ConditionBrain & nerves
Radial Nerve Injury (Radial Nerve Palsy)
A radial nerve injury is damage to the radial nerve, which runs down the back of the arm and controls the muscles that straighten the elbow, wrist and fingers. The classic sign is wrist drop: being unable to lift the wrist or straighten the fingers, often with numbness on the back of the hand near the thumb. Common causes are pressure on the upper arm during deep sleep ("Saturday night palsy"), fractures of the upper arm bone, and crutch misuse. Most compression injuries recover within weeks to months.
Also called: Radial nerve palsy, radial neuropathy, wrist drop, Saturday night palsy, honeymoon palsy
At a glance
- What it is
- Damage to the radial nerve anywhere from the armpit to the forearm.
- Classic sign
- Wrist drop: weakness lifting the wrist and straightening the fingers and thumb.
- Common causes
- Pressure during sleep or intoxication, upper arm (humerus) fractures, crutches, tight casts or tourniquets.
- Diagnosis
- Examination, nerve conduction studies and EMG, and imaging after injuries.
- Treatment
- A cock-up wrist splint, physical therapy and time; surgery for nerves that are cut or do not recover.
When to get help
Call 911 or go to the ER
- Sudden weakness of one hand or arm with face droop, speech difficulty or leg weakness (possible stroke): call 911 or your local emergency number
- An arm injury with deformity, severe pain, or a cold, pale hand
See a doctor within a day or two
- Wrist drop after a fracture of the upper arm or elbow
- New wrist drop or finger weakness with no clear pressure cause
- Wrist drop that develops after a cast, splint or tight bandage is applied
Book a routine appointment
- Wrist drop after sleeping on the arm that is not improving after 2 to 3 weeks
- Aching pain on the outer forearm below the elbow with no weakness (possible radial tunnel syndrome)
- Numbness on the back of the hand near the thumb from a tight watch or handcuffs
Anatomy: where the radial nerve can be injured
The radial nerve comes from the brachial plexus (see brachial plexus injury) in the neck and armpit, winds around the back of the upper arm bone (humerus) in the spiral groove, then crosses the elbow and splits into a motor branch (the posterior interosseous nerve) and a sensory branch to the back of the hand.
| Site of injury | Typical causes | Features |
|---|---|---|
| Armpit (axilla) | Crutches pressing into the armpit | Weak elbow straightening (triceps) plus wrist drop and numbness |
| Upper arm (spiral groove) | Saturday night palsy, humerus fractures, injections, tourniquets | Wrist drop, finger drop, numbness on back of hand; triceps usually spared |
| Elbow and forearm (posterior interosseous nerve) | Elbow fractures or dislocations, ganglion cysts, tumors, repetitive forearm use | Finger drop with partially preserved wrist lift, no numbness |
| Forearm (radial tunnel) | Repetitive gripping and twisting | Aching forearm pain without weakness |
| Wrist (superficial radial nerve) | Tight watches, handcuffs, casts | Numbness or tingling only, on the back of the thumb and hand |
Causes
- Compression: sleeping with the arm draped over a chair back, especially after alcohol or sedatives ("Saturday night palsy"), or with a partner's head on the arm ("honeymoon palsy"); prolonged positions during surgery
- Fractures: humerus shaft fractures cause radial nerve palsy in roughly 1 in 10 cases; elbow fractures and dislocations, especially in children
- Crutches used incorrectly, pressing into the armpit
- Tight casts, tourniquets or blood pressure cuffs
- Cuts and penetrating injuries
- Tumors, cysts and lipomas pressing on the nerve
- Medical causes: peripheral neuropathy from diabetes, vasculitis, multifocal motor neuropathy and rarely lead poisoning
Symptoms
- wrist drop: inability to lift the hand at the wrist
- finger drop: inability to straighten the fingers at the knuckles
- weakness extending the thumb
- weak grip, because the wrist cannot be held in a stable position
- numbness or tingling on the back of the hand, thumb, index and middle fingers
- weakness straightening the elbow if the injury is high in the arm
- pain in some cases, especially after trauma
Diagnosis
- Examination: testing wrist, finger and thumb extension, elbow strength, sensation and reflexes; checking other nerves
- Nerve conduction studies and EMG: locate the injury, show its severity and help predict recovery; most useful after about 3 weeks
- Ultrasound or MRI of the nerve: to look for compression, a cut nerve or a mass
- X-rays after injuries
- Brain or neck imaging if a stroke or a nerve root problem (cervical radiculopathy) is possible
Treatment
Conservative treatment
Most compression injuries and many fracture-related injuries recover without surgery.
- Cock-up wrist splint: keeps the wrist raised, improving grip and preventing overstretching of weak muscles
- Dynamic splint that assists finger extension
- Physical and occupational therapy: range of motion to prevent stiffness, then strengthening as the nerve recovers
- Avoid further pressure on the arm, and fix crutch technique
- Pain relief for nerve pain if needed
Surgery
- Nerve exploration and repair: for cut nerves (for example, open fractures or lacerations) or nerves that show no signs of recovery after about 3 to 6 months
- Release of compression: from tumors, cysts or fibrous bands
- Tendon transfers: redirecting working forearm muscles to restore wrist and finger extension when the nerve does not recover
Recovery time
- Mild compression (neurapraxia): typically recovers in days to 2 to 3 months
- More severe damage (axonotmesis): the nerve regrows at roughly 1 mm a day (about 2.5 cm or 1 inch a month), so recovery can take several months
- Cut nerve (neurotmesis): needs surgical repair; recovery is slower and often incomplete
Most radial nerve palsies after humerus fractures recover on their own.
Frequently asked questions
What are the symptoms of radial nerve injury?
The main symptom is wrist drop, an inability to lift the wrist or straighten the fingers and thumb. There may also be numbness or tingling on the back of the hand near the thumb, and weak grip. High injuries also weaken elbow straightening.
What is Saturday night palsy?
Saturday night palsy is radial nerve compression caused by sleeping with the upper arm pressed against a hard edge, such as a chair back, often after drinking alcohol or taking sedatives. It causes wrist drop and usually recovers within weeks to a few months.
How long does a radial nerve injury take to heal?
Mild compression injuries usually recover in a few weeks to 3 months. More severe injuries can take 6 months or more, as nerves regrow about 1 inch a month. Cut nerves need surgery and may not recover fully.
Is wrist drop permanent?
Usually not. Most wrist drop caused by compression or fractures improves on its own. If there is no recovery after 3 to 6 months, nerve surgery or tendon transfers can restore much of the lost function.
How is radial nerve palsy treated?
Treatment usually includes a wrist splint, physical therapy to keep joints flexible and strengthen muscles, and avoiding pressure on the nerve. Surgery is used for cut nerves, compression from a mass, or when recovery does not occur.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Orthopaedic Surgeons: Radial tunnel syndrome; Humerus shaft fractures
- American Society for Surgery of the Hand: Radial nerve palsy
- MedlinePlus: Radial nerve dysfunction
- National Institute of Neurological Disorders and Stroke: Peripheral neuropathy
- American Association of Neuromuscular and Electrodiagnostic Medicine: Radial neuropathy