Chapter 12 part 2 (CNs, etc) Flashcards
CNs, palsies, eye movements, and brainstem
1) What is the brainstem?
2) What are its 3 parts?
3) What is it the base of?
4) What does it carry?
5) What does it contain?
1) A stalk like structure
2) Midbrain, pons and medulla
3) Cerebral hemispheres
4) Almost all of the information between the brain and the remainder of the body.
5) Its own nuclei
What 6 things do the brainstem nuclei control?
1) Cranial nerves
2) Level of consciousness
3) Cerebellar circuits
4) Muscle tone
5) Posture
6) Most vital functions
On the dorsal surface of the midbrain are 2 pairs of bumps, the _____________ and _______________
superior and inferior colliculi
What do the superior colliculi do?
Visual attention/orientation/discrimination/perception
What is on the ventral surface of the medulla?
The pyramids (corticospinal tracts); can be seen descending from the pontomedullary junction to the pyramidal decussation
The 4th ventricle joins the cerebral aqueduct which runs through the midbrain and drains into the subarachnoid space. The 4th ventricle ends where?
At the entry of the spinal cord
1) CNI (olfactory) connects to what?
2) Where does CN1 run through? Along what?
3) What detects olfactory stimuli? Be specific
1) To the forebrain
2) Through the olfactory tracts; along the ventral surface of the fontal lobes in the olfactory sulci
3) Special chemoreceptors on bipolar sensory neurons in the olfactory neuroepithelium in the upper nasal cavity.
1) The axons of the bipolar sensory neurons in the olfactory neuroepithelium in the upper nasal cavity travel where?
2) Where does the information travel after it leaves those axons?
1) Travel the olfactory nerves to the olfactory bulbs.
2) Travels the olfactory tracts in the olfactory sulcus and processing area (NOT through the thalamus)
Define anosmia
Loss of smell
When testing olfaction, one must test each nostril separately. Why?
Patients with unilateral deficit rarely notice [that there is a deficit] because the other nostril compensates
List some potential causes of anosmia
1) Some neurodegenerative diseases (such as Parkinson’s and Alzheimer’s)
2) Head trauma
3) Viruses (incl COVID 19)
4) Lesions
5) Intracranial tumors
6) Metastases
7) Sarcoidosis
8) Obstruction
Trace the path of CNII (optic nerves)
1) Come out of the back of the eye
2) Meet at the optic chiasm
3) Go through the optic tracts
4) Wrap around the midbrain to the LGN of the thalamus
1) Where does optic information from the thalamus come from?
2) Where does it go?
1) Nucleus in the thalamus that receives information from the retina
2) It sends its axons to the visual cortex through the optic radiations
What cranial nerve exits at the spinal cord?
CN XI (11)
What do CN III,IV, VI (oculomotor, trochlear and abducens) do?
Control the extraocular muscles
1) What does the CNIV (4) (trochlear nerve) do?
2) What is the trochlea?
1) Rotates the top of the eye medially and downward
2) Trochlea is a pulley-like structure
What does CNVI (6) (abducens) do?
Abducts the eye laterally in the horizontal direction
What does CN III (oculomotor nerve) do?
All other eye movements not done by the trochlear and abducens nerves, including pupillary control
1) What does CN V (trigeminal) mainly do? What does this include?
2) What does it also supply?
1) Supplies sensory to the face
-Nose, mouth, sinuses
-Anterior 2/3 of tongue
2) Motor to the mandible and the anterior portion of the external ear
What are the 3 branches of CNV? Where do they exit the skull?
V1-Ophthalmic
V2-Maxillary
V3-Mandibular
The branches each exit the skull in different places
1) Define Trigeminal Neuralgia (tic doulouruex) and what nerve branches are involved
2) When does it usually start and what causes episodes of it?
1) Recurrent episodes of brief pain, that last seconds to minutes in the distribution of V2/V3.
2) Usually begin after age 35, and are set off by chewing, shaving or touching a specific trigger point on the face.
1) What is a potential cause of tic douloureux (since cause is typically unknown)?
2) What two other disorders have this cause?
1) Demyelination of the nerve
2) MS and optic neuritis
What can cause CV sensory loss?
Trauma, tumors, herpes zoster, aneurysms of the internal carotid, schwannomas or meningiomas.
Do V2/V3 fibers cross over? What is the implication of that?
These fibers do not cross over, so lesions cause ipsilateral deficits
1) What does the facial nerve (CNVII) do?
2) What does a small branch of it do?
3) What is its path once it exits the brainstem?
1) Controls muscles of facial expression
2) Carries fibers for parasympathetic, visceral and somatosensory functions (tears, salivation, taste)
3) It runs through the auditory canal of the temporal bone, then takes a turn and runs in the facial canal, medial to the middle ear.
1) What are the facial nerve’s (CNVII) sensory neurons for?
2) What is its path once it exits the skull?
1) Sensation of the external ear
2) Passes through the parotid gland and splits into 5 major branches that control the facial expressions.
1) What is Bell’s Palsy?
