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Treatment of Extensor Digitorum Brevis Manus Myalgia With Botulinum Toxin
Case Presentation
Treatment of Extensor Digitorum Brevis Manus Myalgia With Botulinum Toxin Ian Wendel, DO, Jeffrey Cole, MD Extensor digitorum brevis manus (EDBM) muscles are accessory dorsal hand muscles that are present in 1%-3% of the population. These muscles are not commonly symptomatic, but they can occasionally cause pain and discomfort and may be misdiagnosed as tenosynovitis or a ganglion cyst. In this case, we describe an appropriate workup of dorsal hand masses and myalgia that are suspected to be related to EDBM muscles. The patient’s symptoms were controlled with injections of botulinum toxin into the EDMB muscle belly, which allowed the patient to be relatively pain free for a considerable amount of time and avoid surgery. PM R 2014;6:284-286
INTRODUCTION Dorsal hand pain with an associated mass is a common presenting symptom at physicians’ offices. Differential diagnoses of these symptoms may include tenosynovitis, a ganglion cyst, a torn interosseus muscle, a soft tissue tumor, exostosis, and carpal bossing. Accessory hand muscles to the dorsum of the hand, although rare, are a potential cause of discomfort originating from the dorsum of the hand [1-3]. An example of a dorsal accessory hand muscle is the extensor digitorum brevis manus (EDBM). This muscle’s origin has been described as being at the distal end of the radius, the dorsal radiocarpal ligament, or the wrist joint capsule, and the insertion has been described as being at the extensor hood of the second, third, fourth, or fifth digits, with insertions into multiple digits possible [4,5]. These rare, anomalous muscles, which are present in 1%-3% of the population, occur bilaterally a third of the time, are usually more prominent in the dominant hand, and are occasionally seen in families [6-8].
CASE PRESENTATION At initial presentation, a 39-year-old right-handed woman with a history of osteopenia whose work-related activities included a great deal of typing presented to an outpatient office with right dorsal hand pain of many years’ duration. While inspecting the right hand, we noticed masses at the distal edge of the extensor retinaculum, and this area was tender to palpation. Further examination showed that the masses adjacent to the second and third digital extensor tendons were more prominent with digital extension and abduction, along with wrist flexion. Similar masses were present on the left hand but were asymptomatic. After performing a full electrodiagnostic examination, including radial motor nerve conduction studies, we identified these masses as posterior interosseous nerve innervated muscles and concluded that they were EDBM muscles. Magnetic resonance imaging findings confirmed the presence of EDBM muscles and demonstrated a tear of the aponeurosis in EDBM II (Figure 1). Attempts were made to treat the patient’s pain with a neutral wrist brace, and the ergonomics at her workplace were addressed; however, these steps did not provide relief. Subsequently the EDBM II was injected with 35 units of botulinum toxin via a dorsal approach and electromyographic guidance every 2 years (2002, 2004, 2006, 2008, and 2011). A good clinical response was noted, including relief of myalgic pain and cramping that lasted on average 1.5 years. After these injections, no decrease in function of the treated hand or adverse effects were noted. PM&R
284
1934-1482/13/$36.00 Printed in U.S.A.
I.W. New Jersey Medical School, Doctor’s Office Center, Suite 3200, 90 Bergen St, Newark, NJ 07101. Address correspondence to: I.W.; e-mail: [email protected] Disclosure: nothing to disclose J.C. Kessler Institute for Rehabilitation, West Orange, NJ Disclosure: nothing to disclose Submitted for publication April 1, 2013; accepted September 13, 2013.
ª 2014 by the American Academy of Physical Medicine and Rehabilitation Vol. 6, 284-286, March 2014 http://dx.doi.org/10.1016/j.pmrj.2013.09.010
PM&R
Vol. 6, Iss. 3, 2014
285
Figure 2. The patient’s right hand at rest.
Figure 1. An axial magnetic resonance imaging scan identifying the presence of an extensor digitorum brevis manus II before treatment, as indicated by the arrows.
