Electrodiagnosis of carpal tunnel syndrome: which transcarpal conduction technique is best?

Transcarpal conduction techniques are commonly used to be supplementary techniques to distal sensory and motor latencies (DSL and DML) in the electrodiagnosis of carpal tunnel syndrome (CTS). However, which transcarpal conduction techniques, or combination of techniques, are the most sensitive for the electrodiagnosis of CTS is unknown. To determine which transcarpal conduction technique is the most sensitive for the electrodiagnosis of CTS, we prospectively conduct this study. Study subjects were 100 patients with CTS and 50 controls. In addition to DSL and DML determinations, all subjects were evaluated using four transcarpal conduction techniques. These were (1) median wrist-palm sensory conduction time (W-Psen CT); (2) median wrist-palm mixed nerve conduction time (W-Pmix CT); (3) the difference of conduction time across wrist between median and ulnar nerves (W-Pmix M-U CT); and (4) median wrist-palm motor conduction velocity (W-Pmot CV). The sensitivities and specificities of these tests were compared. Ninety patients had one or more electrophysiologic abnormalities. The DSL and DML diagnostic sensitivities were 74% and 72%, respectively. Better sensitivities were obtained with W-Psen CT (82%), W-Pmot CV (81%), W-Pmix CT (78%), and W-Pmix M-U CT (79%). Compared between four transcarpal conduction techniques, there was no significant difference in sensitivity. Of 26 patients with CTS with normal DSL, additional electrophysiologic abnormalities were revealed with W-Psen CT (30.7%), W-Pmot CV (53.8%), W-Pmix CT (30.7%), or W-Pmix M-U CT (38.5%). When W-Pmot CV was compared with W-Psen CT and W-Pmot CV versus W-Pmix CT, calculated probabilities (P = 0.07) showed a clear trend toward statistical significance. Furthermore, of 20 patients with normal DSL and DML, five patients had abnormality for W-Psen CT, eight for W-Pmot CV, four for W-Pmix CT, and six for W-Pmix M-U CT. On the basis of the results, we concluded that the most simple and reliable transcarpal conduction for electrodiagnosis of CTS was W-Psen CT. The most sensitive technique was W-Pmot CV in subjects with normal DSL or with normal DSL and DML. Evaluation of transcarpal motor conduction affords a useful supplementary technique to W-Psen CT.

Alteration of proximal conduction velocity at distal nerve injury in carpal tunnel syndrome: demyelinating versus axonal change.

The objective of this study was to determine the cause of median forearm motor conduction velocity (FMCV) slowing in patients with carpal tunnel syndrome, due to either focal conduction abnormality over wrist or retrograde conduction slowing, and to decide whether the slowing is related to severity of compression or not. Fifty carpal tunnel syndrome patients confirmed by conventional nerve conduction study with abnormal electromyography of the abductor pollicis brevis muscle were group 1, and 100 with normal electromyography, group 2. One hundred volunteers served as controls. In addition to conventional nerve conduction study of median and ulnar nerves, palmar stimulations for median mixed and motor nerves were also performed to calculate wrist-palm mixed nerve conduction time and motor conduction velocity (W-P MCV). For group 1, group 2, and control subjects, respectively, W-P MCV were 19.73+/-7.65 (mean+/-SD), 32.7+/-6.83, and 52.75+/-6.4 m/s, whereas median FMCV were 48.63+/-8.32, 54.42+/-2.11, and 57.86+/-4.24 m/s. There was a significant reduction in the W-P MCV (62.6%, P<0.00001) and a decrease in the median FMCV (15.95%, P<0.00001) in group 1, and 38% reduction in W-P MCV (P<0.00001) and 5.9% decrease in median FMCV (P<0.00001) in group 2 when compared with controls, but ulnar FMCV and sensory nerve conduction study results did not, suggesting the reduction of median W-P MCV is not parallel with that of median FMCV in both patients groups. Furthermore, there is a poor correlation of median FMCV and W-P MCV in patient groups, implying conduction blockage of the large myelinating fibers at the wrist, leaving only slower axons to be measured, is not the likely cause of reduction of FMCV. In addition, the reduction of compound muscle action potential amplitude of abductor pollicis brevis muscle, conduction block at wrist and weak correlation of median FMCV and compound muscle action potential amplitude of abductor pollicis brevis exclusively occurred in group 1. Therefore, the retrograde conduction slowing really occurs among patients with carpal tunnel syndrome-markedly in those with abnormal electromyography and mildly in those with only demyelination. This finding counters conventional wisdom that nerve function changes only in segments distal to injured sites.

