Lesions affecting brainstem function Flashcards
what are the parts of the brainstem
medulla oblongata
pons
pituitary gland
thalamus
(most pirates parrots talk)
where are the cranial nerves situated
cranial nerves are in the brainstem which is the part that enters the brain after the spinal cord
what are the cranial nerves
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
vestibular
glossopharnageal
vagus
accessory
hypoglossal
where do the cranial nerves lieT
The4 cranial nerves in the medullaareCN 9-12:
Glossopharyngeal (CN9): ipsilateral loss of pharyngeal sensation
Vagus (CN10): ipsilateral palatal weakness
Spinal accessory (CN11): ipsilateral weakness of the trapezius and stemocleidomastoid muscles
Hypoglossal (CN12): ipsilateral weakness of the tongueThe 12th cranial nerve is the motor nerve in the midline of the medulla. Although the 9th, 10th and 11th cranial nerves have motor components, they do not divide evenly into 12 (using our rule) and are thus not the medial motor nerves.
The4 cranial nerves in the ponsareCN 5-8:
Trigeminal (CN5): ipsilateral alteration of pain, temperature and light touch on the face back as far as the anterior two-thirds of the scalp and sparing the angle of the jaw.
Abducent (CN6): ipsilateral weakness of abduction (lateral movement) of the eye (lateral rectus).
Facial (CN7): ipsilateral facial weakness.
Auditory (CN8): ipsilateral deafness.The 6th cranial nerve is the motor nerve in the medial pons. The 7th is a motor nerve but it also carries pathways of taste, and using the rule of 4 it does not divide equally in to 12 and thus it is not a motor nerve that is in the midline. The vestibular portion of the 8th nerve is not included in order to keep the concept simple and to avoid confusion. Nausea and vomiting and vertigo are often more common with involvement of the vestibular connections in the lateral medulla.
The4 cranial nerves above the ponsareCN 1-4:
Olfactory (CN1): not in midbrain.
Optic (CN2): not in midbrain.
Oculomotor (CN3): impaired adduction, supradduction and infradduction of the ipsilateral eye with or without a dilated pupil. The eye is turned out and slightly down.
Trochlear (CN4): eye unable to look down when the eye is looking in towards the nose (superior oblique).The 3rd and 4th cranial nerves are the motor nerves in the midbrain.
what is the pyramidal tract
carries information from the brain to the muscle
fibres originate in the cerebral cortex carrying upper motor nerves fibres to the spinal cord
(corticospinal) and brainstem (corticiobulbar)
transmits signals for the voluntary control of the musculature of the body and the face
no synapses within descending pathways
upper motor neurone from brain then lower motor neurone to the muscle
where do fibres pass in the pyramidal tract
fibres pass from the cereal cortex to the brainstem and the spinal cords
they synapse to the lower motor neurones
what are cerebral penducels
two stalks which attaches the cererbrum to the brainstalk (largest portion of the brain the pink cloudy bit
located on the anterior part of the midbrain
contains the easending and descending nerve fibres between the brain and the brainstem
what is the red nucleus
lies within the midbrain
the red nucleus is pale pink due to the presence of iron
recievies inputs from the cerebellum of the opposite side
and the motor cortex of the same side
function = coordinate motor movement
what are the three types of brainstem lesions
three categories
nucelar
internuclear
infra nuclear - below the level of the nuclei
generally nuclear palsies are a rare occurrence
and often associated with other neurological signs because of other structures in close proximity
what is the difference between nuclear , internuclear and infranuclear lesions
nuclear - lesion at the level of the nucleus
internuclear pathway - between two nuclei - i.e. the third and 6th -
infra nuclear - affects nerve not brain - e.g. hypertensive/ diabetic
describe the contents of the oculomotor nerve
2 nuclei
oculomotor nerve nucleus - superior rectus , inferior rectus , and levator palpabrae superioris
2 types of efferent nerve fibres - somatic innervate the (eoms) and visceral innervate the (sphincter and cillary body) - parasympathetic
where does the third nerve enter and exit the skull
originates at the level of the midbrain (superior colliculus) and leaves the skull from the superior orbital fissure
inside the third nerve what is each muscle innervated by
each muscle is innervated by the corresponding sub nucleus
all subnuclei innervate ipsilateral muscles
except from the superior rectus sub nucleus and the central caudal nucleus
what does the central central caudal nucleus innverate
the levator palpable superior
what does a lesion at the central caudal nucleus result in
central caudal nucleus (CCN) supplies both levator muscles
lesion results in bilateral ptosis
with and without superior rectus limitation
if bilateral limitation of elevation
- lesion affecting superior rectus sub nucleus
what are fasicualr lesions of the third cranial nerve
fascicular = whilst the nerve is travelling within the brainstem
if there is a unilateral limitation of elevation not the superior rectus subnucleus
involvement of the superior reectus nerve fascicles (axons after leaving the nucleus)
because axons from 1 superior rectus subnuclueu cross and pass through cintrlaterla as well as ipsilateral subnucleus
describe the course of the trochlear nerve
originates in the midbrain
only cranial nerve to exit from the posterior midbrain
smallest cranial nerve (by number of axons)
longest intracranial course
unable to distinguish between nuclear and fascicular lesions
describe the course of abducens nerve (6th)
rginates in the lower pons in the floor of the fourth ventricle lateral to the medial longitudinal fasiculus
nerves exits at the junction of the medulla and the pons
it then courses over the medial petrous per towards the cavernous sinus
