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Electrical studies as a prognostic factor in the surgical treatment of carpal tunnel syndrome
The Journal of Hand Surgery/Vo{. 21A No. 3 May 1996
decisions regarding diagnosis and treatment are imprecise and prone to error. 2'3 Peter A. Nathan, MD Richard C. Keniston, MD Kenneth D. Meadows, PT Portland Hand Surgery and Rehabilitation Center 2455 N W Marshall, Suite 1 Portland, OR 97210-2997
References 1. Braun RM, Jackson WJ. Electrical studies as a prognostic factor in the surgical treatmentof carpal tunnel syndrome. J Hand Surg 1994;19A:893-900. 2. Nathan PA, Meadows KD, Keniston RC. Rehabilitationof carpal tunnel surgerypatients using a short surgicalincision and an early program of physical therapy. J Hand Surg 1993;18A:1044-1050. 3. Nathan PA, Keniston RC, Meadows KD, Lockwood RS. Predictive value of nerve conduction measurements at the carpal tunnel. Muscle Nerve 1993;16:1377-1382.
In Reply: In response to Nathan, Keniston, and Meadows, our studies reviewed the neurologic reports usually generated in our community regarding carpal tunnel syndrome. It is obvious that more sensitive measurements would result in more positive findings. The balance between sensitivity and specificity is always reasonable to consider. While we do not reject more sensitive methods, we elected to use the neurologists' reports of abnormality and reviewed our patients' progress following surgical treatment. Our findings were published in a fair and statistically valid way and indicated what actually happens in this community. Dr. Nathan and colleagues apparently agree with our general conclusion regarding the limited usefulness of electrodiagnostic studies as a prognostic factor for return to work. Our contribution is that the functional-recovery curve measurement for these injured hands does not appear to show any variation based on preoperative electrodiagnostic studies. The functional recovery curve excludes the social and economic factors that affect return-to-work time in a complex industrial society. Richard M. Braun, MD 6699 Alvarado Road, Suite 2302 San Diego, CA 92120
527
Electrical Studies as a Prognostic Factor in the Surgical Treatment of Carpal Tunnel Syndrome To the Editor: Braun and Jackson reported that electrodiagnostic testing did not predict functional recovery or reemployment after carpal tunnel release in patients with occupational carpal tunnel syndrome (CTS). 7 The electrodiagnostic data are scanty. Patients were considered to have CTS if there was "any electrical abnormality," potentially including patients with disparate conditions, such as generalized neuropathies. The electrical abnormality detected was usually a sensory latency over 3.5 ms, suggesting these studies employed a digital technique over a distance of 13-14 cm. Of the 125 patients who underwent electrical studies, 75 (60%) showed an abnormality. The recently published Practice Parameter for Electrodiagnostic Studies in Carpal Tunnel Syndrome, reporting an exhaustive literature search done by the quality assurance committee of the American Association of Electrodiagnostic Medicine, concludes that conduction studies can confirm a clinical diagnosis of CTS with a high degree of sensitivity and specificity, that sensory studies are more sensitive than motor studies, and that sensory or mixed conduction studies over the 13-14 cm between wrist and digit are less sensitive than techniques employing the shorter 7-8 cm segment between palm and wrist or than those comparing median to ulnar or radial latency? In Braun and Jackson's study, patients with severe CTS were excluded, leaving a large group of patients with mild to moderate CTS, by both clinical and electrodiagnostic criteria. The patients were further homogenized by using only threshold electrical abnormalities and excluding "incremental abnormalities.TM The study design would therefore make it difficult to detect differences between groups. In addition, the pathophysiology of nerve compression can produce severe electrical abnormalities in terms of slowed conduction but with an excellent prognosis for recovery because of the rapidity of remyelination over a demyelinated segment once compression is relieved. If electromyography can play a meaningful role in prognosticating after carpal tunnel release, detecting CTS will likely require more precision than can be achieved with the relatively blunt instruments used in this investigation. William W. Campbell, MD American Association of'Electrodiagnostic Medicine 21 Second, Street SW, Suite 103 Rochester, MN 55902
528
Lettersto the Editor
References 1. Braun RM, Jackson WJ. Electrical studies as a prognostic factor in the surgical treatment of carpal tunnel syndrome. J Hand Surg 1994;19A:893-900. 2. Jablecki CK, Andary MT, So YT, Wilkins DE, Williams FH. Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. Muscle Nerve 1993;16: 1392-1414.
