Scalp Anatomy and Clinical Relevance

Scalp Anatomy and Clinical Relevance

• The SCALP consists of 5 tissue layers: Skin, Connective tissue, Aponeurosis, Loose areolar layer, and Pericranium

Skin

• It is a thick type of skin with numerous sebaceous glands
• Sebaceous cysts can occur

Connective Tissue Layer

• Has a rich vascular supply
• Fibrous tissue is attached to vessel wall and can prevent vasospasm during an injury, but can cause profuse bleeding
• Firm pressure is needed to control bleeding

Aponeurosis (Galea Aponeurotica)

• It is attached to occipitalis & Frontalis
• Transverse deep wounds gape; the galea must be repaired

Loose Areolar Tissue

• This space continues into the eyelid
• Collection of blood (Subgaleal haematoma) in this space tracks down to the eyelid
• Black eye is associated with this collection of blood
• Infections can spread into the cranial cavity via emissary V (no valves)
• This is also the plain of removing scalp during neuro-surgeries

Pericranium

• Extends through the sutures and is continuous with the endocranium (Endosteal dura)
• Large bleeds deep to the pericranium take the shape of bone; this includes Cephalohaematoma

Suturing Scalp Lacerations

• Important to control bleeding, as it can be life-threatening
• Inspect deep tissue injuries under good light, paying attention to muscles, galea, and bone
• Skin can be repaired with staples or Sutures with hair apposition!
• If the galea or muscles are damaged, it must be repaired
  • Provides good apposition of the skin
  • Controls bleeding
  • Minimizes the spread of infections around entire scalp

Arteries & Veins of the SCALP

• The Arteries include Internal Carotid, Supratrochlear, Supraorbital, Superficial temporal, Occipital, and Posterior Auricular
• The veins include External Carotid

Bones of the Skull

• The Cranial bones total 8 including Frontal, Parietal (2), Temporal (2), and Occipital, Ethmoid (2), and Sphenoid (keystone)
• The Facial bones total 14 including Mandible, Maxilla (2), Zygomatic (2), Nasal (2), and Lacrimal (2), Palatine (2), Vomer, and Inferior Nasal Conchae (2)

Skull Views

• The Coronal suture, Sagittal suture, Lambdoid suture, Frontal bone, Bregma, Parietal bone, Occipital bone, and Lambda can been seen in the superior and posterior view
• Frontal bone, Parietal boΠΕ, asterion, Mastoid process, Temporalis, and Zygomatic bone can be seen from the Lateral View

Pterion and Middle Meningeal Vessels

• A region is where Frontal, Parietal, Temporal, and Sphenoid bones join
• The skull around this region is relatively thinner and weaker
• It is common site of cranial fractures
• Middle meningeal vessels run inside the cranial cavity along the groves on the inner table of the skull (In Extra dural space) in relation to the region.
• Fractures there can cause extra dural hematoma

Clinical Anatomy of Cranial Fractures

• The vault is composed of lamina externa (outer table - thicker), lamina interna (Inner table – thinner), and cancellous bone - Diploë
• The Diploë is almost absent in area covered by the temporalis muscle; the vault is thinner and prone to fracture there
• Thickest areas include mastoid process, glabella, and external occipital protuberance
• Common fracture areas include in the vault (Frontal, temporal & parietal) and in the base (Anterior cranial fossa)

Skull Fractures

• Associated with about 20% of head injuries
• Falls, Assaults, and MVA are the most common modes of injury
• Classifications
  • Location: Vault of skull or Base of skull
  • Number of fracture lines/fragments: Linear or Comminuted
  • Displacement: Depressed or Non-displaced
  • Continuity to exterior: Simple (Closed) or Compound (Open)
• A fracture can be described using all these classifications