DISCUSSION Although anomalous EDBM muscles are commonly asymptomatic, they occasionally cause pain and discomfort. It has been suggested that when these muscles occur they can be compressed against the extensor retinaculum because little room is available to accommodate them within the fourth dorsal compartment in the wrist. This condition has subsequently been termed “fourth compartment syndrome” [9,10]. It has also been suggested that the posterior interosseous nerve may become directly or indirectly entrapped within the fourth dorsal compartment, resulting in symptoms [11]. Another explanation is muscle cramps, possibly related to denervation [12]. We believe that the first scenario is likely with regard to the underlining pathophysiology of the patient’s symptoms. The botulinum toxin injections likely are able to relax the entrapped muscle enabling the EDBM muscle to move more freely within the fourth dorsal compartment. Interestingly, the patient in this case receives approximately 1.5 years of relief per botulinum toxin injection, whereas the effects of botulinum toxin typically last around 3 months. It is not entirely clear why the patient receives continued benefit from the injection, well past 3 months, but it is possible the repetitive nature of her job flares up her symptoms. Knowledge of the existence of the EDBM and the possibility that this accessory muscle could be causing symptoms is necessary for it to be included in a differential diagnosis of dorsal hand pain. These muscles can be visualized and palpated as previously described. Digital extension and abduction of the hand, along with wrist flexion, causes these
masses to protrude (Figures 2,3). As noted previously, the EDBM can be seen on imaging modalities that adequately visualize soft tissues, such as magnetic resonance imaging. Ultrasound also can be used to visualize these muscles [13]. One case report has documented localization of the EDBM with an electromyographic/nerve conduction study [12]. After reviewing the literature, we believe that this report documents the only known case to date in which botulinum toxin was injected into the EDBM as a treatment option for EDBM myalgia. A clinician can wait to see whether symptoms improve with conservative treatment, including rest of the afflicted area, heat, ice, medications, bracing, and/or therapeutic exercise; however, we are unaware of any evidence to support these treatment options. Other treatment options that have been suggested are an extensor retinaculum release [14] or resection of the EDBM [15]. Based on
Figure 3. Digital extension and abduction, along with wrist flexion, promotes detection of the extensor digitorum brevis manus II, as indicated by the arrow.
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the good outcome seen in this case, we propose that injection of the EDBM with botulinum toxin for the treatment of EDBM myalgia is a viable alternative to surgery, providing decreased risks and greater cost-effectiveness compared with the aforementioned surgical procedures.
CONCLUSION EDBM myalgia is rare cause of dorsal hand pain that may be misdiagnosed as a ganglion cyst or tenosynovitis. This case report demonstrates the ability to successfully treat EDBM myalgia with botulinum toxin, which allowed this patient to avoid surgery.
REFERENCES 1. Jeffery AK. Compression of the deep palmar branch of the ulnar nerve by an anomalous muscle. Case report and review. J Bone Joint Surg Br 1971;53:718-723. 2. Ross JA, Troy CA. The clinical significance of the extensor digitorum brevis manus. J Bone Joint Surg Br 1969;51:473-478. 3. Still JM Jr., Kleinert HE. Anomalous muscles and nerve entrapment in the wrist and hand. Plast Reconstr Surg 1973;52:394-400. 4. el-Badawi MG, Butt MM, al-Zuhair AG, Fadel RA. Extensor tendons of the fingers: Arrangement and variations—II. Clin Anat 1995;8:391-398.
TREATMENT OF EDBM MYALGIA WITH BOTOX
5. Paraskevas G, Papaziogas B, Spanidou S, Papadopoulos A. Unusual variation of the extensor digitorum brevis manus: A case report. Orthop Tramatol 2002;12:3. 6. Gama C. Extensor digitorum brevis manus: A report on 38 cases and a review of the literature. J Hand Surg Am 1983;8(5 Pt 1):578-582. 7. McGregor AL. A contribution to the morphology of the thumb. J Anat 1926;60(Pt 3):259-273. 8. Rodriguez-Niedenfuhr M, Vazquez T, Golano P, Parkin I, Sanudo JR. Extensor digitorum brevis manus: Anatomical, radiological and clinical relevance. A review. Clin Anat 2002;15:286-292. 9. Ritter MA, Inglis AE. The extensor indicis proprius syndrome. J Bone Joint Surg Am 1969;51:1645-1648. 10. Ranade AV, Rai R, Prabhu LV, et al. Incidence of extensor digitorum brevis manus muscle. Hand (N Y) 2008;3:320-323. 11. Hoffman J, Ellison MR. Extensor digitorum brevis manus in the nondominant hand of two brothers. J Hand Surg Am 1987;12: 293-294. 12. McManis PG, Daube JR. Electromyographic evaluation of an accessory hand muscle. Muscle Nerve 1989;12:460-463. 13. Ouellette H, Thomas BJ, Torriani M. Using dynamic sonography to diagnose extensor digitorum brevis manus. AJR Am J Roentgenol 2003; 181(5):1224-1226. 14. Komiyama M, Nwe TM, Toyota N, Shimada Y. Variations of the extensor indicis muscle and tendon. J Hand Surg Br 1999;24: 575-578. 15. Dostal GH, Lister GD, Hutchinson D, Mogan JV, Davis PH. Extensor digitorum brevis manus associated with a dorsal wrist ganglion: A review of five cases. J Hand Surg Am 1995;20:35-37.
