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US of Nerve Entrapments in Osteofibrous Tunnels of the Upper and Lower Limbs¹

¹ From the Department of Radiology R, University of Genoa, Largo Rosanna Benzi 8, I-16132 Genoa, Italy (C.M., L.E.D.); the Division of Radiodiagnostics, Hôpital Cantonal Universitaire, Geneva, Switzerland (S.B.); the Radiology Service, Ospedale Santa Corona, Pietra Ligure, Italy (N.G.); the Istituto Giannina Gaslini, Genoa, Italy (M.V.); and the Division of Neurology, E.O. Ospedali Galliera, Genoa, Italy (S.S.). Recipient of a Certificate of Merit award for a scientific exhibit at the 1999 RSNA scientific assembly. Received February 7, 2000; revision requested March 16 and received May 4; accepted May 11. Address correspondence to C.M. (e-mail: martinoli@zeus.newnetworks.it).

View larger version (109K): [in a new window]   Figure 1. Carpal tunnel. Longitudinal 5-12-MHz US scan obtained in an asymptomatic 42-year-old man shows the hypoechoic median nerve (MN), which lies just underneath the flexor retinaculum (arrowheads) and superficial to the hyperechoic flexor tendons (FT). Note that the nerve angles away from the transducer on entering the tunnel. L = lunate, R = distal radius.

View larger version (35K): [in a new window]   Figure 2a. Carpal and Guyon tunnels. (a, b) Drawing (a) and corresponding transverse 5-12-MHz US scan (b) show the proximal level of the carpal tunnel delimited by the pisiform (P) and the scaphoid (S). (c, d) Drawing (c) and corresponding transverse 5-12-MHz US scan (d) show the distal level of the carpal tunnel delimited by the hook of the hamate (H) and the tubercle of the trapezium (T). The flexor retinaculum (medium gray region in a and c; open arrowheads in b and d) forms the roof of the carpal tunnel and the floor of the Guyon tunnel. The palmar carpal ligament (dark gray region in a) forms the volar boundary of the Guyon tunnel. The flexor tendons and median nerve (MN) extend through the carpal tunnel, with the nerve lying palmar and radial. At the level of the pisiform, the ulnar nerve (U) courses medial to the ulnar artery (solid arrowhead) within the Guyon tunnel. At the level of the hamate, the ulnar nerve divides into two terminal branches, a deep motor branch (curved arrow) and a superficial sensory branch (straight arrow). * = flexor pollicis longus tendon, * = flexor carpi radialis tendon.

View larger version (74K): [in a new window]   Figure 2b. Carpal and Guyon tunnels. (a, b) Drawing (a) and corresponding transverse 5-12-MHz US scan (b) show the proximal level of the carpal tunnel delimited by the pisiform (P) and the scaphoid (S). (c, d) Drawing (c) and corresponding transverse 5-12-MHz US scan (d) show the distal level of the carpal tunnel delimited by the hook of the hamate (H) and the tubercle of the trapezium (T). The flexor retinaculum (medium gray region in a and c; open arrowheads in b and d) forms the roof of the carpal tunnel and the floor of the Guyon tunnel. The palmar carpal ligament (dark gray region in a) forms the volar boundary of the Guyon tunnel. The flexor tendons and median nerve (MN) extend through the carpal tunnel, with the nerve lying palmar and radial. At the level of the pisiform, the ulnar nerve (U) courses medial to the ulnar artery (solid arrowhead) within the Guyon tunnel. At the level of the hamate, the ulnar nerve divides into two terminal branches, a deep motor branch (curved arrow) and a superficial sensory branch (straight arrow). * = flexor pollicis longus tendon, * = flexor carpi radialis tendon.

