Wednesday, April 19, 2006
Headshaking Syndrome....Just the facts
Just to set the record straight....this is a SYNDROME. That means it is a condition with multiple potential causes that has a unique set of symptoms. In this case the symptom is head shaking, this is either horizontal, vertical or rotary and frequently resembles a nervous twitch. Sometimes this is so uncontrollable that the behavior becomes almost manic and dangerous. Over the years many different causes have been attibuted to causing head shaking syndrome, including (1) ear mites (2) allergic rhinitis (3) ocular disease (4) Trigeminal neuritis (5) dental disease and (6) photic headshaking. One, from the fever swamps of the internet, links it to vaccines ( see my previous post about my thoughts on holistics) One older study noted that these horses were frequently over 8 years of age, Throughbred or Warm Blood, owned by 40+ year old women used for hunter/jumper or dressage. Additional studies have linked this to the time of year (seasonal) and most recently, to bright sunlight and body color ( chesnut with a large white blaze). All of this would tend to make you think that nobody knows what in the hell is going on......hence a "Syndrome". If you take a step back and look at this logically it might help. Horses like any animal can shake their head for many,many reasons. I frequently do it when talking to some of my clients, but thats for another post. When I was at Cornell I saw more of these than I could count and the cause usually went unconfirmed, however many responded to a change in location and frequently intra-nasal steriods, hhhmmmmm. That sure sounds like allergy doesn't it., but this doesnt explain all of them since others didn't respond. A great study done at UC Davis found a link between headshaking and photic sneezing in people ( sun sneezing). In this study it was shown that bright sunlight, usually in the spring, caused these horses to show headshaking and even go as far as to put their heads in open barrels or in the tail of another horse to shield them from the light. .These stimuli appear to hyperactivate the trigeminal nerve resulting in a nasal irritation. This is believed to be similar to the photic sneeze syndrome in humans. The light or sound-induced headshake is a more violent and irregular, snorting toss, compared to the more rhythmic traditional head bobbing or nodding seen as a classic stereotypy. The horse may appear to be trying to scratch its nose on a foreleg or even on the ground as it snorts, even going along at a Trot
. This form of headshaking almost always worsens under work, and immediately subsides as the animal is returned to the quiet and dark barn or rest, so is easily misinterpreted as a purely behavioral problem. In most cases, light-induced headshaking is seasonal, and will stop immediately when the eyes are covered or the area is darkened. Dark goggles or sun-blocking face masks may be all that is needed for some individuals. Wow.
Additionally , a group at Univ of Penn. blocked the trigeminal nerve ( in the face) and stopped many of the signs, however , surgical transection of the nerve caused some horses to rub their noses off....a significant complication.
To date there are several ways to treat these horse and most are medical. Cyproheptidine, an anti-histamine that effects serotonin levels has been the best, also the addition af a behavior modifiying drug Carbamizine has been shown to help. I think these work in cases where the cause is more photic in origin or behavioral ( like tick disorders in people) . If the cause is more allergic then the use of intra-nasal steriods ( Azmacort, 5-10 metered doses daily) seems to be effective. Others have used panty hose over the horses nose as well as the leather tongs/strips over the nose to eliminate these signs. I feel the ones that rub their noses on the riders and snort while riding are the harder ones to treat and frequently are the most violent while riding. If you have a horse that suffers from this I would encourage you to seek out someone with experience with this disorder or have your Veterinarian send me a note and I will forward some info on the subject. As always , use your mind and don't fall victim to those that are marketing /selling a cure-all. There isn't one, this problem has multiple causes and that means no one treatment will do it. You just might find yourself shaking your head wondering where all the money went.