Intro to Brainstem II Flashcards
The Rule of 4 of the brainstem
?
General guides for localization of brainstem lesions
The long tracts serve as “meridians of longitude” whereas the cranial nerves serve as “parallels of latitude”.
Your goal is to establish where they intersect on your patient.
Most long tract lesions in brainstem will be contralateral; most cranial nerve signs will be ipsilateral to the lesion.
Your patient presents with contralateral weakness and contralateral loss of vibration/proprioception in arms and legs.
You suspect:
brainstem lesion but this could be anywhere in brainstem above caudal medulla. It doesn’t tell you midbrain, pons or rostral medulla.
Check cranial nerves for leve
Midbrain: 3, 4
Pons: 5, 6, 7, 8
Medulla: 9,10,11,12
Midbrain CN
3, 4
Pons CN
5, 6, 7, 8
Medulla CN
9,10,11,12
Cranial nerve NUCLEI locations in the brainstem
Midbrain
III
edinger westphal nucleus
IV
Cranial nerve NUCLEI locations in the brainstem
Pons
V Mesencephalic nucleus of V Primary Motor Nucleus of V Main Sensory nucleus of V Spinal nucleus of V (at caudal pons) VI VII VIII (cochlear nucleus and vestibular nucleus at pontomedullary junction)
Cranial nerve NUCLEI locations in the brainstem
Medulla
IX (nucleus of solitary tract)
X (nucleus of solitary tract, dorsal motor nucleus of vagus and ventral motor nucleus of vagus aka nucleus ambiguous)
XII (hypoglossal nucleus)
(Spinal nucleus of V is here too)
(LR6SO4)3
CN 3 does everything but
Lateral Rectus
Superior oblique
CN 3 is between
superior cerebellar (below) and posterior cerebral arteries
Uncus herniation hurts
CN 3
Cranial nerve NUCLEI
collection of neurons (gray matter) in the brain stem that is associated with one or more cranial nerves.
Axons carrying information to and from the cranial nerves form a synapse first at these nuclei.
Lesions occurring at these nuclei can lead to effects resembling those seen by the severing of nerve(s) they are associated with.
All the nuclei except that of the trochlear nerve (CN IV) supply nerves of the same side of the body.
All the nuclei except that of the ______ supply nerves of the same side of the body.
trochlear nerve (CN IV)
Mesencephalic nucleus of V
Primary Motor Nucleus of V
Main Sensory nucleus of V
Spinal nucleus of V (at caudal pons)
Trigeminal Nerve
The _______ is involved with proprioception of the face, that is, the feeling of position of the muscles.
mesencephalic nucleus
____________ is the parasympathetic preganglionic nucleus that innervates the iris sphincter muscle and the ciliary muscle.
Edinger–Westphal nucleus (accessory oculomotor nucleus)
The _______ : All acoustic information thus enters the brain through this, where the processing of acoustic information begins. The outputs from are received in higher regions of the auditory brainstem.
cochlear nuclear complex
Pupillary light reflex
Shining light in one eye will cause pupillary constriction in both eyes
Afferent = II (Sensory fibers from retina)
Efferent = III (parasympathetic fibers to ciliary ganglion)
MLF*
Medial Long Fasciculus
Coordinating eye movements with head movements
MLF
CN NUCLEI 3, 4, 6, 8
Also involves cerebellum, medial vestibulospinal tract (to coordinate neck muscles also)
VOR
Vestibulo–ocular reflex (VOR)
a reflex eye movement that elicits eye movement by stimulating the vestibular system. This reflex functions to stabilize images on the retinas (in yoked vision) during head movement by producing eye movements in the direction opposite to head movement, thus preserving the image on the center of the visual field(s).
pre-ganglionic parasympathetic vagal neurons to heart and thoracic & abdominal viscera
Dorsal motor nucleus of X
Vagal Pathways
motor vagal neurons to muscles of pharynx, larynx (swallowing, phonation, movement of uvula, gagging)… this nucleus also contains motor fibers to stylopharyngeus muscle which helps in phonation and swallowing (but not gagging)
Nucleus ambiguous
Vagal Pathways
= special sensory (taste) from 7, 9, 10
Solitary Nucleus
Vagal Pathways
GAG REFLEX
Touching the wall of one side of the pharynx elicits bilateral gagging response
Afferent = IX (Sensory fibers)
Efferent = X (Nucleus Ambiguous)
JAW JERK REFLEX
Downward tapping of jaw causes biilateral contraction of masseter
Afferent = mesencephalic nucleus of V (stretch receptors in masseter)
Efferent = main motor nucleus of V
FINE TOUCH
PRESSURE
VIBRATION
FROM FACE
ASCENDING!
1st order nucleus = trigeminal ganglion
2nd order nucleus = main sensory nucleus of V
3rd order nucleus = VPM of Thalamus
CORNEAL BLINK REFLEX:
Cornea is touched by a foreign object both eyes blink
Afferent = spinal nucleus of V
Efferent = motor nucleus of VII
Pain and Temperature from face
ASCENDING!
1st order nucleus = trigeminal ganglion
2nd order nucleus = spinal nucleus of V
3rd order nucleus = VPM of Thalamus
The main motor nucleus of the trigeminal is to the face what the ____________ in ventral horn are for the body (voluntary control of skeletal muscle).
alpha motor neurons
The main sensory nucleus of the trigeminal is to the face what the _____ is for the body (fine touch, vibration, pressure).
NG or NC
The mesencephalic nucleus of the trigeminal is to the face what the ______ is for the body (proprioception).
DRG
The spinal nucleus of the trigeminal is for the face what the ______ is for the body (pain and temp).
N. Proprius
CN ___ Loops around CN 6
7
Thus damage to 6 hurts 7 often
Cortiocobulbar tract
a two neuron white matter motor pathway connecting the cerebral cortex to the brainstem primarily involved in carrying the motor function of the non-oculomotor cranial nerves. The corticobulbar tract is one of the pyramidal tracts, the other being the corticospinal tract.
CN V motor lesion
Jaw deviates TOWARD lesion
CN X lesion
Uvula deviates AWAY from lesion
CN XII lesion
Tongue deviates TOWARD lesion
lick your wounds
a group of large motor neurons, situated deep in the medullary reticular formation. The nucleus ambiguus contains the cell bodies of nerves that innervate the muscles of the soft palate, pharynx, and larynx which are strongly associated with speech and swallowing.
nucleus ambiguus
IX, X
BILATERAL UMN:
3, 4, 5, 6,
Upper of 7
N. Ambiguous (10)
CONTRALATERAL UMN
Lower of 7
Hypoglossal (12)
All LMN are _____ onto their targets except for 4
ipsilateral
