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Practice Parameter: Carpal Tunnel SyndromeComparison of Sensitivity of Different EDX StudiesBased on the data reviewed in the Results, median sensoryand motor nerve CV studies including comparison ofmedian sensory conduction to ulnar and radial sensoryconduction in the same hand are more sensitive and specificfor the diagnosis of CTS than measurements of (1) medianSNAP amplitudes and amplitude ratios, (2) motor CMAPamplitudes and amplitude ratios, (3) F-wave parameters, and(4) sympathetic skin responses.Several studies that met 4 or more of the 6 AAEM CTS LICcompared the relative sensitivity of different tests of mediansensory conduction, median motor conduction, and needleEMG in CTS patients.In 4 of 4 recent (after 1980) studies of patients with CTS,NCSs showed abnormalities more often than needle EMGof the APB muscle (Kimura and Ayyar, 131 Jackson andClifford, 110 Seror, 228 and Kuntzer. 140 )In 23 of 29 studies of CTS patients, median sensory NCSswere abnormal more frequently than motorNCSs. 31,47,57,91,110,125,128,131,135,140,159,167,171,174,188,189,200,206,214,220,221,226,228,233,237,249,253,254,255 The 2 studies published before1990 that were exceptions may reflect a small sample ofpatients (20 hands of 13 patients), 128 and a low threshold(3.7 ms) for an abnormal median motor distal latency, 110 (thelatter information was obtained by written communicationfrom the author and was not included in the original report).The 4 studies published since 1990 that were exceptionshave suggested that computation of the median terminallatency index (Simovic and Weinberg 237 ) and comparisonof the second lumbrical (median) and interossei (ulnar)distal motor latency difference has a test sensitivity equal orgreater than median sensory conduction (Preston andLogigian, 200 Sheean, 233 and Trojaborg 253 ). However, theselatter median/ulnar lumbrical/interossei test findings werenot confirmed in the study by Uncini 254 that met all 6AAEM CTS LIC.In 19 of 19 studies of patients with CTS, median mixedNCSs from the palm to the wrist (e.g., 8 cm conductiondistance) were abnormal more frequently than mediansensory NCSs from the digit to the wrist (e.g., 13 cm to 14cm conduction distance). 9,31,57,59,71,110,128,131,132,140,173,188,189,200,214,221,228,233,237 These 19 studies included the 7 reports thatmet 6 AAEM CTS LIC by Jackson and Clifford, 110Kimura, 132 Padua and colleagues, 188,189 Scelsa andcolleagues, 221 Di Guglielmo and colleagues, 59 andKuntzer 140 which are summarized in Tables 11 and 12.In 20 of 20 studies of patients with CTS, comparison ofmedian sensory/mixed nerve conduction to ulnarsensory/mixed nerve conduction or radial sensory nerveconduction in the same limb of CTS patients were abnormalmore frequently than evaluation of median sensory NCSsfrom wrist to digit alone. 9,38,45,47,57,63,110,116,140,143,148,171,173,174,188,189,192,228,237,248,254,255 These 20 studies included the 6reports that met 6 AAEM CTS LIC by Carroll, 38 Jacksonand Clifford, 110 Kuntzer, 140 Padua and colleagues, 188,189 andUncini and colleagues 254 which are summarized in Tables 9,17, 18, 19, and 20.The pooled sensitivity of the several tests evaluated isshown in Table 22 (data analysis by Gary Gronseth, MD).The data in the appropriate table for each study weresubjected to a meta-analysis with 95% confidence limits totake into account the fact that some of the studies includedmore CTS patients than other studies. CONCLUSIONSThis report provides convincing scientific evidence thatmedian sensory and motor NCSs:1. Are valid and reproducible clinical laboratorystudies.2. Confirm a clinical diagnosis of CTS with a highdegree of sensitivity (>85%) and specificity(>95%).The sensitivities of the several different median NCSs werecompared. The comparison demonstrated that:1. Median sensory NCSs confirm the clinicaldiagnosis of CTS more often than median motorNCSs (63% to 69% versus 65% to 85%: Tables3, 11, 12, 18, 19, 20, and 22).or2. The median sensory or mixed nerve conductionfrom wrist to digit (conduction distance 13 to 14cm) is less sensitive (65%: Tables 11and 22) forconfirmation of the clinical diagnosis