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CARPAL TUNNEL SYNDROME: THE CORRELATION BETWEEN OUTCOME, SYMPTOMS AND NERVE CONDUCTION STUDY FINDINGS
CARPAL TUNNEL SYNDROME: THE CORRELATION BETWEEN OUTCOME, SYMPTOMS AND NERVE CONDUCTION STUDY FINDINGS L. LONGSTAFF, R. H. MILNER, S. O’SULLIVAN and P. FAWCETT From the Department of Plastic Surgery, Royal Victoria Infirmary, Newcastle upon Tyne, UK
A retrospective study was performed on 62 patients who had undergone carpal tunnel decompression surgery. Each patient was assessed in clinic, their case notes were reviewed and their electrophysiological results were analysed and graded according to severity. The median preoperative duration of symptoms was 2 years. No relationship was found between the nature or duration of pre-operative symptoms and the severity of the electrophysiological impairment. Furthermore, no relationship could be identified between pre-operative nerve conduction impairment and either successful outcome of surgery (defined as complete symptom relief) or time to resolution of symptoms after surgery. Journal of Hand Surgery (British and European Volume, 2001) 26B: 5: 475–480 invited to attend a special assessment clinic where they were assessed by the first author. At this clinic additional information was obtained on the nature and duration of the pre-operative symptoms and the outcome after surgery, and each patient was examined for residual signs. Satisfaction with the surgical outcome was assessed using a visual analogue scale. The patient was also asked the direct question ‘‘Are you happy with the results of surgery?’’ to which the answer ‘‘yes’’ or ‘‘no’’ was requested. Of the 150 patients in the series 100 attended this clinic, of whom 62 had undergone electrophysiological tests: it is these 62 that formed the basis of this study.
INTRODUCTION Carpal tunnel syndrome is the most common compression neuropathy of the upper limb. Diagnosis is usually made on the basis of the history and a clinical examination with the additional help of electrophysiological tests. There is wide variation in the extent to which nerve conduction studies are used in clinical practice. BuchJaeger et al. (1994) performed a prospective study on 112 patients with clinical evidence of carpal tunnel syndrome and found positive nerve conduction studies in only 61% of cases. This differs from an earlier study in which it was found that 8% of symptomatic patients had normal nerve conduction studies (Grundberg et al., 1983). Concannon et al. (1997) studied patients with a clinical diagnosis of carpal tunnel syndrome and compared those with positive and negative electrophysiological findings. They demonstrated no difference between the groups for the presence of symptoms and signs, or the outcome following surgery. Padua et al. (1999) performed a large multicentre study which compared the findings on clinical examination with neurophysiological data and the results of a patient-orientated assessment. They observed that symptoms and pain scores decreased in patients with extreme neurophysiological impairment. We have undertaken a study to evaluate the relationship between pre-operative symptoms, electrophysiological tests and outcome after carpal tunnel decompression surgery.
Electrophysiological tests The electrophysiological tests were performed according to a set protocol. Sensory nerve conduction studies were performed using an orthodromic technique with sensory electrodes stimulating the first, third and fifth digits and recording electrodes at the wrist. Latency and peakto-peak amplitude were measured. Motor conduction studies were performed with bipolar surface stimulating electrodes proximal to the carpal tunnel and recording electrodes over the abductor pollicis brevis muscle. Motor latency was measured to the onset of the compound muscle action potential (CMAP). The peak-to-peak amplitude of the CMAP was measured. The nerve conduction studies of each patient were analyzed and graded according to severity. The criteria for categorizing the severity of the carpal tunnel syndrome are illustrated in Table 1. There is no universally accepted grading system for carpal tunnel syndrome and this one is based on a number of established theories (Graham et al., 1983). In the majority of cases, the sensory fibres are affected more than the motor fibres and sensory conduction velocity abnormalities occur earlier than prolongation of the distal motor latency (Kimura et al., 1985). A decrease in
PATIENTS AND METHODS This study was undertaken using a consecutive series of 150 patients who underwent carpal tunnel decompression surgery at the Royal Victoria Infirmary, Newcastle upon Tyne between June 1998 and June 1999. A review of the case notes revealed patient details, pre-operative findings and operative details. Each patient was then 475
476
THE JOURNAL OF HAND SURGERY VOL. 26B No. 5 OCTOBER 2001
Table 1—Classification of nerve conduction study results Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Grade 5 Grade 6
No detectable abnormality Very mild Mild (sensory conduction velocity540 m/sec, motor terminal latency54.5 msec) Moderately severe (motor terminal latency44.5 msec56.5 msec, preserved sensory potential) Severe (motor terminal latency44.5 msec, absent sensory potential) Very severe (motor terminal latency44.5 msec56.5 msec) Extremely severe (compound motor potential from abductor pollicis brevis50.2 mV)
the sensory nerve action potential amplitude occurs earlier in carpal tunnel syndrome than a decrease in the compound muscle action potential (Graham et al., 1983; Stevens, 1987). It is also assumed that techniques that assess sensory nerve conduction velocity over a short distance (e.g. palm-wrist) are superior to those that use a longer distance (AAEM Quality Assurance Committee, 1993). Our categories are based on the published data of Bland (2000), whose neurophysiological severity scale correlates well with clinical severity.
