42 Original Paper

Does Ultrasonography Contribute Significantly to the Diagnosis of Carpal Tunnel Syndrome?

Authors

A. Zyluk, I. Walaszek, Z. Szlosser

Affiliation

Department of General and Hand Surgery, Pomeranian Medical University, Szczecin, Poland

Key words ▶ decompression ● ▶ carpal tunnel syndrome ● ▶ imaging procedures ● ▶ expertise ●

Abstract

Zusammenfassung

Background: Recent studies have demonstrated ultrasonography as a valuable tool for confirming the diagnosis of carpal tunnel syndrome. The objective of this study was to investigate sonographic parameters of the median nerve in patients diagnosed clinically with carpal tunnel syndrome. Patients and Methods: 185 wrists in 185 patients, 149 women (81 %) and 36 men (19 %), with a mean age of 59 years, with the clinical diagnosis of carpal tunnel syndrome were examined sonographically. We measured cross-sectional area (CSA) of the median nerve at the forearm and at the carpal tunnel inlet, as well as the height (a-p dimension) of the nerve at the tunnel inlet and in the narrowest site in the carpal tunnel. Moreover, in all patients the severity of the disease was assessed by the Levine questionnaire. Results: A significant variability of sonographic data characterizing the median nerve was found: the mean CSA at the tunnel inlet was 17.6 mm2 (range: 7–36) and height of the nerve at the tunnel inlet was a mean of 2.7 mm (range: 1.3–4.5). No correlation was found between sonographic data and severity of the syndrome as expressed by the Levine scores. Conclusion: Sonography of the median nerve contributes little to the diagnosis of a clinically relevant carpal tunnel syndrome and its routine use is not justified.

Hintergrund: Neuere Studien haben gezeigt, dass Ultraschall ein nützliches Verfahren für die Bestätigung der Diagnose des Karpaltunnelsyndroms ist. Ziel der vorliegenden Studie war, sonografische Parameter des Nervus medianus bei Patienten mit klinisch diagnostiziertem Karpaltunnelsyndrom zu ermitteln. Patienten und Methoden: 185 Handgelenke von 185 Patienten, darunter 149 Frauen (81 %) und 36 Männer (19 %), mit einem mittleren Alter von 59 Jahren, mit klinisch diagnostiziertem Karpaltunnelsyndrom wurden mittels Ultraschall untersucht. Gemessen wurde die Querschnittsfläche (CSA, cross-sectional area) des Nervus medianus am Unterarm und am Karpaltunneleingang sowie die Dicke (a-p Dimension) des Nervs am Tunneleingang und an der engsten Stelle des Karpaltunnels. Außerdem wurde bei allen Patienten der Schweregrad der Erkrankung mit Hilfe des Levine-Fragebogens untersucht. Ergebnisse: Die sonografischen Befunde des N. medianus bei diagnostiziertem Karpaltunnelsyndrom zeigen eine große Streubreite: der Querschnitt am Tunneleingang betrug im Mittel 17,6 (7–36) mm², die Dicke des Nervs am Tunneleingang lag im Mittel bei 2,7 (1,3– 4,5) mm. Es wurde keine Korrelation zwischen den sonografischen Daten und dem Schweregrad des Syndroms nach Levine-Score gefunden. Schlussfolgerung: Die Ultraschalluntersuchung des Nervus medianus trägt wenig zur Diagnose eines klinisch relevanten Karpaltunnelsyndroms bei. Der routinemäßige Einsatz ist daher nicht gerechtfertigt.

Introduction

signs and results of neurophysiological tests. Ultrasonography (abb. US) has had a relatively long (about 20 years) history in the diagnosis of carpal tunnel syndrome, but in the last decade

Schlüsselwörter ▶ Dekompression ● ▶ Karpaltunnelsyndrom ● ▶ Bildgebende Verfahren ● ▶ Expertise ●

received accepted

16.9.2013 19.11.2013

Bibliography DOI http://dx.doi.org/ 10.1055/s-0033-1363661 Handchir Mikrochir Plast Chir 2014; 46: 42–46 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0722-1819 Correspondence Andrzej Zyluk Department of General and Hand Surgery Pomeranian Medical University ul. Unii Lubelskiej 1 71-252 Szczecin Poland [email protected]





