Equine head block

For this image, list the nerves labelled.

A - supraorbital (frontal)

E- palpebral

F - auriculopalpebral

G+H - infraorbital

I+K - mental

For this image, what nerve would blocking each area effect?

A - supraorbital (frontal)

B- lacrimal

C- infratrochlear

D- zygomatic

E- palpebral

F- auriculoplapebral

 

List the different peri-orbital blocks that can be done on the horse head. (5)

• Supraorbital (frontal)

• Lacrymal

• Zygomatic

• Infratrochlear

• Palpebral

• Retrobulbar

All following questions are about the supraorbital (frontal) nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Frontal nerve (CN 5), sensory and motor.

Desensitisation of the middle 2/3 of upper eyelid and skin from there to forehead midline. Can inhibit motor function of the upper eyelid (palpebral -> auriculopalpebral -> CN 7

Use 35G x 16mm needle. 2ml local anaesthetic.

Locate nerve, it emerges from supraorbital foramen. Inject perpendicular to skin, aspirate to ensure not in the artery also emerging from fossa.

All following questions are about the lacrymal nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

 

Blocks lacrymal nerve (CN 5).

No sensation in the lateral canthus, temporal angel of orbit and lateral upper eyelid.

25G 16mm needle. 2ml local anaesthetic.

Inject subcutaneously around rostromedial border of the supraorbital process.

All following questions are about the zygomatic nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Zygomatic branch of CN 5

Anaesthesia of the middle 2/3 of lower eyelid.

25G 16mm needle, 2-3ml local anaesthetic.

Inject subcutaneously at most ventral aspect of bony orbit, and along the ventral border.

All following questions are about the infratrochlear nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Infratrochlear branch of CN 5.

Anaesthesia of medial canthus, medial upper and lower eyelids.

25G 16mm needle, 2ml local anaesthetic.

Subcutaneous injection, around rostrodorsal aspect of orbital rim. Notch is palpable.

NOTE - DEEPER INJECTION CAN LEAD TO ANAESTHESIA OF THIRD EYELID.

All following questions are about the palpebral nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Palpebral branch of CN7 (motor only)

Horses unable to close eyelids (use corneal protection)

25G 16mm needle, 2ml anaesthetic

Palpate nerve as t runs over dorsal point of zygomatic arch. Inject subcutaneously, adjacent to nerve.

 

(there is also a second option, auriculopalpebral block on ventral border of zygomatic arch, here, inject 5ml)

All following questions are about the retrobulbar nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Many nerves!

Optic, oculomotor, trigeminal, abducent.

Motor blockade of extra ocular and ciliary body. Sensory blockade of periorbital skin, fascia, and eyeball. May leave some movement in upper eyelid.

 

19G 19mm needle

Enter supraorbital fossa, advance needle ventrally until it reached the retrobulbar space. Eye will rotate dorsally as needle enters dorsal fascia of retrobulbar space. 10-20ml LA.

List the different dental and muzzle block that can be done in the horse. (4)

• Infraorbital nerve

• Maxillary nerve

• Mental nerve

• Mandibular nerve

All following questions are about the Infraorbital nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Maxillary branch of CN 5, emerges at infraorbital foramen. (between incisive notch and rostral facial crest)

Desensitises skin rostroventral to injection site - upper lip, nostril, roof of nasal cavity.

23G 16m needle, 3-5ml LA.

Displace bellies of levator labii Sup and levator nasolabialis. Insert needle over foramen.

• Can also infiltrate the canal with LA using a 25-38mm needle, extending anaesthesia to upper incisors, canaine and PM 2.

All following questions are about the maxillary  nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Maxillary branch of CN 5.

Anaesthesia of all maxillary teeth and associated structures + infraorbital block nerves.

19G 75mm needle. 10 ml LA.

Insert needle caudal to the bony orbit where zygomatic process meets supraorbital process to join arch.

Advance needle rostro-medially, slightly ventrally, until you hit bone.

All following questions are about the supraorbital mental nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Inferior alveolar branch of mandibular CN 5.

Desensitisation of lower lip and incisors (rostral to injection point).

25G, 16mm needle. 5ml LA.

Palpate mental foramen, displace depressor labii inferioris. Inject.

All following questions are about the mandibular nerve block in a horse.

• What nerve is this blocking?

• What is the result of this

• What equipment should be used

• How do we go about it?

Inferior alveolar branch, mandibular division of CN 5.

Anaesthesia of all teeth in mandibular arcade. Also mental nerve block.

14G 13cm spinal needle! 10ml LA.

 

Can approach from either ventral border, sliding needle dorsally against medial surface of the mandible, or from caudal border of the vertical ramus, directing needle rostrally.