Clinical Anatomy 28:428–430 (2015)
Letter to the Editor Dynamic Ultrasonography Can Demonstrate the Mechanism of the Palmaris Profundus in Carpal Tunnel Syndrome To The Editor, Clinical Anatomy: In an article by our group (Pirola et al., 2009), we highlighted the clinical significance of the palmaris profundus tendon, a rare anatomic variant, in patients presenting with median nerve compression in the palm. Our group (Pirola et al., 2009) also discussed the anatomic relationships between the median nerve and palmaris profundus tendon resulting in carpal tunnel syndrome (CTS). In a letter to the editor which followed, Pasquale et al. (2010) described a patient with a variant palmaris longus muscle to demonstrate the value of dynamic ultrasound (US) in detecting anatomic variations preoperatively within the carpal tunnel. In this letter, our two groups collaborate to present two patients with median nerve compression at the wrist associated with palmaris profundus on dynamic US to demonstrate the likely mechanisms responsible for the neural symptoms—a feat which cannot be demonstrated with standard MR or CT imaging alone. A 65-year-old man (Case 1) presented with a two month history of bilateral wrist and hand pain accompanied by paresthesias in the thumbs, index, and middle fingers, which he attributed to his exercise regime. Physical examination revealed a positive Tinel’s sign over his wrists with decreased grip strength but no associated atrophy. Electrophysiologic testing demonstrated moderately severe bilateral median neuropathies at the wrist. The patient was referred for sonographically guided carpal tunnel corticosteroid injections, at which time palmaris profundus tendons were detected in both wrists. The variant tendons arose from the flexor digitorum superficialis (FDS) and blended with the distal region of the flexor retinaculum (Fig. 1). As the median nerve approached the carpal tunnel, it moved from a position deep and radial to the palmaris profundus to a position superficial to the palmaris profundus, where it was sandwiched between the palmaris profundus and the more superficially located palmaris longus and flexor retinaculum (Figs. 2A and 2B). The nerve was markedly enlarged and deformed, consistent with compression (Fig. 2B). Since both the palmaris longus and profundus tendons attached distally to the flexor retinaculum, further dynamic median nerve compression occurred as a result of finger or wrist flexion via increased tension in the two palmaris tendons bordering the nerve. As the median nerve entered the carpal tunnel it assumed a position superficial and ulnar to the palmaris profundus (Fig. 2C and Supporting Information Video 1). The neurologic symptoms resolved after corticosteroid injections and modification of the patient’s exercise regimen, and the patient has remained stable as of the time of this letter (2-years posttreatment).
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2015 Wiley Periodicals, Inc.
The second patient is a 35-year old right-handed man (Case 2) who presented with a three month history of paresthesias in the right radial three digits attributed to a recent household move. US examination revealed an enlarged median nerve proximal to the flexor retinaculum and a palmaris profundus. The small accessory tendon arose from the undersurface of the distal FDS muscle, accompanied the median nerve toward the carpal tunnel, and passed closely apposed and superficial to the nerve prior to inserting into the flexor retinaculum. Dynamic US revealed compression of the median nerve during active finger flexion, at which time the nerve assumed a saddleshape as the digital flexor tendons migrated palmarly and the palmaris profundus and flexor retinaculum tightened (Supporting Information Video 2). When the patient relaxed his hand, the median nerve resumed a more normal, oval cross-sectional area. Mild flexor tenosynovitis was also noted. MR imaging performed confirmed the presence of the palmaris profundus and a swollen median nerve just proximal to the cephalad edge of the flexor retinaculum. The patient underwent surgical decompression consisting of resection of the accessory tendon and release of the flexor retinaculum. The postoperative course was uneventful. Whether diagnostic imaging, such as dynamic US, is cost effective in the management of CTS remains controversial (Spinner et al., 2010; Fowler et al., 2014). Nonetheless, the role of preoperative dynamic US as demonstrated by these two cases is quite clear. In both cases, US not only identified an anatomic variant of clinical significance, but also dynamically documented the potential mechanism of median nerve compression. Recent research has highlighted the role of US in identifying anatomic variants and regional anatomy in CTS patients which have implications for clinical disease and may need to be addressed intraoperatively (Cartwright and Walker, 2013). In our two cases, the palmaris profundus contributed to median nerve compression through mirror image mechanisms. In Case 1, the nerve
Additional Supporting Information may be found in the online version of this article. *Correspondence to: Robert J. Spinner, M.D., Mayo Clinic, Gonda 8–214, Rochester, MN 55905, USA. E-mail: [email protected] Received 12 December 2014; Accepted 16 December 2014 Published online 17 February 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ca.22507
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from the FDS. In Case 2, the nerve was statically compressed between the palmaris profundus and underlying flexor tendons; the compression being dynamically exacerbated by the palmar displacement of the finger flexors coupled with increased tension in the palmaris profundus. In both cases, the median nerve was enlarged and demonstrated a kidney shape deformation as a result of compression. In conclusion, the two cases highlight the utility of dynamic US in the evaluation of CTS and provide evidence that symptomatic CTS in the setting of a palmaris profundus is likely mediated by dynamic compression rather than a volumetric effect related to the additional tendon within the carpal tunnel.
