Anatomy Atlas

Medulla oblongata

Medulla oblongata
Also: Medulla · Wallenberg syndrome · Lateral medullary syndrome · Pyramidal decussation · Area postrema
OrganHigh-yielddraftNeuro

Lowest part of the brainstem, continuous with the spinal cord at the foramen magnum. It contains the cardiorespiratory centers, the nuclei of CN IX–XII and the pyramidal decussation; PICA strokes cause the lateral medullary (Wallenberg) syndrome.

Core anatomy

Location

From the lower border of the pons to the foramen magnum, where it becomes the spinal cord; in front of the cerebellum and the lower fourth ventricle.

Parts
  • Pyramids (ventral): corticospinal tracts; about 85–90% cross in the pyramidal decussation at the medulla–cord junction (see corticospinal tract)
  • Olives (inferior olivary nucleus → cerebellum via the inferior cerebellar peduncle)
  • Nuclei: hypoglossal (XII), dorsal motor nucleus of X, nucleus ambiguus (IX, X — swallowing, voice), nucleus of the solitary tract (taste, visceral afferents), spinal trigeminal nucleus and tract (ipsilateral face pain/temperature), vestibular nuclei, gracile and cuneate nuclei (dorsal columns → sensory decussation → medial lemniscus)
  • Cardiovascular and respiratory centers (reticular formation); area postrema — chemoreceptor trigger zone for vomiting (outside the blood–brain barrier)
  • Descending sympathetic fibers in the lateral medulla (lesion → Horner syndrome)
Relations

The cerebellar tonsils lie just above the foramen magnum behind the medulla.

Arterial supply

Vertebral arteries, PICA (lateral medulla), anterior spinal artery (medial medulla) — see vertebrobasilar system.

Venous drainage

Medullary veins → inferior petrosal sinus and spinal veins.

Notes

CN IX, X (postolivary sulcus), XI (lateral), XII (preolivary sulcus) emerge here — see glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), hypoglossal nerve (CN XII).

Mentioned in

Generated automatically from links in other entries.

Where the cranial nerves leave the brainstem (ventral view)The front of the brainstem. The optic nerves meet at the chiasm above. The oculomotor nerve emerges from the interpeduncular fossa between the cerebral peduncles of the midbrain. The trochlear nerve is the only one to leave from the back, just below the inferior colliculus, and winds forward around the peduncle. The trigeminal nerve leaves the lateral pons. The abducens leaves at the pontomedullary junction near the midline; the facial and vestibulocochlear nerves leave at the cerebellopontine angle. The glossopharyngeal and vagus nerves leave the postolivary sulcus of the medulla, the hypoglossal leaves the preolivary sulcus between the pyramid and the olive, and the accessory nerve rises from the upper cervical cord.Optic (II)Oculomotor (III)Trochlear (IV) — from the dorsal sideTrigeminal (V)Abducens (VI)Facial (VII)Vestibulocochlear (VIII)Glossopharyngeal (IX)Vagus (X)Accessory (XI) — from C1–C5Hypoglossal (XII)Midbrain (cerebral peduncle)PonsPyramidOliveSpinal cordMedullaVentral view · dashed IV leaves from the back

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Where the cranial nerves leave the brainstem. Ventral view. III leaves the interpeduncular fossa of the midbrain; IV is the only nerve to leave from the back (dashed); V leaves the lateral pons; VI the pontomedullary junction near the midline; VII and VIII the cerebellopontine angle; IX and X the postolivary sulcus; XII the preolivary sulcus between pyramid and olive; and XI rises from the upper cervical cord. Nuclei follow the same levels: III–IV midbrain, V–VIII pons, IX–XII medulla.
Original schematic, created for this atlas.
Anterior view of the pons and medulla showing the pyramids, the olives, the decussation of the pyramids and the middle cerebellar peduncle (brachium pontis)
Pyramids and olives on the front of the medulla.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 679. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))
Scheme of fibers passing from the spinal cord into the medulla, showing the crossing corticospinal (pyramidal) fibers at the decussation of the pyramids
Scheme of the decussation of the pyramids.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 680. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))

Clinical correlations

Lateral medullary (Wallenberg) syndrome PANCE

Mechanism / lesion

Occlusion of the vertebral artery or PICA (dissection, atherosclerosis).

