Summary Ulnar Tunnel Syndrome is a compressive neuropathy of the ulnar nerve at the level of the wrist (Guyon's canal), most commonly due to a ganglion cyst. Diagnosis can be made clinically with paresthesias of the small and ring finger with intrinsic weakness with a Tinel's sign over Guyon's canal. Treatment involves a course of conservative management with splinting, and surgical decompression in the presence of a compressive lesion (i.e ganglion) or continued symptoms. Epidemology Incidence less common than cubital tunnel syndrome Risk factors cyclists (also known as handlebar palsy) Etiology Pathoanatomy causes of compression include ganglion cyst (80% of nontraumatic causes) lipoma repetitive trauma ulnar artery thrombosis or aneurysm hook of hamate fracture or nonunion pisiform dislocation inflammatory arthritis fibrous band, muscle or bony anomaly congenital bands palmaris brevis hypertrophy idiopathic Anatomy Guyon’s canal course is approximately 4 cm long begins at the proximal extent of the transverse carpal ligament and ends at the aponeurotic arch of the hypothenar muscles contents ulnar nerve bifurcates into the superficial sensory and deep motor branches boundaries and zones (see table below) Boundaries of Guyon's canal Floor Transverse carpal ligament, hypothenar muscles Roof Volar carpal ligament Ulnar border Pisiform and pisohamate ligament, abductor digiti minimi muscle Radial border Hook of hamate Zones of Guyon's canal Zone Location Causes of Compression Symptoms Zone 1 Proximal to bifurcation of the nerve Ganglia and hook of hamate fractures Mixed motor and sensory Zone 2 Surrounds deep motor branch Ganglia and hook of hamate fractures Motor only Zone 3 Surrounds superficial sensory branch Ulnar artery thrombosis or aneurysm Sensory only Deep branch of the ulnar nerve innervates all of the interosseous muscles and the 3rd and 4th lumbricals. Innervates the hypothenar muscles, the adductor pollicis, and the medial head (deep) of the flexor pollicis brevis (FPB) Classification Presentation varies based on location of compression within Guyon's canal and may be Motor only Sensory only Mixed Motor & Sensory Presentation Presentation varies based on location of compression within Guyon's canal and may be pure motor pure sensory mixed motor and sensory Symptoms pain and paresthesias in ulnar 1-1/2 digits weakness to intrinsics, ring and small finger digital flexion or thumb adduction Physical exam inspection & palpation clawing of ring and little fingers login to view 1 more bullet Allen test login to view 1 more bullet neurovascular exam ulnar nerve palsy results in paralysis of the intrinsic muscles (adductor pollicis, deep head FPB, interossei, and lumbricals 3 and 4) weakened grasp login to view 1 more bullet weak pinch login to view 1 more bullet Froment sign login to view 3 more bullets Jeane's sign login to view 2 more bullets Wartenberg sign login to view 1 more bullet Imaging Radiographs useful to evaluate hook of hamate fractures CT scan useful to evaluate hook of hamate fractures MRI useful to evaluate for a ganglion cysts a gradient echo MRI will also show an ulnar artery aneurysm Doppler US or arteriogram useful to diagnosis ulnar artery thrombosis and aneurysm Studies NCS and EMG helpful in establishing diagnosis and prognosis threshold for diagnosis conduction velocity <50 m/sec across elbow low amplitudes of sensory nerve action potentials and compound muscle action potentials Differential Cubital tunnel syndrome compared to ulnar tunnel syndrome, cubital tunnel demonstrates less clawing sensory deficit to dorsum of the hand motor deficit to ulnar-innervated extrinsic muscles Tinel sign at the elbow positive elbow flexion test Diagnosis Clinical and EMG/NCS diagnosis confirmed with history, physical exam and EMG/NCS MRI studies used to confirm presense of compressive lesion (i.e ganglion) Treatment Nonoperative activity modification, NSAIDS and splinting indications login to view 1 more bullet Operative local decompression indications login to view 1 more bullet tendon transfers indications login to view 3 more bullets carpal tunnel release indications login to view 1 more bullet Techniques Local surgical decompression release hypothenar muscle origin decompress ganglion cysts resect hook of hamate vascular treatment of ulnar artery thombosis explore and release all three zones in Guyon's canal Tendon transfers correct claw fingers possible grafts include ECRL, ECRB, palmaris longus tendons must pass volar to transverse metacarpal ligament in order to flex the proximal phalanx attach with either a two or four-tailed graft to the A2 pulley of the ring and small fingers restore power pinch Smith transfer using ECRB or FDS of ring finger restore adduction of small finger transfer ulnar insertion of EDM to A1 pulley or radial collateral ligament of the small finger Complications Recurrence