Normal median nerve proximal latency in carpal tunnel syndrome: a clue to coexisting Martin-Gruber anastomosis.

Five of 65 patients referred for electrodiagnosis because of clinical evidence of carpal tunnel syndrome were found to have near normal latency on proximal stimulation of the median nerve, although the distal motor latency was prolonged. In one patient, the proximal latency was actually shorter than the distal latency. The failure of the proximal latency to be prolonged in proportion to the distal latency results in a spuriously high apparent conduction velocity in the forearm segment of the nerve. This value may even exceed the conduction velocity of the corresponding nerve segment in the unaffected arm. Stimulation studies on the ulnar nerve reveal that this disparity is the result of some of the median nerve fibres destined for the thenar muscles taking an aberrant course through the ulnar nerve and thus escaping compression at the wrist. A median-ulnar communication in the forearm, the 'Martin-Gruber' anastomosis, may occur in up to 15% of the population. The presence of the Martin-Gruber anastomosis in patients with carpal tunnel syndrome results in a partial or total sparing of thenar muscles from denervation and the paradoxical recording of normal proximal latencies in the median nerve when the distal latency is prolonged.     

Effects of spasticity and hemiplegic posture on median nerve and carpal tunnel in stroke patients: Electrophysiological and ultrasonographic evaluation

This study aims to evaluate whether the upper extremity spasticity and hemiplegic posture have any effect on the morphology of the carpal tunnel and median nerve in stroke patients. Nerve conduction studies (NCS) were performed in 46 stroke patients and compared to those of 30 healthy controls. The cross-sectional area (CSA) of the carpal tunnel (CT) and median nerve (wrist/mid-forearm levels) was assessed by ultrasonography. The mean ages of the stroke and control group were 55.6 ± 13.5 and 56 ± 12.1 years, respectively. The median spasticity score of the forearm pronators and wrist flexor muscles was 2 (0–4) according to the Modified Ashworth Scale (MAS). The compound muscle action potential (CMAP) of the median nerve was reduced (10,093 ± 4,451 mV) when compared to non-paretic side (11,615 ± 4,397 mV) (p:0.02) and the CSA of the CT was thinner on the paretic side (1.9 ± 0.3 cm² vs 2.08 ± 0.2 cm²) (p:0.03). Pronator spasticity had no significant effect on the CSA of the median nerve and NCS at the forearm level. The CSA of the median nerve at the wrist was significantly thicker in patients with the wrist flexor spasticity graded II (MAS) and above compared to those with spasticity graded I and below (9.5 ± 1.7 mm² and 8.7 ± 1.7 mm² respectively) (p:0.03). However, the thickening of the median nerve didn’t cause significant abnormalities in NCS. This study shows that in stroke patients, wrist flexor spasticity and hemiplegic wrist posture can cause explicit morphological changes in the CT and median nerve albeit normal findings on NCS.     

Characteristics of forearm mixed nerve conduction study in carpal tunnel syndrome: Comparison with ultrasound assessments

This study aimed to characterize forearm mixed nerve conduction study (NCS) findings in carpal tunnel syndrome (CTS). Eighty-two patients with CTS and 48 healthy controls were enrolled. We directly compared the forearm mixed NCS and ultrasonography results from CTS patients with those from the controls. Correlation analyses were performed to identify the relationship between forearm mixed NCS parameters and ultrasound measurements in CTS. We observed reduced forearm mixed nerve amplitude and increased cross-sectional area (CSA) of the median nerve at the proximal carpal tunnel (CT) inlet in CTS. The forearm mixed nerve amplitude negatively correlated with the CSA at the proximal CT inlet. We found a negative correlation between Bland's neurophysiological grade and the forearm mixed nerve amplitude as well as a positive correlation between the CSA of the median nerve at the proximal CT inlet and Bland's neurophysiological grade. We confirmed that the reduced median mixed nerve amplitude is the distinguishing feature of forearm mixed NCS in CTS. Our findings suggest that the forearm mixed NCS is potentially useful in evaluating its severity.     

