Session 5 Flashcards
Describe embryo at 4 weeks
No face yet discernible
Head and neck take up almost half of body
Embryonic head is complex but follows similar segmental pattern
Each segment contains structures from various different systems
What are the bulges in embryonic neck called
Pharyngeal arches
What is on the outside and inside of a pharyngeal arch
Outside = ectoderm
Inside = endoderm
Pharyngeal arch contains
Artery- mesoderm, one of aortic arches
Cartilage bar- associated muscles, supports arch
Cranial nerve- each arch has a different nerve, motor to muscles associated with cartilage
Arch 1 features
Arch 2 features
Arch 3 features
Arch 4 + 6 features
Depression on outside is called
Depression on inside is called
What does the first cleft form
Tympanic membrane —> eternal acoustic meatus
What happens to clefts 2-6
Caudal border of second arch grows over more caudal arches and they disappear
What does the first pharyngeal pouch form
Tubotympanic recess —> Eustachian tube
Middle ear cavity
What does the second pharyngeal pouch form
Palatine tonsil
What does the third pharyngeal pouch form
Thymus and inferior parathyroid
Branchial/pharyngeal abnormalities
Cysts, sinuses and fistulas
Branchial cysts, sinuses and fistulas
Cyst = enclosed
Sinus = communicates with skin
Fistula = connects skin with pharynx
Branchial sinuses are usually found
As pits near the ear
Branchial cysts are usually found
Anterior to SCM in anterior triangle of neck
Features of fetal alcohol syndrome
Neural crest cells
Under developed jaw
Ears low set
Flat mid face
Small head
How does ear form
Innervation of the anterior 2/3 of tongue
Sensation from trigeminal
taste from facial
Innervation of posterior 1/3 of tongue
Sensation and taste from glossopharyngeal
Muscles arise from
Somites at the level of hypoglossal nerve
What separates the two parts of tongue
Sulcus terminalis
How does the thyroid gland develop
Thyroid diverticulum originates form Foramen cecum
Thyroglossal duct breaks down
Thyroid gland and cartilage is formed
Congenital problems with thyroid gland development
Failure of thyroglossal duct to break down can result in cysts and fistulae opening at foramen caecum
Ectopic thyroid gland tissue can sometimes be found anywhere along path of descent
How to detect a cyst or fistula at foramen caecum
Connected to tongue, stick tongue out = elevate the lump
Collectively, the pharyngeal arches, their grooves (clefts) and pouches are known as the
Pharyngeal apparatus
Rearrangement of developing structures explains why
Recurrent laryngeal nerve of faves becomes looped under the arch of the aorta on left side fan subclavian artery on right side
Facial skeleton arises from the
Frontonasal prominence and 1st pharyngeal arch
What does the fourth pharyngeal pouch form
Superior parathyroid and C cells of thyroid
Face develops from which 5 building blocks
Frontonasal prominence, two maxillary prominences and two mandibular prominences
First evidence of face development is the
Appearance of a depression in the ectoderm on the ventral aspect of the head- stomadaeum (site of future mouth)
Frontonasal prominence will form the
Forehead, bridge of nose, upper eyelids and centre of upper lip
Laterally paired maxillary prominences form the
Middle third of the face, upper jaw and most of lip and sides of nose
Paired mandibular prominences form
Lower third of face, including lower jaw and lip
First evidence of nose formation is appearance of
Two ectodermal thickenings - nasal placoderms
On ventrolateral aspect of Frontonasal prominence
What is a placode
Area of ectoderm that starts to thicken and differentiate itself from the surrounding tissue and give rise to sensory structures
Future ear develops from what placode
Otic
Deepening nasal pits are separated by
Oronasal membrane which disappears and the oral and nasal cavities become one continuous space
Palate development involves the
Maxillary prominences (merge in midline to form philtrum and primary palate) and medial nasal prominences
Fusion of palatal shelves form secondary palate and separates nasal cavity from oral cavity