and both pre-operative symptom duration and postoperative time to loss of symptoms after surgery.
RESULTS Sixty two patients attended for review at the special assessment clinic. All had undergone preoperative nerve conduction studies, and all underwent carpal tunnel decompression surgery at the Royal Victoria Infirmary between June 1998 and June 1999. Thirty five were women, 27 were men. Thirty-three were right handed. Six were diabetics and four were dysthyroid. The median duration of symptoms was 2 years (interquartile range, 1–4 years). Figure 1 illustrates the relative frequency of pre-operative symptoms amongst the 62 patients. The nerve conduction results, classified according to grade of severity, are illustrated in Table 2. Most patients had a result within the middle range of values. There was only a poor correlation between symptom duration and the severity of electrophysiological abnormality (correlation coefficient ¼ +0.24: Figure 2). There was no relationship between the presence of pain (P ¼ 0.498: Figure 3) or the presence of reduced digital
The operation All patients underwent carpal tunnel decompression surgery as day cases. The operations were performed under local anaesthetic with a high arm tourniquet. 29 patients had the operation on the left, 33 on the right. Statistical analysis w2 tests were performed to investigate the relationship between pre-operative symptomatology and the severity of electrophysiological impairment. Correlation coefficients were calculated to investigate the relationship between the severity of electrophysiological impairment
Fig 1 Frequency of pre-operative symptom duration in 62 patients.
Table 2—Nerve conduction study results (graded according to severity, scale 0 to 6) and number of patients in each grade who obtained complete symptom resolution after surgery Electrophysiological grade Grade Grade Grade Grade Grade Grade Grade
0 1 2 3 4 5 6
Number of patients at each grade
Number of patients with complete loss of symptoms after surgery
4 18 8 15 8 5 4
2 8 5 8 5 4 0
CARPAL TUNNEL SYNDROME
477
Fig 2 The correlation between the nerve conduction study result and pre-operative symptom duration.
Fig 3 Distribution of symptoms (pain and sensory loss) between the different grades of electrophysiological abnormality.
sensation (P ¼ 0.063: Figure 3) and the severity of the electrophysiological impairment. Furthermore, there was no relationship between the presence of constant paraesthesiae (P ¼ 0.709: Figure 4) or the presence of weakness (P ¼ 0.471: Figure 4) and the severity of electrophysiological impairment. Fifty one percent of patients reported complete relief of their symptoms after the operation and 46% reported partial relief. Sixty percent of patients reported the immediate loss of their symptoms.
The median time to full resolution of carpal tunnel syndrome symptoms after surgery was 0 days (interquartile range, 0–2 months). There was a poor correlation between the severity of the pre-operative nerve conduction impairment and time to loss of symptoms after surgery (correlation coefficient ¼ 70.02: Figure 5). None of the four patients with grade six neurophysiological severity obtained complete resolution of their symptoms but there was no statistical relationship between complete symptom resolution and the other
478
THE JOURNAL OF HAND SURGERY VOL. 26B No. 5 OCTOBER 2001
Fig 4 Distribution of symptoms (weakness and constant sensory symptoms) between the different grades of electrophysiological abnormality.
Fig 5 The correlation between severity of nerve conduction study findings and time to complete symptom resolution after surgery.
grades of severity of nerve conduction impairment (P ¼ 0.314: Table 2). Complications were few following surgery (Figure 6). There was one wound infection, one patient with palmar paraesthesiae (due to damage to the palmar cutaneous branch of the median nerve), and eight patients with problematic scar tenderness persisting for more than 6 months. Six patients complained of pillar pain and three of weakness postoperatively. Each of these symptoms resolved within 3 months in all cases.
Most patients expressed moderate to high levels of satisfaction after surgery (median visual analogue score ¼ 80, interquartile range, 72–94). Eighty-six per cent of patients reported that they were happy with the results of the operation.
