A comparison of traditional electrodiagnostic studies, electroneurometry, and vibrometry in the diagnosis of carpal tunnel syndrome

Progress in vibrotactile threshold evaluation techniques: a review

Vibrotactile threshold (VT) testing has been used for nearly a century to investigate activation of human somatosensory pathways. This use of vibrotactile stimuli provides a versatile tool for detecting peripheral neuropathies, and has been broadly used for investigation of carpal tunnel syndrome. New applications include investigation of drug-induced neuropathies and diabetes-related neuropathies. As a feedback device, the vibrotactile stimuli could be used as an information delivery system for rehabilitative feedback devices for upper limb musculoskeletal disorders or as information channels for the visually impaired. This review provides a comprehensive review of the advancement in VT measurement techniques over time and a comparison of these techniques in terms of various hardware features used and the testing protocols implemented. The advantages and limitations of these methods have been discussed along with specific recommendations for their implementation and suggestions for incorporation into clinical practice.

Occupational changes in manual tactile sensibility of the dentist

The aim of this study was to find out if the use of vibrating tools (drill, ultrasonic scaler ...) in dental practice has negative side effects on the manual tactile sensibility of the dentist. The sensory tests were performed on 50 subjects, who were allocated to three different groups according to their occupation and the length of their working experience. The first test group consisted of 20 dentists, who had more than 25 years of work experience. As a control group, 20 non-dentists were recruited to obtain a similar age distribution as the former test group. A final group consisted of 10 dentists with more than 1 year of work experience. All subjects underwent three tests: light-touch sensation test, two-point discrimination test and thermal sensation test on the thumb and the index finger of the working and non-working hands. Results showed significant differences, especially for the light-touch sensation test. The study showed more specifically that the tactile sensibility of the working hand of the dentists with more than 25 years of work experience was significantly diminished with respect to the non-working hand and to the working hand of non-dentists. In the test group of young dentists, there was no noticeable reduction of manual tactile sensibility.

Diagnosis of carpal tunnel syndrome

This clinical practice guideline was created to improve patient care by outlining the appropriate information-gathering and decision-making processes involved in managing the diagnosis of carpal tunnel syndrome. The methods used to develop this clinical practice guideline were designed to combat bias, enhance transparency, and promote reproducibility. The guideline's recommendations are as follows: The physician should obtain an accurate patient history. The physician should perform a physical examination of the patient that may include personal characteristics as well as performing a sensory examination, manual muscle testing of the upper extremity, and provocative and/or discriminatory tests for alternative diagnoses. The physician may obtain electrodiagnostic tests to differentiate among diagnoses. This may be done in the presence of thenar atrophy and/or persistent numbness. The physician should obtain electrodiagnostic tests when clinical and/or provocative tests are positive and surgical management is being considered. If the physician orders electrodiagnostic tests, the testing protocol should follow the American Academy of Neurology/American Association of Neuromuscular and Electrodiagnostic Medicine/American Academy of Physical Medicine and Rehabilitation guidelines for diagnosis of carpal tunnel syndrome. In addition, the physician should not routinely evaluate patients suspected of having carpal tunnel syndrome with new technology, such as magnetic resonance imaging, computed tomography, and pressure-specified sensorimotor devices in the wrist and hand. This decision was based on an additional nonsystematic literature review following the face-to-face meeting of the work group.

Effects of bias on the results of diagnostic studies of carpal tunnel syndrome

PURPOSE

Design weaknesses in studies of diagnostic tests can lead to biases that produce misleading results. The extent to which such biases exist in studies of diagnostic tests for carpal tunnel syndrome (CTS) is unknown, and no studies address whether these biases influence published estimates of the performance of CTS diagnostic tests. The present study investigates these issues.

METHODS

We conducted a systematic review of studies of tests used to diagnose CTS in adults. Whether a study had design-related biases was determined using the Quality Assessment of Diagnostic Accuracy Studies instrument, by determining whether a study had a case control design, and by considering each study's level of evidence. We used meta-regression to determine whether any of these factors influenced estimates of the sensitivity, specificity, and diagnostic odds ratio of diagnostic tests.

