Lumbrical-interosseous latency comparison in the diagnosis of carpal tunnel syndrome

Normal reference value of orthodromic and antidromic sensory nerve conduction velocity of median nerve with intact palmaris longus tendon in apparently healthy individuals

OBJECTIVES

The aim of this study was to determine normative electrophysiological reference values of median sensory nerve conduction studies among security guards with the palmaris longus tendon (PLT).

METHODS

Sensory nerve conduction studies of the median nerve using antidromic and orthodromic methods were conducted in the upper limbs of 101 healthy male security guards between the ages of 21 and 42 years. The presence of the PLT was recorded in both hands using a standard test. A scatter plot was used to determine the correlation between different parameters using the ortho and antidromic methods.

RESULTS

The mean age (years), weight (kg), height (cm), and BMI (kg/m2) were 28.77 ± 5.14, 70.53 ± 11.28, 171.71 ± 7.12, and 23.91 ± 3.45, respectively. In the median nerve (sensory) by antidromic method, the mean distal latency (DL) was 2.65 ± 0.33 ms and 2.64 ± 0.37, SNCV (sensory nerve conduction velocity) was 53.45 ± 5.28 m/s and 53.84 ± 5.68 and the amplitude was 27.33 ± 12.38 µV and 29.41 ± 12.97 in the left- and right-hand wrist, respectively. By orthodromic method the DL was 2.54 ± 0.53 ms and 2.51 ± 0.44, SNCV was 55.93 ± 6.09 m/s and 55.93 ± 5.24 and the sensory nerve action potential amplitude was 12.00 ± 8.82 µV and 11.72 ± 6.24 in the left and right hand, respectively. Spearman correlations were used to determine the variables influenced by hand sidedness.

CONCLUSIONS

The normative reference parameters of sensory nerve conduction velocity of the median nerve were established by both methods using a standardized technique.

Rapid Screening for Carpal Tunnel Syndrome: A Novel Method and Comparison With Established Others

PURPOSE

The authors have observed that in healthy people, the Ulnar wrist-to-first dorsal interosseous distal motor latency does not differ significantly compared with median wrist-to-abductor pollicis brevis distal motor latency. The aim of our study was to investigate whether the difference between these two latencies can be used as a screening tool for diagnosing carpal tunnel syndrome and how this technique compares with other established techniques.

METHODS

The study was set up as a prospective observational study. As gold standard for the clinical diagnosis of carpal tunnel syndrome, the authors used the opinion of two neurologists who independently examined the patients. A third neurologist, also independently, performed the electrophysiological study.

RESULTS

Eighty-four subjects, 42 patients and 42 age- and sex-matched controls, participated in the study. Among all subjects using a receiver operating characteristic curve analysis, the area under the curve was 0.924 (95% CI, 0.857-0.991; SE, 0.034; P < 0.001). To detect carpal tunnel syndrome, at a cutoff score of equal to or greater than 0.575 milliseconds, our technique showed a sensitivity of 91%, a specificity of 93%, a positive predictive value of 93%, and a negative predictive value of 91%. Compared with other "classical" techniques, our technique showed better area under the receiver operating characteristic curve and better Youden index.

CONCLUSIONS

The median wrist-to-abductor pollicis brevis motor latency minus ulnar wrist-to-first dorsal interosseous motor latency may be used as a novel rapid screening tool of patients suffering from carpal tunnel syndrome.

Diagnostic Value of the Second Lumbrical-Interosseous Distal Motor Latency Comparison Test in Severe Carpal Tunnel Syndrome

Objective

To examine the usefulness of the second lumbrical-interosseous (2L-INT) distal motor latency (DML) comparison test in localizing median neuropathy to the wrist in patients with absent median sensory and motor response in routine nerve conduction studies.

Methods

Electrodiagnostic results from 1,705 hands of patients with carpal tunnel syndrome (CTS) symptoms were reviewed retrospectively. All subjects were evaluated using routine nerve conduction studies: median sensory conduction recorded from digits 1 to 4, motor conduction from the abductor pollicis brevis muscle, and the 2L-INT DML comparison test.

