Face and scalp

Clinical anatomy

The scalp consists of the skin, connective tissue and muscle covering the vault of the skull. It extends from the top of the forehead to the superior nuchal line posteriorly, and projects down to the zygomatic arch and external auditory canal (external acoustic meatus) laterally. For descriptive purposes, the forehead is considered as part of the scalp. Conventionally, the scalp is described as being composed of five layers: thick, hairy skin; richly vascular dense connective tissue; the aponeurosis of occipitofrontalis (galea aponeurotica, epicranial aponeurosis); loose areolar connective tissue forming a potential subaponeurotic space; and pericranium (periosteum on the outer surface of the skull). The three outer layers, the scalp proper, are closely adherent and can be separated from the underlying loose areolar tissue.

The skin of the scalp possesses numerous sebaceous glands and is a common site for sebaceous cysts, some having a familial tendency. In older patients keratin secretion can result in ‘keratin horn’, which has a precancerous tendency.

The scalp is supplied by the external and internal carotid arteries. The fact that their branches anastomose freely has clinical significance. The superficial temporal and posterior auricular arteries supply the lateral scalp; the occipital artery supplies the posterior scalp; the supratrochlear and supraorbital arteries supply the anterior scalp. Scalp lacerations continue to bleed profusely because the elastic fibres of the underlying galea aponeurotica prevent initial vessel retraction. Careful cauterization of these feeding vessels during two-layered repair is essential in order to prevent haematoma formation. The pericranial layer, if involved, cannot usually be closed because it retracts. The anterior branch of the superficial temporal artery in the scalp is the ideal donor site for a temporal artery biopsy (the gold standard to confirm a diagnosis of giant cell arteritis).

The lymphatic drainage of the scalp involves facial, submandibular, parotid, auricular, occipital and superficial cervical nodes. Cutaneous malignancies of the scalp usually metastasize to the parotid lymph nodes and subsequently to the cervical nodes, particularly to level II nodes ( Ch. 15 ). Posterior scalp lesions drain to the occipital lymph nodes.

Occipitofrontalis is innervated by the facial nerve: occipitalis by the posterior auricular branch arising at the stylomastoid foramen and frontalis by the temporal branch. Damage to the latter will result in a ptotic forehead: informed consent must be obtained if any surgical skin excision is to be carried out along the forehead and in raising flaps for temporomandibular and face-lift procedures and for parotid­ectomy. Much of the scalp is innervated by cutaneous branches of the trigeminal nerve. The skin of the forehead and scalp, nearly as far back as the lambdoid suture, is supplied by the supratrochlear and supraorbital nerves (ophthalmic division of the trigeminal nerve). In trigeminal neuralgia, if medical treatment fails to control lancinating pain in the supraorbital nerve dermatome, neurectomy of this nerve may be offered, although it will produce permanent anaesthesia of the affected scalp. The skin covering the temple is supplied by the zygomaticotemporal nerve (maxillary division of the trigeminal nerve) and the auriculotemporal nerve (mandibular division of the trigeminal nerve). The posterior scalp is innervated by the dorsal rami of C2 and C3 (great auricular nerve and third occipital nerve, respectively). The scalp behind the auricle is supplied by the lesser occipital nerve (C2). An expected complication following neck dissection is numbness of the posterosuperior scalp as a result of sacrifice of branches of the cervical plexus, including the lesser occipital nerve ( Ch. 15 ).

Surgical approaches and considerations

Flaps based on the first three scalp layers, including bicoronal and hemicoronal flaps, provide access for trauma and various cranio­facial surgical procedures. Access to the temporomandibular joint and zygomatic arch is via a modified pre-auricular approach (the modified hockey stick incision) described by Al-Kayat and Bramley. This incision with temporal extension is used in a face-lift procedure and in parotidectomy. The Gillies approach, used to elevate zygoma fractures, is based on a temporal incision at a 45° angle 2.5 cm superior and anterior to the helix (avoiding the superficial temporal artery). Dissection is continued down to the deep portion of the deep temporal fascia, which is incised. A zygomatic elevator is introduced deep to the fascia, medial to the depressed arch segment, to elevate the bone and reduce the fracture. If the surgeon keeps to this plane, the frontal branch of the facial nerve is protected and the fascial attachment to the zygomatic arch is undisturbed.

Scalp defects are covered by different types of flap, based on advancement, rotation or transposition ( Fig. 5.1 ). When cutaneous malignancy of the scalp does not involve the pericranium, defects are covered by these different scalp flaps, depending on site. When a scalp flap is not adequate to cover large defects, the exposed pericranium can be covered by either a split-thickness or a full-thickness skin graft.