2) What does it cause?
3) Besides its symptoms, what do neuro exam and imaging studies look like with this condition?
1) Most common facial nerve disorder; all divisions of the facial nerve are impaired
2) Unilateral facial weakness
3) The remainder of the neuro exam and any imaging studies are typically normal.
1) What is Bell’s palsy recovery like?
2) What is its cause?
3) What are its other symptoms?
1) Gradual recovery, but ~ 80% of patients fully recover in 3 weeks.
2) Unknown cause - thought to be viral or inflammatory in nature.
3) Ear pain from the somatosensory component, dry eye from decreased lacrimation.
-Can also be associated with loss of taste
What is the most common facial nerve (CNVII) disorder?
Bell’s palsy
1) What can happen after Bell’s palsy recovery?
2) Give an example.
1) Sometimes when facial nerves recover, they reach the wrong target.
2) For example, rogue parasympathetic fibers may create “crocodile tears, In which these patients lacrimate instead of salivate when they see food.
Recurrent episodes of Bell’s Palsy warrant what?
An extensive work up to rule out tumors, infiltrating diseases, Lyme’s disease sarcoid, and HIV.
1) What does Vestibulocochlear Nerve VIII do?
2) Where does it go?
1) Hearing and vestibular sensation
2) Enters internal auditory and then travels with the facial nerve in the auditory canal to the cochlea and the vestibular organs (semicircular canals, utricle and saccule.)
What are the two types of hearing loss? Define each.
1) Conductive HL: abnormalities of the external auditory canal or middle ear
2) Sensorineural HL: disorders of the cochlea or CN VIII common
What are some common causes of conductive HL ?
Cerumen in auditory canal, otitis, perforation of TM, and sclerosis of the middle ear ossicles
What are some common causes of sensorineural HL?
1) Exposure to loud sounds
2) Meningitis
3) Ototoxic drugs (like gentamicin)
4) Head trauma
5) Viral infection
6) Aging
7) Meniere’s disease
8) Acoustic neuroma
1) What most common tumor of the inner ear?
2) What is it? What CN is involved?
3) What is the average age of onset?
4) Does it cause unilateral or bilateral hearing loss?
1) Acoustic Neuroma
2) A slow growing tumor that occurs where CN VIII (8) enters the internal auditory meatus
3) 50 years old
4) Almost always unilateral.
A) What are the symptoms of acoustic neuroma?
B) What can it affect? What does this cause?
A1) Unilateral hearing loss
2) Tinnitus (ringing in the ear)
3) Unsteadiness (why?)
B) The trigeminal nerve that is nearby; causes facial pain and sensory loss
What 5 things does the glossopharyngeal nerve (CNIX) convey?
1) Parasympathetic (motor) to parotid gland
2) Sensation from ear (external auditory meatus,)
3) Pharynx and posterior 1/3 of tongue
4) Taste from posterior 1/3 of tongue
5) Chemo/baroreceptors of carotid body
Which nerve supplies anterior 2/3 of tongue?
CNV Trigeminal
1) What are the main functions of the vagus nerve (CNX)?
2) Name two of its branches and what they do
1) Swallowing and gag reflex
2) Recurrent and superior laryngeal nerves; control all laryngeal muscles and the cricothyroid
Besides its main functions, what else does the vagus nerve convey? (3 things)
1) Parasympathetics (motor) to heart, lung and GI tract to the splenic flexure
2) Sensation from the pharynx and small region near the external auditory meatus
3) Visceral sensory from chemo/baroreceptors in the aortic arch and GI tract
1) Where does the spinal accessory nerve (CN XI) arise from?
2) What is its function?
3) What would a lesion of it cause?
1) The cervical spinal cord
2) Motor innervation to sternocleidomastoid and trapezius muscles
3) Weakness of ipsilateral shoulder shrug and weakness of head turning AWAY from the lesion
1) What does the hypoglossal nerve (CNXII) provide?
2) What happens when there’s a lesion in it?
1) Motor to tongue
2) Weakness of tongue points towards the side of lesion when protruding
1) Disorders of CNs __________ are uncommon
2) Most disorders of these nerves are associated with what?
3) They can also be affected by the common offenders, which are what?
1) CNs IX-XII (9-12)
2) Central lesions
3) DM, demyelination, trauma, inflammatory, tumors.
1) What is Glossopharyngeal Neuralgia?
2) What does it cause?
1) Similar to Trigeminal Neuralgia except in CN IX (9) distribution.
2) Episodes of severe throat and ear pain
1) What an occur during surgeries of the neck?
2) What does this cause?
1) Injury to the recurrent laryngeal nerve
2) Unilateral vocal cord paralysis and hoarseness
What causes aspiration pneumonia? What is this a common cause of?
Cause by impaired swallowing, is a common cause of death in the elderly
1) What nerve is responsible for palate elevation?
2) What happens if there’s a lesion in it?
1) CNX (vagus)
2) The soft palate and uvula will deviate towards the normal side, while the soft palate on the abnormal side hangs low (stage curtain sign).
