Lecture 4: Cranial nerves Flashcards
Which cranial nerves attach to the midbrain?
Occulomotor nerve CN 3 Trochlear nerve (dorsal surface) CN 4
Which cranial nerves attach to the pons?
Trigeminal nerve CN 5 Abducens nerve CN 6 Facial nerve CN 7 Vestibulocochlear nerve CN 8 (The above 2 emerge from the cerebellomedullary pontine angle)
An acoustic neuroma is a tumour which may typically develop on the vestibulocochlear nerve adjacent to the brainstem, which cranial nerves are likely to be compressed as the tumour enlarges?
Vestibulocochlear
Facial
What is the method of testing the olfactory nerve?
Offer something familiar for the pt to smell and identify
What is the method of testing the optic nerve?
1) Acuity - Shellen chart
2) Colour - ishihar plates
3) Visual fields - pt identifies wiggling finger in periphery
4) Visual reflexes - pupillary constriction reflex
What is the method of testing the occulomotor nerve or the trochlear nerve?
Patient follows your finger as you draw 2 large H’s infront of them
What is the method of testing the sensory part of the trigeminal nerve?
Corneal reflex - touch cornea with cotton wool and pt closes eye
Touch face with cotton wool on forehead, cheek and lower jaw - can they feel it
What is the method of testing the motor part of the trigeminal nerve?
Ask pt to clench teeth and fell jaw muscles, ask pt to open mouth against resistance
Perform jaw jerk - put finger on chin and strike with a tendon hammer - jaw should pertrude forwards
How would you test for the abducens nerve?
Tested same as CN3 and CN4 in eye movements
How is the motor function of the facial nerve tested?
Ask pt to crease up forehead, close eyes and keep them closed against resistance, puff out cheeks and reveal teeth
How is the cochlear part of the vestibulocochlear nerve tested and is the vestibular part normally tested?
Cochlear part - Rinne test (tuning fork on mastoid process and then next to ear, which is louder? should be 2nd)
Weber test (base of tuning fork in center of forehead, is it louder in either ear? Normally its the same in both)
Vestibular part not normally tested in routine examination
How is the sensory part of the glossopharyngeal nerve tested?
Tested by gag reflex by touching the back or arches of the pharynx
Is the sensory part of the vagus nerve easily tested?
No
How would you test the other components of the vagus nerve?
Pt speaking gives good idea of the efficacy of muscles
Uvula should be observed before and after patient saying aah - check it lies centrally and doesnt deviate on movement
How would you test the accessory nerve?
Ask pt to turn head and shrug against resistance
How would you test the hypoglossal nerve?
Ask patient to stick tongue out
What would you deduce if the tongue deviated to one side during protrusion?
If the tongue deviates to either side it suggests a weakening of muscles on that side
Which cranial nerve is involved in the pupillary light reflex?
Afferent limb = optic nerve CN II
Efferent limb = occulomotor nerve CN III (sphincter pupillae)
Which cranial nerve is involved in the corneal reflex?
Afferent limb = Ophthalmic nerve CNV1
Efferent limb = Facial nerve CN VII (orbicularis oculi)
Which cranial nerve is involved in the gag reflex?
Afferent limb = Glossopharyngeal IX
Efferent limb = Vagus nerve CN X
What 6 structures can be seen on the cerebellum when viewed from the position of the pons?
1) Suprerior, middle and inferior cerebellar peduncle
2) Flocculus (2 of them)
3) Tonsil (2 of them)
4) Nodule
What are the major functions of the cerebellum?
Recieves info from the sensory systems, the spinal cord and other parts of the brain and regulates motor movements such as posture balance, coordination and speech, resulting in smooth and balanced mucular activity, also important for learning motor behaviours
What is past pointing?
Pointing finger overshoots its intended mark to the side of the cerebellar damage
What is intention tremor?
A tremor that occurs during the performance of voluntary movements
What is dysdiadochokinesis?
Inability to perform rapidly alternating movements
What is the obex?
The bottom V of the opening to the 4th ventricle
What is the ‘spidery-type’ substance which can be seen in the 4th ventricle and what is its function?
Choroid plexus - produces CSF
How does the optic nerve pass out of the skull?
Through the optic canal
Occulomotor nerve supplies all muscles that move the eye bar 2 muscles, what are these and what CN innervates them?
All except the superior oblique muscles - innervated by trochlear nerve CN4
and lateral rectus muscle - innervated by abducens nerve CN6
SO4 LR6
Does the occulomotor nerve have some parasympathetic component?