View larger version (31K): [in a new window]   Figure 2c. Carpal and Guyon tunnels. (a, b) Drawing (a) and corresponding transverse 5-12-MHz US scan (b) show the proximal level of the carpal tunnel delimited by the pisiform (P) and the scaphoid (S). (c, d) Drawing (c) and corresponding transverse 5-12-MHz US scan (d) show the distal level of the carpal tunnel delimited by the hook of the hamate (H) and the tubercle of the trapezium (T). The flexor retinaculum (medium gray region in a and c; open arrowheads in b and d) forms the roof of the carpal tunnel and the floor of the Guyon tunnel. The palmar carpal ligament (dark gray region in a) forms the volar boundary of the Guyon tunnel. The flexor tendons and median nerve (MN) extend through the carpal tunnel, with the nerve lying palmar and radial. At the level of the pisiform, the ulnar nerve (U) courses medial to the ulnar artery (solid arrowhead) within the Guyon tunnel. At the level of the hamate, the ulnar nerve divides into two terminal branches, a deep motor branch (curved arrow) and a superficial sensory branch (straight arrow). * = flexor pollicis longus tendon, * = flexor carpi radialis tendon.

View larger version (84K): [in a new window]   Figure 2d. Carpal and Guyon tunnels. (a, b) Drawing (a) and corresponding transverse 5-12-MHz US scan (b) show the proximal level of the carpal tunnel delimited by the pisiform (P) and the scaphoid (S). (c, d) Drawing (c) and corresponding transverse 5-12-MHz US scan (d) show the distal level of the carpal tunnel delimited by the hook of the hamate (H) and the tubercle of the trapezium (T). The flexor retinaculum (medium gray region in a and c; open arrowheads in b and d) forms the roof of the carpal tunnel and the floor of the Guyon tunnel. The palmar carpal ligament (dark gray region in a) forms the volar boundary of the Guyon tunnel. The flexor tendons and median nerve (MN) extend through the carpal tunnel, with the nerve lying palmar and radial. At the level of the pisiform, the ulnar nerve (U) courses medial to the ulnar artery (solid arrowhead) within the Guyon tunnel. At the level of the hamate, the ulnar nerve divides into two terminal branches, a deep motor branch (curved arrow) and a superficial sensory branch (straight arrow). * = flexor pollicis longus tendon, * = flexor carpi radialis tendon.

View larger version (111K): [in a new window]   Figure 3a. Carpal tunnel syndrome in a 65-year-old woman with an aberrant flexor muscle of the index finger. Longitudinal (a, b) and transverse (c, d) 5-12-MHz US scans of the carpal tunnel show the effects of flexion (a, c) and extension (b, d) of the index finger. With the fingers flexed, an anomalous muscle belly (*) lies proximal to the entrance of the carpal tunnel. Progressive extension of the index finger pushes the muscle inside the tunnel, thus causing compression of the median nerve (MN). Flexion and extension of the other digits did not affect the position of this muscle. FT = flexor tendon, P = pisiform.

View larger version (125K): [in a new window]   Figure 3b. Carpal tunnel syndrome in a 65-year-old woman with an aberrant flexor muscle of the index finger. Longitudinal (a, b) and transverse (c, d) 5-12-MHz US scans of the carpal tunnel show the effects of flexion (a, c) and extension (b, d) of the index finger. With the fingers flexed, an anomalous muscle belly (*) lies proximal to the entrance of the carpal tunnel. Progressive extension of the index finger pushes the muscle inside the tunnel, thus causing compression of the median nerve (MN). Flexion and extension of the other digits did not affect the position of this muscle. FT = flexor tendon, P = pisiform.

View larger version (117K): [in a new window]   Figure 3c. Carpal tunnel syndrome in a 65-year-old woman with an aberrant flexor muscle of the index finger. Longitudinal (a, b) and transverse (c, d) 5-12-MHz US scans of the carpal tunnel show the effects of flexion (a, c) and extension (b, d) of the index finger. With the fingers flexed, an anomalous muscle belly (*) lies proximal to the entrance of the carpal tunnel. Progressive extension of the index finger pushes the muscle inside the tunnel, thus causing compression of the median nerve (MN). Flexion and extension of the other digits did not affect the position of this muscle. FT = flexor tendon, P = pisiform.

