Neurology: post-foaling paralysis in Horses (Equis) | Vetlexicon
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Neurology: post-foaling paralysis

ISSN 2398-2977

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Introduction

  • An infrequent sequel to foaling of hindlimb weakness through to paralysis.
  • Cause: compression of the nerves within the pelvic canal of the mare during parturition.
  • Signs: mild stiffness to paraplegia.
  • Diagnosis: history of parturition/dystocia and clinical signs.
  • Treatment: anti-inflammatory and supportive therapy.
  • Prognosis: fair - 50% recover in days/weeks.

Presenting signs

  • Range of hindlimb involvement from mild stiffness to paraplegia.

Acute presentation

  • Recumbency and inability to stand after parturition.

Breed/Species predisposition

  • Small cross-bred mares: the use of a large-sized breed sire on a small-sized dam can   →   large-sized foal at birth.

Cost considerations

  • Prolonged supportive care may be required if recumbent for a long period which can be costly.
  • Complications arise from prolonged recumbency and the mare has to be euthanized.

Pathogenesis

Etiology

  • Compression of the mares obturator nerve during parturition.

Specific

Pathophysiology

  • Various nerves within the pelvic canal are vulnerable to compression from bony parts of the foal during parturition:
    • The obturator nerve (   →   adductor muscles of thigh) as it courses along the medial aspect of the shaft of the ilium. 
    • A nervous web which lies against the ventral aspect of the sacrum giving rise to the following nerves:
      • Sciatic (   →   main extensor muscles of hip and flexors of stifle).
      • Cranial gluteal.
      • Caudal gluteal.
  • Rarely the femoral nerves (   →   major extensor muscles of stifle) can be involved by hemorrhage in and around them.
  • Dystocia may or may not have occurred.
  • Unilateral or bilateral limb involvement.
  • Depending on the severity of the nerve/nerve root damage, the full range of hindlimb involvement from mild stiffness to paralysis may be caused.

Timecourse

  • The onset of signs is immediately following or within a few hours after parturition.
  • Duration of signs varies with the degree of nerve damage from days to weeks.
  • The mare may remain recumbent for several weeks.

Diagnosis

Presenting problems

Client history

  • Recent parturition +/- dystocia.

Clinical signs

  • Full range from mild hindlimb stiffness to paraplegia.
    • Mild unilateral obturator nerve contusion: 
      • Abduction and circumduction of ipsilateral limb at the walk.
      • Affected limb slips laterally when attempting to rise or when standing on a slippery surface   Hindlimb: obturator nerve paralysis  .
    • Femoral nerve involvement:
      • Extensor weakness    Femoral nerve: neuropathy    Femoral nerve: neurapraxia  .
      • Patellar hyporeflexia.
      • Medial thigh analgesia.
  • Unilateral or bilateral hindlimb involvement.

Diagnostic investigation

Biochemistry

Confirmation of diagnosis

Discriminatory diagnostic features

  • History and clinical signs.

Definitive diagnostic features

  • Absence of any other causative factors.

Gross autopsy findings

  • Nerve/nerve root contusion to varying degrees.
  • Very rarely nerve(s) are severed.

Differential diagnosis

Treatment

Initial symptomatic treatment

  • Supportive therapy for mare and foal.

Standard treatment

Mare

  • Anti-inflammatories   Therapeutics: anti-inflammatory drugs  , eg corticosteroids, phenylbutazone   Phenylbutazone  .
  • Supportive care:
    • Deep bed to prevent decubital ulcer formation   Elbow: wound - pressure sore  .
    • Remove/protect sharp/hard objects to prevent self-trauma when attempting to rise.
    • Ensure mare can feed/water from low level.
    • Fluid therapy   Fluid therapy: overview  : overview if required from monitoring hydration and electrolyte balance   Fluid therapy: electrolyte abnormalities  .
    • Monitor food/water intake parenteral feeding may be required   Nutrition: parenteral  .
  • Assist standing as soon as mare is able, or use a sling once mare can support weight sufficiently on limbs.
  • Monitor milk production: suppress lactation if mare is recumbent for a prolonged period.

Foal

  • Colostrum will need to be administered to the foal if the mare cannot stand for the foal to suckle within the first few hours after birth   Nutrition: neonate  .
  • Parenteral feeding will be required if the mare cannot stand for the foal to suckle   Nutrition: neonate  .
  • The foal may require fostering.

Monitoring

Mare

  • Blood samples from mare to assess hydration.
  • Fluid therapy as required to prevent dehydration or correct any electrolyte imbalances.

Foal

Subsequent management

Treatment

  • Continue supportive therapy until mare is completely recovered.

Prevention

Group eradication

  • Attend to dystocia or prolonged parturition as quickly as possible.

Do not breed small mares with large stallions.

Outcomes

Prognosis

  • Fair:  full function returns in 50% of cases over a period of days/weeks.
  • In severe cases the mare may not recover and has to be euthanized.

Expected response to treatment

  • Depending on the extent of the injury to the nerves, the mare should recover within days to weeks.
  • In severe cases the mare may remain recumbent for several weeks.

Reasons for treatment failure

  • Prolonged recumbency may lead to other complications which result in the mare having to be euthanased, eg ischemic myoneuropathy.

Further Reading

Publications

Refereed papers

Other sources of information

  • Hahn C H, Mayhew I G & Mackay R J (1999) Nervous System: diseases of the Peripheral (Spinal) Nerves. In: Equine Medicine and Surgery. Eds: Colahan P T, Mayhew I G, Merritt A M & Moore J N. Mosby Inc, USA. pp 978-979. ISBN: 0815117434.