Head

Skull

Cranial sutures & Ossification of skull

  • Ossification of skull sutures- Cranial sutures normally ossify by the age of 18-24 months after birth. Before that all fontanelles are open & a raise in intracranial pressure causes them to bulge.
  • Cranial sutures- Metopic , Sagital, Coronal, Lamdoid & Squamosal sutures; in the case of suspected non-accidental injury in children, the persistence of sutures should not be mistaken as fractures on X-ray or CT scan of skull.
  • Craniosynostosis– a condition where all the cranial sutures are fused at birth, Sagittal synostosis, the most common form leading to “boat shaped skull”
  • Pterion- the junction where these 4 bones meet together- the Frontal, the Parietal, the Temporal & the Sphenoid (Fig.)
  • Importance of Pterion– the Middle meningeal artery runs behind the Pterion & trauma at this area causes injury the artery leading to an Extradural haemorrhage.
  • Middle meningeal artery- a branch of the Maxillary artery ( one of the terminal branch of External carotid artery), enters the skull through the Foramen spinosum.
  • Basal skull fractures: when a skull fracture involves one/more of the following bones: Temporal (the most common bone involved), occipital, sphenoid or ethmoid.
  • C/F of basal skull fracture- Symptoms: CSF rhinorrhea, anosmia, bleeding from nose &/or ears, haematympanum, deafness, facial nerve palsy; Signs: Battle’s sign (mastoid ecchymosis- bruising over the mastoid process), Racoon eyes/Panda eyes (periorbital ecchymosis- bruising of the periorbital region).
  • Foramen lacerum- is present lateral to the Clivus (basilar artery lies behind the Clivus); part of the foramen is occluded by cartilage & part of it is traversed by internal carotid artery; artery & nerve of the pterygoid canal pass through the foramen lacerum.
  • Cavernous sinus: two in number, one on each side of sella turcica laterally; filled with venous blood from tributeries-— Superficial middle cerebral vein, Superior & Inferior Ophthalmic veins & Sphenoparietal sinuses; cavernous sinuses of each side are joined by inter-cavernous sinuses; & drain into the Superior & Inferior Petrosal sinuses. Contents- Internal Carotid artery with Sympathetic plexus, & VI CN;Lateral wall contains- III, IV, Va & Vb CN.

Basal Skull Fractures & Le Forte Fractures

  • Basal skull fractures: when a skull fracture involves one/more of the following bones: Temporal (the most common bone involved), occipital, sphenoid or ethmoid.
  • C/F of basal skull fracture–
    1. Symptoms: CSF rhinorrhea, anosmia, bleeding from nose &/or ears, haematympanum, deafness, facial nerve palsy;
    2. Signs: Battle’s sign (Mastoid ecchymosis– bruising over the mastoid process), Racoon eyes/Panda eyes (Periorbital ecchymosis– bruising of the periorbital region).
  • Le Forte Fractures: three types- Le Forte I, II & III.
    ~Pure Le Forte Fractures are rare, they are usually associated with other midface fractures. If a fracture is unilateral only then it is “hemi” Le Forte (not described by Rene Le Fort).
    1. Le Forte I– Horizontal maxillary fracture, the fracture line extends from the piriform aperture(anterior nasal aperture) through the lateral maxillary & lateral nasal walls crossing the zygomatico-maxillay junction to the posterior region & often includes a segment of pterygoid plates. It may be Simple(linear) or Complex(comminuted).
      —PICTURE
    2. Le Forte II– Pyramidal maxillary fracture, it extends from the pterygoid region on one side, underneath the zygomaticomaxillary buttress up over the medial portion of the infraorbital rim, behind the lacrimal bone & along the medial wall of the orbit towards the dorsum of the nose where it crosses & continues to the opposite side in the same pattern. It also involves zygoma & pterygoid plates.
      —PICTURE
    3. Le Forte III– Craniofacial dysjunction, the entire mass of facial bones is separated from the cranial base. The fracture line starts at the frontozygomatic suture along the lateral aspect of the internal orbit along the sphenozygomatic suture line to the inferior orbital fissure, extends medially across the floor of the orbit up the medial wall of the orbit towards the dorsum of the nose where it crosses & continues to the opposite side in the same pattern.
      —In other words, the fracture extends from the nasofrontal suture continuing posteriorly through medial wall of the orbit to infferior orbital floor, then to lateral orbital wall through zygomatico-frontal junction & zygomatic arch.
      —PICTURE