The diagnosis of carpal tunnel syndrome is based on the presence of typical clinical symptoms and



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Leistet Ultraschall einen signifikanten Beitrag zur Diagnose des Karpaltunnelsyndroms?

there has been growing interest in its use in the clinical routine. US is considered to be a valuable tool for confirming the diagnosis of carpal tunnel syndrome (abb. CTS) and, compared to neurophysiological studies, offers a simpler, quicker and cheaper way to assess the median nerve in the carpal tunnel [1–3]. Numerous studies have revealed that the most accurate sonographic parameter indicating the compression of the median nerve in the carpal tunnel is the cross-sectional area (abb. CSA) of the nerve at the inlet level [1–3]. However, there remains a lack of consensus regarding the most accurate CSA threshold (cut-off value) for establishing the diagnosis of CTS. Contrary to the nerve conduction studies, sonographic data show great variability of median nerve CSA both in healthy controls (from a mean of 4,8– 9,7 mm2) and in CTS patients (from a mean of 10,7 to 16,8 mm2). The cut-off values ranging from 9 to 12 mm2 have been proposed in a majority of the studies [4–7]. Sensitivity and specificity of US in diagnosing carpal tunnel syndrome (calculated for different cut-off values) varies from 60 to 90 % [4–7]. Difficulties in standardization of cross-sectional nerve area motivated investigators to search for other indicators of the nerve compression, e. g.,“wristforearm” ratio, flexor retinaculum bowing, “flattening” ratio, height of the nerve in the carpal tunnel, median nerve echogenicity or mobility on dynamic assessment, but none of them showed better accuracy in diagnosing CTS [1, 3, 8]. As the results of several studies are inconsistent with regard to the reliability of individual sonographic parameters and cut-off values for distinguishing physiology and pathology, we performed a prospective study to investigate sonographic parameters for characterizing the median nerve in patients diagnosed clinically with carpal tunnel syndrome. We aimed also to show a possible correlation between sonographic parameters of the median nerve and clinical severity of the disease as assessed by the Levine questionnaire.

The control group comprised 20 wrists of 20 volunteers, 15 women and 5 men, with the mean age of 45 years (range: 20–69), having no symptoms and signs of median nerve compression. Sonographic examination of the median nerve was only performed in these subjects. As the control group was small and not matched with the CTS patients, the results of measurements in this group were treated only illustratively. Each patient was examined 1 day before the operation and the measurements included US scanning of the median nerve and clinical examination. In patients with bilateral involvement only the wrist indicated for surgery was examined. Sonographic examination was performed by 2 hand surgeons, both trained in musculoskeletal sonography, with an 18 MHz linear array transducer (Esaote, Maastricht, The Netherlands). The examiner was blinded to the results of the clinical and electrophysiological (if done) examinations. Median nerve images were obtained and recorded at three levels: (i) at the forearm, at the proximal margin of the pronator quadratus muscle, (ii) at the carpal tunnel inlet, and (iii) in the narrowest site of the nerve in the carpal tunnel. At levels (i) and (ii), a cross-sectional area (abb. CSA) of the ▶ Fig. 1a, b). At levmedian nerve was measured (coronal plane, ● els (ii) and (iii) the height of the median nerve was measured ▶ Fig. 2a, b). The CSA at the tunnel inlet and at (sagittal plane, ●

Materials and Methods



Between 2009–2011, 349 patients, 279 women and 60 men, were admitted to the authors’ institution for carpal tunnel release. Of this number, 185 patients, 149 women (81 %) and 36 men (19 %), with a mean age of 59 (range: 27–88) years, with the disease lasting a mean of 58 (range: 3–370) months were examined sonographically. In 53 patients (29 %) the disease was unilateral, involving the right wrist in 38 and the left in 15, and 132 patients (71 %) had bilateral involvement. The diagnosis of carpal tunnel syndrome was made based on “classical” clinical history, ▶ Table 1). Electrodiagnostic studies were symptoms and signs (● additionally performed on 113 of 185 patients (61 %) for various reasons, confirming the diagnosis, but in 72 patients (39 %) the diagnosis was solely clinical. Results of nerve conduction studies were not included in this study, as this will be the subject of a separate report. Table 1 Typical for carpal tunnel syndrome constellation of symptoms and signs. Pain and numbness in the hand, which woken at night. Feeling of oedema of the digits Occurrence of these symptoms in digits/hand innervated by a median nerve Occurrence of these symptoms in the day, at manual work or static grip with flexed wrist Relief of symptoms after shaking or rubbing the hand Weaker grip, reduced dexterity of the hand

