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ASSESSMENT OF OUTCOME OF CARPAL TUNNEL SYNDROME: A COMPARISON OF ELECTROPHYSIOLOGICAL FINDINGS AND A SELF-ADMINISTERED BOSTON QUESTIONNAIRE
ASSESSMENT OF OUTCOME OF CARPAL TUNNEL SYNDROME: A COMPARISON OF ELECTROPHYSIOLOGICAL FINDINGS AND A SELF-ADMINISTERED BOSTON QUESTIONNAIRE N. HEYBELI, S. KUTLUHAN, S. DEMIRCI, M. KERMAN and E. F. MUMCU From the Departments of Orthopaedics and Traumatology, Neurology and Neurosurgery, Su¨leyman Demirel University, School of Medicine, Isparta, Turkey
The relationship between nerve conduction studies and the self-administered Boston Questionnaire that measures the severity of symptoms and functional status in carpal tunnel syndrome was assessed in 44 patients with idiopathic carpal tunnel syndrome. The patients were examined preoperatively and 3 and 6 months postoperatively. Although both the clinical outcome and electrophysiological findings improved significantly after surgery, we observed no correlation between improvements in nerve conduction and the questionnaire scores. Journal of Hand Surgery (British and European Volume, 2002) 27B: 3: 259–264
INTRODUCTION
PATIENTS AND METHODS
Carpal tunnel syndrome is a frequent cause of disability (Ferry et al., 1998; Stevens et al., 1988). Although, the results of carpal tunnel release are generally regarded as satisfactory (Glowacki et al., 1996; Thurston and Lam, 1997), some patients still have unsatisfactory outcomes (Bland, 2001; Katz et al., 2001). Complications may occur after surgical procedures (Palmer and Toivonen, 1999), and reoperations may be required (Cobb et al., 1996). Several tools have been used to assess the outcome of carpal tunnel syndrome treatment. These include nerve conduction studies, symptom surveys, sensibility testing, pinch or grip strength measurement, complication rates, assessment of pain levels and dexterity, return to work, and functional capacity (Amadio et al., 1996). Nerve conduction studies have been used to diagnose carpal tunnel syndrome and evaluate the outcome of treatment. Some authors regard them as a standard part of assessment (AAEM Quality Assurance Committee, 1993; Corwin and Kasdan, 1998; Haig et al., 1999) though others believe that they are unnecessary (Braun and Jackson, 1994; Finsen and Russwurm, 2001). Some studies found no relationship between nerve conduction studies performed before and after treatment (Braun and Jackson, 1994; Concannon et al., 1997), and the nature or duration of preoperative symptoms and success of surgery (Longstaff et al., 2001). A uniform, cost-effective and easily administrable assessment tool is required for carpal tunnel syndrome. Some self-administered questionnaires have been developed, one of which is the Boston Questionnaire (Levine et al., 1993). In this study, we investigated whether changes in the symptomatic and functional outcome scores of the questionnaire after surgery correlated with changes in nerve conduction studies.
Patients and study design The local research ethics committee of our institution approved the study. Forty-four electrophysiologically confirmed carpal tunnel syndrome patients were entered into this prospective study over a 1-year period. All were evaluated preoperatively and 3 and 6 months postoperatively using both nerve conduction studies and the Boston Questionnaire. The patients were informed that nerve conduction studies would be repeated 3 and 6 months after surgery and informed consent was obtained for all follow-up examinations and evaluations. Patients with bilateral carpal tunnel syndrome were not included since the Boston Questionnaire scores may have been affected by symptoms in the contralateral hand. Patients with diabetes, connective tissue disorders and kidney or thyroid disease were excluded, as were patients who had undergone previous carpal tunnel syndrome surgery. The mean age of the patients was 48 (range, 33–66) years. Forty were women and four were men. Twentyfour of the operations were performed on the right hand and 20 on the left. Boston Questionnaire (Brigham and Women’s Hospital Carpal Tunnel Questionnaire) The Boston Questionnaire is self-administered and assesses the severity of symptoms and the functional status of carpal tunnel syndrome patients (Levine et al., 1993). The symptom severity scale consists of 11, and the functional status scale of eight, questions. Each question has a 1-to-5 scale, in which 1 indicates no symptom and 5 indicates the severe symptoms. The symptom severity scale assesses the symptoms with 259
260
respect to severity, frequency, time and type. The functional status scale assesses the affect of the carpal tunnel syndrome on daily living. The Boston Questionnaire had been translated into Turkish, and has been validated in a preliminary study (Heybeli et al., 2001).