RESULTS

A total of 23 studies of 129 diagnostic test evaluations met our inclusion criteria. Of those, 87% (20 of 23 studies) contained at least 1 bias and, on average, each study contained 2 biases. The most common design-related bias was spectrum bias (61% of studies [14 of 23 studies]), which was perfectly correlated with use of a case control design. Spectrum bias was associated with a statistically significant overestimation of sensitivity, specificity, and the diagnostic odds ratio. Test review bias (which was clearly present in 35% of studies [8 of 23 studies]) was associated with statistically significant overestimation of sensitivity and the diagnostic odds ratio. These results were not influenced by whether the diagnostic test under study was a clinical or an electrodiagnostic test.

CONCLUSIONS

Well-designed studies of diagnostics for CTS are uncommon, and shortcomings in the design of studies of clinical and electrodiagnostic tests are associated with overestimates of the performance of these tests. Consequently, most articles on diagnostic tests for CTS are unlikely to report results that are applicable to actual clinical practice.

The Hand-Arm Vibration International Consortium (HAVIC): Prospective Studies on the Relationship Between Power Tool Exposure and Health Effects

OBJECTIVES

The Hand-Arm Vibration International Consortium (HAVIC) is a collaboration of investigators from Europe and North America studying health effects from hand-arm vibration (HAV). Features include prospective design, cross-cohort exposure, and health assessment methods.

METHODS

Two new cohorts (dental hygienists and dental hygiene students), two existing cohorts (Finnish forest workers, and Swedish truck cab assemblers), and a previous population (US shipyard workers) are included. Instruments include surveys, quantitative medical tests, physical examination, and work simulation and data logging to assess exposure. New methods were developed for nerve conduction and data logging.

RESULTS

Findings on the relationship between nerve conduction and skin temperature in HAV-exposed subjects resulted in a new approach to subject warming.

CONCLUSIONS

Integrating established cohorts has advantages over de novo cohort construction. Complex laboratory tests can be successfully adapted for field use.

Nerve conduction and sensorineural function in dental hygienists using high frequency ultrasound handpieces

BACKGROUND

Oscillatory vibration from industrial power tools poses a well-recognized risk of peripheral nerve injury. There have been reports of elevated vibrotactile perception thresholds (VPT) among dentists, dental technicians, and dental hygienists, using rotary devices and ultrasonics. Elevated VPTs are an indicator of small fiber nerve or mechanoreceptor injury, but the high frequencies associated with dental instruments are presumed by the ISO to exceed physiological response upper thresholds. This study examines nerve conduction and sensorineural deficits in dental hygienists.

METHODS

A cross-sectional study of 94 experienced dental hygienists was conducted to assess peripheral nerve function and clinical signs and symptoms. Specialized testing included measurement of VPTs for three different categories of mechanoreceptors, sensory nerve conduction tests with fractionated digit and palmar segments, and measurement of calibrated pinch force with force sensitive resistors (FSRs) during a simulated procedure.

RESULTS

Chronic hand paresthesias were described by 44.7% of experienced dental hygienists. Sensory nerve conduction velocity (SNCV) across the wrist-palm segment of the median nerve. VPTs were particularly elevated at the FAII mechanoreceptor among experienced dental hygienists. Compared to participants without carpal tunnel syndrome (CTS), as defined by study criteria, 14 experienced hygienists with diagnosed CTS had almost twice the average weekly use of vibratory instruments -8.3 hr versus 4.5 hr, and had SNCV deficits along the digit -47.11 m/sec (+8.70) versus 42.57 m/sec (+8.25), and across the wrist -44.04 m/sec (+7.15) versus 41.36 m/sec (+9.27). There was a distinct subset of dental hygienists (27%) with a combination of low calibrated pinch force in simulations, subjective loss of strength and elevated VPTs, especially in the FAII mechanoreceptor population -110.82 db (+8.57) versus 104.84 db (+6.80) in the rest of the cohort. This subset also had a higher prevalence of paresthesias (67% vs. 39%) and greater cumulative vibration exposure (OR = 1.206 [CI 1.005-1.448]), than other hygienists.

