ENT + Ophthalmology

Embryonic development of head + neck structures

Week 4: pharyngeal apparatus forms

6 arches + cranial nerves → separated by 4 clefts

5th regresses early

Outer ectoderm lining, mesenchyme core, inner endoderm lining

What bones arise from 1st pharyngeal arch

• maxilla

• Mandible

• Incus

• Malleus

• Temporal

• Zygomatic

Muscles arising from 1st pharyngeal arch (+innervation)

• temporalis

• Pterygoid

• Masseter

• Tensor tympani

• Mylohyoid

• Anterior belly of digastric

Innervated by trigeminal n. (V3)

Structures arising from 2nd pharyngeal arch + innervation

• Hyoid (upper portion + lesser horns)

• Stapes + stapedius

• Posterior belly of digastric

• Stylohyoid

Innervated by facial nerve

Structures arising from 3rd pharyngeal arch + innervation

• Hyoid

• Stylopharyngeus m.

Innervated by glossopharyngeal nerve (IX)

Structures arising from 4th pharyngeal arches + innervation

• levator palatini

• Pharyngeal constrictors

• Cricothyroid m.

Innervated by vagus n. (Sup. laryngeal branch)

Structures arising from 6th pharyngeal arch + innervation

Intrisinc muscles of larynx

Innervated vagus n. (Recurrent laryngeal branch)

Structures arising from 1st pharyngeal cleft + pouch

Form ear:

Cleft → external acoustic meatus + tympanic membrane

Pouch → middle ear + eustachian tube

What is first arch syndrome

Congenital disorders caused by failure of neural crest cells to migrate into first pharyngeal arch

• treacher-collins syndrome

• Pierre-robin sequence

Development of palate (week 6-12)

• intermaxillary segment → primary palate

• Maxillary prominences → 2 palatine shelves (secondary palate)

• All fuse together

Palate deformities

• cleft lip = anterior deformity

Layers of scalp superficial to deep (SCALP)

• Skin

• Connective tissue (dense) → blood vessels

• Aponeurosis

• Loose connective tissue

• Periosteum

Scalp blood supply

• Supratrochlear (ICA)

• Supraorbital (ICA)

• Superficial temporal

• Posterior auricular

• Occipital

Branches of external carotid artery

• superior thyroid

• Ascending pharyngeal

• Lingual

• Facial

• Occipital

• Posterior auricular

• Maxillary

• Superficial temporal

Venous drainage of head + neck

• superficial v. = external jugular v → subclavian v.

• Deep v. = internal jugular v → subclavian → brachiocephalic v.

Cavernous sinus contents + significance

Plexus of thin walled veins on upper surface of sphenoid sinus → superior + inferior ophthalmic veins drain inside

• ICA

• Oculomotor n.

• Trochlear n.

• Abducens n.

• Trigeminal V1+2

Thinnest part of cranium + significance

Pterion → frontal, sphenoid, parietal + temporal bones

• Likely fracture site

• Middle meningeal artery injured = extradural haematoma (compression of cerebral cortex)

Tri-lamina structure of cranium

• outer compact bone plate

• Diploe spongy bone (reduces weight)

• Inner compact bone plate

How does a newborn skull differ from an adult

• sutures not fused → gaps = anterior + posterior fontanelle (more mobile)

• Neurocranium + viscerocranium ratio 8:1 (adult 2:1)

What is shown

Orbital blow-out fracture

CT is imaging of choice → may show black eyebrow sign

Anterior fossa skull base fracture clinical presentations

• Periorbital ecchymosis

• Halo sign (in CSF)

• Partial/total loss of vision/scent

• Eye movement defects

Middle fossa skull base fracture clinical presentations

• Battle sign

• Hearing loss

• Carotid a. Damage

• Balances issues

Atypical cervical vertebrae

• C1 (atlas): no body or spinous process

• C2 (axis): odontoid process

• C7: no bifid spinous process (vertebral prominence)

Features of typical cervical vertebrae (C3-6)

• Bifid spinous process

• Triangular foramen

• Uncinate process

• Smallest vertebrae

• Transverse foramen in transverse process

Cervical vertebrae fractures

• C1 (atlas) → Jefferson’s, head first fall

• C2 (axis) → Hangman’s, neck hyperextension - more critical

Layers of fascia in neck

• skin + subcutaneous fat

• Superficial fascia → platysma m. (Involve in facial expressions innervated by CN VII)