Yes
How many parts are there to the trigeminal nerve and what are they called?
V1 - Ophthalmic
V2 - Maxillary
V3 - Mandibular
What does the mandibular nerve innervate?
Muscles of mastication
General sense to anterior 2/3 of the tongue and lower jaw
What does the facial nerve innervate?
Mostly motor - muscles of facial expression
What is the parasympathetic component of the facial nerve?
Parasympathetic innervation to the salivary glands but NOT the parotid gland
Which salivary gland is not innervated by the facial nerve, which nerve innervates this salivary gland?
The parotid gland
Innervated by the glossopharyngeal nerve
What does the glossopharyngeal nerve innervate?
Mainly sensory to pharynx
Stimulates the carotid sinus
Other than its parasympathetic function, what else does the vagus nerve supply?
Muscles to the larynx, pharynx and palate
How does the spinal accessory nerve enter the cranial cavity and after doing so what does it do?
Spinal accessory originates from spine and enters the cranial cavity through the foramen magnum where it then joins with the cranial accessory to form the accessory nerve
What does the hypoglossal nerve innervate?
All muscles of the tongue except 1 which is innervated by the vagus
Which cranial nerves exit the cranial cavity through the jugular foramen?
CN 9,10,11
How many possible fibre types of cranial nerves are there?
7
What is a nucleus?
A functional group of neurons within the CNS - a collection of cell bodies
Where are cranial nerve nuclei located?
Within the tegmentum of the brainstem, found in all brainstem parts
Does the tegmentum run throughout all 3 parts of the brainstem?
Yes, forms distinctive divisions in the midbrain, pons and medulla
What are the 2 types of cranial nerve nuclei?
1) Sensory
2) Motor
What is the function of a sensory cranial nerve nucleus?
Receives info from fibres entering the brainstem in cranial nerves
Axon synapses here with a cell body of another neuron and info is sent along fibres to the appropriate higher center
What is the function of a motor cranial nerve nucleus?
Receives info from higher centre
Fibres synapse here and gives rise to motor fibres that leave the brain stem in cranial nerves
Sensory and motor nuclei are located laterally or medially?
Sensory nuclei are located laterally within the brainstem
Motor nuclei are located medially within the brainstem
Where are the cranial nerve nuclei located in relation to the ventricular system?
Anteriorly - within the tegmentum
Why does the occulomotor nerve have 2 nuclei within the brainstem and what are they called?
Because it carries 2 types of fibres, somatic motor fibres and visceral motor (autonomic) fibres.
For each fibre type within a cranial nerve there is a corresponding nucleus in the brainstem
1) Edinger-Westphal nucleus
2) Oculomotor nucleus
What structures are innervated by the somatic and visceral motor fibres of the occulomotor nerve?
Somatic motor - Extraocular muscles Visceral motor (autonomic) - Sphincter pupillae and ciliary muscles
The 4 autonomic ganglia of the head and neck are associated with which cranial nerve?
Associated with the trigeminal nerve
What are the names of the 4 autonomic ganglia of the head and neck?
1) Ciliary ganglion
2) Submandibular ganglion
3) Pterygopalatine ganglion
4) Otic ganglion
Autonomic fibres carried in which cranial nerve synapse at the ciliary autonomic ganglion, what nerve are the post synaptic fibres carried in and what is their target?
Pre synaptic fibres - CN III
Post synaptic fibres - CN V1
Target - Sphincter pupillae (eye)
The pre synaptic and post synaptic fibres of the pterygopalatine ganglion are carried in what nerves and what is the target?
Pre synaptic - CN VII
Post synaptic - CN V2
Target - Lacrimal gland
The pre synaptic and post synaptic fibres of the submandibular ganglion are carried in what nerves and have what target?
Pre synaptic - CN VII
Post synaptic - CN V3
Target - Submandibular and sublingual gland
The pre synaptic and post synaptic fibres of the Otic ganglion are carried in what nerves and have what target?
Pre synaptic - CN IX
Post synaptic - CN V3
Target - Parotid gland
What are the 3 autonomic functions of the head and neck?
1) Sphincter pupillae of the eye
2) Salivary glands - (submandibular, sublingual, parotid)
3) Lacrimal gland
What are the 4 cranial nerves containing autonomic fibres?
1) Oculomotor
2) Facial
3) Glossopharyngeal
4) Vagus
How do the autonomic fibres of the cranial nerves pass to their target organ?
The synapse at autonomic ganglion in the trigeminal nerves and piggy back on the trigeminal nerves to reach their target organ
