What symptoms are truly caused by median nerve compression in carpal tunnel syndrome?

OBJECTIVE: This study aims to identify the symptoms, signs and distributions which are associated with neurophysiological carpal tunnel syndrome (N-CTS), defined by the finding of a median nerve lesion at the wrist through neurophysiologic studies, and to compare them with those of patients with sensory or motor complaints in the upper limbs whose electrophysiologic investigation did not show evidence of this syndrome. METHODS: A cross-sectional study was performed, with prospective gathering of data, following a predetermined protocol. We included all patients older than 12 years who were referred for nerve conduction studies and electromyography of at least one of the upper limbs between August 2001 and January 2003. The patients answered a clinicoepidemiologic questionnaire and painted the areas in which they felt pain and those in which they felt paresthesia, and were also examined to test for classical signs CTS. RESULTS: A neurophysiological diagnosis of CTS was reached in 1549 upper limbs (39%). Approximately 6% of the upper limbs with N-CTS and 16% of those without median nerve lesion do not have any hand or wrist symptoms (P<0.001). Paresthesia, pain, hand weakness and cramps were the symptoms statistically associated to N-CTS, with paresthesia being the one with the greatest power of association. This is usually felt in median innervation's territory, and is frequently extended to the whole hand, but without association with N-CTS when felt in proximal region. CONCLUSIONS: One concludes that the most characteristic manifestation of carpal tunnel syndrome (CTS) is paresthesia. Pain also occurs very frequently but it is less specific, and weakness, meanwhile, seems to have a low frequency. We believe that the variability in the clinical presentation of CTS is largely due to the presence of associated diseases and our results provide information which could help to better define the clinical criteria used in the diagnosis of this syndrome.     

Symptoms of 100 patients with electromyographically verified carpal tunnel syndrome.

To determine the symptoms of carpal tunnel syndrome (CTS), screening evaluations were performed in 244 consecutive patients with sensory symptoms in the hand and unequivocal slowing of median nerve conduction at the wrist. This yielded 100 patients thought to have no explanation other than CTS for their upper limb complaints. These patients completed a hand symptom diagram (HSD) and questionnaire (HSQ) about their symptoms. CTS symptoms were most commonly reported in median and ulnar digits, followed by median digits only and a glove distribution. Unusual sensory patterns were reported by some patients. Based on the HSQ, paresthesias or pain proximal to the wrist occurred in 36.5% of hands. The usefulness of the HSD and HSQ for diagnosis was determined by asking three physicians, blinded to the diagnosis, to rate the likelihood of CTS in the patients with CTS and in 50 patients with other causes of upper extremity paresthesia. The sensitivities of the instruments ranged from 54.1% to 85.5%. Combining the HSD and HSQ ratings increased the range of sensitivities to 79.3% to 93.7%.     

Schwannoma of the median nerve (even outside the wrist) may mimic carpal tunnel syndrome

Abstract Over the last 3 years we have observed 5 cases of median nerve schwannoma that clinically simulated carpal tunnel syndrome (CTS). We describe the atypical clinical-neurophysiological picture indicating to perform ultrasonography (US). We retrospectively re-evaluated 5 cases of schwannoma that clinically simulated CTS. Five consecutive patients were referred to the neurophysiopathology laboratory. All patients complained of symptoms and had a neurophysiological examination that might have indicated CTS. Nevertheless we performed US because of some incongruous aspects. In cases of atypical abnormalities at neurophysiological and clinical examination, or dissociation between neurophysiological and clinical findings, physicians should consider the presence of a median nerve tumour. Here, US evaluation is very useful as supporting diagnostic methodology to assess the anatomopathological condition of the nerve lesion and must not be limited to the wrist.     