DISCUSSION Carpal tunnel syndrome decompression surgery is safe and effective. Ninety seven percent of patients had
CARPAL TUNNEL SYNDROME
479
Fig 6 Complications after carpal tunnel surgery.
complete or partial relief of their symptoms and 60% of patients reported immediate relief of their paraesthesiae postoperatively. No relationship was observed between the type of symptom experienced and the severity of the electrophysiological abnormality. The median duration of symptoms before surgery was 2 years, and one might expect that the more prolonged the symptom duration, the more severe the electrophysiological impairment encountered. However, our results would suggest that no such relationship exists and there was also no relationship between the severity of the carpal tunnel syndrome (as indicated by electrophysiological testing) and the outcome after surgery. With the exception of the four patients with extremely severe electrophysiological abnormality, all of whom did not recover fully, the patients with the more severe grades of abnormality did just as well as those with moderate grades of nerve conduction impairment. Additionally, we found no relationship between the severity of the preoperative electrophysiological abnormality and the time to postoperative recovery and relief of symptoms. This is surprising as increased pressure within the carpal tunnel is thought to lead to occlusion of intraneural vessels leading to ischaemia (Sunderland, 1976) When this compression is released, the pressure is relieved and so the circulation improves (Rydevic et al., 1981), which corresponds with the rapid improvement in symptoms seen in most patients after surgery. If compression is chronic, ischaemia is followed by intrafascicular oedema (Lundborg et al., 1983), fibroblast infiltration and scar formation (Sunderland, 1976). One would expect that the more chronic the condition, the more axonal damage would occur leading to a greater electrophysiological
impairment and a less successful and slower recovery after surgery. Clearly, our study has limitations, especially as it is retrospective in nature. Although the electrophysiological tests were performed in a uniform manner, they were not performed by one individual and a number of different surgeons, with different levels of expertise, performed the operations. On this basis, it would be unwise to make emphatic conclusions from the data. Nonetheless, this study has revealed some interesting results and will form the basis for a larger prospective controlled trial in which we will rigorously assess the role of electrophysiological tests in the management and prediction of outcome of carpal tunnel syndrome. Acknowledgements No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
References AAEM Quality assurance committee (1993). Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. Muscle & Nerve, 16: 1392–1414. Bland JDP (2000). A neurophysiological grading scale of carpal tunnel syndrome. Muscle & Nerve, 23: 1280–1283. Buch-Jaeger N, Foucher G (1994). Correlation of clinical signs with nerve conduction tests in the diagnosis of carpal tunnel syndrome. Journal of Hand Surgery, 19B: 6: 720–724. Concannon MJ, Gainor B, Petroski G, Puckett C (1997). The predictive value of electrodiagnostic studies in carpal tunnel syndrome. Plastic and Reconstructive Surgery, 100: 6: 1452–1458. Graham RA (1983). Carpal tunnel syndrome: a statistical analysis of 214 cases. Orthopaedics, 66: 1283. Grundberg AB (1983). Carpal tunnel decompression in spite of normal electromyography. Journal of Hand Surgery, 8: 348–349. Kimura I, Ayyar DR (1985). Carpal tunnel syndrome: electrophysiological aspects of 639 symptomatic extremities. Electromyography & Clinical Neurophysiology, 25: 151.
480 Lundborg G, Myers R, Powell H (1983). Nerve compression injury and increased endoneural fluid pressure: A ‘‘miniature compression syndrome.’’ Journal of Neurology, Neurosurgery & Psychiatry, 46: 1119– 1124. Padua I, Padua R, Aprile I, Tonali P (1999). Italian multicentre study of carpal tunnel syndrome. Differences in the clinical and neurophysiological features between male and female patients. Journal of Hand Surgery, 24B: 5: 579–582. Rydevic B, Lundborg G, Bagge U (1981). Effects of graded compression on intraneural blood flow. An in vivo study on rabbit tibial nerve. Journal of Hand Surgery, 6: 3–12. Stevens JC (1987). The electrodiagnosis of Carpal Tunnel Syndrome. Muscle & Nerve, 10: 99.
THE JOURNAL OF HAND SURGERY VOL. 26B No. 5 OCTOBER 2001 Sunderland S (1976). The nerve lesion of carpal tunnel syndrome. Journal of Neurology, Neurosurgery & Psychiatry, 39: 615–626.
