Medulla Oblongata

Embryologically, what is the medulla oblongata formed from?

Mylencephalon

Which ventricle is associated with the medulla?

4th ventricle

Which CN nuclei are found in the medulla?

• CN V, Trigeminal

• CN IX, Glossopharyngeal

• CN X, Vagus

• CN XI, Spinal Accessory

• CN XII, Hypoglossal

Which CNs emerge from the pontomedullary junction?

• CN VI, Abducens

• CN VII, Facial

• CN VIII, Vestibulocochlear

What structures are found in the medulla?

• 4th ventricle

• All tracts b/w SC & brain

• CN nuclei V, IX-XII

• Reticular formation

• Vertebral arteries

What are the 2 sections of the medulla?

1. Rostral / Open → 4th ventricle mostly

2. Caudal / Closed → continuous with SC, obex, rostral end of central canal

What are the external features of the anterior medulla?

• Pyramids

• Olives

• CN XII, Hypoglossal

• Pontomedullary junction

What is significant about the medullary pyramids?

• Descending CST fibers

• 85-95% CST fibers cross

• UMNs for UEs & LEs

What are the inferior olivary nuclei?

• Climbing/ascending fibers to cerebellum

• Aid in motor learning

What are the external features of the lateral medulla?

• CN IX, Glossopharyngeal

• CN X, Vagus

• CN XI, Spinal Accessory

What are the external features of the posterior medulla?

• Fasciculus cuneatus & gracilis (DC)

• Nucleus cuneatus & gracilis

• Obex

• Floor of 4th ventricle

• Inferior cerebellar peduncle

What information does the inferior cerebellar peduncle carry?

• Afferent axons to cerebellum

• From dorsal spinocerebellar tract, inferior olivary nuclei, & vestibular nuclei

What are the internal features of the medulla?

• Nuclei of CN IX, X, XI, XII

• Spinal Trigeminal Nucleus (CN V)

• Vestibular Nuclei (CN VIII)

• Reticular formation

• Raphe Nuclei

Which descending pathways run through the medulla?

• CST

• Vestibulospinal tracts

• Reticulospinal tracts

• Rubrospinal tracts

• Corticobulbar tracts

• Spinal trigeminal tract

Which ascending pathways run through the medulla?

• Medial Lemniscus

• STT

• Spinocerebellar tracts

• Medial Longitudinal Fasciculus (MLF)

What is the reticular formation?

• Several loosely organized groups of neurons found in brainstem

• Control CPGs: breathing, coughing, ingestion, BP, vomit, cardiac centers

• Connect to SC through reticulospinal tract

What is the raphe nuclei?

• Nuclei that produce serotonin to modulate sleep

• Synapse onto dorsal horns of SC to lessen response to painful stimuli

What is the corticobulbar tract?

• Descending motor pathway made up of UMNs from pre-central gyrus

• Sends motor commands from cortex to CN motor nuclei (LMNs)

• Most CN nuclei receive bilateral UMN input (NOT CN VII)

• Does NOT include CN III, IV, & VI

What is the spinal trigeminal tract?

• Carries ONLY pain & temperature from face & oral cavity

• Trigeminal ganglion → enter pons → descend to spinal trigeminal nucleus → cross → ascend as trigeminothalamic tract → thalamus → sensory cortex

What is the medial lemniscus?

• DC synapse & cross in medulla

What is the spinocerebellar tract?

• Dorsal → unconscious proprioceptive info from Clark’s nucleus to cerebellum through inf cerebellar peduncle

• Ventral → enters cerebellum through sup cerebellar peduncle at level of midbrain

What is the medial longitudinal fasciculus (MLF)?

• Tract that coordinates eye movements with head & neck movements

• Carries ascending & descending motor fibers that link the vestibular system, oculomotor nuclei, & neck muscles

• Highway that coordinates VOR & VSR

• Descending portion becomes medial vestibulospinal tract

What is the vestibulo-ocular reflex (VOR)?

Keeps your eyes steady when your head moves

What is the vestibulo-spinal reflex (VSR)?

Coordinates neck muscle activity to stabilize head & eyes

Where does the blood supply of the medulla come from?

• Vertebral-basilar system

• Vertebral arteries (ASA, PSA, PICA)

What vascular structure is typically occluded in medulla lesions with crossed findings?

PICA

What is meant by “crossed findings” in a medulla lesion?

Ipsilateral loss of pain & temperature to the face/head with contralateral loss of pain & temperature to the body

What is Lateral Medullary Syndrome / Wallenberg Syndrome?

• Lesion of the medulla from a PICA stroke

• Ipsilateral loss of pain/temperature of face

• Contralateral loss of pain/temperature of body

• Vertigo, nystagmus, nausea

• Dysarthria & dysphagia

• Ipsilateral ataxia

• Ipsilateral Horner’s syndrome