Brainstem Morphology Flashcards
mesencephalon
roof: tectum
ventricular cavity: cerebral aqueduct
basilar portion: crura cerebri
tegmentum
consistently located b/w the ventricular system and the basilar portion of the midbrain, pons, and medulla
metencephalon
roof: cerebellum
ventricular cavity: 4th ventricle
basilar portion: pons
myelencephalon
roof: posterior columns
ventricular cavity: central canal
basilar portion: pyramids
blood supply to the brainstem
- branches from the circle of Willis, vertebral As, and basilar As
- highly vascularized and vulnerable to thrombosis and emboli
- penetrating As have a wedge shaped pattern of distribution–thrombosis of one of the As would result in a wedge shaped region of infarction
spinal lemniscus
- sensory
- conveys pain and temp info from the opposite 1/2 of the body
- either lateral or posterolateral to ML
medial lemniscus
- sensory
- conveys prop, 2 pt, and vibratory sensations from opposite 1/2 of body
- at level of upper pons and midbrain, the ML also contains fibers that convey taste info from ipsilateral 1/2 of the tongue and pharynx
trigeminal lemniscus
- conveys pain, temp, and crude tactile sensations from the opposite 1/2 of face
- located b/w ML and SL
lateral lemniscus
- conveys bilateral auditory info, but predominantly info from opposite ear
- located in lateral aspect of brain
medial longitudinal fasciculus
- conveys vestibular influences to the CN 3, 4, 6
- contains fibers for oculomotor N
- located next to midline and anterior to central gray
- in medulla and lower pons, located in dorsal tip of ML
internuclear ophthalmoplegia
- lesion of medial longitudinal fasciculus
- have an abnormal response to horizontal gaze in direction opposite the side of the lesion
- horizontal gaze contralateral to MLF lesion is abnormal
- named according to side of Oculomotor impairment
- ex: if horizontal to R is normal and disconjugate to left, so R eye does not adduct, then there is right INO due to lesion of R MLF
- ex: if horizontal to L is normal and disconjugate to left (L eye does not adduct), then there is a left INO with lesion of L MLF
-bilateral in young pts with MS or unilateral in order pts with vascular dz
unilateral lesion of medial longitudinal fasciculus
-impairment or loss of adduction (MR) of ipsilateral eye and nystagmus of abducting eye
corticospinal tract
- conveys descending motor info from motor cortex
- unilateral lesion: contralateral spastic hemiplegia
corticobulbar tract
- brainstem CN motor nuclei and innervated by corticobulbar fibers
- most decussate in lower pons b/w trigeminal and abducens N
- unilateral lesion of CBF result in denervation of brainstem motor nuclei below level of lesion
unilateral lesion of CBF above level of decussation
contralateral paralysis or paresis of mimetic Ms of lower 1/2 of face–supranuclear facial palsy
-as well as other cranial palsies due to denervation of abducens nucleus, hypoglossal nucleus, and nucleus ambiguus
lesions of CBF below the decussation
ipsilateral cranial nerve palsies
supra nuclear facial palsy
- upper quadrant of face is unaffected by unilateral lesion of CBF
- unilateral lesion of CBF to the facial nucleus results in paralysis of contralateral lower quadrant of face
cranial N by level
- telencephalon: I
- diencephalon: 2
- mesencephalon/midbrain: 3, 4
- metencephalon/pons: 5
- pontomedullary sulcus: 6, 7, 8
- myelencephalon/medulla oblongata: 9-12
lesion at the level of the diencephalon
optic N, chiasm, tract
-visual field blindness
lesion of midbrain
- oculomotor N–external strabismus, pupillary dilation, complete ptosis
- trochlear N–can’t adduct and depress eye
lesion of pons
trigeminal N–ipsilateral loss of sensations from 1/2 of face, paralysis and atrophy of ipsilateral Ms of mastication
-when pt opens his mouth wide, chin deviates toward side of lesion
lesion of pontomedullary sulcus
- abducens N–ipsilateral paralysis of lateral gaze and internal strabismus
- facial N–ipsilateral Bell’s palsy, loss of taste sensations from the anterior 2/3 of tongue, hyperacusis
- vestibulocochlear N–ipsilateral deafness, problems with equilibrium and posture, and nystagmus
lesion at level of medulla
- glossopharyngeal N–dec sensation from palate and pharynx and loss of taste from posterior 1/3 of tongue
- vagus N–dysphagia, dysarthria, hoarseness, paralysis or paresis of Ms of palate
- uvula may deviate to side opposite the lesion
- spinal accessory N–pt can’t turn head away from affected side or shrug shoulders
- hypoglossal N–atrophy of ipsilateral intrinsic Ms of tongue, dysarthria, dysphagia, protruded tongue deviates towards side of lesion
lesion of nucleus ambiguus
- deviation of uvula away from affected lesion
- dysarthria, dysphagia, hoarseness
what determines the level and side of lesion?
the highest affected cranial N
anterior white commissure lesion
- syringomyelia
- bilateral loss of pain and temp–yoke like
descending nucleus and tract of V lesion
-unilateral hemianalgesia and thermal hemianalgesia of face
inferior olivary nucleus
- receives CTF
- projects to cerebellum
spinal lemniscus lesion
-contralateral hemianalgesia of body
medial lemniscus lesion
contralateral loss of prop and 2 pt tactile from body
medial longitudinal fasciculus
internuclear ophthalmoplegia
corticospinal tract lesion
contralateral spastic hemiplegia
pulvinar
tectal visual pathway
substantia nigra
- Parkinson’s dz
- afferents from striatum
- efferents to thalamic motor nuclei
mammillary body
-Korsakoff’s Syndrome
optic radiations lesion
contralateral homonymous hemianopsia
PLIC lesion
contralateral spastic hemiplegia
genu of internal capsule lesion
supra nuclear facial palsy