of CTScompared to:a. Techniques which evaluate median sensoryor mixed nerve conduction over a short (7 to8 cm) conduction distance across the carpaltunnel (e.g., palmar studies 74%: Tables 12and 22); orb. Techniques which compare sensory ormixed nerve conduction of the median nervethrough the carpal tunnel to sensory ormixed nerve conduction of the ulnar nerve(85%: Tables 18, 19, and 22) or radial nerve(65%: Tables 20 and 22) in the same hand;c. Techniques which compare sensory or mixednerve conduction of the median nerve throughthe carpal tunnel to sensory or mixed NCSs ofproximal (forearm) and distal (digit) segmentsof the median nerve in the same limb (85%:Tables 16 and 22).S954 CTS Literature Review© 2002 American Association of Electrodiagnostic Medicine
Practice Parameter: Carpal Tunnel SyndromeTable 22. Comparison of Pooled Sensitivities and Specificitiesof EDX Techniques to Diagnose CTS.TechniquePooledSensitivity*A Median sensory and mixed nerve conduction: wrist and0.85†palm segment compared to forearm or digit segment(0.83,0.88)B Comparison of median and ulnar sensory conduction0.85Between wrist and ring finger(0.80,0.90)C Median sensory and mixed nerve conduction0.74†Between wrist and palm(0.71,0.76)D Comparison of median and ulnar mixed nerve0.71Conduction between wrist and palm(0.65,0.77)E Median motor nerve conduction0.69†Between wrist and palm(0.64,0.74)F Comparison of median and radial sensory conduction0.65Between wrist and thumb(0.60,0.71)G Median sensory nerve conduction0.65†Between wrist and digit(0.63,0.67)H Median motor nerve distal latency 0.63†(0.61,0.65)I Median motor nerve terminal latency index 0.62†(0.54,0.70)J Comparison of median motor nerve distal latency (second0.56‡lumbrical) to the ulnar motor nerve distal latency (second (0.46,0.66)interossei)K Sympathetic skin response 0.04PooledSpecificity*0.98†(0.94,1.00)0.97(0.91,0.99)0.97†(0.95,0.99)0.97(0.91,0.99)0.98†(0.93,0.99)0.99(0.96,1.00)0.98†(0.97,0.99)0.98†(0.96,0.99)0.94†(0.87,0.97)0.98‡(0.90,1.00)0.52(0.44,0.61)(0.00,0.08)* For each EDX technique to summarize results across studies, sensitivities were pooled from individual studies by calculating aweighted average. In calculating the weighted average, studies enrolling more patients received more weight than studies enrollingfewer patients. Specificities were similarly pooled by calculating the weighted average. The data in the parentheses below thesensitivity and specificity values represent the lower and upper 95% confidence limits of the weighted average, respectively. Dataanalysis courtesy of Dr. Gary Gronseth.† There was heterogeneity between some of the studies (the 95% confidence intervals of the sensitivities and specificities do notoverlap). This disparity may be related to differences in case definition of CTS, the use of different cut-points to define anabnormal value, and differences in the average severity of the CTS patients in the different studies.‡ Results based on a single study.RECOMMENDATIONS REGARDING EDXSTUDIES TO CONFIRM A CLINICALDIAGNOSIS OF CTSThe recommendations below are identical to those madeand endorsed in 1993 7 by the AAN, the AAPMR, and theAAEM with the clarification of recommendation 1 and 2aand the addition of 2c based on new evidence reviewed inthe second CTS Literature Review. 2 In patients suspectedof positive CTS, the following EDX studies arerecommended (see Table 22 for sensitivity and specificityof Techniques A – K):1. Median sensory NCS across the wrist with aconduction distance of 13 to 14 cm(Technique G). If the result is abnormal,comparison of the result of the mediansensory NCS to the result of a sensory NCSof 1 other adjacent sensory nerve in thesymptomatic limb (Standard).2. If the initial median sensory NCS across thewrist has a conduction distance greater than8 cm and the result is normal, 1 of thefollowing additional studies is recommended:a. Comparison of median sensory ormixed nerve conduction across the wristover a short (7 to 8 cm) conductiondistance (Technique C) with ulnarsensory nerve conduction across thewrist over the same short (7 to 8 cm)Muscle & Nerve Supplement X 2002 S955
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