Peripheral nerve injuries

Last updated: May 9, 2022

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Peripheral nerve injuries result from systemic diseases (e.g., diabetes, autoimmune disease) or localized damage (e.g., trauma, compression, tumors) and manifest with neurological deficits distal to the level of the lesion. They occur as isolated neurological conditions or, more commonly, in association with soft tissue, vascular, and/or skeletal damage. Peripheral nerve injury can cause 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.

Nerve fiber overview
Nerve fibers Myelination Impulse conduction velocity (m/s) Afferent fibers Efferent fibers
A (Ia, Ib)
  • Present
  • 100
(II)
  • 50
  • None
  • 20
  • None
(III)
  • 15
B
  • 7
  • None
C (IV)
  • Absent
  • 1

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 [1]

Leads to central chromatolysis

  • Definition: the reaction of a neuronal cell body in response to an axonal injury
  • Function: increase in protein synthesis to help restore the integrity of the damaged axon
  • Characteristics
    • Swelling of the neuronal body
    • Dispersion of the Nissl bodies
    • Displacement of the nucleus to the periphery

Results in Wallerian degeneration

  • Definition: an active neuronal degeneration process in response to axonal injury
  • Function
    • To clear axonal debris and prevent scarring
    • Facilitate targeted reinnervation and functional recovery of tissues previously innervated by that axon before injury
  • Characteristics

Neurotmesis [1]

  • 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

Brachial plexus injuries [2][3]

Erb palsy

For weakened muscles in Erb's palsy, imagine BIRDS eating hERBS served by a waiter: Biceps brachii, Infraspinatus, wRist extensors, Deltoid, Supraspinatus, waiter's tip posture.

Klumpke palsy

Peripheral nerve injuries in the upper extremity

  • Distal nerve lesions are more likely to cause claw deformities (e.g., ulnar claw or median claw) because they result in a loss of lumbrical function with intact extrinsic flexors
  • In proximal nerve lesions, hand distortions (e.g., pope's blessing) are only visible when the patient tries to flex the fingers or make a fist.
Overview of peripheral nerve injuries in the upper extremity
Injured nerve Nerve roots Common causes Motor deficits Sensory deficits
Axillary nerve injury
  • C5–C6
  • Lower part of the deltoid region and lateral arm
Musculocutaneous nerve injury
  • C5–C7
  • Trauma
  • Upper trunk compression (e.g., Erb palsy)
Radial nerve injury
  • C5–T1
  • Axillary injury: impaired forearm extension at elbow, wrist drop
  • Mid-arm injury: wrist drop
  • ↓ Grip strength: Maximal flexion can only be achieved when the wrist is extended.
  • Dorsal arm and forearm
  • Hand
    • Dorsal aspect of the thumb, index, and the middle fingers
    • Lateral ring finger
Median nerve injury
  • C5–T1

Recurrent branch of median nerve injury

  • C5–T1
  • No sensory deficits

Ulnar nerve injury

  • C8–T1

Peripheral nerve injuries in the cervicothoracic region

Overview of peripheral nerve injuries in the cervicothoracic region

Injured nerve

Nerve roots

Innervated muscles

Common causes

Motor deficits

Phrenic nerve injury

  • C3–C5
  • Diaphragm
  • Elevation of the diaphragm on the side of the phrenic nerve lesion ↓ pulmonary and cardiac function

Suprascapular nerve injury

  • C4–C6

Dorsal scapular nerve injury

  • C5
  • Isolated injury is uncommon
  • Usually accompanies injury to the scalene muscles

Long thoracic nerve injury

  • C5–C7

Thoracodorsal nerve injury

  • C6–C8

Diaphragm innervation: "C3, 4, 5 keep the diaphragm alive."

Overview of nerve injuries in the lower body

Injured nerve

Nerve roots

Common causes

Motor deficits

Sensory deficits

Iliohypogastric nerve injury

  • T12–L1
  • Lateral hip
  • Suprapubic region
  • In iatrogenic injury: burning or tingling sensation radiating to regions innervated by the injured nerve
Genitofemoral nerve injury
  • L1–L2
Lateral femoral cutaneous nerve injury (meralgia paresthetica)
  • L2–L3
  • None
Femoral nerve injury
  • L2–L4
Obturator nerve injury
  • Howship-Romberg sign: pain and paresthesia over the inner aspect of the thigh
Superior gluteal nerve injury
  • None

Common peroneal nerve injury

Sciatic nerve injury
  • Lower leg and foot
Tibial nerve injury
  • Sensory loss over sole of the foot (See “Morton neuroma” for more information.)
Sural nerve injury
  • None
  • Posterolateral side of the lower leg
  • Lateral border of the foot
  • Small area under the heel
Inferior gluteal nerve injury
  • Paralysis of gluteus maximus → impaired thigh extension
  • Difficulty standing up from a sitting position and climbing stairs
  • Backward lurching gait: an abnormal gait in which the trunk tilts backward while walking during the heel strike phase of the limb with the weak hip extensor
  • Forward pelvic tilt
  • None

Differences between tibial nerve and peroneal nerve injuries: TIPPED
Tibial → impaired foot Inversion and Plantarflexion
Peroneal → impaired foot Eversion and 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).

Conservative treatment [6]

Surgical repair

  • Indications
    • Open, non-contaminated, sharp injuries and concomitant vascular injuries → immediate surgical exploration and repair
    • Open, contaminated injuries and 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
    • Nerve transfer: an intact healthy nerve is redirected towards a denervated nerve in order to restore the innervation of its target organ
    • Tendon transfer: a tendon from a sufficiently powerful muscle is redirected towards another tendon in order to restore its motion and function
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  4. 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): p.A63-66. doi: 10.1227/01.NEU.0000346265.17661.1E . | Open in Read by QxMD
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  7. Jacobs MA, Austin N, Austin NM . Splinting the Hand and Upper Extremity: Principles and Process. Lippincott Williams & Wilkins ; 2003
  8. Haastert-Talini K, Grothe C. Electrical stimulation for promoting peripheral nerve regeneration. Int Rev Neurobiol. 2013; 109 : p.111-124. doi: 10.1016/B978-0-12-420045-6.00005-5 . | Open in Read by QxMD
  9. Griggs RB, Bardo MT, Taylor BK. Gabapentin alleviates affective pain after traumatic nerve injury. Neuroreport. 2015; 26 (9): p.522-527.
  10. 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 : p.213-225. doi: 10.1016/j.neuroscience.2016.05.010 . | Open in Read by QxMD

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