Brainstem Morphology

Question 1

mesencephalon

Answer 1

roof: tectum
ventricular cavity: cerebral aqueduct
basilar portion: crura cerebri

Question 2

tegmentum

Answer 2

consistently located b/w the ventricular system and the basilar portion of the midbrain, pons, and medulla

Question 3

metencephalon

Answer 3

roof: cerebellum
ventricular cavity: 4th ventricle
basilar portion: pons

Question 4

myelencephalon

Answer 4

roof: posterior columns
ventricular cavity: central canal
basilar portion: pyramids

Question 5

blood supply to the brainstem

Answer 5

• 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

Question 6

spinal lemniscus

Answer 6

• sensory
• conveys pain and temp info from the opposite 1/2 of the body
• either lateral or posterolateral to ML

Question 7

medial lemniscus

Answer 7

• 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

Question 8

trigeminal lemniscus

Answer 8

• conveys pain, temp, and crude tactile sensations from the opposite 1/2 of face
• located b/w ML and SL

Question 9

lateral lemniscus

Answer 9

• conveys bilateral auditory info, but predominantly info from opposite ear
• located in lateral aspect of brain

Question 10

medial longitudinal fasciculus

Answer 10

• 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

Question 11

internuclear ophthalmoplegia

Answer 11

• 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

Question 12

unilateral lesion of medial longitudinal fasciculus

Answer 12

-impairment or loss of adduction (MR) of ipsilateral eye and nystagmus of abducting eye

Question 13

corticospinal tract

Answer 13

• conveys descending motor info from motor cortex

- unilateral lesion: contralateral spastic hemiplegia

Question 14

corticobulbar tract

Answer 14

• 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

Question 15

unilateral lesion of CBF above level of decussation

Answer 15

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

Question 16

lesions of CBF below the decussation

Answer 16

ipsilateral cranial nerve palsies

Question 17

supra nuclear facial palsy

Answer 17

• 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

Question 18

cranial N by level

Answer 18

• telencephalon: I
• diencephalon: 2
• mesencephalon/midbrain: 3, 4
• metencephalon/pons: 5
• pontomedullary sulcus: 6, 7, 8
• myelencephalon/medulla oblongata: 9-12

Question 19

lesion at the level of the diencephalon

Answer 19

optic N, chiasm, tract

-visual field blindness

Question 20

lesion of midbrain

Answer 20

• oculomotor N–external strabismus, pupillary dilation, complete ptosis
• trochlear N–can’t adduct and depress eye

Question 21

lesion of pons

Answer 21

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

Question 22

lesion of pontomedullary sulcus

Answer 22

• 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

Question 23

lesion at level of medulla

Answer 23

• 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

Question 24

lesion of nucleus ambiguus

Answer 24

• deviation of uvula away from affected lesion

- dysarthria, dysphagia, hoarseness

Question 25

what determines the level and side of lesion?

Answer 25

the highest affected cranial N

Question 26

anterior white commissure lesion

Answer 26

- syringomyelia | - bilateral loss of pain and temp--yoke like

Question 27

descending nucleus and tract of V lesion

Answer 27

-unilateral hemianalgesia and thermal hemianalgesia of face

Question 28

inferior olivary nucleus

Answer 28

- receives CTF | - projects to cerebellum

Question 29

spinal lemniscus lesion

Answer 29

-contralateral hemianalgesia of body

Question 30

medial lemniscus lesion

Answer 30

contralateral loss of prop and 2 pt tactile from body

Question 31

medial longitudinal fasciculus

Answer 31

internuclear ophthalmoplegia

Question 32

corticospinal tract lesion

Answer 32

contralateral spastic hemiplegia

Question 33

pulvinar

Answer 33

tectal visual pathway

Question 34

substantia nigra

Answer 34

- Parkinson's dz - afferents from striatum - efferents to thalamic motor nuclei

Question 35

mammillary body

Answer 35

-Korsakoff's Syndrome

Question 36

optic radiations lesion

Answer 36

contralateral homonymous hemianopsia

Question 37

PLIC lesion

Answer 37

contralateral spastic hemiplegia

Question 38

genu of internal capsule lesion

Answer 38

supra nuclear facial palsy