Electrodiagnostic testing All studies were performed with the patient supine, at a room temperature of 251C, using a Nihon Kohden – Neuropack MEB 5504K (Tokyo, Japan). The filter band-pass was 2 Hz to 3 kHz for the motor studies and 20 Hz to 3 kHz for the sensory studies. The compound muscle action potential was recorded with surface electrodes over the abductor pollicis brevis and adductor digiti minimi muscles. The median and ulnar nerves were stimulated 8 cm proximal to the anodal electrode by a hand-held stimulator with a 2 cm inter-electrode distance. Stimulus duration was 0.2 ms, sweep speed was 2 ms/division and amplitude gain was 5 mV. Measurements were made with a tape measure. Sensory nerve action potentials were obtained antidromically and were recorded with ring electrodes placed at the proximal and distal interphalangeal joints. The distance between the stimulator and the recording electrode was 14 cm. Sweep speed was 2 ms/division and the gain was 10 mV. An average of ten responses for sensory and five responses for motor evaluation were obtained from each stimulation site. The amplitudes of the sensory nerve action potentials and compound muscle action potentials were measured from peak-to-peak and distal latency from the onset point. Concentric needle electromyographic investigations were performed to exclude other causes of the hand symptoms. The electrophysiological criterion used to diagnose carpal tunnel syndrome was a median-ulnar sensory distal latency difference of greater than 0.5 ms (Uncini et al., 1993). The limits of normal routinely used in our laboratory were as follows: a median distal motor latency from the wrist to abductor pollicis brevis 44.2 ms; median sensory conduction velocity o42 m/s; median sensory conduction velocity o40 m/s in the wrist-topalm segment. In addition to the numerical data obtained from the nerve conduction studies, the severity of the electrophysiological findings was classified on a 1to-5-severity scale, which separately evaluates motor and sensory conduction in the median nerve (Mondelli et al., 2000).
Statistical methods The paired t-test was used for comparison of the preand postoperative means for nerve conduction studies, and the non-parametric Wilcoxon test was used to assess the Boston Questionnaire and electrophysiological scale findings. The Spearman correlation test was used to
THE JOURNAL OF HAND SURGERY VOL. 27B No. 3 JUNE 2002
investigate the relationship between the Boston Questionnaire scale and the electrophysiological findings. RESULTS The symptom severity and functional status scale scores improved postoperatively. The Boston Questionnaire and electrophysiological scale scores and the nerve conduction parameters before and at 3 and 6 months after surgery are shown in Table 1, and comparisons of these measurements at these times are shown in Table 2. Boston Questionnaire At the 3-month follow-up, there was a mean decrease of 2.170.7 points in symptom severity scale, indicating a reduction in symptoms. Five patients had no residual symptoms. At the 6-month follow-up, ten patients had complete relief of symptoms, and 33 cases had only minimal residual symptoms (Fig 1). None of the patients had a 6-month symptom severity scale score which was worse than the preoperative or 3-month score. At the 3-month follow-up, all patients function had improved significantly, with a mean decrease of 1.871.0 points in the functional status scale (Fig 2). Both functional status and symptom severity scales were significantly improved (Po0.001) at the 3-month follow-up, and there was a further improvement in the functional status scale by the 6-month follow-up (Pr0.001). The symptom severity scale and functional status scale scores correlated well with each other and there was a strong correlation in the degree of improvement in both scales at the 3- and 6-month follow-ups (r ¼ 0.831, Po0.001 and r ¼ 0.579, Po0.001, respectively). Electrodiagnostic testing Nine patients had normal median sensory conduction velocities at the initial electrophysiological examination. An improvement was observed at the 3-month followup in all cases and 23 had normal sensory conduction velocities at this time. At the 6-month follow-up only 11 hands had slow sensory conduction velocities. Preoperatively, the median distal motor latency was normal in seven patients. At the 3-month follow-up 15 patients, and at the 6-month follow-up 18 patients, had normal distal motor latencies. Two patients, who had improved by 3 months, had delayed distal motor latencies at 6 months. There was a statistically significant (Po0.001) improvement in distal motor latency after surgery, and this occurred during the first 3 months. There was a significant improvement in both the motor and sensory electrophysiological scales at the 3month follow-up. Only the sensory score improved between the 3- and 6-month evaluations (Fig 3 a,b).
Preoperative Mean (SD) BQ Symptom Severity Score BQ Functional Status Score Electropyhsiological Motor Scale Electropyhsiological Sensory Scale
3.4 3.3 2.3 2.6
Median motor CV DL CMAPa Median sensory CV DL SNAPa
Third month Range
(0.7) (1.1) (0.8) (0.9)
Mean (SD)
1.6–4.7 1.1–4.8 1–4 1–4
1.3 1.5 1.6 1.7
Sixth month Range
(0.3) (0.4) (0.6) (0.8)
Mean (SD)
1.0–2.2 1.0–2.4 1–3 1–4
1.3 1.4 1.7 1.5
Range
(0.3) (0.3) (0.6) (0.6)
1.0–2.1 1.0–2.3 1–3 1–3
51.5 (3.1) 5.9 (1.4) 8.6 (5.4)
45.9–58.0 3.4–9.0 0.4–22.0
50.8 (4.7) 4.8 (0.9) 8.8 (4.2)
40.3–58.9 3.4–6.8 1.9–18.0
51.6 (4.1) 4.7 (1.0) 8.7 (4.1)
44.3–59.8 3.4–6.8 0.3–18.9
36.8 (6.1) 3.9 (0.6) 15.4 (12.1)
24.8–49.4 3.0–5.0 1.7–53.3
43.1 (5.8) 3.3 (0.5) 20.9 (15.2)
28.7–54.7 2.7–4.7 2.1–58.0
45.1 (5.6) 3.2 (0.5) 20.5 (17.7)
30.0–54.8 2.6–4.5 1.6–81.0
BQ: Boston Questionnaire; CI: 95% confidence limit; CMAPa: Compound muscle action potential amplitude (mV); CV: Conduction velocity (m/s); DL: Distal latency (ms); SD: Standard deviation; SNAPa: Sensory nerve action potential amplitude (mV).