Fig. 1 a Coronal view of the median nerve (outlined) at the pronator quadratus level. Cross-sectional area of the nerve is 13 mm2. Proximal edge of the muscle is marked with an arrow. b Coronal view of the median nerve (outlined) at the carpal tunnel inlet. CSA of the nerve is 20 mm2. The hook of hamate is marked with an arrow.

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Original Paper 43

the distal forearm was calculated directly with the area measurement software of the US machine, after outlining of the shape of the nerve by the assessor. Clinical examinations included completion of the Levine questionnaire. The Levine questionnaire is a disease-specific measure consisting of 2 multi-item scales. The symptom severity scale consists of 11 items characterizing pain and numbness experienced by the patient. The functional status scale consists of 8 items reflecting difficulties in use of the hand in daily living. The answers are rated from 1 (no symptoms, no impairment) to 5 (severe symptoms, activity impossible to perform). The final score ranges in both scales are from 1 (no CTS) to 5 (extremely severe CTS) [8]. Quantitative data were expressed as the mean, median, range and standard deviation. The difference in sonographic parameters between patients and controls was assessed with the MannWhitney U test. The correlation between variables was analyzed with the Spearman rank test and a coefficient p < 0.05 was considered as indicating a significant difference.

Results



▶ Table 2 and Results of all measurements are shown in ● ▶ Table 3. The cross-sectional area of the median nerve at the ●

tunnel inlet differed significantly from the CSA at the forearm and the difference (ΔCSA) amounted a mean of 7.9 mm2 (range: − 4 to 28 mm2). The height of the median nerve at the tunnel inlet differed significantly from the narrowest site in the carpal tunnel and the difference (Δheight) amounted to 0.9 mm (range: − 0.8 to 2.9 mm). The ranges and SDs of all sonographic parameters in CTS patients were wide, suggesting their dispersed distribution. Comparing to the control group, the cross-sectional area and the height of the median nerve at the tunnel inlet were statistically significantly greater (Mann-Whitney U test, p < 0.001) in CTS patients. Likewise, the differences in the ΔCSA and Δheight were statistically significant between the patients and control group (p < 0.001). However, there were no significant differences between the groups in the CSA at the distal forearm and the height at the narrowest site in the tunnel. As we mentioned earlier, these calculations have only illustrative value. The Levine scores were calculated in the CTS patients, amounting to a mean of 3.2 for the symptom part, and a mean of 2.9 for ▶ Table 2). Using the the function part of the questionnaire (● Spearman rank test we calculated a correlation between all considered sonographic parameters of the median nerve and clinical severity of carpal tunnel syndrome as expressed by the Levine symptom and function scores. We found no correlation between these variables (each p > 0.5, each R < 0.2). In 5 cases (3 %), we found unexpected anomalies in the carpal tunnel such as a bifid median nerve in 2 patients, a ganglion cyst in another 2 and a median artery in one. These sonographic findings were confirmed intraoperatively. The results of the sonographic examination did not influence the decision-making about the operative treatment of the syndrome (in no patient was the operation cancelled).

Discussion



The objective of this study was to investigate sonographic parameters of the median nerve in the carpal tunnel in patients

Table 2 Results of sonographic measurements of the median nerve in 185 CTS patients. Variable

Mean

Range

Median

SD

CSA at the forearm mm2 CSA at the tunnel inlet mm2 Difference (ΔCSA) mm2 Height at the tunnel inlet mm The lowest tunnel height mm Difference (Δheight) mm Levine symptom score Levine function score

9.6 17.6 7.9 2.7 1.8 0.9 3.2 2.9

5–26 7–36 − 4–28 1.3–4.5 0.7–3.6 − 0.8–2.9 1.4–4.8 1.0–4.5

9 16 7 2.6 1.7 0.9 3.2 3.0

3.07 5.52 5.28 0.57 0.49 0.63 0.65 0.67

Table 3 Results of sonographic measurements of the median nerve in 20 healthy controls.