What must happen so the palatal shelves can fuse (and nasal septum)
Tongue must drop down
Cleft lip arises from
Failure of fusion of medial nasal prominence and maxillary prominence
Cleft palate is when
Failure of fusion of medial nasal prominence and maxillary prominence
AND
Failure of palatal shelves to meet in midline
(Genetic and environmental)
Clefts of the lip and palate diagnosis
Antenatal with ultrasound, or after delivery
Difficulties with feeding or speech development, cosmetic
Clefts treatment
Surgery
Cleft lips- around 3 months (for cosmetic reasons)
Cleft palate- 9-12 months (specialist feeding techniques can be used up until this point)
From which pharyngeal arch are the maxillary and mandibular prominences formed
First arch
Major sensory branches from Va
Frontal nerve- supraorbital and supratrochlear nerve (on to forehead)
Nasociliary nerve- eye and skin over nose and tip of nose
Major sensory branches from Vb
Infra-orbital nerve (vulnerable in orbital floor fracture)
Superior alveolar nerves (supplies upper teeth and gums)
Major sensory branches from Vc
Auriculotemporal nerve (sensory to side of scalp, part of ext ear and TMJ)
Lingual nerve (general sensation from anterior 2/3 tongue)
Inferior alveolar nerve (supplies lower teeth and gums) + mental nerve (both vulnerable in mandibular fractures)
CN Va Opthalmic nerve division of trigeminal nerve key branches image
Hutchinson’s sign
vesicles on tip of nose- very concerned about eye being affected by shingles
Divisions of trigeminal nerve as seen on face
CN Vb Maxillary nerve division of trigeminal nerve key branches image
CN Vc Mandibular nerve division of trigeminal nerve key branches image
Orbital blowout fracture clinical correlation and presentation
Sensory defect on lower eyelid and part of cheek
Numb gums and upper teeth
Infraoribital nerve runs within bone forming floor of orbital
Mandibular fracture clinical relevance
Mental nerve exits mental foramen
Mental nerve enters into mandibular canal, becomes inferior alveolar nerve running within bone of mandible
Patch of sensation from lower lip and chin, gum and incisors affected
Facial nerve CN VII supplies generally
Motor, special sensory (Taste), parasympathetic
Facial nerve specific supplies
Motor (muscles of facial expression and nerve to stapedius)
Special sensory taste (anterior 2/3 tongue)
Parasympathetic to glands (lacrimal, nasal and salivary) (excluding parotid)
How to test facial nerve
Muscles of facial expression
Facial nerve lesion presentation
Unilateral facial droop +/- reporting symptoms due to absence of other facial nerve functions e.g. altered taste, dry mouth, can’t cry
On examination - whole half of affected side including forehead
Causes of facial nerve problems
Lesions in/around internal acoustic meatus & posterior cranial fossa tumours
Basal skull fracture involving Petrous bone
Middle ear disease (inflammation in facial canal, facial nerve palsy)
Parotid disease
Types of facial nerve palsy
Bell’s palsy, Ramsay-Hunt syndrome
How to diagnosis Ramsay-Hunt syndrome or not
Look for vesicles- a little bit like shingles of facial nerve
Caused by VZ
Vesicles around external ear
Facial nerve route
Extracranial branches of facial nerve
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical
Two zebras bit my cock
3 branches of facial nerve into Petrous bone
Nerve to stapedius - innervates muscle which dampens vibration of stapes
Greater Petrosal- carries parasympathetic fibres to lacrimal and nasal mucosal glands
Chorda tympani- taste from anterior 2/3 tongue, carries parasympathetic fibres to salivary glands (except parotid)
Facial droop key difference between stroke and facial nerve lesion
In stroke:
Forehead sparing- can close eye and raise eyebrows
Brain neural connections between motor cortex and facial nerve nuclei have been damaged
Not a facial nerve lesion
Forehead sparing explained
Pathology and injury involving motor pathways anywhere along path from primary motor cortex to where synapse with facial nerve motor nuclei in brainstem
Upper half of Contralateral face spared as has back up from ipsilateral cortex
