2.9 Nerve supply to the face

Question 1

Core Information

Sensory supply:

Answer 1

the sensory supply to the face is provided mainly by the three
divisions of the fifth cranial nerve, the trigeminal.

(As the largest cranial nerve it also supplies much of the scalp, the mouth, teeth and the nasal cavity.)

The skin over the parotid gland and the angle of the mandible is, however,
supplied by the greater auricular nerve, which arises from the ventral rami of the

second and third cervical nerves.

Question 2

Trigeminal nerve divisions

Answer 2

At the trigeminal (Gasserian) ganglion, the nerve separates into the
ophthalmic (V1),
the maxillary (V2)
mandibular (V3)
divisions.

Question 3

Ophthalmic (V1)

Answer 3

the ophthalmic nerve supplies the
skin of the nose, the
forehead, eyelids and the scalp.

(It also supplies the globe, the lacrimal apparatus and the conjunctiva.)

The nerve divides just before the superior orbital
fissure into the lacrimal, nasociliary and frontal branches.

The large frontal branch divides further into the supraorbital and supratrochlear nerves.

The supraorbital nerve supplies the skin of the forehead and scalp,
sometimes as far back as the lambdoid suture.

The supratrochlear nerve supplies part of the
upper eyelid and the skin of the lower part of the forehead near the midline.

The lacrimal nerve supplies the skin adjacent to the medial canthus of the eye,
and the nasociliary nerve and its branches supply the skin of the nose down as
far as the alae nasae.

Question 4

Maxillary (V2)

Answer 4

This runs below the ophthalmic branch before leaving the base of
the skull via the foramen rotundum to divide into its various branches.

The zygomatic nerve divides further on the lateral wall of the orbit into a zygomaticotemporal
branch which supplies the skin of the temple, and a zygomaticofacial
branch which supplies the skin over the cheekbones.

The maxillary nerve proper crosses the pterygopalatine fossa to enter the infraorbital canal, from which it emerges through the infraorbital foramen as the infraorbital nerve.

This supplies the skin of the lower eyelid, the cheek and upper lip.

Question 5

Mandibular

Answer 5

Mandibular (V3): its large sensory root passes through the foramen ovale with
branches that include the auriculotemporal, lingual and buccal nerves.

The auriculotemporal nerve emerges from behind the temporomandibular joint to
supply the skin over the tragus and meatus of the ear as well as the skin over the
temporal region.

The mandibular division also provides the inferior dental nerve,
and one of its terminal branches, the mental nerve, emerges through the mental
foramen in the mandible to supply the skin of the chin and lower lip.

Question 6

Clinical Information

Answer 6

some of the nerves of the face are at risk from pressure
(such as the supraorbital nerve in the prone position),

some may be affected by disease processes such as herpes zoster
(ophthalmic branch of the trigeminal nerve)

+

trigeminal neuralgia.

Question 7

LA surgery to face

Answer 7

The supraorbital and supratrochlear nerves can be blocked a few millimetres above
the supraorbital ridge. If the injection is made too close to the eyebrow it increases
the risk of periorbital haematoma. Alternatively, a single insertion point can be used
in the midbrow region to allow bilateral blocks

The infratrochlear nerve can be blocked by a needle directed along the medial wall of
the orbit via an insertion site about 1 cm above the inner canthus

The infraorbital nerve can be blocked as it exits the infraorbital foramen, which lies
about 1.5 cm (a finger’s breadth) below the inferior orbital margin in line with the
pupil. The nerve can also be blocked by an intra-oral approach, injecting above the
canine (third) tooth.

The mental foramen, conveniently, is also in line with the pupil and the mental nerve
can be blocked in the midpoint of the mandible (although the height of the foramen
varies with age, being nearer the alveolar margin in the elderly)

The superficial branches of the zygomatic nerve can be blocked by subcutaneous
infiltration or by injection at their sites of emergence from the zygoma.

The auriculotemporal nerve is blocked over the posterior aspect of the zygoma, and
the greater auricular nerve by infiltration over the mastoid process behind the ear.

Relatively small volumes of 3–5 ml of local anaesthetic will usually be sufficient to
block all these nerves described.