Auriculopalpebral nerve block

• The orbicularis oculi muscle causes tight lid closure, especially in painful eye conditions, and eyelid akinesia and anesthesia may be essential for complete examination of the eye.
• The auriculopalpebral nerve, a branch of the facial nerve, is a motor nerve supplying the orbicularis oculi muscle, the frontalis muscle (which provides some muscling to the upper eyelid) and the external muscles of the ear.
• Cattle do not have a corrugator supercilii muscle, which is otherwise known as the levator anguli oculi medialis, but use their frontalis muscle for the same purpose.
• The auriculopalpebral nerve runs from the base of the ear along the dorsal aspect of the zygomatic arch, past and ventral to the eye, giving off branches along its route.
• When blocked, this allows manipulation of the eyelids without undue pressure on a painful globe.

Uses

• To facilitate examination of the eye especially in painful conditions.
• To control eyelid movement during minor surgical procedures.

Advantages

• Provides excellent eyelid akinesis.
• Can be used in conjunction with sedation and other regional blocks.

Disadvantages

• The auriculopalpebral block is purely a motor block and does not remove sensation.
• As such it can be used for ocular examination, but should not be used alone as analgesia for any form of ocular surgery.
• The supraorbital, lacrimal, infratrochlear and zygomatic nerves require blocking to remove all periocular sensation.
• As well as the orbicularis oculi muscle, the palpebral nerve supplies motor innervation to the frontalis muscle so that it may sometimes appear that the strongest motor block is apparent in the upper eyelid.
• The supraorbital, lacrimal, infratrochlear and zygomatic nerves require blocking to remove all periocular sensation.
• To block motor activity of the levator palpebrae superioris and the extraocular muscles controlling globe movement, cranial nerves III, IV and VI require blocking.
• Block of the more proximal auricular part of the auriculopalpebral nerve is occasionally achieved, inadvertently, when performing this block – noted by drooping and akinesia of the ipsilateral ear pinna.

Alternative techniques

• With the advent of consistent and effective sedatives Sedating cattle, especially the alpha 2 agonists, the need for auriculopalpebral blocks is reduced.

Time required

Preparation

• Sedation may be necessary in some difficult cases to allow the nerve block to be carried out: 5-15 min.
• Skin preparation (usually minimal): 2-3 min.

Procedure

• 1-2 min.
• Effective in 5-10 min.

Decision taking

Criteria for choosing test

• Examination of the eye especially where increased ocular pain and blepharospasm are present.
• Facilitate minor surgery such as third eyelid removal, in conjunction with topical local anesthesia and other nerve blocks.