Updated: 11/12/2022

Ulnar Tunnel Syndrome

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  •  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
          • caused from loss of intrinsics flexing the MCPs and extending the IP joints
        • Allen test
          • helps diagnose ulnar artery thrombosis
      • 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
          • from loss of MP joint flexion power
        • weak pinch
          • from loss of thumb adduction (as much as 70% of pinch strength is lost)
        • Froment sign
          • IP flexion compensating for loss of thumb adduction when attempting to hold a piece of paper
          • loss of MCP flexion and adduction by adductor pollicis (ulnar n.)
          • compensatory IP hyperflexion by FPL (AIN)
        • Jeane's sign
          • a compensatory thumb MCP hyperextension and thumb adduction by EPL (radial n.)
          • compensates for loss of IP extension and thumb adduction by adductor pollicis (ulna n.)
        • Wartenberg sign
          • abduction posturing of the little finger
  • 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
          • as a first line of treatment when symptoms are mild
    • Operative
      • local decompression
        • indications
          • severe symptoms that have failed nonoperative treatment
      • tendon transfers
        • indications
          • correction of clawed fingers
          • loss of power pinch
          • Wartenberg sign (abduction of small finger)
      • carpal tunnel release
        • indications
          • patients diagnosed with both ulnar tunnel syndrome and CTS
  • 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

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(OBQ18.119) A 55-year-old patient presents with numbness and tingling in the right small and ring fingers and associated hand weakness. On examination, there is decreased sensation on the volar, ulnar and radial aspect of the small finger and the volar, and ulnar aspect of the ring finger, but the sensation on the dorsum of the hand is preserved. Symptoms are reproduced with pressure over the wrist during flexion. There is weakness of finger adduction and grip strength, but flexor digitorum profundus strength of the ring and small finger remains preserved. The patient denies any previous trauma to the right hand or wrist. What study would most likely identify the causative lesion?

QID: 213015

MRI of the cervical spine



EMG/NCV of the upper extremity



MRI of the wrist



Carpal tunnel view radiographs



CT and MRI of the elbow



L 2 A

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(SBQ17SE.6) A 26-year-old male construction worker presents with a six-month history of paresthesias in the small and ring fingers. Physical examination reveals weakness of the first dorsal interosseous muscle. An MRI is demonstrated in Figure A. Which additional finding is characteristic of this pathology?

QID: 211171

Abnormal sensation over the dorsal ulnar hand



Wartenberg syndrome



Inability to flex the thumb interphalangeal joint (IPJ) without flexing the distal IPJ joint of the index finger



Thumb and index finger IPJ flexion when attempting to pinch a piece of paper



Inability to flex both the thumb IPJ and index finger IPJ



L 4 A

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(OBQ16.256) A 38-year-old female presents with 8 months of gradual weakness of her right hand. She denies paresthesias, numbness, and pain in the right upper extremity. She has compensatory thumb interphalangeal flexion during key pinch and intact two point discrimination. She has a negative Tinel's sign at the wrist and elbow. Electromyography (EMG) shows normal sensory conduction velocities but delayed motor conduction to the first dorsal interosseous muscle. Figure A and B show MRI images of pre and post contrast, respectively. Ultrasound is shown in Figure C. What is the next best step?

QID: 9018

Biopsy of the mass



Cyst excision



MRI of cervical spine



Excision of the hook of hamate



Cubital tunnel release



L 2 B

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(OBQ10.132) A 72-year-old female complains of progressive weakness with grasp and key pinch in her left hand. Physical exam of the hand is significant for decreased sensation on the volar aspect of the fourth and fifth digits. Dorsal sensation throughout the hand is normal. A clinical photo displaying bilateral key pinch is shown in Figure A. What is the most likely cause of compression?

QID: 3225

Accessory head of the FPL



Flexor carpi ulnaris



Osborne's ligament



Ganglion within Guyon's canal



Anconeus epitrochlearis



L 3 B

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Evidence (9)
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