Treatment of Extensor Digitorum Brevis Manus Myalgia With Botulinum Toxin Ian Wendel, DO, Jeffrey Cole, MD Extensor digitorum brevis manus (EDBM) muscles are accessory dorsal hand muscles that are present in 1%-3% of the population. These muscles are not commonly symptomatic, but they can occasionally cause pain and discomfort and may be misdiagnosed as tenosynovitis or a ganglion cyst. In this case, we describe an appropriate workup of dorsal hand masses and myalgia that are suspected to be related to EDBM muscles. The patient’s symptoms were controlled with injections of botulinum toxin into the EDMB muscle belly, which allowed the patient to be relatively pain free for a considerable amount of time and avoid surgery. PM R 2014;6:284-286
INTRODUCTION Dorsal hand pain with an associated mass is a common presenting symptom at physicians’ offices. Differential diagnoses of these symptoms may include tenosynovitis, a ganglion cyst, a torn interosseus muscle, a soft tissue tumor, exostosis, and carpal bossing. Accessory hand muscles to the dorsum of the hand, although rare, are a potential cause of discomfort originating from the dorsum of the hand [1-3]. An example of a dorsal accessory hand muscle is the extensor digitorum brevis manus (EDBM). This muscle’s origin has been described as being at the distal end of the radius, the dorsal radiocarpal ligament, or the wrist joint capsule, and the insertion has been described as being at the extensor hood of the second, third, fourth, or fifth digits, with insertions into multiple digits possible [4,5]. These rare, anomalous muscles, which are present in 1%-3% of the population, occur bilaterally a third of the time, are usually more prominent in the dominant hand, and are occasionally seen in families [6-8].
CASE PRESENTATION At initial presentation, a 39-year-old right-handed woman with a history of osteopenia whose work-related activities included a great deal of typing presented to an outpatient office with right dorsal hand pain of many years’ duration. While inspecting the right hand, we noticed masses at the distal edge of the extensor retinaculum, and this area was tender to palpation. Further examination showed that the masses adjacent to the second and third digital extensor tendons were more prominent with digital extension and abduction, along with wrist flexion. Similar masses were present on the left hand but were asymptomatic. After performing a full electrodiagnostic examination, including radial motor nerve conduction studies, we identified these masses as posterior interosseous nerve innervated muscles and concluded that they were EDBM muscles. Magnetic resonance imaging findings confirmed the presence of EDBM muscles and demonstrated a tear of the aponeurosis in EDBM II (Figure 1). Attempts were made to treat the patient’s pain with a neutral wrist brace, and the ergonomics at her workplace were addressed; however, these steps did not provide relief. Subsequently the EDBM II was injected with 35 units of botulinum toxin via a dorsal approach and electromyographic guidance every 2 years (2002, 2004, 2006, 2008, and 2011). A good clinical response was noted, including relief of myalgic pain and cramping that lasted on average 1.5 years. After these injections, no decrease in function of the treated hand or adverse effects were noted. PM&R
284
1934-1482/13/$36.00 Printed in U.S.A.
I.W. New Jersey Medical School, Doctor’s Office Center, Suite 3200, 90 Bergen St, Newark, NJ 07101. Address correspondence to: I.W.; e-mail: [email protected] Disclosure: nothing to disclose J.C. Kessler Institute for Rehabilitation, West Orange, NJ Disclosure: nothing to disclose Submitted for publication April 1, 2013; accepted September 13, 2013.
ª 2014 by the American Academy of Physical Medicine and Rehabilitation Vol. 6, 284-286, March 2014 http://dx.doi.org/10.1016/j.pmrj.2013.09.010
PM&R
Vol. 6, Iss. 3, 2014
285
Figure 2. The patient’s right hand at rest.
Figure 1. An axial magnetic resonance imaging scan identifying the presence of an extensor digitorum brevis manus II before treatment, as indicated by the arrows.