OUTCOME ASSESSMENT AFTER CARPAL TUNNEL SURGERY
Table 1FThe means, standard deviations and ranges of the Boston Questionnaire scores, electrophysiological scales and nerve conduction parameters before and at 3 and 6 months after surgery
Table 2FThe differences between the Boston Questionnaire scores, electrophysiological scales and nerve conduction parameters at the pre-operative and 3 and 6-month assessments Preoperative versus third month Mean (SD)
CI-lower
CI-upper
Third month versus sixth month p
(0.7) (1.0) (0.7) (0.9)
1.8 1.5 0.4 0.6
2.3 2.1 0.8 1.2
o0.001 o0.001 o0.001 o0.001
Median motor CV DL CMAPa
0.7 (4.9) 1.1 (1.1) 0.2 (4.4)
0.8 0.7 1.5
2.2 1.4 1.2
NS o0.001 NS
Median sensory CV DL SNAPa
6.3 (5.8) 0.6 (0.5) 5.5 (11.9)
8.1 0.5 9.1
4.6 0.8 1.9
o0.001 o0.001 o0.01
BQ Symptom Severity Score BQ Functional Status Score Electropyhsiological Motor Scale Electropyhsiological Sensory Scale
2.1 1.8 0.6 0.9
Mean (SD)
CI-lower
CI-upper
Preoperative versus sixth month p
p
2.3 2.2 0.8 1.4
o0.001 o0.001 o0.001 o0.001
NS NS NS
0.0 (4.5) 1.2 (1.0) 0.1 (4.7)
1.4 0.9 1.6
1.4 1.4 1.3
NS o0.001 NS
o0.001 0.003 NS
8.3 (5.6) 0.7 (0.5) 5.2 (11.8)
10.0 0.5 8.8
6.6 0.9 1.6
o0.001 o0.001 o0.01
NS r0.001 NS o0.01
0.7 (3.1) 0.1 (0.7) 0.1 (3.0)
1.7 0.1 0.8
0.2 0.3 0.9
2.0 (2.7) 0.1 (0.2) 0.4 (12.2)
2.8 0.03 3.3
1.2 0.1 4.1
CI-upper
1.9 1.6 0.4 0.8
0.1 0.06 0.5 0.08
(0.2) (0.2) (0.7) (0.4)
CI-lower
(0.7) (1.0) (0.6) (0.9)
0.00 0.04 0.02 0.06
0.1 0.1 0.6 0.2
Mean (SD) 2.1 1.9 0.6 1.1
BQ: Boston Questionnaire; CI: 95% confidence limit; CMAPa: Compound muscle action potential amplitude (mV); CV: Conduction velocity (m/s); DL: Distal latency (ms); SD: Standard deviation; SNAPa: Sensory nerve action potential amplitude (mV). 261
262
THE JOURNAL OF HAND SURGERY VOL. 27B No. 3 JUNE 2002
Fig 1 Distribution of subjects according to symptom severity scale preoperatively and at 3 and 6 months postoperatively.
Fig 3 (a) Distribution of subjects according to motor conduction score preoperatively and at 3 and 6 months postoperatively. (b) Distribution of subjects according to sensory conduction score preoperatively and at 3 and 6 months postoperatively.
Fig 2 Distribution of subjects according to functional status scale preoperatively and at 3 and 6 months postoperatively.
The improvements in distal motor and sensory conduction after surgery did not correlate with the changes in the symptom severity and functional status scales. In addition, the improvements in the functional status scale and symptom severity scale scores did not correlate with the age of the patients or the electrophysiological scores.
DISCUSSION Although patients assess relief of symptoms and improvement in function, and physicians evaluate the results and outcome of carpal tunnel surgery with nerve conduction studies and clinical assessments, observer
bias is unavoidable with such methods, which are neither standardized nor reproducible. Self-administered questionnaires may eliminate bias and, though subjective, are standardized, reproducible and sensitive to clinical changes. The Boston Questionnaire, developed by Levine et al. (1993), is a condition-specific instrument which has been tested for reproducibility, coherence, validity and sensitivity to clinical changes. Nerve conduction studies, which were regarded as the gold standard for the diagnosis of carpal tunnel syndrome until recently, are now regarded as superfluous for both diagnosis and outcome assessment by some authors (Braun and Jackson, 1994; Finsen and Russwurm, 2001). Many have queried their value as a diagnostic tool or an outcome measure, finding either no or only a limited relationship between them and the patient’s clinical status or satisfaction after surgery (Braun and Jackson, 1994; Concannon et al., 1997; Glowacki et al., 1996; Redmond and Rivner, 1988).
