Chapter 5: The Brain Stem (continued) Flashcards
Describe the course the accessory nucleus takes.
accessory nucleus is found in the cervical spinal cord.
- axons of the spinal accessory nerve arise from the accessory nucleus, pass through the foramen magnum to enter the cranial cavity, and join the fibers of the vagus to exit the cranial cavity through the jugular foramen
What does the curve of the facial nucleus form?
the internal genu of the facial nerve
What is the purpose of the superior olivary nucleus?
recieves auditory impulses from both ears by way of the cochlear nuclei
Where is the main sensory nucleus of pons located?
just lateral to the motor nucleus of pons where trigeminal motor neurons are transmitted
What is the purpose of the main sensory nuceus of the pons?
receives tactile and pressure sensation from the face, scalp, oral cavity, nasal cavity and dura
What is the spinal trigeminal nucleus?
a caudal continuation of the main sensory nucleus
Where does the spinal trigeminal nucleus extend?
from the mid pons through the medulla to the cervical cord
What is the purpose of the spinal trigeminal nucleus?
central processes from cells in the trigeminal ganglion conveying pain and temperature sensation from the face descend in the spinal tract of V and synapse on cells in the spinal nucleus
What part of the thalamus relays touch, pain, temperature (CN V) and taste (CN VII, IX) sensations from the face to cortex?
VPM
Where is the mesencephalic nucleus located?
at the point of entry of the fifth nerve and extends into the midbrain
Purpose of the mesencephalic nucleus?
recieves proprioceptive input from joints, muscles of mastication, extraocular muscles, teeth, and the periodontium
Label figure III.5.5 include note at bottom
What is another name for corticobulbar innervation of cranial nerve nuclei?
Corticonuclear innervation of CN nuclei
What is the purpose of corticobulbar fibers?
serve as the source of upper motoneuron innervation of the LMN in CN nuclei
Corticobulbar innervation of facial motoneruons to muscles of the upper face is contralateral or bilateral?
bilateral
UMN of corticobulbar fibers that innervate the upper face are responsible for what action of the face?
wrinkling of the forehead and shutting the eye
Corticobulbar tract innervation to the lower part of the face is bilateral or contralateral?
contralateral
Cortiocbulbar innervation to the lower part of the face innervates which structure?
muscles of the mouth
Bells palsy cause and presentation?
facial nerve lesion
complete ipsilateral paralysis of muscles of facial expression, including an inability to wrinkle the forehead or shut the eyes and a drooping of the corner of the mouth
Presentation of a lesion of corticobulbar nerves to the tongue muscles?
lesion of the left will cause deviation of tongue to the right
Label the structures of the inner ear.
What does the spiral ganglion contain?
contains cell bodies whose peripheral axons innervate auditory hair cells of the organ of Corti
Why do middle ear diseases result in conductive hearing loss?
because of a reduction in amplification provided by the ossicles
What are some middle ear disease?
otitis media, otosclerosis
What lesions may result in hyperacusis?
leisons of the facial nerve in the brain stem or temporal bone (Bell palsy)
Hyperacusis.
an increased sensitivity to loud sounds
Presbycusis results from what event occurring?
loss of hair cells at the base of the cochlea
If air conduction > bone conduction an indication of sensorineural hearing loss or conductive?
sensorineural hearing loss
If bone conduction is greater that air conduction this is a type of sensorineural or conductive hearing loss?
conductive hearing loss
Describe the path of the auditory system from cells of the cochlear nuclei to the cerebral cortex.
Axons go from ventral cochlear nuclei and bilaterally innervate the superior olivary nuclei
reach lateral lemniscus which carries auditory input from the cochlear nuclei and the superior olivary nuclei to the inferior colliculus in midbrain
Inferior colliculus carries auditory information to MGB (medial geniculate body) of the thalamus,
auditory radiation projects to the primary auditory cortex located on posterior portion of the transverse temporal gyrus (Heschl’s gyrus; Brodmann areas 41 and 42)
If a patient presents with a significant hearing loss in one ear, the lesion is most likely where?
in middle ear, inner ear, eighth nerve, or cochlear nuclei
What is conductive hearing loss caused by?
passage of sound waves through external or middle ear is interrupted. Causes: obstruction, otosclerosis, otitis media
Sensorineural hearing loss cause?
damage to cochlea, CN VIII or central auditory connection
Weber test
place tuning fork on vertex of skull
if unilateral conductive loss > vibration is louder in affected ear;
if unilateral sensorineural loss > vibration is louder in normal ear
Rinne test
place tuning fork on mastoid process (bone connduction) until vibration is not heard, then place fork in front of ear (air conduction).