In Reply: Dr. Campbell indicates dissatisfaction with the methods of electrical testing used in our article. As we have indicated, the electrodiagnostic methodology that was used in our study came from established neurologists in the San Diego community. We asked these physicians to advise us regarding whether they considered their studies to indicate normal values or abnormal values indicating nerve pathology. Whcn any one neurologist reported an abnormal study, we added the patients involved to the group of patients considered to have electrodiagnostic evidence of pathology. Our practice relies on the services of neurologists in interpreting their own studies, and we accepted their evaluation of the work they performed. The decision to remove type IV patients from our study was arbitrary. If these patients were added to the study, this would have created a bias against the use of electrodiagnostic tools. The prognosis for people with long-standing nerve compression, anesthesia in the area of the median nerve, major atrophy in the musculature of the hand, and a history of impact injury is poor regardless of electrodiagnostic assistance in diagnosis. We selected a group of patients t h a t we wished to study because these are the most important, most numerous, and most economically significant group of patients that we see. Dr. Campbell appears to take a position that our article negated the value of electrical testing. This is not the case. We find electrical studies are helpful in making the diagnosis of carpal tunnel syndrome. We discuss our surgical decision-making process with the patient and with all interested parties. Our track record speaks for itself. The facts were presented in a fair, unbiased, and statistically significant fashion. In the patient population that we have seen over a period of 5 years in a community practice devoted to surgery of the hand, electrodiagnostic studies of the threshold type reported do not affect prognosis. Richard M. Braun, MD 6699 Alvarado Road, Suite 2302 San Diego, CA 92120
Outcome Following Conservative Management of Thoracic Outlet Syndrome To the Editor: We were not surprised to learn that exercise can ameliorate upper extremity/neck symptoms (Novak CB, Collins ED, MacKinnon SE. Outcome following conservative management of thoracic outlet syndrome. J Hand Surg 1995;20A:542-8). Nor were we surprised that a high percentage of the patients had carpal tunnel syndrome (CTS) and/or cubital tunnel syndrome. This suggests that much of what was believed to be thoracic outlet syndrome (TOS) may be a pattern of proximally referred symptoms from a more peripheral entrapment of the median or ulnar nerves, rather than true neurogenic TOS? We have never confirmed a diagnosis of presumed TOS made elsewhere. Most often, we have found-using the more sensitive segmental nerve conduction techniques2--these patients to have median and/or ulnar nerve conduction abnormalities or transient musculoskeletal symptoms. Use of less sensitive median/ulnar nerve conduction techniques can result in a missed CTS/cubital tunnel syndrome diagnosis, 2'3 which may be misinterpreted as TOS. Our treatment is directed at the CTS or cubital tunnel syndrome, and we find that the proximal symptoms (called TOS by some) abate as well. The fact that the more proximal symptoms abated easily but the more distal symptoms tended to persist suggests that the more distal symptoms (and pathology) were primary. In our experience, exercise is often effective for at least transient control of the secondary and referred symptoms of CTS, but it is rarely effective for the primary, distal symptoms if there are moderate or severe nerve conduction abnormalities. Peter A. Nathan, MD Portland Hand Surgery and Rehabilitation Center 2455 N W Marshall, Suite 1 Portland, OR 97210-2997
References 1. Wilbourn AJ. Thoracic outlet syndrome. Controversies in entrapment neuropathies: court D-7th Annual Continuing Education Course. American Associaton of Electromyography and Electrodiagnosis 1984; 28-38. 2. Seror P, Nathan PA. Relative frequency of nerve conduction abnormalities at carpal tunnel and cubita! tunnel in France and the United States: importance of silent neuropathies and role of ulnar neuropathy after unsuccessful carpal tunnel syndrome release. Ann Chir Main 1993; 12:281-285.