Fig. 1. Cross-sectional sonographic image (Case 1) of the median nerve in the forearm just proximal to the carpal tunnel. Green arrows signify the palmaris profundus tendon just distal to its musculotendinous junction within FDS. Note the median nerve (MN) on its radial side. Inset demonstrates transducer positioning to obtain US image. FCR 5 flexor carpi radialis muscle, FDS 5 flexor digitorum superficialis muscle, MED NRV SAX 5 short axis view of median nerve, Top 5 volar/superficial, Bottom 5 dorsal/deep, Left 5 radial (RAD), Right 5 ulnar.
was statically compressed between the palmaris profundus and the combination of the palmaris longus and flexor retinaculum. This compression was dynamically exacerbated by finger flexor activation, which not only caused the normal palmar displacement of the flexor tendons, but also increased tension in the palmaris profundus via its origin
Fig. 2. Cross-sectional sonographic images (Case 1) of the median nerve at the carpal tunnel inlet scanning proximal to distal (A!C). A: The median nerve (MN) starts deep on the radial side of the palmaris profundus tendon (green arrows). B: As the scan moves into the carpal tunnel inlet, the MN moves superficially over tendon, where it is sandwiched between the palmaris profundus (green arrows) and superficially located palmaris longus (PL). The proximal flexor retinaculum is depicted by the horizontal, hyperechoic (bright) tissue lying between the PL and palmaris profundus. Both the PL and
Alper Cesmebasi Department of Neurologic Surgery Mayo Clinic Rochester, Minnesota Department of Anatomical Sciences St George’s University Grenada, West Indies Robert J. Spinner* Department of Neurologic Surgery Mayo Clinic Rochester, Minnesota Jay Smith Department of Physical Medicine and Rehabilitation Mayo Clinic Rochester, Minnesota Carlo Martinoli Cattedra di Radiologia-DISC Universita di Genova Genova, Italy
palmaris profundus attach distally to the same structure—the flexor retinaculum. Note the enlarged MN, demonstrating a kidney shape deformation due to compression. C: The MN eventually has moved superficial and to the ulnar side of the palmaris profundus. Note the enlarged, hypoechoic (i.e., dark) MN characteristic of CTS. FCR 5 flexor carpi radialis; FDS 5 flexor digitorum superficialis; FDP, flexor digitorum profundus. MED NRV SAX 5 short axis view of median nerve, Top 5 volar/superficial, Bottom 5 dorsal/deep, Right 5 radial (RAD), Right 5 ulnar.
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REFERENCES Cartwright MS, Walker FO. 2013. Neuromuscular ultrasound in common entrapment neuropathies. Muscle Nerve 48:696–704. Fowler JR, Munsch M, Tosti R, Hagberg WC, Imbriglia JE. 2014. Comparison of ultrasound and electrodiagnostic testing for diagnosis of carpal tunnel syndrome: Study using a validated clinical tool as the reference standard. J Bone Joint Surg Am 96: e148.
Pasquale AD, Liotta G, Granata G, Martinoli C, Padua L. 2010. A dynamic ultrasonographic evaluation of the palmaris anomalous muscle. Clin Anat 23:328–329. bert-Blouin MN, Amador N, Amrami KK, Spinner RJ. Pirola E, He 2009. Palmaris profundus: One name, several subtypes, and a shared potential for nerve compression. Clin Anat 22:643–648. bert-Blouin MN, Amrami KK. 2010. Dynamic Spinner RJ, He imaging in patients with carpal tunnel syndrome. Clin Anat 23: 330–331.
