Session 3 - Cranial Nerves Flashcards
(43 cards)
How are the connective tissue bindings in the CNS and PNS different?
In CNS layers are: endoneurium, perineurium, and epineurium
In PNS layers are, pia mater, arachnoid mater and dura mater.
What is a cranial nerve?
A nerve bundle that issues direct from the brain and supply or innervate tissues of the head and neck region. (They also supply some viscera outside of Head and neck region)
Cranial nerves are numbered I to XII what relevance does this have?
CN I is most rostral (anterior/superior) CN XI is most caudal. CNXII is the exception and is just in front of CNXII
Name the cranial nerves:
I - olfactory nerve II - optic nerve III - oculomotor nerve IV - Trochlear nerve V - trigeminal nerve VI - Abducens nerve VII - facial nerve VIII - Vestibulocochlear nerve IX - glossopharyngeal X - vagus nerve XI - accessory nerve XII - hypoglossal nerve
Describe CN I
Olfactory nerve - supplies sense of smell
Is not a true cranial nerve - more of a brain tract
Exits the cranium via the cribiform plate (susceptible to damage here) and then forms the olfactory bulb.
Left and right nasal cavities are supplied by separate left and righ olfactory nerves.
Loss of smell is called anosmia
What are some causes of anosmia?
Upper respiratory tract infections
Fracture of cribiform plate
Describe CN II
Optic nerve - is a sensory nerve
Actually a brain tract.
Central retinal artery and vein pass through the nerve.
Describe CNIII
Oculomotor nerve
Mixed nerve - motor and autonomic fibres
Supplies all extraocular muscles except superior oblique and lateral rectus so supplies: superior, inferior and medial rectus and inferior oblique. It also supplies levator palpaebrae superioris.
Autonomic - parasympathetic - controls constrictor pupillae
Pre-ganglionic parasympathetic fibres - ciliary ganglion - post ganglionic neurones (short- ciliary nerves) - to ciliary and sphincter pupillae muscles causing constriction of pupil and curvature of lens (accomodation)
Describe the clinical features of a complete CNIII palsy.
At rest the eye assumes a down and out position.
Complete ptosis of the upper eyelid (denervation of the levator palpaebrae superioris muscle)
Pupil is fixed and dilated
Describe CN IV
Trochlear nerve
Supplies superior oblique only
Describe the clinical features seen if there was CNIV damage.
Patient would get diplopia when looking Medially and downwards e.g. When going downstairs.
To test ask patient to look Medially and downwards. Able to look Medially (medial rectus) but not downwards.
Describe CNVI
Abducens nerve
Supplies lateral rectus
Has a long intercranial course and runs through the cavernous sinus so is susceptible to damage if there is increased inter cranial pressure.
What clinical signs are seen in CNVI damage?
Patient is unable to look laterally
Squint on looking outwards.
Describe CNV
Trigeminal nerve
Has motor and sensory functions.
Splits into three branches: Vi - opthalmic, Vii - maxillary, Viii - Mandibular
Vi - sensory function only - forehead, canthus of eye, bridge of nose. Sensation to cornea and conjunctiva
Vii - sensory function only cheeks also mucosa of nasal cavity, mucosal lining of paranasal sinuses, mucosal lining palate, roots of upper teeth.
Viii - sensory and motor function - rest of face including mucosa of inner cheek, anterior 2/3rds of tongue (sensation only) and roots of lower teeth. Motor function to muscles of mastication - masseter, temporalis, medial and lateral pterygoids, anterior belly of digastric.
Describe CNVII
Facial nerve
Motor, sensory and autonomic divisions
Motor - facial nerve
Sensory - Nervus intermedius
Autonomic - part of the Nervus intermedius - greater petrosal nerve is its largest branch
Motor division - muscles of facial expression and muscle to stapedius
Sensory - general sensation of the concha of auricle and behind ear.
Special sensory - taste to anterior 2/3rd of tongue (chordae tympani)
Autonomic - supplies lacrimal, submandibular, sublingual glands, also supplies glands of mucous membranes of nasopharynx, paranasal sinuses, hard and soft palate.
Describe the clinical features or CNVII damage
Loss of facial expression Loss of sphincter function Loss of naso-labial fold Hyperacusis (Forehead sparing) If damage posterior wall (chordi tympani) can have an affect on taste,salivation and lacrimation.
Describe CNVIII
Vestibulocochlear nerve
Special sense
Vestibular - balance
Cochlear - hearing
What are the two types of hearing loss? And what test can be used to differentiate between the two?
Sensori-neural - nerve damage
Conductive - blockage
Rinnes and webers test.
What are the clinical features of damage to vestibular nerve?
Loss of balance Vertigo Nausea Nystagmus Impairment of caloric response.
Describe CNIX
Glossopharyngeal nerve
Mixed sensory and motor nerve
Motor - brachiomotor - stylopharyngeus, viscera motor - parotid gland.
Sensory - viscerosensory - carotid body and sinus, pharynx and middle ear, special sensory - posterior 1/3rd of tongue.
How can you test the glossopharyngeal nerve?
Test gag reflex
Sensory limb of the reflex
As sensory supply to pharynx
Describe CNX
Vagus nerve
Mixed sensory and motor nerve
Motor - intrinsic muscles of the larynx and pharynx
Muscles of the palate
Smooth muscle - bronchi and digestive tract
Secretomotor - thoracic and abdominal viscera
Sensory - external ear, auditory canal and eardrum
Pharynx and larynx
Visceral sensation - thorax and abdomen
What are the symptoms of right recurrent laryngeal nerve damage?
Symptoms are hoarse voice, weak cough, risk or aspiration of fluids
How might damage to the left recurrent laryngeal arch occur?
Bronchial or oesophageal carcinoma
Enlarged mediastinal lymph nodes
Stretched over an aneurysm of the aortic arch.
