Neu­ro­logic Dis­or­ders: The Warn­ing Signs

Know­ing the the signs of a pos­si­ble ner­vous-sys­tem is­sue can mean the dif­fer­ence be­tween re­cov­ery and lin­ger­ing dis­abil­ity (or worse) for your horse.

Practical Horseman - - News - By Sushil Du­lai Wen­holz

Learn to rec­og­nize the red flags of a ner­vous-sys­tem is­sue early as well as what you can do to get your horse on the road to re­cov­ery.

Your horse just isn’t quite right. His per­for­mance has been a lit­tle off lately, you’ve no­ticed him stum­bling now and then, and he seems to be los­ing mus­cle over his topline. He’s not ac­tu­ally lame. So what’s go­ing on?

With symp­toms like those, there’s

a good chance your horse might be fac­ing a neu­ro­log­i­cal dis­or­der. Many things—in­clud­ing trauma, de­gen­er­a­tive con­di­tions, viruses and par­a­sites—can dis­rupt the sig­nals flow­ing along your horse’s spinal cord from the brain to the nerves and mus­cles.

“De­tect­ing symp­toms early in­creases the like­li­hood of suc­cess­ful treat­ment and re­cov­ery,” says the Univer­sity of Penn­syl­va­nia New Bolton Cen­ter’s as­sis­tant pro­fes­sor Amy L. John­son, DVM, DACVIM in both in­ter­nal medicine and neu­rol­ogy. That’s be­cause neu­ro­log­i­cal dis­or­ders af­fect neu­rons (nerve cells), and “once neu­rons are de­stroyed, they don’t re­gen­er­ate,” says Dr. John­son.

If a neu­ro­logic dis­or­der is left un­treated, she adds, more neu­rons be­come af­fected and more of them die.

“Horses can com­pen­sate for los­ing some neu­rons, but once a crit­i­cal number are lost, nor­mal func­tion will never re­turn. And al­most all neu­ro­log­i­cal dis­eases can be fa­tal, depend­ing on the sever­ity and whether or not treat­ment is pro­vided.”

That’s why it’s crit­i­cal for horse own­ers to know the signs of po­ten­tial neu­ro­logic trou­ble and act quickly to bring a vet onto the scene. Here, Dr. John­son shares red flags to watch for, plus an in­side per­spec­tive on what your vet will do to pin­point the trou­ble and put your horse on the road to re­cov­ery.

Signs to Watch For

“The most com­mon in­di­ca­tion of a neu­ro­logic prob­lem in horses is some de­gree of clum­si­ness or in­co­or­di­na­tion,” says Dr. John­son. That’s be­cause neu­ro­logic dis­or­ders of­ten af­fect the spinal cord, which de­liv­ers mes­sages to all of the horse’s limbs. So you might no­tice your horse stand­ing in un­usual po­si­tions—say, with his legs crossed or placed more widely than usual. Or your horse might trip, stum­ble, move more slowly than nor­mal or have trou­ble per­form­ing his reg­u­lar work.

Other neu­ro­log­i­cal dis­or­ders af­fect the brain. If the front brain is in­volved, you may spot al­ter­ations in your horse’s be­hav­ior and men­tal sta­tus, says Dr. John­son. For in­stance, she adds, “If your 3-year-old Thor­ough­bred is act­ing like a 20-year-old pony, that could be an in­di­ca­tion of trou­ble.” Other signs of a front-brain prob­lem in­clude ob­ses­sive cir­cling, aim­less wan­der­ing and stag­ger­ing.

“If the prob­lem is in the back part of the brain, or the brain stem, the horse may have an un­usual ap­pear­ance to his face, sim­i­lar to a person who has suf­fered a stroke,” says Dr. John­son. “You may see droop­ing of an ear or eye­lid, the nose pulled to one side, a tilt to the head. The horse may have trou­ble eat­ing or drink­ing, even to the point where food is com­ing out the nose.”

Other gen­eral signs of po­ten­tial neu­ro­log­i­cal trou­ble in­clude mus­cle loss, of­ten on one or both hips, or over the topline. Your horse may not swish his tail or twitch his skin like he nor­mally does—for ex­am­ple, to keep flies off. You may see an over­all drop in con­di­tion or your horse may sud­denly have trou­ble main­tain­ing weight or may lose his ap­petite. Cer­tain dis­or­ders could con­trib­ute to neck pain, lead­ing your horse to re­sist bend­ing his neck or rais­ing/low­er­ing his head, or caus­ing a loss of sup­ple­ness.

If you no­tice any of these signs, it’s time to call the vet.

