Pontine nuclei US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Pontine nuclei. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Pontine nuclei US Medical PG Question 1: A 45-year-old patient presents with difficulty speaking and swallowing following a stroke. MRI reveals an infarct in the medulla. Which of the following cranial nerve nuclei is most likely affected?
- A. Vestibulocochlear nucleus
- B. Trigeminal nerve nucleus
- C. Facial nerve nucleus
- D. Nucleus ambiguus (Correct Answer)
Pontine nuclei Explanation: ***Nucleus ambiguus***
- The **nucleus ambiguus** is located in the **medulla** and contains motor neurons that innervate muscles involved in **speaking** and **swallowing**, specifically those of the pharynx, larynx, and soft palate via cranial nerves IX, X, and XI [1].
- An infarct in the medulla causing difficulty speaking and swallowing strongly implicates damage to this nucleus, leading to **dysarthria** and **dysphagia** [1].
*Vestibulocochlear nucleus*
- This nucleus is primarily involved in **hearing** and **balance**, which would manifest as dizziness, hearing loss, or nystagmus, not directly difficulty speaking and swallowing.
- While located in the brainstem, damage to this nucleus typically does not cause the specific symptoms of dysarthria and dysphagia described.
*Trigeminal nerve nucleus*
- The trigeminal nerve is responsible for sensory innervation of the face, and motor innervation for **mastication** (chewing).
- Damage would primarily affect facial sensation or jaw movement, not the act of deglutition or phonation.
*Facial nerve nucleus*
- This nucleus, located in the **pons**, controls the muscles of **facial expression** and taste for the anterior two-thirds of the tongue.
- Damage would lead to facial weakness or paralysis, not the profound difficulty with speaking and swallowing affecting pharyngeal and laryngeal function.
Pontine nuclei US Medical PG Question 2: A 72-year-old woman is brought in to the emergency department after her husband noticed that she appeared to be choking on her dinner. He performed a Heimlich maneuver but was concerned that she may have aspirated something. The patient reports a lack of pain and temperature on the right half of her face, as well as the same lack of sensation on the left side of her body. She also states that she has been feeling "unsteady" on her feet. On physical exam you note a slight ptosis on the right side. She is sent for an emergent head CT. Where is the most likely location of the neurological lesion?
- A. Pons
- B. Internal capsule
- C. Cervical spinal cord
- D. Medulla (Correct Answer)
- E. Midbrain
Pontine nuclei Explanation: ***Medulla***
- This presentation describes **Wallenberg syndrome** (lateral medullary syndrome), characterized by **ipsilateral facial sensory loss**, **contralateral body sensory loss**, and **ataxia** due to involvement of the spinothalamic tracts, trigeminal nucleus, and cerebellar pathways.
- **Dysphagia** (choking) and **Horner's syndrome** (ptosis, miosis, anhidrosis) are also classic signs, specifically the ptosis seen here, pointing to an infarct in the **lateral medulla**.
*Pons*
- Lesions in the pons typically present with varying degrees of **cranial nerve deficits** (e.g., trigeminal, abducens, facial) and **motor or sensory deficits** affecting both sides of the body due to the decussation of tracts.
- The specific combination of **crossed sensory loss** and other symptoms seen here is not characteristic of isolated pontine lesions.
*Internal capsule*
- A lesion in the internal capsule would primarily cause **contralateral motor weakness (hemiparesis)** and **sensory loss** affecting both the face and body on the same side, without the ipsilateral facial involvement.
- It would not explain the **ataxia** or specific cranial nerve signs like ptosis.
*Cervical spinal cord*
- Spinal cord lesions result in **sensory and motor deficits below the level of the lesion**, affecting both sides of the body symmetrically, or ipsilaterally depending on the tract involved.
- They do not cause **facial sensory disturbances**, **dysphagia**, or **ataxia** in the manner described.
*Midbrain*
- Midbrain lesions typically involve the **oculomotor nerve** (CN III), causing eye movement abnormalities, and can result in **contralateral hemiparesis**.