Proximal pain in patients with carpal tunnel syndrome: a clinical-neurophysiological study

Patients with carpal tunnel syndrome (CTS) usually complain of pain and paresthesia in the hand or wrist, but pain proximally to the wrist has been frequently reported in this condition. This study was aimed at understanding which clinical features are associated with the presence of proximal pain (PP) in the upper limb of CTS patients. We recruited 250 patients with clinical and neurophysiological evidence of CTS. After thorough selection to rule out concomitant upper limb painful conditions, 112 patients (175 hands) were included. PP was defined as the presence of pain in the upper limb proximally to the wrist (neck excluded) in association with sensory complaints in the hand. Patients were asked about the presence and severity of proximal sensory complaints, the distribution of sensory complaints in the hand, and underwent an objective evaluation and neurographic study. Thenar muscle strength was significantly larger, the neurophysiological measures were significantly less severe, and hand paresthesia was significantly greater in patients with PP. The neurographic score and the measures of median nerve damage were inversely correlated with the severity of PP. PP was related to extramedian spread of symptoms in the hand. None of the objective/neurographic variables was related to severity of sensory complaints restricted to the hand. PP may be found in a consistent number of CTS patients. PP may represent a clinical marker of mild median nerve damage. The presence of proximal complaints might be related to peripheral or central nervous system mechanisms.     

Carpal tunnel syndrome: ultrasound, neurophysiology, clinical and patient-oriented assessment

OBJECTIVE: The aim of this study is twofold. First, to assess the relationships between the cross-sectional area (CSA) of the median nerve (MN) calculated at ultrasound (US) and: (1) patient's perception of his/her symptoms and hand function; (2) clinical severity of CTS; (3) neurophysiological classification; (4) hand distribution of symptoms. Second, to assess the sensitivity of ultrasonography (US) and neurophysiology in the diagnosis of CTS using clinical measures as gold standard. METHODS: We performed a prospective study by using multidimensional assessment: clinical (Historic and Objective scale, Hi-Ob), neurophysiological, patient-oriented measures (Boston Carpal Tunnel Questionnaire, BCTQ) and high-resolution US. The dominant hands of 54 consecutive patients who were referred to our neurophysiologic laboratory with clinical signs of CTS (43 females, mean age 53.3, range 30-80, SD: 13.1) were examined. RESULTS: A statistically significant correlation was found between the CSA of the MN at wrist and (1) hand function (according to BCTQ, r=0.35, p=0.01), (2) clinical scale (Hi-Ob scale, r=0.51, p<0.00007), (3) neurophysiologic classification (r=0.80, p<0.0000001), and (4) hand distribution of symptoms (p=0.017). Neurophysiology showed higher sensitivity than US but in one of 3 cases with normal neurophysiological results, US showed data suggestive of CTS. CONCLUSIONS: A positive correlation exists between US findings and all the conventional measures of CTS severity. The sensitivity of the combination of US and neurophysiology is higher than the sensitivity of neurophysiology or US alone. US is a useful complementary tool for CTS assessment. SIGNIFICANCE: Information on the contribution of US in CTS and the interpretation of severity measurements in CTS.     

Carpal tunnel syndrome secondary to an osteophyte of the trapezium

We report a 42-year-old man with a rare carpal tunnel syndrome (CTS) secondary to an osteophyte of the trapezium. The patient presented with a 3-year history of CTS, consisting of progressive pain and paresthesias in his right hand, positive Tinel and Phalen signs, and an electrodiagnostic study demonstrating median nerve compression at the wrist. The procedure was an open carpal tunnel release. Intraoperatively, a bony protuberance was found beneath the transverse carpal ligament (TCL), resulting in compression of the median nerve. The median nerve was decompressed and the patient’s symptoms resolved postoperatively. Surgical pathology revealed bony fragments, and a postoperative CT scan was supportive of an osteophytic remnant protruding from the trapezium. Carpal bone osteophytes are rarely reported causes of CTS.     

The ultrasonographic wrist-to-forearm median nerve area ratio in carpal tunnel syndrome.