Management of extreme carpal tunnel syndrome: Evidence from a long‐term follow‐up study

Extreme carpal tunnel syndrome (CTS) is characterized by severe thenar atrophy, plegia of the abductor pollicis brevis (APB), fixed sensory deficit in the median nerve distribution, and absence of median motor and sensory responses on electrophysiological examination. In this study we report long‐term follow‐up of 37 patients with extreme CTS. Of the 24 patients with idiopathic extreme CTS, 9 were untreated, and 3 received conservative treatment. At follow‐up, none of these patients showed objective or electrophysiological improvement, and all but 1 still reported positive symptoms. Conversely, 12 patients (14 hands) who underwent carpal tunnel release showed: resolution of positive symptoms in all but 1 hand; reappearance of median compound muscle action potentials (4.2 ± 0.6 mV); reappearance of sensory nerve action potentials in all but 1 (7.9 ± 0.8 μV); improvement of APB strength to grade 4 or 5 on the Medical Research Council scale in 11 hands; and resolution of hypesthesia in 1 hand. Six of 13 patients with non‐idiopathic extreme CTS were operated. Of the 6, we found no or poor reinnervation in 3 patients, restoration of nerve responses and normal APB strength but no relief from pain and/or paresthesia in 2, and full recovery in 1. If untreated, extreme CTS is an irreversible condition. Although the outcome is considered to be disappointing in such cases, carpal tunnel release provides long‐term relief, significant sensorimotor reinnervation, and improvement of motor deficit in most patients. It should be considered to be the first‐choice treatment for idiopathic extreme CTS. Associated diseases do not necessarily imply a poor surgical outcome. Muscle Nerve, 2009     

Single injection of platelet-rich plasma as a novel treatment of carpal tunnel syndrome

Both in vitro and in vivo experiments have confirmed that platelet-rich plasma has therapeutic effects on many neuropathies, but its effects on carpal tunnel syndrome remain poorly understood. We aimed to investigate whether single injection of platelet-rich plasma can improve the clinical symptoms of carpal tunnel syndrome. Fourteen patients presenting with median nerve injury who had suffered from mild carpal tunnel syndrome for over 3 months were included in this study. Under ultrasound guidance, 1–2 mL of platelet-rich plasma was injected into the region around the median nerve at the proximal edge of the carpal tunnel. At 1 month after single injection of platelet-rich plasma, Visual Analogue Scale results showed that pain almost disappeared in eight patients and it was obviously alleviated in three patients. Simultaneously, the disabilities of the arm, shoulder and hand questionnaire showed that upper limb function was obviously improved. In addition, no ultrasonographic manifestation of the carpal tunnel syndrome was found in five patients during ultrasonographic measurement of the width of the median nerve. During 3-month follow-up, the pain was not greatly alleviated in three patients. These findings show very encouraging mid-term outcomes regarding use of platelet-rich plasma for the treatment of carpal tunnel syndrome.     

Does forearm mixed nerve conduction velocity reflect retrograde changes in carpal tunnel syndrome?

The mixed nerve conduction velocity of the median nerve in the forearm diverged from the motor and sensory nerve conduction velocities and correlated poorly with the severity of carpal tunnel syndrome (CTS) in 61 hands. In contrast, the motor and sensory nerve conduction velocities in the forearm correlated well with CTS severity. The mixed nerve conduction velocity in the forearm is probably determined by nonlesioned fibers such as those from the cutaneous palmar branch of the median nerve. The motor and sensory, but not the mixed nerve conduction velocities in the forearm may be used to estimate possible retrograde impairment in CTS. © 1994 John Wiley & Sons, Inc.     

Sensitive median–ulnar motor comparative techniques in carpal tunnel syndrome

We describe two modified methods for median‐to‐ulnar motor conduction comparison in the diagnosis of median neuropathy at the wrist: the median–thenar to ulnar–thenar latency difference (TTLD), and the median–thenar to ulnar–hypothenar latency difference (THLD). We also describe an F‐wave ulnar‐to‐median comparative test, the F‐wave latency difference (FWLD). The abnormal cutoffs based upon 34 normal controls are: TTLD, 0.8 ms; THLD, 1.2 ms; FWLD, 0.6 ms. In 50 patients (79 hands) with clinically defined carpal tunnel syndrome and electrophysiological evidence of median neuropathy at the wrist (based upon a prolonged median nerve palm–wrist latency), the diagnostic sensitivities were: 95–98%, 85–88%, and 75–78%, respectively. These tests are therefore highly sensitive. They are easily performed and require minimal additional effort to incorporate into commonly used clinical electrodiagnostic routines. They may be advantageous when a concomitant polyneuropathy is present, and they may also help avoid technical pitfalls and aid in identification of anatomic variants. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 88–98, 1999     

