• Clinical science

Peripheral nerve injuries


Peripheral nerve injuries include a variety of conditions in which one or more peripheral nerves are damaged, leading to neurological deficits distal to the level of the lesion. Possible causes include systemic diseases (e.g., diabetes, autoimmune disease) and localized damage (e.g., trauma, compression, tumors). Peripheral nerve injuries may occur as isolated neurological conditions or, more commonly, in association with soft tissue, vascular, and/or skeletal damage. The clinical presentation may vary from sensory deficits to motor loss or a combination of both. Diagnosis is based on clinical evaluation, imaging techniques (x-ray, CT/MRI), and electrodiagnostic exams (e.g., nerve conduction study, EMG). Observation and conservative treatment (e.g., activity modification, splinting, electrical stimulation) are indicated in most closed injuries, which show a high rate of spontaneous recovery. Patients with open injuries or long disease courses may require surgical treatment. The recovery from peripheral nerve injury is often incomplete and patients may suffer from chronic pain.

Types of nerve fibers

Nerve fibers Myelination Impulse conduction velocity (m/s) Afferent fibers Efferent fibers
A (Ia, Ib) 100
  • Ia: primary afferent fibers of the muscle spindle
  • Ib: golgi-tendon organ
(II) 50
  • Pressure and fine touch sensations
  • Secondary afferent fibers of the muscle spindle
  • Muscle spindle
(III) 15
B 7
C (IV) - 1

Types of nerve damage

Classification of peripheral nerve injury assists in determining prognosis and choosing a treatment strategy.

  • Neuropraxia
    • Compression injury; causing temporary disruption of nerve conduction
    • The whole nerve remains structurally intact.
    • Good prognosis with complete recovery of nerve function
  • Axonotmesis
    • The axon is damaged but the perineurium and epineurium remain intact.
    • Leads to central chromatolysis
      • Definition: The reaction of a neuronal cell body in response to an axonal injury.
      • Characteristics
        • Swelling of the neuronal body
        • Dispersion of the Nissl bodies
        • Displacement of the nucleus to the periphery
      • Function: These changes reflect an increase in the protein synthesis in an effort to restore the integrity of the damaged axon.
    • Results in Wallerian degeneration
      • Definition: An active neuronal degeneration process in response to axonal injury.
      • Characteristics
        • Initially retained electrical excitability of axonal distal to the injury, lasting up to 36 hours
        • Progressive degeneration of distal segment cytoskeleton with dissolution of axonal membrane
        • Degradation of residual myelin sheath by macrophages and Schwann cells
        • Proximal stump either stays in place or retracts slightly; ultimately, the stump will sprout regenerative nervous fibers that aim to reinnervate the distal tissues
        • Efficiency in the peripheral nervous system is significantly higher than in the central nervous system
      • Function
        • To clear axonal debris and prevent scarring
        • Facilitate targeted reinnervation of tissues previously innervated by that axon before injury
    • Good chance of at least partial recovery
  • Neurotmesis
    • Complete nerve transection
    • Connective sheath damage
    • Chances of recovery very poor without surgical repair
  • Traumatic neuroma: benign, painful nodular thickening caused by nerve regeneration at the site of different forms of nerve injury


Nerve injuries in the upper body

Brachial plexus injuries

Erb palsy

  • Injury to the upper trunk of the brachial plexus (C5–C6)
  • Etiology
    • Excessive lateral flexion of the neck
      • Trauma (e.g., falling on the head and shoulder in a motorcycle accident)
      • Birth injury: excessive lateral traction on the neck during delivery.
  • Clinical features
    • Weakness of muscles in the C5 and C6 myotomes → flexed wrist with an extended forearm and internally rotated and adducted arm (waiter's tip posture)
    • Asymmetric Moro reflex in infants
    • Sensory loss in the C5 and C6 dermatomes (thumb and lateral surface of the forearm and arm)
  • Treatment
    • Immobilization in flexion and external rotation with an abduction brace
    • Physiotherapy, potentially with neuromuscular electrical stimulation
    • Surgery for severe nerve damage or prolonged cases

Klumpke palsy

  • Injury to the lower trunk of the brachial plexus (C8–T1)
  • Etiology
    • Hyperabduction of the arm
      • Trauma (e.g., breaking a fall by grabbing a branch)
      • Birth injury: excessive traction on the arm during delivery
    • Compression of the lower trunk of brachial plexus (subacute to chronic onset)
  • Clinical features
    • Weakness of muscles in the C8 and T1 myotomes (intrinsic hand muscles) → total claw hand
    • Absent grasp reflex in infants
    • Sensory loss in the C8 and T1 myotomes (little finger and medial surface of the forearm and arm)
    • Pre-ganglionic Horner syndrome if injury occurs proximal to the white ramus communicans
    • Decreased peripheral pulses if subclavian vessels are compressed by a Pancoast tumor or cervical rib (see thoracic outlet syndrome)
  • Treatment
    • Splinting the hand to correct the claw hand
    • Physiotherapy, potentially with neuromuscular electrical stimulation
    • Surgery for severe nerve damage