Received: 15 December 2000 Accepted after revision: 6 April 2001 Mr L. Longstaff, 2 Woodbine Road, Gosforth, Newcastle upon Tyne NE3 1DD UK. E-mail: [email protected] # 2001 The British Society for Surgery of the Hand doi: 10.1054/jhsb.2001.0616, available online at http://www.idealibrary.com on
A retrospective study was performed on 62 patients who had undergone carpal tunnel decompression surgery. Each patient was assessed in clinic, their case notes were reviewed and their electrophysiological results were analysed and graded according to severity. The median preoperative duration of symptoms was 2 years. No relationship was found between the nature or duration of pre-operative symptoms and the severity of the electrophysiological impairment. Furthermore, no relationship could be identified between pre-operative nerve conduction impairment and either successful outcome of surgery (defined as complete symptom relief) or time to resolution of symptoms after surgery. Journal of Hand Surgery (British and European Volume, 2001) 26B: 5: 475–480 invited to attend a special assessment clinic where they were assessed by the first author. At this clinic additional information was obtained on the nature and duration of the pre-operative symptoms and the outcome after surgery, and each patient was examined for residual signs. Satisfaction with the surgical outcome was assessed using a visual analogue scale. The patient was also asked the direct question ‘‘Are you happy with the results of surgery?’’ to which the answer ‘‘yes’’ or ‘‘no’’ was requested. Of the 150 patients in the series 100 attended this clinic, of whom 62 had undergone electrophysiological tests: it is these 62 that formed the basis of this study.
INTRODUCTION Carpal tunnel syndrome is the most common compression neuropathy of the upper limb. Diagnosis is usually made on the basis of the history and a clinical examination with the additional help of electrophysiological tests. There is wide variation in the extent to which nerve conduction studies are used in clinical practice. BuchJaeger et al. (1994) performed a prospective study on 112 patients with clinical evidence of carpal tunnel syndrome and found positive nerve conduction studies in only 61% of cases. This differs from an earlier study in which it was found that 8% of symptomatic patients had normal nerve conduction studies (Grundberg et al., 1983). Concannon et al. (1997) studied patients with a clinical diagnosis of carpal tunnel syndrome and compared those with positive and negative electrophysiological findings. They demonstrated no difference between the groups for the presence of symptoms and signs, or the outcome following surgery. Padua et al. (1999) performed a large multicentre study which compared the findings on clinical examination with neurophysiological data and the results of a patient-orientated assessment. They observed that symptoms and pain scores decreased in patients with extreme neurophysiological impairment. We have undertaken a study to evaluate the relationship between pre-operative symptoms, electrophysiological tests and outcome after carpal tunnel decompression surgery.
Electrophysiological tests The electrophysiological tests were performed according to a set protocol. Sensory nerve conduction studies were performed using an orthodromic technique with sensory electrodes stimulating the first, third and fifth digits and recording electrodes at the wrist. Latency and peakto-peak amplitude were measured. Motor conduction studies were performed with bipolar surface stimulating electrodes proximal to the carpal tunnel and recording electrodes over the abductor pollicis brevis muscle. Motor latency was measured to the onset of the compound muscle action potential (CMAP). The peak-to-peak amplitude of the CMAP was measured. The nerve conduction studies of each patient were analyzed and graded according to severity. The criteria for categorizing the severity of the carpal tunnel syndrome are illustrated in Table 1. There is no universally accepted grading system for carpal tunnel syndrome and this one is based on a number of established theories (Graham et al., 1983). In the majority of cases, the sensory fibres are affected more than the motor fibres and sensory conduction velocity abnormalities occur earlier than prolongation of the distal motor latency (Kimura et al., 1985). A decrease in
PATIENTS AND METHODS This study was undertaken using a consecutive series of 150 patients who underwent carpal tunnel decompression surgery at the Royal Victoria Infirmary, Newcastle upon Tyne between June 1998 and June 1999. A review of the case notes revealed patient details, pre-operative findings and operative details. Each patient was then 475
476
THE JOURNAL OF HAND SURGERY VOL. 26B No. 5 OCTOBER 2001
Table 1—Classification of nerve conduction study results Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Grade 5 Grade 6
No detectable abnormality Very mild Mild (sensory conduction velocity540 m/sec, motor terminal latency54.5 msec) Moderately severe (motor terminal latency44.5 msec56.5 msec, preserved sensory potential) Severe (motor terminal latency44.5 msec, absent sensory potential) Very severe (motor terminal latency44.5 msec56.5 msec) Extremely severe (compound motor potential from abductor pollicis brevis50.2 mV)
the sensory nerve action potential amplitude occurs earlier in carpal tunnel syndrome than a decrease in the compound muscle action potential (Graham et al., 1983; Stevens, 1987). It is also assumed that techniques that assess sensory nerve conduction velocity over a short distance (e.g. palm-wrist) are superior to those that use a longer distance (AAEM Quality Assurance Committee, 1993). Our categories are based on the published data of Bland (2000), whose neurophysiological severity scale correlates well with clinical severity.
and both pre-operative symptom duration and postoperative time to loss of symptoms after surgery.