Danger area of face & cavernous sinus thrombosis

  • DANGEROUS AREA OF FACE (DANGER TRIANGLE OF FACE)
    —The area from the corners of the mouth to the bridge of the nose, including the nose and maxilla.
    —Importance-Facial vein communicates with the cavernous sinus through emissary vein. Due to lack of valve(s) in the veins draining the area, retrograde spread of infection can reach the cranial cavity causing Cavernous sinus thrombosis, Meningitis, Brain abscess.
  • Cavernous sinus thrombosis:
    1. Clinical features:
      —Orbital symptoms– Painful swelling of the eye (periorbital oedema), Ptosis, chemosis, proptosis, photophobia & gradual loss of vision,
      —Cranial Nerve involvement– III, IV, V1, V2 & VI cranial nerve palsies- the VI CN (Abducens nerve) is the 1st nerve to be involved as it lies in the centre of the cavernous sinus while others lie in the lateral wall.
      —The infection from the sinus of one side can spread quickly to the opposite side via intercavernous sinuses.
  • Middle cranial fossa– the temporal lobe lies in the middle cranial fossa.
  • Sella turcica– Pituitary gland lies here & is linked to Hypothalamus via…

Cranial fossae & Boundaries

  • Anterior cranial fossa:
    ~Boundaries–
    —Anterior: inner surface of frontal bone,
    —Posteromedial: anterior border of pre-chiasmatic sulcus of sphenoid(limbus) ,
    —Posterolateral: lesser wings of sphenoid ,
    —Floor: orbital part of frontal bone, ethmoid bone & anterior aspect body and lesser wings of sphenoid
    —Roof:
  • Middle cranial fossa:
    ~Boundaries–
    —Anterolateral: lesser wings of sphenoid
    —Anteromedial: chiasmatic sulcus & limbus of sphenoid
    —Posterolateral: Petrous part of temporal bone,
    —Posteromedial: dorsum sellae of sphenoid
    —Floor: body & greater wings of sphenoid, squamous & petrous parts of temporal bone.
  • Posterior cranial fossa:
    ~Boundaries–
    —Anteromedial: dorsum sellae of sphenoid, clivus
    —Anterolateral: petrous part of temporal bone,
    —Floor: mastoid part of temporal bone, squamous, condylar & basilar parts of occipital bone.
    —Roof: Tentorium cerebelli

Foramens of Cranial Fossae

  • Anterior cranial fossa:
    1. Foramen caecum– emissary vein to superior sagittal sinus.
    2. Anterior ethmoidal foramen– Anterior ethmoidal artery, vein & nerve.
    3. Foramina of Cribriform plate– Olfactory nerve (CN I)
    4. Posterior ethmoidal foramen– Posterior ethmoidal artery, vein & nerve
  • Middle cranial fossa:
    1. Optic canal– Optic Nerve (CN II) with three layers of meninges→ infection of meninges as Papilledema, Ophthalmic artery, Sympathetic Nerves
    2. Superior Orbital Fissure– Occulomotor Nerve (CN III), Trochlear Nerve (CN IV), Lacrimal, Frontal & Nasocilliary branches of Ophthalmic Nerve (CN V₁), Abducent Nerve (CN VI), Superior Ophthalmic Vein)
    3. Foramen rotundum– Maxillary Nerve (CN V₂)
    4. Foramen ovale– Mandibular Nerve (CN V₃), Accessory Meningeal artery, Lesser Petrosal Nerve
    5. Foramen spinosum– Middle meningeal artery & vein, Meningeal branch of Mandibular Nerve
    6. Foramen lacerum– in this foramen, the greater petrosal nerve joins with the deep petrosal nerve to form the nerve of the pterygoid canal which along with artery of pterygoid canal pass through it. Foramen lacerum is a portal of entry into cranium for tumours (e,g. Nasopharyngeal Ca, Juvenile angiofibroma, Adenoid cystic Ca, Malignant melanoma & Lymphoma)
    7. Carotid canal– SIDE: Sympathetic plexus around artery, ICD (Internal carotid artery with its sympathetic nerve plexus), Deep petrosal nerve, Emissary veins
  • Posterior cranial fossa:
    1. Internal acoustic meatus– Facial Nerve (CN VII), Vestibulocochlear Nerve (CN VIII), Labyrinthine artery
    2. Jugular foramen– Inferior petrosal sinus, Glossopharyngeal Nerve (CN IX), Vagus Nerve (CN X), Accessory Nerve (CN XI), Sigmoid sinus, Posterior meningeal artery
    3. Hypoglossal canal– Hypoglossal Nerve (CN XII)
    4. Foramen magnum– Medulla oblongata, Meninges, Vertebral arteries & venous plexuses, Meningeal branches of vertebral arteries, Spinal root of accessory nerve