• Deep fascia → investing, pretracheal + prevertebral

• Forms carotid sheath (common + internal carotid artery, internal jugular vein + vagus nerve)

Fascial spaces in neck + significance

• pretracheal

• Retropharyngeal (alar fascia splits true + danger space)

• Prevertebral

Deep neck space infections → can spread to mediastinum/pericardium

Superficial/regional lymph nodes

Receive lymph from scalp, face + neck

• Occipital → occipital scalp

• Mastoid → posterior neck, upper ear + lateral scalp

• Preauricular + parotid → temporal scalp + lateral face

• Submental → chin + lower lip

• Submandibular → face between eye + mouth

• Buccal → nose + cheek

• Superficial cervical → anterior neck

Deep lymph nodes

Located close to internal jugular veins under sternocleidomastoid

• prelaryngeal

• Pretracheal

• Paratracheal

• Retropharyngeal

• Jugulo-digastric/tonsillar (superior deep node)

• Jugulo-omohyoid (inferior deep node)

Name the 12 cranial nerves (PNS)

• olfactory

• Optic

• Oculomotor

• Trochlear

• Trigeminal

• Abducens

• Facial

• Vestibulocochlear

• Glossopharyngeal

• Vagus

• Accessory

• Hypoglossal

CN I: olfactory

• Function: Sensory → smell

• Arises from primary olfactory cortex

• exits through cribriform plate(ethmoid bone)

CN II: optic

• function: Sensory → vision

• Arises from retinas

• exits through optic canal

CN III: oculomotor

• function: Motor → extraorbital muscles+ eyelid elevation

• Arises from ventral midbrain

• exits superior orbital fissure

CN IV: trochlear

• function: motor → superior oblique m.

• Arises from dorsal midbrain

• Exits from Superior orbital fissure

CN V: Trigeminal

• Function: sensory + motor → splits into 3 branches at trigeminal ganglion

• Arises from Pons

• V1 opthalmic - superior orbital fissure

• V2 maxillary - foramen rotundum

• V3 mandibular - foramen ovale

CN VI: abducens

• Function: motor → lateral rectus

• Arises from Pons

• Exits superior orbital fissure

CN VII: Facial

• function: sensory + motor → facial expression, anterior 2/3 tongue, lacrimal+salivary glands, stapedius m. (ear)

• Arises from pons → internal acoustic meatus

• exit stylomastoid foramen

CN VIII: Vestibulocochlear

• Function: sensory → 2 branches

• vestubular → balance, cochlear → hearing

• arises from pons

• exits internal acoustic meatus

CN IX: Glossopharyngeal

• function: sensory + motor → posterior 1/3 tongue, pharynx + stylopharyngeus

• arises from medulla

• exits jugular foramen

CN X: Vagus

• function: sensory + motor → pharyngeal + laryngeal muscles, PANS innervation

• arises from medulla

• exits jugular foramen

CN XI: Accessory

• function: motor → trapezius + sternocleidomastoid m.

• arises from spinal cord/medulla

• exits jugular foramen

CN XII: Hypoglossal

• function: motor → innervates tongue (not palatoglossus)

• arises from medulla

• exits hypoglossal canal

Frey’s syndrome

• damaged auriculotemporal n. (branch of V3)

• during healing reinnervates sweat gland

• sweating instead of salivating + redness whilst eating

Extra-ocular muscles + functions

• superior rectus (III) → elevate, intorsion, adduct

• Medial rectus (III) → adduct

• Inferior rectus (III) → depress, extort, adduct

• Lateral rectus (VI) → abduct

• Inferior oblique (III) → extorsion, elevate, abduct

• Superior oblique (IV) → intorsion, depress, abduct

Muscles + nerves involved in opening/closing of eyes

• opening: levator palpebrae superioris → occularmotor n.

• Closing: oribicularis oculi → facial n.