RESULTS Sixty two patients attended for review at the special assessment clinic. All had undergone preoperative nerve conduction studies, and all underwent carpal tunnel decompression surgery at the Royal Victoria Infirmary between June 1998 and June 1999. Thirty five were women, 27 were men. Thirty-three were right handed. Six were diabetics and four were dysthyroid. The median duration of symptoms was 2 years (interquartile range, 1–4 years). Figure 1 illustrates the relative frequency of pre-operative symptoms amongst the 62 patients. The nerve conduction results, classified according to grade of severity, are illustrated in Table 2. Most patients had a result within the middle range of values. There was only a poor correlation between symptom duration and the severity of electrophysiological abnormality (correlation coefficient ¼ +0.24: Figure 2). There was no relationship between the presence of pain (P ¼ 0.498: Figure 3) or the presence of reduced digital
The operation All patients underwent carpal tunnel decompression surgery as day cases. The operations were performed under local anaesthetic with a high arm tourniquet. 29 patients had the operation on the left, 33 on the right. Statistical analysis w2 tests were performed to investigate the relationship between pre-operative symptomatology and the severity of electrophysiological impairment. Correlation coefficients were calculated to investigate the relationship between the severity of electrophysiological impairment
Fig 1 Frequency of pre-operative symptom duration in 62 patients.
Table 2—Nerve conduction study results (graded according to severity, scale 0 to 6) and number of patients in each grade who obtained complete symptom resolution after surgery Electrophysiological grade Grade Grade Grade Grade Grade Grade Grade
0 1 2 3 4 5 6
Number of patients at each grade
Number of patients with complete loss of symptoms after surgery
4 18 8 15 8 5 4
2 8 5 8 5 4 0
CARPAL TUNNEL SYNDROME
477
Fig 2 The correlation between the nerve conduction study result and pre-operative symptom duration.
Fig 3 Distribution of symptoms (pain and sensory loss) between the different grades of electrophysiological abnormality.
sensation (P ¼ 0.063: Figure 3) and the severity of the electrophysiological impairment. Furthermore, there was no relationship between the presence of constant paraesthesiae (P ¼ 0.709: Figure 4) or the presence of weakness (P ¼ 0.471: Figure 4) and the severity of electrophysiological impairment. Fifty one percent of patients reported complete relief of their symptoms after the operation and 46% reported partial relief. Sixty percent of patients reported the immediate loss of their symptoms.
The median time to full resolution of carpal tunnel syndrome symptoms after surgery was 0 days (interquartile range, 0–2 months). There was a poor correlation between the severity of the pre-operative nerve conduction impairment and time to loss of symptoms after surgery (correlation coefficient ¼ 70.02: Figure 5). None of the four patients with grade six neurophysiological severity obtained complete resolution of their symptoms but there was no statistical relationship between complete symptom resolution and the other
478
THE JOURNAL OF HAND SURGERY VOL. 26B No. 5 OCTOBER 2001
Fig 4 Distribution of symptoms (weakness and constant sensory symptoms) between the different grades of electrophysiological abnormality.
Fig 5 The correlation between severity of nerve conduction study findings and time to complete symptom resolution after surgery.
grades of severity of nerve conduction impairment (P ¼ 0.314: Table 2). Complications were few following surgery (Figure 6). There was one wound infection, one patient with palmar paraesthesiae (due to damage to the palmar cutaneous branch of the median nerve), and eight patients with problematic scar tenderness persisting for more than 6 months. Six patients complained of pillar pain and three of weakness postoperatively. Each of these symptoms resolved within 3 months in all cases.
Most patients expressed moderate to high levels of satisfaction after surgery (median visual analogue score ¼ 80, interquartile range, 72–94). Eighty-six per cent of patients reported that they were happy with the results of the operation.