OUTCOME ASSESSMENT AFTER CARPAL TUNNEL SURGERY
The goal of our study was to assess the relationship between nerve conduction studies and the Boston Questionnaire. We observed a significant improvement in both measures after surgery and the symptom severity and functional status scale scores correlated well with each other, though not with the nerve conduction study findings. This suggests that the Boston Questionnaire and nerve conduction studies measure different aspects of outcome. Surgical complications like scar tenderness or neuroma formation are not considered by nerve conduction studies, though are directly related to patient satisfaction and influence the functional score of the Boston Questionnaire. In our series, four of nine patients with poor nerve conduction study results at the 6-month follow-up were asymptomatic, and three of them had full function. Furthermore, ten of 12 patients whose electrophysiological studies returned to normal after surgery reported impaired function and nine had persistent symptoms. Our diagnostic criterion for carpal tunnel syndrome was a difference of greater than 0.5 ms between the median and ulnar nerve sensory distal latencies. The mean latency difference was 1.4 ms (3.92.5) preoperatively, and this improved to 0.7 ms (3.32.6) at the 3month follow-up. Based on this criterion, many hands did not regain normal conduction by the end of the follow-up. At the 3-month follow-up, 27 hands still had median to ulnar sensory distal latency differences of greater than 0.5 ms, and only two of these 27 had further improvement in this parameter. However, most of these 27 cases had good clinical outcomes, which leads us to conclude that electrophysiological parameters take much longer than the symptoms and functional status of the patients to return to normal, or alternatively sometimes never return to normal. The variability between symptoms and nerve conduction study findings suggests that the decreased nerve conduction threshold required for symptom production varies from person to person. Identifying factors that predict the outcome of carpal tunnel release may be much more complex than generally assumed; for instance, ‘‘involvement of an attorney’’ has recently been implicated (Katz et al., 2001). These authors also reported that worse scores on patient-reported measures of upper extremity functional limitation, worse mental status and alcohol use were also significantly associated with greater postoperative functional limitation, more severe postoperative symptoms and lower satisfaction. Another interesting result was that the preoperative clinical signs did not predict the outcome of surgery. Dudley Porras et al. (2000) assessed a series of carpal tunnel syndrome patients before and 6 months after surgery using both the Boston Questionnaire and electrodiagnostic testing. They recommended the sensory nerve conduction velocity as ‘‘an objective way of measuring the post-operative outcome as it had a significant relationship with the improvement in clinical impairment of the patient’’. However these authors did not report any positive
263
correlation between sensory nerve conduction velocity and the Boston Questionnaire scores. Our results confirm the findings of Mondelli et al. (2000) who also found no correlation between electrophysiological and Boston Questionnaire findings. We agree with these authors that the assessment of clinical symptoms is a good measure in outcome of carpal tunnel syndrome and thus recommend the use of the Boston Questionnaire for audit and research purposes. It does not seem wise to advocate the use of Boston Questionnaire in the diagnosis of carpal tunnel syndrome, as the scales of the instrument measure symptoms and functional disabilities that can be caused by other neuropathies or upperextremity disorders. Clearly, our study has limitations as it only investigated of a small group of patients and several different surgeons performed the operations. However, the study was prospective and the patients were carefully selected to exclude bias and were assessed with standard electrodiagnostic methods and a standard questionnaire.
References AAEM Quality Assurance Committee, Jablecki CK, Andary MT, So YT, Wilkins DE, Williams FH (1993). Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. Muscle and Nerve, 16: 1392–1414. Amadio PC, Silverstein MD, Ilstrup DM, Schleck CD, Jensen LM (1996). Outcome assessment for carpal tunnel surgery: the relative responsiveness of generic, arthritis-specific, disease-specific, and physical examination measures. Journal of Hand Surgery, 21A: 338–346. Bland JDP (2001). Do nerve conduction studies predict the outcome of carpal tunnel decompression? Muscle and Nerve, 24: 935–940. Braun RM, Jackson WJ (1994). Electrical studies as a prognostic factor in the surgical treatment of carpal tunnel syndrome. Journal of Hand Surgery, 19A: 893–900. Cobb TK, Amadio PC, Leatherwood DF, Schleck CD, Ilstrup DM (1996). Outcome of reoperation for carpal tunnel syndrome. Journal of Hand Surgery, 21A: 347–356. Concannon MJ, Gainor B, Petroski GF, Puckett CL (1997). The predictive value of electrodiagnostic studies in carpal tunnel syndrome. Plastic and Reconstructive Surgery, 100: 1452–1458. Corwin HM, Kasdan ML (1998). Electrodiagnostic reports of median neuropathy at the wrist. Journal of Hand Surgery, 23A: 55–57. Dudley Porras AF, Rojo Alaminos P,Vin˘uales JI, Ruiz Villaman˘an MA (2000). Value of electrodiagnostic tests in carpal tunnel syndrome. Journal of Hand Surgery, 25B: 361–365. Ferry S, Pritchard T, Keenan J, Croft P, Silman AJ (1998). Estimating the prevalence of delayed median nerve conduction in the general population. British Journal of Rheumatology, 37: 630–635. Finsen V, Russwurm H (2001). Neurophysiology not required before surgery for typical carpal tunnel syndrome. Journal of Hand Surgery, 26B: 61–64. Glowacki KA, Breen CJ, Sachar K, Weiss APC (1996). Electrodiagnostic testing and carpal tunnel release outcome. Journal of Hand Surgery, 21A: 117– 122. Haig AJ, Tzeng HM, LeBreck DB (1999). The value of electrodiagnostic consultation for patients with upper extremity nerve complaints: a prospective comparison with the history and physical examination. Archives of Physical Medicine and Rehabilitation, 80: 1273–1281. Heybeli N, O¨zerdemog˘lu RA, Aksoy OG, Mumcu EF (2001). Functional and symptomatic scoring used for the assessment of outcome in carpal tunnel release. Acta Orthopaedica et Traumatologica Turcica, 35: 147–151. Katz JN, Losina E, Amick BJ, Fossel AH, Bessette L, Keller RB (2001). Predictors of outcome of carpal tunnel release. Arthritis and Rheumatism, 44: 1184–1193. Levine DW, Simmons BP, Koris MJ, et al. (1993). A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome. Journal of Bone and Joint Surgery, 75A: 1585–1592.