CONCLUSIONS

The high levels of paresthesias observed among dental hygienists appear to be attributable to several pathophysiological mechanisms, including, sensory nerve demyelination at the carpal tunnel and intrinsic to the digits, and dysfunction of fingertip mechanoreceptors. A distinct sub-population appears to exhibit a high level of accumulated abnormality.

Potential occupational health problems for dentists in Flanders, Belgium

The aim of this study was to gather data on occupational health effects among Flemish dentists. A questionnaire on various potential health effects was sent out to randomly selected Flemish dentists. Pilot experimental studies were performed on hearing and sensory function of the fingers on small groups of dentists. Audiometric data of both ears, gathered with an interval of 10 years, were analysed. Sensory tests of the fingers were performed for dominant and non-dominant hands in relation to exposure time to (ultra)sonic equipment. Positive responses for the questionnaire were as follows: low back pain, 54% (stress-correlated); vision problems, 52.3% (age-correlated); infections, 9%; allergies, 22.5% (mainly latex); stress level was scored 7 on a scale from 0 to 10; diminished sensitivity of the fingertips, 6% and auditory disorders, 19.6%. Pilot audiometric data showed a hearing loss at 4,000 Hz for the left ear, presumably indicative of occupational noise trauma. The two-point discrimination ability of the dominant hand tended to diminish in line with the number of years of practice. Dentists in Flanders were found to suffer from various health-related problems. More elaborate studies are required to provide more details on the risks for occupational hearing impairment and vibration hand neuropathy and to determine whether the problems described were related to the practice of dentistry.

Accuracy of a portable electroneurometer for measuring distal motor latency

BACKGROUND

A facile electromyographic test in the outpatient clinic is needed to evaluate the outcome of screening for carpal tunnel syndrome. The purpose of the current prospective study was to compare the accuracy of Nervepace digital electroneurometer (Nervepace) and Dantec Neuromatic 2000M (Dantec) measurements of a wide range of distal motor latency (DML) of the median nerve.

METHODS

The DML values for 112 of 126 median nerves examined with Nervepace and conventional electromyography, Dantec were statistically analyzed in this prospective study. The 30 hands of 15 clinically healthy adults 20-24 years old served as the reference group. Sixty consecutive patients (96 hands) with idiopathic carpal tunnel syndrome provided a wider range of DML values. All of the patients had standard clinical tests and standard motor (Dantec and Nervepace) and sensory (Dantec) electrodiagostic tests before endoscopic carpal tunnel release.

RESULTS

The DML was measurable in all 30 hands of the reference group, in all 96 hands of the patients by Dantec, but in only 82 hands (52 patients) by Nervepace. Nervepace and Dantec DML values of 6.0 ms or less had high correlation and agreement.

CONCLUSIONS

Correlation and agreement decreased significantly among values greater than 6.0 ms.

Clinical diagnosis of carpal tunnel syndrome: a systematic review

The purposes of this systematic review were to examine the properties of clinical tests used in the diagnosis of carpal tunnel syndrome (CTS) and to provide estimates of their sensitivity and specificity. A literature search was conducted using two databases-PubMed and the Cumulative Index to Nursing and Allied Health Literature (CINAHL)-from 1986 to June 2003, and hand-searching reference lists of retrieved articles. Two reviewers evaluated the papers for quality using an evaluation tool developed by one of the authors. Estimates of sensitivity and specificity were determined by averaging values across studies weighted by sample size. Although 60 studies were reviewed in detail, many were of poor quality (mean quality score was 6.6 of 12, with only 15 of 60 obtaining a score of 8 or greater). The most frequently studied test was Phalen's, with an overall estimate of 68% sensitivity and 73% specificity. Next was Tinel's, with estimates of 50% and 77%, and then carpal compression, with estimates of 64% and 83% for sensitivity and specificity, respectively. Two-point discrimination and testing of atrophy or strength of the abductor pollicis brevis proved to be specific but not very sensitive. The estimates determined in this review should help therapists choose clinical tests with the appropriate balance of sensitivity and specificity required for diagnosing carpal tunnel syndrome in their specific clinical environments.