Post-irradiation myokymia and neuromyotonia in unilateral tongue and mentalis muscles: report of a case.

We report a 52-year-old man with slowly progressive dysarthria and dysphagia for about 11 years after radiation therapy of nasopharyngeal carcinoma. Neurological examination revealed atrophy and myokymia on the left side of the tongue and in the left mentalis muscles. Electrical discharges of myokymia and neuromyotonia were also observed in the aforementioned muscles, suggesting increased motor axonal membrane excitability involving the left hypoglossal nerve and the marginal mendibular branch of the left facial nerve. Magnetic resonance imaging of the brain did not show any evidence of tumor recurrence, indicating that irradiation probably plays an important role in pathogenesis. Focal myokymia with concomitant neuromyotonia in unilateral tongue and mentalis muscles could be an unusual delayed manifestation after radiation therapy.

Comparison of sensitivity of transcarpal median motor conduction velocity and conventional conduction techniques in electrodiagnosis of carpal tunnel syndrome.

OBJECTIVE: To compare the sensitivity of median wrist-palm motor conduction velocity (W-P MCV) with those of standard sensory conduction techniques in the electrodiagnosis of carpal tunnel syndrome (CTS). METHODS: This study included 280 consecutively suspected CTS patients (360 hands) referred for evaluation and 150 volunteers who served as controls. We determined and calculated (1) median W-P MCV, (2) median motor distal latencies (DL) and median sensory DL for (3) thumb (D1), (4) index (D2) and (5) ring finger (D4), (6) median wrist-palm sensory conduction velocity (W-P SCV) and sensory conduction time (W-P SCT) for index finger and sensory latency differences between (7) median-radial (M-R) for thumb and (8) median-ulnar (M-U) nerves for ring finger. The normal limits were calculated from the median of normal controls +/-2.5 standard deviations. The sensitivities of each test were determined and compared. RESULTS: Among the 360 hands with suspected CTS, 32 hands (8.9%) had normal electrodiagnostic studies and 328 (91.1%) had at least one abnormal electrodiagnostic study. Among the 328 hands with abnormalities, 234 (65%) had abnormal motor DL and 294 (81.7%) had abnormal W-P MCV. The sensitivity was 80.3% for D1, 72.5% for D2, 76.7% for D4, 86.7% for M-R (specificity, 98.7%), 87.2% for M-U (specificity, 96.7%), 80.8% for sensory W-P SCT and 73.6% for W-P SCV. CONCLUSIONS: W-P MCV is a valuable motor conduction technique for the diagnosis of CTS and it is confirmed again that W-P MCV is equal to or more sensitive than W-P SCV and W-P SCT. Furthermore, the findings of the present study are in agreement with the conventional wisdom that internal comparison of latency differences between median and ulnar or radial nerves is the best method for a diagnosis of patients with suspected CTS. Therefore, we recommend that CTS patients be studied according to the following steps: (1) routine sensory and motor DL, (2) if step 1 is negative, then perform and determine W-P MCV or SCT. This may increase the diagnostic yield of 10%, (3) if step 2 is negative, measure the M-U or MR. These are the final and more sensitive techniques in making a diagnosis with an additional diagnostic yield of 10%. SIGNIFICANCE: We provide the evidence of W-P MCV that could be a standard technique for electrodiagnosis of CTS. Furthermore, we make a reasonable flow chart and recommendation for electrodiagnosis of CTS for electromyographers.