Predictive value of nerve conduction measurements at the carpal tunnel

We compared the predictive values of three measurements of sensory conduction of the median nerve at the carpal tunnel (maximum latency difference [MLD], 8-cm latency [S8], and 14-cm latency [S14]) in 2334 hands of industrial workers, workers' compensation patients, and students, The MLD was determined by the centimetric technique. The MLD was the most sensitive and efficient measurement for predicting carpal tunnel syndrome (CTS). An MLD ≥ 0.40 ms correctly identified 86.3% of 753 hands with CTS. The MLD correlated best with CTS and with the primary diagnostic category (CAT). MLD was the second factor selected in stepwise regression analysis for CAT (numbness was first and S8 was third). The MLD was the most important factor for predicting persistent or de novo CTS in a 5-year follow-up of 630 hands. Thus, the MLD was the most reliable nerve conduction study measurement for predicting current or future CTS in these subjects' hands.     

The carpal tunnel syndrome: localization of conduction abnormalities within the distal segment of the median nerve.

Palmar stimulation was used to assess median nerve conduction across the carpal tunnel in 61 control patients and 105 patients with the carpal tunnel syndrome. With serial stimulation from midpalm to distal forearm the sensory axons normally showed a predictable latency change of 0.16 to 0.21 ms/cm as the stimulus site was moved proximally in 1 cm increments. In 47 (52 per cent) of 91 affected nerves tested serially, there was a sharply localized latency increase across a 1 cm segment, most commonly 2 to 4 cm distally to the origin of the transverse carpal ligament. In these hands, the focal latency change across the affected 1 cm segment (mean +/- SD: 0.80 +/- 0.22 ms/cm) averaged more than four times that of the adjoining distal (0.19 +/- 0.09 ms/cm) or proximal 1 cm segments (0.19 +/- 0.08 ms/cm). In the remaining 44 (48 per cent) hands, the latency increase was distributed more evenly across the carpal tunnel. Unlike the sensory axons the motor axons were difficult to test serially because of the recurrent course of the thenar nerve, which may be contained in a separate tunnel. The wrist-to-palm latency was significantly greater in the patients with carpal tunnel syndromes than in the controls for sensory (2.18 +/- 0.48 ms v 1.41 +/- 0.18 ms) and motor axons (2.79 +/- 0.93 ms v 1.50 +/- 0.21 ms). Consequently, there was considerable difference between the carpal tunnel syndromes and controls in SNCV (38.5 +/- 7.5 m/s v 57.3 +/- 6.9 m/s), and MNCV (28.2 +/- 4.5 m/s v 49.0 +/- 5.7 m/s). In the remaining distal segment, however, there was only a small difference between the two groups in sensory (1.48 +/- 0.28 ms v 1.41 +/- 0.22 ms) and motor latency (2.15 +/- 0.34 ms v 2.10 +/- 0.31 ms). The exclusion of the relatively normal distal latency made it possible to demonstrate mild slowing across the carpal tunnel in 36 (21 per cent) sensory and 40 (23 per cent) motor axons of 172 affected nerves when the conventional terminal latencies were normal. Sensory or motor conduction abnormalities were found in all but 13 (8 per cent) hands. Without palmar stimulation, however, an additional 32 (19 per cent) hands would have been regarded as normal.     

Improved inching method for the diagnosis and prognosis of carpal tunnel syndrome.

A modified sensory "inching" method for the electrodiagnosis of carpal tunnel syndrome (CTS) is described. The median nerve as stimulated at the cubital portion, with 8 channel recording electrodes placed along the nerve across the carpal tunnel. In most of the CTS cases, there was a conductive abnormality from 3 to 4.5 cm distal to the proximal ending of the flexor retinaculum. Subjects' values, obtained by subtracting the theoretical latency from the measured latency, which were more than 0.6 ms, could not be improved by conservative therapy. As we could determine from subtle change at the short span of nerve conduction, below the electrodes from the proximal to the affected site of the carpal tunnel, this method provides high sensitivity and specificity for the diagnosis of CTS.     

