Brainstem III: Medulla

Question 1

What are the 2 major decussations in the medulla?

Answer 1

Dorsal columns become medial lemniscus (ascending pathway)

pyramidal tracts (descending pathway)

Question 2

Fasiculus gracilis and cuneatus

Answer 2

continues from dorsal column of spinal cord for conscious proprioception, vibratory sense, and fine tactile info.

Come up and synapse into nuclei

Question 3

Location of nucleus gracillis and cuneatus with respect to one another

Answer 3

gracillis - medial

cuneatus - lateral

Question 4

Fibers traveling in pyramids carry what?

Answer 4

Motor fibers continue into spinal cord as CST pathways or stop at cranial nerve nuclei as corticobulbar pathways…pyramidal decussation fibers become dorsolateral CST (90%) and 10% remain uncrossed as ventral CST

Question 5

Difference between “closed” and “open” medulla

Answer 5

“open” medulla contains more “open” 4th ventricle and is more rostral

Question 6

Gracillis and cuneatus get sensation from which parts of body

Answer 6

gracillis - lower body (under T6)

cuneatus - upper body

Question 7

Lesion of pyramidal tract results in what?

Answer 7

Upper motor lesion symptoms (i.e. HYPERreflexia)

Question 8

Medial lemniscus arises from what?

Answer 8

Dorsal columns of spinal cord (ascending somatosensory fibers)

Question 9

Pathway of fasciculus gracilis and cuneatus

Answer 9

terminate and synase with neurons of nucleus gracilis and cuneatus respectively. 2nd order neurons from these nuclei decussate to ventral aspect as internal arcuate fibers to form medial lemniscus. Lemniscus ascends rostrally through medulla and terminates in VPL of thalamus

Question 10

Medial longitudinal fasciculus (MLF)

Answer 10

Ascending fibers from vestibular nuclei to III, IV, VI (eye movements) and descending from medial vestibular nucleus which projects to neck muscles for visual tracking function

Question 11

Spinal nucleus of V

Answer 11

• extends through medulla as far as C2

- mediates pain and temperature of head, replaces substantia gelatinosa

Question 12

What other pathways are in medulla?

Answer 12

SST - pain and temp from contral lateral side (ducessation ocurs in spinal cord)

spinocerebellar - proprioceptions from muscle spindle fibers to cerebellum (remains ipsilateral)

tectospinal tract - from superior colliculus of midbrain, follows MLF to cervical levels and mediates neck postural movements

Question 13

What are the decussation fibers from nucleus gracillis and cuneatus called as they form medial lemniscus?

Answer 13

Internal arcuate fibers

Question 14

Where does the medial lemniscus terminate?

Answer 14

VPL of thalamus

Question 15

Accessory cuneate nucleus

Answer 15

at edge of nucleus cuneatus, muscle spindles and Golgi tendon organs of UPPER limb…projects to ICP as cuneocerebellar tract (unconscious proprioception of upper limb)

Question 16

Medial medullary syndrome

Answer 16

• lesion of anterior spinal branches of vertebral arteries
• loss of sensation from contralateral body (medial lemniscus)
• contralateral upper motor neuron paralysis (pyramids, CST)
• ipsilateral tongue paralysis (hypoglossal nucleus XII)

Question 17

What structures are in the medial medulla?

Answer 17

From ventral to dorsal:

pyramids (CST), medial lemniscus (DC), tectospinal tract (coordinating eye and neck), MLF (vestibular nuclei with eye muscle III, IV, VI), and hypoglossal nucleus

Question 18

What structures are in the lateral medulla?

Answer 18

inferior olivary nucleus (relay for afferent signals to cerebellum

reticular formation

vestibular nuclei

Question 19

lateral medullary syndrome (Wallenberg’s)

Answer 19

• lesion to PICA (posterior inferior cerebellar artery)
• loss of contralateral pain and temp (STT)
• loss of pain and temperature from ipsilateral face (spinal nucleus of V)
• loss of gag reflex, hoarseness, difficulty with speech and swallowing (nucleus ambiguous of IX and X)
• possible loss of sympathetics (Horner’s)