• Attach to inferior + superior tarsal plates

Bell’s palsy pathology

• damage to CN VII (facial)

• Unilateral facial weakness/paralysis

• Lower motor neurone lesion

• Typically idiopathic → infection, lyme disease, pregnancy + diabetes RFx

How to differentiate between stroke + Bell’s palsy

• stroke: upper neurone lesion = able to move upper half of facial muscles (eg eyebrows)

• BP: lower motor = paralysis of all muscles

Bell’s Palsy clinical presentations (BELLs PAlsy)

• Blink reflex abnormal

• Ear sensitivity

• Loss of taste

• Lacrimation → absent/excess

• Paralysis

• Absent nasolabial fold

Horner’s syndrome

• ocularsympathetic palsy → interruption of cervicothoracic sympathetic chain (C8-T2)

• Can occur at 1st/2nd/3rd order neurone

• Presents w/ ptosis, miosis + anhydrosis

3 layers of eye wall

• fibrous: sclera + cornea

• Vascular/uvea: pupil, iris, ciliary body, choroid

• Neural: retina

Retinal neurones

• Ganglion cell

• Bipolar cell

• Photoreceptors: cones + rods

• Pigment epithelium

photoreceptors

Cones:

• concentrated in fovea

• highest visual acuity

• detect blue, red + green light

Rods:

• more numerous

• light sensitive → vision in low light

• black + white

Ocular accommodation

• reflex when focusing on a close object after looking far away

• ciliary muscle contraction = relaxation of zonular fibres

• lens becomes more curved (refractive power increases)

Mechanism of pupil constriction + dilation

Constriction/Miosis: increased light → sphincter pupillae contract

Dilation/mydriasis: decreased light → dilator pupillae contract

Parasympathetic control

Aqueous humour

• produced by ciliary body into posterior chamber → anterior

• Drained through trabecular meshwork → canal of schlemm

• Maintains intraoccular pressure, provides nutrients, removes waste

What visual field defect is shown

Total right eye visual loss

Optic nerve lesion → ipsilateral blindness

What visual field defect is shown

Bitemporal hemianopia (Central optic chiasm lesion)

What visual field defect is shown

Left nasal hemianopia (Lateral optic chiasm lesion = ipsilateral)

What visual field defect is shown

Right homonymous hemianopia (optic tract lesion = contralateral)

What visual field defect is shown

Left homonymous hemianopia w/ macular sparing (occipital cortex lesion)

What visual field defect is shown

Contralateral homonymous quadrantanopia (optic radiation lesion)

Glaucoma pathology

• Impaired aqueous humour drainage = increased anterior chamber pressure

• intraocular hypertension damages optic nerve (atrophy) = peripheral visual field loss

• loss of ganglion cells = loss of central vision

Glaucoma risk factors

• increasing age (>50)

• African ethnicity

• FHx

Glaucoma clinical presentations

Chronic → asymptomatic, visual field defects

Acute:

• Severe eye pain

• Redness + corneal oedema

• Blurred/reduced vision

• Haloes

• Fixed mid-dilated pupil

Glaucoma investigations

• intracocular pressure (tonometry)

• Humphrey perimetry (visual field testing)

• Fundoscopy → cupping (optic disk assessment)

Glaucoma management

• prostaglandin analogue

• Carbonic anhydrase inhibitor

• Laser surgery

Cataracts pathology

• clouding/opacification of lens

• Acquired or congenital

• Protein deposits on lens = reduced light transmission to retina

• Progressive decline

Cataracts risk factors

• congenital infections: TORCH

• Marfan + alport syndrome

• Prolonged glucocorticoid use

• Smoking/ excess alcohol

• Galactosaemia

• Diabetes

How does diabetes + congenital galactosaemia lead to cataracts

• excess circulating glucose/galactose

• Converted into sorbitol/galactitol + accumulates in lens

• Hypertonic environment = lens fibres swell

• Fibres rupture (Osmotic cellular injury)

Cataracts clinical presentations

• painless visual impairment (bilateral)

• Glare

• Decrease colour sensitivity

• Myopic shift

Cataracts investigations + management

• fundoscopy

• Slit lamp exam

• Surgery - lens replacement

Oculomotor (III) Palsy

• Affected eye down + out (lateral rectus + sup. Oblique functional)

• mydriasis + ptosis

• Diabetic/hypertension microvascular cause, post. Communicating a. Aneurysm, trauma + tumours

Trochlear (IV) Palsy

• superior oblique affected = hypertropia (sits higher)

• Head tilted to contralateral side

• Vertical/horizontal diplopia

• Head trauma, microvascular disease, idiopathic

Abducens (VI) Palsy

• lateral rectus affected = inability to abduct

• Horizontal diplopia

• Microvascular cause, MS, stroke, tumour

Retinal artery occlusion

• Occlusion of central retinal a. (Emergency)

• Sudden painless unilateral visual loss

• Fundoscopy: pale retina + cherry red spot

• High risk in atherosclerosis + giant cell arteritis

visual pathway

• eyes (photoreceptors → bipolar → ganglion)