OBJECTIVE: Peripheral nerve ultrasound is an emerging tool in the diagnosis of carpal tunnel syndrome (CTS). Although numerous publications have cited an increased median nerve area at the wrist to be the diagnostic of CTS, there has been considerable variability in the published normal values for this measurement. Our objective is to collect data on the wrist-to-forearm ratio (WFR) of median nerve area in patients with CTS and healthy controls. METHODS: Patients with electrodiagnostically proven CTS underwent ultrasonography of the median nerve at the wrist and forearm. The median nerve area was measured at these points and compared to values from asymptomatic volunteers. RESULTS: The WFR of median nerve area in asymptomatic volunteers was 1.0+/-0.1. The WFR in patients presenting with CTS was 2.1+/-0.5. CONCLUSIONS: The WFR in patients with CTS is elevated as compared to asymptomatic controls. A WFR of 1.4 gave 100% sensitivity for detecting patients with CTS while using only median nerve area at the wrist resulted in a sensitivity of 45-93%, depending on the cut-off value used. SIGNIFICANCE: The WFR of median nerve area promises to be a valid means of diagnosing CTS, and may be superior to measuring median nerve area at the wrist alone.     

The median palmar cutaneous nerve in normal subjects and CTS.

OBJECTIVE: The neurophysiological confirmation of carpal tunnel syndrome (CTS) relies on detecting abnormal median nerve transcarpal conduction in the presence of unaffected comparator nerves. We compare the palmar cutaneous median branch (PCBm) with the ulnar sensory nerve conduction to digit 5 (US(5)) as comparator nerves for diagnosing CTS. METHODS: In a prospective case control study of patients with clinically defined carpal tunnel syndrome and normal subjects, we determined and compared the PCBm and US(5) conduction velocity. RESULTS: We examined 57 hands with clinically defined CTS and 59 control hands. Comparison showed highly significantly slowed PCBm conduction (p<0.0001) but not for US(5) conduction (p=0.488). Using a 3 percentile cut-off for abnormality derived from controls, PCBm conduction velocity was abnormal in 46% of CTS hands. CONCLUSIONS: The high frequency of PCBm nerve conduction abnormality in CTS suggests that this nerve should not be used as a comparator nerve for the neurophysiological diagnosis of CTS. This finding may help explain some of the extension of sensory symptoms outside the median nerve distribution in CTS. SIGNIFICANCE: In CTS frequent abnormality of PCBm conduction makes this a poor comparator nerve and may explain extension of sensory symptoms beyond the median nerve.     

Evidence of altered motor axon properties of the ulnar nerve in carpal tunnel syndrome.

OBJECTIVE: To analyse recruitment properties of ulnar nerve motor axons in 60 CTS patients with negative ulnar nerve electrodiagnostic tests. METHODS: Recruitment properties of the ulnar nerve were studied by analysing the relationship between the intensity of electrical stimulation and the size of motor response, i.e. the stimulus-response curve. Parameters of the curve (threshold, slope and plateau) were compared with those of the corresponding curve of the median nerve and both with parameters of 30 control curves. RESULTS: The ulnar nerve stimulus-response curve was strikingly abnormal and, except for severity, closely resembled that of the median nerve. The slope of the curve was significantly less than that of controls and decreased with increasing abnormalities of the median nerve. This suggested that the pathological process involving the ulnar nerve was contingent with the severity of median nerve involvement. CONCLUSIONS: We propose that the ulnar nerve may be subject to compression in Guyon's canal as a consequence of high pressure in the carpal tunnel of CTS patients. SIGNIFICANCE: Ectopic activity from ulnar axons may contribute to clinical spread of symptoms outside the median nerve territory in CTS. This does not exclude possible involvement of central plasticity mechanisms in producing extra-median symptoms in CTS patients.     

Lumbrical and interossei recording in carpal tunnel syndrome.