View larger version (117K): [in a new window]   Figure 3d. Carpal tunnel syndrome in a 65-year-old woman with an aberrant flexor muscle of the index finger. Longitudinal (a, b) and transverse (c, d) 5-12-MHz US scans of the carpal tunnel show the effects of flexion (a, c) and extension (b, d) of the index finger. With the fingers flexed, an anomalous muscle belly (*) lies proximal to the entrance of the carpal tunnel. Progressive extension of the index finger pushes the muscle inside the tunnel, thus causing compression of the median nerve (MN). Flexion and extension of the other digits did not affect the position of this muscle. FT = flexor tendon, P = pisiform.

View larger version (131K): [in a new window]   Figure 4a. Carpal tunnel syndrome in a 37-year-old man with a persistent median artery of the forearm. (a) Transverse 5-12-MHz gray-scale US scan obtained at the distal radius shows the proximal bifurcation of the median nerve (arrows) and the median artery of the forearm (arrowhead) located between the two nerve branches. (b) Longitudinal color Doppler US scan shows the course of the anomalous artery (arrow) through the carpal tunnel, superficial to the flexor tendons (FT) and deep to the flexor retinaculum (arrowheads). The presence of the artery causes disturbances in nerve function.

View larger version (114K): [in a new window]   Figure 4b. Carpal tunnel syndrome in a 37-year-old man with a persistent median artery of the forearm. (a) Transverse 5-12-MHz gray-scale US scan obtained at the distal radius shows the proximal bifurcation of the median nerve (arrows) and the median artery of the forearm (arrowhead) located between the two nerve branches. (b) Longitudinal color Doppler US scan shows the course of the anomalous artery (arrow) through the carpal tunnel, superficial to the flexor tendons (FT) and deep to the flexor retinaculum (arrowheads). The presence of the artery causes disturbances in nerve function.

View larger version (122K): [in a new window]   Figure 5a. Carpal tunnel syndrome in a 52-year-old man with rheumatoid arthritis. Longitudinal (a) and transverse (b) 10-13-MHz US images obtained at the distal radius show abnormally increased effusion (*) surrounding the flexor tendons (FT), resulting in palmar displacement and compression of the median nerve (MN) at the entrance to the tunnel (arrow).

View larger version (127K): [in a new window]   Figure 5b. Carpal tunnel syndrome in a 52-year-old man with rheumatoid arthritis. Longitudinal (a) and transverse (b) 10-13-MHz US images obtained at the distal radius show abnormally increased effusion (*) surrounding the flexor tendons (FT), resulting in palmar displacement and compression of the median nerve (MN) at the entrance to the tunnel (arrow).

View larger version (139K): [in a new window]   Figure 6a. Carpal tunnel syndrome in a 40-year-old woman with a large intramuscular hemangioma extending through the flexor muscles of the forearm down to the carpal tunnel. The patient underwent release of the retinaculum 6 months earlier. (a, b) Longitudinal (a) and transverse (b) 5-13-MHz color Doppler US scans of the proximal carpal tunnel show an enlarged median nerve (arrows) containing abnormal vessels. FT = flexor tendon. (c) Coronal T2-weighted MR image (repetition time msec/echo time msec = 2,000/72) of the forearm shows the hemangioma (arrowheads) as a large hyperintense lesion involving the ventral aspect of the forearm, as well as the carpal tunnel. (d, e) Axial T2-weighted (d) and fat-suppressed T2-weighted (e) MR images (1,920/72) of the wrist show increased signal intensity in the epineurium surrounding the fascicles of the median nerve (arrow). This appearance is due to the presence of abnormal vessels within the nerve substance.

View larger version (125K): [in a new window]   Figure 6b. Carpal tunnel syndrome in a 40-year-old woman with a large intramuscular hemangioma extending through the flexor muscles of the forearm down to the carpal tunnel. The patient underwent release of the retinaculum 6 months earlier. (a, b) Longitudinal (a) and transverse (b) 5-13-MHz color Doppler US scans of the proximal carpal tunnel show an enlarged median nerve (arrows) containing abnormal vessels. FT = flexor tendon. (c) Coronal T2-weighted MR image (repetition time msec/echo time msec = 2,000/72) of the forearm shows the hemangioma (arrowheads) as a large hyperintense lesion involving the ventral aspect of the forearm, as well as the carpal tunnel. (d, e) Axial T2-weighted (d) and fat-suppressed T2-weighted (e) MR images (1,920/72) of the wrist show increased signal intensity in the epineurium surrounding the fascicles of the median nerve (arrow). This appearance is due to the presence of abnormal vessels within the nerve substance.

