Face, scalp and facial nerve
Scalp, Face, Facial Nerve and Muscles of Facial Expression
Scalp and face for FCPS Part 1: the five scalp layers, facial muscles, the facial nerve's course and branches, parotid relations, facial vessels and lymph. Explains scalp bleeding, facial palsy patterns, Frey syndrome and lip cancer spread.
One of the most tested topics in past papers
Scalp layers
| Layer | Clinical point |
|---|---|
| Skin | Hair follicles, many sebaceous glands (sebaceous cysts) |
| Connective tissue (dense) | Vessel walls are bound to the fibrous septa, so cut vessels cannot retract or constrict: profuse bleeding; nerves run here |
| Aponeurosis (galea aponeurotica) | Joins frontalis and occipitalis; a wound through it gapes, especially when cut transversely, because the muscles pull the edges apart |
| Loose areolar tissue | "Danger layer": emissary veins link it to the dural sinuses, so infection spreads inside the skull; blood spreads freely (subgaleal haematoma) |
| Pericranium | Firmly attached at sutures, so subperiosteal blood (cephalohaematoma) is limited to one bone |
- The first three layers move together as the "scalp proper". A superficial wound with closely applied edges has spared the galea; a gaping one has divided it. Palpate the base for a fracture before closing.
- Frontalis has no bony attachment in front; it inserts into the skin of the eyebrows. Blood or fluid in the loose areolar layer therefore tracks forwards into the upper eyelids, giving bilateral periorbital bruising a day after a blow to the vertex. Anterior cranial fossa fracture must still be excluded (CSF rhinorrhoea).
- Arteries: supratrochlear and supraorbital (internal carotid, via ophthalmic) in front; superficial temporal, posterior auricular and occipital (external carotid) at the side and back.
- Sensory: trigeminal branches in front of the ear; greater occipital (C2), lesser occipital and great auricular (C2–C3) behind.
Muscles of facial expression
- All derive from the second pharyngeal arch and are supplied by the facial nerve. They lie in the superficial fascia and insert into skin.
- Orbicularis oculi: palpebral part blinks, orbital part screws the eye shut. Orbicularis oris: closes lips. Buccinator: keeps food between the teeth; pierced by the parotid duct opposite the upper second molar. Frontalis, zygomaticus, platysma and others.
Facial nerve (VII): course and branches
- Motor root plus nervus intermedius (taste and parasympathetic) enter the internal acoustic meatus with VIII.
- In the facial canal of the temporal bone: geniculate ganglion gives the greater petrosal nerve (lacrimal, nasal and palatal glands via the pterygopalatine ganglion); then the nerve to stapedius; then the chorda tympani (taste to anterior two-thirds of tongue; submandibular and sublingual glands via the submandibular ganglion).
- Exits through the stylomastoid foramen; gives posterior auricular, posterior belly of digastric and stylohyoid branches; enters the parotid gland and divides into temporal, zygomatic, buccal, marginal mandibular and cervical branches.
- Newborns: the mastoid process is not yet developed, so the stylomastoid foramen and nerve lie just under the skin behind the ear, vulnerable to forceps pressure. In infant mastoid surgery the incision is placed more posteriorly and superiorly.
- Marginal mandibular branch loops below the mandible; injury in submandibular surgery weakens the lower lip. Incisions are made 2–3 cm below the mandible.
Localising facial palsy
| Lesion | Features |
|---|---|
| Upper motor neurone (stroke) | Lower face weak, forehead spared (upper face has bilateral cortical supply) |
| Lower motor neurone | Whole half of face, including forehead |
| Proximal to geniculate ganglion | Plus dry eye, hyperacusis, loss of taste |
| Between stapedius and chorda tympani | Hyperacusis plus loss of taste |
| At stylomastoid foramen or in parotid | Motor weakness only |
- Bell's palsy: idiopathic LMN palsy; prednisolone within 72 hours; protect the cornea; most recover.
- Ramsay Hunt syndrome: zoster of the geniculate ganglion; ear canal vesicles, palsy, hearing loss.
Parotid gland and the facial nerve
- The parotid lies in front of the ear, enclosed in a tough capsule from the investing layer of deep cervical fascia. Inflammation (e.g. mumps) swells the gland inside this unyielding fascia, so pain is severe and worse on chewing, which compresses the gland. The great auricular and auriculotemporal nerves carry its pain.
- From superficial to deep in the gland: facial nerve, retromandibular vein, external carotid artery.
- Parotid duct (Stensen): crosses masseter about a finger-breadth below the zygomatic arch, turns round its anterior border, pierces buccinator and opens opposite the upper second molar.