Fig. 2 a Saggital view of the median nerve (marked with + ) at the carpal tunnel inlet. The height of the nerve is 2.3 mm. b Saggital view of the median nerve (marked with + 1) at the narrowest site in the carpal tunnel. The height of the nerve is 1.8 mm. Saggital view of the flexor retinaculum is marked with + 2 (height 4.8 mm).

Variable

Mean

Range

CSA at the forearm mm2 CSA at the tunnel inlet mm2 Difference (ΔCSA) mm2 Height at the tunnel inlet mm The lowest tunnel height mm Difference (Δheight) mm

10.3 11.5 1.2 2.3 1.8 0.5

7–14 9–15 − 3–7 1.4–4.9 1.2–2.4 − 0.1–3.3

Zyluk A et al. Does Ultrasonography Contribute Significantly … Handchir Mikrochir Plast Chir 2014; 46: 42–46

Median 10.5 12 1 2.0 1.7 0.2

SD 1.79 1.79 2.23 0.75 0.38 0.72

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44 Original Paper

Original Paper 45

Author and year

Number of CTS patients

CSA (mean) mm2

CSA (range) mm2

CSA cut-off values for CTS mm2

Hobson-Webb 2008 Klauser 2009 Domanasiewicz 2009 Moran 2009 Karadag 2009 Pastare 2009 Visser 2009 Pinilla 2009 Hobson-Webb 2009 (USA) (Eur) This study

44 100 153 70 49 97 161 40 46 50 185

15.1 16.8 14.0 not stated 11.7–16.3 not stated not stated 10,1 15.4 11.9 17.6

not stated 11–22 9–19 not stated not stated not stated not stated 6–14 8–24 5–23 7–36

not stated 12 10 13 not stated 9 10 6,5 14 10 –

Author and year

Number of controls

CSA (mean) mm2

CSA (range) mm2

9.7 9.0 8.5 8.5 6.5 4.8

7–11 6–11 8–10 5–8 3,5–6

Hobson-Webb 2008 Klauser 2009 Domanasiewicz 2009 Karadag 2009 Pastare 2009 Pinilla 2009

18 93 50 50 18 30

Hobson-Webb 2009 (USA) (Eur) – the paper reports data from two separate laboratiories in the USA and in Italy

with carpal tunnel syndrome and to analyze the correlation between these parameters and clinical severity of the disease, as assessed by the Levine questionnaire. Our findings show a significant variability of sonographic data characterizing the median nerve. It concerns the CSA at the tunnel inlet, which has been shown to be the most reliable parameter indicating compression of the nerve, but also other parameters measured in ▶ Table 2). A comparison with the control group this study (● ▶ Table 3) illustrates a significant overlap between normal, (● physiological and pathological data. The sonographic measurements were performed in patients with established CTS diagnosis, and, therefore, the results were not considered in decision making about treatment of the patients. We aimed to investigate to which extent a sonographic examination may contribute to the diagnosis. Our findings show that ultrasonography of the median nerve provides no meaningful information for the diagnosis of and decision-making about the treatment of clinically relevant CTS. Moreover, we failed to show any relationship between sonographic parameters of the median nerve and clinical severity of the syndrome as expressed by the Levine scores. The major drawback of the sonographic examination is the great variability of dimensions of the median nerve, hence making it difficult determine a reliable cut-off level for distinguishing ▶ Table 4). This is probably because physiology and pathology (● of: (i) great individual variability in the median nerve dimensions, both normal and diseased, which may be related to the patients’ handiness’, sex, age, race, body mass or hand physiognomies (slim or strong wrists), (ii) technique of scanning, including different load, pressure and direction of the transducer applied to the wrist, different level of measurement, (iii) factors related to personal skills and habits of the operator, precision in marking the shape of the nerve, (iv) the equipment used. Unlike, e. g., nerve conduction studies, ultrasonography is a more subjective method of imaging, therefore results of meas▶ Table 2–4. Therefore urements vary significantly, as shown in ● it seems to be difficult to establish reliable cut-off values for the diagnosis of carpal tunnel syndrome. Sonography is an efficient technique to search for anatomic variations and space-occupy-

