Limbic system US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Limbic system. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Limbic system US Medical PG Question 1: A 78-year-old woman is brought to the physician by her son because of progressive memory loss for the past year. She feels tired and can no longer concentrate on her morning crossword puzzles. She has gained 11.3 kg (25 lb) in the last year. Her father died from complications of Alzheimer disease. She has a history of drinking alcohol excessively but has not consumed alcohol for the past 10 years. Vital signs are within normal limits. She is oriented but has short-term memory deficits. Examination shows a normal gait and delayed relaxation of the achilles reflex bilaterally. Her skin is dry and she has brittle nails. Which of the following is the most likely underlying etiology of this woman’s memory loss?
- A. Thiamine deficiency
- B. Autoimmune thyroid disease (Correct Answer)
- C. Alzheimer disease
- D. Vitamin B12 deficiency
- E. Normal pressure hydrocephalus
Limbic system Explanation: ***Autoimmune thyroid disease***
- The patient exhibits classic symptoms of **hypothyroidism**, including **fatigue**, **difficulty concentrating**, **weight gain**, **dry skin**, **brittle nails**, and **delayed relaxation of the Achilles reflex**.
- **Hypothyroidism** can lead to cognitive impairment, including memory loss, which may be reversible with treatment.
*Thiamine deficiency*
- While thiamine deficiency can cause memory loss (Wernicke-Korsakoff syndrome), it typically presents with **ataxia**, **ophthalmoplegia**, and severe global amnesia, often in the context of active alcohol abuse.
- The patient's **alcohol consumption** ceased 10 years ago, and she does not exhibit other characteristic symptoms of Wernicke-Korsakoff syndrome.
*Alzheimer disease*
- Although the patient's father had Alzheimer disease and she has progressive memory loss, her additional symptoms like **weight gain**, **fatigue**, **dry skin**, **brittle nails**, and **delayed reflexes** are not typical for Alzheimer disease.
- While Alzheimer's cannot be entirely ruled out, the constellation of symptoms points strongly towards a more immediately treatable cause.
*Vitamin B12 deficiency*
- Vitamin B12 deficiency can cause **memory loss**, **fatigue**, and neurologic symptoms, but it is not typically associated with **weight gain**, **dry skin**, **brittle nails**, or **delayed deep tendon reflexes**.
- Neurologic symptoms often include **peripheral neuropathy** and **paresthesias**.
*Normal pressure hydrocephalus*
- **Normal pressure hydrocephalus (NPH)** is characterized by the triad of **gait disturbance**, **urinary incontinence**, and **dementia**.
- While the patient has memory loss, her gait is described as normal, and there is no mention of urinary incontinence, making NPH less likely.
Limbic system US Medical PG Question 2: A 62-year-old man is brought to the emergency department because of headache, blurring of vision, and numbness of the right leg for the past 2 hours. He has hypertension and type 2 diabetes mellitus. Current medications include enalapril and metformin. He is oriented only to person. His temperature is 37.3°C (99.1°F), pulse is 99/min and blood pressure is 158/94 mm Hg. Examination shows equal pupils that are reactive to light. Muscle strength is normal in all extremities. Deep tendon reflexes are 2+ bilaterally. Sensation to fine touch and position is decreased over the right lower extremity. The confrontation test shows loss of the nasal field in the left eye and the temporal field in the right eye with macular sparing. He is unable to read phrases shown to him but can write them when they are dictated to him. He has short-term memory deficits. Which of the following is the most likely cause for this patient's symptoms?
- A. Infarct of the right middle cerebral artery
- B. Infarct of the right anterior cerebral artery
- C. Infarct of the right posterior cerebral artery
- D. Herpes simplex encephalitis
- E. Infarct of the left posterior cerebral artery (Correct Answer)
Limbic system Explanation: ***Infarct of the left posterior cerebral artery***
- The patient's inability to read but ability to write when dictated, known as **alexia without agraphia**, is a classic sign of an infarct in the **left posterior cerebral artery (PCA)** affecting the **splenium of the corpus callosum** and the **left visual cortex**.
- The **right homonymous hemianopsia** with **macular sparing** (loss of the nasal field in the left eye and the temporal field in the right eye) is also characteristic of a left PCA infarct due to involvement of the optic radiations or primary visual cortex, with macular sparing often observed.
