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Neurectomy

Neurectomy is a medical term describing the cutting of a nerve. Bilateral infraorbital neurectomy can be an effective treatment for horses with headshaking. A positive response to an infraorbital nerve block can indicate that transection of the infraorbital nerve (on both sides of the face) may be a useful treatment option. A positive response is obtained when the symptoms of headshaking improve following the nerve block. This procedure is usually reserved for horses that have not responded to all other available treatments. It is not without risks and can cause nasal irritation (short and long term). Rubbing of the nostrils is a not infrequent complication of this surgery, but in most cases this is a temporary problem. Some horses may take a period of a few days to a few weeks to fully adjust to the loss of sensation around the upper lip and cheek. Source: Annabel Ensor. BVSc.: link

Neurectomy is the irreversible cutting of the trigeminal nerve or one of its branches. Cutting the infraorbital nerve may be performed if pain is limited to the area below the eye along the upper cheekbone. Cutting the nerve causes permanent numbness of the region that the nerve supplies and should only be considered when all other treatments have failed to control pain. Infraorbital neurectomy is performed via an intraoral incision in the labiogingival sulcus. The infraorbital nerve is avulsed well into the infraorbital foramen. Sectioning of the inferior alveolar nerve is accomplished within the inferior alveolar canal. Loss of facial sensation in the relevant division is inevitable, but corneal sensation is left intact. Dysesthesias sometimes appear.

Assessment of bilateral infraorbital nerve blockade and bilateral infraorbital neurectomy in the investigation and treatment of idiopathic headshaking

T. S. MAIR, Bell Equine Veterinary Clinic, Mereworth, Maidstone, Kent, ME18 5GS, UK.

The infraorbital nerve is part of the maxillary branch of the trigeminal nerve. It traverses the infraorbital canal, emerges from the infra orbitat foramen, and divides into nasal and superior labial branches. The infraorbital nerve supplies sensory innervation to the ipsilateral upper lip, cheek, nostril and gums to the level of the first cheek teeth. Infraorbital neurectomy has

been performed for many years as a treatment for headshaking (Tutt 1946; Mair et al. 1992) but there have been few reports of its efficacy. In an earlier study, bilateral infraorbital neurectomy was used in 7 horses affected by the idiopathic headshaking syndrome (Mair et al. 1992). The neurectomy provided sustained relief from headshaking in 3 of 7 horses, but in one of these a reaction at the neurectomy site necessitated a further surgical procedure after 6 months. A fourth horse was reported to be partly improved following neurectomy. The use of an infraorbital nerve block has been described as a useful diagnostic tool in the evaluation of headshakers (Cook 1980; Wilkins et al. 1993; Wilkins 1997b). A positive response to the block has been interpreted as an indication that the horse is being irritated in some manner in the area supplied by this nerve (Wilkins 1997b). The response to such a nerve block has also been used to assess the potential value of infra orbital neurectomy.

The purpose of this study was to review the results of bilateral infraorbital nerve blocks and neurectornies in 19 horses affected by the idiopathic headshaker syndrome. The correlation between results of the nerve blocks and of neurectornies was also examined. Equine Veterinary Journal Vol 31, 1999

Bilateral infraorbital neurectomy provided sustained relief in three of seven horses, but in one of these cases, a reaction at the neurectomy site necessitated another surgical procedure after six months. A fourth horse was reported to be slightly improved after neurectomy. A period of nasal irritation resulting in self-inflicted trauma was a common complication of this surgery. Mair TS, Howarth S, Lane JG.  1992,  PMID: 9109952

Infraorbital neurectomy resulted in an initial loss of sensitivity at all frequencies, followed by a gradual return of sensation which reached preoperative levels at approximately one year. The return of sensitivity was followed by the return of neuralgia.  Verrillo RT, Ecker AD. 1977, PMID: 876675

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