Caudal anaesthesia of the infraorbital nerve for diagnosis of idiopathic headshaking and caudal compression of the infraorbital nerve for its treatment, in 58 horses

Abstract

The diagnostic protocol described is recommended for the investigation of headshakers. Caudal compression offers the best prognosis for a successful outcome compared with other treatments, for horses in which the only alternative is euthanasia. Surgical treatment of the disorder requires refinement, and the pathogenesis of the disorder requires investigation.

Validation of the accuracy of needle placement as used in diagnostic local analgesia of the maxillary nerve for investigation of trigeminally mediated headshaking in horses

“…We consider it to be good practice to perform diagnostic local anaesthesia around the maxillary nerve and CNN on presumed idiopathic headshakers (Roberts and others 2013). A marked decrease in headshaking in response to application of diagnostic local anaesthesia around the maxillary nerve and CNN without other pathology in the innervated area will support the diagnosis of trigeminal (maxillary) neuropathy to the veterinarian, the owner of the horse, and may also be used as proof for insurers.…”

“…A diagnosis of facial dysaesthesia can be made by observing a marked decrease in headshaking in response to local anaesthesia of the innervating sensory nerves (Roberts and others 2013, Pickles and others 2014). …”

“…Where no cause of this facial dysaesthesia can be identified on endoscopy, imaging of the head, ophthalmologic and dental examination the dysaesthesia is likely to be neuropathic (Newton and others 2000, Roberts and others 2013). …”

“…The caudal nasal nerve (CNN) branches off the maxillary nerve just proximal to the maxillary foramen and enters the caudal nasal foramen before running towards the dorsal meatus of the nasal cavity to innervate the nasal mucosa (Dyce and others 2002). In previous articles the CNN has been called the ‘posterior ethmoidal nerve’ (Newton and others 2000, Roberts and others 2013), but due to possible confusion with the ethmoidal nerve which branches of the ophthalmic nerve rather than the maxillary nerve we will refrain from using this term.…”

“…The intended site of deposition of the local analgesic is around the maxillary and CNN, (Newton and others 2000, Roberts and others 2013) but accuracy of needle deposition at this location using the approach described by Newton and others (2000) has never been confirmed. Deposition in different locations could explain some of the false negative responses.…”