Scalp, Brain And Cranial Nerves

Question 1

Layers of the scalp

Answer 1

SCALP

Skin
(Dense) Connective tissue
Epicranial aponeurosis
Loose connective tissues
Pericranium

Question 2

Clinical note of scalp layers

Answer 2

Between the aponeurosis and pericranium there are potential spaces for accumulation of fluid or spread of infection

Fluid/infection can spread to eyelids or root of nose due to the frontal belly of occipitofrontalis inserting into the skin and subcutaneous tissue

Scalp infections can spread to intracranial structures via emissary vein

Question 3

Cutaneous Sensory Innervation of face and scalp

Answer 3

Via trigeminal nerve (CN V1,2,3) to the anterior segment of face

EXCEPT skin of angle of mandible supplied by the cervical plexus with the great auricular nerve (C2 and C3)

Question 4

Arterial supply of face and scalp

Answer 4

Majority for ECA and some from ICA (ophthalmic artery)

ECA
- facial artery
- maxillary artery (buccal, mental, infraorbital)
- transverse of facial (branch of superficial temporal artery)

ICA
- ophthalamic artery (zygomaticofacial and zygomaticotemporal)

Question 5

Venous drainage of scalp and face

Answer 5

Facial vein drains most of the face to the IJV

Transverse facial drains some of upper face

Question 6

Danger triangle of face

Answer 6

No valves in veins so blood flows in both directions

So veins deep the danger triangle drain to cavernous sinus (which is in the cranium)

So skin infections in this part of the face may lead to intracranial infections

Question 7

Lymphatic drainage of scalp and face

Answer 7

• preauricular and parotid
  : near ear and drains eyelid lateral cheek and external nose
• submandibular
  : follows facial artery and drains the medial orbit, external nose, medial cheek and upper lip
• submental
  : at inferior chin and drains the medial lower lip and chin

Question 8

Circle of Willis

Answer 8

Circular anastomotic loop found at base of brain
Allows for equalisation of blood flow between the 2 hemispheres

Essential in case an artery becomes compromised as blood flow is maintained through collateral circulation

Question 9

Circle of Willis arteries involved

Answer 9

(Subclavian arteries) -> vertebral arteries -> join to become basillar artery -> posterior cerebral artery -> posterior communicating artery ->the internal carotid becomes the middle cerebral which join with the posterior cerebral arteries through the posterior communicating arteries -> anterior communicating artery -> anterior cerebral artery

Question 10

Cranial nerves on base of skull

Answer 10

I (Olfactory) - cribiform plate foramina

II (Optic) - optic canal

III, IV (Oculomotor, Trochlear) - superior orbital fissure

V (Trigeminal) - superior orbital fissure , foramen rotundum and foramen ovale

VI (Aducens) - superior orbital fissure

VII, VIII (Facial, Vestibulocochlear) - internal acoustic meatus

IX, X, XI (Glossopharyngeal, Vagus, Spinal accessory) - jugular foramen

XII (Hypoglossal) - Hypoglossal canal

Question 11

Cranial nerves functions

Answer 11

Olfactory - sense of smell/olfaction
Optic - sight/vision
Oculomotor - motor: eye movements
Trochlear - motor: eye movements
Trigeminal - sensation: head and cavities, motor: MoM
Abducens: motor: eye movements
Facial: motor: MofFE
Vestibulococochlear - hearing and balance
Glossopharyngeal - general sensation to poster 1/3 tongue and also oropharynx
Vagus - general sensation: pharynx and larynx, parasympathetic: heart, lungs, gi tract
Accessory - motor: SCM and trapezius
Hypoglossal - motor: tongue