- They do not produce the **crossed sensory deficits** (ipsilateral face, contralateral body) or **ataxia** characteristic of this case.
Pontine nuclei US Medical PG Question 3: A 27-year-old man is brought into the emergency department by ambulance. The patient was at an appointment to receive welfare when he began acting abnormally. The patient was denied welfare. Shortly afterwards, he no longer responded to questions and stared blankly off into space, not responding to verbal stimuli. Other than odd lip-smacking behavior, he was motionless. Several minutes later, he became responsive but seemed confused. The patient has a past medical history of drug abuse and homelessness and is not currently taking any medications. His temperature is 98.9°F (37.2°C), blood pressure is 124/78 mmHg, pulse is 90/min, respirations are 14/min, and oxygen saturation is 99% on room air. Physical exam reveals cranial nerves II-XII as grossly intact with 5/5 strength in the upper and lower extremities and a stable gait. The patient seems confused when answering questions and has trouble remembering the episode. Which of the following is the most likely diagnosis?
- A. Absence seizure
- B. Malingering
- C. Focal impaired awareness seizure (Correct Answer)
- D. Transient ischemic attack
- E. Generalized seizure
Pontine nuclei Explanation: ***Focal impaired awareness seizure***
- The patient's presentation with a period of **unresponsiveness**, **staring blankly**, repetitive **lip-smacking automatisms**, and subsequent **postictal confusion** and **amnesia of the event** are highly characteristic of a focal impaired awareness seizure (formerly called complex partial seizure).
- This seizure type originates from a **focal area of the brain** (often temporal lobe) and involves **impaired consciousness** during the episode.
- The context of significant stress (welfare denial) can sometimes precipitate seizures in susceptible individuals, although it is not a direct cause.
- **Automatisms** (repetitive purposeless movements like lip-smacking) are a hallmark feature.
*Absence seizure*
- Absence seizures are typically **brief (seconds)**, characterized by a sudden **cessation of activity and blank stares**, without automatisms like lip-smacking.
- Patients usually have **no postictal confusion** or memory loss of the event, which contradicts this patient's presentation.
- More common in **children** rather than adults.
*Malingering*
- Malingering involves the **intentional feigning of symptoms** for secondary gain, but the presence of automatisms like lip-smacking and the postictal state are objective neurological signs not easily faked.
- The lack of responsiveness to verbal stimuli and subsequent confusion are clinical features inconsistent with volitional control.
*Transient ischemic attack*
- TIAs present with **focal neurological deficits** (e.g., weakness, speech disturbance, visual loss) that resolve completely within 24 hours, often without confusion.
- The symptoms described (staring, lip-smacking, generalized unresponsiveness, and confusion) are not typical of a TIA.
- More common in **older patients** with vascular risk factors.
*Generalized seizure*
- A generalized seizure, such as a tonic-clonic seizure, would involve **loss of consciousness** with **tonic and clonic movements** of the extremities, which are not described here.
- While postictal confusion is common, the focal automatisms and lack of widespread motor activity point away from a primary generalized seizure.
- Generalized seizures involve **both hemispheres** from onset, unlike this focal presentation.
Pontine nuclei US Medical PG Question 4: A 57-year-old woman is brought to the emergency department by her husband with complaints of sudden-onset slurring for the past hour. She is also having difficulty holding things with her right hand. She denies fever, head trauma, diplopia, vertigo, walking difficulties, nausea, and vomiting. Past medical history is significant for type 2 diabetes mellitus, hypertension, and hypercholesterolemia for which she takes a baby aspirin, metformin, ramipril, and simvastatin. She has a 23-pack-year cigarette smoking history. Her blood pressure is 148/96 mm Hg, the heart rate is 84/min, and the temperature is 37.1°C (98.8°F). On physical examination, extraocular movements are intact. The patient is dysarthric, but her higher mental functions are intact. There is a right-sided facial weakness with preserved forehead wrinkling. Her gag reflex is weak. Muscle strength is mildly reduced in the right hand. She has difficulty performing skilled movements with her right hand, especially writing, and has difficulty touching far objects with her index finger. She is able to walk without difficulty. Pinprick and proprioception sensation is intact. A head CT scan is within normal limits. What is the most likely diagnosis?