Peripheral nerve injuries in the upper extremity

Axillary nerve injury

Musculocutaneous nerve injury

  • Nerve roots involved: C5–C7
  • Etiology
    • Trauma
    • Upper trunk compression
  • Clinical presentation

Peripheral nerve injuries in the cervicothoracic region

Injured nerve

Innervated muscles

Common causes

Neurological deficits

Suprascapular nerve injury

  • Compression
    • Entrapment of the nerve within the suprascapular notch
    • Paralabral ganglion cyst
    • Thickening and/or bony ossification of the overlying superior transverse scapular ligament
  • Major or repetitive trauma
  • Limited adduction, abduction, and external rotation of the arm
  • Shoulder instability (due to paralysis of rotator cuff muscles)

Thoracodorsal nerve injury

  • Latissimus dorsi: limited shoulder retraction, impaired adduction and internal rotation of the arm
  • Teres major: limited internal rotation and adduction of the arm

Long thoracic nerve injury

  • Axillary surgery (e.g., lymph node dissection during mastectomy)
  • Stab wounds
  • Carrying a heavy backpack for a long time
  • Medial winging of the scapula, impaired abduction of the arm beyond 90°

Dorsal scapular nerve injury

  • Isolated injury is uncommon, usually accompanies injury to the scalene muscles
  • Lateral winging of the scapula

Phrenic nerve injury

"C3, 4, 5 keeps the diaphragm alive"


Nerve injuries in the lower body

Injured nerve

Nerve roots

Common causes

Neurological deficits

Superior gluteal nerve injury
  • L4–S1
  • Iatrogenic injury due to intramuscular injections in superomedial region
Inferior gluteal nerve injury
  • L5–S2
  • Motor deficit

Femoral nerve injury

  • L2–L4
  • Direct injury (trauma)
  • Prolonged pressure on the nerve: psoas hematoma, aortic or iliac aneurysms or tumors
  • Iatrogenic: pelvic, abdominal, or spinal surgery; femoral line placement.
Lateral femoral cutaneous nerve injury (meralgia paresthetica)
  • L2–L4
  • Compression at the level of the inguinal ligament, caused by:
    • Increased intra-abdominal pressure (e.g., pregnancy, obesity, ascites)
    • External compression (e.g., tight belts, pants, or compression dressings)
    • Local compression (e.g., tumors, hematomas)
  • Sensory deficit: pain and paresthesias on the lateral surface of the anterior thigh
    • Can be improved by wearing looser clothing and/or losing weight
Obturator nerve injury
  • Sensory deficit: medial thigh
  • Motor deficit: paralysis of hip adductors
Sciatic nerve injury
  • L4–S3
Tibial nerve injury
  • Sensory deficit: sensory loss over sole of the foot (see Morton's metatarsalgia)
  • Motor deficit: paralysis of foot flexors → inability to walk on the toes or balls of the feet; inability to invert foot
Common peroneal nerve injury
  • L4–S2
  • Fracture of the fibular head
  • Compression: tight casts, sitting cross-legged, Lithotomy position during surgery
Sural nerve lesion
  • L4–S3
  • Sensory deficit: posterolateral the lower leg, the lateral border of the foot, and a small area under the heel

TIPPED = tibial nerve injury versus peroneal nerve injury: TIP = Tibial → damaged foot Inversion, Plantarflexion; PED = Peroneal → damaged foot Eversion, Dorsiflexion



The diagnosis of peripheral nerve injuries is based on a thorough clinical history, neurological examination, and, in some cases, diagnostic tests (e.g., x-ray if fracture is suspected)

  • Imaging
    • Plain x-rays: detection of compression or transection occurring due to dislocated bone or fracture segments
    • CT/MRI: evaluation of causes like nerve tumors, avulsions, and focal soft tissue pathologies
  • Electrodiagnostic studies
    • Nerve conduction study/neurography
    • Needle electromyography (EMG)


Nerve repair

Conservative treatment

  • Observation and expectant management in closed injuries of the nerve with a high rate of spontaneous recovery
  • Activity modification (e.g., avoid sports or activities that increase likelihood of further nerve injury)
  • Splinting: prevents stiffness and contractures of joints, supports residual nerve functionality and reinnervation
  • Electrical stimulation: supports the regeneration of the proximal axons and reinnervation of the denervated muscles after surgical nerve repair
  • Drug therapy: treatment of chronic neuropathic pain following peripheral nerve injury (e.g., gabapentin); in combination with surgical treatment to enhance remyelination and motor regeneration (e.g., lithium)
  • Analgesia: infiltration with local anesthetics

Surgical repair

  • Indications
    • Open, non-contaminated, sharp injuries; concomitant vascular injuries → immediate surgical exploration and repair
    • Open, contaminated injuries; postreduction palsy → early surgical exploration and repair (within 3 weeks)
    • Patients without clinical or electromyographic signs of spontaneous recovery → delayed surgical exploration and repair (within 3 months)
  • Procedures
    • Nerve repair (neurorrhaphy): reconstruction of nerve continuity
    • Tendon transfer: A tendon from a sufficiently powerful muscle is redirected towards another tendon in order to restore its motion and function.
    • Nerve transfer: An intact healthy nerve is redirected towards a denervated nerve in order to restore the innervation of its target organ.


