EQUUS - - Equus -

!n earf ul of trou­ble

Q:For about a year, I had been hav­ing prob­lems with blurred vi­sion and a slight bal­ance is­sue. My doc­tor di­ag­nosed it as an in­ner ear prob­lem. The is­sue turned out to be wa­ter: I had been us­ing a spray noz­zle to rinse my hair, and I would oc­ca­sion­ally get wa­ter in my ears. Once I learned this, I took care to keep wa­ter out of my ear canals and my bal­ance and eye prob­lems both cleared up.

My ques­tion is, can horses have this prob­lem? I am care­ful not to get wa­ter in my horses’ ears while I bathe them, but I know a lot of peo­ple spray their horses’ faces more in­dis­crim­i­nately. Is it pos­si­ble that wa­ter in a horse’s in­ner ear might be mis­di­ag­nosed as a mild case of wob­bles or EPM? Ann Barosh Huntsville, Texas

A:It would be dif­fi­cult to get a sig­nif­i­cant amount of wa­ter into a horse’s ear canal as you were bathing him. In con­trast to the hu­man ear canal, which is short and straight, a horse’s ear canal is long and runs in­ward at an an­gle. Plus, most horses have a fair amount of hair in their ears that pro­tects the open­ing to the canal, which is quite small.

That said, horses cer­tainly can have mid­dle ear and vestibu­lar sys­tem is­sues that re­sult in bal­ance prob­lems. The vestibu­lar sys­tem is the sen­sory mech­a­nism in the in­ner ear that de­tects move­ment of the head and helps to con­trol bal­ance.

Vestibu­lar dis­ease in the horse may re­sult from a num­ber of in­fec­tious, trau­matic and other con­di­tions. Head trauma and tem­poro­hy­oid os­teoarthrop­a­thy (THO) are two of the most

com­mon. THO is a chronic, bony over­growth on the sty­lo­hy­oid bone where it con­nects with the base of the skull at the tem­poro­hy­oid joint, near the mid­dle ear. (The sty­lo­hy­oid bones are part of the hy­oid ap­pa­ra­tus, a set of bones that form a “swing” shape be­low the back of the skull and sup­port the lar­ynx and the base of the tongue.) The cause of the bony over­growth is not com­pletely un­der­stood but it could be due to trauma, os­teoarthri­tis or in­fec­tion spread­ing from the nearby mid­dle ear or gut­tural pouches.

The bony over­growth causes joint fu­sion (anky­lo­sis) of the tem­poro­hy­oid joint. This de­creases the range of move­ment of the joint so ac­tions such as swal­low­ing or mov­ing the neck or head can cause frac­tures at the site of the fu­sion. The re­sult­ing swelling and in­flam­ma­tion put pres­sure on nearby struc­tures and can lead to neu­ro­log­i­cal and other signs, in­clud­ing dis­charge---blood, pus or spinal fluid---from the ear, dif­fi­culty swal­low­ing (dys­pha­gia), a head tilt, in­vol­un­tary move­ment of the eye­balls (nys­tag­mus), mis­align­ment of the eye­ball from its nor­mal po­si­tion (stra­bis­mus), cir­cling, in­co­or­di­na­tion (ataxia) and fa­cial nerve paral­y­sis.

THO is usu­ally di­ag­nosed by an en­do­scopic ex­am­i­na­tion of the gut­tural pouches---the bony over­growths would be clearly vis­i­ble. Other di­ag­nos­tic op­tions in­clude skull ra­dio­graphs and com­puted to­mog­ra­phy.

The gut­tural pouches are unique to a small num­ber of an­i­mal species, in­clud­ing the horse. There are two gut­tural pouches---sacs of air that ex­pand from the eu­stachian tubes---one be­neath each ear. In a ma­ture horse, each gut­tural pouch cav­ity can hold as much as a cof­fee mug. The gut­tural pouches are lined with a very thin mem­brane and be­neath that mem­brane are some crit­i­cal struc­tures, such as ma­jor ar­ter­ies to the head and some of the most im­por­tant nerves in the body. Most of these nerves are cra­nial nerves, so when they are dam­aged, the re­sult­ing clin­i­cal signs re­late to func­tions of the head.

Other po­ten­tial causes of vestibu­lar dis­ease in horses in­clude equine0 pro­to­zoal myeloen­cephali­tis (EPM),

Horses cer­tainly can have mid­dle ear and vestibu­lar sys­tem is­sues that re­sult in bal­ance prob­lems.

ab­nor­mal tis­sue growths (neo­pla­sia), brain ab­scesses, West0 Nile en­cephali­tis, east­ern0 equine en­cephalomye­li­tis (EEE) and par­a­sitic mi­gra­tion.

So while horses do have dis­eases that af­fect their bal­ance, due to dif­fer­ences in their anatomy it would be ex­tremely un­likely for bal­ance is­sues to be caused by get­ting wa­ter into their ex­ter­nal ear canal. Sandra Sar­gent, DVM, DACVD Pitts­burgh Vet­eri­nary Der­ma­tol­ogy Pitts­burgh, Penn­syl­va­nia

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