- A. Locked in syndrome
- B. Pure motor syndrome
- C. Parinaud’s syndrome
- D. Dysarthria-clumsy hand syndrome (Correct Answer)
- E. Lateral medullary syndrome
Pontine nuclei Explanation: ***Dysarthria-clumsy hand syndrome***
- This syndrome is characterized by **dysarthria**, **facial weakness**, and **clumsiness of the hand** (especially with fine motor movements), often affecting the contralateral side to the lesion.
- The patient's presentation with slurred speech (dysarthria), mild right-hand weakness, difficulty with skilled movements, and preserved forehead wrinkling (indicating an upper motor neuron lesion in the facial nerve distribution) is highly consistent and points to a **lacunar stroke** typically affecting the pons or internal capsule.
*Locked-in syndrome*
- This severe condition involves **complete paralysis** of nearly all voluntary muscles except for vertical eye movements and blinking, which is not described here.
- Patients are fully conscious but unable to communicate verbally or with body movements, a much more extensive deficit than presented.
*Pure motor syndrome*
- This syndrome primarily involves **weakness** without significant sensory, cerebellar, or cranial nerve involvement.
- While the patient has motor symptoms, the presence of **dysarthria** and **facial weakness** suggests more than just pure motor deficits of the limbs, differentiating it from pure motor hemiparesis.
*Parinaud’s syndrome*
- This syndrome, resulting from a lesion in the **dorsal midbrain**, presents with **vertical gaze palsy**, pupillary abnormalities, and lid retraction (Collier's sign).
- The patient's intact extraocular movements and lack of these specific eye signs rule out Parinaud's syndrome.
*Lateral medullary syndrome*
- Also known as **Wallenberg's syndrome**, it results from an infarct of the lateral medulla and is characterized by a constellation of symptoms including **vertigo**, nystagmus, ipsilateral facial numbness, contralateral body numbness, and ataxia.
- The patient explicitly denies vertigo and walking difficulties, and her sensory examination is intact, making lateral medullary syndrome unlikely.
Pontine nuclei US Medical PG Question 5: Where does the only cranial nerve without a thalamic relay nucleus enter the skull?
- A. Superior orbital fissure
- B. Internal auditory meatus
- C. Foramen rotundum
- D. Jugular foramen
- E. Cribriform plate (Correct Answer)
Pontine nuclei Explanation: ***Cribriform plate***
- The **olfactory nerve (CN I)** is the only cranial nerve that does not have a thalamic relay nucleus before reaching the cerebral cortex.
- It passes through the **cribriform plate** of the ethmoid bone to reach the olfactory bulbs.
*Superior orbital fissure*
- This opening transmits the **oculomotor (CN III), trochlear (CN IV), ophthalmic division of trigeminal (CN V1)**, and **abducens (CN VI)** nerves.
- These nerves all have sensory or motor components that relay through the thalamus, directly or indirectly.
*Internal auditory meatus*
- This canal transmits the **facial (CN VII)** and **vestibulocochlear (CN VIII)** nerves.
- The vestibulocochlear nerve's auditory pathway involves a thalamic relay in the **medial geniculate nucleus**.
*Foramen rotundum*
- The **maxillary division of the trigeminal nerve (CN V2)** passes through the foramen rotundum.
- Sensory information carried by CN V2 relays through the **thalamus**.
*Jugular foramen*
- This opening transmits the **glossopharyngeal (CN IX), vagus (CN X)**, and **accessory (CN XI)** nerves.
- Sensory components of these nerves, particularly taste and visceral sensation, involve thalamic nuclei.
