19 Del. Admin. Code § 1342-A-5.0

Current through Register Vol. 27, No. 12, June 1, 2024

Section 1342-A-5.0 - Follow-Up Diagnostic Testing Procedures

5.1 ELECTRODIAGNOSTIC (EDX) STUDIES are well established and widely accepted for evaluation of patients suspected of having CTS. The results are highly sensitive and specific for the diagnosis. Studies may confirm the diagnosis or direct the examiner to alternative disorders. Studies require clinical correlation due to the occurrence of false positive and false negative results. Symptoms of CTS may occur with normal EDX studies, especially early in the clinical course.

EDX findings in CTS reflect slowing of median motor and sensory conduction across the carpal tunnel region due to demyelination. Axonal loss, when present, is demonstrated by needle electromyography in median nerve-supplied thenar muscles. Findings include fibrillations, fasciculations, neurogenic recruitment and polyphasic units (reinnervation).

5.1.1 Needle electromyography of a sample of muscles innervated by the C5 to T1 spinal roots, including a thenar muscle innervated by the median nerve of the symptomatic limb, is frequently required.

5.1.2 The following EDX studies are not recommended to confirm a clinical diagnosis of CTS:

5.1.2.1 Low sensitivity and specificity compared to other EDX studies: multiple median F wave parameters, median motor nerve residual latency, and sympathetic skin response

5.1.2.2 Investigational studies: evaluation of the effect on median NCS of limb ischemia, dynamic hand exercises, and brief or sustained wrist positioning

5.1.3 To assure accurate testing, temperature should be maintained at 30-34C preferably recorded from the hand/digits. For temperature below 30C the hand should be warmed.

5.1.4 All studies must include normative values for their laboratories.

5.1.5 Positive Findings - Any of these nerve conduction study findings must be accompanied by median nerve symptoms to establish the diagnosis.

5.1.5.1 Slowing of median distal sensory and/or motor conduction through the carpal tunnel region

5.1.5.2 Electromyographic changes in the median thenar muscles in the absence of proximal abnormalities

5.1.6 Because laboratories establish their own norms, a degree of variability from the suggested guideline values is acceptable.

5.1.7 In all cases, normative values are to be provided with the neurodiagnostic evaluation.

5.1.8 Suggested grading scheme by electrodiagnostic criteria for writing a consultation or report may be:

5.1.8.1 Mild CTS-prolonged (relative or absolute) median sensory or mixed action potential distal latency (orthodromic, antidromic, or palmar).

5.1.8.2 Moderate CTS-abnormal median sensory latencies as above, and prolongation (relative or absolute) of median motor distal latency.

5.1.8.3 Severe CTS-prolonged median motor and sensory distal latencies, with either absent sensory or palmar potential, or low amplitude or absent thenar motor action potential. Needle examination reveals evidence of acute and chronic denervation with axonal loss.

5.1.9 Frequency of Studies/Maximum Number of Studies:

5.1.9.1 Indications for Initial Testing:

5.1.9.1.1 Patients who do not improve symptomatically or functionally with conservative measures for carpal tunnel syndrome over a 3-4 week period

5.1.9.1.2 Patients in whom the diagnosis is in question

5.1.9.1.3 Patients for whom surgery is contemplated

5.1.9.1.4 To rule out other nerve entrapments or a radiculopathy

5.1.9.2 Repeated studies may be performed:

5.1.9.2.1 To determine disease progression. 8-12 weeks is most useful when the initial studies were normal and CTS is still suspected

5.1.9.2.2 For inadequate improvement with non-surgical treatment for 8-12 weeks

5.1.9.2.3 For persistent or recurrent symptoms following carpal tunnel release, post-op 3-6 months, unless an earlier evaluation is required by the surgeon

5.2 IMAGING STUDIES

5.2.1 Radiographic Imaging: Not generally required for most CTS diagnoses. However, it may be necessary to rule out other pathology in the cervical spine, shoulder, elbow, wrist or hand. Wrist and elbow radiographs would detect degenerative joint disease, particularly scapholunate dissociation and thumb carpometacarpal abnormalities which occasionally occur with CTS.