ing alterations such as tumours, abnormal vessels, muscles or synovial hypertrophy, but is less useful in quantitative assessment [2, 3]. There have been several ultrasonography studies dealing with the role of this imaging technique in the diagnosis of the CTS. Klauser et al. reported results of sonographic examination of 100 wrists in 68 CTS patients and 93 wrists in 58 healthy controls. They measured CSA of the median nerve (i) at the level of maximal nerve shape change from the proximal to the distal carpal tunnel and (ii) at the level of the proximal third of the pronator quadratus muscle. A difference between these variables (ΔCSA) was calculated for each wrist. Statistically significant differences were noted in CSA between patients and controls at the carpal tunnel level, at the distal forearm and in ΔCSA. The best diagnostic discrimination with a sensitivity of 94 % and a specificity of 95 % was noted by using a carpal tunnel CSA threshold of 12 mm2 and a ΔCSA threshold of 2 mm2 (sensitivity of 99 % and specificity of 100 %). Our results are in agreement with the measurements of these authors with regard to the CSA at the tunnel inlet and in ΔCSA, but the variability of data in our study was greater [1]. Pinilla et al. examined the median nerve CSA and a-p diameter in 30 wrists of 27 CTS patients and in 15 controls. They found statistically significant differences in these variables between patients and controls. A cut-off value of the CSA of 6.5 mm2 was found to be the most reliable with a sensitivity of 89 % and a specificity of 93 %. Our results are consistent with findings of these authors with regard to the median nerve height, but not to the CSA, which was significantly greater in our patients (17.6 mm2 vs. 10.1 mm2) [4]. Yazdchi et al. examined the median nerve CSA and flexor retinaculum thickness in 90 CTS patients. They measured CSA of the median nerve (i) at the level of carpal tunnel inlet, (ii) carpal tunnel outlet and (iii) immediately proximal to the carpal tunnel inlet. A cut-off value of the CSA of 12.5 mm2 was found to be the most useful, with a sensitivity of 71 % and a specificity of 59 % [6]. Karadag et al. reported results of the median nerve CSA in 99 wrists of 54 CTS patients. In contrast to our findings, these authors noted a significant relationship between the CSA and clinical severity of the CTS as expressed by the Levine scores [9].

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Table 4 Cross-section area values and cut-offs for patients and controls reported in the literature.

46 Original Paper Conflict of interest: None References 1 Klauser AS, Halpern EJ, de Zordo T et al. Carpal tunnel syndrome assessment with US: value of additional cross-sectional area measurements of the median nerve in patients and healthy volunteers. Radiology 2009; 250: 171–177 2 Seror P. Sonography and electrodiagnostics in carpal tunnel syndrome diagnosis, an analysis of literature. Eur Radiol 2008; 67: 146–152 3 Zyluk A, Puchalski P, Nawrot P. The usefulness of ultrasonography in the diagnosis of carpal tunel syndrome – a review. Chir Narz Ruchu Ortop Pol 2010; 75: 385–391 (English abstract) 4 Pinilla I, Martin-Hervas C, Sordo G et al. The usefulness of ultrasonography in the diagnosis of carpal tunnel syndrome. J Hand Surg Eur 2008; 33: 435–439 5 Moran L, Perez M, Esteban A et al. Sonographic measurement of crosssectional area of the median nerve in the diagnosis of carpal tunnel syndrome: correlation with nerve conduction studies. J Clin Ultrasound 2009; 37: 125–131 6 Yazdchi M, Terzemani KM, Mikaelli H et al. Sensitivity and specificity of median nerve ultrasonography in diagnosis of carpal tunnel syndrome. Int J Gen Med 2012; 5: 99–103 7 Pastare D, Therimadasamy AK, Lee E et al. Sonography versus nerve conduction studies in patients referred with clinical diagnosis of carpal tunnel syndrome. J Clin Ultrasound 2009; 37: 389–393 8 Levine DW, Simmons BP, Koris MJ et al. A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome. J Bone Joint Surg 1993; 75A: 1585–1592 9 Karadag YS, Karadag O, Cicekli E et al. Severity of carpal tunnel syndrome assessed with high frequency ultrasonography. Rheumatol Int 2010; 30: 761–765 10 Domanasiewicz A, Koszewicz M, Jabłecki J. Comparison of the diagnostic value of ultrasonography and neurography in carpal tunnel syndrome. Neurol Neurochir Pol 2009; 43: 433–438 11 Hobson-Webb LD, Massey JM, Juel VC et al. The ultrasonographic wrist to forearm median nerve area ratio in carpal tunnel syndrome. Clin Neurophysiol 2008; 119: 1353–1357 12 Hobson-Webb LD, Pauda L. Median nerve ultrasonography in carpal tunnel syndrome: findings from two laboratories. Muscle Nerve 2009; 40: 94–97 13 Visser LH, Smidt MH, Lee ML. Diagnostic value of wrist median nerve cross sectional area versus wrist to forearm ratio in carpal tunnel syndrome. Clin Neurpohysiol 2008; 119: 2896–2899 14 Zyluk A, Walaszek I, Szlosser Z. No correlation between sonographic and electrophysiological parameters in carpal tunnel syndrome. J Hand Surg 2013, Epub. doi:10.1177/1753193413489046