What to Ex­pect from Your Vet

When your vet ar­rives on site, ex­pect her to start with a ba­sic phys­i­cal exam, tak­ing your horse’s heart rate, res­pi­ra­tory rate and tem­per­a­ture and check­ing for gut sounds. At this stage, the vet is look­ing to elim­i­nate the pos­si­bil­ity of a sys­temic (body-wide) dis­ease, such as sep­ticemia (bac­te­ria or tox­ins in the blood­stream) or equine in­fec­tious ane­mia. says Dr. John­son, be­cause “most neu­ro­log­i­cal dis­or­ders don’t cause sys­temic prob­lems, but sys­temic dis­ease can oc­ca­sion­ally make a horse look neu­ro­logic.”

Your vet will also ask you to dis­cuss the symp­toms you’ve seen, in­clud­ing changes in your horse’s per­son­al­ity, such as lethargy or ag­gres­sion. Share as much de­tail as you can on the cir­cum­stances, such as when the signs started and how of­ten they oc­cur. Your horse’s age and breed may also play a role, since some

neu­ro­log­i­cal prob­lems tend to be more com­mon in cer­tain groups.

Your vet will also take in the big pic­ture, look­ing your horse over for any signs of asym­me­try in pos­ture or muscling, mus­cle atro­phy or lack of con­di­tion.

Your vet will then be­gin con­duct­ing spe­cific tests to pin­point whether your horse’s prob­lems are re­lated to a neu­ro­log­i­cal dis­or­der and, if so, which part of the ner­vous sys­tem is most likely the source of trou­ble. These tests typ­i­cally in­clude pro­ce­dures to check fa­cial re­flexes, body re­flexes and your horse’s gaits and pos­ture.

Fa­cial Re­flexes

“There are 12 cra­nial nerves that in­flu­ence the horse’s abil­ity to see, chew, swal­low and have sym­met­ri­cal ex­pres­sions, among other things,” says Dr. John­son. To test how well these nerves are do­ing their job, she notes, your vet may con­duct any of a number of tests on both sides of the horse (where ap­pli­ca­ble). Here are a few ex­am­ples:

Test­ing your horse’s “men­ace re­sponse.” The vet moves her hand quickly to­ward the horse’s eye to see whether he blinks. This tests the horse’s abil­ity to see and to close his eye­lids.

Check­ing for skin sen­sa­tion. The vet taps along the side of the horse’s face, from the ear to the nos­tril. The horse should blink and/or at­tempt to move away from the tap­ping.

Test­ing the abil­ity to chew and swal­low. The vet may give the horse a treat or watch the horse eat and drink.

Test­ing tongue strength and func-

tion. The vet gen­tly pulls the horse’s tongue out through the bars on one side of the mouth and then watches to see if the horse can pull it back in.

Body Re­flexes

Again, the vet may per­form any or all of the fol­low­ing tests on both sides of your horse to check for nor­mal re­sponses. Typ­i­cally, a lack of re­ac­tion to any test or in a spe­cific area in­di­cates that nerve sig­nals may not be reach­ing that location.

Neck range of mo­tion. The vet may en­cour­age your horse to bend his neck to each side, stretch­ing to­ward the hip, sti­fle or hock, or down be­tween the front legs, of­ten us­ing a car­rot or other treat as an in- cen­tive. If your horse has trou­ble with this ex­er­cise, it could in­di­cate an in­jury to his neck, such as a frac­tured ver­te­bra or neck arthri­tis. Other in­di­ca­tions of neck trou­ble in­clude dif­fi­culty rais­ing the head, hold­ing the head or neck in an un­usual po­si­tion,

loss of sup­ple­ness through the neck and re­luc­tance to bend dur­ing work.

Skin sen­sa­tion. Your vet will lightly run or tap a pen along your horse’s skin to watch for a twitch­ing re­sponse—the re­ac­tion your horse would have to a fly land­ing on his skin.

Re­ac­tion to pres­sure. Your vet will pal­pate your horse’s topline, neck, chest, hindquar­ters and sti­fles to see if he moves away from the pres­sure or oth­er­wise re­acts.

Tail tone and body strength/co­or­di­na­tion. A horse’s tail re­ceives nerve sig­nals from the spinal cord, so your vet will also con­duct tests to make sure those mes­sages are get­ting de­liv­ered. For in­stance, she may lift the tail to check for re­sis­tance; if the tail is limp, that’s a sign of trou­ble. To test your horse’s body strength and co­or­di­na­tion, she may also pull the tail gen­tly to each side while your horse is stand­ing and/or walk­ing. If the pull shifts your horse off bal­ance, that’s an­other red flag.

Gait and Pos­ture As­sess­ment

In the next stage of a neu­ro­log­i­cal eval­u­a­tion, your vet will as­sess your horse’s gaits and pos­ture. In gen­eral, these tests will show whether the horse knows where his feet are and has nor­mal con­trol over his limbs.