Letter to the Editor Dynamic Ultrasonography Can Demonstrate the Mechanism of the Palmaris Profundus in Carpal Tunnel Syndrome To The Editor, Clinical Anatomy: In an article by our group (Pirola et al., 2009), we highlighted the clinical significance of the palmaris profundus tendon, a rare anatomic variant, in patients presenting with median nerve compression in the palm. Our group (Pirola et al., 2009) also discussed the anatomic relationships between the median nerve and palmaris profundus tendon resulting in carpal tunnel syndrome (CTS). In a letter to the editor which followed, Pasquale et al. (2010) described a patient with a variant palmaris longus muscle to demonstrate the value of dynamic ultrasound (US) in detecting anatomic variations preoperatively within the carpal tunnel. In this letter, our two groups collaborate to present two patients with median nerve compression at the wrist associated with palmaris profundus on dynamic US to demonstrate the likely mechanisms responsible for the neural symptoms—a feat which cannot be demonstrated with standard MR or CT imaging alone. A 65-year-old man (Case 1) presented with a two month history of bilateral wrist and hand pain accompanied by paresthesias in the thumbs, index, and middle fingers, which he attributed to his exercise regime. Physical examination revealed a positive Tinel’s sign over his wrists with decreased grip strength but no associated atrophy. Electrophysiologic testing demonstrated moderately severe bilateral median neuropathies at the wrist. The patient was referred for sonographically guided carpal tunnel corticosteroid injections, at which time palmaris profundus tendons were detected in both wrists. The variant tendons arose from the flexor digitorum superficialis (FDS) and blended with the distal region of the flexor retinaculum (Fig. 1). As the median nerve approached the carpal tunnel, it moved from a position deep and radial to the palmaris profundus to a position superficial to the palmaris profundus, where it was sandwiched between the palmaris profundus and the more superficially located palmaris longus and flexor retinaculum (Figs. 2A and 2B). The nerve was markedly enlarged and deformed, consistent with compression (Fig. 2B). Since both the palmaris longus and profundus tendons attached distally to the flexor retinaculum, further dynamic median nerve compression occurred as a result of finger or wrist flexion via increased tension in the two palmaris tendons bordering the nerve. As the median nerve entered the carpal tunnel it assumed a position superficial and ulnar to the palmaris profundus (Fig. 2C and Supporting Information Video 1). The neurologic symptoms resolved after corticosteroid injections and modification of the patient’s exercise regimen, and the patient has remained stable as of the time of this letter (2-years posttreatment).
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2015 Wiley Periodicals, Inc.
The second patient is a 35-year old right-handed man (Case 2) who presented with a three month history of paresthesias in the right radial three digits attributed to a recent household move. US examination revealed an enlarged median nerve proximal to the flexor retinaculum and a palmaris profundus. The small accessory tendon arose from the undersurface of the distal FDS muscle, accompanied the median nerve toward the carpal tunnel, and passed closely apposed and superficial to the nerve prior to inserting into the flexor retinaculum. Dynamic US revealed compression of the median nerve during active finger flexion, at which time the nerve assumed a saddleshape as the digital flexor tendons migrated palmarly and the palmaris profundus and flexor retinaculum tightened (Supporting Information Video 2). When the patient relaxed his hand, the median nerve resumed a more normal, oval cross-sectional area. Mild flexor tenosynovitis was also noted. MR imaging performed confirmed the presence of the palmaris profundus and a swollen median nerve just proximal to the cephalad edge of the flexor retinaculum. The patient underwent surgical decompression consisting of resection of the accessory tendon and release of the flexor retinaculum. The postoperative course was uneventful. Whether diagnostic imaging, such as dynamic US, is cost effective in the management of CTS remains controversial (Spinner et al., 2010; Fowler et al., 2014). Nonetheless, the role of preoperative dynamic US as demonstrated by these two cases is quite clear. In both cases, US not only identified an anatomic variant of clinical significance, but also dynamically documented the potential mechanism of median nerve compression. Recent research has highlighted the role of US in identifying anatomic variants and regional anatomy in CTS patients which have implications for clinical disease and may need to be addressed intraoperatively (Cartwright and Walker, 2013). In our two cases, the palmaris profundus contributed to median nerve compression through mirror image mechanisms. In Case 1, the nerve
Additional Supporting Information may be found in the online version of this article. *Correspondence to: Robert J. Spinner, M.D., Mayo Clinic, Gonda 8–214, Rochester, MN 55905, USA. E-mail: [email protected] Received 12 December 2014; Accepted 16 December 2014 Published online 17 February 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ca.22507
Letter to the Editor
429
from the FDS. In Case 2, the nerve was statically compressed between the palmaris profundus and underlying flexor tendons; the compression being dynamically exacerbated by the palmar displacement of the finger flexors coupled with increased tension in the palmaris profundus. In both cases, the median nerve was enlarged and demonstrated a kidney shape deformation as a result of compression. In conclusion, the two cases highlight the utility of dynamic US in the evaluation of CTS and provide evidence that symptomatic CTS in the setting of a palmaris profundus is likely mediated by dynamic compression rather than a volumetric effect related to the additional tendon within the carpal tunnel.
