An otherwise healthy 58-year-old man comes to the physician because of a 1-year history of episodic coughing whenever he cleans his left ear. There is no history of hearing loss, tinnitus, or vertigo. Stimulating his left ear canal with a cotton swab triggers a bout of coughing. The physician informs him that these symptoms are caused by hypersensitivity of a cranial nerve. A peripheral lesion of this nerve is most likely to manifest with which of the following findings on physical examination?

Ipsilateral sensorineural hearing loss

Ipsilateral deviation of the tongue

Inability to raise ipsilateral eyebrow

Decreased secretion from ipsilateral sublingual gland

A 56-year-old man with a significant past medical history of diabetes mellitus, hypertension, and hypercholesterolemia is brought to the emergency department by his wife. The wife states the symptoms started 1 hour ago when she noticed that he was having difficulty swallowing his breakfast and that his voice was hoarse. The patient had a recent admission for a transient ischemic attack but was not compliant with his discharge instructions and medication. Examination of the eye shows left-sided partial ptosis and miosis along with diplopia and nystagmus. During the examination, it is noted that the right side of the face and body has markedly more sweating than the left side. An MRI of the brain reveals an ischemic infarct at the level of the left lateral medulla. Which of the following most likely accounts for this patient’s symptoms?

Denervation of the descending sympathetic tract

Postganglionic sympathetic lesion

Injury to the cervical sympathetic ganglia

Preganglionic lesion at the lateral gray horn

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

Medulla oblongata nuclei for USMLE Step 3: High-Yield Anatomy Lessons

Medulla Oblongata - The Vital Knot

Location: Most caudal brainstem part, transitioning to the spinal cord.
Key Surface Structures:
- Pyramids: Ventral bulges containing corticospinal (motor) tracts.
- Decussation: Site where pyramidal tracts cross the midline.
- Olives: Bulges lateral to pyramids; contain inferior olivary nucleus (motor learning).
Cranial Nerves (CN): Nuclei for CN IX, X, XI, and XII are located here.
- 📌 Mnemonic: The last four CNs (9, 10, 11, 12) are in the medulla, the "low down" part of the brainstem.

⭐ Wallenberg Syndrome: Occlusion of the Posterior Inferior Cerebellar Artery (PICA) causes this lateral medullary syndrome, presenting with contralateral body pain/temp loss and ipsilateral facial deficits.

Ventral Medulla Oblongata: Pyramids, Olives, Cranial Nerves

Cranial Nerve Nuclei - The Medulla's Command Center

Medulla oblongata cross-section with cranial nerve nuclei

The medulla houses critical nuclei for vital functions, coordinating inputs and outputs for several cranial nerves.

Nucleus	Cranial Nerve(s)	Function (Fiber Type)	Clinical Correlation
Nucleus Ambiguus	IX, X, XI (cranial root)	SVE	Motor: Pharynx/larynx muscles (swallowing, speaking). Lesion → hoarseness, dysphagia.
Solitary Nucleus	VII, IX, X	GVA, SVA	Sensory: Visceral sensation (carotid body/sinus), taste. Key for gag/cough reflexes.
Dorsal Motor Nucleus	X	GVE	Parasympathetic: Heart, lungs, upper GI tract.
Hypoglossal Nucleus	XII	GSE	Motor: Intrinsic & extrinsic tongue muscles. LMN lesion → tongue deviates toward lesion.

⭐ Wallenberg Syndrome (Lateral Medullary Syndrome): Infarction of the PICA (Posterior Inferior Cerebellar Artery) affects multiple structures. Damage to the Nucleus Ambiguus is a key feature, causing ipsilateral paralysis of the soft palate, pharynx, and larynx, leading to dysphagia and hoarseness.

Medullary Syndromes - When Things Go Wrong

Medullary Syndromes & Vascular Territories

Damage to medullary nuclei from vascular occlusion presents with distinct clinical syndromes based on the artery affected.

Feature	Medial Medullary Syndrome	Lateral Medullary (Wallenberg) Syndrome
Vessel	Anterior Spinal Artery (ASA)	Posterior Inferior Cerebellar Artery (PICA)
Tracts	* Corticospinal Tract * Medial Lemniscus * Hypoglossal Nucleus (CN XII)	* Spinothalamic Tract * Spinal Trigeminal Nucleus (CN V) * Nucleus Ambiguus (CN IX, X) * Vestibular Nuclei * Sympathetic Fibers
Signs	* Contralateral paralysis * ↓ Contralateral proprioception * Ipsilateral tongue deviation	* ↓ Contralateral body pain/temp * ↓ Ipsilateral face pain/temp * Hoarseness, dysphagia * Vertigo, nystagmus * Ipsilateral Horner's Syndrome

⭐ Exam Favorite: The presence of dysphagia, hoarseness, and a diminished gag reflex is highly specific for Lateral Medullary Syndrome, pointing directly to damage to the Nucleus Ambiguus.

High‑Yield Points - ⚡ Biggest Takeaways

The medulla contains the nuclei for the last four cranial nerves: CN IX, X, XI, and XII.

Nucleus ambiguus (CN IX, X) provides motor control to the pharynx and larynx; lesions result in hoarseness and dysphagia.

Nucleus solitarius is the primary center for visceral sensory information, including taste and baroreceptor inputs.

The hypoglossal nucleus controls tongue movement; a lesion causes the tongue to deviate toward the injured side.

The inferior olivary nucleus is crucial for motor learning and coordination.

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