Page 10 - Clinical Connections - Spring 2024

RVC RESEARCH STUDY VETERINARY SERVICES RVC.AC.UK
Equine

HEADSHAKING – TREATMENT OVERVIEW

Melanie Perrier, Senior Lecturer in Equine Soft Tissue Surgery

ccasional shaking of the head Transverse image at the level of the mandibular used. Cyproheptadine, a centrally acting
may be normal, however when 08s cheek teeth. There is a complete antihistamine and serotonin antagonist, is
O becoming frequent, violent and longitudinal fracture along 308 (arrowheads), used, but research findings on efficacy are
dividing it into two big fragments and exposing
when affecting riding or handling the horse, the pulp canals that show a heterogeneous mixed.
a pathological process must be considered. appearance with gas Magnesium may have neuroprotective
Conditions which can cause headshaking effects on nerve firing that potentially
include otitis interna, cranial nerve dampen signs of neuropathic pain. In one
dysfunction, cervical injury, ocular disease, study, intravenous infusion of magnesium
guttural pouch mycosis, dental disease, sulphate was used in six horses with
sinusitis and behavioural or rider issues. headshaking signs. Horses were evaluated
In 98% of cases, when no physical up to two hours after IV Mg infusion and an
cause could be determined, headshaking increased in magnesium blood levels was
is classified as idiopathic headshaking. noted. This resulted in a 29% reduction in
Idiopathic headshaking is a complex headshaking.
pathology, which can be frustrating for both Sodium cromoglycate eyedrops have
owner and veterinarian. also been used for their mast cell stabilising
Trigeminal mediated headshaking or properties. Three seasonally affected
idiopathic headshaking is defined as horses were treated and all returned to
an acquired disorder of the horse. The ridden exercise.
headshaking is typically worst at exercise Percutaneous Electrical Nerve
with only some horses being affected also at Stimulation (PENS) is a treatment translated
rest. Seasonality of clinical signs has been from electrical nerve neuromodulation.
reported in about 60% of cases, the majority As such it may normalise neural function.
being in spring and summer. Complication rates were reported in up
CT is a useful tool to rule out primary to 8.8% of cases and are usually mild
Diagnosis disease for which treatment could result and transient. Remission of headshaking
The diagnosis is usually one of exclusion in improvement of headshaking. An RVC following the initial course occurred in 53%.
and should include a complete physical study found that, in more than 20% of the Median length of time recorded in remission
examination and a ridden examination. cases, a treatable primary condition was was 9.5 weeks.
Further diagnostics may include dental identified – leading to complete resolution of PENS is believed to be a good first-
examination, dental endoscopy, otoscopy, clinical signs. line treatment for horses which do not
maxillary nerve block (if the clinical signs Clinically relevant primary diseases respond to a nose net. More recently,
are reproducible and consistent), upper in that study included dental fracture, electroacupuncture has been used to
airways endoscopy, skull radiographs and primary sinusitis, temporo-mandibular joint modulate perception of afferent nociceptive
Computed Tomography (CT). arthritis, nuchal bursitis, musculoskeletal stimuli by inhibiting afferent pain signals
pathologies, basisphenoid fracture, otitis and by activation of descending inhibitory
Transverse (A) image of the head of a horse
with marked enlargement of the left infraorbital externa and a mass affecting the infra- pathways. Electroacupuncture is believed to
nerve (white arrows) that is causing expansion orbital nerve. be less invasive than PENs and may yield
and thickening of the infraorbital canal wall similar results.
Treatment Finally, surgical treatment includes
While several treatments are available, bilateral infraorbital neurectomy, which has
success rates are extremely variable. There been associated with serious side effects,
is also considerable placebo effect when and caudal ablation of the infraorbital nerve
interpreting results of treatments and many via coil compression. This procedure has
unpublished treatments used by owners. been shown to yield 50% success rate in 57
Among treatment used, nose nets are horses, with 26% relapsing within a median
found to be cheap, non-invasive, risk-free time of nine months. Most horses developed
and allowed in most competition at most side effects of nose rubbing, which was
levels. They are reported to give up to 70% deemed short-term in most cases, but in
relief in 25% cases and are believed to act four of 58 cases, horses were euthanised
through the gate control theory. due to severity or nonresolution of these
The drug gabapentin is used in side effects.
equine headshaking but it has poor
bioavailability and only anecdotal reports
of success. Carbamazepine, which
reduces central nerve conduction, is also For equine referrals, please call: 01707
666297
Email:
equinehospital@rvc.ac.uk

10 Spring 2024