Content area
Full Text
What is headshaking?
There are many possible reasons why a horse may shake its head, including poor riding technique, challenging behaviour, the presence of a foreign body in its nasal passages, dental pain, or even back pain. Facial pain or dysaesthesia (abnormal sensation) certainly appears to be a reason for a horse to shake its head. Facial pain may be present as a result of detectable gross pathology, such as a periapical abscess of a tooth, or unfortunately in the majority of headshakers it is due to a trigeminal neuropathy of unknown cause (Lane and Mair 1987); now best described as idiopathic trigeminal-mediated headshaking.
Trigeminal-mediated headshaking
Trigeminal-mediated headshaking appears to be acquired, with the age range of onset usually being that of a young adult (in my experience most commonly five- to 10-year-old horses) and there is some evidence to suggest it may be more common in geldings (Madigan and Bell 2001). Anecdotally, signs are often acute in onset (to the point that owners can often give you an exact date and time) but some may be insidious. A classic history that an owner may give is that while out riding ‘a bee flew up the horse’s nose, he went crazy and has never recovered’. The classical clinical signs usually involve predominantly vertical head and neck movements, often with some sharp vertical twitches or flicks and accompanied by signs of nasal irritation such as snorting, twitching lips, rubbing the nose and striking at the nose. Both sides of the face usually appear to be affected.
Clinical signs may occur at rest but are usually worse at exercise and would be more extreme outdoors than indoors. The onset of clinical signs may be seasonal (around two thirds of affected horses only show clinical signs in the spring and summer, Madigan and Bell 2001) and, if so, horses usually appear to be affected more in the spring or summer.
There is little longitudinal data available so we currently rely on anecdotal evidence. It seems that spontaneous remission is rare but not impossible. Instead, horses are often reported to progress in the clinical signs for the first few weeks and then plateau.
From this information, we can assume that the condition is acquired....