If unilateral conductive loss > no air condution after bone conduction is gone;
if unilateral sensorineural loss> air conduction present after bone conduction gone
Secondary vestibular fibers, originating in the vestibular nuclei, join the MLF and supply which nuclei?
motor nuclei of CN III, IV, and VI
What is the function of the vestibular component of the vestibulocochlear nerve?
- equilibrium
- posture
- VOR (vestibulo-ocular reflex)
What do the 3 semicircular canals of the ear respond to?
angular acceleration and deceleration of the head
What senses do the utricle and saccule respond to?
linear acceleration and the pull of gravity
What lobe of the cerebellum do the vestibular nuclei send information to?
flocculonodular lobe of the cerebellum
Describe what is happening in this figure. (Lesion of left vestibular nuclei or nerve)
a lesion of the vestibular nuclei or nerve (in this example, on the left) produces a vestibular nystagmus with a slow deviation of the eyes toward the lesion and a fast correction back to the right and head will rotate to the right
Pneumonic to remember actions of nystagmus with caloric testing?
COWS
cold opposite, warm same
What does cold water in a caloric test mimic?
a lesion of the vestibular system
Chronic vertigo suggests a central or peripheral lesion?
central lesions
T/F. Vertigo is usually severe in peripheral and mild brain stem disease.
true
What is Meniere disease?
characterized by abrupt, recurrent attacks of vertigo lasting minutes to hours accompanied by tinnitus or deafness and usually involving only one ear
Nausea and vomiting and a sensation of fullness or pressure in the ear are also common during an acute episode
inability to stand
What is Meniere disease caused by?
distention of the fluid spaces in the cochlear and vestibular parts of the labyrinth
Conjugate gaze.
the ability of the eyes to move together
What actions are needed for conjugate gaze?
Nuclei which nerves used for the eyes to move together ?
oculomotor nuclei and abducens nuclei are interconnected by medial longitudinal fasiculus MLF
What gaze centers control horizontal gaze?
frontal eye field (contralateral gaze), and PPRF (paramedian pontine reticular formation, ipsilateral gaze)
Describe the effect of each lesion seen in the image .
voluntary horizonatal conjugate gaze
Describe the images in the picture
also abducens nucleus is coexistent with PPRF, the center for ipsilateral horizontal gaze. Lesions result in an inability to look to the lesion side, and may include a complete ipsilateral facial paralysis because the VIIth nerve fibers loop over the CN VI nucleus
Describe what is happening in each of the responses.
image normal/abnorma rsponses to horizontal gaze part2
Label the arterial supply of the brain
What are the branches of the vertebral artery?
branches of anterior spinal artery (ASA)
posterior inferior cerebellar artery (PICA)
How is the basilar artery formed?
joining of the 2 vertebral arteries at the pontomedullary junction
What is medial medullary syndrome caused by?
occlusion of the ASA
What are symptoms along with affected parts of medial medullary syndrome?
pyramid: contralateral spastic paresis
medial lemniscus: contralateral loss of tactile, vibration, conscious proprioception
XII nucleus/fibers: ipsilateral flaccid paralysis of tongue with tongue deviation on protrusion to lesion
What is the affected artery in lateral medullary syndrome?
PICA posterior inferior cerebellar artery
What is another name for lateral medullary syndrome?
Wallenburg syndrome
What are the affected areas and presentation of symptoms of those with lateral medullary syndrome?
- inferior cerebellar peduncle: ipsilateral limb ataxia
- vestibular nuclei: vertigo, nause/vomiting, nystagmus (away from lesion)
- nucleus ambiguus (CN IX, X): ipsilateral paralysis of larynx, pharynx, palate > dysarthria, dysphagia, loss of gag reflex
- spinal V: ipsilateral pain/ temperature loss (face)
- spinothalamic tract: contralateral pain/temperature loss (body)
- descending hypothalamics: ipsilateral Horner syndrome
Medial pontine syndrome usually occurs as a result of occlusion of which arteries?
paramedian branches of the basilar artery
What are the affected areas and the characteristics of a medial pontine syndrome?
corticospinal tract: contralateral spastic hemiparesis
medial lemniscus: contralateral loss of tactile/position/vibration sensation
fibers of VI: medial strabismus
What is the occluded artery in lateral pontine syndrome?
