Brainstem nuclei Practice Questions

Q: A 67-year-old man with a history of atrial fibrillation presents with sudden onset of right-sided facial droop involving the forehead, inability to conjugately gaze to the right, and left-sided hemiplegia sparing the face. His pupils are equal and reactive. An MRI is obtained. At which axial level and side does the lesion most likely reside?

Right caudal pons. ***Right caudal pons*** - This patient presents with **Foville syndrome**, which involves the **right facial nerve nucleus** (ipsilateral facial droop including forehead) and the **right PPRF or abducens nucleus** (ipsilateral conjugate gaze palsy). - The **contralateral (left) hemiplegia** is caused by damage to the **corticospinal tract** before it decussates in the medulla, localizing the lesion to the **right side** of the brainstem at the **caudal pontine** level. *Left caudal pons* - A lesion on the left side would cause an **ipsilateral (left) facial droop** and a **left-sided conjugate gaze palsy**, which contradicts the clinical presentation. - Left-sided damage at this level would result in **right-sided hemiplegia** because the corticospinal fibers descend to the right side of the body after leaving the left pons. *Left rostral medulla* - Medullary lesions typically present with **hypoglossal nerve (CN XII)** palsy (tongue deviation) or **Wallenberg syndrome** features, rather than gaze or facial nerve palsies. - Lesions at the medulla level would not explain the **horizontal gaze palsy**, which is localized to the **PPRF/CN VI** in the pons. *Right rostral medulla* - A rostral medullary lesion would not involve the **CN VI nucleus** or **CN VII nucleus**, as these are located more superiorly within the **pons**. - Medullary involvement would more likely cause **lower cranial nerve** deficits such as **dysphagia** or **hoarseness** (CN IX, X) rather than facial droop. *Left midbrain tegmentum* - Midbrain lesions typically involve the **oculomotor nerve (CN III)**, resulting in **ptosis** and a "down and out" pupil, which are absent here. - A midbrain lesion would not involve the **CN VII nucleus**, which is required to explain the **forehead-involving** facial paralysis seen in this patient.

Q: An 86-year-old woman is brought to the emergency department by her niece because the patient felt like she was spinning and about to topple over. This occurred around 4 hours ago, and although symptoms have improved, she still feels like she is being pulled to the right side. The vital signs include: blood pressure 116/75 mm Hg, pulse 90/min, and SpO2 99% on room air. Physical examination reveals right-sided limb ataxia along with hypoalgesia and decreased temperature sensation on the right side of the face and left side of the body. An urgent non-contrast CT scan of the head shows no evidence of hemorrhage. What other finding is most likely to be present in this patient?

Absent gag reflex. ***Absent gag reflex*** - The constellation of **vertigo**, **right-sided ataxia**, and **crossed sensory loss** (right face, left body) is characteristic of **Wallenberg syndrome** (lateral medullary infarction). - This syndrome often involves the **nucleus ambiguus**, which controls the muscles of the **soft palate, pharynx, and larynx**, leading to an absent gag reflex, dysphagia, and hoarseness. *Hemiparesis* - **Hemiparesis** (weakness on one side of the body) is typically associated with lesions in the **corticospinal tracts** higher up in the brainstem or cerebral hemispheres. - While stroke can cause hemiparesis, it is not a primary feature of Lateral Medullary Syndrome, which predominantly affects sensory and cerebellar pathways. *Deviated tongue* - **Tongue deviation** is seen with lesions of the **hypoglossal nerve (CN XII)** or its nucleus, which would typically cause the tongue to deviate towards the side of the lesion when protruded. - Wallenberg syndrome primarily affects structures supplied by the **posterior inferior cerebellar artery (PICA)**, and the hypoglossal nucleus is usually spared. *Hemianopia* - **Hemianopia** (loss of half of the visual field) results from damage to the **optic tracts**, optic radiations, or the visual cortex in the occipital lobe. - Lateral medullary infarction primarily affects the brainstem and cerebellum, far from the visual pathways responsible for hemianopia. *Absent cough reflex* - While dysphagia and an absent gag reflex are common in Wallenberg syndrome due to involvement of the nucleus ambiguus, an entirely **absent cough reflex** is a more severe indicator of brainstem dysfunction. - The cough reflex is complex and involves cranial nerves IX, X, and the respiratory centers; while it can be impaired, an absent gag reflex is more specifically linked to the **nucleus ambiguus** lesion in this syndrome.

Q: A 60-year-old woman presents with progressive difficulty swallowing solid foods for the past 2 months. She also says her voice has gradually changed, and she has had recent episodes of vertigo associated with nausea and vomiting and oscillating eye movements while reading. She denies any problems with the movement of her face or extremities. Past medical history is significant for hypertension, managed with enalapril, and dyslipidemia, which she is managing with dietary modifications. The patient reports a 40-pack-year smoking history. Vital signs are within normal limits. On physical examination, there is decreased pain and temperature sensation on the right side of her body, and she cannot touch her nose with her eyes closed. Which of the following is the most likely site of vascular occlusion in this patient?

