Medulla Anatomy And Clincial Correlations

Question 1

How to view the medulla and pons posteriorly

Answer 1

Look at the rhomboid fossa and find the lateral recess

• above lateral recess = pons
• below lateral recess = medulla

Medullary has “open and closed” portions

• open = caudal half of the rhomboid fossa
• closed = obex point and caudal from that point (note: obex is the tip of the most caudal part of the rhomboid fossa, also where 4th ventricle narrows to become the central canal)

Question 2

What trigone are found in the medulla?

Answer 2

Vagal and hypoglossal trigone

- contain the corresponding nuclei

Question 3

Caudal medulla

Answer 3

motor (descending) fibers/tracts decussate first (caudal-caudal medulla), and then sensory (ascending) fibers/tracts decussate next (rostral-caudal medulla)

Anterior/central portion of caudal medulla

• decussation of the pyramids (motor)
• contains nuclei of the accessory nerve
• medial lemniscus decussation (sensory)
• contains internal arcuate fibers

Lateral potion of the caudal medulla

• contains the spinal trigeminal tract and nucleus
• contains anterolateral system
• contains spinocerebellar fibers

Posterior portion of the caudal medulla

• contains the gracile and cuneate fasciculus
• contains nucleus ambiguus

Central gray matter of the caudate medulla (surrounds central canal)

• contains some of the hypoglossal and vagal
• solitary nucleus and tract motor nuclei

Question 4

Mid-medullary level contents

Answer 4

Anterior/central medulla

• inferior olivary nucleus
• corticospinal fibers (pyramids)
• medial lemniscus

Lateral medulla

• spinal trigeminal tract and nucleus
• nucleus ambiguus
• anterolateral system

Posterior medulla:

• hypoglossal nuclei
• dorsal motor vagal nuclei
• vestibular nuclei
• solitary tract and nuclei

Question 5

Rostral medulla contents

Answer 5

larger and extends more dorsal and laterally to account for inferior cerebellar peduncle

Anterior and medial medulla

• inferior olivary nucleus
• corticospinal fibers (pyramids)
• medial lemniscus

Lateral medulla

• CN 8 nuclei (vestibular and cochlear nuclei)
• spinal trigeminal tract
• solitary tract and nucleus (gustatory)

Rhomboid fossa

• hypoglossal nucleus
• inferior salivatory nucleus

Question 6

Medial medullary syndrome (Dejerines)

Answer 6

Caused by lesions to the anterior spinal and/or paramedian branches of the vertebral artery

Involves:

• pyramids
• medial lemniscus
• hypoglossal nerve

clinical presentation:

• contralateral hemiplegia (body weakness)
• caused by loss of ipsilateral pyramid (which holds contralateral fibers)*
• contralateral loss of vibration position and discriminatory touch
• caused by loss of ipsilateral medial lemniscus (which contains contralateral ascending fibers) *
• ipsilateral weakness of the tongue
• caused by loss of ipsilateral hypoglossal nucleus (which has already decussate)*

Question 7

Lateral medullary syndrome (Wallenberg)

Answer 7

Caused by vertebral and/or PICA inclusions

Involves:

• spinal trigeminal tract and nucleus
• nucleus ambiguus
• vestibular nuclei
• anterolateral system (spinothalamic tract)
• hypothalamospinal fibers (sympathetic fibers)

Clincial presentation:

• ipsilateral loss of pain and thermal sense of the face
• (Because of spinal trigeminal tract and nucleus damage, these do not decussate)*
• hoarseness, deviation of uvula to contralateral side of lesion and dysphagia
• (because nucleus ambiguus is damaged which contains motor for CN 9/10 nuclei)*
• nystagmus, vertigo, nausea, ataxia
• (because nucleus ambiguus and vestibular nuclei are damaged which contains motor for CN 9/10 nuclei and spatial orientation)*
• contralateral loss of pain and thermal sense of the body (spares the face)
• (due to spinaltholamic tract is knocked, decussate in the spinal cord so the contralateral side would be affected)*
• horners syndorme
• (due to hypothalamic fibers being damaged)*