Results

Four hundred and one hands from a total of 1,705 were classified as having severe CTS. Among the severe CTS group, 56 hands (14.0%) showed absent median sensory and motor response in a routine nerve conduction study, and, of those hands, 42 (75.0%) showed an abnormal 2L-INT response.

Conclusion

The 2L-INT DML comparison test proved to be a valuable electrodiagnostic technique in localizing median mononeuropathy at the wrist, even in the most severe CTS patients.

Diagnosis of Severe Carpal Tunnel Syndrome Using Nerve Conduction Study and Ultrasonography

This study investigated the correlation between nerve conduction study and ultrasonographic findings for assessment of the usefulness of ultrasonography in determining carpal tunnel syndrome severity. Hands of adults with carpal tunnel syndrome were assessed using ultrasound and nerve conduction studies and grouped according to median nerve cross-sectional area (CSA). There were significant differences (p < 0.01) in mean median nerve CSA between controls, patients with median sensory nerve conduction velocity ≤40 m/s and patients with absent sensory nerve action potential and between controls, patients with median nerve distal motor latency ≥4.5 ms and patients with absent compound muscle action potentials of the abductor pollicis brevis. This is the first report to define median nerve CSA cutoff values (18 mm(2)) for determining carpal tunnel syndrome severity in patients with absent compound muscle action potentials of the abductor pollicis brevis. Median nerve CSA values below the cutoff values should prompt clinicians to consider other disorders, such as cervical compressive myelopathy.

Additional method for diagnosis of carpal tunnel syndrome: value of the second lumbrical-interossei test (2L-INT)

We examined 57 hands referred with suspected carpal tunnel syndrome (CTS) using the second lumbrical-interossei nerve test (2L-INT) as well as standard test. Sensory nerve conduction velocity (SCV) was detectible in 67% of patients (38/57), the abductor pollicis brevis-compound muscle action potential (APB-CMAP) in 84% (48/57), 2L-CMAP in 96% (55/57) and the first interossei palmares muscle (INT-CMAP) in 100% (57/57). ABP-CMAP was not recorded in patients in whom severe atrophy of the abductor pollicis brevis muscle was evident. As 2L-CMAP is maintained even in the most severe cases of CTS, the 2L-INT method is a valuable test for improving the accuracy of preoperative diagnosis in the electrophysiological diagnosis of CTS.

Second lumbrical-interossei nerve test predicts clinical severity and surgical outcome of carpal tunnel syndrome

The purpose of this study was to examine the utility of the second lumbrical-interossei nerve (2L-IN) test in the diagnosis of carpal tunnel syndrome (CTS). We examined 65 patients with suspected unilateral CTS using the 2L-IN test, in addition to the standard electrophysiological test. The operative cases were divided into three classes of severity based on Padua's neurophysiological classification: extreme CTS (absence of median motor and sensory response); severe CTS (absence of sensory response, abnormal distal motor latency [DML]); and moderate CTS (abnormal sensory nerve conduction velocity, abnormal DML). With the 2L-IN test, the extreme CTS group could be further subdivided into extreme CTS-A (both abductor pollicis brevis [APB]- compound muscle action potential [CMAP] and 2L-CMAP not recordable) and extreme CTS-B (2L-CMAP recordable, APB-CMAP not recordable). Patients with extreme CTS and severe CTS were older, had chronic symptoms, and poorer outcome compared with the moderate CTS patients. Patients of the moderate CTS group were almost all satisfied with the results of surgery. The electrodiagnostic severity correlated with the clinical outcome. Severe strangulation of the thenar muscle branch was identified in patients in the extreme CTS-B group, requiring decompression of the thenar muscle branch rather than conventional simple transverse ligament detachment.

