The radial nerve (C5–T1, posterior cord of the brachial plexus) is the most commonly injured nerve in peripheral nerve trauma, primarily serving the extensor compartment of the upper limb. [1-3] Injury classically presents with wrist drop and finger drop with sensory loss over the posterior forearm and dorsal hand. The most common causes are external compression (40%) and humeral fractures (18%), with the arm (spiral groove) being the most frequent site of injury. [1]
1. History
- Mechanism of injury: trauma (fracture, laceration, gunshot wound), compression (sleeping on arm, "Saturday night palsy," crutch use, tourniquet), or repetitive activity [1-2]
- Onset: hyperacute (within 24 hours) in most traumatic and compressive cases; subacute/chronic in entrapment or tumors [1]
- Symptom characterization: inability to extend wrist/fingers, difficulty gripping objects (paradoxically, grip requires wrist extension), numbness/tingling over dorsal hand [2]
- Timing: sudden onset after waking (compression), immediately post-fracture, or progressive (tumor, entrapment)
- Associated symptoms: pain (more common in radial tunnel syndrome), arm swelling (fracture), preceding alcohol/sedative use (Saturday night palsy) [1]
- Important negatives: neck pain, bilateral symptoms, bowel/bladder dysfunction (to exclude cervical myelopathy/radiculopathy)
2. Alarm Features
- Open fracture with nerve deficit — suggests neurotmesis requiring urgent surgical exploration [4]
- Vascular compromise (absent radial pulse, expanding hematoma) — associated with brachial artery injury in humeral fractures
- Progressive weakness or new-onset deficit after fracture fixation — suggests iatrogenic injury [4-5]
- Bilateral wrist drop — consider lead poisoning, multifocal motor neuropathy, or central lesion [6]
- Associated signs of posterior cord or brachial plexus injury (deltoid weakness) — suggests more proximal lesion [6]
- Wrist drop with constitutional symptoms (weight loss, fever) — consider malignancy or nerve sheath tumor [7]
3. Medications
- Relevant contributors to compressive neuropathy: sedatives, alcohol, opioids, general anesthesia (prolonged positioning) — all increase risk of Saturday night palsy [1]
- Neurotoxic medications that may cause generalized peripheral neuropathy (not specific to radial nerve): chemotherapeutics (vincristine, cisplatin, paclitaxel), amiodarone, metronidazole, isoniazid, statins, nitrofurantoin [8-9]
- Common treatments:
- NSAIDs for pain (especially radial tunnel syndrome) [2][10]
- Gabapentin/pregabalin for neuropathic pain [9]
- Corticosteroid injection (diagnostic and therapeutic for radial tunnel syndrome) [10]
- Contraindicated: injection of neurotoxic substances near the nerve; avoid intramuscular injections in the deltoid region on the affected side (reported cause of iatrogenic radial nerve injury) [11]
4. Diet
- No specific dietary triggers for radial nerve injury
- Alcohol excess is a major risk factor for compressive radial neuropathy (Saturday night palsy) and should be addressed [1]
- Nutritional deficiencies (B12, B6, thiamine) can contribute to generalized neuropathy and impair nerve recovery
- Adequate protein intake supports nerve regeneration
5. Review of Systems
- Neurologic: weakness in other distributions (brachial plexus, cervical radiculopathy), bilateral symptoms, gait abnormalities
- Musculoskeletal: arm/forearm pain, history of fracture, joint instability
- Constitutional: weight loss >10% body weight (identified as a risk factor for radial mononeuropathy), fevers, night sweats [1]
- Vascular: cold hand, color changes (compartment syndrome, vascular injury)
- Rheumatologic: joint swelling (synovitis causing PIN compression) [2]
6. Collateral History and Family History
- Witnesses to mechanism (e.g., position during sleep, duration of compression)
- Alcohol or substance use history (critical for Saturday night palsy) [1]
- Occupational history: repetitive pronation/supination, use of crutches, prolonged arm positioning [12]
- Family history of hereditary neuropathy with liability to pressure palsies (HNPP) — autosomal dominant, predisposes to recurrent compressive neuropathies
- Family history of Charcot-Marie-Tooth disease
7. Risk Factors
- Humeral shaft fracture (especially middle-to-distal third) — 8.5–16% incidence of radial nerve palsy [4][10]
- External compression: prolonged arm positioning during sleep, anesthesia, intoxication [1-2]
- Male sex — male predominance in both traumatic and nontraumatic groups [1]
- Diabetes mellitus — increases susceptibility to compressive neuropathy [1]
- Significant weight loss (>10% body weight in 2–3 months) — loss of protective soft tissue [1]
- Excessive alcohol use [1]
- Repetitive forearm pronation/supination — risk for radial tunnel syndrome [10]