decisions regarding diagnosis and treatment are imprecise and prone to error. 2'3 Peter A. Nathan, MD Richard C. Keniston, MD Kenneth D. Meadows, PT Portland Hand Surgery and Rehabilitation Center 2455 N W Marshall, Suite 1 Portland, OR 97210-2997
References 1. Braun RM, Jackson WJ. Electrical studies as a prognostic factor in the surgical treatmentof carpal tunnel syndrome. J Hand Surg 1994;19A:893-900. 2. Nathan PA, Meadows KD, Keniston RC. Rehabilitationof carpal tunnel surgerypatients using a short surgicalincision and an early program of physical therapy. J Hand Surg 1993;18A:1044-1050. 3. Nathan PA, Keniston RC, Meadows KD, Lockwood RS. Predictive value of nerve conduction measurements at the carpal tunnel. Muscle Nerve 1993;16:1377-1382.
In Reply: In response to Nathan, Keniston, and Meadows, our studies reviewed the neurologic reports usually generated in our community regarding carpal tunnel syndrome. It is obvious that more sensitive measurements would result in more positive findings. The balance between sensitivity and specificity is always reasonable to consider. While we do not reject more sensitive methods, we elected to use the neurologists' reports of abnormality and reviewed our patients' progress following surgical treatment. Our findings were published in a fair and statistically valid way and indicated what actually happens in this community. Dr. Nathan and colleagues apparently agree with our general conclusion regarding the limited usefulness of electrodiagnostic studies as a prognostic factor for return to work. Our contribution is that the functional-recovery curve measurement for these injured hands does not appear to show any variation based on preoperative electrodiagnostic studies. The functional recovery curve excludes the social and economic factors that affect return-to-work time in a complex industrial society. Richard M. Braun, MD 6699 Alvarado Road, Suite 2302 San Diego, CA 92120
527
Electrical Studies as a Prognostic Factor in the Surgical Treatment of Carpal Tunnel Syndrome To the Editor: Braun and Jackson reported that electrodiagnostic testing did not predict functional recovery or reemployment after carpal tunnel release in patients with occupational carpal tunnel syndrome (CTS). 7 The electrodiagnostic data are scanty. Patients were considered to have CTS if there was "any electrical abnormality," potentially including patients with disparate conditions, such as generalized neuropathies. The electrical abnormality detected was usually a sensory latency over 3.5 ms, suggesting these studies employed a digital technique over a distance of 13-14 cm. Of the 125 patients who underwent electrical studies, 75 (60%) showed an abnormality. The recently published Practice Parameter for Electrodiagnostic Studies in Carpal Tunnel Syndrome, reporting an exhaustive literature search done by the quality assurance committee of the American Association of Electrodiagnostic Medicine, concludes that conduction studies can confirm a clinical diagnosis of CTS with a high degree of sensitivity and specificity, that sensory studies are more sensitive than motor studies, and that sensory or mixed conduction studies over the 13-14 cm between wrist and digit are less sensitive than techniques employing the shorter 7-8 cm segment between palm and wrist or than those comparing median to ulnar or radial latency? In Braun and Jackson's study, patients with severe CTS were excluded, leaving a large group of patients with mild to moderate CTS, by both clinical and electrodiagnostic criteria. The patients were further homogenized by using only threshold electrical abnormalities and excluding "incremental abnormalities.TM The study design would therefore make it difficult to detect differences between groups. In addition, the pathophysiology of nerve compression can produce severe electrical abnormalities in terms of slowed conduction but with an excellent prognosis for recovery because of the rapidity of remyelination over a demyelinated segment once compression is relieved. If electromyography can play a meaningful role in prognosticating after carpal tunnel release, detecting CTS will likely require more precision than can be achieved with the relatively blunt instruments used in this investigation. William W. Campbell, MD American Association of'Electrodiagnostic Medicine 21 Second, Street SW, Suite 103 Rochester, MN 55902
528
Lettersto the Editor
References 1. Braun RM, Jackson WJ. Electrical studies as a prognostic factor in the surgical treatment of carpal tunnel syndrome. J Hand Surg 1994;19A:893-900. 2. Jablecki CK, Andary MT, So YT, Wilkins DE, Williams FH. Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. Muscle Nerve 1993;16: 1392-1414.