Pontine nuclei US Medical PG Question 6: A man appearing to be in his mid-50s is brought in by ambulance after he was seen walking on railroad tracks. On further questioning, the patient does not recall being on railroad tracks and is only able to provide his name. Later on, he states that he is a railroad worker, but this is known to be false. On exam, his temperature is 99.9°F (37.7°C), blood pressure is 128/86 mmHg, pulse is 82/min, and respirations are 14/min. He appears disheveled, and his clothes smell of alcohol. The patient is alert, is only oriented to person, and is found to have abnormal eye movements and imbalanced gait when attempting to walk. Which of the following structures in the brain likely has the greatest reduction in the number of neurons?
- A. Mammillary bodies (Correct Answer)
- B. Cerebellar vermis
- C. Parietal-temporal cortex
- D. Frontal eye fields
- E. Basal ganglia
Pontine nuclei Explanation: ***Mammillary bodies***
- This patient presents with symptoms highly suggestive of **Wernicke-Korsakoff syndrome**, which includes **ophthalmoplegia** (abnormal eye movements), **ataxia** (imbalanced gait), and **confabulation** (making up stories, like being a railroad worker) with **anterograde amnesia** (not recalling being on railroad tracks).
- Wernicke-Korsakoff syndrome is primarily caused by **thiamine (vitamin B1) deficiency**, commonly seen in **chronic alcoholics**, and results in neuronal loss and necrosis, especially in the **mammillary bodies** and dorsomedial nucleus of the thalamus.
*Cerebellar vermis*
- While **alcoholism** can lead to cerebellar damage, particularly the **vermis**, causing **ataxia**, it does not fully explain the **memory deficits, confabulation, and ophthalmoplegia** seen in Wernicke-Korsakoff syndrome.
- Damage to the cerebellar vermis would primarily result in truncal ataxia and gait instability without the prominent amnesia and confabulation.
*Parietal-temporal cortex*
- Damage to the **parietal-temporal cortex** is associated with various cognitive deficits, including **aphasias** and **agnosias**, depending on the specific areas affected.
- While it can be affected by chronic alcoholism, it is not the primary site of damage in **Wernicke-Korsakoff syndrome** and does not typically present with the classic triad.
*Frontal eye fields*
- The **frontal eye fields** are involved in controlling **voluntary eye movements** and saccades. Damage here can cause specific patterns of gaze palsies.
- However, the abnormal eye movements seen in Wernicke-Korsakoff syndrome (e.g., nystagmus, ophthalmoplegia) are typically due to damage in brainstem nuclei and **mammillary bodies**, not primarily the frontal eye fields.
*Basal ganglia*
- The **basal ganglia** are primarily involved in motor control, learning, and executive functions. Damage to these structures can lead to **movement disorders** like Parkinsonism or Huntington's disease.
- While chronic alcoholism can have diffuse effects on the brain, the basal ganglia are not the primary site of pathology in **Wernicke-Korsakoff syndrome**, and damage here would not explain the memory and confabulation symptoms.
Pontine nuclei US Medical PG Question 7: A 75-year-old man is brought to the emergency room after being found unresponsive in his home. His medical history is unknown. On physical examination he does not demonstrate any spontaneous movement of his extremities and is unable to respond to voice or painful stimuli. You notice that he is able blink and move his eyes in the vertical plane. Based on these physical exam findings, you expect that magnetic resonance angiogram will most likely reveal an occlusion in which of the following vessels?
- A. Basilar artery (Correct Answer)
- B. Anterior cerebral artery
- C. Anterior spinal artery
- D. Posterior cerebral artery
- E. Anterior inferior cerebellar artery
Pontine nuclei Explanation: ***Basilar artery***
- The patient's presentation with **quadriplegia**, inability to respond to stimuli, and preserved **vertical eye movements** and blinking is characteristic of **locked-in syndrome**.
- **Locked-in syndrome** is most commonly caused by an **occlusion of the basilar artery**, leading to infarction of the ventral pons while sparing the tegmentum.
*Anterior cerebral artery*
- Occlusion of the **anterior cerebral artery** typically causes **contralateral leg weakness** and sensory loss, and sometimes **abulia** or urinary incontinence.