Andrzej Zyluk Age 57 years. Born in 1956 in Szczecin, Poland. Graduated in 1981 in Pomeranian Medical University in Szczecin, Poland. MD thesis in 1992, habilitation 1998 in Pomeranian Medical University in Szczecin, Poland. Head of the Department of General and Hand Surgery, Pomeranian Medical University in Szczecin, since 1999. Professor of Surgery, since 2004. President of Polish Society for Surgery of the Hand 2009–2013. Overseas member of British Society for Surgery of the Hand. Member of Editiorial Board of the Journal of Hand Surgery (European Volume), since 2004. Main topic of interest: hand surgery, CRSPS, carpal tunel syndrome.

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In our earlier study we investigated the correlation between between sonographic and electrophysiological parameters in patients diagnosed with carpal tunnel syndrome. One hundred and thirteen patients (113 wrists), 90 women and 23 men, with a mean age of 60 years, underwent sonographic and electrophysiological examinations. 55 patients (48 %) had mild, 43 (38 %) moderate and 12 (11 %) had severe conduction disturbances (3 patients had normal conduction). Sonographic measurements showed a cross-sectional area of the median nerve of 9.9 mm2 at the forearm and 17.8 mm2 at the tunnel inlet. The height of the nerve at the tunnel inlet was a mean of 2.7 mm, and the lowest height inside the tunnel was 1.8 mm. No correlation was found between sonographic and electrophysiological parameters [14]. Results of this study are – in general – consistent with findings from the present one. Our study has some limitations. First is that sonography was made by the surgeons but not by the radiologists. In fact, these surgeons were both trained in musculoskeletal sonography, hence having some skills in this technique at the beginning and developing them as time passed. Moreover, the sonography is suggested to be performed by the surgeons themselves, to reduce time and costs associated with referring patients to other specialists. Nevertheless, we cannot exclude operator-dependent biases in our sonographic data. The second is the small control group, not matched with the study one, hence we were unable to calculate sensitivity and specificity of the US. The third is using a clinical diagnosis of CTS as a reference for sonographic findings. This is because the general policy in our unit is to diagnose carpal tunnel syndrome on clinical grounds. The strong point is recruitment of a large number of patients as well as the clear and uniform methodology. The results of this study and review of the literature shown ▶ Table 4 lead us to the critical conclusion that sonography in ● cannot be considered a valuable tool in diagnosing carpal tunnel syndrome and its routine use in typical cases is not justified. We believe that a confident diagnosis of the condition can be made based on the history and clinical findings and that US contributes little to it. In doubtful cases, (atypical symptomatology, unclear course), nerve conduction studies provide significantly more information about the condition and function of the median nerve, the presence of more than one compression sites or other pathologies, than does ultrasonography.

Does ultrasonography contribute significantly to the diagnosis of carpal tunnel syndrome?

Recent studies have demonstrated ultrasonography as a valuable tool for confirming the diagnosis of carpal tunnel syndrome. The objective of this stud...
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