The Cranial Nerves Flashcards
What is cranial nerve 8?
Vestibulocochlear nerve
Which number is the abducens nerve?
CN VI
What number is the trochlear nerve?
CN IV
Name cranial nerve IX
Glossopharyngeal nerve
What is CN I?
Olfactory nerve
What is cranial nerve XI?
Accessory spinal nerve
Name cranial nerve XII?
Hypoglossal nerve
Which cranial nerves have autonomic components?
III, VII, IX and X
What is the function of CN I and how is this tested?
When might this function be inhibited?
Smell - use smelling salts one nostril at a time
Anosmia - temporary with URTI, permanent in Cribriform plate fracture
Describe the course of the olfactory nerve
Nasal mucosa –> Cribriform plate –> olfactory bulb in anterior cranial fossa
How would you test the optic nerve?
Visual acuity Colour vision Visual fields Pupillary reflexes Fundoscopy
Describe the course of CN II
Retina –> optic canal –> optic tract –> primary visual cortex in occipital lobe
What are the functions of the oculomotor nerve?
- motor to extra ocular muscles except LR and SO - moves eyeball
- motor to LPS - opens eyelid
- parasympathetic constricts pupil via sphincter pupillae
Describe the course of the oculomotor nerve
Motor begins in oculomotor nucleus of midbrain, parasympathetic begins in Edinger-Westphal nucleus.
Passes through cavernous sinus and superior orbital fissure.
List the 3 major causes for oculomotor palsy?
- increases intracranial pressure
- aneurysm of the posterior cerebral artery
- cavernous sinus infection
What are the 3 signs of oculomotor palsy, assuming damage is proximal to the ciliary ganglion?
Down and out pupil
Ptosis
Blown pupil
What is the function of CN IV?
Motor to superior oblique muscle so allows eye to move down and in
Describe the course of CN IV
Trochlear nucleus in midbrain –> cavernous sinus –> superior orbital fissure
What signs would you find on examination if there was CN IV palsy?
Diplopia when looking down and in
Possible head tilt and neck stiffness
What single problem could cause palsy of CNs III, IV and VI?
Cavernous sinus infection
Give a brief overview of the course of CNV
Begins in pons - 1 sensory root and 1 motor root
In middle cranial fossa, sensory root forms trigeminal ganglion - V1 - superior orbital fissure
V2 - foramen rotundum
V3 - foramen ovale
List the functions of the trigeminal nerve
Sensory to the face
Muscles of mastication
Which nerve produces the corneal reflex?
V1
What is the course of the abducens nerve?
Abducens nucleus in pons –> cavernous sinus –> superior orbital fissure
What sign would indicate palsy of the 6th cranial nerve?
Inability to abduct the eye
Describe the course of the facial nerve
Arises in the pons
Through IAM into facial canal
In facial canal, forms geniculate ganglion and gives off greater petrosal nerve, nerve to stapedius and chords tympani
Exits facial canal and cranium via style mastoid foramen
Runs to anterior to pinna - gives off posterior auricular and motor fibres to digastric and Stylohyoid
Continues to parotid - splits into 5 terminal branches
List the functions of the facial nerve
Taste
Muscles of facial expression
Lacrimation
Salivation
What is the most likely cause of facial nerve palsy?
Middle ear pathology
Which foramen does CN VIII pass through?
IAM
When you think about this, it makes complete sense seeing as it supplies the ear
What are the functions of the Glossopharyngeal nerve?
Sensory to oropharynx, posterior tongue, carotid and parotid
Motor to stylopharyngeus
Parasympathetic to parotid
What is the course of cranial nerves IX and X?
Originate in the medulla oblongata and pass through the jugular foramen
What are the functions of the vagus nerve?
Sensory to laryngopharynx and ear
Motor to laryngeal and pharyngeal muscles
Parasympathetic to heart, lungs and GI tract
Which nerves are involved in the gag reflex?
CN IX - Afferent
CN X - efferent
Where does the accessory nerve originate?
Spinal - C1 - C5
Medulla oblongata
Which foramen does the hypoglossal nerve pass through?
Hypoglossal canal
Compare and contrast deviation of the uvula and tongue?
- uvula - vagus nerve - deviates away from lesion
- tongue - hypoglossal nerve - deviates towards lesion
Why is frowning still possible in facial nerve palsy?
Frontalis muscle has bilateral innervation so it still receives innervation from the unaffected side
What is Harlequin syndrome?
- damage to autonomic fibres of CN V at level of thoracic cord
- results in lack of sweating (anhydrosis) and vasomotor dysfunction (no vasodilation) after exercise on the affected side
Which cranial nerves are located in the anterior triangle?
Of these, which are also in the carotid triangle?
What about the carotid sheath?
Anterior triangle - CNs VI, IX, X, XI and XII
Carotid triangle - CN X + XII
Carotid sheath - CN X only
Which cranial nerve(s) is/are located in the posterior triangle?
CN XI
Which cranial nerves pass through the cavernous sinus?
III, IV, V1, V2 and VI
State which CNs go through which cranial fossa
Anterior - I and II
Middle - III to VII
Posterior - VIII to XII
Which cranial nerves originate from each of the following:
Midbrain
Pons
Medulla
Midbrain - III and IV
Pons - V to VIII
Medulla - IX to XII