Classic presentation

Ipsilateral loss of pain/temperature on the face (spinal trigeminal) with contralateral loss on the body (spinothalamic); dysphagia, hoarseness, reduced gag (nucleus ambiguus); ipsilateral Horner syndrome; vertigo, nystagmus, nausea (vestibular); ipsilateral limb ataxia; hiccups. No limb weakness.

Medial medullary syndrome PANCE

Mechanism / lesion

Occlusion of the anterior spinal artery or vertebral paramedian branches.

Classic presentation

Contralateral hemiparesis (pyramid), contralateral loss of proprioception/vibration (medial lemniscus), ipsilateral tongue deviation (XII).

Tonsillar herniation and Chiari I malformation PANCE

Mechanism / lesion

Cerebellar tonsils pushed through the foramen magnum, compressing the medulla (raised ICP, posterior fossa mass, or lumbar puncture with a mass lesion); Chiari I — congenital tonsillar descent.

Classic presentation

Herniation: neck stiffness, Cushing triad (hypertension, bradycardia, irregular respirations), then respiratory arrest. Chiari I: occipital headache worse with cough/Valsalva, syringomyelia (cape-like loss of pain/temperature).

High-yield PANCE pearls

  • Ipsilateral face + contralateral body pain/temp loss + dysphagia/hoarseness + Horner → Wallenberg (PICA/vertebral).
  • Contralateral hemiparesis + contralateral proprioception loss + ipsilateral tongue → medial medullary (anterior spinal).
  • Cushing triad: hypertension, bradycardia, irregular breathing → impending herniation.
  • Medulla = CN IX, X, XI, XII + cardiorespiratory centers.
  • Area postrema = chemoreceptor trigger zone (vomiting).

Imaging anatomy

CT

CT for hemorrhage and signs of raised ICP; image before lumbar puncture when a mass is possible.

MRI

MRI with DWI — medullary infarcts (often missed on CT); sagittal MRI for Chiari malformation and syrinx; MRA/CTA for vertebral dissection.

Physical exam

Strength / function testing

Palate elevation, gag, voice and swallow (IX, X), tongue (XII), SCM/trapezius (XI); facial and body pinprick/temperature (crossed sensory loss), pupils and ptosis (Horner), limb coordination, nystagmus.

Self-quiz

Q1.

A 48-year-old has sudden vertigo, hoarseness and difficulty swallowing. Exam shows a small left pupil with ptosis, reduced pain sensation on the left face and the right side of the body, and left limb ataxia. Strength is normal. Which artery is occluded?

Show answer

B

Lateral medullary (Wallenberg) syndrome from left PICA/vertebral occlusion: crossed pain/temperature loss, nucleus ambiguus signs (dysphagia, hoarseness), ipsilateral Horner and ataxia, with no weakness.

Q2.

A patient with a large cerebellar hemorrhage becomes hypertensive with a heart rate of 44/min and irregular breathing. What is happening?

Show answer

B

The Cushing triad signals raised ICP with brainstem (medullary) compression — impending tonsillar herniation. Posterior fossa masses need urgent neurosurgical decompression.

Q3.

The area postrema of the medulla has which function?

Show answer

A

The area postrema lies outside the blood–brain barrier and acts as the chemoreceptor trigger zone for vomiting.

Q4.

A 30-year-old has occipital headaches worse with coughing and a cape-like loss of pain and temperature over the shoulders. MRI shows the cerebellar tonsils below the foramen magnum. What is the diagnosis?

Show answer

E

Chiari I malformation is congenital descent of the cerebellar tonsils, causing occipital headache with cough/Valsalva and often a syrinx (cape-like pain/temperature loss).

Q5.

In lateral medullary syndrome, damage to which nucleus causes dysphagia and hoarseness?

Show answer

C

The nucleus ambiguus supplies the pharyngeal and laryngeal muscles (CN IX, X), so its damage causes dysphagia, hoarseness and a reduced gag. The spinal trigeminal nucleus causes the ipsilateral face pain/temperature loss.

Flashcards

See also