View larger version (98K): [in a new window]   Figure 6c. Carpal tunnel syndrome in a 40-year-old woman with a large intramuscular hemangioma extending through the flexor muscles of the forearm down to the carpal tunnel. The patient underwent release of the retinaculum 6 months earlier. (a, b) Longitudinal (a) and transverse (b) 5-13-MHz color Doppler US scans of the proximal carpal tunnel show an enlarged median nerve (arrows) containing abnormal vessels. FT = flexor tendon. (c) Coronal T2-weighted MR image (repetition time msec/echo time msec = 2,000/72) of the forearm shows the hemangioma (arrowheads) as a large hyperintense lesion involving the ventral aspect of the forearm, as well as the carpal tunnel. (d, e) Axial T2-weighted (d) and fat-suppressed T2-weighted (e) MR images (1,920/72) of the wrist show increased signal intensity in the epineurium surrounding the fascicles of the median nerve (arrow). This appearance is due to the presence of abnormal vessels within the nerve substance.

View larger version (153K): [in a new window]   Figure 6d. Carpal tunnel syndrome in a 40-year-old woman with a large intramuscular hemangioma extending through the flexor muscles of the forearm down to the carpal tunnel. The patient underwent release of the retinaculum 6 months earlier. (a, b) Longitudinal (a) and transverse (b) 5-13-MHz color Doppler US scans of the proximal carpal tunnel show an enlarged median nerve (arrows) containing abnormal vessels. FT = flexor tendon. (c) Coronal T2-weighted MR image (repetition time msec/echo time msec = 2,000/72) of the forearm shows the hemangioma (arrowheads) as a large hyperintense lesion involving the ventral aspect of the forearm, as well as the carpal tunnel. (d, e) Axial T2-weighted (d) and fat-suppressed T2-weighted (e) MR images (1,920/72) of the wrist show increased signal intensity in the epineurium surrounding the fascicles of the median nerve (arrow). This appearance is due to the presence of abnormal vessels within the nerve substance.

View larger version (121K): [in a new window]   Figure 6e. Carpal tunnel syndrome in a 40-year-old woman with a large intramuscular hemangioma extending through the flexor muscles of the forearm down to the carpal tunnel. The patient underwent release of the retinaculum 6 months earlier. (a, b) Longitudinal (a) and transverse (b) 5-13-MHz color Doppler US scans of the proximal carpal tunnel show an enlarged median nerve (arrows) containing abnormal vessels. FT = flexor tendon. (c) Coronal T2-weighted MR image (repetition time msec/echo time msec = 2,000/72) of the forearm shows the hemangioma (arrowheads) as a large hyperintense lesion involving the ventral aspect of the forearm, as well as the carpal tunnel. (d, e) Axial T2-weighted (d) and fat-suppressed T2-weighted (e) MR images (1,920/72) of the wrist show increased signal intensity in the epineurium surrounding the fascicles of the median nerve (arrow). This appearance is due to the presence of abnormal vessels within the nerve substance.

View larger version (100K): [in a new window]   Figure 7a. Carpal tunnel syndrome in a 48-year-old woman with multiple myeloma and deposits of amyloid in the deep carpal tunnel. Longitudinal (a) and transverse (b) 5-12-MHz US scans show the bulk of the amyloid substance (*) in the confined space of the tunnel, compressing the flexor tendons (FT) and median nerve (arrow) against the flexor retinaculum (arrowheads). Note the volar bulging of the retinaculum in b.

