Sciatic nerve: paralysis in Horses (Equis) | Vetlexicon
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Sciatic nerve: paralysis

ISSN 2398-2977


Introduction

  • Peripheral nerve injuries are relatively common; some regeneration of peripheral nerves occurs but is slow.
  • See also peripheral nerve injuries overview   Peripheral nerve: trauma  .
  • Cause: direct trauma, inflammatory disease of the spinal cord, bacterial infection, osteomyelitis fractures or from misdirected injections in foals.
  • Signs: extension of stifle and hock and loss of sensation in distal limb, dragging of the foot.
  • Diagnosis: clinical signs and examination of muscles.
  • Treatment: steroids and non-steroidal anti-inflammatories may be useful.
  • Prognosis: depends upon extent of damage to nerve.

Presenting signs

  • Extension of stifle and hock and flexion of fetlock.
  • Inability to flex and advance hindlimb.
  • Foot drags on floor.

Pathogenesis

Etiology

  • Direct trauma.
  • Associated with coxo-femoral luxation or acetabular fractures.
  • Associated with pelvic fractures or sacral/pelvic osteomyelitis.
  • Inflammation of the spinal cord, eg equine protozoal myelitis.
  • In adults the nerve is very deep, but in foals it is more superficial and so can be damaged by intramuscular injection.

Pathophysiology

  • The sicatic nerve originates from segments L6-S1.
  • It innervates the semimembranosis and semitendinosis muscles before splitting into tibial and peroneal branches.
  • Sciatic nerve damage   →   loss of tibial and peroneal nerve function   →   loss of sensation in distal limb (below stifle).
  • The tibial branch is more commonly affected.
  • Motor loss   →   poor limb flexion.
  • Damage may be mild and temporary (neuropraxia).
  • Severe/permanent loss of function may occur (neurotmesis).

Diagnosis

Presenting problems

  • Abnormal hindlimb gait, dragging foot, stifle and hock held in extension.

Client history

  • May be history of trauma.
  • Injections into buttocks of foals.
  • Inability to flex and advance hindlimb.

Clinical signs

  • Extension of stifle and hock.
  • Flexion of fetlock.
  • Weight can be borne if limb placed in natural position, but any movement will lead to weight being supported on dorsum of foot.
  • Inability to flex and advance the hindlimb.
  • Loss of sensation in distal limb.

Diagnostic investigation

Other

Confirmation of diagnosis

Discriminatory diagnostic features

  • History and clinical signs.

Definitive diagnostic features

  • Clinical signs and accurate neurologic examination.
  • Electromyography if available.

Differential diagnosis

Treatment

Initial symptomatic treatment

  • Rest.

Standard treatment

  • Rest.

Prevention

Outcomes

Prognosis

  • Dependent upon extent of damage.
  • Some regeneration of peripheral nerves occurs but very slow (usually regrowth is no more than 0.5 cm/year).
  • Most cases due to anesthesia resolve after 2-7 days, but some wasting/changes in gait may persist.
  • Prognosis poorer if no change after 4 weeks.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • von Schweinitz D G (2014) Electroacupuncture for nerve injury in the horse. Equine Vet Educe 26, 24-26 VetMedResource.
  • Hahn C (2008) Common peripheral nerve disorders in the horse. In Pract 30 (6), 322-329 VetMedResource.