Conduction velocity in the forearm segment of the median nerve in patients with impaired conduction through the carpal tunnel

Conduction velocity, in the forearm segment of the median nerve, has been investigated in a group of patients with carpal tunnel syndrome. Motor conduction velocity was reduced below 50 m/s in 18% of the sample. Although a correlation between severity of compression and forearm motor conduction velocity was demonstrated, it was weak (r = 0.51) and slow forearm velocities occurred i n some patients who had only a minor abnormality at the carpal tunnel itself. In patients with uncomplicated carpal tunnel syndrome, slow motor conduction in the forearm segment of the median nerve was accompanied by only a small reduction (approx. 5 m/s) in mixed nerve conduction velocity. By contrast, in patients whose abnormality at the carpal tunnel was accompanied by evidence of a more widespread sensorimotor neuropathy, mixed conduction velocity was reduced in parallel with the change in motor conduction velocity.     

拇指感觉神经传导速度诊断轻度腕管综合征的临床应用价值

目的:探讨拇指感觉神经传导速度(sensory nerve conduction velocity,SCV)诊断轻度腕管综合征的临床应用价值。方法:对18例(26只手)轻度腕管综合征的患者和15例(30只手)年龄性别相匹配的正常人,测定了腕部正中神经和桡神经的感觉神经传导速度,并进行对比研究。结果:中指正中神经SCV的异常率为50%,腕部正中神经/桡神经(刺激拇指)SCV差值的异常率为84.6%,明显大于用常规检查方法组(刺激中指),有8例12只手腕部正中神经感觉动作电位(刺激拇指)中出现双峰电位,而对照组则无。结论:在腕管综合征肌电图的诊断中,比较正中神经和桡神经SCV的差值是早期诊断腕管综合征的敏感指标之一。     

Evaluation of carpal tunnel syndrome in patients with polyneuropathy

The difference between the median nerve latency to the second lumbrical muscle and the ulnar nerve latency to the second interosseous muscle (L-I DIFF) was tested in a prospective study to discriminate whether prolonged distal motor latency of the median nerve in patients with polyneuropathy (PNP) reflects an additional carpal tunnel syndrome (CTS). We investigated 92 patients (107 hands) with CTS, 30 patients (34 hands) with PNP, 22 patients (27 hands) with CTS and coexisting PNP (PNP+CTS), and 77 controls (87 hands). L-I DIFF was significantly prolonged in both the CTS and PNP+CTS patients as compared to PNP patients and controls. It proved to be the most specific test to differentiate between diffuse (PNP) and focal (entrapment) nerve disorder. © 1997 John Wiley & Sons, Inc. Muscle Nerve, 20, 153–157, 1997.     

Postoperative nerve conduction changes after open and endoscopic carpal tunnel release.

OBJECTIVE: To assess the improvement of motor distal latency (MDL), sensory nerve conduction velocity (SCV) of the median nerve and the amplitudes of compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) in patients with idiopathic carpal tunnel syndrome subjected to surgical treatment according to the open carpal tunnel release method and the endoscopic carpal tunnel release. METHODS: Sixty-six hands of sixty-six patients were divided into two groups: the ECTR group and the OCTR group. The patients were evaluated preoperatively, and at 1, 3, 6, and 12 months postoperatively. RESULTS: Although no statistically significant difference of the recovery of MDL and the amplitude of CMAP and SNAP was detected between the two groups at any time point during follow-up, one patient in the ECTR group in whom the operation had been converted to OCTR, showed delay of MDL and decrease in the amplitude of CMAP. CONCLUSIONS: There is a risk of nerve damage in patients undergoing ECTR. Although statistical analysis suggests that nerve conduction improves by about the same degree 12 months after ECTR or OCTR, slightly faster improvement after OCTR cannot be excluded.     

