Session 4 - Cranial nerves Flashcards
What are the two mnemoics for cranial nerves?
Oh Oh Oh To Touch And Feel Very Girly Vaginas So Heavenly
Some Say Marry Money
But My Brother Says Big Boobs Matter Most
Name the 12 cranial nerves
Olfactory - Sensory Optic - Sensory Oculomotor - Motor Trochlear - Motor Trigeminal - Both Abducent - Motor Facial - Both Vestibulocochlear - Sensory Glossopharyngeal - Both Vagus - Both Spinal accessory - Motor Hypoglossal - motor
Name and outline the sensory function of the CN I?
Olfactory nerve
Smell
What pathology can be involved with the olfactory nerve?
Fracture of the cribiform plate associated with leakage of CSF from nose (rhinorrhea) and anosmia
Name and outline the sensory function of the cranial nerve II
Optic nerve
Sight
Outline the pathology of the optic nerve
Can be damaged due to
- Direct trauma to eye, orbit or optical canal
- Pressure on optic pathway
Causes a loss of pupillary constriction and visual field defects
Name and outline the motor function of CN III
Oculomotor Innervates - Extraocular muscle - Ciliary muscles - Sphincter pupillae
Outline pathology of the oculomotor nerve
Fracture of cavernous sinus or anurysm
Causes - Dilated pupils, ptosis, eyes turned down and out, loss of pupillary reflex on affected side
Name and outline motor innervation of CN IV
Trochlear
Innervates the superior oblique of the eye
Name a pathology of the trochlear nerve
Stretching of the nerve during its course around the brainstem OR orbit fractures
Causes inability to look down when eye adducted
Name CN V and its three branches
Trigeminal nerve
Opthalmic
Maxillary
Mandibular
What does the opthalmic branch do?
Sensory for skin and cornea
How can the opthalmic branch be tested?
Corneal reflex (poking sclera)
What does the maxillary branch innervate?
Skin, mucous membrane of nose, palate and upper dental arcade
What does the mandibular branch do?
Sensory - Skin, lower teeeth, cheek and anterior 2/3rd of toung
Motor - Innervates muscles of mastication
What do lesions of trigeminal nerve lead to?
Paralysis of muscles and sharp, intense facial pain
What is CN VI? What is its motor function?
Abducens
Motor - Innervates the lateral rectus muscle
What occurs in pathology of abducens?
Fractures involving cavernous sinus or orbit
Eye fails to move laterally, diplopia on lateral gaze
What is cranial nerve VII and what are its sensory and motor functions?
Facial nerve Sensory Taste - Anterior 2/3 tongue Supplies part of external acoustic meatus and auricle Motor Muscles of facial expression Submandibular and sublingual glands Nasal mucosa, paranasal sinuses and lacrimal gland
Name three ways in which facial nerve can be injured
Laceration in parotid region
Fracture of temporal bone
Intracranial haematoma
What symptoms are there in laceration of in parotid region facial nerve damage?
Paralysis of facial muscles, eye remains open, angle of mouth droops, forehead does not wrinkle
(Bell’s palsy)
What occurs in fracture of temporal bone injury to facial nerve?
Bell’s palsy
Involvement of cochlear nerve and chroda tympani - Dry cornea, loss of taste in anterior 2/3rds of tounge
What are the symptoms of facial nerve damage due to intracranial haematoma?
Forehead wrinkles because of bilateral innervation of frontalis muscle
Paralysis of contralateral facial muscles
What is bell’s palsy?
Form of facial paralysis resulting from dysfunction of facial nerve. Most common mononeurpathy. Inflammatory condition leads to swelling of facial nerve, especially in narrow bone canal beneath ear.
Eye on affected side cannot be closed, which leads to dry cornea and there may be a loss of taste in anterior 2/3 tongue.
What three pathologies must be excluded before a diagnosis of bell’s palsy can be made?
Stroke
Lyme disease
Herpes zoster virus
How is Bell’s palsy treated?
Corticosteroids
What is CN VIII and what are its main functions?
Vestibulocochlear nerve
Vestibulo branch - controls balance
Cochlear branch - Hearing
What are some possible pathologies of the vestibulocochlear nerve and their symptoms?
o Skull fractures, ear infections, tumour of the nerve (acoustic neuroma) may all cause nerve lesions
Progressive, unilateral hearing loss, tinnitus, vertigo
Acoustic neuroma frequently impairs Facial Nerve (CN VII) too
What is CN IX and what are its sensory and motor functions?
Glossopharyngeal nerve Sensory - Taste to posterior 1/3rd of tongue General sensory widely distributed to the pharynx, oropharyngeal isthmus, dorsum of palate, auditory tube - CAROTID BODY AND SINUS
Motor
- Innervates stylopharngeus
- PAROTID
How can the glossopharngeal nerve be damaged?
Loss of taste to posterior 1/3rd tongue
What is CN X and what are its sensory and motor function?
Vagus nerve
Sensory
General Sensory lower pharynx and larynx, external auditory meatus and back of auricle
Special Sensory (taste) to epiglottis
Motor
Innervates all muscles of the pharynx, except Stylopharyngeus
Innervates muscles of airways, larynx, heart and GI tract
Innervates all of the palate muscles, except tensor veli palatine
How can pathology of vagus nerve cause hoarseness of voice?
Hoarseness of voice due to paralysis of vocal fold
o Left recurrent laryngeal nerve is lower than the right
o Bronchial or oesophageal carcinoma
o Enlarged mediastinal lymph nodes
o Stretched over an aneurysm of the aortic arch
How can mitral stenosis cause hoarseness of voice?
o Mitral stenosis Enlarged LA Pushed up left pulmonary artery, compressing the left recurrent laryngeal nerve against the aortic arch
How can a thyroidectomy cause damage to superior laryngeal nerve?
External branch lies close to superior thyroid artery and may be damaged when ligating the blood vessel
What is CN XI? What are its motor functions?
Accessory nerve
Innervates pharync, larynx and soft palate
Trapezius and SCM
What can cause lesions of accesory nerve?
Surgery or lacerations to the neck can cause parlysis of SCM and superior trapezius and shoulder drop
What is CN XII and what are its motor functions?
Innervates extrinsic and intrinsic muscles of the tounge, except for palatoglossus
How can hypoglossal nerve be damaged?
Neck lacerations and basal skull fractures
Protruded tongue will deviate towards affected side due to arrangement of muscles
What are the muscles of facial expression?
Three groups
Orbital Group
- Obicularis Oculi
- Corrugator supercilli
Nasal group
Oral Group
- Orbicularis Oris
- Buccinator
- risorius, zygomaticus major, zygomaticus minor, levator labii superioris, levator labii superioris alaeque nasi and levator anguli oris
Danger of facila nerve damage in terms of orbital group
The eye cannot shut - this can cause the cornea to dry out. This is known as exposure keratitis.
The lower eyelid droops, called ectropion. Lacrimal fluid pools in the lower eyelid, and cannot be spread across the surface of the eye. This can result in a failure to remove debris, and ulceration of the corneal surface.`