- Arm wrestling — 26–28% incidence of radial nerve palsy with humeral shaft fractures [10]
8. Differential Diagnosis
- C7 radiculopathy: wrist drop with radial deviation weakness, but also involves median-innervated muscles (pronator teres, FCR); triceps reflex diminished; neck pain with dermatomal sensory loss [6]
- Posterior cord brachial plexopathy: involves deltoid (axillary nerve) in addition to radial nerve distribution [6]
- Posterior interosseous nerve (PIN) syndrome: finger drop without wrist drop (ECRL spared); no sensory loss; often caused by lipoma or synovitis [2]
- Lateral epicondylitis (tennis elbow): pain without motor weakness; tenderness at lateral epicondyle rather than distal to radial head [10]
- Multifocal motor neuropathy (MMN): chronic progressive finger/wrist extension weakness; conduction block on NCS; treatable with IVIG [1]
- Neuralgic amyotrophy (Parsonage-Turner syndrome): acute severe shoulder/arm pain followed by weakness; may selectively involve PIN [1]
- Lead poisoning: bilateral wrist drop, abdominal pain, basophilic stippling on blood smear
- Central lesion (stroke, brain tumor): upper motor neuron signs, face/leg involvement
9. Past Medical History
- Prior fractures of the humerus or forearm
- Previous episodes of compressive neuropathy (consider HNPP)
- Diabetes mellitus, hypothyroidism
- Malignancy (nerve sheath tumors, metastatic disease) [7]
- Rheumatologic conditions (rheumatoid arthritis — synovitis causing PIN compression)
- Prior surgeries on the arm (iatrogenic injury during ORIF) [4-5]
- Alcohol use disorder
10. Physical Exam
Vital signs: generally normal unless associated polytrauma
Motor examination (localize the lesion level)
Sensory examination
- Posterior forearm and dorsal hand (main trunk lesion) — absent in pure PIN syndrome [2]
- Dorsal radial hand only (superficial radial nerve/handcuff neuropathy) [2]
Special maneuvers
- Tinel sign over spiral groove or radial tunnel
- Maudsley test (resisted middle finger extension) — positive in radial tunnel syndrome [10]
- Resisted forearm supination — pain in radial tunnel syndrome [10]
- Assess for wrist drop with gravity-eliminated and against-gravity testing (MRC grading)
11. Lab Studies
- Routine labs are generally not required for isolated traumatic radial nerve injury
- If etiology unclear:
- CBC, CMP, ESR/CRP (infection, inflammation, malignancy)
- HbA1c or fasting glucose (diabetes screening) [1]
- Lead level (bilateral wrist drop)
- Vitamin B12 with methylmalonic acid
- Serum protein electrophoresis with immunofixation (monoclonal gammopathy) [9]
- TSH
- If MMN suspected: anti-GM1 ganglioside antibodies [1]
12. Imaging
- X-ray of humerus: first-line if fracture suspected; evaluate for mid-to-distal shaft fractures [2][4]
- MRI of the arm/forearm: indicated for suspected space-occupying lesion (lipoma, nerve sheath tumor, ganglion cyst), or to exclude mimicking diagnoses [2][10]
- Ultrasound (neuromuscular): increasingly used for point-of-care evaluation of nerve continuity, compression sites, and space-occupying lesions [10]
- MRI of cervical spine: if C7 radiculopathy is in the differential [6]
- Imaging is unnecessary in classic Saturday night palsy with clear compressive history and expected recovery trajectory
13. Special Tests
Electrodiagnostic studies (EDX) — the cornerstone of evaluation:
- Optimal timing: at least 3–4 weeks post-injury to allow Wallerian degeneration to manifest; fibrillation potentials and positive sharp waves become evident [13-14]
- Nerve conduction studies (NCS): radial motor NCS recording from both EIP and EDC recommended; assess for conduction block across the spiral groove [1]
- Needle EMG: assess radial-innervated muscles (EIP, EDC, brachioradialis, ECRL, triceps) plus non-radial C7 muscles (pronator teres, FCR) and cervical paraspinals to exclude radiculopathy [1]
- Key prognostic EDX findings: brachioradialis recruitment (full = 100% good outcome); preserved CMAP amplitude; conduction block (favorable, suggests demyelination) [3]
The following figure illustrates the temporal evolution of nerve injury pathophysiology and why EDX has limited utility immediately post-injury:
Nerve injury classification (Seddon/Sunderland): [13][15]
14. ECG
- ECG is not routinely indicated for isolated radial nerve injury
- Consider ECG in the setting of polytrauma, crush injury, or if compartment syndrome is suspected (hyperkalemia from rhabdomyolysis)
- If lead poisoning is suspected as a cause of bilateral wrist drop, ECG may show conduction abnormalities
15. Assessment
Clinical summary: Radial nerve injury most commonly presents as acute wrist and finger drop following humeral fracture or external compression. The arm (spiral groove) is the most common site, accounting for 89% of cases in a large series. [1]
Severity stratification
