Pediatr Radiol (2016) 46:293–295 DOI 10.1007/s00247-015-3461-2
CASE REPORT
A rare accessory muscle in the hand — the flexor digitorum superficialis indicis Wendy D. Ellis 1,2 & Stephanie E. Spottswood 1 & Steven A. Lovejoy 3
Received: 17 February 2015 / Revised: 23 July 2015 / Accepted: 28 August 2015 / Published online: 28 September 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Accessory muscles are easily overlooked during imaging evaluation. Although usually discovered incidentally, they are occasionally symptomatic. With increasing utilization of cross-sectional imaging, the radiologist should be prepared to readily identify these anomalous muscles. It is particularly important to distinguish these anatomical variants from soft-tissue tumors prior to invasive intervention, reserving biopsy and surgery for children who are symptomatic. This report discusses a case of a flexor digitorum superficialis indicis muscle, an extremely rare but well-described accessory muscle, presenting as a painful mass in a 15-year-old girl. The report includes the clinical presentation, radiologic findings, and the significance to management.
Keywords Accessory muscle . Adolescent . Flexor digitorum superficialis indicis . Hand . Magnetic resonance imaging
* Wendy D. Ellis [email protected] 1
Department of Radiology and Radiologic Sciences, Monroe Carell Jr. Children’s Hospital at Vanderbilt, 2200 Children’s Way, Ste. 1415, Nashville, TN 37232-9700, USA
2
Department of Pediatrics, Monroe Carell Jr. Children’s Hospital at Vanderbilt, Nashville, TN, USA
3
Department of Orthopaedics and Rehabilitation, Monroe Carell Jr. Children’s Hospital at Vanderbilt, Nashville, TN, USA
Introduction A wide variety of supernumerary and accessory muscles have been described in the medical and anatomical literature [1]. These muscles have typically been discovered incidentally during surgery or at autopsy [2–6]. The increasing use of cross-sectional imaging, including US, CT and MRI, has led to discovery of these anatomical variations during routine evaluation or during workup for specific symptoms. Muscle variants are easily overlooked, and when discovered they can be misdiagnosed as soft-tissue tumors. It is important that the radiologist is aware of known muscle variations in order to prevent unnecessary biopsy or surgery in asymptomatic children and to assist in proper diagnosis and treatment in the setting of symptomatic children.
Case report A 15-year-old girl presented to the orthopedic surgery clinic with complaints of a painful lump in the right palm. The lump was initially noticed about 5 years prior, but it had more recently become painful. The girl was right-hand dominant and noticed the pain most significantly while opening bottles using her dominant hand. There was no history of hand trauma. She had no other relevant medical problems, took no prescription or over-the-counter medications and had no known allergies. She had no relevant family history. The girl lived at home with her mother and had no notable social issues. On physical examination, there was noticeable swelling along the volar surface of the second ray with mild tenderness to palpation. There was no skin discoloration and no lymphadenopathy was detected at the elbow or axilla. The girl was referred for radiographs and an MRI.
294
Fig. 1 Axial T2-weighted fat-saturated images of the right hand show (a) a round mass with the signal characteristics of muscle along the volar aspect of the second digit (arrow) in our patient, a 15-year-old girl, and (b) a normal hand in an age- and gender-matched control (a 14-year-old girl)
Pediatr Radiol (2016) 46:293–295
profundus and superficialis tendons. The signal characteristics were uniform and indistinguishable from the normal intrinsic hand muscles (Fig. 1). There was no enhancement of the mass (Fig. 2) nor was there adjacent bone or soft-tissue edema. The mass originated in the carpal tunnel and inserted on the flexor digitorum superficialis tendon of the index finger at the level of the A1 pulley, and it slightly deformed the superficial palmar skin and fat. The flexor digitorum tendons were otherwise normal in course and signal characteristics. The girl was diagnosed with having a rare accessory muscle known as the flexor digitorum superficialis indicis. The combined clinical symptoms and imaging findings prompted referral to the orthopedic hand specialist for surgical evaluation. The girl subsequently underwent surgical excision and debulking of the right hand mass. Both intraoperative and pathological findings were consistent with an accessory flexor digitorum superficialis indicis muscle. The girl tolerated surgery without complication and her symptoms resolved after accessory muscle debulking.