5.2.2 Magnetic Resonance Imaging (MRI): Considered experimental and not recommended for diagnosis of Carpal Tunnel Syndrome. Trained neuroradiologists have not identified a single MRI parameter that is highly sensitive and specific. MRI is less accurate than standard electrodiagnostic testing, and its use as a diagnostic tool is not recommended.

5.2.3 Sonography: This tool has not been sufficiently studied to define its diagnostic performance relative to electrodiagnostic studies. It is not a widely applied test. Sonography may detect synovial thickening in CTS caused by rheumatoid arthritis. It may be useful if space-occupying lesions, such as, lipomas, hemangiomas, fibromas, and ganglion cysts, are suspected. Its routine use in CTS is not recommended.

5.3 ADJUNCTIVE TESTING Clinical indications for the use of tests and measurements are predicated on the history and systems review findings, signs observed on physical examination, and information derived from other sources and records. They are not designed to be the definitive indicator of dysfunction.

5.3.1 Electromyography: is a generally accepted, well-established procedure. It is indicated when acute and/or chronic neurogenic changes in the thenar eminence are associated with the conduction abnormalities discussed above.

5.3.2 Electroneurometer: May serve as a diagnostic tool as it helps to detect early distal sensorineural impairment.

5.3.3 Portable Automated Electrodiagnostic Device: Measures distal median nerve motor latency and F-wave latency at the wrist and has been tested in one research setting. It performed well in this setting following extensive calibration of the device. Motor nerve latency compared favorably with conventional electrodiagnostic testing, but F-wave latency added little to diagnostic accuracy. It remains an investigational instrument whose performance in a primary care setting is as yet not established, and is not recommended as a substitute for conventional electrodiagnostic testing in clinical decision-making.

5.3.4 Quantitative Sensory Testing (QST): May be used as a screening tool in clinical settings pre- and post-operatively. Results of tests and measurements of sensory integrity are integrated with the history and systems review findings and the results of other tests and measures. QST has been divided into two types of testing:

5.3.4.1 Threshold tests measure topognosis, the ability to exactly localize a cutaneous sensation, and pallesthesia, the ability to sense mechanical using vibration discrimination testing (quickly adapting fibers); Semmes-Wienstein monofilament testing (slowly adapting fibers);

5.3.4.2 Density Tests also measure topognosis and pallesthesia using static two-point discrimination (slowly adapting fibers); moving two-point discrimination (quickly adapting fibers).

5.3.5 Pinch and Grip Strength Measurements: May be accepted as a diagnostic tool for CTS. Strength is defined as the muscle force exerted by a muscle or group of muscles to overcome a resistance under a specific set of circumstances. Pain, the perception of pain secondary to abnormal sensory feedback, and/or the presence of abnormal sensory feedback affecting the sensation of the power used in grip/pinch may cause a decrease in the force. When all five handle settings of the dynamometer are used, a bell-shaped curve, reflecting maximum strength at the most comfortable handle setting, should be present. These measures provide a method for quantifying strength that can be used to follow a patient's progress and to assess response to therapy. In the absence of a bell-shaped curve, clinical reassessment is indicated.

5.3.6 Laboratory Tests In one study of carpal tunnel patients seen by specialists, 9% of patients were diagnosed with diabetes, 7% with hypothyroidism, and 15% with chronic inflammatory disease including spondyloarthropathy, arthritis, and systemic lupus erythematosis. Up to two thirds of the patients were not aware of their concurrent disease. Estimates of the prevalence of hypothyroidism in the general population vary widely, but data collected from the Colorado Thyroid Disease Prevalence Study revealed subclinical hypothyroidism in 8.5% of participants not taking thyroid medication. The prevalence of chronic joint symptoms in the Behavioral Risk Factor Surveillance System (BRFSS) from the Centers for Disease Control (CDC) was 12.3%. If after 2-3 weeks, the patient is not improving the physician should strongly consider the following laboratory studies: thyroid function studies, rheumatoid screens, chemical panels, and others, if clinically indicated.

Laboratory testing may be required periodically to monitor patients on chronic medications.

19 Del. Admin. Code § 1342-A-5.0