Nerve conduction studies of median motor nerve and median sensory branches according to the severity of carpal tunnel syndrome

OBJECTIVE

To evaluate each digital branch of the median sensory nerve and motor nerves to abductor pollicis brevis (APB) and 2nd lumbrical (2L) according to the severity of carpal tunnel syndrome (CTS).

METHODS

A prospective study was performed in 67 hands of 41 patients with CTS consisting of mild, 23; moderate, 27; and severe cases, 17. Compound muscle action potentials (CMAPs) were obtained from APB and 2L, and median sensory nerve action potentials (SNAPs) were recorded from the thumb to the 4th digit. Parameters analyzed were latency of the median CMAP, latency difference of 2L and first palmar interosseous (PI), as well as latency and baseline to peak amplitude of the median SNAPs.

RESULTS

The onset and peak latencies of the median SNAPs revealed significant differences only in the 2nd digit, according to the severity of CTS, and abnormal rates of the latencies were significantly lower in the 2nd digit to a mild degree. The amplitude of SNAP and sensory nerve conduction velocities were more preserved in the 2nd digit in mild CTS and more affected in the 4th digit in severe CTS. CMAPs were not evoked with APB recording in 4 patients with severe CTS, but obtained in all patients with 2L recording. 2L-PI showed statistical significance according to the severity of CTS.

CONCLUSION

The branch to the 4th digit was mostly involved and the branch to the 2nd digit and 2L were less affected in the progress of CTS. The second digit recorded SNAPs and 2L recorded CMAPs would be valuable in the evaluation of severe CTS.

Value of latency difference of the second lumbrical-interossei as a predictor of carpal tunnel syndrome in uremic patients

BACKGROUND

Routine electrophysiological parameters for diagnosing carpal tunnel syndrome do not detect median neuropathy at wrist in cases with concomitant severe peripheral neuropathy what ever its cause. Uremic patients on dialysis may have hand symptoms that may be because of peripheral neuropathy, carpal tunnel syndrome, or both.

OBJECTIVE

The authors aimed to assess the significance of the second lumbrical-interosseus (2L-INT) latency difference as a predictor of carpal tunnel syndrome in uremic patients on dialysis.

METHODS

Fifty-four consecutive cases (108 hands) of end-stage renal failure on dialysis (hemo or peritoneal) were subjected to routine electrophysiological studies for carpal tunnel syndrome. 2L-INT latency difference was measured in all cases.

RESULTS

The cases (94.3%) had abnormal electrophysiological studies. Routine tests revealed carpal tunnel syndrome in 54 hands, and all of these had prolonged 2L-INT latency difference. Peripheral neuropathy was found in another 42.9% hands, but 75.6% of these had prolonged 2L-INT latency difference, suggesting a concomitant carpal tunnel syndrome, whereas on using the routine neurophysiological studies, only 13.3% were diagnosed as carpal tunnel syndrome. Overall, the frequency of carpal tunnel syndrome in uremic patients on maintenance dialysis using standard nerve conduction parameters was 51.4%; however, the frequency increased substantially to 83.8% if 2L-INT latency difference is included in the criteria for the diagnosis.

CONCLUSIONS

Carpal tunnel syndrome is common in patients with end-stage renal failure on dialysis. 2L-INT latency difference is a sensitive test to predict median neuropathy at wrist in presence of peripheral neuropathy.

Premotor potential study in carpal tunnel syndrome

INTRODUCTION

Premotor potentials (PMPs) precede compound muscle action potentials evoked from the second lumbrical muscle after median nerve stimulation. Although PMP has been identified as a median sensory nerve action potential, few reports have documented the significance of PMP parameters for diagnosing carpal tunnel syndrome (CTS).

METHODS

We investigated the relationships between PMP parameters and results of 6 standard median nerve conduction studies in 74 CTS hands.

RESULTS

Significant correlations were noted in all comparisons. PMP conduction velocity was strongly correlated with the sensory conduction velocity between wrist and digit 2 (r(2) = 0.91). Moreover, PMP parameters were significantly correlated with neurophysiological severity of CTS.