View larger version (86K): [in a new window]   Figure 7b. Carpal tunnel syndrome in a 48-year-old woman with multiple myeloma and deposits of amyloid in the deep carpal tunnel. Longitudinal (a) and transverse (b) 5-12-MHz US scans show the bulk of the amyloid substance (*) in the confined space of the tunnel, compressing the flexor tendons (FT) and median nerve (arrow) against the flexor retinaculum (arrowheads). Note the volar bulging of the retinaculum in b.

View larger version (82K): [in a new window]   Figure 8a. Carpal tunnel syndrome in a 43-year-old man with perilunate dorsal dislocation of the wrist. Longitudinal 7.5-10-MHz US scan (a) and corresponding T2-weighted MR image (1,880/70) (b) of the carpal tunnel show the median nerve (arrowheads) compressed by a displaced lunate (L). Within the carpal tunnel, the lunate is prominent and has a crescentic profile. C = capitate, R = radius, * = compression point.

View larger version (73K): [in a new window]   Figure 8b. Carpal tunnel syndrome in a 43-year-old man with perilunate dorsal dislocation of the wrist. Longitudinal 7.5-10-MHz US scan (a) and corresponding T2-weighted MR image (1,880/70) (b) of the carpal tunnel show the median nerve (arrowheads) compressed by a displaced lunate (L). Within the carpal tunnel, the lunate is prominent and has a crescentic profile. C = capitate, R = radius, * = compression point.

View larger version (90K): [in a new window]   Figure 9a. Cubital tunnel. (a) Drawing of the medial aspect of the elbow shows the course of the ulnar nerve (dark gray region) in the cubital tunnel. At the condylar groove, the nerve passes between the medial epicondyle and the olecranon, just deep to the cubital tunnel retinaculum and the arcuate ligament (light gray region) between the humeral and ulnar origins (*) of the flexor carpi ulnaris muscle (FCU). (b, c) Transverse 5-12-MHz US scans of the proximal tunnel (b) and distal tunnel (c) show the normal relationship of the ulnar nerve (arrow) to the medial epicondyle (ME) and the two heads of the flexor carpi ulnaris muscle (*). O = olecranon.

View larger version (105K): [in a new window]   Figure 9b. Cubital tunnel. (a) Drawing of the medial aspect of the elbow shows the course of the ulnar nerve (dark gray region) in the cubital tunnel. At the condylar groove, the nerve passes between the medial epicondyle and the olecranon, just deep to the cubital tunnel retinaculum and the arcuate ligament (light gray region) between the humeral and ulnar origins (*) of the flexor carpi ulnaris muscle (FCU). (b, c) Transverse 5-12-MHz US scans of the proximal tunnel (b) and distal tunnel (c) show the normal relationship of the ulnar nerve (arrow) to the medial epicondyle (ME) and the two heads of the flexor carpi ulnaris muscle (*). O = olecranon.

View larger version (92K): [in a new window]   Figure 9c. Cubital tunnel. (a) Drawing of the medial aspect of the elbow shows the course of the ulnar nerve (dark gray region) in the cubital tunnel. At the condylar groove, the nerve passes between the medial epicondyle and the olecranon, just deep to the cubital tunnel retinaculum and the arcuate ligament (light gray region) between the humeral and ulnar origins (*) of the flexor carpi ulnaris muscle (FCU). (b, c) Transverse 5-12-MHz US scans of the proximal tunnel (b) and distal tunnel (c) show the normal relationship of the ulnar nerve (arrow) to the medial epicondyle (ME) and the two heads of the flexor carpi ulnaris muscle (*). O = olecranon.

View larger version (101K): [in a new window]   Figure 10a. Cubital tunnel syndrome in a 65-year-old man with a history of trauma to the elbow and heterotopic ossification in the cubital tunnel area. Longitudinal 7.5-10-MHz US scan (a) and axial computed tomographic (CT) scan (b) show an ossicle (arrow), which causes compression and reactive enlargement of the ulnar nerve (arrowheads) within the cubital tunnel. ME = medial epicondyle, O = olecranon.