The familial occurrence of carpal tunnel syndrome

Epidemiological studies of the carpal tunnel syndrome have generally overlooked the possibility of a familial occurrence. A prospective study was undertaken to determine the prevalence and significance of a positive family history of carpal tunnel syndrome. Seventy-ive of 253 women and 40 of 168 men with a confirmed carpal tunnel syndrome had at least one relative with symptoms of, or surgery for, carpal tunnel syndrome. A positive family history was predictive of a median abnormality or prior surgery at the carpal tunnel (chi-square = 20.484, P < 0.001). The 84 patients with a prior carpal tunnel surgery, likely the most well informed historically, had a positive family history of 39.3% versus 13.3% in the 279 patients without median latency slowing. The familial occurrence appears crucial in the epidemiological study of carpal tunnel syndrome, and may be important in the selection of normal subjects for electrodiagnostic standards. © 1994 John Wiley & Sons, Inc.     

Study on the latency difference between compound muscle and sensory nerve action potentials]

In motor nerve conduction studies compound muscle action potentials (CMAPs) appear later than sensory nerve action potentials (SNAPs). This time lag originates from the conduction delay at the distal motor axon, neuromuscular transmission time and muscle action potential induction time. To investigate the latency difference between CMAPs and SNAPs we studied 46 healthy individuals, 46 patients with diabetes mellitus and 33 patients with carpal tunnel syndrome, using the lumbrical and interossei recording method. In this method the recording active electrode was placed on the 2nd lumbrical muscle and the reference electrode on the proximal palmar aspect of the index finger. Supramaximal stimulation was given to the median or ulnar nerve trunk at 9-cm proximal to the recording active electrode. The CMAP from the 2nd lumbrical muscle (L) and the SNAP from the digital nerve (N) were recorded after median nerve stimulation, and the CMAP from the 2nd interossei muscles (I) was recorded after ulnar nerve stimulation. The residual latency, which is arbitrary defined as the latency difference (L-N) in this study, was 1.38 +/- 0.15 (mean +/- SD) msec in healthy individuals. About 1 msec of the residual latency is regarded as the time for neuromuscular transmission and the time to evoke muscle activities. Thus, the conduction delay at the distal motor axon was calculated as about 0.4 msec in healthy individuals. The residual latency was relatively constant in 29 diabetic patients without conduction delay across the carpal tunnel, which was defined by the latency difference (L-I) < or = 0.4 msec. Their sensory nerve conduction velocities (calculated from N latency) were always above 40 m/sec. On the other hand in diabetic patients with conduction delay across the carpal tunnel, which was defined by the latency difference (L-I) > 0.4 msec, the residual latency gradually increased as the sensory nerve conduction velocity decreased. Their sensory nerve conduction velocities were mostly less than 40 m/sec. The similar relationship was observed in patients with carpal tunnel syndrome without diabetes mellitus. We consider that the diabetic neuropathy alone doesn't cause the increase of the residual latency. Instead, severe conduction delay across the carpal tunnel decreases the N velocity and increases the residual latency. We can also regard the relationship between the latency difference (L-N) and N velocity as being in inverse proportion. Perhaps the increase of the residual latency was simply caused by the proportional decrease in the conduction velocity at the distal motor axon, not by the special mechanism concerning to the carpal tunnel syndrome. This paper presented the electrophysiological changes seen in the distal segment secondary to the proximal entrapment.     

Axonal degeneration of the ulnar nerve secondary to carpal tunnel syndrome: fact or fiction?

The distribution of sensory symptoms in carpal tunnel syndrome is strongly dependent on the degree of electrophysiological dysfunction of the median nerve. The association between carpal tunnel syndrome and ulnar nerve entrapment is still unclear. In this study, we measured ulnar nerve function in 82 patients with carpal tunnel syndrome. The patients were divided into group I with minimal carpal tunnel syndrome (n = 35) and group II with mild to moderate carpal tunnel syndrome (n = 47) according to electrophysiological data. Sixty-one age- and sex-matched subjects without carpal tunnel syndrome were used as a control group. There were no significant differences in ulnar sensory nerve peak latencies or conduction velocities from the 4th and 5th fingers between patients with carpal tunnel syndrome and the control group. The ulnar sensory nerve action potential amplitudes from the 4th and 5th fingers were lower in patients with carpal tunnel syndrome than in the control group. The ratios of the ulnar sensory nerve action potential amplitudes from the 4th and 5th fingers were almost the same in patients with carpal tunnel syndrome as in the control group. These findings indicate that in patients with minimal to moderate carpal tunnel syndrome, there is some electrophysiological evidence of traction on the adjacent ulnar nerve fibers. The findings do not indicate axonal degeneration of the ulnar nerve.     