CONCLUSION

Measuring PMP parameters with a second lumbrical-interosseous study may be useful for diagnosing CTS.

A new median motor test: comparison with conventional motor studies in carpal tunnel syndrome

INTRODUCTION

Carpal tunnel syndrome (CTS) is the most commonly operated of entrapment peripheral neuropathies, and its surgical outcome largely depends on the underlying mechanism involved. Early identification of CTS is essential because it is associated with a better prognosis.

AIM

To identify CTS at an earlier stage and hence improve the potential future outcome, the authors propose incorporating a new method of using the second lumbricalis (2L-MC) to register the nerve conduction.

METHODS

We prospectively evaluated 121 of 216 patients with confirmed carpal tunnel syndrome and 49 cases from 25 healthy subjects. According to the accepted criteria of Stevens, we divided our study into two groups of mild CTS and moderate CTS, respectively. Following our proposed method, we stimulated the palm, distal forearm, and elbow and measuring the difference in latency between the second lumbricalis and the second interosseous, in addition to the conventional neurophysiologic assessments.

RESULTS

Seventeen of 109 (15.6%) hands showed a significant difference in latency using 2L-MC within the mild CTS group, while only 4 of 107 (3.7%) within the moderate CTS group remained undiagnosed using this method. In the mild CTS group, motor involvement was only shown to be slightly more sensitive when compared with 2LI-DML.

DISCUSSION

Adding the proposed test to the conventional studies of CTS in our cases presented showed a 14% increased sensitivity in detecting motor dysfunction when compared with conventional studies alone. Therefore, this new 2L-MC study represents a useful technique for assessing early motor involvement in CTS and would only add a few extra minutes to the standard diagnostic procedures. To conclude, we propose that incorporating this study as part of the standard assessment of CTS is given further consideration.

The significance of second lumbrical-interosseous latency comparison in the diagnosis of carpal tunnel syndrome

AIM

To assess the significance of the second lumbrical-interosseous latency (2LI-DML) comparison in the diagnosis of carpal tunnel syndrome (CTS).

PATIENTS AND METHODS

We examined 150 consecutive hands of patients referred with suspected CTS, using the 2LI-DML test and other standard measures of median nerve function. Correlations of the 2LI-DML test with standard tests were computed.

RESULTS

Hundred and four hands were electrophysiologically confirmed to have CTS. The 2LI-DML test was abnormal in 99/104 (95.2%) hands with CTS with a mean value of 1.54 +/- 1.12 ms. Among the other measures, the orthodromic median-ulnar palmar velocity comparison was the most frequently abnormal test (95/104 hands, 91.3%), followed by the double-peak morphology of orthodromic sensory action potential from digit 4 (94/104, 90.4%). The 2LI-DML test significantly correlated, either positively or negatively, with all other standard tests.

CONCLUSION

The 2LI-DML comparison is highly sensitive in diagnosing CTS, even in mild cases in which standard tests fail to detect abnormalities.

Can studies of the second lumbrical interossei and its premotor potential reduce the number of tests for carpal tunnel syndrome?

The second lumbrical interossei latency difference test (2-LINT) is a frequently used test for diagnosing carpal tunnel syndrome (CTS). Recently, the premotor potential (2-LUMP) observed with 2-LINT was identified as a median sensory potential. 2-LINT recording therefore not only compares conduction across equidistant median and ulnar motor segments, but also registers median sensory conduction. In 52 CTS and 50 control hands, we tested whether motor and sensory data obtained with 2-LINT help to reduce the number of tests necessary to diagnose CTS. The combined sensitivity of 2-LINT derived parameters (2-LUMP latency, median second lumbrical to ulnar interossei latency difference, ulnar digit 5 sensory to 2-LUMP velocity, and ulnar interossei to 2-LUMP latency difference) was 89%, identical to that of combined non-2-LINT derived parameters (median digit 3 sensory velocity, ulnar digit 5 to median digit 3 sensory velocity difference, median abductor pollices brevis [APB] latency, median APB to ulnar abductor digiti minimi latency). The 2-LINT technique with its premotor potential may therefore help to reduce the number of nerve conduction tests commonly needed to investigate patients with suspected CTS.

