Scalp

• Extent: It extends from the Supercilliary arches anteriorly to the External occipital protuerance & Superior nuchal lines posteriorly & continues inferiorly to the Zygomatic arch laterally.
• Layers of the scalp: It can be remembered by the pnemonic SCALP. The 1st three layers are tightly held together.
  • S– Skin
  • C– Connective tissue(dense):-it anchors the skin to the 3rd layer & contains vessels & nerves supplying the scalp. A laceration in the scalp causes profuse bleeding due to rich blood supply & because dense connective tissue layer does not retract & the blood vessels are held in open position.
  • A– Aponeurotic layer: contains 3 structures- anteriorly Frontalis muscle, posteriorly Occipitalis muscle & their aponeurotic tendon- Galea aponeurotica/Epicranial aponeurosis
  • L– Loose connective tissue/areolar tissue
  • P– Pericranium(periosteum)
• Blood supply of the scalp
  Arterial supply of the scalp:
  1. Supratrochlear artery- a br of Ophthalmic artery.
  2. Supraorbital artery- a br of Ophthalmic artery.
  3. Zygomaticotemporal artery- a br of Lacrimal artery.
  4. Superficial temporal artery- one of the terminal br of External carotid artery.
  5. Posterior auricular artery- a br of External carotid artery.
  6. Occipital artery- a br of External carotid artery.
  
  
  Venous drainage of the scalp: by veins with the same names as arterial supply, i.e. supratrochlear, supraorbital, zygomaticotemporal, superficial temporal, posterior auricular & occipital veins. They drain into facial, retromandibular & posterior auricular veins & eventually into External & Internal jugular veins. Intracranially, they connect to diploic veins & intracranial venous sinuses via emissary veins(valveless).
• Innervation(Nerve supply) of scalp: from cranial nerves or cervical nerves.
  1. Anterior to Ears & the Vertex of head– by the following branches of Trigeminal Nerve (CN V).
     -Supratrochlear nerve
     -Supraorbital nerve
     -Zygomaticotemporal nerve
     -Auriculotemporal nerve
  
  
  2. Posterior to Ears & the Vertex– by the following branches of cervical nerves(spinal cord level C2 & C3).
     -Great Auricular nerve (Cervical plexus, Anterior rami of C2 & C3)
     -Lesser Occipital nerve (Cervical plexus, Anterior ramus of C2)
     -Greater Occipital nerve (Posterior ramus of C2 spinal nerve)
     -Third Occipital nerve (Posterior ramus of C3 spinal nerve)
• Scalp Laceration: (also see the article Scalp Laceration)
  
  • Surgical Aspects of scalp laceration:
    -profuse bleeding mainly arterial (as in erect posture venous pressure is extremely low & due to rich blood supply & because dense connective tissue layer does not retract causing the blood vessels held in open position).
    -Lacerations deeper to aponeurotic layer gape & if primary closure is difficult to achieve due to tightly held layers, undermining of adjacent tissues may have to be done.
    – A laceration with sign of inflammation, contaminated, having foreign body or delayed for ≥24 hrs may warrant delayed primary closure 4 to 5 days after cleansing and debriding the wound.
    -Larger defect may need skin graft or local flap.
  • Options of wound closure:
    -by surgical staples– preferred if haemostasis is achieved & apposition is good & also in case of cranial surgery.
    -by modified hair apposition– used for straight, small wounds (under 10cm), if there is adequate haemostasis in the patient with hair of at least 1cm in length. It is relatively time-consuming in comparison to surgical staples, but less painful, no need of staple removal, & good cosmetic results with few complications.
    -by suturing– simple interrupted sutures, if single layered then non-absorbable(3-0 or 4-0 polypropylene or Nylon) suture;
    For deeper wound, closure in two layers preferred- 3-0 or 4-0 absorbable suture for deeper layer & 3-0 or 4-0 non-absorbable suture for superficial layer.
    Suture removal is usually done on 7-10 days, in general, the greater the tension across a wound, the longer the sutures should remain in place.
• Other conditions of Scalp:
  
  • Lump of the scalp– SEBACEOUS CYST is the commonest due to large no. of sebaceous glands in the scalp. An ulcerated lump can be a malignant lesion like Basal cell Ca & Squamous cell Ca
  • Infection of the scalp– may spread to dural sinuses via valveless emissary veins & may affect it e.g. Cavernous sinus.