Posterior inferior cerebellar artery. ***Correct: Posterior inferior cerebellar artery*** - This presentation is classic for **Wallenberg syndrome (lateral medullary syndrome)**, which is most commonly caused by occlusion of the **posterior inferior cerebellar artery (PICA)**. - Key symptoms like **dysphagia**, **hoarseness (nucleus ambiguus involvement)**, **vertigo, nausea, vomiting, nystagmus (vestibular nuclei)**, **ipsilateral ataxia (inferior cerebellar peduncle/cerebellum)**, and **contralateral pain and temperature loss (spinothalamic tract)** are all present. *Incorrect: Anterior cerebral artery* - Occlusion of the anterior cerebral artery typically causes **contralateral leg weakness and sensory loss**, with **gait dysfunction** and **behavioral changes**. - It does not explain the **brainstem symptoms** like dysphagia, vertigo, or ataxia. *Incorrect: Anterior inferior cerebellar artery* - An **anterior inferior cerebellar artery (AICA) stroke** would present with symptoms of lateral pontine syndrome, including **ipsilateral facial weakness and sensory loss**, **tinnitus and hearing loss**, and **ataxia**. - While some vestibular symptoms can occur, the prominent **dysphagia and hoarseness** point more strongly to medullary involvement. *Incorrect: Middle cerebral artery* - A **middle cerebral artery (MCA) stroke** typically results in **contralateral hemiparesis**, **hemianesthesia**, and possibly **aphasia** (if dominant hemisphere affected) or **hemineglect** (if non-dominant hemisphere affected). - This does not account for the brainstem signs observed in the patient. *Incorrect: Anterior spinal artery* - Occlusion of the **anterior spinal artery** primarily affects the spinal cord, causing **bilateral motor weakness, bilateral loss of pain and temperature sensation below the lesion**, and **bladder dysfunction**. - It does not cause the cerebellar, vestibular, or bulbar symptoms seen in this patient.

Question 1

A 67-year-old man with a history of atrial fibrillation presents with sudden onset of right-sided facial droop involving the forehead, inability to conjugately gaze to the right, and left-sided hemiplegia sparing the face. His pupils are equal and reactive. An MRI is obtained. At which axial level and side does the lesion most likely reside?

Accepted Answer

Right caudal pons

Answer

Left caudal pons

Answer

Left rostral medulla

Answer

Right rostral medulla

Answer

Left midbrain tegmentum

Question 2

A 32-year-old woman at 28 weeks of gestation undergoes a fetal echocardiogram that reveals the aorta arising from the morphological right ventricle and the pulmonary trunk arising from the morphological left ventricle. The great vessels run parallel rather than in their normal spiral relationship. The embryological error most directly responsible for this anomaly occurred during which developmental process?

Accepted Answer

Failure of the aorticopulmonary septum to spiral as it partitions the truncus arteriosus

Answer

Incomplete fusion of the endocardial cushions within the atrioventricular canal

Answer

Failure of neural crest cells to migrate into the outflow tract to initiate conotruncal septation

Answer

Abnormal rightward looping of the primitive heart tube during Carnegie stage 10

Answer

Premature closure of the foramen secundum before birth

Question 3

An 86-year-old woman is brought to the emergency department by her niece because the patient felt like she was spinning and about to topple over. This occurred around 4 hours ago, and although symptoms have improved, she still feels like she is being pulled to the right side. The vital signs include: blood pressure 116/75 mm Hg, pulse 90/min, and SpO2 99% on room air. Physical examination reveals right-sided limb ataxia along with hypoalgesia and decreased temperature sensation on the right side of the face and left side of the body. An urgent non-contrast CT scan of the head shows no evidence of hemorrhage. What other finding is most likely to be present in this patient?

Accepted Answer

Absent gag reflex

Answer

Hemiparesis

Answer

Deviated tongue

Answer

Hemianopia

Answer

Absent cough reflex

Question 4

A 60-year-old woman presents with progressive difficulty swallowing solid foods for the past 2 months. She also says her voice has gradually changed, and she has had recent episodes of vertigo associated with nausea and vomiting and oscillating eye movements while reading. She denies any problems with the movement of her face or extremities. Past medical history is significant for hypertension, managed with enalapril, and dyslipidemia, which she is managing with dietary modifications. The patient reports a 40-pack-year smoking history. Vital signs are within normal limits. On physical examination, there is decreased pain and temperature sensation on the right side of her body, and she cannot touch her nose with her eyes closed. Which of the following is the most likely site of vascular occlusion in this patient?

Accepted Answer

Posterior inferior cerebellar artery

Answer

Anterior cerebral artery

Answer

Anterior inferior cerebellar artery

Answer

Middle cerebral artery

Answer

Anterior spinal artery

Question 5

A 59-year-old woman with a past medical history of atrial fibrillation currently on warfarin presents to the emergency department for acute onset dizziness. She was watching TV in the living room when she suddenly felt the room spin around her as she was getting up to go to the bathroom. She denies any fever, weight loss, chest pain, palpitations, shortness of breath, lightheadedness, or pain but reports difficulty walking and hiccups. A physical examination is significant for rotary nystagmus and decreased pin prick sensation on the left side of her body. A magnetic resonance image (MRI) of the head is obtained and shows ischemic changes of the right lateral medulla. What other symptoms would you expect to find in this patient?

Accepted Answer

Decreased gag reflex

Answer

Left-sided tongue deviation

Answer

Language impairment

Answer

Paralysis of the right lower limb

Answer

Right-sided facial paralysis

Brainstem nuclei — MCQs

Brainstem nuclei — MCQs

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