Why would forehead also be affected
Pathology and injury involving facial nerve anywhere from after exit from brain stem and along its route to target tissue
Whole half of ipsilateral face affected
CN VIII Vestibulocochlear functions
Special sensory
Cochlea (organ of hearing)
Semicircular canals (organ of balance)
presentation and test for CN VIII Vestibulocochlear lesion
Present with- hearing loss, dizziness, tinnitus
Test with- gross bedside hearing test (whisper/finger rub), tuning fork test (Weber’s and Rinne’s)
Problems with CN VIII Vestibulocochlear
Vestibular shwannoma (or other posterior cranial fossa tumours)
Occlusion of labyrinthine artery (supplies the nerve)
Base of skull fracture (involving petrous bone)
Brainstem lesions (pons) rare
What is Vestibular Schwannoma (acoustic neuroma)
Benign tumour involving Schwann cells associated with vestibulocochlear
Slow growing
Usually unilateral
Vestibular Schwannoma (acoustic neuroma) signs and symptoms
Unilateral hearing loss
Tinnitus
Vertigo
Numbness, pain or weakness down one half of face
CN IX and X Glossopharyngeal and Vagus nerves route
Arise from medulla
Run through posterior cranial fossa
Exit through jugular foramen
Both carry parasympathetic fibres (to different target tissues)
Enters into carotid sheath - close relationship with internal and external carotid arteries
Glossopharyngeal nerve leaves sheat superiorly, tend to be examined together
CN IX Glossopharyngeal roles
Mainly sensory (oropharynx/tonsils/middle ear cavity)
Posterior 1/3 tongue (SS/GS)
1 swallowing muscle
Parasympathetic to parotid gland
Afferents from carotid sinus and body
CN X Vagus nerve roles
Motor and sensory
Muscles of larynx/pharynx- including soft palette
Sensory (Larynx/laryngopharynx)
Parasympathetic to many tissues
Presentation of patients with CN IX and X Glossopharyngeal and Vagus nerves problems
Difficulty with swallowing (CN X mainly)
Weak cough (CN X)
Difficulties with speech or changes in voice (CN X)
Assessment of patients with problems with CN X and CN IX
Speech, swallow and cough assessed
Soft palate movement (ahhh = elevation) and uvula position (CNX) assessed
Gag reflex (IX afferent, X efferent)
Problems with CN IX and X Glossopharyngeal and Vagus nerves
RLN branch of CN X (thyroid pathology or surgery, superior thorax/mediastinal pathology)
Pathology or surgery involving carotid sheath structures (e.g. common or internal carotid artery dissection, carotid endartectomy)
Posterior cranial fossa tumours , base of skull fractures (jugular foramen)
Brainstem (medullary) lesions e.g. infarct, MND
Key branches of vagus in neck
Right recurrent laryngeal nerve
Left recurrent laryngeal nerve
CN XI and XIII Accessory and Hypoglossal pathway
Arise from medulla (accessory nerve also has some contribution from upper cervical spinal nerves)
Runs through posterior cranial fossa
enter into carotid sheath (both leave superiorly in sheath)
- hypoglossal exits and travels towards tongue
- accessory exits and heads towards posterior triangle
CN XII Hypoglossal functions
Motor, target tissues = muscles of tongue
CN XII Hypoglossal examination and causes for problems
Examine tongue movements and protrusion
Surgery/pathology in proximity to or involving contents of upper carotid health, internal and external carotid arteries e.g. carotid endartectomy
Posterior cranial fossa tumours
Brainstem (medullary) lesions involving the hypoglossal nucleus e.g. brainstem infarct, MS
Can be affected in motor neurone disease
Problem with CN XII Hypoglossal
Tongue deviates towards the weakest side
CN XI Spinal Accessory pathway and action (and test)
Medulla (cranial roots) and spinal roots
Emerges deep to posterior border of SCM to enter posterior triangle, runs superficially in posterior triangle to reach trapezius
SCM (turn head) and Trapezius (shrug shoulders)
Causes shoulder drop
CN XI Spinal Accessory nerve problems
Injury, surgery or pathology involving posterior triangle or structures within
Posterior cranial fossa tumours
Base of skull fractures (jugular foramen)
Brainstem (medullary) lesions e.g. infarct