- Neurapraxia (most compressive injuries): excellent prognosis, recovery within 3 months [13][15]
- Axonotmesis: recovery depends on distance to target muscles; rate of 1 mm/day [15-16]
- Neurotmesis: no spontaneous recovery; requires surgical intervention [13][15]
Typical vs. atypical presentations
- Typical: acute wrist/finger drop after fracture or compression, with sensory loss over dorsal hand
- Atypical: isolated finger drop without wrist drop (PIN syndrome), pure pain without weakness (radial tunnel syndrome), chronic progressive weakness (MMN, tumor) [1-2][10]
Complications: joint contractures from prolonged immobilization, chronic neuropathic pain, permanent motor deficit if surgical window missed
16. Treatment Plan
Initial stabilization
- Immobilize any associated fracture
- Cock-up wrist splint (volar) to maintain wrist in 20–30° extension — prevents contracture and improves grip function [2]
Conservative management (first-line for most cases)
- Avoidance of repeat compression [2]
- Physical/occupational therapy: passive ROM to prevent contractures, progressive strengthening as reinnervation occurs
- NSAIDs for pain; gabapentin/pregabalin for neuropathic pain [9-10]
- For radial tunnel syndrome: activity modification, bracing, corticosteroid injection (diagnostic and therapeutic) [10]
- Saturday night palsy: physical therapy is nearly 100% effective at 6 months [2]
Surgical options (when conservative management fails)
- Neurolysis: for lesions in continuity; 98% achieved motor recovery ≥ Grade 3 [17]
- Primary/secondary nerve repair: 83–91% good outcomes [17]
- Nerve grafting (sural nerve graft): for nerve gaps; optimal timing ≤6.9 months post-injury; shorter defect length and more graft cables predict better outcomes [5][18]
- Nerve transfer (median to radial): median nerve branches (FCR, FDS) coapted to PIN and ECRB; M4+ wrist extension in all patients in one series; optimal within 6 months [11]
- Tendon transfer: considered the gold standard for late or irreversible radial nerve palsy; faster recovery but lacks independent finger function [11]
- Early surgical exploration (within 3 weeks): for humeral fracture-associated palsy, recovery rate of 89.8% vs. 77.2% with nonsurgical management and 68.1% with late exploration [4]
Prognosis by timing (humeral fracture-associated palsy): if nerve has not recovered by 7 months, probability of recovery by 18 months is 56%; if not recovered by 1 year, probability drops to 17% [19]
17. Disposition
Admission criteria
- Associated humeral fracture requiring operative fixation
- Open fracture with nerve deficit (urgent surgical exploration)
- Polytrauma
- Vascular compromise
Discharge criteria
- Isolated compressive radial neuropathy (Saturday night palsy) with no fracture
- Stable neurovascular exam
- Adequate pain control and splinting in place
Observation indications
Specialist consultation triggers
- Orthopedic surgery: humeral fracture management
- Hand/peripheral nerve surgery: open injury with nerve transection, no improvement after 3 months of conservative treatment, progressive deficit [2][13]
- Neurology/electrodiagnostic medicine: EDX at 3–4 weeks for prognostication and localization [14]
- Neurosurgery: complex nerve reconstruction, nerve transfer consideration [11][17]
18. Follow Up / Return Precautions
Follow-up timing
- Clinical reassessment at 2–4 weeks for early signs of recovery (Tinel sign advancement)
- EDX at 3–4 weeks post-injury (optimal timing for diagnostic accuracy) [14]
- Repeat clinical and/or EDX assessment at 3 months — if no recovery from suspected neurapraxia, escalate to surgical consultation [13]
- For axonotmetic injuries: serial assessments every 4–6 weeks monitoring for advancing Tinel sign and clinical reinnervation
Symptoms requiring immediate reassessment
- Worsening weakness or new sensory loss
- Increasing pain, swelling, or signs of compartment syndrome
- New deficit after fracture fixation (iatrogenic injury)
- Development of weakness in other nerve distributions
Patient counseling points
- Wear the wrist splint consistently to prevent contractures and maintain hand function
- Avoid positions that compress the arm (do not sleep with arm draped over chair)
- Avoid alcohol excess
- Recovery timeline: neurapraxia typically resolves within 3 months; axonotmesis recovery occurs at ~1 mm/day from the injury site [13][15]
- Most nontraumatic compressive radial neuropathies (~90%) have a good outcome [3]
Expected recovery course: spontaneous recovery occurs in 77–90% of humeral fracture-associated palsies. [4][19] Compressive (Saturday night palsy) injuries have the best prognosis, with demyelinating pathophysiology and expected full recovery. [1][13]
References
1. Radial Mononeuropathy: Clinical and Electrodiagnostic Characteristics in 177 Patients. — Sinthuwong C, Katirji B. Muscle & Nerve. 2026.