Discussion Standard posteroanterior, oblique and lateral radiographs of the right hand demonstrated no bone or soft-tissue abnormality. MRI of the right hand was performed on a Philips 3-T Achieva magnet (Philips Healthcare, Best, The Netherlands) before and after 10 ml intravenous gadolinium contrast administration (Magnevist; Bayer Healthcare Pharmaceuticals, Whippany, NJ), and included three imaging planes (axial, sagittal and coronal) using T1-W, fat-suppressed T1-W, fatsuppressed T2-W, short tau inversion recovery (STIR) and fatsuppressed proton-density sequences. Within the palmar soft tissues, volar to the second metacarpal, a prominent soft-tissue mass was noted, associated with the flexor digitorum Fig. 2 Coronal T1-weighted images of the right hand show (a) a muscle bundle along the flexor tendon of the second digit (arrows) that is similar in appearance and bulk to the thenar and hypothenar musculature in our patient and (b) a normal hand in an age- and gender-matched control (a 14-year-old girl). No abnormal enhancement was seen in the muscle on post-contrast images
The flexor digitorum superficialis is a large muscle contained in the palmar antebrachial group. Following a normal course, the flexor digitorum superficialis arises from the common flexor origin (having humeral, ulnar and radial components) and extends through the forearm where it separates into deep and superficial components. After passing through the carpal tunnel, the superficial flexor digitorum superficialis tendons insert on the middle and ring fingers and the deep flexor digitorum superficialis tendons insert on the index and long fingers. Three varieties of flexor digitorum superficialis anomalies are described. The digastric type arises in the medial
Pediatr Radiol (2016) 46:293–295
epicondyle in the forearm and crosses the carpal tunnel to insert in the palm. The second type arises from the flexor digitorum superficialis muscle belly in the forearm and extends into the carpal tunnel, but not into the palm. The third type, as seen in our patient, is an intrinsic hand muscle that arises from fibers of the carpal tunnel and inserts on the middle phalanx of the index finger [1]. Anomalous hand muscles are rare and the true incidence is not known. It is important, however, to recognize these normal variants in order to facilitate appropriate management. In many cases, a clinical diagnosis can be challenging and imaging studies are often requested early in the evaluation. This early use of advanced imaging with US, CT or MRI places the burden of diagnosis on the shoulders of the astute radiologist. Although distinguishing these anomalous structures from soft-tissue tumors is crucial, the radiologist should be aware that the muscles could be the cause of the child’s symptoms. Treatment for symptoms associated with accessory hand muscles commonly includes conservative treatment, including pain management and physical therapy. When symptoms are severe or persist with treatment, surgical debulking of the accessory muscle is sometimes needed. In summary, we present a case of an anomalous accessory hand muscle, the flexor digitorum superficialis indicis, in a symptomatic child. Anomalous muscles of the hand can be easily overlooked, even by experienced radiologists, but
295
accurate early identification with radiologic imaging can save the child unnecessary clinical workup (as well as the emotional stress associated with the concern for a tumor) and facilitate prompt and appropriate medical or surgical management. Conflicts of interest None
References 1.
Sookur P, Naraghi A, Bleakney R et al (2008) Accessory muscles: anatomy, symptoms, and radiologic evaluation. Radiographics 28: 481–499 2. Coenen L, Biltjes I (1991) Pseudotumor of the palm due to an anomalous flexor digitorum superficialis muscle belly. J Hand Surg 16A: 1046–1051 3. Dixit SH, Kakar S (2010) An uncommon variation of flexor digitorum superficialis indicis, a case report: anatomic and clinical relevance. Clin Anat 23:889–890 4. Grant S, Due T (1995) Anomalous flexor digitorum superficialis presenting as a painful palmar mass: a case report. Clin Anat 8: 432–433 5. Kostakoglu N, Borman H, Kecik A (1997) Anomalous flexor digitorum superficialis muscle belly: an unusual case of mass in the palm: a case report. Brit J Plast Surg 50:654–656 6. Stephens N, Marques E, Livingston C (2007) Anomalous flexor digitorum superficialis muscle belly presenting as a mass within the palm. Can J Plast Surg 15:44–46
CASE REPORT
A rare accessory muscle in the hand — the flexor digitorum superficialis indicis Wendy D. Ellis 1,2 & Stephanie E. Spottswood 1 & Steven A. Lovejoy 3
Received: 17 February 2015 / Revised: 23 July 2015 / Accepted: 28 August 2015 / Published online: 28 September 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Accessory muscles are easily overlooked during imaging evaluation. Although usually discovered incidentally, they are occasionally symptomatic. With increasing utilization of cross-sectional imaging, the radiologist should be prepared to readily identify these anomalous muscles. It is particularly important to distinguish these anatomical variants from soft-tissue tumors prior to invasive intervention, reserving biopsy and surgery for children who are symptomatic. This report discusses a case of a flexor digitorum superficialis indicis muscle, an extremely rare but well-described accessory muscle, presenting as a painful mass in a 15-year-old girl. The report includes the clinical presentation, radiologic findings, and the significance to management.