*Infarct of the right middle cerebral artery*
- A right MCA infarct would typically present with **left-sided motor and sensory deficits**, **left homonymous hemianopsia**, and **neglect** of the left side, which do not align with the patient's specific presentation of alexia without agraphia and right homonymous hemianopsia.
*Infarct of the right anterior cerebral artery*
- A right ACA infarct would primarily cause **left-sided lower extremity weakness** and **sensory loss**, often affecting the **frontal lobe** with behavioral changes.
- It would not explain the visual field deficits or alexia without agraphia seen in this patient.
*Infarct of the right posterior cerebral artery*
- A right PCA infarct would cause **left homonymous hemianopsia** with or without macular sparing, but would not produce alexia without agraphia, which is a specific **language processing deficit** localized to the dominant (left) hemisphere.
- It could lead to visual agnosia or prosopagnosia, but not the specific reading-writing dissociation observed.
*Herpes simplex encephalitis*
- Herpes simplex encephalitis typically presents with **fever**, **headache**, **seizures**, and **altered mental status**, often with **focal neurological deficits** affecting the **temporal** and **frontal lobes**.
- While it can cause memory deficits and altered mental status, it would not typically present with the acute, specific combination of alexia without agraphia and distinct visual field deficits of vascular origin.
Limbic system US Medical PG Question 3: A 52-year-man is brought to the physician because of a 2-week history of memory loss. Three weeks ago, he had a cardiac arrest that required cardiopulmonary resuscitation and intravenous epinephrine. On mental status examination, he cannot recall objects shown to him 20 minutes earlier but vividly recalls memories from before the incident. The remainder of the examination shows no abnormalities. Which of the following structures of the brain is most likely affected?
- A. Internal pyramidal layer of the amygdala
- B. Microglial cells of dorsal midbrain
- C. Purkinje cells of the cerebellum
- D. Pyramidal cells of the hippocampus (Correct Answer)
- E. Astroglial cells of the putamen
Limbic system Explanation: ***Pyramidal cells of the hippocampus***
- The patient's inability to form new memories (anterograde amnesia) following a period of **hypoxia** suggests damage to the **hippocampus**, specifically its pyramidal cells.
- The **hippocampus** is highly vulnerable to **ischemic injury** due to the metabolic demands of its pyramidal cells.
*Internal pyramidal layer of the amygdala*
- The amygdala is primarily involved in **emotional processing**, particularly fear and anxiety, not memory encoding directly.
- Damage to the amygdala would likely manifest as altered emotional responses, rather than isolated memory loss.
*Microglial cells of dorsal midbrain*
- Microglial cells are the brain's resident immune cells and proliferate in response to injury, they are not the primary site of memory formation.
- The dorsal midbrain contains structures involved in visual and auditory reflexes, not directly memory consolidation.
*Purkinje cells of the cerebellum*
- Purkinje cells are specialized neurons in the **cerebellum** responsible for **motor coordination** and balance.
- Damage to these cells would result in ataxia and motor dysfunction, not memory deficits.
*Astroglial cells of the putamen*
- Astroglial cells are supportive cells throughout the brain; the putamen is involved in **motor control** and **procedural learning**.
- Dysfunction of the putamen typically leads to movement disorders like Parkinsonism, not specific memory loss.
Limbic system US Medical PG Question 4: A neurology resident sees a stroke patient on the wards. This 57-year-old man presented to the emergency department after sudden paralysis of his right side. He was started on tissue plasminogen activator within 4 hours, as his wife noticed the symptoms and immediately called 911. When the resident asks the patient how he is doing, he replies by saying that his apartment is on Main St. He does not seem to appropriately answer the questions being asked, but rather speaks off topic. He is able to repeat the word "fan." His consciousness is intact, and his muscle tone and reflexes are normal. Upon striking the lateral part of his sole, his big toe extends upward and the other toes fan out. Which of the following is the area most likely affected in his condition?