The scalp can also be used as a large donor site to cover various facial, oropharyngeal and head and neck defects, such as: bilobed scalp flap; galeal pericranial flap ( Fig. 5.2 ); galeal frontalis flap ( Fig. 5.3 ); and forehead island and composite flaps ( Fig. 5.4 ). The majority of the flaps have an axial pattern based on the superficial temporal, supratrochlear or supraorbital arteries and veins. If the external carotid artery is ligated in the neck, as part of the management for head and neck cancer, choosing an axial patterned flap such as a forehead flap would not be reliable. However, raising a bicoronal flap for cranial access is possible because of the rich vascular anastomoses between the internal and external carotid arteries, despite ligating the external carotid artery. In general, the veins have a similar distribution to the arteries; each artery is usually accompanied by a pair of venae comitantes. Scalp veins communicate with intracranial venous sinuses via emissary veins, which pass through various foramina in the skull.

A large scalp defect – for example, one created as a result of avulsion in trauma or malignancy – is covered by composite cutaneous tissues brought in from a distant site as a microvascular transfer. The common flaps are either an anterolateral thigh flap (ALT flap) or a radial forearm fasciocutaneous flap (RFFF). Recipient vessels are usually anastomosed to the superficial temporal artery and vein using 10/0 Ethilon sutures. Where there is inadequate length or a vessel matching problem, a vein graft is placed as an interpositional recipient vessel and the distal end is sutured to vessels in the neck.

The scalp is used as an access site in endoscopic aesthetic surgery. Three vertical incisions down to the parietal bone are placed 2.5 cm posterior to the hair line and two transverse temporal incisions down to the deep part of the deep temporal fascia are placed over temporalis. The dissection will form a tunnel ‘optical cavity’, where instruments and endoscope can be inserted to carry out brow lift.

Calvarial bone ossifies in mesenchyme, which results in lesser resorption and has the potential for early vascularization when used as a reconstructive tissue. Components harvested from the cranial vault for facial reconstruction include the following:

• Full-thickness calvaria is used particularly in children.

• The outer calvaria is an excellent donor site and is commonly used in the reconstruction of orbital wall and frontal sinus defects, and in nasal reconstruction and midface repair ( Fig. 5.5 ).

• Trephined bone is harvested using a craniotomy, particularly when osteoplastic flaps are raised to access the skull base and the brain.

• Skull shavings are versatile filling materials and can be used as a lining if incorporated with the attached pericranium.

• Pedicle flaps, based on superficial temporal, supraorbital or supratrochlear arteries, are used in reconstructing large defects of the orbit or nose, or in congenital deformities: for example, in Treacher Collins syndrome, to reconstruct the zygomatic arches ( Fig. 5.6 ).

When there is involvement of the pericranium, the calvaria will be exposed and additional measures are required to repair the exposed defect. This is done either by drilling multiple holes with a round burr in the outer calvaria so that bleeding can occur from the diploë, or by removing the whole outer calvaria. In older patients, vitality of the outer calvaria is dependent on diploic perfusion; further measures should be taken to achieve scalp healing if perfusion is inadequate. The recent introduction of innovative materials and substitutes such as Integra (Integra®, Integra Life Sciences Corp, Plainsboro, NJ, USA) and ReCell (RECELL® SYSTEM, Valencia, CA, USA) technology has revolutionized scalp reconstruction.

Surgical surface anatomy

The upper face consists of the forehead and the hairless area of the temple. The middle face includes the globe, periorbital structures, cheeks, nose and upper jaw. The lower face includes the perioral structures, chin and lower jaw.

The forehead extends from the hair margin to the eyebrow and spans the region between the scalp and upper eyelids. Metopic synostosis produces midline bossing with a ridge. Variable transverse creases on the skin may become prominent when expressing surprise or fright emotions. Contraction of underlying facial muscles produces wrinkles. The temple is demarcated superiorly by the temporal crest indicating the upper limit of temporalis, which becomes obvious when the teeth are clenched.

The external nose is a pyramidal structure located in the midline of the midface and attached to the facial skeleton; the overall shape is very variable. The upper angle or root is continuous with the forehead and the free tip forms the apex, which projects anteriorly. The lateral surfaces unite in the median plane to form the dorsum, which is narrowest at the medial canthus. The lobule is an area containing the tip of the nose. Its base contains two ellipsoidal apertures, the external nares or nostrils, which open on to its inferior surface, separated by the nasal septum and columella, which usually projects below the alar margin. The alar sulcus is a groove in the skin bounding the nasal alae above and joining the nasolabial groove (sulcus), which separates the cheek from the upper lip. Below, the alar sulcus curves towards the tip of the nose but does not reach it.

The oral aperture is formed by the upper and lower lips, joined at the oral commissure. The sharp junction between the red mucosal zone and the skin is the vermillion border ( Ch. 11 ). The midline region of the upper lip presents a shallow vertical groove, the philtrum, limited above by its attachment to the columella, and ending below in a slight tubercle limited by lateral ridges: it is formed by the decussation of the oblique fibres of orbicularis oris. The labiomental groove separates the lower lip from the chin. In older patients the marionette lines separate the oral commissure and the lateral lower lip from the mandible and chin. The chin is the protrusion in the midline of the mandible.

Clinical anatomy