2. Peripheral Nerve Entrapment and Injury in the Upper Extremity. — Silver S, Ledford CC, Vogel KJ, Arnold JJ. American Family Physician. 2021.
3. How electrodiagnosis predicts clinical outcome of focal peripheral nerve lesions. — Robinson LR. Muscle & Nerve. 2015.
4. Radial Nerve Palsy Recovery With Fractures of the Humerus: An Updated Systematic Review. — Ilyas AM, Mangan JJ, Graham J. The Journal of the American Academy of Orthopaedic Surgeons. 2020.
5. Management of Radial Nerve Lesions After Trauma or Iatrogenic Nerve Injury: Autologous Grafts and Neurolysis. — Schwaiger K, Abed S, Russe E, et al. Journal of Clinical Medicine. 2020.
6. Distinguishing Radiculopathies From Mononeuropathies. — Robblee J, Katzberg H. Frontiers in Neurology. 2016.
7. Clinical Reasoning: A 65-Year-Old Woman With Cancer History and Wrist Drop. — Merrill R, Puckett M, Morrow WP, et al. Neurology. 2022.
8. Peripheral Neuropathy: Evaluation and Differential Diagnosis. — Castelli G, Desai KM, Cantone RE. American Family Physician. 2020.
9. Peripheral Neuropathy. — Mauermann ML, Staff NP. The Journal of the American Medical Association. 2026.
10. Sports‐related peripheral nerve injuries of the upper limb. — Dutton RA, Norbury J, Colorado B. Muscle & Nerve. 2024.
11. Median to Radial Nerve Transfer: An 8-Year Experience From a Lower-Middle Income Country. — Ahmed KS, Rajput BU, Siddiqui MAI, Nadeem A, Rahman MF. The Journal of Surgical Research. 2023.
12. Occupational nerve injuries. — Hearn SL, Jorgensen SP, Gabet JM, Carter GT. Muscle & Nerve. 2025.
13. Assessment, management, and rehabilitation of traumatic peripheral nerve injuries for non‐surgeons. — Bateman EA, Pripotnev S, Larocerie-Salgado J, Ross DC, Miller TA. Muscle & Nerve. 2025.
14. Optimal timing of needle electromyography to diagnose lesion severity in traumatic radial nerve injury. — Steenbeek ED, Pondaag W, Tannemaat MR, et al. Muscle & Nerve. 2023.
15. Traumatic injury to peripheral nerves. — Robinson LR. Muscle & Nerve. 2022.
16. Peripheral Nerve Reconstruction after Injury: A Review of Clinical and Experimental Therapies. — Grinsell D, Keating CP. BioMed Research International. 2014.
17. Surgical Management and Outcome in Patients With Radial Nerve Lesions. — Kim DH, Kam AC, Chandika P, Tiel RL, Kline DG. Journal of Neurosurgery. 2001.
18. Rehabilitation Outcomes and Prognostic Factors of Nerve Grafting Combined With Exercise Therapy for High-Level Radial Nerve Injury: Results of a Retrospective Study. — Cen Y, Zhao H, Wu L. Injury. 2025.
19. What Is the Probability of Radial Nerve Recovery After Surgical Repair of Humerus Fractures Accounting for Time Since Injury?. — Krijnen NA, Comerci AJ, Head LK, et al. Clinical Orthopaedics and Related Research. 2026.