- A. Caudate nucleus
- B. Broca’s area
- C. Arcuate fasciculus
- D. Temporal lobe (Correct Answer)
- E. Cuneus gyrus
Limbic system Explanation: ***Temporal lobe***
- The patient exhibits features of **Wernicke's aphasia**, characterized by **fluent but nonsensical speech** ("apartment is on Main St." when asked how he is), poor comprehension, and the ability to repeat words. **Wernicke's area**, responsible for language comprehension, is located in the **posterior part of the superior temporal gyrus**.
- **Sudden paralysis of the right side** indicates involvement of the left cerebral hemisphere (**contralateral motor cortex** lesion), while speech disturbances point to the dominant hemisphere, which is typically the **left temporal lobe**.
*Caudate nucleus*
- Lesions of the **caudate nucleus** are primarily associated with **movement disorders** (e.g., chorea) and **behavioral changes**, not typically with fluent aphasia as described.
- While it plays a role in cognitive functions, its direct involvement in the specific language deficits presented is less likely.
*Broca’s area*
- Damage to **Broca's area**, located in the **frontal lobe**, causes **Broca's aphasia**, characterized by **non-fluent, halting speech** with good comprehension and poor repetition.
- The patient's speech is **fluent**, though off-topic, which contrasts with the typical presentation of Broca's aphasia.
*Arcuate fasciculus*
- The **arcuate fasciculus** connects Broca's and Wernicke's areas, and damage to it typically causes **conduction aphasia**, characterized by **impaired repetition** despite fluent speech and good comprehension.
- While the patient has impaired comprehension, his ability to repeat "fan" makes conduction aphasia less likely than Wernicke's aphasia, where repetition can vary but comprehension is profoundly affected.
*Cuneus gyrus*
- The **cuneus gyrus** is located in the **occipital lobe** and is primarily involved in **visual processing**.
- Damage to this area would lead to **visual field deficits** (e.g., hemianopia) rather than the language and comprehension problems described.
Limbic system US Medical PG Question 5: A 58-year-old right-handed man is brought to the emergency department after he was found unconscious in his living room by his wife. She reports that he has never had a similar episode before. The patient has hypertension and consumes multiple alcoholic drinks per day. On arrival, he is confused and oriented only to person. He cannot recall what happened. He has difficulty speaking and his words are slurred. He reports a diffuse headache and muscle pain and appears fatigued. His temperature is 37°C (98.6°F), pulse is 85/min, respirations are 14/min, and blood pressure is 135/70 mm Hg. Examination shows a 2-cm bruise on his right shoulder. Strength is 5/5 throughout, except for 1/5 in the left arm. The remainder of the physical examination shows no abnormalities. An ECG shows left ventricular hypertrophy. A CT scan of the head without contrast shows no abnormalities. Which of the following is the most likely underlying cause of this patient's symptoms?
- A. Syncope
- B. Seizure (Correct Answer)
- C. Transient ischemic attack
- D. Stroke
- E. Migraine
Limbic system Explanation: ***Seizure***
- The patient's **postictal confusion**, **slurred speech**, **diffuse headache**, and **muscle pain** following a transient loss of consciousness are highly suggestive of a seizure. The unilateral weakness (**Todd's paralysis**) is also a classic postictal phenomenon.
- The **bruise on his shoulder** could indicate a fall during the event, and his alcohol consumption and hypertension are risk factors for seizures.
*Syncope*
- Syncope is characterized by a **brief loss of consciousness due to global cerebral hypoperfusion**, usually followed by rapid and complete recovery of consciousness and neurological function.
- The patient's **prolonged confusion**, **slurred speech**, and **unilateral weakness** after the event are inconsistent with typical syncope.
*Transient ischemic attack*
- A TIA involves **transient neurological dysfunction caused by focal brain or retinal ischemia**, without acute infarction. Symptoms typically resolve within 24 hours.
- While the **slurred speech** and **unilateral weakness** (left arm 1/5 strength) might mimic TIA symptoms, the preceding **loss of consciousness** and subsequent **prolonged postictal state** are not characteristic of a TIA.
*Stroke*
- A stroke involves **brain tissue damage due to ischemia or hemorrhage**, leading to persistent neurological deficits.
- Although he presents with **unilateral weakness** and **slurred speech**, the **head CT without contrast** showed **no abnormalities**, ruling out acute ischemic stroke within the typical detection window for initial CT (within a few hours) and hemorrhagic stroke, and the preceding **loss of consciousness** and **postictal symptoms** point away from a primary stroke.