  • 1. Le T, Bhushan V,‎ Sochat M, Chavda Y, Zureick A. First Aid for the USMLE Step 1 2018. New York, NY: McGraw-Hill Medical; 2017.
  • 2. John P. Rossiter, Alan C. Jackson. Pathology. Elsevier; 2013: pp. 351–386.
  • 3. Stephenson RO. Radiation-Induced Brachial Plexopathy. In: Radiation-Induced Brachial Plexopathy. New York, NY: WebMD. http://emedicine.medscape.com/article/316497-clinical. Updated March 10, 2015. Accessed February 16, 2017.
  • 4. Abbasi D. Traumatic Anterior Shoulder Instability (TUBS). http://www.orthobullets.com/sports/3050/traumatic-anterior-shoulder-instability-tubs. Updated January 1, 2017. Accessed February 16, 2017.
  • 5. Anlauf K. Axillar Nerve Injury. http://www.physio-pedia.com/Axillary_Nerve_Injury. Accessed February 16, 2017.
  • 6. Jenkins B, McInnis M, Lewis C. Step-Up to USMLE Step 2 CK. Lippincott Williams & Wilkins; 2015.
  • 7. Marino BS, Fine KS. Blueprints Pediatrics. Lippincott Williams & Wilkins; 2013.
  • 8. Russman B. Neonatal Brachial Plexus Palsy. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. http://www.uptodate.com/contents/neonatal-brachial-plexus-palsy. Last updated July 15, 2016. Accessed May 12, 2017.
  • 9. Semel-Concepcion J. Neonatal Brachial Plexus Palsies. In: Moberg-Wolff EA. Neonatal Brachial Plexus Palsies. New York, NY: WebMD. http://emedicine.medscape.com/article/317057. Updated June 17, 2016. Accessed May 12, 2017.
  • 10. Hollingworth T. Differential Diagnosis in Obstetrics and Gynaecology: An A-Z. CRC Press; 2008.
  • 11. Anderson WE. Femoral Mononeuropathy. In: Femoral Mononeuropathy. New York, NY: WebMD. http://emedicine.medscape.com/article/1141793-overview#a8. Updated March 24, 2016. Accessed February 16, 2017.
  • 12. Yeremeyeva E, Kline DG, Kim DH. Iatrogenic sciatic nerve injuries at buttock and thigh levels: the Louisiana State University experience review. Neurosurgery. 2009; 65(4 Suppl): pp. A63–66. doi: 10.1227/01.NEU.0000346265.17661.1E.
  • 13. Stewart JD. Foot drop: where, why and what to do?. Pract Neurol. 2008; 8(3): pp. 158–169. doi: 10.1136/jnnp.2008.149393.
  • 14. Novak CB. Peripheral Nerve Injuries. In: Peripheral Nerve Injuries. New York, NY: WebMD. http://emedicine.medscape.com/article/1270360-workup#showall. Updated July 7, 2016. Accessed February 16, 2017.
  • 15. Akuthota V, Herring SA . Nerve and Vascular Injuries in Sports Medicine. New York, NY: Springer Science & Business Media; 2009.
  • 16. Jacobs MA, Austin N, Austin NM . Splinting the Hand and Upper Extremity: Principles and Process. Baltimore, MD: Lippincott Williams & Wilkins; 2003.
  • 17. Haastert-Talini K, Grothe C. Electrical stimulation for promoting peripheral nerve regeneration. Int Rev Neurobiol. 2013; 109: pp. 111–124. doi: 10.1016/B978-0-12-420045-6.00005-5.
  • 18. Griggs RB, Bardo MT, Taylor BK. Gabapentin alleviates affective pain after traumatic nerve injury. Neuroreport. 2015; 26(9): pp. 522–527. url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4479280/.
  • 19. Fang XY, Zhang WM, Zhang CF et al. Lithium accelerates functional motor recovery by improving remyelination of regenerating axons following ventral root avulsion and reimplantation. Neuroscience. 2016; 329: pp. 213–225. doi: 10.1016/j.neuroscience.2016.05.010.
last updated 08/13/2019
{{uncollapseSections(['HuaKsm', 'DrX1jz', 'urXpQz', 'FrXgQz', '8rXOQz', '42c33b0', 'ErX8Qz'])}}