Optimal recording electrode placement in the lumbrical–interossei comparison study

The lumbrical-interossei comparison study is commonly employed in the electrodiagnosis of carpal tunnel syndrome. Placement of the recording electrodes relies on anatomic landmarks as the muscles being recorded cannot be seen or palpated. To determine the optimal active electrode location, 15 controls and 5 patients were studied using a grid of 12 electrodes placed over the lateral palm. Amplitudes, rise-times, and latencies of the responses at each location were measured. The lowest control latency difference was located in the lateral mid-proximal palm (mean 0 ms, upper range of 0.5 ms). This location also had the highest lumbrical amplitude and rise-time. More distal in the palm, the mean latency difference increased to 0.5 ms with an upper range of 0.9 ms. When performing the lumbrical-interossei comparison study, it is essential to place the active recording electrode in the optimal location. Failure to do so will result in an increased number of false-positive studies.

Diagnostic utility of waveform analysis of compound muscle action potentials for carpal tunnel syndrome

PURPOSE

To determine the diagnostic utility of waveform analysis of compound muscle action potentials (CMAP) for carpal tunnel syndrome (CTS).

METHODS

A total of 131 hands in 71 patients diagnosed with CTS (grouped according to severity) and 80 hands in 44 normal subjects were evaluated using nerve conduction test through the carpal tunnel combined with waveform analysis of CMAP.

RESULTS

Compared to normal subjects, the sensory nerve conduction velocity and mean frequency of the CMAP waveform were significantly reduced in patients with CTS. Compared with distal motor latency and sensory nerve conduction velocity, the mean frequency of the CMAP decreased significantly with increasing clinical severity.

CONCLUSION

This study suggests that waveform analysis of CMAP is of diagnostic value in CTS, and is also of value in objective evaluation of postoperative recovery of carpal median nerve dysfunction.

Value of the lumbrical-interosseous technique in carpal tunnel syndrome

OBJECTIVE

To determine whether the second lumbrical-interosseous technique has comparable sensitivity with the median-ulnar transcarpal mixed nerve technique (palmdiff).

DESIGN

A prospective series of consecutive patients with median distribution paresthesias were evaluated with electrodiagnostic testing. Outpatient veterans referred by a heterogeneous group of specialists and generalists to the Portland Veterans Affairs Medical Center electrodiagnostic laboratory. A total of 129 consecutive veterans referred for evaluation of median distribution paresthesias were assessed with two electrodiagnostic tests.

RESULTS

The second lumbrical-interosseous technique performed with equal sensitivity (60.5%) to the palmdiff technique, with the added unique feature of its being uniformly obtainable.

CONCLUSIONS

The second lumbrical-interosseous technique is characterized by performance equal to the palmdiff in categorizing carpal tunnel syndrome. It is also characterized by being nearly uniformly obtainable, even in severe carpal tunnel syndrome. These features suggest a wider role for the second lumbrical-interosseous technique than currently accepted.

Lumbrical and interossei recording in severe carpal tunnel syndrome

Patients with severe carpal tunnel syndrome (CTS) may occasionally have absent median motor and sensory responses; in these cases, it is not possible to accurately localize the median mononeuropathy to the wrist using standard electrodiagnostic tests. We prospectively investigated the use of comparing the median motor latency to the second lumbrical and the ulnar motor latency to the interossei muscles in 28 patient hands with severe CTS and absent median motor and sensory responses. We found a prolonged latency difference in 92.8%. Along with its use in mild CTS, study of the lumbrical-interossei latency difference is helpful in patients with severe CTS with absent median motor and sensory responses.