*Migraine*
- Migraine is a **primary headache disorder** often accompanied by neurological symptoms (aura) but typically does not involve a complete **loss of consciousness**.
- While he has a **diffuse headache**, the **loss of consciousness**, **unilateral weakness**, and **postictal confusion** are inconsistent with migraine.
Limbic system US Medical PG Question 6: A 46-year-old homeless man was found wandering aimlessly in the supermarket. On examination, he is confused and said that the President appointed men to kill him because he is disclosing state secrets to extraterrestrial organisms. The man also has horizontal nystagmus and an ataxic gait. What is the most likely cause of the clinical presentation?
- A. Neurofibrillary tangles
- B. Atrophy of globus pallidus
- C. Necrosis of mammillary bodies (Correct Answer)
- D. Hypothyroidism
- E. Trinucleotide repeat disorder
Limbic system Explanation: ***Necrosis of mammillary bodies***
- The patient's presentation with confusion, delusions (President appointing men to kill him), horizontal nystagmus, and ataxic gait is highly suggestive of **Wernicke-Korsakoff syndrome**, which is primarily caused by **thiamine (B1) deficiency**.
- **Necrosis of the mammillary bodies** is a classic neuropathological hallmark of Wernicke-Korsakoff syndrome, due to their high metabolic rate and vulnerability to thiamine deficiency.
*Neurofibrillary tangles*
- **Neurofibrillary tangles**, composed of hyperphosphorylated tau protein, are characteristic of **Alzheimer's disease** and other tauopathies.
- While Alzheimer's can cause confusion and disorientation, it typically does not present with acute nystagmus and ataxia in this manner, and delusions are usually less bizarre.
*Atrophy of globus pallidus*
- **Atrophy of the globus pallidus** can be seen in various neurodegenerative disorders, including some forms of **Huntington's disease** or mitochondrial disorders.
- However, it is not a primary or characteristic finding for Wernicke-Korsakoff syndrome or the specific acute constellation of symptoms presented.
*Hypothyroidism*
- **Hypothyroidism** can cause confusion, cognitive slowing, and sometimes ataxia (due to cerebellar dysfunction).
- However, it typically does not cause acute horizontal nystagmus or the distinct, florid psychotic delusions described.
*Trinucleotide repeat disorder*
- **Trinucleotide repeat disorders** (e.g., Huntington's disease, spinocerebellar ataxias) are genetic conditions that cause various neurological symptoms, including cognitive decline, movement disorders, and psychiatric features.
- These are typically chronic, progressive conditions and do not present acutely with the specific triad of nystagmus, ataxia, and confusion/psychosis seen in thiamine deficiency.
Limbic system US Medical PG Question 7: 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
Limbic system 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.
Limbic system US Medical PG Question 8: A 54-year-old man is brought to the emergency department 30 minutes after being hit by a car while crossing the street. He had a left-sided tonic-clonic seizure and one episode of vomiting while being transported to the hospital. On arrival, he is not oriented to person, place, or time. Physical examination shows flaccid paralysis of all extremities. A CT scan of the head is shown. This patient's symptoms are most likely the result of a hemorrhage in which of the following structures?
- A. Between the dura mater and the arachnoid mater
- B. Into the cerebral parenchyma
- C. Between the skull and the dura mater
- D. Between the arachnoid mater and the pia mater (Correct Answer)
- E. Into the ventricular system
Limbic system Explanation: ***Between the arachnoid mater and the pia mater (Correct)***
- The CT scan demonstrates diffuse high-density (white) material within the sulci and basal cisterns, indicative of a **subarachnoid hemorrhage**. This space is located between the arachnoid mater and the pia mater.
- The patient's presentation with altered mental status, seizures, vomiting, and flaccid paralysis following trauma is consistent with the severe neurological impact of a **traumatic subarachnoid hemorrhage**.
*Between the dura mater and the arachnoid mater (Incorrect)*
- Hemorrhage in this location is known as a **subdural hematoma**, which typically appears as a crescent-shaped collection of blood.
- While possible in trauma, the CT image shows blood primarily filling the sulci, not a subdural collection.