Keywords Accessory muscle . Adolescent . Flexor digitorum superficialis indicis . Hand . Magnetic resonance imaging
* Wendy D. Ellis [email protected] 1
Department of Radiology and Radiologic Sciences, Monroe Carell Jr. Children’s Hospital at Vanderbilt, 2200 Children’s Way, Ste. 1415, Nashville, TN 37232-9700, USA
2
Department of Pediatrics, Monroe Carell Jr. Children’s Hospital at Vanderbilt, Nashville, TN, USA
3
Department of Orthopaedics and Rehabilitation, Monroe Carell Jr. Children’s Hospital at Vanderbilt, Nashville, TN, USA
Introduction A wide variety of supernumerary and accessory muscles have been described in the medical and anatomical literature [1]. These muscles have typically been discovered incidentally during surgery or at autopsy [2–6]. The increasing use of cross-sectional imaging, including US, CT and MRI, has led to discovery of these anatomical variations during routine evaluation or during workup for specific symptoms. Muscle variants are easily overlooked, and when discovered they can be misdiagnosed as soft-tissue tumors. It is important that the radiologist is aware of known muscle variations in order to prevent unnecessary biopsy or surgery in asymptomatic children and to assist in proper diagnosis and treatment in the setting of symptomatic children.
Case report A 15-year-old girl presented to the orthopedic surgery clinic with complaints of a painful lump in the right palm. The lump was initially noticed about 5 years prior, but it had more recently become painful. The girl was right-hand dominant and noticed the pain most significantly while opening bottles using her dominant hand. There was no history of hand trauma. She had no other relevant medical problems, took no prescription or over-the-counter medications and had no known allergies. She had no relevant family history. The girl lived at home with her mother and had no notable social issues. On physical examination, there was noticeable swelling along the volar surface of the second ray with mild tenderness to palpation. There was no skin discoloration and no lymphadenopathy was detected at the elbow or axilla. The girl was referred for radiographs and an MRI.
294
Fig. 1 Axial T2-weighted fat-saturated images of the right hand show (a) a round mass with the signal characteristics of muscle along the volar aspect of the second digit (arrow) in our patient, a 15-year-old girl, and (b) a normal hand in an age- and gender-matched control (a 14-year-old girl)
Pediatr Radiol (2016) 46:293–295
profundus and superficialis tendons. The signal characteristics were uniform and indistinguishable from the normal intrinsic hand muscles (Fig. 1). There was no enhancement of the mass (Fig. 2) nor was there adjacent bone or soft-tissue edema. The mass originated in the carpal tunnel and inserted on the flexor digitorum superficialis tendon of the index finger at the level of the A1 pulley, and it slightly deformed the superficial palmar skin and fat. The flexor digitorum tendons were otherwise normal in course and signal characteristics. The girl was diagnosed with having a rare accessory muscle known as the flexor digitorum superficialis indicis. The combined clinical symptoms and imaging findings prompted referral to the orthopedic hand specialist for surgical evaluation. The girl subsequently underwent surgical excision and debulking of the right hand mass. Both intraoperative and pathological findings were consistent with an accessory flexor digitorum superficialis indicis muscle. The girl tolerated surgery without complication and her symptoms resolved after accessory muscle debulking.