Transcarpal motor conduction velocity in carpal tunnel syndrome

Transcarpal motor conduction to abductor pollicis brevis (APB) was evaluated in 43 patients (70 hands) with suspected carpal tunnel syndrome (CTS). Transcarpal motor conduction was abnormal in 80% of hands compared with 11.5% with prolongated distal motor latency from wrist stimulation. Transcarpal motor conduction was comparable in sensitivity with transcarpal sensory conduction and 2nd lumbrical-interosseous latency difference. Transcarpal motor conduction is a sensitive test for diagnosis of CTS. Sensory fibers were no more susceptible than motor fibers to compression in the carpal tunnel, and fibers to APB were as susceptible as those to the 2nd lumbrical muscle.

[Carpal tunnel syndrome. Current approaches]

A clinical, epidemiological and nerve conduction studies report on carpal tunnel syndrome was done after electrophysiological author's experience on 668 cases and literature review. The median nerve underwent focal (nodal) or segmental demyelination after compression on carpal tunnel, 3-4 distal to wrist fold. The symptomatic complex includes nocturnal hands numbness and paraesthesia, mostly bilateral and between 40-60 years old. Familial cases are described and the gene could encode thick transverse carpal ligament. Anthropomorphic findings could also bring about an additional risk, but with low significance. Magnetic resonance could be a useful tool for selected atypical cases. Conservative treatment and controversies on surgery timing are discussed. Classical conduction studies on median nerve reveal a prolonged distal segmental sensory latency and also on distal motor latency. Increasing sensitivity may be reach using additional methods such as, median mixed mid-palm latency, comparative mid-palm latency median/ulnar, comparative sensory latency median/radial and median/ulnar, inching method from wrist to palm recording on index/middle finger and comparative motor median/ulnar recording on lumbrical/interosseous muscle.

[Carpal tunnel syndrome: sensory median-radial latency difference versus conduction studies in 1059 hands (668 cases)]

Between January 1989 and June 1996, 1,059 carpal tunnel syndrome hands (CTS) from 668 patients were studied. None had been previously operated and all had bilateral conduction studies; peripheral neuropathy was excluded. The patients were selected with sensory median/radial difference (MRD) > or = 1.0 ms that strongly supports electrodiagnosis of CTS (standard deviation > 6) after simultaneous stimulation on wrist and recording on thumb. Normal MRD were obtained in 125 hands with upper limit of normality = 0.43 ms (mean + 2SD). The age ranged from 17 to 83 years (mean 47.5) and 91.3% were female. MRD > or = 1.0 ms correlates in 95% with median distal motor latency > 4.25 ms (80 mm distance) and with median distal sensory latency to index finger > or = 3.01 ms, middle finger > or = 3.14 ms and ring finger > or = 3.26 ms, all of them 140 mm distance, antidromic and onset-measured. The results have brought new values for the limit of normality in our EMG laboratory since MRD > or = 1.0 ms is very sensitive for CTS diagnosis.

Electrophysiological studies in mild idiopathic carpal tunnel syndrome

Many techniques have been reported to improve the diagnosis of carpal tunnel syndrome (CTS), but there is no agreement on the diagnostic yield of these different methods. We used an electrophysiological protocol including the assessment of the orthodromic sensory conduction velocity of the median nerve along the carpal tunnel, comparison of median and ulnar sensory conduction between the ring finger and wrist, short segment incremental median sensory nerve conduction across the carpal tunnel recording from the III digit ('inching test'), the study of the refractory period of transmission (RPT) and calculation of the distoproximal ratio obtained by dividing the nerve conduction velocity in the median nerve between the third digit and the palm and between the palm and wrist in 41 patients with mild CTS (75 symptomatic hands) and in 45 control subjects. The distoproximal ratio calculation was the most sensitive technique (81%), but was also the least specific. The 'inching test', even though less sensitive, had the advantage of localising focal abnormalities of the median nerve along the carpal tunnel. RPT was abnormal in patients with recent symptoms. Combining the different techniques, an overall sensitivity of 92% was reached, 11% higher than the yield of the single best test suggesting that a multimodal approach could be useful. The best procedure for electrodiagnosis of mild CTS was to combine the median/ulnar comparison test with calculation of the disto-proximal ratio.