View larger version (115K): [in a new window]   Figure 10b. Cubital tunnel syndrome in a 65-year-old man with a history of trauma to the elbow and heterotopic ossification in the cubital tunnel area. Longitudinal 7.5-10-MHz US scan (a) and axial computed tomographic (CT) scan (b) show an ossicle (arrow), which causes compression and reactive enlargement of the ulnar nerve (arrowheads) within the cubital tunnel. ME = medial epicondyle, O = olecranon.

View larger version (106K): [in a new window]   Figure 11a. Cubital tunnel syndrome in a 47-year-old woman with posttraumatic changes in the elbow resulting in cubitus valgus. Longitudinal 5-12-MHz US scan (a) and transverse 5-12-MHz US scans obtained at the distal arm (b) and within the cubital tunnel (c) show abrupt narrowing of the ulnar nerve (UN) between the thickened floor of the tunnel (*) and the retinaculum (arrowheads). Proximal to the tunnel, the nerve appears swollen and hypoechoic with an absent fascicular pattern.

View larger version (111K): [in a new window]   Figure 11b. Cubital tunnel syndrome in a 47-year-old woman with posttraumatic changes in the elbow resulting in cubitus valgus. Longitudinal 5-12-MHz US scan (a) and transverse 5-12-MHz US scans obtained at the distal arm (b) and within the cubital tunnel (c) show abrupt narrowing of the ulnar nerve (UN) between the thickened floor of the tunnel (*) and the retinaculum (arrowheads). Proximal to the tunnel, the nerve appears swollen and hypoechoic with an absent fascicular pattern.

View larger version (105K): [in a new window]   Figure 11c. Cubital tunnel syndrome in a 47-year-old woman with posttraumatic changes in the elbow resulting in cubitus valgus. Longitudinal 5-12-MHz US scan (a) and transverse 5-12-MHz US scans obtained at the distal arm (b) and within the cubital tunnel (c) show abrupt narrowing of the ulnar nerve (UN) between the thickened floor of the tunnel (*) and the retinaculum (arrowheads). Proximal to the tunnel, the nerve appears swollen and hypoechoic with an absent fascicular pattern.

View larger version (99K): [in a new window]   Figure 12a. Guyon tunnel syndrome in a 54-year-old man with a pisotriquetrum ganglion. Transverse 5-12-MHz US scan (a) and axial CT arthrogram (b) show a rounded, hypoechoic ganglion (*), which displaces the ulnar artery (curved arrow) and compresses the ulnar nerve (straight arrow) against the pisiform (P). T = triquetrum.

View larger version (87K): [in a new window]   Figure 12b. Guyon tunnel syndrome in a 54-year-old man with a pisotriquetrum ganglion. Transverse 5-12-MHz US scan (a) and axial CT arthrogram (b) show a rounded, hypoechoic ganglion (*), which displaces the ulnar artery (curved arrow) and compresses the ulnar nerve (straight arrow) against the pisiform (P). T = triquetrum.

View larger version (40K): [in a new window]   Figure 13a. Common peroneal nerve at the fibular neck. (a) Drawing of the anterolateral aspect of the leg shows the course of the common peroneal nerve (dark gray region) and its superficial and deep branches. The light gray region represents the insertion of the peroneus longus muscle. (b, c) Transverse 5-12-MHz US scans show the common peroneal nerve (arrow) before (b) and after (c) winding around the fibular neck. Note the close relationship of the nerve to the osseous surface of the fibula (F).

View larger version (115K): [in a new window]   Figure 13b. Common peroneal nerve at the fibular neck. (a) Drawing of the anterolateral aspect of the leg shows the course of the common peroneal nerve (dark gray region) and its superficial and deep branches. The light gray region represents the insertion of the peroneus longus muscle. (b, c) Transverse 5-12-MHz US scans show the common peroneal nerve (arrow) before (b) and after (c) winding around the fibular neck. Note the close relationship of the nerve to the osseous surface of the fibula (F).

