EQUINE VETERINARY EDUCATION / AE / AUGUST 2019


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a)


b)


c)


d)


Fig 1: Most important anatomical structures for nerve blocks used in equine dentistry. a) Infraorbital foramen for infraorbital nerve block, b) caudal entrance of infraorbital canal for maxillary nerve block, c) mental foramen for mental nerve block and d) mandibular foramen for inferior alveolar nerve block.


maxillary, mandibular, infraorbital and mental nerve blocks with their relevant anatomical foramina. The infraorbital and mental nerves are desensitised outside the infraorbital and mental foramina for procedures involving the mandibular and maxillary soft tissues, such as treatment of soft tissue trauma in these areas. For painful procedures involving the incisor teeth (such as extraction in equine odontoclastic tooth resorption and hypercementosis), mandibular or maxillary fractures of the incisive (premaxillary) bone or extraction of the first cheek teeth, the infraorbital or mental nerve should be desensitised inside the respective foramina because of branching nerves to these structures. Figure 2a shows the localisation of the infraorbital foramen, relative to the surrounding structures (rostral edge of the facial crest and nasoincisive notch).


Maxillary nerve block Several techniques for the maxillary block have been described in various studies: Bardell et al. (2010) described two approaches for the maxillary nerve block in equine


a) b)


cadavers with different orientations of the needle (perpendicular vs. angled needle placement in relation to the skin). Staszyk et al. (2008) compared a superficial approach (superficial advancement of the needle into the extraperiorbital fat cushion underneath the masseter muscle) to a deep approach (deep advancement of the needle into the pterygopalatine fossa of the palatine bone). The advantage of the superficial technique is the decreased risk of haemorrhage, because the major vascular structures (infraorbital artery, deep facial vein and descending palatine artery) are located close to the palatine bone. Nannarone et al. (2016) described a retrograde maxillary


nerve perineural injection within the infraorbital canal towards the maxillary foramen using a Tuohy needle, thereby avoiding the periocular region and possibly the described complications (Tremaine 2007; Staszyk et al. 2008). For surgical procedures involving the paranasal sinuses


and the nasal cavity, a maxillary nerve block will in some instances not be sufficient due to sensory innervation of these structures by the ophthalmic branch of the trigeminal nerve


Fig 2: Anatomical localisation of the infraorbital and mandibular foramen. a) Anatomical structures (rostral edge of the facial crest and nasoincisive notch) and handsetting to determine the infraorbital foramen. b) Determination of position of the mandibular foramen using perpendicular lines through occlusion of the maxillary and mandibular cheek teeth and the lateral canthus of the eye.


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