This syndrome is known by a variety of names (Hypoxic ischaemic encephalopathy, Perinatal asyphyxia syndrome, Neonatal encephalopathy, Wanderer, Barker or Dummy foals).
Foals can suffer from reduced blood flow and decreased oxygen delivery to vital organs (brain, kidneys, intestinal tract) due to early placental separation (Red bag delivery), dysfunction of the placenta (placentitis), a difficult or prolonged delivery or emergency Caesarean section. Some of these foals show abnormal behaviour from birth. Others are relatively normal for the first few hours, but may then start to show signs at 24-36 hours old.
We also see ‘dummy foals’ which have had an apparently normal, or even quick, foaling. During pregnancy, progestogens present in the foal’s blood have a mild ‘sedative’ effect. In normal foals, blood progestogen levels drop rapidly at birth, and suggest that the trigger for this is the ‘squeezing’ effect on the foal’s ribcage during delivery. Foals born very rapidly, which then show neurological signs, have been shown to have abnormally high blood progestogen concentrations. ‘Squeezing’ the foal for 20 minutes with soft ropes placed around the ribcage (after checking that there are no fractured ribs) is thought to mimic the birth process of foaling and has been shown to result in an improvement in the behavioural signs in some foals.
The condition has many manifestations, including difficulty in getting up, a poor suck reflex, inability to find the teat, abnormal swallowing reflex, head tilt, walking in circles, seizures, reduced gut motility (which may lead to meconium impaction and in severe cases, reflux of ingested colostrum or milk) abnormal bladder function and kidney failure. These foals are also more susceptible to acquiring infections.
Treatment is supportive; it may be just assisting the foal to stand and find the teat and supervising it to suck every 1-2 hours. Other foals suffering from frequent seizures may require hospitalisation, heavy sedation, nasal oxygen, intravenous fluids, intravenous nutrition and plasma transfusions, which can become very expensive. The neurological signs usually improve rapidly over the first week. Full term, normal birthweight foals with NMS, which do not develop complications have a good prognosis (80% survival rate).