In Reply: Dr. Campbell indicates dissatisfaction with the methods of electrical testing used in our article. As we have indicated, the electrodiagnostic methodology that was used in our study came from established neurologists in the San Diego community. We asked these physicians to advise us regarding whether they considered their studies to indicate normal values or abnormal values indicating nerve pathology. Whcn any one neurologist reported an abnormal study, we added the patients involved to the group of patients considered to have electrodiagnostic evidence of pathology. Our practice relies on the services of neurologists in interpreting their own studies, and we accepted their evaluation of the work they performed. The decision to remove type IV patients from our study was arbitrary. If these patients were added to the study, this would have created a bias against the use of electrodiagnostic tools. The prognosis for people with long-standing nerve compression, anesthesia in the area of the median nerve, major atrophy in the musculature of the hand, and a history of impact injury is poor regardless of electrodiagnostic assistance in diagnosis. We selected a group of patients t h a t we wished to study because these are the most important, most numerous, and most economically significant group of patients that we see. Dr. Campbell appears to take a position that our article negated the value of electrical testing. This is not the case. We find electrical studies are helpful in making the diagnosis of carpal tunnel syndrome. We discuss our surgical decision-making process with the patient and with all interested parties. Our track record speaks for itself. The facts were presented in a fair, unbiased, and statistically significant fashion. In the patient population that we have seen over a period of 5 years in a community practice devoted to surgery of the hand, electrodiagnostic studies of the threshold type reported do not affect prognosis. Richard M. Braun, MD 6699 Alvarado Road, Suite 2302 San Diego, CA 92120
Outcome Following Conservative Management of Thoracic Outlet Syndrome To the Editor: We were not surprised to learn that exercise can ameliorate upper extremity/neck symptoms (Novak CB, Collins ED, MacKinnon SE. Outcome following conservative management of thoracic outlet syndrome. J Hand Surg 1995;20A:542-8). Nor were we surprised that a high percentage of the patients had carpal tunnel syndrome (CTS) and/or cubital tunnel syndrome. This suggests that much of what was believed to be thoracic outlet syndrome (TOS) may be a pattern of proximally referred symptoms from a more peripheral entrapment of the median or ulnar nerves, rather than true neurogenic TOS? We have never confirmed a diagnosis of presumed TOS made elsewhere. Most often, we have found-using the more sensitive segmental nerve conduction techniques2--these patients to have median and/or ulnar nerve conduction abnormalities or transient musculoskeletal symptoms. Use of less sensitive median/ulnar nerve conduction techniques can result in a missed CTS/cubital tunnel syndrome diagnosis, 2'3 which may be misinterpreted as TOS. Our treatment is directed at the CTS or cubital tunnel syndrome, and we find that the proximal symptoms (called TOS by some) abate as well. The fact that the more proximal symptoms abated easily but the more distal symptoms tended to persist suggests that the more distal symptoms (and pathology) were primary. In our experience, exercise is often effective for at least transient control of the secondary and referred symptoms of CTS, but it is rarely effective for the primary, distal symptoms if there are moderate or severe nerve conduction abnormalities. Peter A. Nathan, MD Portland Hand Surgery and Rehabilitation Center 2455 N W Marshall, Suite 1 Portland, OR 97210-2997
References 1. Wilbourn AJ. Thoracic outlet syndrome. Controversies in entrapment neuropathies: court D-7th Annual Continuing Education Course. American Associaton of Electromyography and Electrodiagnosis 1984; 28-38. 2. Seror P, Nathan PA. Relative frequency of nerve conduction abnormalities at carpal tunnel and cubita! tunnel in France and the United States: importance of silent neuropathies and role of ulnar neuropathy after unsuccessful carpal tunnel syndrome release. Ann Chir Main 1993; 12:281-285.