Neurophysiological classification and sensitivity in 500 carpal tunnel syndrome hands

OBJECTIVES

To evaluate the following points about carpal tunnel syndrome (CTS): 1) characterization of a wide population; 2) sensitivity of electrodiagnostic tests, and particularly the contribution of disto-proximal ratio test; 3) validity of a neurophysiological classification developed by us.

MATERIAL AND METHODS

Prospective study in 500 hands with CTS symptoms. Neurophysiological "standard" tests were always performed: sensory nerve conduction velocity (SNCV) first- and third digit-wrist and distal motor latency (DML). In "standard negative" hands disto-proximal ratio technique (R) was performed. Neurophysiological classification: Extreme CTS (absence of median motor, sensory responses), Severe (absence of sensory response, abnormal DML), Moderate (abnormal SNCV, abnormal DML), Mild (abnormal SNCV, normal DML), Minimal (abnormal R or other segmental/comparative test, normal standard tests).

RESULTS

Sensibility of standard tests: 77%. R increased the diagnostic yield by 20%. CTS classification appeared reliable with significant differences between groups.

CONCLUSION

R is a useful test, the classification may be useful in clinical/therapeutical decisions.

Coactivation of the ulnar nerve in motor tests for carpal tunnel syndrome

Coactivation of the ulnar nerve at the wrist can be a source of error in tests for carpal tunnel syndrome (CTS). We compared the effects of coactivation in two tests for CTS: the abductor pollicis brevis-distal motor latency (APB-DML) and lumbrical-interosseus-distal motor latency difference (2LI-DML). We studied 33 hands of 25 consecutive patients referred for suspected CTS. In severe CTS, when selective supramaximal stimulation of the median nerve was impossible, all APB-compound muscle action potentials (CMAP) showed abnormalities, indicating volume conduction of ulnar muscle activation. 2LI-DML in these hands led to falsely normal test results, as two identical CMAP were obtained after median and ulnar stimulation. In less severe CTS, warning signs indicating coactivation were observed in APB-DML virtually as often as in 2LI-DML. Undetected coactivation was more likely to be associated with false normal test results in 2LI-DML than in APB-DML.

Neurophysiological classification of carpal tunnel syndrome: assessment of 600 symptomatic hands

Following the AAEM electrodiagnostic guidelines, we developed a neurophysiological classification of carpal tunnel syndrome (CTS). Six hundred hands with clinical CTS (mean age 51.4 yr., female/male ratio 5.5/1, right/left ratio 1.8/1) were prospectively evaluated and divided into six classes of severity only on the basis of median nerve electrodiagnostic findings: extreme CTS (EXT-absence of thenar motor responses), severe CTS (SEV-absence of sensory response and abnormal distal motor latency-DML), moderate CTS (MOD-abnormal digit-wrist conduction and abnormal DML), mild CTS (MILD-abnormal digit wrist conduction and normal DML), minimal CTS (MIN-exclusive abnormal segmental and/or comparative study), and negative CTS (NEG-normal findings at all tests). Using this neurophysiological classification, the CTS groups appeared normally distributed (EXT 3% of cases, SEV 14%, MOD 36%, MILD 24%, MIN 21%, NEG 3%), and the age of patients and clinical findings appeared to be related to neurophysiological abnormalities. Significant differences in median neurophysiological parameters not included in the classification (such as palm-wrist sensory conduction velocity) were observed in the different CTS groups. The analysis of the groups showed that: 1) the majority of advanced cases (SEV and EXT) occurred in older patients (60-80 years), 2) most of the milder cases (MIN and MILD) occurred in young female patients. The aim of this study was to standardise the neurophysiological evaluation of CTS.