Median motor studies are commonly "normal" in mild carpal tunnel syndrome (CTS). This reflects either the sparing of motor compared to sensory fibers, or the inability of conventional studies to detect an abnormality. A novel approach to demonstrate early motor fiber involvement in CTS is the placement of the same active electrode lateral to the third metacarpal, allowing recording from the second lumbrical or the deeper interossei, when stimulating the median or ulnar nerves at the wrist, respectively. We compared the difference between these latencies in 51 normal control hands to 107 consecutive patient hands referred with symptoms and signs suggestive of CTS, who were subsequently proven to have electrophysiologic CTS by standard nerve conduction criteria. A prolonged lumbrical-interossei latency difference (> 0.4 ms) was found to be a sensitive indicator of CTS in all patient groups. It was also helpful in patients with coexistent polyneuropathy, where localization at the wrist was otherwise difficult.     

Ultrasonography in severe carpal tunnel syndrome

Introduction: In up to 30% of patients with carpal tunnel syndrome (CTS), the cross‐sectional area (CSA) of the median nerve may not be enlarged. We hypothesize that this could be the result of secondary atrophy of the nerve in severe CTS. The aim of this study was to measure the ultrasonographic CSA of the median nerve at the wrist in patients with severe CTS. Methods: In 14 consecutive patients with clinically and electrophysiologically defined severe CTS, the CSA of the median nerve was measured and compared with that of control subjects. Results: CSA of the median nerve exceeded the upper limit of normal in the majority of patients with severe CTS. Conclusions: Atrophy of the median nerve in severe CTS does not explain negative ultrasonographic test results. Instead, the CSA of the median nerve is enlarged in most patients with severe CTS. Muscle Nerve, 2012     

Ulnar nerve impairment at the wrist does not contribute to extramedian sensory symptoms in carpal tunnel syndrome

ObjectiveExtramedian spread of sensory symptoms is frequent in carpal tunnel syndrome (CTS) but its mechanisms are unclear. We explored the possible role of subtle ulnar nerve abnormalities in the pathogenesis of extramedian symptoms.MethodsWe recruited 350 CTS patients. After selection, 143 patients (225 hands) were included. The hand symptoms distribution was graded with a diagram into median (MED) and extramedian (EXTRAMED) pattern. We tested the correlation of ulnar nerve conduction measures with the distribution and the severity of symptoms involving the ulnar territory. The clinical significance of ulnar nerve conduction findings was explored with quantitative sensory testing (QST).ResultsEXTRAMED distribution was found in 38.7% of hands. The ulnar neurographic measures were within normal values. Ulnar nerve sensory measures were significantly better in EXTRAMED vs MED hands and not significantly correlated to ulnar symptoms severity. Ulnar and median nerve sensory measures were significantly correlated. QST showed normal function of ulnar nerve Aβ-fibers.ConclusionsUlnar nerve sensory abnormalities do not contribute to the spread of sensory symptoms into the ulnar territory.SignificanceOur data favour the hypothesis that spinal and supraspinal neuroplastic changes may underlie extramedian spread of symptoms in CTS.     

Clinical features of 1039 patients with neurophysiological diagnosis of carpal tunnel syndrome

PURPOSE: To describe the clinical features of patients with a neurophysiologic diagnosis of carpal tunnel syndrome (CTS) in the state of Rio Grande do Sul, Brazil. METHODS: We prospectively studied 1039 patients with a neurophysiologic diagnosis of CTS in southern Brazil. All patients completed a clinicoepidemiological questionnaire which included a drawing of the arm and hand, in which they were asked to paint the areas in which paresthesia and pain occurred. In part of the sample, we also investigated the presence of clinical signs such as Tinel's, Phalen, and tenar atrophy. The diagnosis of CTS was performed using a predetermined neurophysiological protocol. RESULTS: A total of 1528 hands were diagnosed with CTS. The severity of CTS was mild in 42% of cases, moderate in 18% and severe in 40%. Patients had a mean age of 48.3 +/- 12.4 years old, and a ratio of 5.6 females to 1 male was observed. Symptoms restricted to the hand and wrist was observed in 51.8% of cases with paresthesia and in 18.5% of cases with pain. In 92.5% of the partially affected hands, paresthesia was present in at least one of the first three fingers, while pain affected the three first fingers in 78.8% of these hands. Pain with a distribution which did not involve the hand occurred in 18.5% of cases, while paresthesia without involvement of the hand occurred in only 1.9%. Distribution of symptoms, according to Katz's hand diagram, showed a classic pattern in 12.6% of affected hands, a pattern classified as probable CTS in 66.3%, and an unlikely CTS pattern in 4.1%. Tinel's and Phalen's sign were observed in 34.2 and 56.3% of the hands, respectively. CONCLUSION: The clinical presentation of CTS is pleomorphic, ranging from the absence of symptoms to very severe cases. This variation probably is dependent on coexistent diseases, such as tendinitis and fibromyalgia, as well as on subjective aspects of the patients.     

