Louisiana Administrative Code › Title 40 - LABOR AND EMPLOYMENT › Part I - Workers' Compensation Administration › Subpart 2 - Medical Guidelines › Chapter 22 - Neurological and Neuromuscular Disorder Medical Treatment Guidelines › Subchapter A - Carpal Tunnel Syndrome (CTS) Medical Treatment Guidelines › Section I-2209 - Follow-Up Diagnostic Testing Procedures

Current through Register Vol. 50, No. 6, June 20, 2024
A. 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).
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.
2. The
					 following EDX studies are not recommended to confirm a clinical diagnosis of
					 CTS:
a. Low sensitivity and specificity
					 compared to other EDX studies: multiple median F wave parameters, median motor
					 nerve residual latency, and sympathetic skin response
b. Investigational studies: evaluation of the
					 effect on median NCS of limb ischemia, dynamic hand exercises, and brief or
					 sustained wrist positioning
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.
4. All studies must include normative values
					 for their laboratories.
5. Positive
					 Findings Any of these nerve conduction study findings must be accompanied by
					 median nerve symptoms to establish the diagnosis.
a. Slowing of median distal sensory and/or
					 motor conduction through the carpal tunnel region
b. Electromyographic changes in the median
					 thenar muscles in the absence of proximal abnormalities
c. Suggested guidelines for the upper limits
					 of normal latencies:
i. Median distal motor
					 latency (DML)-4.5msec/8cm
ii.
					 Median distal sensory peak latency (DSL)-3.6msec/14cm
iii. Median intrapalmar peak latency
					 (palm-wrist)-2.2msec/8cm
iv.
					 Median-ulnar palmar sensory latency difference greater than 0.3msec
6. Because laboratories
					 establish their own norms, a degree of variability from the suggested guideline
					 values is acceptable.
7. In all
					 cases, normative values are to be provided with the neurodiagnostic
					 evaluation.
8. Suggested grading
					 scheme by electrodiagnostic criteria for writing a consultation or report may
					 be:
a. Mild CTS-prolonged (relative or
					 absolute) median sensory or mixed action potential distal latency (orthodromic,
					 antidromic, or palmar).
b. Moderate
					 CTS-abnormal median sensory latencies as above, and prolongation (relative or
					 absolute) of median motor distal latency.
c. Severe CTS-prolonged median motor and
					 sensory distal latencies, with either absent or 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.
9. Frequency of Studies/Maximum
					 Number of Studies:
a. Indications for Initial
					 Testing
i. patients who do not improve
					 symptomatically or functionally with conservative measures for carpal tunnel
					 syndrome over a three to four week period;
ii. patients in whom the diagnosis is in
					 question;
iii. patients for whom
					 surgery is contemplated;
iv. to
					 rule out other nerve entrapments or a radiculopathy.
b. repeated studies may be performed:
i. to determine disease progression. 8-12
					 weeks is most useful when the initial studies were normal and CTS is still
					 suspected.
ii. for inadequate
					 improvement with non-surgical treatment for 8-12 weeks ;
iii. for persistent or recurrent symptoms
					 following carpal tunnel release, post-op three to six months, unless an earlier
					 evaluation is required by the surgeon.