• Clinical science

Peripheral nerve injuries

Summary

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. Patients with peripheral nerve injury may present with sensory deficits, loss of motor function, or a combination of both. Diagnosis is based on clinical evaluation, imaging techniques (x-ray, CT/MRI), and electrodiagnostic examination (e.g., nerve conduction study, EMG). Observation and conservative treatment (e.g., activity modification, splinting, electrical stimulation) are indicated in most closed injuries, which have a high rate of spontaneous recovery. Patients with open injuries or long disease courses may require surgical treatment. Recovery from peripheral nerve injury is often incomplete and patients may experience chronic pain.

Types of nerve damage

Classification of peripheral nerve injury is useful for determining the 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 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 membrane 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
        • The proximal stump either stays in place or retracts slightly; ultimately, the stump will sprout regenerative nervous fibers that, ideally, reinnervate the distal tissues.
        • Regeneration is significantly more efficient in the peripheral nervous system 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
    • The chances of recovery are very poor without surgical repair.
  • Traumatic neuroma: benign, painful nodular thickening caused by nerve regeneration at the site of different forms of nerve injury

References:[1][2]

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 and shoulder dystocia
  • 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 (absent or impaired on the affected side)
    • 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
    • Surgery for severe nerve damage or prolonged cases

Klumpke palsy

Peripheral nerve injuries in the upper extremity

Injured nerve Nerve roots Common causes Motor deficits Sensory deficits
Axillary nerve injury
  • C5–C6
  • Lateral shoulder (lower half of the deltoid region)
Musculocutaneous nerve injury
  • C5–C7
  • Trauma
  • Upper trunk compression (e.g., Erb palsy)
  • Lateral forearm, from the elbow to the base of the thumb
Median nerve injury
  • C5–T1
  • Palmar aspect of thumb, index and middle fingers, lateral ring finger
Radial nerve injury
  • C5–T1
  • Dorsal aspect of thumb, index, and middle fingers, lateral ring finger

Ulnar nerve injury

  • C7–T1
  • Palmar and dorsal aspects of lateral half of ring finger, little finger

Peripheral nerve injuries in the cervicothoracic region

Injured nerve

Innervated muscles

Common causes

Motor 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

Phrenic nerve injury

  • Diaphragm
  • Elevation of the diaphragm on the side of the phrenic nerve lesion → ↓ pulmonary and cardiac function

"C3, 4, 5 keeps the diaphragm alive"

References:[3][4][5][6][7][8][9][10]

Nerve injuries in the lower body

Injured nerve

Nerve roots

Common causes

Motor deficits

Sensory deficits
Superior gluteal nerve injury
  • L4–S1
  • Iatrogenic injury due to intramuscular injections in the superomedial region
  • None
Inferior gluteal nerve injury
  • L5–S2
  • Paralysis of gluteus maximus → impaired thigh extension
  • Difficulty standing from a sitting position and climbing stairs
  • Backward lurching gait (an abnormal gait in which the trunk tilts backwards during the heel strike phase in the limb with the weak hip extensor)
  • Forward pelvic tilt
  • None

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
  • Anterior cutaneous branches: anteromedial thigh
  • Saphenous nerve lesion : medial lower leg, medial edge of the foot
Lateral femoral cutaneous nerve injury (meralgia paresthetica)
  • L2–L3
  • 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)
  • None
  • 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
  • Paralysis of hip adductors
  • Medial thigh
Sciatic nerve injury
  • L4–S3
  • Lower leg and foot
Tibial nerve injury
  • 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
  • None
  • Posterolateral side of 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

References:[11][12][13]

Diagnostics

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-ray: detection of compression or transection due to dislocated bone or fracture segments
    • CT/MRI: evaluation of causes like nerve tumors, avulsions, and focal soft tissue pathologies
  • Electrodiagnostic studies

References:[14]

Nerve repair

Conservative treatment

  • Observation and expectant management in closed injuries of the nerve, which have 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); used 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.

References:[15][16][17][18][19]

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last updated 12/12/2019
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