AICA anterior inferior cerebellar artery
What is the presentation of lateral pontine syndrome and affected parts of this area of the brain?
- middle cerebellar peduncle: ipsilateral ataxia
- vestibular nuclei: vertigo, nausea and vomiting, nystagmus
- facial nucleus and fibers: ipsilateral facial paralysis; ipsilateral loss of taste (anterior two-thirds of tongue), lacrimation, salivation, and corneal reflex; hyperacusis
- spinal trigeminal nucleus/ tract: ipsilateral pain/ temperature loss (face)
- spinothalamic tract: conntralateral pain/ temperature loss (body)
- cochlear nucleus/ VIII fibers: ipsilateral hearing loss
- descending hypothalamics: ipsilateral Horner Syndrome
What is pontocerebellar angle syndrome usually caused by?
an acoustic neuroma (schwannoma) of CN VIII
Another name for a dorsal midbrain syndrome?
parinaud syndrome
What is parinaud syndrome typically caused by?
tumor in the pineal gland
What are the areas of the brain affected and the characteristics of Parinaud syndrome?
- superior colliculus/pretectal area: paralysis of upward gaze, various pupillary abdnormalities
- cerebral aqueduct: noncommunicating hydrocephalus
What artery is affected in medial midbrain syndrome?
branches of PCA
What is another name for medial midbrain syndrome?
Weber syndrome
What areas of the brain and characteristics are there for Weber Syndrome?
- Fibers of III: ipsilateral oculomotor palsy (lateral strabismus, dilated pupil, ptosis)
- corticospinal tract: contralateral spastic hemiparesis
- corticobulbar tract: contralateral hemiparesis of the lower face
In general, how do cortex or capsular lesions present on the body?
complete anesthesia and lower face weakness contralaterally
- all sensory system lesions from face or body produce contralatral deficits
- lesion of corticobulbar fibers produces contralateral lower face weakness
In general, how do brain stem lesions present?
- Long track findings: all give rise to contralateral deficits
- lesion is at brain stem: at level of cranial nerve affected and on same side as cranial nerve findings
What are the findings of a hemisection of the spinal cord in general?
- long track findings: not all on one side; loss of pain and temperature separate from others
- lesion is at spinal cord level on side opposite P and T loss
- spastic weakness
- altered vibratory sense
- 2 signs ipsilateral and below lesion one sign contralateral and below lesion
- no CN signs.
Neurons found where degenerate in Alzheimer disease?
both the raphe and locus caeruleus degenerate
Where is the reticular formation located?
in the brain stem and functions to coordinate and integrate the actions of different parts of the CNS
What is the purpose of the reticular formation?
plays an important role in the regulation of muscle and reflex activity and control of respiration, cardiovascular responses, behavioral arousal, and sleep
What are raphe nuclei? Where is it found and what is its extent?
narrow column of cells in the midline of the brain stem extending from the medulla to the midbrain.
Function of raphe nuclei? (what may it play a role in?)
mood, aggression, and the induction of non-rapid eye movement (non REM sleep)
What do some of the areas of the raphe nuclei produce?
synthesize serotonin (5-hydroxytryptamine 5-HT from 1 tryptophan and project to vast areas of the CNS
What nucleus in raphe nuclei produce serotonin?
dorsal raphe nucleus
Are raphe nuclei part of reticular nuclei?
yes
Cells in the locus coeruleus synthesize what? What is their function?
NE and send projections to most brain areas involved in control of cortical activation
Decreased levels of what neurotransmitter are implicated in REM (paradoxic) sleep?
NE
What are the periaqueductal (central) gray areas of reticular nuclei? What receptors are found here?
collection of nuclei surrounding the cerebral aqueduct in the midbrain. Opioid receptors are present on the periaqueductal gray cells.
Projections on periaqueductal gray cells descend to modulate pain found where?
at the level of the dorsal horn of the spinal cord
