Peroneal nerve: trauma in Horses (Equis) | Vetlexicon
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Peroneal nerve: trauma

ISSN 2398-2977

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Introduction

  • Common injury.
  • Cause: kick or pressure to the lateral stifle, a tibial fracture and anesthesia.
  • Signs: inability to flex hock and extend digits, shorter stride, knuckling of fetlock, hypalgesia of craniolateral portion of limb.
  • Diagnosis: pelvic limb lameness.
  • Treatment: DMSO, corticosteroids, surgery.

Presenting signs

  • Extension of the tarsus.
  • Flexion of the fetlock.
  • Flexion of the interphalangeal joints.
  • At rest, the leg will be extended caudal with the dorsum of the hoof resting on the ground.
  • At a walk, the foot is dragged along the ground and then jerked caudal when weightbearing is attempted.
  • Atrophy of the cranial lateral muscles of the gaskin.

Geographic incidence

  • Worldwide.

Pathogenesis

Etiology

  • From blunt trauma to the lateral condyle of the femur.
  • From fractures of the lateral condyle of the femur.
  • By a kick or pressure to the lateral stifle.
  • A tibial fracture.
  • Anesthesia.

Pathophysiology

  • The peroneal nerve is a distal branch of the sciatic nerve.
  • Injury to peroneal nerve leads to alterations in flexor muscles of the tarsus.
  • Injury to peroneal nerve leads to alterations in extensor muscles of the digits.
  • Peroneal nerve sectioning in ponies results in the above gait deficits initially.
  • Paralysis of the peroneal branch results in extension of the tarsus and flexion of the fetlock and interphalangeal joints.
  • Atrophy of the cranial lateral muscles of the gaskin may be expected.
  • Injury to this nerve is a component of sciatic injury.

Timecourse

  • Injury from kicks by other horses or from lateral recumbency will lead to transient signs that will eventually improve.
  • Ponies with peroneal nerve sectioning show within 3 month minimal gait deficits.

Diagnosis

Presenting problems

  • Pelvic limb lameness.

Client history

Clinical signs

  • Inability to flex hock and extend digits.
  • Shorter stride.
  • Knuckling of fetlock.
  • Weightbearing can be performed if the leg is advanced manually and the toe extended.
  • Hypalgesia of craniolateral portion of limb.
  • Hypalgesia on the craniolateral aspect of the gaskin, hock, and metatarsal regions.
  • Measurement of the affected limb circumference using a measurement tape can be helpful in picking up subtle decreases in limb diameter associated with muscle atrophy.

Diagnostic investigation

Other
  • Neurologic exam  Neurology: examination - adult    Neurology: examination - foal  .
  • Electrodiagnostic aids(EMG and nerve conduction velocity) may be helpful in diagnosing diseases of the nerves   →   because the muscle is the end organ of the peripheral nerve, damage to the nerve can lead to abnormal muscle electrical potentials such as positive sharp waves and fibrillation potentials.
  • Muscle biopsymay reveal muscle fiber atrophy, angular fibers, and fiber type grouping characteristics of denervation.

Confirmation of diagnosis

Discriminatory diagnostic features

  • History and clinical signs.

Definitive diagnostic features

Treatment

Standard treatment

Medical management
  • Dimethyl sulfoxide (DMSO)  Dimethyl sulfoxide  :
    • Can be used in horses with acute injury to peripheral nerves.
    • Its principal action is to scavenge free oxygen radicals generated in damaged tissue.
    • Helps to maintain blood flow to hypoxic tissues by reducing generation of prostaglandins and thromboxane, thus preventing platelet aggregation.
    • Can be efficacious early in the onset of peripheral nerve trauma both intravenously (IV) (1 g/kg as a 10% solution) and topically over the affected area
  • Corticosteroids:
    • Can be efficacious in acute peripheral nerve trauma.
    • Dexamethasone   Dexamethasone  (0.05-0.2 mg/kg IV) may be used initially.
    • Short-term administration of corticosteroids is best, but long-term administration may be necessary.

    When given at the recommended doses, corticosteroids can act synergistically with DMSO
    Surgical management
  • May not be necessary in uncomplicated nerve injury if the horse is not used for performance.
  • If the nerve is severed, then it should be anastomosed at the time of injury.

Subsequent management

Treatment

Surgical management
  • Surgical exploration of the area to free entrapped nerves or hematomas should only be performed if the condition persists.
  • Removal of adhesions, neuromata, and possible re-anastomosis can be performed 2-8 weeks after injury.
    Physical therapy
  • May be effective in developing compensatory mechanisms and strength in horses that have recovered from the initial nerve injury.
  • Horses may improve dramatically with regular and controlled exercise on a lunge line, treadmill, or at pasture.
  • Exercise allows the unaffected parts of the nervous system to compensate for the affected muscles by increasing strength and conscious proprioception.
  • Massage, therapeutic ultrasound   Musculoskeletal: therapeutic ultrasound  , ice packs, and hydrotherapy of affected muscle groups for 10-15 min, two to three times daily should be carried out.
  • Passive flexion and extension of the affected limb are also helpful in maintaining range of motion.
  • Spl inting of affected limbs may keep the limb from dragging on the ground, thus preventing ulcer formation.

Prevention

Outcomes

Prognosis

  • Usually, decompression of entrapped nerves may lead to full recovery and return to function in 2-3 months.

Further Reading

Publications

Refereed papers