DISCUSSION Carpal tunnel syndrome decompression surgery is safe and effective. Ninety seven percent of patients had
CARPAL TUNNEL SYNDROME
479
Fig 6 Complications after carpal tunnel surgery.
complete or partial relief of their symptoms and 60% of patients reported immediate relief of their paraesthesiae postoperatively. No relationship was observed between the type of symptom experienced and the severity of the electrophysiological abnormality. The median duration of symptoms before surgery was 2 years, and one might expect that the more prolonged the symptom duration, the more severe the electrophysiological impairment encountered. However, our results would suggest that no such relationship exists and there was also no relationship between the severity of the carpal tunnel syndrome (as indicated by electrophysiological testing) and the outcome after surgery. With the exception of the four patients with extremely severe electrophysiological abnormality, all of whom did not recover fully, the patients with the more severe grades of abnormality did just as well as those with moderate grades of nerve conduction impairment. Additionally, we found no relationship between the severity of the preoperative electrophysiological abnormality and the time to postoperative recovery and relief of symptoms. This is surprising as increased pressure within the carpal tunnel is thought to lead to occlusion of intraneural vessels leading to ischaemia (Sunderland, 1976) When this compression is released, the pressure is relieved and so the circulation improves (Rydevic et al., 1981), which corresponds with the rapid improvement in symptoms seen in most patients after surgery. If compression is chronic, ischaemia is followed by intrafascicular oedema (Lundborg et al., 1983), fibroblast infiltration and scar formation (Sunderland, 1976). One would expect that the more chronic the condition, the more axonal damage would occur leading to a greater electrophysiological
impairment and a less successful and slower recovery after surgery. Clearly, our study has limitations, especially as it is retrospective in nature. Although the electrophysiological tests were performed in a uniform manner, they were not performed by one individual and a number of different surgeons, with different levels of expertise, performed the operations. On this basis, it would be unwise to make emphatic conclusions from the data. Nonetheless, this study has revealed some interesting results and will form the basis for a larger prospective controlled trial in which we will rigorously assess the role of electrophysiological tests in the management and prediction of outcome of carpal tunnel syndrome. Acknowledgements No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
References AAEM Quality assurance committee (1993). Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. Muscle & Nerve, 16: 1392–1414. Bland JDP (2000). A neurophysiological grading scale of carpal tunnel syndrome. Muscle & Nerve, 23: 1280–1283. Buch-Jaeger N, Foucher G (1994). Correlation of clinical signs with nerve conduction tests in the diagnosis of carpal tunnel syndrome. Journal of Hand Surgery, 19B: 6: 720–724. Concannon MJ, Gainor B, Petroski G, Puckett C (1997). The predictive value of electrodiagnostic studies in carpal tunnel syndrome. Plastic and Reconstructive Surgery, 100: 6: 1452–1458. Graham RA (1983). Carpal tunnel syndrome: a statistical analysis of 214 cases. Orthopaedics, 66: 1283. Grundberg AB (1983). Carpal tunnel decompression in spite of normal electromyography. Journal of Hand Surgery, 8: 348–349. Kimura I, Ayyar DR (1985). Carpal tunnel syndrome: electrophysiological aspects of 639 symptomatic extremities. Electromyography & Clinical Neurophysiology, 25: 151.
480 Lundborg G, Myers R, Powell H (1983). Nerve compression injury and increased endoneural fluid pressure: A ‘‘miniature compression syndrome.’’ Journal of Neurology, Neurosurgery & Psychiatry, 46: 1119– 1124. Padua I, Padua R, Aprile I, Tonali P (1999). Italian multicentre study of carpal tunnel syndrome. Differences in the clinical and neurophysiological features between male and female patients. Journal of Hand Surgery, 24B: 5: 579–582. Rydevic B, Lundborg G, Bagge U (1981). Effects of graded compression on intraneural blood flow. An in vivo study on rabbit tibial nerve. Journal of Hand Surgery, 6: 3–12. Stevens JC (1987). The electrodiagnosis of Carpal Tunnel Syndrome. Muscle & Nerve, 10: 99.
THE JOURNAL OF HAND SURGERY VOL. 26B No. 5 OCTOBER 2001 Sunderland S (1976). The nerve lesion of carpal tunnel syndrome. Journal of Neurology, Neurosurgery & Psychiatry, 39: 615–626.
Received: 15 December 2000 Accepted after revision: 6 April 2001 Mr L. Longstaff, 2 Woodbine Road, Gosforth, Newcastle upon Tyne NE3 1DD UK. E-mail: [email protected] # 2001 The British Society for Surgery of the Hand doi: 10.1054/jhsb.2001.0616, available online at http://www.idealibrary.com on