Practice Parameter and Literature Review of the Usefulness of ...

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Practice Parameter: Carpal Tunnel Syndromeplaced slightly lateral to the midpoint of the thirdmetacarpal) with stimulation at the wrist for both the medianand ulnar nerves. The median nerve CMAP is recordedfrom the second lumbrical and the ulnar nerve CMAP isrecorded from the dorsal interosseus deep to the secondlumbrical in the palm with the same set of recordingelectrodes. 200 In contrast to the TTLD methodologydescribed above, both CMAPs have an initial negativedeflection.In a study that met all 6 AAEM CTS LIC, Uncini 254demonstrated that the LILD identified a small number ofadditional CTS patients with normal median motor distallatency values (Table 9). Because Uncini 254 did notsimultaneously evaluate median mixed nerve palmarconduction studies in CTS patients, his results are notinconsistent with the results of Sander 220 which showed themedian mixed nerve palmar conduction studies to be moresensitive than the THLD and TTLD studies to identify CTSpatients.There were 4 studies of the LILD in CTS that met 4 or 5 ofthe 6 AAEM CTS LIC with the following incidence ofabnormal LILD measurements in CTS: Sheean andcolleagues 233 (1995), 73%; Trojaborg 253 (1996), 84%;Preston and Logigian 200 (1992), 95%; and Resende 207(2000), 100%. Sheean and colleagues 233 noted that thecomputation of the LILD was identical in sensitivity tocomputation of the difference in median and ulnar mixednerve palmar CV to confirm the diagnosis of CTS; in 48 of66 hands with suspected CTS, 48 (72%) showedabnormalities with each test and there was a closecorrelation between the 2 tests.Median F-Wave Latency Studies. Table 10 presents theresults of a study of 7 different F-wave parameters in CTS.The study by Kuntzer 140 met 6 AAEM CTS LIC anddemonstrated that none of the F-wave parameters achievedthe specificity and sensitivity for the diagnosis of CTS ofdirect measurements of distal median motor conductionacross the carpal tunnel segment of the median nerve.Sander and colleagues, 220 in a study that met 5 of the 6AAEM CTS LIC, evaluated the calculated difference(FWLD: F-wave latency difference) between the minimummedian F-wave latency recorded from the APB and theminimum ulnar F-wave latency recorded from the ADM toidentify CTS patients. In the Sander and colleagues 220 study,the sensitivity of the FWLD to identify CTS was less than(1) comparison of median and ulnar distal motor latenciesacross the carpal tunnel and (2) comparison of median andulnar mixed nerve latencies across the carpal tunnel.Macleod, 157 in a study that met 4 of the 6 AAEM CTS LIC,noted that there was a high percentage of repeater F wavesin CTS, which are identical recurring F waves with the samelatency, configuration, and amplitude. However,abnormalities of median F-wave parameters can be causedby pathology not only in the carpal tunnel segment of theTable 9. Comparison of the Median Motor NerveDistal Latency (2nd Lumbrical) to the Ulnar MotorNerve Distal Latency (Interossei) in CTS.Author Uncini and colleagues 254Year 1993Number of Normal Hands(subjects)72 (47)Normal Subject’s Age: Mean(range)45 (18 to 78)Number of CTS Hands(patients)95 (70)CTS Subject’s Age: Mean(range)49 (26 to 78)Technique: ConductionDistanceAnatomical landmarksStimulation Site (median)Stimulation Site (ulnar)Recording SiteWrist creaseWrist creasePalm*Minimum Hand Temperature 32°CDifference Median-UlnarOnset Latency ± SDCriteria for Abnormal ValueAbnormal Value Difference inMedian and Ulnar LatencySpecificity of Abnormal Value0.10 ± 0.19 msMean + 2 SD>0.5 ms97.5% (estimate)Sensitivity of Abnormal Value 10% (56%)†* Lateral to midpoint 3rd metacarpal bone† In the Uncini and colleagues paper, 254 comparison of median motorconduction (lumbrical) and ulnar motor conduction (interossei) wasdone only in the CTS patients with (1) normal median sensoryconduction from D2 to wrist (SCV >45 ms) and (2) normal medianmotor conduction from wrist to APB (MDL
Practice Parameter: Carpal Tunnel Syndromemedian nerve, but also by pathology along the length of themedian motor nerve fibers to the APB from the spinal cordto the wrist. For all these reasons, measurements of F-wavelatencies and other F-wave parameters are notrecommended for the diagnosis of CTS.Buschbacher, 35 in a study that met 5 of the 6 AAEM LIC,reported the results of F-wave parameter in 195 referencesubjects. Fisher 73 (1997) used CTS as a model for analyzingthe effects of focal nerve injury on F-wave parameters.Median Sensory NCSsMedian Sensory Nerve Conduction from Digit to Wrist.Table 11 presents the results of 6 studies of median sensoryNCSs of a 13 to 14 cm length of the median nerve with theproximal portion passing through the carpal tunnel (digitwriststudies). These 6 studies that met all 6 AAEM CTSLIC determined that between 40% and 74% of patients withCTS demonstrate either a prolonged median sensory peaklatency or the median SNAP was absent. In a 1972 studythat met the 6 AAEM CTS LIC, Casey and LeQuesne 39reported a 94% incidence of abnormal median digit-wristsensory conduction: 15 out of 16 CTS patient studiesabnormal with 9 out of 16 absent SNAP and 6 out of 16reduced CV.There are 4 studies listed in Table 1 that provide mediansensory nerve conduction data in normal subjects whichsupport the choice of abnormal values in the 6 studies inTable 11 for median sensory peak latency, median sensoryonset latency, and median sensory CV (calculated from theonset latency and conduction distance). 