264 Longstaff L, Milner RH, O’Sullivan S, Fawcett P (2001). Carpal tunnel syndrome: the correlation between outcome, symptoms and nerve conduction study findings. Journal of Hand Surgery, 26B: 475–480. Mondelli M, Reale F, Sicurelli F, Padua L (2000). Relationship between the selfadministered Boston questionnaire and electrophysiological findings in follow-up of surgically-treated carpal tunnel syndrome. Journal of Hand Surgery, 25B: 128–134. Palmer AK, Toivonen DA (1999). Complications of endoscopic and open carpal tunnel release. Journal of Hand Surgery, 24A: 561–565. Redmond MD, Rivner MH (1988). False positive electrodiagnostic tests in carpal tunnel syndrome. Muscle and Nerve, 11: 511–517. Stevens JC, Sun S, Beard CM, O’Fallon WM, Kurland LT (1988). Carpal tunnel syndrome in Rochester, Minnesota, 1961 to 1980. Neurology, 38: 134–138.
THE JOURNAL OF HAND SURGERY VOL. 27B No. 3 JUNE 2002 Thurston A, Lam N (1997). Results of open carpal tunnel release: a comprehensive, retrospective study of 188 hands. Australian and New Zealand Journal of Surgery, 67: 283–288. Uncini A, Di Muzio A, Awad J, Manente G, Tafuro M, Gambi D (1993). Sensitivity of three median-to-ulnar comparative tests in diagnosis of mild carpal tunnel syndrome. Muscle and Nerve; 16: 1366–1373. Received: 7 September 2001 Accepted after revision: 30 January 2002 Dr. Nurettin Heybeli, Posta kutusu (P.K) 128, Isparta, Turkey. E-mail: [email protected] r 2002 The British Society for Surgery of the Hand doi: 10.1054/jhsb.2002.0762, available online at http://www.idealibrary.com on
The relationship between nerve conduction studies and the self-administered Boston Questionnaire that measures the severity of symptoms and functional status in carpal tunnel syndrome was assessed in 44 patients with idiopathic carpal tunnel syndrome. The patients were examined preoperatively and 3 and 6 months postoperatively. Although both the clinical outcome and electrophysiological findings improved significantly after surgery, we observed no correlation between improvements in nerve conduction and the questionnaire scores. Journal of Hand Surgery (British and European Volume, 2002) 27B: 3: 259–264
INTRODUCTION
PATIENTS AND METHODS
Carpal tunnel syndrome is a frequent cause of disability (Ferry et al., 1998; Stevens et al., 1988). Although, the results of carpal tunnel release are generally regarded as satisfactory (Glowacki et al., 1996; Thurston and Lam, 1997), some patients still have unsatisfactory outcomes (Bland, 2001; Katz et al., 2001). Complications may occur after surgical procedures (Palmer and Toivonen, 1999), and reoperations may be required (Cobb et al., 1996). Several tools have been used to assess the outcome of carpal tunnel syndrome treatment. These include nerve conduction studies, symptom surveys, sensibility testing, pinch or grip strength measurement, complication rates, assessment of pain levels and dexterity, return to work, and functional capacity (Amadio et al., 1996). Nerve conduction studies have been used to diagnose carpal tunnel syndrome and evaluate the outcome of treatment. Some authors regard them as a standard part of assessment (AAEM Quality Assurance Committee, 1993; Corwin and Kasdan, 1998; Haig et al., 1999) though others believe that they are unnecessary (Braun and Jackson, 1994; Finsen and Russwurm, 2001). Some studies found no relationship between nerve conduction studies performed before and after treatment (Braun and Jackson, 1994; Concannon et al., 1997), and the nature or duration of preoperative symptoms and success of surgery (Longstaff et al., 2001). A uniform, cost-effective and easily administrable assessment tool is required for carpal tunnel syndrome. Some self-administered questionnaires have been developed, one of which is the Boston Questionnaire (Levine et al., 1993). In this study, we investigated whether changes in the symptomatic and functional outcome scores of the questionnaire after surgery correlated with changes in nerve conduction studies.