Discussion Standard posteroanterior, oblique and lateral radiographs of the right hand demonstrated no bone or soft-tissue abnormality. MRI of the right hand was performed on a Philips 3-T Achieva magnet (Philips Healthcare, Best, The Netherlands) before and after 10 ml intravenous gadolinium contrast administration (Magnevist; Bayer Healthcare Pharmaceuticals, Whippany, NJ), and included three imaging planes (axial, sagittal and coronal) using T1-W, fat-suppressed T1-W, fatsuppressed T2-W, short tau inversion recovery (STIR) and fatsuppressed proton-density sequences. Within the palmar soft tissues, volar to the second metacarpal, a prominent soft-tissue mass was noted, associated with the flexor digitorum Fig. 2 Coronal T1-weighted images of the right hand show (a) a muscle bundle along the flexor tendon of the second digit (arrows) that is similar in appearance and bulk to the thenar and hypothenar musculature in our patient and (b) a normal hand in an age- and gender-matched control (a 14-year-old girl). No abnormal enhancement was seen in the muscle on post-contrast images
The flexor digitorum superficialis is a large muscle contained in the palmar antebrachial group. Following a normal course, the flexor digitorum superficialis arises from the common flexor origin (having humeral, ulnar and radial components) and extends through the forearm where it separates into deep and superficial components. After passing through the carpal tunnel, the superficial flexor digitorum superficialis tendons insert on the middle and ring fingers and the deep flexor digitorum superficialis tendons insert on the index and long fingers. Three varieties of flexor digitorum superficialis anomalies are described. The digastric type arises in the medial
Pediatr Radiol (2016) 46:293–295
epicondyle in the forearm and crosses the carpal tunnel to insert in the palm. The second type arises from the flexor digitorum superficialis muscle belly in the forearm and extends into the carpal tunnel, but not into the palm. The third type, as seen in our patient, is an intrinsic hand muscle that arises from fibers of the carpal tunnel and inserts on the middle phalanx of the index finger [1]. Anomalous hand muscles are rare and the true incidence is not known. It is important, however, to recognize these normal variants in order to facilitate appropriate management. In many cases, a clinical diagnosis can be challenging and imaging studies are often requested early in the evaluation. This early use of advanced imaging with US, CT or MRI places the burden of diagnosis on the shoulders of the astute radiologist. Although distinguishing these anomalous structures from soft-tissue tumors is crucial, the radiologist should be aware that the muscles could be the cause of the child’s symptoms. Treatment for symptoms associated with accessory hand muscles commonly includes conservative treatment, including pain management and physical therapy. When symptoms are severe or persist with treatment, surgical debulking of the accessory muscle is sometimes needed. In summary, we present a case of an anomalous accessory hand muscle, the flexor digitorum superficialis indicis, in a symptomatic child. Anomalous muscles of the hand can be easily overlooked, even by experienced radiologists, but
295
accurate early identification with radiologic imaging can save the child unnecessary clinical workup (as well as the emotional stress associated with the concern for a tumor) and facilitate prompt and appropriate medical or surgical management. Conflicts of interest None
References 1.
Sookur P, Naraghi A, Bleakney R et al (2008) Accessory muscles: anatomy, symptoms, and radiologic evaluation. Radiographics 28: 481–499 2. Coenen L, Biltjes I (1991) Pseudotumor of the palm due to an anomalous flexor digitorum superficialis muscle belly. J Hand Surg 16A: 1046–1051 3. Dixit SH, Kakar S (2010) An uncommon variation of flexor digitorum superficialis indicis, a case report: anatomic and clinical relevance. Clin Anat 23:889–890 4. Grant S, Due T (1995) Anomalous flexor digitorum superficialis presenting as a painful palmar mass: a case report. Clin Anat 8: 432–433 5. Kostakoglu N, Borman H, Kecik A (1997) Anomalous flexor digitorum superficialis muscle belly: an unusual case of mass in the palm: a case report. Brit J Plast Surg 50:654–656 6. Stephens N, Marques E, Livingston C (2007) Anomalous flexor digitorum superficialis muscle belly presenting as a mass within the palm. Can J Plast Surg 15:44–46
