Ulnar Nerve Palsy: Causes, Symptoms, and Acupuncture Treatment

Ulnar nerve palsy is a syndrome of muscle paralysis in the distribution of the ulnar nerve, caused by various factors that injure or compress the ulnar nerve.

The ulnar nerve is a mixed nerve composed of motor, sensory, and autonomic nerve fibers. It originates from the C8 and T1 spinal cord segments and gives rise to the following four branches:

1. Muscular Branch

In the upper third of the forearm, it gives off a branch that innervates the flexor carpi ulnaris, producing flexion and adduction of the hand, and the flexor digitorum profundus, which flexes the distal phalanges of the 4th and 5th fingers.

II. Palmar Cutaneous Branch

It branches from the ulnar nerve at the middle third of the forearm and descends to supply the skin of the hypothenar region and the area slightly proximal to it.

3. Dorsal Hand Branch (手背支)

From the junction of the middle and lower third of the forearm, the ulnar nerve emerges to the dorsum of the hand and divides into five dorsal digital nerves, which supply the skin on the ulnar side of the 3rd, 4th, and 5th fingers.

IV. Palm Branch

It is further divided into a superficial branch and a deep branch. The superficial branch innervates the palmaris brevis, which pulls the skin toward the palmar aponeurosis. The deep branch innervates the adductor pollicis, enabling thumb adduction; the abductor digiti minimi, which abducts the little finger; the flexor digiti minimi brevis, which flexes the proximal phalanx of the fifth finger; and the opponens digiti minimi, which draws (the little finger into opposition).

The opponens digiti minimi draws the little finger to the center of the palm for opposition. The flexor pollicis brevis flexes the thumb. The four lumbricals flex the metacarpophalangeal (MCP) joints (proximal phalanges) of the 2nd to 5th fingers and extend the interphalangeal (IP) joints (middle and distal phalanges). The interossei, comprising the dorsal and palmar interossei, also flex the MCP joints of the 2nd to 5th fingers and extend the IP joints. The dorsal interossei abduct the 2nd to 4th fingers (spreading them apart), while the palmar interossei adduct the 2nd, 4th, and 5th fingers back to the midline.

Common causes of ulnar nerve palsy include compression at the elbow, fracture of the distal humerus (e.g., olecranon fracture), dislocation of the elbow or shoulder joint, tumor, inflammation, and leprosy. Among these, compression within the cubital tunnel—cubital tunnel syndrome—is the most common.

**Diagnostic Key Points**

The clinical manifestations primarily include radial deviation of the wrist, with weakness in wrist flexion and adduction of the hand; the fourth and fifth fingers show weakness in flexion, with the fingers positioned in abduction, separated from each other, and exhibiting a distinct claw-like deformity. Due to difficulty in both adduction and abduction, gripping objects between the fingers becomes problematic. Prolonged paralysis leads to atrophy of the lumbricals, interossei, and hypothenar muscles. The atrophied dorsum of the hand takes on a fence-like appearance, hence the term “fence sign.” In severe cases, the paper-clip test is positive.

Treatment

1. Acupoints and Needling Methods

1. HT3 (Shaohai) on the affected side: Located in the depression between the ulnar end of the cubital crease and the medial epicondyle of the humerus when the elbow is flexed. Use a 30-gauge, 2-cun filiform needle. After routine local disinfection, insert approximately 1.8 cun towards LI11 (Quchi). Needling sensation: local distension and pain, or a radiating sensation extending to the little finger.

2. **HT7 (Shenmen) on the affected side**: locate the point on the wrist crease, on the radial side of the flexor carpi ulnaris tendon. Use a 32-gauge, 1.5 cun filiform needle. After routine local disinfection, insert the needle about 1.2 cun along the bony crevice at the ulnar border below the palmar crease. Needling sensation: local distension and soreness.

3. **Baxie Points (EX-UE9)** (4 points on the affected side): Located at the junction of the red and white flesh in the interdigital folds on the dorsum of the hand. Using four 32-gauge, 1.5 cun filiform needles. After routine local disinfection, insert horizontally along the interosseous spaces toward the wrist, approximately 1.3 cun deep. Needling sensation: Local distension and pain.

2. Methods

The patient is seated. The above acupoints are needled according to the method with electroacupuncture applied. The needles are retained for 40 minutes before removal. Treatment is given once daily, with 10 sessions constituting one course. After a 5-day rest, the next course begins.

【Commentary】

Ulnar nerve paralysis treated with the aforementioned method plus electroacupuncture generally yields favorable results. However, the outcome depends mainly on the severity and duration of the injury. For patients with mild damage (compression or irritation) and a short duration, the treatment period is relatively brief and the effect is good. For those with severe damage (direct nerve injury), a longer duration, and the presence of muscle atrophy or reduced function within the ulnar nerve’s innervation area, a longer course of treatment is required, though the results remain quite satisfactory. After recovery, patients should be advised to avoid or minimize pressure on the elbow during daily work or any activities, and to regularly perform hand exercises to enhance restored hand function.