- Finding the facial trunk in superficial parotidectomy: the tragal pointer (it lies about 1 cm deep and slightly anterior-inferior to it), the posterior belly of digastric, the tympanomastoid suture.
- Frey syndrome (gustatory sweating): after parotidectomy, cut auriculotemporal parasympathetic fibres (from the otic ganglion) regrow into the sweat glands of the overlying skin, so the cheek sweats and flushes on eating.
- The commonest salivary tumour is pleomorphic adenoma of the parotid; it rarely causes facial palsy. Facial palsy with a parotid swelling suggests malignancy.
Facial vessels and the danger triangle
- Facial artery (external carotid) crosses the mandible at the anterior border of masseter (palpable pulse), runs tortuously to the medial angle of the eye as the angular artery; gives superior and inferior labial arteries.
- Facial vein connects with the cavernous sinus through the ophthalmic veins and through the deep facial vein to the pterygoid plexus. Infection in the "danger triangle" (upper lip and side of nose) can spread to cause cavernous sinus thrombosis.
Sensory supply and lymph
- V1 forehead, upper eyelid, dorsum of nose; V2 lower eyelid, cheek, upper lip, side of nose; V3 lower lip, chin, lower jaw, temple. The angle of the jaw and lower parotid area are C2–C3 (great auricular).
| Region | First nodes |
|---|---|
| Forehead, lateral eyelids, temple | Parotid (preauricular) |
| External nose, cheek, upper lip, lateral lower lip | Submandibular |
| Central lower lip, chin | Submental, often to both sides |
| Back of scalp | Occipital, mastoid |
- Lower lip squamous cell carcinoma (sun-exposed farmers): a lateral lesion spreads to ipsilateral submandibular nodes; a central one may go to submental nodes on both sides.
Remember A gaping scalp wound has cut the galea; blood in the loose layer can reach the eyelids because frontalis has no bony anchor.
Exam trap In an upper motor neurone facial palsy the forehead is spared.
Exam trap Frey syndrome is misdirected auriculotemporal fibres, not facial nerve fibres.
How FCPS asks about this
- Danger layer of the scalp: loose areolar tissue with emissary veins.
- Why scalp wounds bleed so much: vessels held open by dense connective tissue.
- Bilateral eyelid bruising after a vertex blow: frontalis has no bony attachment in front.
- Sweating of the cheek while eating after parotid surgery: Frey syndrome from auriculotemporal fibres.
- Landmark for the facial nerve trunk: tragal pointer.
- Facial nerve injury from forceps in a newborn: no mastoid process yet.
- Lateral lower lip cancer: ipsilateral submandibular nodes; external nose also drains there.
Test yourself on this topic
5 of the 55 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
A 65-year-old farmer has an ulcerated squamous cell carcinoma on the lateral third of his lower lip. Which lymph nodes are most likely to be involved first?
Answer: Ipsilateral submandibular nodes
Lymph from the lateral parts of the lower lip and from the whole upper lip drains to the submandibular nodes, while the central part of the lower lip drains to the submental nodes, often on both sides. Both groups then drain to the deep cervical chain. Lip cancer is usually squamous cell carcinoma of the lower lip, linked to sun exposure in outdoor workers and to smoking. Assessment includes palpation of the submandibular and submental regions.
Lip lymph drainage
- Central lower lip: submental
- Lateral lower lip: submandibular
- Upper lip: submandibular
- Then deep cervical nodes
Remember Only the middle of the lower lip goes to the chin nodes.
Exam trap Central lower lip tumours can spread to both sides of the neck.
Why the other options are wrong
- Submental nodes Receive lymph from the central lower lip, not the lateral third.
- Preauricular (parotid) nodes Drain the forehead, temple and lateral eyelids.
- Supraclavicular nodes A late, second-tier site.
- Retropharyngeal nodes Drain the nasopharynx and posterior nasal cavity.
Four hours after a difficult vacuum delivery, a newborn has a boggy, fluctuant scalp swelling that extends from the forehead to the occiput, crossing the suture lines and shifting with head position. His heart rate is 180/min, he looks pale, and haemoglobin has fallen from 17 to 11 g/dL. Which plane contains the blood?
Answer: Between galea and pericranium
This is a subgaleal haemorrhage. Vacuum traction tears emissary veins, and blood collects in the loose areolar layer between the galea aponeurotica and the pericranium. This space has no suture attachments and extends from the orbital margins to the nuchal lines, so it can hold a large part of a newborn's blood volume, causing shock. A cephalhaematoma is subperiosteal and stops at sutures, and caput succedaneum is oedema of the skin and subcutaneous tissue present at birth.