Linear Fracture

• Commonest type
• Usually due to blunt trauma with the impact over a relatively wide surface area of skull Significant if the fracture runs through a vascular channel
• Can occur in relation to the Vault of the skull, Base of skull - Basilar, Sutures - Diastatic
• Diastatic usually occurs in infants and young children before complete fusion of sutures
• May be associated with a linear fracture meeting a suture line

Depressed Fracture

• Is Due to blunt trauma with the impact over a smaller surface area
• Commonly involves the cranial vault
• There is an increased risk of causing damage to the brain tissue; Brain contusions/Laceration
• There is also an increased risk of Seizures/neurological deficits; this needs elevation surgically
• Can be associated with comminution because comminution is caused by blunt trauma with the impact over a smaller surface area

Fractures vs. Sutures

Fractures

• Are greater than 3 mm in width, widest at the center and narrow at the ends
• They usually appear darker and are usually over the temporoparietal area
• They runs in a straight line

Sutures

• Are less than 2 mm in width, same width throughout
• They are lighter on x-rays compared with fracture lines
• They are at specific anatomic sites and do not run in a straight line

Simple (Closed) vs Compound (Open) Cranial Fractures

Simple Cranial fracture

• Is when The fracture is not exposed to the exterior

Compound Cranial factures

• The fracture is exposed to the exterior
• This has Risk of infection+
• Although rare, compound cranial fractures may occur with intact scalp/skin
• Includes fractures that can also involve:
  • Air sinuses
  • Petrous bone and middle ear
    • Raises theCaries risk of IC infections if there is associated damage to meninges

Determining if Fractures are Compound

• Pneumocephalus, Subcutaneous emphysema, Air sinuses, Petrous bone and middle ear can cause a compound fracture
• The presence of gas in the cranial cavity or foreign body is indicative
• Fracture causing CSF rhinorrhoea/otorrhoea is the best indicator of a compound cranial fracture

Bones of the skull base

• DO NOT include the Maxillary

Basilar Skull Factures - Signs and symptoms

• Are commonly linear fractures extending from facial or skull vault fractures
• Signs and symptoms are due to, brain and cranial nerve damage and Sinus/Petrous temporal fractures

Leakage of CSF

• CSF rhinorrhoea & CSF otorrhoea
• It will have a double ring sign (Sensitive sign)
• It will be Positive for Beta 2 Transferrin
• Leakage of blood with Menageal with Menigeal damage showing
  • Epistaxis
  • Haemotympanum (Intact Tympanic membrane) or Blood otorrhoea
• Fluid levels in sinuses and Pneumocephalus

Vascular Damage & Bleeding

• IC Haematomas mass effect, can also have fluid leak into and accumulate in the form of
  • Haematoma behind the ears – Battle's sign
    • Haematoma around the eyes – Racoon eyes
  • Subconjunctival bleeding & Exophthalmos

Anterior cranial fossa fractures

• 70% of basillar & more vulnerable! , due to direct blow to the front of the skull which is commonly associated with orbital
• Structures related – frontal lobes, eyes, nose

Fractures with Eye Related Signs

• Bleeding into orbital cavity structures → exophthalmos & bleeding around the eyes (Periorbital bleeding /Racoon eyes)
• Bleeding into subconjunctival space → subconjunctival haemorrhage
• Damage to optic canal/nerve → Blindness & Damage to eye muscles/nerves → ocular palsies, numbness of the forehead

Nose related signs

• Damage to frontal/Ethmoid sinuses (cribriform plate)→ CSF rhinorrhoea (CSF fistula)/ Epistaxis/Meningitis risk
• Damage to cribriform plate + Olfactory nerves/bulb → Anosmia

Middle cranial fossa fractures (20-25%)

• It is weakest area of the base of the skull due to Multiple foramina, hence linear vault fractures can extend along these lines of least resistance