Etiology: What Causes Ulnar Nerve Palsy

Ulnar nerve palsy arises from damage or compression of the ulnar nerve along its anatomical course. The most common mechanism is entrapment at the elbow, specifically within the cubital tunnel, where the nerve lies superficially and is vulnerable to repetitive flexion, prolonged leaning, or direct trauma. Fractures of the medial epicondyle or elbow dislocation can also precipitate injury. In the wrist, compression within Guyon’s canal—often from repetitive use of hand tools, ganglion cysts, or fractures of the hamate—constitutes another frequent cause. Additional etiologies include systemic conditions such as diabetes mellitus or alcoholism, which predispose to peripheral neuropathy, and space-occupying lesions like tumors or hematomas. Less commonly, the nerve may be affected by iatrogenic factors during surgical procedures, including elbow arthroscopy or fracture fixation. Understanding what causes ulnar nerve palsy is essential for prompt diagnosis and targeted intervention, as the nerve’s mixed motor and sensory composition means that prolonged compression leads to irreversible damage. A thorough history focusing on occupational risks, recreational activities (e.g., cycling), and preceding trauma guides clinical suspicion. Anatomical variants, such as a persistent epitrochleoanconeus muscle, can also contribute to chronic compression. Finally, inflammatory arthritides like rheumatoid arthritis may cause synovial hypertrophy, further narrowing the cubital tunnel. Thus, the etiological spectrum is broad, ranging from acute mechanical injury to chronic degenerative or systemic processes, all of which culminate in functional disruption of the ulnar nerve. Recognizing these diverse triggers allows clinicians to address the root cause early and mitigate long-term morbidity.

Clinical Presentation: Symptoms of Ulnar Nerve Palsy

The clinical hallmarks of ulnar nerve palsy reflect the nerve’s distribution to intrinsic hand muscles and the sensory territory of the little finger and ulnar half of the ring finger. Early symptoms typically include intermittent ulnar nerve palsy hand numbness and paresthesias along the fourth and fifth digits, often exacerbated by elbow flexion or prolonged pressure on the ulnar aspect of the palm. As the condition progresses, motor deficits emerge, manifested by weakness of finger abduction and adduction, loss of pinch strength, and the classic “claw hand” deformity, where the fourth and fifth metacarpophalangeal joints are hyperextended and the interphalangeal joints are flexed. Patients may report difficulty with fine motor tasks, such as typing, gripping objects, or buttoning shirts. Sensory loss can become constant and may extend to the hypothenar eminence and dorsum of the hand. In chronic cases, muscle wasting, particularly of the first dorsal interosseous and hypothenar muscles, becomes apparent. It is important to distinguish symptoms of ulnar nerve palsy from more proximal nerve entrapments, such as cervical radiculopathy or brachial plexopathy, through careful physical examination including Tinel’s sign at the elbow or wrist and Froment’s sign for thumb adductor weakness. Nerve conduction studies and electromyography confirm the diagnosis and localize the lesion. The constellation of sensory disturbances and progressive motor loss underscores the need for early recognition; whereas isolated numbness may be reversible, advanced muscle weakness often signals irreversible axonal injury. Therefore, any persistent or worsening ulnar nerve palsy hand numbness should prompt immediate evaluation to prevent permanent functional impairment.

Management: Treatment for Ulnar Nerve Palsy

Management of ulnar nerve palsy is stratified according to severity, etiology, and chronicity. For mild, intermittent symptoms without motor deficits, conservative measures are first-line. These include activity modification (avoiding prolonged elbow flexion or direct pressure), ergonomic adjustments, and nocturnal splinting to keep the elbow in slight extension. Physical therapy focusing on nerve gliding exercises and strengthening of spared muscles can alleviate symptoms. Pharmacological options such as nonsteroidal anti-inflammatory drugs or, in neuropathic pain, gabapentin may be considered. When conservative therapy fails or when motor weakness or muscle atrophy is present, surgical decompression is indicated. Cubital tunnel release, either in situ or with anterior transposition of the nerve, relieves compression at the elbow; similarly, Guyon’s canal release addresses wrist-level entrapment. Postoperative care involves gradual mobilization and continued rehabilitation. For severe or chronic cases with established claw hand deformity, additional reconstructive procedures, such as tendon transfers to restore finger abduction or thumb adduction, may be necessary. The optimal treatment for ulnar nerve palsy thus hinges on timely intervention: early decompression yields excellent recovery, while delayed surgery often results in incomplete resolution of motor and sensory deficits. Long-term outcomes also depend on addressing underlying causes, such as optimizing glycemic control in diabetic patients or managing occupational risk factors. Overall, a multidisciplinary approach combining surgical and rehabilitative techniques maximizes functional recovery and minimizes disability. Regular follow-up with nerve conduction studies can monitor regeneration. Patients should be counseled that sensory symptoms—including ulnar nerve palsy hand numbness—generally improve more fully than motor function, highlighting the critical window for effective intervention.