulnar neuropathy at the elbow. Much experience suggests simple decompression to be a comparably effective alternative which involves less trauma, morbidity, and rehabilitation time. The post-operative clinical and electrophysiological results of 52 cases of simple decompression (41 patients) are summarized. Excellent or good clinical results were found in 75% of the nerves. Mean ulnar motor conduction velocities were significantly improved post-operatively, although nerve conduction parameters did not consistently correlate with clinical outcome. The average return-to-work time was 5.1 weeks. The advantages of simple decompression make it the procedure of choice for most cases of ulnar neuropathy.

1. Braun RM, Jackson WJ. Electrical studies as a prognostic factor in the surgical treatment of carpal tunnel syndrome. J Hand Surg 1994;19A:893-900. 2. Nathan PA, Meadows KD, Keniston RC. Rehabilitation of carpal tunnel surgery patients using a short surgical incision and an early program of physical therapy. J Hand Surg 1993;18A:1044-1050. 3. Nathan PA, Keniston RC, Meadows KD, Lockwood RS. Predictive value of nerve conduction measurements at the carpal tunnel. Muscle Nerve 1993; 16:1377-1382.

To the Editor. —We read with interest the communication by Rempel et al.1We have been studying the cause of CTS in industrial workers for 8 years and have found no consistent objective evidence that occupation is a major contributing factor to conduction abnormalities of the median nerve.2,3Rather, we have found the major risk factors for abnormal nerve conduction to be individual characteristics (obesity, age, wrist dimensions, and lack of exercise). In turn, abnormal nerve conduction is by far the most important factor predicting clinical CTS after 5 years.3 We agree with Rempel et al1that it is desirable to reduce the incidence of clinical CTS in industrial workers. What we disagree with is how the reduced incidence is to be achieved. Most of the major risk factors for CTS are also major risk factors for other serious illnesses, such as cardiovascular disease, neuropsychiatric problems

Fetal lung maturity was correlated to the results of amniotic fluid analysis in 578 samples obtained over a 2½ interval. Lecithin/sphingomyelin (L/S) ratios obtained by planimetric and densitometric methods were compared to the rapid surfactant test (RST). Both the planimetric L/S ratio (P L/S) and the densitometric L/S ratio (D L/S) correlated positively in a highly significant fashion with the RST. Both RST and D L/S were reliable in predicting fetal lung maturity (99 and 100 per cent, respectively). The RST was the most reliable test for fetal lung immaturity (69 per cent). Therefore, this series indicates than the RST could be used as a primary method with the D L/S being useful as an additional indicator of fetal maturity when the RST was intermediate, or the sample contaminated with blood and/or meconium.

To the Editor.— In her commentary on cholesterol screening, Ms Merz 1 discusses the need for lipoprotein analysis, in addition to total cholesterol measurements. As a military pathologist, I have been involved with autopsies on four middle-aged men who have died of acute myocardial infarction while exercising. None of these men has had a total cholesterol level greater than 6.21 mmol/L by the Lipid Research Clinics method, 2 although the two with high-density lipoprotein cholesterol (HDL-C) values both had cholesterol/HDL-C ratios greater than 4.00, including the one with a total cholesterol level greater than 5.17 mmol/L. Since most patients who die of cardiovascular disease at this medical center also do not have elevated total cholesterol levels, I began to question the reliability of isolated total cholesterol measurements. First, I looked at 1-month mortality in patients with cardiovascular disease who survived to admission and who had total cholesterol levels measured. Only