Patients and study design The local research ethics committee of our institution approved the study. Forty-four electrophysiologically confirmed carpal tunnel syndrome patients were entered into this prospective study over a 1-year period. All were evaluated preoperatively and 3 and 6 months postoperatively using both nerve conduction studies and the Boston Questionnaire. The patients were informed that nerve conduction studies would be repeated 3 and 6 months after surgery and informed consent was obtained for all follow-up examinations and evaluations. Patients with bilateral carpal tunnel syndrome were not included since the Boston Questionnaire scores may have been affected by symptoms in the contralateral hand. Patients with diabetes, connective tissue disorders and kidney or thyroid disease were excluded, as were patients who had undergone previous carpal tunnel syndrome surgery. The mean age of the patients was 48 (range, 33–66) years. Forty were women and four were men. Twentyfour of the operations were performed on the right hand and 20 on the left. Boston Questionnaire (Brigham and Women’s Hospital Carpal Tunnel Questionnaire) The Boston Questionnaire is self-administered and assesses the severity of symptoms and the functional status of carpal tunnel syndrome patients (Levine et al., 1993). The symptom severity scale consists of 11, and the functional status scale of eight, questions. Each question has a 1-to-5 scale, in which 1 indicates no symptom and 5 indicates the severe symptoms. The symptom severity scale assesses the symptoms with 259
260
respect to severity, frequency, time and type. The functional status scale assesses the affect of the carpal tunnel syndrome on daily living. The Boston Questionnaire had been translated into Turkish, and has been validated in a preliminary study (Heybeli et al., 2001).
Electrodiagnostic testing All studies were performed with the patient supine, at a room temperature of 251C, using a Nihon Kohden – Neuropack MEB 5504K (Tokyo, Japan). The filter band-pass was 2 Hz to 3 kHz for the motor studies and 20 Hz to 3 kHz for the sensory studies. The compound muscle action potential was recorded with surface electrodes over the abductor pollicis brevis and adductor digiti minimi muscles. The median and ulnar nerves were stimulated 8 cm proximal to the anodal electrode by a hand-held stimulator with a 2 cm inter-electrode distance. Stimulus duration was 0.2 ms, sweep speed was 2 ms/division and amplitude gain was 5 mV. Measurements were made with a tape measure. Sensory nerve action potentials were obtained antidromically and were recorded with ring electrodes placed at the proximal and distal interphalangeal joints. The distance between the stimulator and the recording electrode was 14 cm. Sweep speed was 2 ms/division and the gain was 10 mV. An average of ten responses for sensory and five responses for motor evaluation were obtained from each stimulation site. The amplitudes of the sensory nerve action potentials and compound muscle action potentials were measured from peak-to-peak and distal latency from the onset point. Concentric needle electromyographic investigations were performed to exclude other causes of the hand symptoms. The electrophysiological criterion used to diagnose carpal tunnel syndrome was a median-ulnar sensory distal latency difference of greater than 0.5 ms (Uncini et al., 1993). The limits of normal routinely used in our laboratory were as follows: a median distal motor latency from the wrist to abductor pollicis brevis 44.2 ms; median sensory conduction velocity o42 m/s; median sensory conduction velocity o40 m/s in the wrist-topalm segment. In addition to the numerical data obtained from the nerve conduction studies, the severity of the electrophysiological findings was classified on a 1to-5-severity scale, which separately evaluates motor and sensory conduction in the median nerve (Mondelli et al., 2000).
Statistical methods The paired t-test was used for comparison of the preand postoperative means for nerve conduction studies, and the non-parametric Wilcoxon test was used to assess the Boston Questionnaire and electrophysiological scale findings. The Spearman correlation test was used to
THE JOURNAL OF HAND SURGERY VOL. 27B No. 3 JUNE 2002
investigate the relationship between the Boston Questionnaire scale and the electrophysiological findings. RESULTS The symptom severity and functional status scale scores improved postoperatively. The Boston Questionnaire and electrophysiological scale scores and the nerve conduction parameters before and at 3 and 6 months after surgery are shown in Table 1, and comparisons of these measurements at these times are shown in Table 2. Boston Questionnaire At the 3-month follow-up, there was a mean decrease of 2.170.7 points in symptom severity scale, indicating a reduction in symptoms. Five patients had no residual symptoms. At the 6-month follow-up, ten patients had complete relief of symptoms, and 33 cases had only minimal residual symptoms (Fig 1). None of the patients had a 6-month symptom severity scale score which was worse than the preoperative or 3-month score. At the 3-month follow-up, all patients function had improved significantly, with a mean decrease of 1.871.0 points in the functional status scale (Fig 2). Both functional status and symptom severity scales were significantly improved (Po0.001) at the 3-month follow-up, and there was a further improvement in the functional status scale by the 6-month follow-up (Pr0.001). The symptom severity scale and functional status scale scores correlated well with each other and there was a strong correlation in the degree of improvement in both scales at the 3- and 6-month follow-ups (r ¼ 0.831, Po0.001 and r ¼ 0.579, Po0.001, respectively). Electrodiagnostic testing Nine patients had normal median sensory conduction velocities at the initial electrophysiological examination. An improvement was observed at the 3-month followup in all cases and 23 had normal sensory conduction velocities at this time. At the 6-month follow-up only 11 hands had slow sensory conduction velocities. Preoperatively, the median distal motor latency was normal in seven patients. At the 3-month follow-up 15 patients, and at the 6-month follow-up 18 patients, had normal distal motor latencies. Two patients, who had improved by 3 months, had delayed distal motor latencies at 6 months. There was a statistically significant (Po0.001) improvement in distal motor latency after surgery, and this occurred during the first 3 months. There was a significant improvement in both the motor and sensory electrophysiological scales at the 3month follow-up. Only the sensory score improved between the 3- and 6-month evaluations (Fig 3 a,b).