View larger version (121K): [in a new window]   Figure 13c. Common peroneal nerve at the fibular neck. (a) Drawing of the anterolateral aspect of the leg shows the course of the common peroneal nerve (dark gray region) and its superficial and deep branches. The light gray region represents the insertion of the peroneus longus muscle. (b, c) Transverse 5-12-MHz US scans show the common peroneal nerve (arrow) before (b) and after (c) winding around the fibular neck. Note the close relationship of the nerve to the osseous surface of the fibula (F).

View larger version (55K): [in a new window]   Figure 14. Common peroneal nerve entrapment by a ganglion in a 54-year-old man. Longitudinal 5-12-MHz US scan of the posterolateral knee shows a ganglion (*) that expands along the common peroneal nerve (arrowheads), thus leading to a compressive syndrome. The ganglion can be differentiated from the nerve substance on the basis of its cystic structure. F = fibula.

View larger version (38K): [in a new window]   Figure 15a. Tarsal tunnel. (a) Drawing of the medial aspect of the ankle shows the course of the tibial nerve (dark gray region) and its terminal branches, the medial and lateral plantar nerves and the calcaneal nerve, in the tarsal tunnel. Light gray region = flexor retinaculum tendon. (b) Transverse 5-12-MHz US scan of the retromalleolar region shows the retinaculum (arrowheads) and tibial nerve (arrow) close to the posterior tibial artery (A) and veins (V). FDL = flexor digitorum longus tendon. (c) Transverse 5-12-MHz US scan of the medial heel shows the medial and lateral plantar nerves (arrows) and calcaneal nerve (arrowhead). A = posterior tibial artery, FHL = flexor hallucis longus tendon, V = posterior tibial vein.

View larger version (113K): [in a new window]   Figure 15b. Tarsal tunnel. (a) Drawing of the medial aspect of the ankle shows the course of the tibial nerve (dark gray region) and its terminal branches, the medial and lateral plantar nerves and the calcaneal nerve, in the tarsal tunnel. Light gray region = flexor retinaculum tendon. (b) Transverse 5-12-MHz US scan of the retromalleolar region shows the retinaculum (arrowheads) and tibial nerve (arrow) close to the posterior tibial artery (A) and veins (V). FDL = flexor digitorum longus tendon. (c) Transverse 5-12-MHz US scan of the medial heel shows the medial and lateral plantar nerves (arrows) and calcaneal nerve (arrowhead). A = posterior tibial artery, FHL = flexor hallucis longus tendon, V = posterior tibial vein.

View larger version (110K): [in a new window]   Figure 15c. Tarsal tunnel. (a) Drawing of the medial aspect of the ankle shows the course of the tibial nerve (dark gray region) and its terminal branches, the medial and lateral plantar nerves and the calcaneal nerve, in the tarsal tunnel. Light gray region = flexor retinaculum tendon. (b) Transverse 5-12-MHz US scan of the retromalleolar region shows the retinaculum (arrowheads) and tibial nerve (arrow) close to the posterior tibial artery (A) and veins (V). FDL = flexor digitorum longus tendon. (c) Transverse 5-12-MHz US scan of the medial heel shows the medial and lateral plantar nerves (arrows) and calcaneal nerve (arrowhead). A = posterior tibial artery, FHL = flexor hallucis longus tendon, V = posterior tibial vein.

View larger version (101K): [in a new window]   Figure 16a. Tarsal tunnel syndrome in a 61-year-old woman with a tibiotalar ganglion. Transverse 10-13-MHz US scan (a) and coronal T2-weighted MR image (2,000/80) (b) show a large ganglion (*) at the posteromedial ankle that displaces and expands around the tibial nerve (arrow), thus sustaining a compressive syndrome. T = talus.

View larger version (113K): [in a new window]   Figure 16b. Tarsal tunnel syndrome in a 61-year-old woman with a tibiotalar ganglion. Transverse 10-13-MHz US scan (a) and coronal T2-weighted MR image (2,000/80) (b) show a large ganglion (*) at the posteromedial ankle that displaces and expands around the tibial nerve (arrow), thus sustaining a compressive syndrome. T = talus.

