Equis ISSN 2398-2977

Foal: neonatal maladjustment syndrome

Synonym(s): dummy barker wanderer hypoxic-ischemic encephalomyelopathy HIE

Contributor(s): Robert J MacKay, Carla Sommardahl

Introduction

  • Cause: uncertain, probably related to CNS hypoxial ischemia at birth, secondary to placental dysfunction, external pressure in the birth canal, cardiovascular and/or respiratory dysfunction, metabolic disturbances; possibly systemic illness in utero → inability to adjust to extra-uterine life.
  • Signs: neurologic signs - poor or absent suckling reflex, convulsions, disorientation, inco-ordination, weakness or inability to stand.
  • Diagnosis: history and signs.
  • Treatment: anticonvulsant therapy; cerebral decompression; thermoregulation; oxygen; nursing; ACTH for premature or dysmature foals.
  • Prognosis: guarded.

Pathogenesis

Etiology

  • Postulated causes include:
  • Definitions:
    • Prematurity: <320 days gestation, hypoflexion of limbs ('floppy') and inability to stand and suck within 2 h of birth, <45 kg birthweight (Thoroughbred).
    • Dysmaturity: delivered at term but with signs of prematurity; associated with placental pathology and precocious mammary development in the mare.

Pathophysiology

  • Cerebral dysfunction → convulsions and/or failure to suck → weight loss, dehydration → rapid decline.
  • Dysmaturity:
    • Placental pathology → fetal stress → precocious adrenocortical maturation → range of subtle effects on endocrine maturation and function.
  • Placenta:
    • Diffuse epithelio chorial placenta → extensive circulation of 300-400 cm between cardiac output and return → vulnerability to ischemia.
    • Placental size correlates with fetal size at term.
  • Factors affecting placental growth and size:
    • Nutrition.
    • Environmental temperature.
    • Loss of attachment.
    • Uterine and umbilical blood flow.
    • Maternal size.
  • Placental growth rate is determined early in pregnancy.
  • Some compensatory growth following a period of retardation can occur but is severely limited as gestation progresses.
  • Growth restricted placenta → growth-restricted fetus → hypoxemia and hypoglycemia plus other endocrine alterations (insulin, thyroid homrones, catechomaines and cortisol) → physiological alterations persist in neonate and older animal.
  • Intra-uterine growth retardation → respiratory dysfunction and potentially decreased muscle mass at maturity.
  • Pulmonary function:
    • ?Inadequate duct density at termination of airways.
    • Prolonged recumbancy (post-partum) → atelectasis → loss of pulmonary dead space → right to left shunt develops → respiratory distress and hypoxemia.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • McSloy A (2008) Hypoxic ischaemic encephalopathy: Recognising and treating the dummy foal. UK Vet 13 (9), 4-8 VetMedResource.
  • No authors listed (1998) Third Dorothy Russell Havemeyer Foundation Third International Workshop on Equine Perinatology: comparative aspects. Proceedings. Equine Vet J 30 (6), 455-466 PubMed.
  • Rossdale P (1993) Clinical view of disturbances in the equine fetal maturation. Equine Vet J 14, 3-7 PubMed.
  • Drummond W H (1988) Neonatal maladjustment syndrome, its relationship to perinatal hypoxic-ischemic insults. Equine Vet J Suppl 5, 41-43 Wiley Online Library.

Other sources of information

  • Bernard W V (2003) Jump-Starting the Dummy Foal (Neonatal Maladjustment Syndrome/Hypoxic Ischemic Encephalopathy). In: Proc 49th AAEP Convention. pp 8-12.
  • Bain F T (1999) How I Treat Neonatal Maladjustment Syndrome. In: Proc NAVC. pp 73.


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