- It does not explain the widespread motor paralysis affecting all four limbs or the preservation of vertical eye movements in an otherwise unresponsive patient.
*Anterior spinal artery*
- Occlusion of the **anterior spinal artery** causes an **anterior spinal cord syndrome**, characterized by bilateral weakness and loss of pain/temperature sensation below the lesion, with preserved proprioception and vibration sense.
- This presentation does not include the characteristic signs of **brainstem dysfunction** seen in locked-in syndrome.
*Posterior cerebral artery*
- An occlusion in the **posterior cerebral artery** typically leads to **contralateral homonymous hemianopia**, and depending on the branch occluded, can also cause memory deficits or thalamic pain.
- It does not account for the extensive motor paralysis or the pattern of preserved vertical eye movements seen in locked-in syndrome.
*Anterior inferior cerebellar artery*
- Occlusion of the **anterior inferior cerebellar artery (AICA)** typically results in **lateral pontine syndrome**, which includes ipsilateral facial weakness, hearing loss, cerebellar ataxia, and contralateral loss of pain and temperature sensation.
- While it affects the pons, AICA occlusion does not typically cause the complete quadriplegia and preservation of vertical eye movements characteristic of locked-in syndrome.
Pontine nuclei US Medical PG Question 8: A 26-year-old man is brought to the emergency department by ambulance after being involved in a motor vehicle collision. He does not open his eyes on command or respond to verbal cues. A CT scan of the head shows a hyperdense fluid collection in the right medial temporal lobe with medial displacement of the uncus and parahippocampal gyrus of the temporal lobe. Which of the following cranial nerves is most likely to be injured as a result of this patient's lesion?
- A. Vagus
- B. Facial
- C. Oculomotor (Correct Answer)
- D. Abducens
- E. Trigeminal
Pontine nuclei Explanation: ***Oculomotor***
- The description of **medial displacement of the uncus and parahippocampal gyrus** (uncus herniation) compresses the **oculomotor nerve (CN III)** as it passes between the posterior cerebral and superior cerebellar arteries.
- Compression of the oculomotor nerve leads to a **dilated pupil** (due to parasympathetic fiber involvement) and **down-and-out deviation of the eye** (due to paralysis of extraocular muscles it innervates).
*Vagus*
- The vagus nerve (CN X) is deep within the skull and brainstem, far from the temporal lobe, and is not directly affected by uncal herniation.
- Injury to the vagus nerve typically presents with dysphagia, hoarseness, or cardiac arrhythmias, symptoms not indicated here.
*Facial*
- The facial nerve (CN VII) exits the brainstem at the pontomedullary junction and is located more superiorly and laterally than the structures involved in uncal herniation.
- Damage to the facial nerve causes facial muscle weakness or paralysis, which is not the primary concern with uncal herniation.
*Abducens*
- The abducens nerve (CN VI) is a long, slender nerve that can be affected by **generalized increases in intracranial pressure**, but is less commonly directly compressed by an uncal herniation itself.
- Injury to the abducens nerve causes **lateral rectus muscle paralysis**, leading to medial deviation of the eye, whereas uncal herniation typically affects the oculomotor nerve.
*Trigeminal*
- The trigeminal nerve (CN V) exits the pons and is located superior to the tentorial notch and medial temporal lobe, making it unlikely to be directly compressed by uncal herniation.
- Injury to the trigeminal nerve causes sensory loss in the face or weakness of the muscles of mastication, which are not consistent with the described lesion.
Pontine nuclei US Medical PG Question 9: 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?
- A. Hemiparesis
- B. Deviated tongue
- C. Hemianopia
- D. Absent cough reflex
- E. Absent gag reflex (Correct Answer)
Pontine nuclei Explanation: ***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.
Pontine nuclei US Medical PG Question 10: 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?
- A. Anterior cerebral artery
- B. Anterior inferior cerebellar artery
- C. Posterior inferior cerebellar artery (Correct Answer)
- D. Middle cerebral artery
- E. Anterior spinal artery
Pontine nuclei Explanation: ***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.
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