Injury or compression of the ulnar nerve (C8–T1) often at the elbow (cubital tunnel) or wrist (Guyon's canal), causing impaired hand intrinsic muscles and sensory loss in the ulnar distribution.
Very common entrapment neuropathy (second after carpal tunnel) that can lead to permanent hand dysfunction if untreated. Often appears on exams via classic claw hand deformity or ulnar-sided numbness scenarios.
Intermittent numbness/tingling in the little finger and ulnar half of the ring finger, often worse with prolonged elbow flexion (e.g., holding a phone) or at night. May have aching medial elbow pain.
Typical patient: history of chronic elbow pressure (desk job leaning on elbows, truck drivers, wheelchair use) or repetitive elbow motion; alternatively a cyclist with prolonged pressure on the palms (ulnar tunnel at wrist).
On exam: decreased sensation in ulnar 1½ digits (palmar and dorsal if lesion at elbow), weak finger abduction/adduction (interossei) and reduced grip strength. Froment's sign (thumb flexes when pulling paper) and Wartenberg's sign (little finger held abducted) may be present in advanced cases.
Localize the lesion: if dorsal ulnar hand sensation is preserved, compression is likely at the wrist (Guyon's canal) (dorsal ulnar cutaneous branch branches off proximal to the wrist).
Perform provocative tests: Tinel's sign at the elbow (tapping the funny bone) may reproduce tingling; an elbow flexion test (holding elbow bent ~60 seconds) often elicits symptoms. Always check Froment's sign (weak adductor pollicis) and do a neck exam to exclude a cervical radiculopathy.
Order nerve conduction studies (NCS/EMG) to confirm slowing across the elbow and assess severity. Consider imaging (elbow X-ray for bone spurs, ultrasound or MRI) if a mass, bone deformity, or alternative diagnosis is suspected.
Condition
Distinguishing Feature
C8–T1 cervical radiculopathy
neck or shoulder pain with medial hand numbness; often involves multiple dermatomes (not just ulnar nerve) and neck movements may worsen symptoms
median nerve compression at wrist: numbness of lateral 3½ digits, thenar weakness (ape hand deformity) rather than ulnar distribution
Thoracic outlet syndrome
compression of lower brachial plexus (C8/T1); can mimic ulnar neuropathy but often with vascular signs or whole hand involvement
Conservative (mild cases): Activity modification to avoid prolonged elbow flexion or direct pressure (e.g., use an elbow pad, keep the arm extended at night), plus NSAIDs for inflammation. Nighttime splinting of the elbow in extension is often recommended. Physical therapy and nerve-gliding exercises can also help.
Surgical (for severe or refractory cases): Decompression of the ulnar nerve at the cubital tunnel (often with anterior transposition of the nerve to a new position at the elbow). For ulnar tunnel syndrome at the wrist, surgical release of Guyon's canal is performed. If the nerve is acutely lacerated (e.g., by trauma), prompt surgical repair is indicated.
Mnemonic: DR CUMA – Drop (wrist drop) = Radial nerve, Claw hand = Ulnar nerve, Median nerve = Ape hand.
Ulnar paradox: a proximal lesion (at elbow) causes less clawing than a distal lesion (because the ulnar half of FDP is also paralyzed). In other words, *"the closer to the Paw, the worse the Claw."*
Remember the difference between an ulnar claw and the hand of benediction: Ulnar claw is evident at rest (4th and 5th digits clawed), whereas a median nerve injury is most obvious when making a fist (inability to flex 2nd and 3rd digits, aka Pope's blessing).
Acute trauma (e.g., elbow fracture or deep laceration) with immediate ulnar nerve paralysis → concern for nerve transection or entrapment in bone; requires urgent surgical exploration.
Evidence of severe neuropathy (marked intrinsic hand muscle weakness or wasting, fixed claw deformity, or symptoms persisting >6 weeks despite rest) → indicates high-grade compression; prompt specialist referral for possible surgical release.
Ulnar-sided hand numbness/weakness → suspect ulnar nerve entrapment (cubital tunnel syndrome if at elbow).
Physical exam: test sensation in the ulnar distribution and intrinsic hand muscle strength; perform Tinel's at the elbow or an elbow flexion test to provoke symptoms. Also examine the neck to rule out a cervical radiculopathy.
If symptoms are mild and no motor deficit: start conservative management (avoid elbow flexion/pressure, use padding/splint at night, NSAIDs as needed).
If significant weakness or no improvement after a trial (~6 weeks): obtain electrodiagnostic studies (EMG/NCS) to confirm the diagnosis and pinpoint the compression site.
For persistent or severe cases: proceed with surgical decompression of the ulnar nerve (cubital tunnel release ± anterior transposition at the elbow, or ulnar tunnel release at the wrist).
Middle-aged office worker with intermittent tingling of the 4th and 5th fingers, worse with his elbows bent (holding a phone, resting on desk). Exam shows decreased sensation in those fingers and a positive Tinel sign at the elbow → Cubital tunnel syndrome (ulnar nerve compression at the elbow).
Cyclist with a prolonged history of riding presents with weak grip and numbness in the little finger. There is atrophy in the first dorsal interosseous and a positive Froment sign; dorsal hand sensation is intact → Guyon canal syndrome (ulnar nerve compression at the wrist from handlebar pressure).
Case 1
A 45‑year‑old man has had "pins and needles" in his right ring and little fingers for 3 months, worse at night and when talking on the phone. He also reports a weak grip and has occasionally dropped objects.
Illustration of the elbow joint showing compression of the ulnar nerve at the cubital tunnel (inside of the elbow).