Does retrograde axonal atrophy really occur in carpal tunnel syndrome patients with normal forearm conduction velocity?

OBJECTIVE: The cause of decreased median forearm motor conduction velocity (FMCV) in carpal tunnel syndrome (CTS) is best ascribed to retrograde axonal atrophy (RAA); however, the relationships between the occurrence of RAA and electrophysiological or clinical severity remains controversial. We attempt to determine whether RAA really occurs in CTS patients with normal median FMCV and to investigate any relationships between RAA and severity of compression at the wrist. METHODS: Consecutive CTS patients were enrolled and age-matched volunteers served as controls. We performed conventional nerve conduction studies (NCS) and measured median and ulnar distal motor latencies (DML), FMCV, compound muscle action potential (CMAP) amplitudes, distal sensory latencies (DSL), and sensory nerve action potential (SNAP) amplitudes. Furthermore, palmar median stimulation was done to calculate the wrist-palm motor conduction velocity (W-P MCV). Patients included for analysis should have normal FMCV and needle examination. We compared each electrodiagnostic parameters between the patient group and controls. RESULTS: The mean+/-SD of the W-P MCV for patients and controls were 33.26+/-6.74 and 52.14+/-5.85 m/s and those of median FMCV were 55.26+/-3.56 and 57.82+/-3.9 m/s, respectively. There was a significant reduction in the W-P MCV (36.2%, P<0.00001), significant decrease in the median FMCV (4.43%, P<0.00001) and SNAP amplitudes, and an increase of the DML and DSL in the patient group (P<0.00001) compared to the controls; however, there were no differences in median and ulnar CMAP amplitudes, ulnar FMCV and DML between the controls and patients. CONCLUSIONS: RAA and relatively slowed median FMCV do occur in CTS patients with normal median FMCV, regardless of severity of clinical manifestations and electrophysiological abnormalities. SIGNIFICANCE: This article provides new information for research of the electrophysiological changes of the proximal nerve part at distal injury.

Clinical findings of intracranial vertebral artery disease using magnetic resonance angiography.

The vertebral artery lesion has a variety of clinical characteristics. We sought to clarify the clinical patterns and the location of the intracranial vertebral artery (ICVA) diseases according to analyses of images obtained using magnetic resonance angiography (MRA). We studied vascular lesions, risk factors, symptoms, signs, and outcomes in 35 patients with ICVA disease (3 had bilateral occlusion; 9, unilateral occlusion; 6, bilateral stenosis; and 17, unilateral stenosis). The most common site of unilateral and bilateral lesions was the distal ICVA after the origin of posterior inferior cerebellar artery (PICA). We found accompanying basilar artery disease in 28.6% of patients with unilateral and bilateral ICVA disease. The majority of the ICVA lesions were associated with internal carotid arteries disease (48.8%). The common vascular risk factors were hypertension (71%), diabetes mellitus (34%), hyperlipidemia (31%), smoking (29%), and coronary artery disease (23%). Eighteen patients (51.4%) had transient ischemic attacks (TIAs) only, 10 patients (28.6%) had TIAs before stroke, and 5 patients (14.3%) had strokes without TIAs. Most patients (80%) with TIAs, with or without stroke, had multiple episodes. Vertigo or dizziness, ataxia, limbs weakness and abnormal gait were the common symptoms and signs. At 6 months follow-up, 66.7% patients had no symptoms or only slight symptoms that caused no disability. Our data showed (1) the usual location of ICVA disease (occlusion or severe stenosis) was distal to PICA, especially near the vertebrobasilar junction; (2) the risk factors were hypertension, diabetes mellitus, hyperlipidemia, smoking, and coronary artery disease; (3) patients with ICVA disease had a high frequency of accompanying internal carotid, middle cerebral, or basilar artery disease; (4) vertigo or dizziness, and ataxia were the common symptoms and signs; (5) TIA was the most common clinical pattern; (6) the outcome was favorable, except in cases with bilateral ICVA occlusion.