34,58,110,242There were 19 other median sensory NCSs of the peaklatency, onset latency, and CV with conduction between thewrist and a digit (conduction distance of 13 to 14 cm) thatmet 4 or 5 of the AAEM CTS LIC with the followingincidence of abnormal findings (absent response, prolongedpeak or onset latency, or reduced CV) in patients with CTS:Andary and colleagues 9 (1996), 27%; Kothari andcolleagues 135 (1995), D2 42% and D3 54%; White andcolleagues 264 (1988), 44%, if a response could be elicited;Rosen 214 (1993), 48%; Mills 171 (1985), 53%; Sheean andcolleagues 233 (1995), 55%; Stevens 243 (1987), 64%; Seror 228(1994), peak latency 61%, CV 66%; Preston andLogigian 200 (1992), 67%; Felsenthal 71 (1979), 70%;Trojaborg 253 (1996), D2 70% and D3 72%; Gunnarsson 91(1997), 77%; Melvin and colleagues 167 (1973), 79%;Marinacci 159 (1964), 83%; Monga and colleagues 174 (1985),86%; Kimura and Ayyar 131 (1985), 92%; Kemble 125 (1968),93%; Plaja 199 (1971), 98%; Merchut and colleagues 168(1990), 100%.While most authors used the index finger (Digit 2 or D2) forstimulation or recording, some prefer to use the middlefinger (Digit 3 or D3) instead of the index finger to evaluatemedian sensory conduction in CTS. 31,117,118,173,181,192,271 Thestudies that evaluated median digit-wrist sensory conductionwith several digits noted abnormalities in CTS patients moreoften with evaluation of the middle finger compared to theindex finger, and evaluation of the thumb and sometimes thering finger studies were more often abnormal than both theindex and middle finger studies. 135,188,189,253There are 2 studies of median sensory conduction from digitto wrist in normal subjects that met 5 of the 6 AAEM CTSLIC: Stetson 242 (1994) D2 onset latency (3.0 ± 0.2 ms) andD2 sensory CV (SCV) (60.2 ± 4.9 m/s); Buschbacher 36onset (D2 = 2.6 ± 0.3 ms, D3 = 2.7 ± 0.3 ms) and peak (D2and D3 = 3.4 ± 0.3 ms) latencies, the Buschbacher 36 datapresents mean + 2 SD values higher than most of thereference values in the 7 studies in Table 11.Median Sensory Conduction from the Palm to the Wrist.Table 12 presents the results of 7 studies of median sensoryand/or mixed NCSs of an 8-cm length of the median nervepassing through the carpal tunnel. These 7 studies that metall 6 AAEM CTS LIC determined that between 67% and84% of patients with CTS demonstrate a prolonged medianpeak latency, onset latency, or CV with a conductiondistance of 8 cm.In Table 1, there are 4 studies of median sensory and/ormixed nerve conduction between the wrist and palm innormal subjects. Using a technique to study the conductionof the wrist-palm median nerve segment similar toKimura, 130 Di Benedetto and colleagues 58 reported adifference in peak latency in healthy subjects of less than 2.2ms, and a difference in onset latency in healthy subjects ofless than 1.8 ms, the latter value almost identical to thefinding of Kimura 130 in Table 12. Cruz Martinez andcolleagues 50 calculated the CV in palm-to-wrist segments ofthe median nerve from the onset latency in 47 normalsubjects, aged 21 to 77 Under the age of 50, the mediansensory CV was 55 ± 5 m/s, and over the age of 50, themedian sensory CV was 51 ± 5 m/s. Stetson 242 in a study of105 normal subjects noted an onset latency of 1.8 ± 0.2 ms.Buschbacher 33 in a study of 248 normal subjects reported anonset latency of 1.6 ± 0.2 ms and a peak latency of 2.1 ± 0.2ms.There were 15 additional studies that report median mixednerve conduction over a 7 cm to 8 cm distance across thecarpal tunnel that met 4 or 5 of the 6 AAEM CTS LIC withthe following incidence of abnormal findings in patientswith CTS: Kimura 121 (1978), 45%; Andary and colleagues 9(1996), 57%; White and colleagues 264 (1988), 65%, a studythat ignored cases with absent responses; Mills 171 (1985),67%; Robinson and colleagues 211 (1998) 70%; Sheean andcolleagues 233 (1995), 73%; Seror 228 (1994), 76%; Prestonand Logigian 200 (1992), 82%; Stevens 243 (1987), 87%;Monga and colleagues 174 (1985), 88%; Felsenthal andSpindler 71 (1979), 100%; Wongsam 271 (1983), 100%;Muscle & Nerve Supplement X 2002 S939
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