Head and Neck
Head and Neck · video tutorial
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Foramina of the Skull Base
| Region | Foramen | Structures passing through |
|---|---|---|
| Sphenoid bone | Optic canal | Optic nerve (CN II), ophthalmic artery, sympathetic nerves |
| Sphenoid bone | Superior orbital fissure | Lacrimal, frontal & nasociliary branches of V1; superior & inferior ophthalmic veins; CN III (sup. & inf. divisions); CN IV (trochlear); CN VI (abducens). Mnemonic: “Live Free So To See No Insane Anatomy” |
| Sphenoid bone | Foramen rotundum | CN V2 (maxillary nerve) |
| Sphenoid bone | Foramen ovale | “OVALE”: Otic ganglion, CN V3 (mandibular), Accessory meningeal artery, Lesser petrosal nerve, Emissary vein |
| Sphenoid bone | Foramen spinosum | Middle meningeal artery, meningeal branch of mandibular nerve |
| Spheno–temporal junction | Foramen lacerum | Internal carotid artery passes over (not through in life); nerve & artery of the pterygoid canal |
| Petrous temporal bone | Carotid canal | Internal carotid artery, sympathetic plexus, deep petrosal nerve, emissary veins |
| Temporal / occipital | Jugular foramen | Inferior petrosal sinus (ant.); CN IX, X, XI (intermediate); sigmoid sinus → IJV (post.) |
| Temporal bone | Internal acoustic meatus | CN VII (facial), CN VIII (vestibulocochlear), labyrinthine artery (from AICA) |
| Temporal bone | Stylomastoid foramen | CN VII (facial nerve), stylomastoid artery |
| Occipital bone | Foramen magnum | Medulla, vertebral arteries, anterior & posterior spinal arteries, spinal root of CN XI, tectorial membrane, apical ligament of dens |
What is the cranial nerve track on the clivus?
The abducens nerve (CN VI).
Which juvenile structure forms the clivus?
The spheno-occipital synchondrosis.
Congenital tumour of the clivus?
Platybasia (flattening of bone) and chordoma.
Benign tumours of the posterior cranial fossa?
Haemangioblastoma, acoustic neuroma, ependymoma, ependymoblastoma.
Skull Bones
Cranial bones (protect the brain)
- Frontal
- Parietal (left and right)
- Temporal (left and right)
- Occipital
- Sphenoid
- Ethmoid
Facial bones (form the face)
- Nasal
- Zygomatic
- Maxilla
- Mandible
- Lacrimal
- Palatine
- Inferior nasal concha
- Vomer
Surface foramina of the face
- A – supraorbital foramen/notch — supraorbital nerve, artery and vein
- B – infraorbital foramen — infraorbital nerve, artery and vein
- C – mental foramen — mental nerve, artery and vein
- These three lie in a straight line along the lateral limbus of the eye — a useful landmark for nerve blocks.
Cranial Fossae
Middle cranial fossa
| Region | Boundary |
|---|---|
| Anterior | Lesser wing of sphenoid + anterior clinoid process |
| Laterally | Squamous part of temporal bone |
| Posterior-lateral | Petrous part of temporal bone + dorsum sellae |
Key foramina: superior orbital fissure, foramen rotundum, foramen ovale, foramen spinosum. Contents: temporal lobe.
Posterior cranial fossa
Bones involved: occipital bone and the mastoid & petrous parts of the temporal bones. Key landmarks: clivus, squamous occipital bone. Contents: brainstem and cerebellum.
Which bones form the posterior cranial fossa?
The occipital bone and the temporal bone.
Cavernous Sinus & Venous Sinuses
Found in the middle cranial fossa, on either side of the sella turcica. It lies lateral to the pituitary gland and medial to the temporal lobes, and is related to the sphenoid sinus.
Structures passing through — “OTOM CAT”
- Lateral wall: Oculomotor (III), Trochlear (IV), Ophthalmic (V1), Maxillary (V2)
- Within the sinus: Internal Carotid Artery, Abducens (VI)
Receives the superior and inferior ophthalmic veins, sphenoparietal sinus and emissary veins; drains via the superior and inferior petrosal sinuses → IJV.
Signs of cavernous sinus thrombosis?
Painful swelling of the eye; 3rd, 4th, 5th and 6th cranial nerve palsies; gradual loss of vision. Infection may spread via the dangerous area of the face through the ophthalmic and facial veins.
What is the major vein draining the brain parenchyma?
The great cerebral vein (of Galen).
Dural venous sinuses
- A – superior sagittal sinus
- B – inferior sagittal sinus
- C – transverse sinus
- D – straight sinus
- E – cavernous sinus
- F – sigmoid sinus
- G – falx cerebri
- H – tentorium cerebelli
Cranial Nerves at the Base of the Skull
Oculomotor nerve (CN III)
| Feature | Details |
|---|---|
| Origin | Midbrain |
| Function | Motor to SR, IR, MR, IO and levator palpebrae superioris; parasympathetic to constrictor pupillae |
| Injury signs | Ptosis, mydriasis (fixed dilated pupil), eye 'down and out' |
Cause of a 'blown pupil'?