Fracture signs & Symptons

• Damage to the sphenoid sinus + meninges causes CSF rhinorrhoea
• Petrous bone fractures
• Haemotympanum/Blood or CSF otorrhoea & Epistaxis
• Blood can accumulate behind the ears which can cause Battle's sign
• CN III to VIII can be potentially be affected; Superior Orbital fissure # (CN III, IV, VI) causes Diplopia/Pupillary dilatation
• Foramen ovale causes Mandibular nerve involvement or Numbness over lower face/weakness of masticatory muscles Petrous bone fractures will damage the and give Deafness, tinnitus, vertigo

Posterior Cranial Fossa Fractures

• Rare (5% of basilar fractures) but often rapidly fatal (Smaller compartment + Presence of vital centres)
• Significant hemorrhaging Presence of Venous sinuses around region that can cause:
  • Blood can accumulate behind the ears →Battle's sign
  • CN VII-CNXII which can cause Dysphagia and loss of gag reflex and Cerebellar signs

Signs & Symptoms of Cranial Fracture

• soft-tissue swelling (“Boggy mass”), “Step-off” / Palpable discrepancy in bone contour, crepitus (bone crackle), lacerations, & tenderness occur
• Also Headache, Nausea, and focal signs of skull fracture like altered consciousness
• A Thin slice CT (Bone window) is used to get images/ evaluate fractures
• 3D reconstructions can be useful to evaluate complex fractures with the presence of injuries
• For isolated skull fractures, treatment is Primarily conservative unless
• If surgical intervention is determined, neurological deficits, CSF fluids will be addressed

Example of clinical

• Patient admitted with scalp contusion (temporo-parietal region)
• He had CSF rhinorrhea, and numbness of the skin over the jaw, -CN V3 & impaired tongue sensation left c- CN's V3 VII
• A CSF leak and Fracture of TMJ is suspected

Mid Facial Fractures - Lefort Classification

• Is an Anatomically complex region with multiple bones/articulations which is commonly damaged from blunt trauma with MVA/assaults/sport injuries
• It can be associated with intracranial/ophthalmological injuries; management is often delayed since Associated airway & brain injuries

Classifications:

• Lefort I - Hard palate is separated from the maxilla
• Lefort II - Maxilla is separated from rest of the face
• Lefort III - has Craniofacial dysjunction
• These # can be linked with intracranial and ophthalmological injuries
• Lefort II # often damages the infraorbital nerve

Facial Fractures

• Will depend on severity, nature, of injury includes:

  • Individual bone & multiple
    • Includes:
      • Common bones (mandible/ zygomatic/ orbital fractures)

• Orbital Fractures*

• Relations of the orbit from Superior to Medial, include

  • Superior which has an anterior cranial fossa
  • Medial with Ethmoid & Sphenoid sinuses

• Medial and Inferior are weaker Orbital Fractures

• Direct Blow rim fractures can cause blow out fractures

• Presentation*

• Bruising, Crepitus

• In the presence of Intraorbital bleeding, it can be exophthalmos

• Nerve damage/Muscle can cause anesthesia of the affected cheek and upper teeth / gums, Gaze abnormalities, vision impairment

Middle Cranial Fossa Fractures: Are unlikely to be associate with flaccid paralysis of ipsilateral tongue muscles

Intracranial Injuries:

Brain with Intercranial Haemorrhage - 2 primary mechanisms for Brain Injuries - Due to bone and Damage Caused by the movement of the brain within the intra- cranium

Primary Vs secondary Brain Juries

• Primary injuries ( lacerations, contusions with diffuse axonal injury) with acute percussion
• There are 2 primary Mechanisms involving:

Direct Damage

 - Depressed Fracture causes injury to site
 -  skull invaginate to pressure points of the brain leading ( contrecoup injury or coup)

• Brain bounces from site with Coup to contrecoup damage which will happen in secondary

- Rotational injury

• High to low - Then to from RAS against hemispheres with axonal shearing injury or DAI ( diffuse Axonal Shear with DAI)

Diffuse Axonal Injury

DAI is the most common traumatic brain injury with subcatrical locations (white matter corpus callosum)