Your vet may ask you to walk your horse on vary­ing sur­faces, up or down a slope and a curb or step, in a tight cir­cle in each di­rec­tion and to back up. She may want to see your horse mov­ing freely in a round pen as well as mov­ing in hand. She’ll watch to see if your horse stum­bles, sways, stag­gers, drags his toes, swings a hind leg, steps on him­self or shows other signs of in­co­or­di­na­tion or gait ab­nor­mal­i­ties.

Your vet may also pick up one of your

horse’s feet and place it so it crosses in front of its op­po­site. For ex­am­ple, she may lift the left front and place it over the right front. A horse with a neu­ro­log­i­cal prob­lem may leave the foot out of place for a while be­fore mov­ing it back into po­si­tion.

Go­ing to the Next Level

By this point in the exam, your vet will prob­a­bly have a strong sense of whether your horse has a neu­ro­log­i­cal prob­lem, says Dr. John­son. If the is­sue doesn’t seem neu­ro­logic, she adds, the vet will carry on look­ing for other pos­si­ble causes for what you’re see­ing, such as con­duct­ing a lame­ness exam or oral exam be­cause prob­lems with chew­ing and swal­low­ing, for in­stance, can be caused by den­tal trou­bles.

If your vet de­cides there is a neu­ro­logic dis­or­der, the next chal­lenge is de­ter­min­ing the un­der­ly­ing cause. It’s not as sim­ple as you might think. “The ac­tual neu­ro­logic signs the horse shows de­pend al­most en- tirely on what part of the ner­vous sys­tem is af­fected, rather than the dis­ease it­self,” says Dr. John­son. “In other words, the neu­ro­logic signs of brain in­jury can be sim­i­lar re­gard­less of whether the brain is in­jured due to trauma, ab­nor­mal liver func­tion or in­fec­tion such as equine pro­to­zoal myeloen­cephali­tis. How­ever, other signs might help iden­tify the un­der­ly­ing cause.”

Fol­low­ing are sev­eral ex­am­ples of com­mon neu­ro­log­i­cal dis­or­ders and the symp­toms and di­ag­nos­tic aids that can help your vet dis­tin­guish one from an­other.


If your horse has ex­pe­ri­enced an in­jury to the skull or any part of the spine—for in­stance, from hit­ting his head or fall­ing— that’s a strong in­di­ca­tion that trauma could be the trou­ble. Symp­toms of a prob­lem could be im­me­di­ate, such as un­con­scious­ness, dis­ori­en­ta­tion or tem­po­rary blind­ness. Or they may not ap­pear for a while and then could in­clude trou­ble get­ting up

or lack of co­or­di­na­tion.

Di­ag­nos­tics: Ra­dio­graphs (X-rays) to check for pos­si­ble frac­tures of the skull or spinal ver­te­brae.

Equine Pro­to­zoal Myeloen­cephali­tis

Loss of co­or­di­na­tion is one of the most com­mon symp­toms of EPM along with mus­cle atro­phy af­fect­ing only one side of the horse, says Dr. John­son. EPM horses may also show signs of back brain­stem im­pair­ment, such as par­tial fa­cial paral­y­sis and trou­ble swal­low­ing.

Di­ag­nos­tics: Blood and spinal-fluid tests to look for an­ti­bod­ies to the EPM­caus­ing par­a­site. Both tests are recommended be­cause in ar­eas where EPM is preva­lent, it’s not un­com­mon for 50 per­cent or more of the equine pop­u­la­tion to have an­ti­bod­ies to the dis­ease. That could cause a pos­i­tive blood test even if a horse isn’t in­fected, ex­plains Dr. John­son. If the an­ti­bod­ies are also present in spinal fluid at an in­creased level com­pared to blood, that pro­vides a much more ac­cu­rate di­ag­no­sis, she says.

Equine Her­pesvirus-1

EHV-1 is more com­monly seen in out­breaks in­volv­ing a number of in­di­vid­u­als, says Dr. John­son. So if mul­ti­ple horses in an area start ex­hibit­ing sim­i­lar symp­toms, that’s an in­di­ca­tion this dis­ease could be the cul­prit. Af­fected horses may run a fever and lose con­trol over when they uri­nate or pass ma­nure (uri­nary and/or fe­cal in­con­ti­nence). They may show weak­ness in their tail mus­cles. The back legs are more of­ten af­fected, which can lead to the horse hav­ing trou­ble ris­ing and, in­stead, tak­ing on a “sit­ting dog” po­si­tion part­way up.