Literature review: nervepace digital electroneurometer in the diagnosis of carpal tunnel syndrome

Over the last two decades, several diagnostic devices have been developed to assess patients with suspected carpal tunnel syndrome (CTS). One such device is the Nervepace Digital Electroneurometer (NDE). At this time, however, the AAEM concludes that the current literature does not support the substitution of the NDE for standard electrodiagnostic studies in the clinical evaluation of patients with CTS.

Electrodiagnosis in carpal tunnel syndrome

There is currently no gold standard to definitively diagnose carpal tunnel syndrome. It remains a clinical diagnosis supported by characteristic electrodiagnostic abnormalities. Properly performed electrodiagnostic studies should provide the hand surgeon with information regarding severity, progression if a previous study was performed, and a reasonable assurance that concomitant peripheral nervous system abnormalities are not present. Hand surgeons do not need to discern nuances of an electrodiagnostic evaluation; however, the ability to identify state-of-the-art techniques coupled with a thoughtful interpretation by the electrodiagnostician will improve their confidence in using this important diagnostic tool to evaluate carpal tunnel syndrome.

Test of a new technique for the diagnosis of carpal tunnel syndrome

Several new techniques for carpal tunnel syndrome diagnosis have been developed in the last few years. This work tests a technique that compares the distal motor latency of the median nerve to the second lumbrical muscle (2L) with the distal motor latency of the ulnar nerve to the interossei muscle (INT). Results from 40 normal hands give the superior limit of the normal difference (2L-INT) as 0. 26 ms (&xmacr;+3 SD). In 55 hands with different levels of carpal tunnel syndrome, this new technique was more sensitive and accurate than the conventional test which uses the distal motor latency of the median nerve to the abductor pollicis brevis muscle (APB), especially in the less severe cases. With the absence of the compound muscle action potentials of the APB muscle caused by severe thenar atrophy, it is much easier to obtain the potential from the 2L muscle. We concluded that this is a sensitive, simple, rapid, and non-invasive new technique, and therefore, it should be incorporated as part of the routine ENMG procedures for carpal tunnel syndrome diagnosis.

The value of electrodiagnostic consultation for patients with upper extremity nerve complaints: a prospective comparison with the history and physical examination

OBJECTIVES

To determine whether electrodiagnostic testing changes diagnostic certainty compared with a detailed history and physical examination, and whether interactions between medical information, the extent of testing, and diagnostic certainty imply a need for advanced medical knowledge on the part of the tester.

DESIGN

Prospective observation.

SETTING

University orthopedic department and small community hospital electrodiagnostic laboratories.

PATIENTS

Two hundred fifty-five consecutive referrals for upper extremity nerve complaints.

OUTCOME MEASURES

Diagnosis, diagnostic confidence, and severity of neurologic lesion were coded after standardized history and physical and after electrodiagnostic testing.

RESULTS

Electrodiagnostic testing substantially altered 42% of diagnoses, confirmed 37%, and did not clarify 21%. The extent of testing correlated with the size of the differential diagnosis, the number of previous hospitalizations, and the number of other medical problems. Confidence in final diagnoses correlated positively with severity of the lesion, but negatively with the size of the differential diagnosis and the number of painful body areas. Hospitalizations and medical problems also tended towards negative correlations.

CONCLUSIONS

This study, in which all electrodiagnostics, histories, and physical examinations were performed by a single physician, suggests that electrodiagnosis substantially alters clinical impressions in a large percentage of patients. The complex relationship between clinical information, the extent of testing, and final diagnostic certainty suggests that specialized medical knowledge is required for accurate electrodiagnosis.