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.     

Prediction of the neurophysiological diagnosis of carpal tunnel syndrome from the demographic and clinical data.

OBJECTIVE: To use demographic and clinical data to identify the clinical pattern that best predicts the diagnosis of carpal tunnel syndrome (CTS), as defined by neurophysiologic studies. METHODS: A diagnostic cross-sectional study in 2535 consecutive patients (3907 upper limbs) older than 12 years old who were referred for nerve conduction studies in the upper limbs between August 2001 and January 2003 in 3 university hospitals and 2 private neurophysiology services in the state of Rio Grande do Sul, Brazil. RESULTS: A neurophysiologic diagnosis of CTS was established in 39.1% of these upper limbs. The presence of paresthesias or pain at least 2 of the first 4 digits in association with one of the following: female gender, symptoms worsening at night or on awakening, an BMI > or =30, thenar atrophy, or other sign (Tinel's, Phalen's, or Reversed Phalen's signs); were the best pattern associated with the diagnosis. CONCLUSIONS: We have found that the clinical picture alone does not seem sufficient, in majority of the population, to correctly predict the diagnosis of CTS, as defined by median nerve neuropathy at the carpal tunnel. We believe that a compressive lesion of the median nerve at the carpal tunnel can be present both in patients with no typical symptoms of CTS (including asymptomatic individuals) and in patients in which neurophysiologic studies are negative. SIGNIFICANCE: Further studies separating patients into these groups will allow us to identify the long-term prognosis as well as the ideal therapeutic approach for each of these clinical situations.     

Peripheral autonomic involvement in the carpal tunnel syndrome

The sympathetic skin response (SSR), evoked from the middle finger of both hands by electrical stimuli to the median nerve (MN) at the wrist, was studied in 21 patients with bilateral carpal tunnel syndrome (CTS) and in 16 patients with monolateral CTS (14 at the right and 2 at the left side) without clinical signs of autonomic involvement. In monolateral and bilateral CTS there was a decrease in the SSR areas of both sides. In monolateral CTS the decrease was greater contralaterally to the lesion. A decrease in the SSR in CTS generally indicates a local blockade of sympathetic nerve excitability due to MN entrapment. Contralateral reduction of the sympathetic response suggests an involvement of the efferent pathway of the autonomic reflex far from the lesion at the wrist. However, dispersion of the excitement over a long distance and throughout numerous synaptic connections may affect contralateral more than homolateral SSR excitability. Finally, sympathetic damage in CTS is in accord with the anatomofunctional correlation (in the peripheral nerve and ganglia) between somatic sensory, which were most markedly involved in our patients, and sympathetic afferent nerve fibers.     

Sonography in carpal tunnel syndrome

Introduction: Our objective in this study was to assess the diagnostic utility of the median nerve cross‐sectional area (CSA) at the wrist, the wrist–forearm ratio, and the wrist–forearm difference in patients with and without carpal tunnel syndrome (CTS). Methods: Individuals with electrodiagnostically proven CTS and asymptomatic control subjects were recruited prospectively from among patients referred to our electrodiagnostic laboratory. Blinded measurements of CSA were made from transverse sonographic images of the median nerve at the wrist (pisiform) and mid‐forearm. Results: Fifty‐five cases and 49 controls were recruited. Wrist median nerve CSA (15 vs. 9 mm²; P < 0.0001), wrist–forearm ratio (3.09 vs. 1.90 mm²; P < 0.0001), and wrist–forearm difference (10 vs. 4 mm²; P < 0.0001) were all significantly larger in CTS cases (areas under the curve = 0.89, 0.82, and 0.88, respectively). Conclusions: Median nerve CSA at the carpal tunnel inlet and wrist–forearm difference provides the best discrimination between patients with CTS and controls according to receiver operator characteristic (ROC) analysis. Age, gender, height, weight, and wrist size have no effect on CSA. Muscle Nerve, 2011     