Di­ag­nos­tics: Poly­merase chain-re­ac­tion tests to iden­tify the virus in blood sam­ples or nasal swabs. (A PCR test al­lows the vet to an­a­lyze vi­ral DNA even when very small amounts are present in a sam­ple.)

Wob­bler Syn­drome

Of­fi­cially known as cer­vi­cal ver­te­bral stenotic myelopa­thy or cer­vi­cal ver­te­bral mal­for­ma­tion, “wob­blers is a prob­lem with the ver­te­bral col­umn in the re­gion of the neck,” says Dr. John­son. Specif­i­cally, ab­nor­mal ver­te­brae cause com­pres­sion on the spinal

cord, which can block nerve sig­nals.

“Symp­toms tend to be in all four limbs, al­though they may be more ev­i­dent in the back legs,” says Dr. John­son. She adds that the dis­ease can look a lot like EPM, but wob­bler horses might have neck pain while EPM horses won’t.

Di­ag­nos­tics: Blood and spinal-fluid tests to rule out EPM, ra­dio­graphs to elim­i­nate a ver­te­bral frac­ture and show ver­te­bral changes sug­ges­tive of wob­bler syn­drome and/or a myel­o­gram (see side­bar on page 55) to iden­tify pres­sure on the spinal cord.

Eastern and Western Equine En­cephalomyeli­tis, West Nile Virus

These mos­quito-borne dis­eases all af­fect the horse’s spinal cord and brain, says Dr. John­son. “They have symp­toms in­dica­tive of brain prob­lems—weird be­hav­ior, they may lose the abil­ity to stand up, they may have fevers,” she adds. The horse may also ex­hibit head-press­ing (lit­er­ally, the horse presses his head against a sur­face such as a stall wall) and aim­less wan­der­ing, lose his ap­petite, ap­pear de­pressed, have im­paired vi­sion or show mus­cle twitch­ing and hindlimb weak­ness. Dr. John­son notes that horses with West Nile virus may present with more spinal symp­toms than EEE or WEE horses but al­most al­ways have brain signs as well.

Di­ag­nos­tics: Blood and spinal-fluid tests are taken by your vet­eri­nar­ian.

Next Steps

Since it may take days to get re­sults from di­ag­nos­tic tests (and even then more ad­vanced test­ing may be needed), your vet may start your horse on an ini­tial treat­ment plan im­me­di­ately. This might in­clude ther­a­pies di­rectly aimed at the sus­pected dis­or­der (see side­bar on page 56). Or it may fo­cus on sup­port­ive treat­ments—such as in­tra­venous flu­ids or anti-in­flam­ma­to­ries—to keep your horse com­fort­able and as sta­ble as pos­si­ble un­til a fi­nal di­ag­no­sis is made.

This in­her­ent de­lay in the process is just one more rea­son it’s im­por­tant for you to know the symp­toms of neu­ro­log­i­cal trou­ble. Then you can start the ball rolling quickly on a di­ag­no­sis so treat­ments can be­gin and your horse can start his jour­ney to re­cov­ery.

ABOVE: If your vet thinks that your horse could have a neu­ro­log­i­cal is­sue, she will per­form tests to as­sess his strength and co­or­di­na­tion, such as pulling his tail gen­tly to the side when he’s walk­ing and see­ing if it af­fects his bal­ance.

RIGHT: A horse suf­fer­ing from a neu­ro­log­i­cal dis­or­der can of­ten ap­pear weak and un­steady on his feet.

Be­cause neu­ro­logic dis­or­ders of­ten af­fect the horse’s spinal col­umn and sub­se­quently his limbs, you might no­tice him stand­ing in an un­usual wide-legged po­si­tion or even stum­bling or cross­ing his legs when he walks.

If a horse’s neu­ro­logic prob­lem is in the brain stem, he could have a strange droop­ing or asym­met­ri­cal ap­pear­ance to his fa­cial fea­tures, sim­i­lar to a person who had a stroke.

To check a horse’s fa­cial re­flexes, a vet may test a men­ace re­sponse by mov­ing her hand quickly to­ward his eye to see if he blinks.

To check your horse’s body re­flexes, a vet will likely con­duct a neck stretch test in both di­rec­tions (usu­ally with a car­rot as an in­cen­tive) to ob­serve the sup­ple­ness of the neck and rule out any pos­si­ble trauma or arthri­tis con­cerns.

Your vet may want to watch your horse walk up or down a hill or on un­even sur­faces in or­der to an­a­lyze his gait and pos­ture and note any stum­bling or weak­ness.

One of the best ways to de­ter­mine if your horse has sus­tained a frac­ture is for your vet to take ra­dio­graphs of his spine or skull.

Blood tests can help with proper di­ag­no­sis of neu­ro­logic dis­eases such as EPM, EHV-1, EEE, WEE and West Nile virus.

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