Preoperative Mean (SD) BQ Symptom Severity Score BQ Functional Status Score Electropyhsiological Motor Scale Electropyhsiological Sensory Scale
3.4 3.3 2.3 2.6
Median motor CV DL CMAPa Median sensory CV DL SNAPa
Third month Range
(0.7) (1.1) (0.8) (0.9)
Mean (SD)
1.6–4.7 1.1–4.8 1–4 1–4
1.3 1.5 1.6 1.7
Sixth month Range
(0.3) (0.4) (0.6) (0.8)
Mean (SD)
1.0–2.2 1.0–2.4 1–3 1–4
1.3 1.4 1.7 1.5
Range
(0.3) (0.3) (0.6) (0.6)
1.0–2.1 1.0–2.3 1–3 1–3
51.5 (3.1) 5.9 (1.4) 8.6 (5.4)
45.9–58.0 3.4–9.0 0.4–22.0
50.8 (4.7) 4.8 (0.9) 8.8 (4.2)
40.3–58.9 3.4–6.8 1.9–18.0
51.6 (4.1) 4.7 (1.0) 8.7 (4.1)
44.3–59.8 3.4–6.8 0.3–18.9
36.8 (6.1) 3.9 (0.6) 15.4 (12.1)
24.8–49.4 3.0–5.0 1.7–53.3
43.1 (5.8) 3.3 (0.5) 20.9 (15.2)
28.7–54.7 2.7–4.7 2.1–58.0
45.1 (5.6) 3.2 (0.5) 20.5 (17.7)
30.0–54.8 2.6–4.5 1.6–81.0
BQ: Boston Questionnaire; CI: 95% confidence limit; CMAPa: Compound muscle action potential amplitude (mV); CV: Conduction velocity (m/s); DL: Distal latency (ms); SD: Standard deviation; SNAPa: Sensory nerve action potential amplitude (mV).
OUTCOME ASSESSMENT AFTER CARPAL TUNNEL SURGERY
Table 1FThe means, standard deviations and ranges of the Boston Questionnaire scores, electrophysiological scales and nerve conduction parameters before and at 3 and 6 months after surgery
Table 2FThe differences between the Boston Questionnaire scores, electrophysiological scales and nerve conduction parameters at the pre-operative and 3 and 6-month assessments Preoperative versus third month Mean (SD)
CI-lower
CI-upper
Third month versus sixth month p
(0.7) (1.0) (0.7) (0.9)
1.8 1.5 0.4 0.6
2.3 2.1 0.8 1.2
o0.001 o0.001 o0.001 o0.001
Median motor CV DL CMAPa
0.7 (4.9) 1.1 (1.1) 0.2 (4.4)
0.8 0.7 1.5
2.2 1.4 1.2
NS o0.001 NS
Median sensory CV DL SNAPa
6.3 (5.8) 0.6 (0.5) 5.5 (11.9)
8.1 0.5 9.1
4.6 0.8 1.9
o0.001 o0.001 o0.01
BQ Symptom Severity Score BQ Functional Status Score Electropyhsiological Motor Scale Electropyhsiological Sensory Scale
2.1 1.8 0.6 0.9
Mean (SD)
CI-lower
CI-upper
Preoperative versus sixth month p
p
2.3 2.2 0.8 1.4
o0.001 o0.001 o0.001 o0.001
NS NS NS
0.0 (4.5) 1.2 (1.0) 0.1 (4.7)
1.4 0.9 1.6
1.4 1.4 1.3
NS o0.001 NS
o0.001 0.003 NS
8.3 (5.6) 0.7 (0.5) 5.2 (11.8)
10.0 0.5 8.8
6.6 0.9 1.6
o0.001 o0.001 o0.01
NS r0.001 NS o0.01
0.7 (3.1) 0.1 (0.7) 0.1 (3.0)
1.7 0.1 0.8
0.2 0.3 0.9
2.0 (2.7) 0.1 (0.2) 0.4 (12.2)
2.8 0.03 3.3
1.2 0.1 4.1
CI-upper
1.9 1.6 0.4 0.8
0.1 0.06 0.5 0.08
(0.2) (0.2) (0.7) (0.4)
CI-lower
(0.7) (1.0) (0.6) (0.9)
0.00 0.04 0.02 0.06
0.1 0.1 0.6 0.2
Mean (SD) 2.1 1.9 0.6 1.1
BQ: Boston Questionnaire; CI: 95% confidence limit; CMAPa: Compound muscle action potential amplitude (mV); CV: Conduction velocity (m/s); DL: Distal latency (ms); SD: Standard deviation; SNAPa: Sensory nerve action potential amplitude (mV). 261
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THE JOURNAL OF HAND SURGERY VOL. 27B No. 3 JUNE 2002
Fig 1 Distribution of subjects according to symptom severity scale preoperatively and at 3 and 6 months postoperatively.
Fig 3 (a) Distribution of subjects according to motor conduction score preoperatively and at 3 and 6 months postoperatively. (b) Distribution of subjects according to sensory conduction score preoperatively and at 3 and 6 months postoperatively.
Fig 2 Distribution of subjects according to functional status scale preoperatively and at 3 and 6 months postoperatively.
The improvements in distal motor and sensory conduction after surgery did not correlate with the changes in the symptom severity and functional status scales. In addition, the improvements in the functional status scale and symptom severity scale scores did not correlate with the age of the patients or the electrophysiological scores.