Fig. 1. Cross-sectional sonographic image (Case 1) of the median nerve in the forearm just proximal to the carpal tunnel. Green arrows signify the palmaris profundus tendon just distal to its musculotendinous junction within FDS. Note the median nerve (MN) on its radial side. Inset demonstrates transducer positioning to obtain US image. FCR 5 flexor carpi radialis muscle, FDS 5 flexor digitorum superficialis muscle, MED NRV SAX 5 short axis view of median nerve, Top 5 volar/superficial, Bottom 5 dorsal/deep, Left 5 radial (RAD), Right 5 ulnar.
was statically compressed between the palmaris profundus and the combination of the palmaris longus and flexor retinaculum. This compression was dynamically exacerbated by finger flexor activation, which not only caused the normal palmar displacement of the flexor tendons, but also increased tension in the palmaris profundus via its origin
Fig. 2. Cross-sectional sonographic images (Case 1) of the median nerve at the carpal tunnel inlet scanning proximal to distal (A!C). A: The median nerve (MN) starts deep on the radial side of the palmaris profundus tendon (green arrows). B: As the scan moves into the carpal tunnel inlet, the MN moves superficially over tendon, where it is sandwiched between the palmaris profundus (green arrows) and superficially located palmaris longus (PL). The proximal flexor retinaculum is depicted by the horizontal, hyperechoic (bright) tissue lying between the PL and palmaris profundus. Both the PL and
Alper Cesmebasi Department of Neurologic Surgery Mayo Clinic Rochester, Minnesota Department of Anatomical Sciences St George’s University Grenada, West Indies Robert J. Spinner* Department of Neurologic Surgery Mayo Clinic Rochester, Minnesota Jay Smith Department of Physical Medicine and Rehabilitation Mayo Clinic Rochester, Minnesota Carlo Martinoli Cattedra di Radiologia-DISC Universita di Genova Genova, Italy
palmaris profundus attach distally to the same structure—the flexor retinaculum. Note the enlarged MN, demonstrating a kidney shape deformation due to compression. C: The MN eventually has moved superficial and to the ulnar side of the palmaris profundus. Note the enlarged, hypoechoic (i.e., dark) MN characteristic of CTS. FCR 5 flexor carpi radialis; FDS 5 flexor digitorum superficialis; FDP, flexor digitorum profundus. MED NRV SAX 5 short axis view of median nerve, Top 5 volar/superficial, Bottom 5 dorsal/deep, Right 5 radial (RAD), Right 5 ulnar.
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Letter to the Editor
REFERENCES Cartwright MS, Walker FO. 2013. Neuromuscular ultrasound in common entrapment neuropathies. Muscle Nerve 48:696–704. Fowler JR, Munsch M, Tosti R, Hagberg WC, Imbriglia JE. 2014. Comparison of ultrasound and electrodiagnostic testing for diagnosis of carpal tunnel syndrome: Study using a validated clinical tool as the reference standard. J Bone Joint Surg Am 96: e148.
Pasquale AD, Liotta G, Granata G, Martinoli C, Padua L. 2010. A dynamic ultrasonographic evaluation of the palmaris anomalous muscle. Clin Anat 23:328–329. bert-Blouin MN, Amador N, Amrami KK, Spinner RJ. Pirola E, He 2009. Palmaris profundus: One name, several subtypes, and a shared potential for nerve compression. Clin Anat 22:643–648. bert-Blouin MN, Amrami KK. 2010. Dynamic Spinner RJ, He imaging in patients with carpal tunnel syndrome. Clin Anat 23: 330–331.