Subgaleal haemorrhage
- Blood between galea and pericranium
- Crosses sutures, shifts with position
- Can cause hypovolaemic shock
- Risk: vacuum delivery
Remember Boggy, crossing sutures, pale baby: subgaleal bleed.
Exam trap Treat a subgaleal haemorrhage as an emergency: replace volume and check clotting.
Why the other options are wrong
- Within skin and subcutaneous tissue This is caput succedaneum: soft oedema present at birth, not shock.
- Beneath the pericranium This is a cephalhaematoma, limited by sutures.
- Between the skull and dura Extradural blood is intracranial and does not form a shifting scalp swelling.
- Within the subarachnoid space Subarachnoid bleeding is intracranial.
A man has a laceration running from the occiput up to the vertex. In the emergency department, the doctor blocks a nerve at the back of the head midway between the occipital protuberance and the mastoid process. Which of the following nerves is blocked?
Answer: Greater occipital nerve
The posterior scalp up to the vertex is supplied mainly by the greater occipital nerve, the dorsal ramus of C2. It pierces trapezius and runs up with the occipital artery, about a third of the way from the external occipital protuberance towards the mastoid, where it can be blocked. The lesser occipital nerve (ventral ramus C2) supplies the scalp behind the ear, and the third occipital nerve a small area low in the midline of the neck.
Scalp sensory supply
- Front: supratrochlear, supraorbital (V1)
- Temple: auriculotemporal (V3)
- Behind ear: lesser occipital (C2)
- Back to vertex: greater occipital (C2)
Remember Back of the scalp is C2.
Exam trap The scalp below the vertex has no trigeminal supply posteriorly; it is all cervical.
Why the other options are wrong
- Lesser occipital nerve Supplies the scalp behind the ear, not up to the vertex.
- Great auricular nerve Supplies the skin over the parotid, angle of jaw and ear lobe.
- Third occipital nerve Supplies only a small area at the nape.
- Auriculotemporal nerve A branch of V3 to the temple.
Why do scalp lacerations bleed so profusely?
Answer: Fibrous tissue holds cut vessels open
The scalp has a rich blood supply from both external and internal carotid branches, which anastomose freely. The vessels run in the dense connective tissue layer, where the fibrous tissue keeps their cut ends open and stops them retracting, so they bleed heavily. Suturing the wound through the full thickness, including the galea, compresses the vessels and controls bleeding.
Scalp bleeding
- Vessels in dense connective tissue
- Held open, can't retract
- Rich anastomoses from both carotids
- Close in layers to compress
Remember Held open, so it keeps flowing.
Exam trap A gaping wound means the galea aponeurotica is divided.
Why the other options are wrong
- The scalp has arteries but no veins Veins are present.
- Scalp arteries lack muscle in their walls Their walls are normal.
- Bleeding comes from the skull bone Usually from scalp vessels.
- Platelets do not work in the scalp Clotting is normal.
Two men have transverse scalp lacerations over the forehead. In one, the wound edges lie close together; in the other, they gape widely. Which of the following does the gaping wound most likely indicate?
Answer: The galea aponeurotica has been divided
The galea aponeurotica joins the frontal and occipital bellies of occipitofrontalis. Superficial wounds that do not reach it stay closed because the skin is firmly bound to the galea by dense connective tissue. Once the galea is cut, especially transversely, the pull of occipitofrontalis separates the edges. A gaping scalp wound therefore needs the galea repaired as a separate layer to restore muscle function and reduce bleeding.
Galea and wound gaping
- Galea joins frontal and occipital bellies
- Cut galea: muscle pulls edges apart
- Transverse wounds gape most
- Repair galea as separate layer
Remember A gaping scalp wound has cut the galea.
Exam trap Always palpate the skull in the wound base for a fracture before closing.
Why the other options are wrong
- The pericranium has been stripped Stripping pericranium does not make the wound gape.
- Only the skin has been cut Skin-only wounds remain closed.
- The dense connective tissue is intact The dense layer is above the galea; intact galea keeps edges together.
- The skull has been fractured Gaping depends on the galea, not on bone.
Where this sits in the CPSP syllabus
- Paper 1: Head, neck and back, Scalp, face, facial nerve and muscles of facial expression
- Surgery & Allied, Paper 2: Head and neck, Scalp, face, facial nerve and muscles of facial expression
Read next
Drug dose pages
Doses, cautions and practical tips for drugs in this chapter.