Dural Venous Sinuses

  • Name all the venous sinuses & their course
    ~ 4 unpaired & 6 paired sinuses:
    • Unpaired–
      1. Superior sagittal sinus,
      2. Inferior sagittal sinus,
      3. Straight sinus &
      4. Occipital sinus
    • Paired–
      1. Sphenoparietal sinus,
      2. Superior Petrosal sinus,
      3. Inferior Petrosal sinus,
      4. Transverse sinus,
      5. Sigmoid sinus,
      6. Cavernous sinus.

Temporal & Infratemporal Fossae

  • TEMPORAL FOSSA:
    • Boundaries–
      1. Anterior: Frontal process of Zygomatic bone & Zygomatic process of frontal bone
      2. Posterior & Superior: Temporal lines
      3. Lateral: Temporal fascia- from Temoral lines to Zygomatic arch
      4. Inferior: Zygomatic arch & Infratemporal crest of greater wing of sphenoid
      5. Floor: Pterion

        —Pterion is the point where the four bones- Frontal, Parietal, Temporal & Sphenoid meet.
    • Contents of Temporal Fossa:
      1. the major structure is Temporalis muscle,
      2. also, the Zygomaticotemporal branch of the Maxillary nerve[V2] passes through the fossa.

  • INFRATEMPORAL FOSSA:
    • Boundaries–
      1. Medial: Lateral pterygoid plate
      2. Lateral: Mandible ramus & coronoid process
      3. Anterior: Maxilla
      4. Posterior: Tympanic plate, mastoid & styloid processes of temporal bone
    • Contents of Infratemporal Fossa:
      1. Muscles:
        • Medial pterygoid
        • Lateral pterygoid
        • Temporalis
      2. Vessels:
        • Maxillary artery
        • Pterygoid venous plexus
      3. Nerves: these nerves pass through infratemporal fossa-
        • Mandibular nerve
        • Chorda tympani
        • Otic ganglion
        • Auriculotemporal nerve
        • Inferior alveolar nerve
        • Lingual nerve

MUSCLES OF MASTICATION:

The following are muscles of mastication & are supplied by the Mandibular division of Trigeminal Nerve, V3.
Of the four muscles of mastication, Temporalis fills the temporal fossa, Medial & Lateral pterygoids are in the Infratemporal fossa & Masseter is lateral to Infratemporal fossa.

FACIAL ARTERY- COURSE & BRANCHES

  • Course: The Facial artery branches from anterior surface of the External carotid artery (Other branches of External Carotid artery: SALFOPMS -Superior Thyroid, Ascending Pharyngeal, Lingual, Facial, Occipital, Posterior Auricular, Superficial Temporal & Maxillary arteries) in the Carotid triangle, passes obliquely beneath the digastric & stylohyoid muscles, appears at lower border of mandible after passing posterior to submandibular gland. It curves upwards over the body of mandible anterior to Masseter (where its pulse can be felt) & enters the face. From here it runs upwards & medially to reach the angle of mouth, passes along the side of nose & terminates as angular artery at the medial corner of eye.
  • Branches:
    • In the Neck–
      1. Ascending palatine artery
      2. Tonsillar artery
      3. Submental artery
      4. Br to submandibular gland
    • Facial branches–
      1. Superior labial artery
      2. Inferior labial artery
      3. Lateral nasal artery
      4. Angular artery

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:Supratrochlear artery- a br of Ophthalmic artery.
      1. Supraorbital artery- a br of Ophthalmic artery.
      2. Zygomaticotemporal artery- a br of Lacrimal artery.
      3. Superficial temporal artery- one of the terminal br of External carotid artery.
      4. Posterior auricular artery- a br of External carotid artery.
      5. 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.
    • Anterior to Ears & the Vertex of head– by the following branches of Trigeminal Nerve (CN V).
      1. Supratrochlear nerve
      2. Supraorbital nerve
      3. Zygomaticotemporal nerve
      4. Auriculotemporal nerve
    • Posterior to Ears & the Vertex– by the following branches of cervical nerves (spinal cord level C2 & C3).
      1. Great Auricular nerve (Cervical plexus, Anterior rami of C2 & C3)
      2. Lesser Occipital nerve (Cervical plexus, Anterior ramus of C2)
      3. Greater Occipital nerve (Posterior ramus of C2 spinal nerve)
      4. 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.