Early diagnosis of carpal tunnel syndrome: comparison of digit 1 with wrist and distoproximal ratio

Our objective in this study was to compare the sensitivity and specificity of the median sensory nerve conduction velocity (SNCV) from digit 1 to wrist with those of the distoproximal (D/P) ratio of the median SNCV from palm to digit 3/palm to wrist in the diagnosis of mild carpal tunnel syndrome (CTS) by using a receiver operating characteristic (ROC) curve. To achieve this objective, we studied prospectively (January 1997-October 1998) 370 patients referred for CTS. One hundred forty-two patients (38.4%) with moderate to severe CTS and 15 patients (4.1%) with multiple (> or = 3) compressive neuropathies in upper limbs with subclinical peripheral neuropathy were excluded. The remaining 213 patients (302 hands with mild CTS; 167 women; mean age, 50 y +/- 12 y) and 38 controls (71 hands; 25 women; mean age, 47 y +/- 13 y) had median and ulnar nerve conduction studies. ROC curves were constructed for median SNCV digit 1 to wrist and median SNCV D/P ratio from the patients' and controls' data. The median SNCV at < or = 45.9 m/s, corresponding to an optimal cutoff point on ROC curve, discriminated 89.5% of mild CTS from controls with specificity of 98.6%. The median D/P ratio at > or = 1.12, corresponding to an optimal cutoff point on ROC curve, discriminated 67.2% of mild CTS from controls with specificity of 97.2%. Of the 10.3% (31/302) of hands in which digit 1 to wrist was within normal limits at the selected optimal cutoff value (< or = 45.9 ms), 7% (21/302) had an abnormal D/P ratio (> or = 1.12), and 3.3% (10/302) had a normal electrophysiologic examination. The likelihood ratio (true-positive ratio to false-positive ratio, assessing the discriminative power of a test) of the median SNCV digit 1 to wrist, at an optimal point on ROC curve (63.9), was higher than that of the median SNCV D/P ratio (23.9, chi2 = 36.9, P < .001). These findings suggest that the median SNCV digit 1 to wrist is more sensitive than the median SNCV D/P ratio in the diagnosis of mild CTS.     

Exclusive electrophysiological motor involvement in carpal tunnel syndrome.

OBJECTIVE: To define the frequency of exclusive electrophysiological motor involvement in carpal tunnel syndrome (CTS). METHODS: We reviewed the electrophysiological studies of 2727 consecutive hands with typical symptoms and signs of CTS and at least one abnormal test of the following: median distal motor latency (DML), digit two sensory conduction velocity (D2-SCV), segmental D2-SCV from wrist to palm, median-ulnar sensory latency difference from ring finger stimulation. RESULTS: Thirty-one hands (1.2%) had prolonged median DML ( > 4.4 ms) with normal SCV ( > 48 m/s). In 17 of 31 hands, segmental D2-SCV from wrist to palm or median-ulnar latency difference from ring finger stimulation were also performed with normal results in 8 hands, demonstrating a true exclusive electrophysiological motor involvement. CONCLUSIONS: In CTS, exclusive electrophysiological involvement of median motor fibers is rare. It may be related to preferential compression of the intraneural motor fascicles clumped superficially in the most volar-radial nerve quadrant or, more probably, to the fact that the recurrent thenar branch may exit the carpal tunnel through a separate ligamentous tunnel within the transverse carpal ligament where it may be preferentially or selectively compressed.     

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 (r² = 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. Muscle Nerve, 2012