View larger version (115K): [in a new window]   Figure 17a. Tarsal tunnel syndrome in a 32-year-old man with posttraumatic bone changes at the posteromedial ankle. (a) Longitudinal 10-13-MHz US scan shows focal fusiform thickening and a hypoechoic appearance of the tibial nerve (arrowheads) in the tarsal tunnel. (b) Transverse US scan obtained during eversion and dorsiflexion of the ankle shows anterior displacement of the tibial nerve (arrow) against a prominent bone (*). The nerve appears swollen and hypoechoic in comparison with its normal appearance (Fig 15b). A = posterior tibial artery, V = posterior tibial vein. (c) Axial CT scan shows a prominent bone spur (*) at the posteromedial aspect of the talus.

View larger version (105K): [in a new window]   Figure 17b. Tarsal tunnel syndrome in a 32-year-old man with posttraumatic bone changes at the posteromedial ankle. (a) Longitudinal 10-13-MHz US scan shows focal fusiform thickening and a hypoechoic appearance of the tibial nerve (arrowheads) in the tarsal tunnel. (b) Transverse US scan obtained during eversion and dorsiflexion of the ankle shows anterior displacement of the tibial nerve (arrow) against a prominent bone (*). The nerve appears swollen and hypoechoic in comparison with its normal appearance (Fig 15b). A = posterior tibial artery, V = posterior tibial vein. (c) Axial CT scan shows a prominent bone spur (*) at the posteromedial aspect of the talus.

View larger version (119K): [in a new window]   Figure 17c. Tarsal tunnel syndrome in a 32-year-old man with posttraumatic bone changes at the posteromedial ankle. (a) Longitudinal 10-13-MHz US scan shows focal fusiform thickening and a hypoechoic appearance of the tibial nerve (arrowheads) in the tarsal tunnel. (b) Transverse US scan obtained during eversion and dorsiflexion of the ankle shows anterior displacement of the tibial nerve (arrow) against a prominent bone (*). The nerve appears swollen and hypoechoic in comparison with its normal appearance (Fig 15b). A = posterior tibial artery, V = posterior tibial vein. (c) Axial CT scan shows a prominent bone spur (*) at the posteromedial aspect of the talus.

View larger version (55K): [in a new window]   Figure 18a. Morton neuroma. (a) Drawing of the forefoot shows the site of entrapment of the interdigital nerve (dark gray region) underneath the edge of the transverse intermetatarsal ligament (light gray region). (b, c) Transverse (b) and longitudinal (c) 5-12-MHz US scans, obtained with the transducer over the dorsal aspect of the metatarsal heads in a 44-year-old woman, show a Morton neuroma (arrow) between the second metatarsal (II) and third metatarsal (III). The lesion is hypoechoic and fusiform. The small interdigital nerve (arrowheads) is seen proximal to the mass. IV = fourth metatarsal.

View larger version (95K): [in a new window]   Figure 18b. Morton neuroma. (a) Drawing of the forefoot shows the site of entrapment of the interdigital nerve (dark gray region) underneath the edge of the transverse intermetatarsal ligament (light gray region). (b, c) Transverse (b) and longitudinal (c) 5-12-MHz US scans, obtained with the transducer over the dorsal aspect of the metatarsal heads in a 44-year-old woman, show a Morton neuroma (arrow) between the second metatarsal (II) and third metatarsal (III). The lesion is hypoechoic and fusiform. The small interdigital nerve (arrowheads) is seen proximal to the mass. IV = fourth metatarsal.

View larger version (100K): [in a new window]   Figure 18c. Morton neuroma. (a) Drawing of the forefoot shows the site of entrapment of the interdigital nerve (dark gray region) underneath the edge of the transverse intermetatarsal ligament (light gray region). (b, c) Transverse (b) and longitudinal (c) 5-12-MHz US scans, obtained with the transducer over the dorsal aspect of the metatarsal heads in a 44-year-old woman, show a Morton neuroma (arrow) between the second metatarsal (II) and third metatarsal (III). The lesion is hypoechoic and fusiform. The small interdigital nerve (arrowheads) is seen proximal to the mass. IV = fourth metatarsal.