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Screening for the onset of carpal tunnel syndrome (CTS), which is associated with excess ergonomic stresses of the wrist and hand, is a major concern in occupational medicine. CTS questionnaires, physical examinations, and quantitative sensory function determination through neuroselective current perception threshold (CPT) measurements were obtained from the median digital nerves of 16 assembly line workers who were symptomatic with hand pain. Median nerve evaluations by CPT detected sensory abnormalities in 75% of the workers, and abnormalities in 50% of the workers were detected by clinical evaluations (p less than .05, df = 22). CPT abnormalities were characterized as "hypoesthetic" in 25% and hyperesthesic in 42% of the workers. The noninvasive, nonaversive CPT technique provided sensitive and easily obtained quantitative measures. Regular use of this procedure in the occupational setting may assist in preventing the development of advanced CTS for it provides early detection of median nerve abnormalities.

OBJECTIVE To evaluate the effects of different frequencies of auricular (ear-to-ear) sine-wave transcutaneous electrical nerve stimulation (TENS), administered at subliminal intensity, on trigeminal nerve sensitivity. DESIGN In a double-blind protocol, healthy volunteer subjects were administered one of three different frequencies of active TENS (5, 100, or 2,000 Hz) or placebo TENS (no current was passed) for 30 min. SETTING Department of Psychology, City University of New York. SUBJECTS 72 healthy undergraduate volunteers with no preexisting pain problems (16 men and 56 women), from the Department of Psychology, City University of New York. OUTCOME MEASURE Pretreatment to posttreatment changes were measured in sensation threshold for a 250-Hz electrical stimulus applied transcutaneously to an area 1 cm anterior to the tragus of the ear (mandibular division of the trigeminal nerve). RESULTS Analysis of variance indicated no group differences in baseline trigeminal sensation threshold, but there were significant group differences in pretreatment to posttreatment changes in sensation threshold (p < 0.001). A postiori analysis showed significant increases in trigeminal sensation threshold after active TENS as compared to placebo TENS (p < 0.05), with 5- and 100-Hz TENS producing significantly greater hypesthesia than 2,000-Hz TENS (p < 0.05). CONCLUSIONS Sine-wave auricular TENS produces frequency-dependent trigeminal hypesthesia that is not a placebo effect.

Some effects of sub-threshold sine-wave transcutaneous electrical nerve stimulation (TENS), passed between earlobe electrodes at a constant alternating current (AC) frequency of 100 Hertz (Hz), were investigated in 90 normal subjects after 30 minutes of treatment, and after 3 minutes of standardized mental stress (mental arithmetic) which immediately followed the 30 minute treatment. In a double-blind protocol, five groups received 1) active TENS during treatment and active TENS during stress; 2) active TENS during treatment and placebo TENS during stress; 3) placebo TENS during treatment and placebo TENS during stress; 4) placebo TENS during treatment and active TENS during stress; and 5) no treatment during both treatment and stress. Results showed significant reductions in systolic blood pressure, pulse rate and anxiety, but not in diastolic blood pressure or peripheral vascular tension, after 30 minutes of active TENS as compared to no treatment. No placebo TENS effect was observed. No significant differences were observed between active TENS; placebo TENS and no treatment in physiological or psychological response to the stress procedure. Results are discussed in terms of the applicability of this technique to the management of stress.

Normal peripheral nerve conduction is a marker of adequate dialytic therapy in the ESRD population. Decreasing nerve function detected by periodic testing indicates insufficient dialysis. The standard test for the quantitative evaluation of nerve integrity is the nerve conduction test (NCT). A study of 34 dialysis patients proves that the measurement of current perception threshold (CPT) is equally effective to NCT in defining peripheral nerve function (r = 0.81; p less than 0.001). The superiority of the CPT examination is discussed.

Peripheral and central nervous system effects of the cranial application of sub-threshold transcutaneous electrical nerve stimulation (TENS), of sinusoid waveform passed between earlobe electrodes at an AC frequency of 100 Hertz, were investigated. In a single-blind study, each of thirty healthy volunteer subjects was administered one 30 minute treatment of either active TENS, placebo TENS or no treatment. Pretreatment to post-treatment changes in measures of autonomic activity (blood pressure, pulse rate, peripheral vasomotor activity), somatic activity (skeletal muscle tension), and anxiety were evaluated. Significant reductions in systolic blood pressure (p less than .05), diastolic blood pressure (p less than .01), pulse rate (p less than .05), peripheral vasomotor activity (marginally significant: p less than .07) and anxiety (p less than .05) were observed subsequent to active. TENS as compared to both placebo TENS and no TENS. No significant placebo TENS effect was observed. Possible mechanisms of action of this form of cranial TENS on the peripheral and central nervous system are discussed.

