Multiple tests and diagnostic validity

Refining quality measures for electrodiagnostic testing in suspected carpal tunnel syndrome to account for acceptable variations in practice: Expert review process

INTRODUCTION/AIMS

Using a set of process-of-care quality measures for electrodiagnostic testing in suspected carpal tunnel syndrome (CTS), the research team previously documented large variations in electrodiagnostic testing practices and adherence to quality measures. This study sought to enhance the applicability and validity of the quality measures by integrating acceptable variations in testing practices.

METHODS

We recruited 13 expert electrodiagnostic medicine specialists from five specialty societies. The experts iteratively refined five quality measures, and then rated the validity of the refined quality measures (1-9 scale). During this process, the experts reviewed data on adherence to existing quality measures and variations in electrodiagnostic testing practices, and considered recently published quality measures from the American Association of Neuromuscular and Electrodiagnostic Medicine.

RESULTS

Three quality measures (electrodiagnostic testing before surgery for CTS, temperature assessment during electrodiagnostic testing, and electrodiagnostic criteria for severe median neuropathy) underwent few refinements and were rated valid (medians 8-9). Two measures (essential components of electrodiagnosis, criteria for interpreting electrodiagnostic tests as median neuropathy) were judged valid (medians 8) after revisions. For these measures, experts' ratings on the recommended components of sensory or mixed nerve conduction studies varied: agreement among the experts about the use of sensory peak latency was greater than for onset latency or sensory velocity.

DISCUSSION

This study produced quality measures that provide minimum standards for electrodiagnostic testing for suspected CTS that are more comprehensive and nuanced than prior versions. Future work can assess the feasibility, reliability, and validity of these refined measures in diverse physician practices.

Clinical and electrodiagnostic abnormalities of the median nerve in dental assistants

STUDY DESIGN

Descriptive.

OBJECTIVES

To determine the presence of clinical and electrodiagnostic abnormalities of the median and ulnar nerves in both upper extremities of dental assistants.

BACKGROUND

A high prevalence of median neuropathies at, or distal to, the wrist have been reported in dentists and dental hygienists. But there is a paucity of literature on the incidence of abnormalities of the median or ulnar nerves in dental assistants.

METHODS

Thirty-five United States Army dental assistants (24 female, 11 male; age range, 18-41 years) volunteered for the study. Subjects completed a standardized history and physical examination. Nerve conduction status of the median and ulnar nerves of both upper extremities was obtained by performing motor, sensory, and F-wave (central) nerve conduction studies.

RESULTS

All electrophysiological variables were normal for motor, sensory, and F-wave (central) values when compared to a chart of normal values. Based on comparison studies of median and ulnar motor latencies within the same hand, 9 subjects (26%) involving 14 hands (20%) were found to have electrodiagnostic abnormalities of the median nerve at, or distal to, the wrist. The other 26 dental assistants demonstrated normal comparison studies of the median and ulnar nerves in both upper extremities.

CONCLUSIONS

In this descriptive study of 35 dental assistants, 9 subjects (26%) were found to have electrodiagnostic abnormalities of the median nerve at, or distal to, the wrist (when compared to the ulnar nerve of the same hand). Ulnar nerve electrophysiological function was within normal limits for all subjects examined.

Median and ulnar neuropathies in university guitarists

STUDY DESIGN

Descriptive study.

OBJECTIVES

To determine the presence of median and ulnar neuropathies in both upper extremities of university guitarists.

BACKGROUND

Peripheral nerve entrapment syndromes of the upper extremities are well documented in musicians. Guitarists and plucked-string musicians are at risk for entrapment neuropathies in the upper extremities and are prone to mild neurologic deficits.

METHODS AND MEASURES

Twenty-four volunteer male and female guitarists (age range, 18-26 years) were recruited from the Belmont University School of Music and the Vanderbilt University Blair School of Music. Individuals were excluded if they were pregnant or had a history of recent upper extremity or neck injury. Subjects completed a history form, were interviewed, and underwent a physical examination. Nerve conduction status of the median and ulnar nerves of both upper extremities was obtained by performing motor, sensory, and F-wave (central) nerve conduction studies. Descriptive statistics of the nerve conduction study variables were computed using Microsoft Excel.

RESULTS

Six subjects had positive findings on provocative testing of the median and ulnar nerves. Otherwise, these guitarists had normal upper extremity neural and musculoskeletal function based on the history and physical examinations. When comparing the subjects' nerve conduction study values with a chart of normal nerve conduction studies values, 2 subjects had prolonged distal motor latencies (DMLs) of the left median nerve of 4.3 and 4.7 milliseconds (normal, < 4.2 milliseconds). Prolonged DMLs are compatible with median neuropathy at or distal to the wrist. Otherwise, all electrophysiological variables were within normal limits for motor, sensory, and F-wave (central) values. However, comparison studies of median and ulnar motor latencies in the same hand demonstrated prolonged differences of greater than 1.0 milliseconds that affected the median nerve in 2 additional subjects, and identified contralateral limb involvement in a subject with a prolonged distal latency. The other 20 subjects demonstrated normal comparison studies of the median and ulnar nerves in both upper extremities.

CONCLUSIONS

In this descriptive study of a population of 24 university guitarists, 4 musicians (17%) were found to have electrophysiologic evidence of median neuropathy at or distal to the wrist or carpal tunnel syndrome. Ulnar nerve electrophysiological function was within normal limits for all subjects examined.

Clinical and electrodiagnostic testing of carpal tunnel syndrome: a narrative review

Carpal Tunnel Syndrome (CTS) is a pressure-induced neuropathy that causes sensorimotor disturbances of the median nerve, which impair functional ability. A clear history that elicits relevant personal and work exposures and the nature of symptoms can lead to a high probability of a correct diagnosis. Hand diagrams and diagnostic questionnaires are available to provide structure to this process. A variety of provocative tests have been described and have variable accuracy. The Phalen's wrist flexion and the carpal compression tests have the highest overall accuracy, while Tinel's nerve percussion test is more specific to axonal damage that may occur as a result of moderate to severe CTS. Sensory evaluation of light touch, vibration, or current perception thresholds can detect early sensory changes, whereas 2-point discrimination changes and thenar atrophy indicate loss of nerve fibers occurring with more severe disease. Electrodiagnosis can encompass a variety of tests and is commonly used to assess the presence/severity of neuropathic changes and to preclude alternative diagnoses that overlap with CTS in presentation. The pathophysiologic changes occurring with different stages of nerve compression must be considered when interpreting diagnostic test results and predicting response to physical therapy management.

Motor and somatosensory evoked potentials in asymptomatic spondylotic cord compression

To assess whether electrophysiological tests are of use in differentiating between patients with asymptomatic cervical stenosis and patients with clinical evidence of myelopathy, we studied motor evoked potentials (MEPs) to magnetic brain stimulation and somatosensory evoked potentials (SEPs) in patients with asymptomatic cervical cord compression and compared the results to healthy age-matched controls. The MEPs were normal in 23 of 25 patients and SEPs in 22 of 23 patients. Thus, MEPs and SEPs are normal in most cases of asymptomatic cervical stenosis. As previous studies have shown MEPs, and to a lesser extent SEPs, to be sensitive in the detection of spondylotic myelopathy, our data indicate that MEP and SEP may be clinically useful for differentiating patients with cervical stenosis who have myelopathy from those who have not.