DISCUSSION Although patients assess relief of symptoms and improvement in function, and physicians evaluate the results and outcome of carpal tunnel surgery with nerve conduction studies and clinical assessments, observer
bias is unavoidable with such methods, which are neither standardized nor reproducible. Self-administered questionnaires may eliminate bias and, though subjective, are standardized, reproducible and sensitive to clinical changes. The Boston Questionnaire, developed by Levine et al. (1993), is a condition-specific instrument which has been tested for reproducibility, coherence, validity and sensitivity to clinical changes. Nerve conduction studies, which were regarded as the gold standard for the diagnosis of carpal tunnel syndrome until recently, are now regarded as superfluous for both diagnosis and outcome assessment by some authors (Braun and Jackson, 1994; Finsen and Russwurm, 2001). Many have queried their value as a diagnostic tool or an outcome measure, finding either no or only a limited relationship between them and the patient’s clinical status or satisfaction after surgery (Braun and Jackson, 1994; Concannon et al., 1997; Glowacki et al., 1996; Redmond and Rivner, 1988).
OUTCOME ASSESSMENT AFTER CARPAL TUNNEL SURGERY
The goal of our study was to assess the relationship between nerve conduction studies and the Boston Questionnaire. We observed a significant improvement in both measures after surgery and the symptom severity and functional status scale scores correlated well with each other, though not with the nerve conduction study findings. This suggests that the Boston Questionnaire and nerve conduction studies measure different aspects of outcome. Surgical complications like scar tenderness or neuroma formation are not considered by nerve conduction studies, though are directly related to patient satisfaction and influence the functional score of the Boston Questionnaire. In our series, four of nine patients with poor nerve conduction study results at the 6-month follow-up were asymptomatic, and three of them had full function. Furthermore, ten of 12 patients whose electrophysiological studies returned to normal after surgery reported impaired function and nine had persistent symptoms. Our diagnostic criterion for carpal tunnel syndrome was a difference of greater than 0.5 ms between the median and ulnar nerve sensory distal latencies. The mean latency difference was 1.4 ms (3.92.5) preoperatively, and this improved to 0.7 ms (3.32.6) at the 3month follow-up. Based on this criterion, many hands did not regain normal conduction by the end of the follow-up. At the 3-month follow-up, 27 hands still had median to ulnar sensory distal latency differences of greater than 0.5 ms, and only two of these 27 had further improvement in this parameter. However, most of these 27 cases had good clinical outcomes, which leads us to conclude that electrophysiological parameters take much longer than the symptoms and functional status of the patients to return to normal, or alternatively sometimes never return to normal. The variability between symptoms and nerve conduction study findings suggests that the decreased nerve conduction threshold required for symptom production varies from person to person. Identifying factors that predict the outcome of carpal tunnel release may be much more complex than generally assumed; for instance, ‘‘involvement of an attorney’’ has recently been implicated (Katz et al., 2001). These authors also reported that worse scores on patient-reported measures of upper extremity functional limitation, worse mental status and alcohol use were also significantly associated with greater postoperative functional limitation, more severe postoperative symptoms and lower satisfaction. Another interesting result was that the preoperative clinical signs did not predict the outcome of surgery. Dudley Porras et al. (2000) assessed a series of carpal tunnel syndrome patients before and 6 months after surgery using both the Boston Questionnaire and electrodiagnostic testing. They recommended the sensory nerve conduction velocity as ‘‘an objective way of measuring the post-operative outcome as it had a significant relationship with the improvement in clinical impairment of the patient’’. However these authors did not report any positive
263
correlation between sensory nerve conduction velocity and the Boston Questionnaire scores. Our results confirm the findings of Mondelli et al. (2000) who also found no correlation between electrophysiological and Boston Questionnaire findings. We agree with these authors that the assessment of clinical symptoms is a good measure in outcome of carpal tunnel syndrome and thus recommend the use of the Boston Questionnaire for audit and research purposes. It does not seem wise to advocate the use of Boston Questionnaire in the diagnosis of carpal tunnel syndrome, as the scales of the instrument measure symptoms and functional disabilities that can be caused by other neuropathies or upperextremity disorders. Clearly, our study has limitations as it only investigated of a small group of patients and several different surgeons performed the operations. However, the study was prospective and the patients were carefully selected to exclude bias and were assessed with standard electrodiagnostic methods and a standard questionnaire.
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THE JOURNAL OF HAND SURGERY VOL. 27B No. 3 JUNE 2002 Thurston A, Lam N (1997). Results of open carpal tunnel release: a comprehensive, retrospective study of 188 hands. Australian and New Zealand Journal of Surgery, 67: 283–288. Uncini A, Di Muzio A, Awad J, Manente G, Tafuro M, Gambi D (1993). Sensitivity of three median-to-ulnar comparative tests in diagnosis of mild carpal tunnel syndrome. Muscle and Nerve; 16: 1366–1373. Received: 7 September 2001 Accepted after revision: 30 January 2002 Dr. Nurettin Heybeli, Posta kutusu (P.K) 128, Isparta, Turkey. E-mail: [email protected] r 2002 The British Society for Surgery of the Hand doi: 10.1054/jhsb.2002.0762, available online at http://www.idealibrary.com on