Originally published on TheHorse.com
Nothing disrupts the joy of foal ownership like the observation of potential problems: A disinterest in nursing, a depressed attitude, strange mannerisms, or seizures could mean a foal is suffering from some serious neurologic problems. During a presentation at the 2011 Western Veterinary Conference, held Feb. 20-24 in Las Vegas, Nev., Mary Rose Paradis, DVM, MS, Dipl. ACVIM, an associate professor in the Department of Clinical Sciences at Tufts University's Cummings School of Veterinary Medicine, in North Grafton, Mass., discussed some of the common problems that neurologic foals exhibit along with diagnostic methods and treatments.
Besides the common signs of depression and seizures, the resting foal might thrash his legs at seemingly random times, or he might make paddling motions with his legs as he walks; the foal might display back muscle spasms (known as opisthotonos, seen in the foal as hypertension/arching of the back to one side) or show extensor muscle rigidity; or he might overheat (hyperthermia), she added.
Neurologic Exams in Foals
"The most common neurologic presenting complaints in the newborn foal are changes in normal behavior, lack of suckle, depression, and seizures," Paradis explained.
A neurologic examinations of a foal differ from those performed on adult horses, Paradis said, and it might yield slightly different results:
Whereas gait analysis is generally performed in hand, on a longe line, or under saddle in the adult horse, Paradis suggested watching a foal's gaits while he is "freely moving about the stall or paddock."
A depressed foal lacks a response to external stimuli and spends an unusually large amount of time sleeping, Paradis said. It's important to understand that healthy foals can spend about half their day napping, so consider how he responds to typical external stimuli before assuming a sleepy foal is depressed.
"Seizures in the first few days of life of the foal can be acquired or congenital (born with it) in origin," Paradis said, adding that acquired seizures are generally related to perinatal asphyxia (lack of oxygen in a neonate during the birth process), infection, or trauma; congenital causes include abnormally formed neurologic or skeletal tissue or a genetic defect.
Neonatal Encephalopathy (NE)
Paradis said NE (also called neonatal maladjustment syndrome or dummy foal syndrome) is the most common acquired--as opposed to congenital--neurologic problem seen in foals. She noted that while researchers are not certain about what causes NE, they believe that some type of asphyxiation plays a role in the disorder's development--simply put, the foal's brain is deprived of enough oxygen during birth, whether through chronic placental insufficiency or acute placental separation, leading to abnormalities. Paradis said most foals (70%-80%) with NE recover and lead a healthy life.
Another less-frequent cause of seizures in the foal is bacterial meningitis, which Paradis explained is a form of septicemia. In the neonate's central nervous system, the blood-brain barrier--that which generally protects the brain from harmful cells circulating in the blood--is incomplete. This situation is compounded by the foal's relative lack of phagocytes, which are white blood cells that engulf and digest bacterial invaders.
"Once bacterial entry has occurred," Paradis noted, "cerebrospinal fluid (CSF) acts as a good media for bacterial growth. Rapid multiplication of the bacteria is favored because of the inadequate ... defenses of the CNS."
Paradis said that many foals with neurologic problems have a history of trauma, specifically of the head and neck.
"Cerebral trauma (cases) will have signs of blindness, depression, seizure, head pressing, and coma," Paradis described.
She continued to explain that brain stem trauma will be accompanied by signs of nystagmus (involuntary movement of the eyeballs), facial paralysis, strabismus (misalignment of the eyeballs within the sockets), and gait abnormalities. Clinical signs of neck trauma or intracranial hemorrhage include ataxia (incoordination), and paralysis.
Congenital Neurologic Issues
Several congenital neurologic problems affect foals, Paradis said:
Paradis described several diagnostic options for veterinarians addressing neurologic problems in foals:
"The most important ... therapy for the neurologic foal is supportive care," Paradis stressed. She explained that a stomach tube will be the easiest way to ensure the foal receives proper nutrition during treatment, and that recumbent foals should be monitored closely for pressure sores. The foal will also need to be kept warm and dry, a task that can prove difficult as the foal may urinate on itself when unconscious, causing urine scalding.
Medical treatment for seizures (generally controlled by sedatives diazepam or midazolam) and antibiotics for controlling meningitis is warranted. Paradis emphasized, though, that the foal should have attentive nursing care to prevent additional problems/injuries.
Because foals tend to "grow out" of some neurologic problems, depending on the disorder, the prognosis can be a positive one. Paradis relayed that foals with NE specifically have a good prognosis, with survival rates as high as 80%. Many of these foals, she added, have grown up to have successful careers under saddle.
Foals with septic meningitis, however, have a less favorable chance for survival. She explained that if the foal does survive his illness, "there is a chance it will have a mental disability that may make it untrainable." She added that a new group of drugs (called third-generation cephalosporins) have shown promise for treating meningitis, however, and if they continue to yield positive results, "this picture may change."
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.