Head trauma → uncal herniation → compression of CN III at the tentorial notch → fixed dilated pupil.
Abducens nerve (CN VI)
Supplies lateral rectus; injury causes a medial squint. A false-localising sign in raised ICP due to its long intracranial course.
Facial Nerve
Through which foramen does the facial nerve exit the skull?
The stylomastoid foramen, after travelling through the facial canal in the petrous temporal bone.
Three key branches before it exits the skull?
Greater petrosal nerve (lacrimal gland via pterygopalatine ganglion), nerve to stapedius, and chorda tympani (taste to anterior two-thirds of tongue; secretomotor to submandibular & sublingual glands).
Five terminal branches within the parotid gland?
Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical — “Two Zebras Bit My Cat”.
UMN vs LMN facial lesion?
UMN lesion: contralateral lower-face paralysis with sparing of the upper face (bilateral corticobulbar supply). LMN lesion: ipsilateral paralysis of both upper and lower face (e.g. acoustic neuroma, Bell's palsy).
Parotid Gland
What type of secretion does the parotid produce?
Serous (watery) secretion.
Parasympathetic (secretomotor) pathway to the parotid?
Inferior salivatory nucleus → glossopharyngeal nerve (CN IX) → lesser petrosal nerve → otic ganglion → auriculotemporal nerve → parotid gland.
Which structures pass through the gland?
Facial nerve and its branches, retromandibular vein, and the external carotid artery and its branches.
What is Frey syndrome?
Damage to the parasympathetic auriculotemporal fibres causing gustatory sweating in response to salivary stimulus.
Triangles of the Neck
Posterior triangle
Boundaries: sternocleidomastoid, trapezius and the middle third of the clavicle. Contents include the spinal accessory nerve, cervical plexus branches, trunks of the brachial plexus, the external jugular vein and the third part of the subclavian artery.
Effect of spinal accessory nerve injury?
Shoulder droop and inability to shrug (trapezius) or turn the head to the contralateral side (sternomastoid).
Anterior triangle
| Subdivision | Key contents |
|---|---|
| Digastric (submandibular) | Submandibular gland & nodes, facial vessels, hypoglossal nerve |
| Muscular | Strap muscles, anterior jugular vein |
| Carotid | Carotid sheath (CCA, vagus, IJV), ansa cervicalis |
Larynx
| Muscle | Action | Nerve |
|---|---|---|
| Cricothyroid | Stretches / tenses vocal cords | External branch of superior laryngeal nerve |
| Posterior cricoarytenoid | Abducts cords (the only abductor) | Recurrent laryngeal nerve |
| Lateral cricoarytenoid | Adducts cords | Recurrent laryngeal nerve |
| Thyroarytenoid / vocalis | Relaxes / fine-tunes cords | Recurrent laryngeal nerve |
Site of a cricothyroidotomy?
The cricothyroid membrane, between the thyroid and cricoid cartilages.
Effect of recurrent laryngeal nerve injury?
Unilateral injury → hoarseness; bilateral injury → vocal cord paralysis, stridor and airway compromise.
Thyroid & Parathyroid Glands
Three parts: left and right lobes joined by an isthmus. Attached to the larynx by pretracheal fascia, so it moves on swallowing. Develops from the foramen caecum and descends — a persistent track gives a thyroglossal duct cyst (midline, moves with tongue protrusion).
| Cancer | Route of spread |
|---|---|
| Papillary | Lymphatic (only type to spread this way) |
| Follicular | Blood |
| Medullary | From parafollicular C cells |
| Anaplastic | Direct local invasion |
Vertebral level of the thyroid cartilage?
C4.
Arch of Aorta, Carotid System & Circle of Willis
Branches of the arch of the aorta: brachiocephalic trunk (→ right subclavian + right common carotid), left common carotid, left subclavian. The common carotid bifurcates at the upper border of the thyroid cartilage into internal (brain) and external (face & neck) branches.
| Structure | Type | Function |
|---|---|---|
| Carotid body | Chemoreceptor | Detects blood gas changes |
| Carotid sinus | Baroreceptor | Detects blood pressure changes |
Circle of Willis
Formed by the two internal carotid and two vertebral arteries: anterior communicating, anterior cerebral, internal carotid, posterior communicating, and posterior cerebral arteries with the termination of the basilar artery.
Signs of a middle cerebral artery (MCA) infarct?
Contralateral hemiplegia (face & arm > leg), contralateral sensory loss, homonymous hemianopia, and aphasia if in the dominant hemisphere.
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