• optic nerve

• optic chiasm

• lateral geniculate nucleus (thalamus)

• optic radiation

• visual cortex

myopia

• short sightedness → unable to see far away

• long eyeball or lens too convex → image in front of retina

• corrected with concave lens (neg. diopter)

hypermetropia (hyperopia)

• far sightedness → unable to see near

• short eyeball or flat lens → image formed behind retina

• corrected with convex lens (pos. diopter)

presbyopia

Age related reduction in ability to focus on close objects (failure of accommodation) → Stiff lens + reduced elasticity

Types of hearing loss

• conductive: problem w/ sound travelling from environment to inner ear

• Sensorineural: problem w/ sensory system or CN VIII so not transferred to brain

Causes of sensorineural hearing loss

• presbycusis

• Noise exposure

• Meniere’s disease

• Acoustic neuroma

• Labyrinthitis

Causes of conductive hearing loss

• ear wax/foreign body

• Infection (otitis media/externa)

• Effusion

• Perforated tympanic membrane

• Eustachian tube dysfunction

Medications associated with sensorineural hearing loss (ototoxic)

• loop diuretics

• Aminoglycoside antibiotics (gentamicin)

• Chemotherapy drugs (eg cisplatin)

Weber’s test

Tuning fork place in centre of forehead

• normal = sound equal in both ears

• Sensorineural = sound louder in normal ear

• Conductive = sound louder in affected ear

Rinne’s test

Tuning fork placed at mastoid process (bone conduction) then near ear (air conduction)

• normal/positive = air conduction > bone

• Negative = bone conduction > air, suggests conductive hearing loss

Presbycusis

• age-related hearing loss (sensorineural)

• Gradual + symmetrical → high-pitched sounds

• Loud noise exposure = key risk factor

• Causes: loss of cochlear hair cells or neurones, stria vascularis atrophy or reduced endolymphatic potential

Otitis media pathology, investigation + management

• infection + inflammation of middle ear

• Often preceded by viral upper respiratory infection (eg rhino-sinusitis)

• Otoscopy: red, bulging tympanic membrane

• Generally self limiting, analgesia + amoxicillin (pt under 2)

• Complication - otitis media w/ effusion (glue ear)

Otitis media common pathogens

• streptococcus pneumoniae

• Haemophilus influenzae

• Moraxella catarrhalis

• S. Aureus

Otitis media clinical presentations

• otalgia (ear pain)

• Fever

• Cough/sore throat

• Conductive hearing loss

• Vertigo/balance issues

Otitis externa pathology + investigation

• infection + inflammation of external ear

• Assoc w/ water submersion + cotton bud use

• Otoscopy: erythema + oedema of canal, pus/discharge

Otitis externa common pathogens

• pseudomonas aeruginosa

• Staphylococcus aureus

• Fungal → candida, aspergillus

Otitis external clinical presentations

• otalgia (ear pain)

• Conductive hearing loss

• Discharge

• Itchiness

Otitis externa management

• analgesia

• Acetic acid 2% (mild cases)

• Moderate: Topical antibiotic + steroid (neomycin, gentamicin)

Labyrinthitis Pathology

• inflammation of bony labyrinth → semicircular canals, vestibule + cochlear

• Typically due to viral upper respiratory tract infection → CMV, mumps, rubella

• Bacterial → otitis media or meningitis complication

Labyrinthitis clinical presentations

• vertigo (acute onset)

• Tinnitus

• Hearing loss

Vertigo

Sensation of surroundings spinning

• peripheral = problem w/ vestibular system

• Central = problem involves brainstem or cerebellum

Common causes of vertigo (VOMITS)

• vestibulitis → labyrinthitis or vestibular neuronitis (peripheral)

• Ototoxic drugs

• Meniere’s disease (peripheral)

• Injury to CN VIII

• Tumour (Central)

• Spin: benign paroxysmal positional vertigo (peripheral)

Vertigo investigations

• ear examination

• Cerebellar examination

• Romberg’s test

• HiNTs → head impulse, nystagmus, test of skew

Meniere’s disease pathology

• idiopathic inner-ear disorder

• Recurrent attacks of vertigo, hearing loss, tinnitus + aural fullness

• Assoc. w/ endolymphatic hydrops (high pressure disrupts sensory signals)

Meniere’s disease management

• antihistamines

• Antiemetic (Prochlorperazine)

• Refer to ENT