DISCUSSION Although anomalous EDBM muscles are commonly asymptomatic, they occasionally cause pain and discomfort. It has been suggested that when these muscles occur they can be compressed against the extensor retinaculum because little room is available to accommodate them within the fourth dorsal compartment in the wrist. This condition has subsequently been termed “fourth compartment syndrome” [9,10]. It has also been suggested that the posterior interosseous nerve may become directly or indirectly entrapped within the fourth dorsal compartment, resulting in symptoms [11]. Another explanation is muscle cramps, possibly related to denervation [12]. We believe that the first scenario is likely with regard to the underlining pathophysiology of the patient’s symptoms. The botulinum toxin injections likely are able to relax the entrapped muscle enabling the EDBM muscle to move more freely within the fourth dorsal compartment. Interestingly, the patient in this case receives approximately 1.5 years of relief per botulinum toxin injection, whereas the effects of botulinum toxin typically last around 3 months. It is not entirely clear why the patient receives continued benefit from the injection, well past 3 months, but it is possible the repetitive nature of her job flares up her symptoms. Knowledge of the existence of the EDBM and the possibility that this accessory muscle could be causing symptoms is necessary for it to be included in a differential diagnosis of dorsal hand pain. These muscles can be visualized and palpated as previously described. Digital extension and abduction of the hand, along with wrist flexion, causes these
masses to protrude (Figures 2,3). As noted previously, the EDBM can be seen on imaging modalities that adequately visualize soft tissues, such as magnetic resonance imaging. Ultrasound also can be used to visualize these muscles [13]. One case report has documented localization of the EDBM with an electromyographic/nerve conduction study [12]. After reviewing the literature, we believe that this report documents the only known case to date in which botulinum toxin was injected into the EDBM as a treatment option for EDBM myalgia. A clinician can wait to see whether symptoms improve with conservative treatment, including rest of the afflicted area, heat, ice, medications, bracing, and/or therapeutic exercise; however, we are unaware of any evidence to support these treatment options. Other treatment options that have been suggested are an extensor retinaculum release [14] or resection of the EDBM [15]. Based on
Figure 3. Digital extension and abduction, along with wrist flexion, promotes detection of the extensor digitorum brevis manus II, as indicated by the arrow.
286
Wendel and Cole
the good outcome seen in this case, we propose that injection of the EDBM with botulinum toxin for the treatment of EDBM myalgia is a viable alternative to surgery, providing decreased risks and greater cost-effectiveness compared with the aforementioned surgical procedures.
CONCLUSION EDBM myalgia is rare cause of dorsal hand pain that may be misdiagnosed as a ganglion cyst or tenosynovitis. This case report demonstrates the ability to successfully treat EDBM myalgia with botulinum toxin, which allowed this patient to avoid surgery.
REFERENCES 1. Jeffery AK. Compression of the deep palmar branch of the ulnar nerve by an anomalous muscle. Case report and review. J Bone Joint Surg Br 1971;53:718-723. 2. Ross JA, Troy CA. The clinical significance of the extensor digitorum brevis manus. J Bone Joint Surg Br 1969;51:473-478. 3. Still JM Jr., Kleinert HE. Anomalous muscles and nerve entrapment in the wrist and hand. Plast Reconstr Surg 1973;52:394-400. 4. el-Badawi MG, Butt MM, al-Zuhair AG, Fadel RA. Extensor tendons of the fingers: Arrangement and variations—II. Clin Anat 1995;8:391-398.
TREATMENT OF EDBM MYALGIA WITH BOTOX
5. Paraskevas G, Papaziogas B, Spanidou S, Papadopoulos A. Unusual variation of the extensor digitorum brevis manus: A case report. Orthop Tramatol 2002;12:3. 6. Gama C. Extensor digitorum brevis manus: A report on 38 cases and a review of the literature. J Hand Surg Am 1983;8(5 Pt 1):578-582. 7. McGregor AL. A contribution to the morphology of the thumb. J Anat 1926;60(Pt 3):259-273. 8. Rodriguez-Niedenfuhr M, Vazquez T, Golano P, Parkin I, Sanudo JR. Extensor digitorum brevis manus: Anatomical, radiological and clinical relevance. A review. Clin Anat 2002;15:286-292. 9. Ritter MA, Inglis AE. The extensor indicis proprius syndrome. J Bone Joint Surg Am 1969;51:1645-1648. 10. Ranade AV, Rai R, Prabhu LV, et al. Incidence of extensor digitorum brevis manus muscle. Hand (N Y) 2008;3:320-323. 11. Hoffman J, Ellison MR. Extensor digitorum brevis manus in the nondominant hand of two brothers. J Hand Surg Am 1987;12: 293-294. 12. McManis PG, Daube JR. Electromyographic evaluation of an accessory hand muscle. Muscle Nerve 1989;12:460-463. 13. Ouellette H, Thomas BJ, Torriani M. Using dynamic sonography to diagnose extensor digitorum brevis manus. AJR Am J Roentgenol 2003; 181(5):1224-1226. 14. Komiyama M, Nwe TM, Toyota N, Shimada Y. Variations of the extensor indicis muscle and tendon. J Hand Surg Br 1999;24: 575-578. 15. Dostal GH, Lister GD, Hutchinson D, Mogan JV, Davis PH. Extensor digitorum brevis manus associated with a dorsal wrist ganglion: A review of five cases. J Hand Surg Am 1995;20:35-37.