Forearm mixed nerve conduction velocity: questionable role in the evaluation of retrograde axonal atrophy in carpal tunnel syndrome.

The objective of this study was to determine whether forearm mixed nerve conduction velocity (Fmix) reflects the real conduction velocity of forearm motor nerve (Fmot) and forearm sensory nerve (Fsen) fibers passing through the carpal tunnel. Forearm mixed nerve conduction velocity is presumed to be indicative of the conduction velocity of the median nerve over the forearm. Therefore, Fmix is used widely to assess the causes of slowing forearm conduction velocity in carpal tunnel syndrome. However, some authors claim that Fmix comes chiefly from the undamaged fibers in carpal tunnel syndrome, and thus cannot replace Fmot or Fsen in the evaluation of retrograde axonal atrophy. Patients with clinical symptoms and signs of carpal tunnel syndrome confirmed with standard electrodiagnosis were included. Age-matched volunteers served as control subjects. Conduction velocities across the wrist and over the forearm were measured, including those of the wrist sensory (Wsen), wrist motor (Wmot), and wrist mixed nerves (Wmix); and forearm mixed (Fmix), forearm motor (Fmot), and forearm sensory nerves (Fsen). The authors compared and correlated Wsen, Wmot, and Wmix; and Fmix, Fmot, and Fsen respectively. The mean values of Wsen, Wmot, Wmix, Fmix, Fmot, and Fsen of the control subjects less those of corresponding conduction velocity of carpal tunnel syndrome patients were designated Wsen N, Wmot N, Wmix N, Fmix N, Fmot N, and Fsen N respectively and were compared and correlated again. Wrist motor nerve conduction velocity, Wsen, and Wmix were significantly lower in carpal tunnel syndrome patients, and Fmot and Fsen but not Fmix were reduced significantly when compared with control subjects. Mean wrist sensory nerve conduction velocity, Wmot N, and Wmix N; and Fsen N and Fmot N showed good correlation except for Fmix N, suggesting that Fmix reflects the conduction velocity of undamaged fibers in carpal tunnel syndrome. Forearm mixed nerve conduction velocity cannot replace Fmot or Fsen in the assessment of retrograde axonal atrophy in carpal tunnel syndrome. In the disease state, Fmix possibly represents the conduction velocity of the palmar cutaneous branch.     

Results of carpal tunnel release

We evaluated, by means of a prospective study, the results of carpal tunnel release both clinically and electrophysiologically in 188 patients with a carpal tunnel syndrome. A questionnaire was completed by patient and surgeon pre- and post-operatively (6 and 12 months after operation), when physical examination, electromyography and nerve conduction tests were also performed. Full pre- and post-operative results were available for 136 patients and 82% of the patients were satisfied with the results of the operation. Symptoms caused by median nerve compression showed the greatest improvement and no fixed patterns with regard to unsatisfactory results were found. If pain persisted in the wrist, many patients considered the operation to have been unsuccessful. Electrophysiological improvement occurred in all patients and at 12 months follow-up, median nerve conduction was normal in 21% of cases. Thus distal sensory latency remained abnormal in 79% of the patients, emphasizing the need for caution when recurrence of carpal tunnel syndrome is diagnosed in such cases.     

Ulnar nerve lesions associated with the carpal tunnel syndrome

Electrophysiological studies were performed on median and ulnar nerves in 234 cases of carpal tunnel syndrome. Abnormalities of the ulnar nerve sensory action potential were found in 39·3% of cases. The amplitude of the ulnar nerve sensory action potential was related to the amplitude of the median nerve sensory action potential, and to the median nerve motor conduction velocity in the forearm. The findings suggest that in a significant proportion of patients with carpal tunnel syndrome, a more generalized subclinical neuropathy may be present.