Neuro-selective current perception threshold (CPT) values quantify peripheral nerve (n) integrity and provide an index of adequate hemodialysis (HD). Evaluation of polyneuropathy (PN) by CPT correlates with nerve conduction testing (NCT). CPT is convenient, painless, and may be performed during HD. Early detection of carpal tunnel syndrome (CTS), a complication of uremia, permits curative intervention. Utility of CPT and NCT measurements in detecting CTS in 29 stable HD patients were evaluated. Reproducibility of seven CPT determinations over 4 weeks was determined in each of 9 HD patients. The coefficient of variation for repeated 2000 Hz CPT measures was 6%. PN was detected by CPT in 92% of the patients and by NCT in 79% (r = 0.79, p less than 0.001). In 38% of the hands there was a CPT impairment in both the median and ulnar nerves (n), of which 25% were symptomatic for CTS. CPTs consistent with CTS (sufficiently greater impairment of the median vs ulnar n) were observed in 31% of the hands with combined median and ulnar n CPT abnormalities, and 11% were identified with CTS by NCT. The unique ability of the CPT exam to quantify hyperesthesia may account for its superior CTS detection sensitivity. These findings demonstrate that repeated CPT determinations are consistent and are diagnostic for CTS.

The effects of transcutaneous electrical nerve stimulation (TNS) of a constant alternating current administered at various frequencies and waveforms to volunteer human subjects were investigated. The TNS was found to evoke noncutaneous subjective sensations in all the subjects. Only with a sinusoid waveform of TNS were distinct frequency ranges of the stimulation associated with specific noncutaneous subjective sensations. Our findings suggest that nervous tissue is capable of discriminating the waveform parameters of an electrical stimulus.

Detailed clinical neurological examinations were conducted on 44 nondiabetic volunteers and 59 diabetic subjects. The examinations focused particularly on sensory symptomatic and physical evaluation. Standardized assessment of symptoms and physical testing of light touch, pain, vibratory, and thermal sensation was performed at the hand, wrist, elbow, foot, ankle, and knee. A total symptom score and physical score were defined by summing test scores at each site. Current perception threshold (CPT) testing that used constant sine-wave-alternating current was conducted at the same anatomic sites. CPT correlations with the physical score gave r values of .55 for 5 Hz, .60 for 250 Hz, and .62 for 2000 Hz (n = 618). Correlations with the symptom score were not as strong: r = .45 for 5 Hz, .46 for 250 Hz, and .51 for 2000 Hz. The correlation with symptom score was due primarily to a strong relationship for the symptom of numbness (r = .53 for all 3 frequencies). Correlations with pain and paresthesia were much lower. CPTs for diabetic subjects at the three frequencies were higher at most locations than for the nondiabetic volunteers. However, CPTs were no different from normal values in diabetic subjects without evidence of neuropathy. CPT testing appears to be a useful technique for assessment of diabetic sensory neuropathy.

Central stimulant actions of 10 methylxanthines in mice correlate with affinities for adenosine receptors labeled with N6-[3H]cyclohexyladenosine. Affinities of methylxanthines for adenosine receptors are consonant with central levels attained at behaviorally effective doses. The much higher concentrations of methylxanthines required to influence benzodiazepine receptor binding do not correlate with behavioral potency. N6-(L-Phenylisopropyl)adenosine (L-PIA), a metabolically stable analog of adenosine with high affinity for adenosine receptors, is an extremely potent behavioral depressant, reducing locomotor activity of mice at doses as little as 0.05 mumol/kg. The D isomer, which has much less affinity for adenosine receptors, is much less active as a central depressant. Theophylline stimulates locomotor activity and reverses depressant effects of L-PIA. Caffeine or 1,7-dimethylxanthine, when administered alone, elicits biphasic effects, with locomotor depression at lower doses and stimulation at higher doses. When administered with L-PIA, even low doses of caffeine produce marked stimulation. 3-Isobutyl-1-methylxanthine given alone elicits only behavioral depression. However, like theophylline and caffeine, isobutylmethylxanthine reverses the L-PIA-evoked depression, converting it into pronounced locomotor stimulation. The data strongly suggest that the behavioral stimulant effects of methylxanthines involve a blockade of central adenosine receptors.

[ 3 H ]-N 6 - cyclohexyladenosine and [3H]-1,3-diethyl-8-phenylxanthine label the A1 subtype of adenosine receptor in brain membranes. The affinities of methylxanthines in competing for A1 adenosine receptors parallel their potencies as locomotor stimulants. The adenosine agonist N6-(-phenylisopropyl) adenosine is a potent locomotor depressant. Both diazepam and N 6 -( l - phenylisopropyl ) adenosine cause locomotor stimulation in a narrow range of subdepressant doses. Combined stimulant doses of the two agents depress motor activity, as do larger doses of either one, given separately. Evidence supporting and against the hypothesis that some of the actions of benzodiazepines are mediated via the adenosine system is reviewed. A number of compounds interact with both systems, probably because of physico-chemical similarities between adenosine and diazepam. It is concluded that of the four classic actions of benzodiazepines, the sedative and muscle relaxant (but not anxiolytic or anticonvulsant) actions could possibly be mediated by adenosine.