*Into the cerebral parenchyma (Incorrect)*
- This would be an **intraparenchymal hemorrhage**, appearing as a focal area of high density within the brain tissue itself.
- Although there might be some associated parenchymal injury in severe trauma, the predominant pattern seen on the CT is diffuse blood in the subarachnoid space.
*Between the skull and the dura mater (Incorrect)*
- This describes an **epidural hematoma**, often characterized by a lenticular (lens-shaped) collection of blood due to its confinement by dural attachments.
- The CT image does not show a lenticular collection of blood in this space.
*Into the ventricular system (Incorrect)*
- **Intraventricular hemorrhage** would show blood filling the cerebral ventricles.
- While subarachnoid hemorrhage can sometimes extend into the ventricles, the primary finding on this CT is diffuse blood in the subarachnoid space, not isolated ventricular blood.
Limbic system US Medical PG Question 9: A 67-year-old man is brought to the physician by his daughter because he frequently misplaces his personal belongings and becomes easily confused. His daughter mentions that his symptoms have progressively worsened for the past one year. On mental status examination, he is oriented to person, place, and time. He vividly recalls memories from his childhood but can only recall one of three objects presented to him after 5 minutes. His affect is normal. This patients' symptoms are most likely caused by damage to which of the following?
- A. Amygdala
- B. Superior temporal gyrus
- C. Hippocampus (Correct Answer)
- D. Ventral posterolateral nucleus
- E. Substantia nigra
Limbic system Explanation: ***Hippocampus***
- The patient's inability to recall new information (only one of three objects after 5 minutes) despite intact long-term memory suggests **anterograde amnesia**, which is characteristic of hippocampal damage.
- The hippocampus is crucial for the **formation of new declarative memories**, such as facts and events. Progressive decline in this function over a year is consistent with neurodegenerative conditions affecting the hippocampus, such as **Alzheimer's disease**.
*Amygdala*
- The amygdala is primarily involved in **processing emotions** and fear, as well as emotional memory.
- Damage to the amygdala would typically manifest as deficits in recognizing or expressing emotions, or in forming emotional memories, which are not the primary symptoms described here.
*Superior temporal gyrus*
- The superior temporal gyrus contains the **primary auditory cortex** and is involved in processing auditory information and language comprehension (Wernicke's area).
- Damage to this area would primarily cause auditory processing difficulties, such as **Wernicke's aphasia**, rather than memory problems for new information.
*Ventral posterolateral nucleus*
- The ventral posterolateral (VPL) nucleus of the thalamus is a key relay station for **somatosensory information** (touch, pain, temperature) from the body to the cerebral cortex.
- Damage to the VPL nucleus would lead to sensory deficits on the contralateral side of the body, not issues with memory formation.
*Substantia nigra*
- The substantia nigra is part of the basal ganglia and is crucial for **motor control**, producing dopamine that projects to the striatum.
- Damage to the substantia nigra is characteristic of **Parkinson's disease**, leading to motor symptoms like tremor, rigidity, bradykinesia, and postural instability, which are not described in this patient.
Limbic system US Medical PG Question 10: At what age does maximum brain growth occur?
- A. 6 months (Correct Answer)
- B. 1 year
- C. 2 years
- D. 3 years
- E. 5 years
Limbic system Explanation: ***6 months***
- **Brain growth** is most rapid during the early postnatal period, with the brain reaching almost **50% of its adult size by 6 months of age**.
- This period involves rapid **synaptogenesis** and myelination, crucial for early cognitive and motor development.
*1 year*
- While significant **brain growth** continues, the peak rate of increase in brain volume has typically passed by 1 year.
- At this age, the brain has reached approximately **75% of its adult size**.
*2 years*
- By 2 years, the brain is about **80% of its adult size**, indicating ongoing but slower growth compared to the first year.
- This period is more characterized by refinement of neural circuits rather than rapid volumetric expansion.
*3 years*
- At 3 years, the brain has attained around **90% of its adult size**, though important developmental changes continue.
- The rate of **neural development** at this stage largely focuses on strengthening existing connections and pruning less used ones.
*5 years*
- By 5 years, the brain has reached approximately **90-95% of its adult size**, with growth significantly slower than in earlier years.
- Development at this age focuses primarily on **synaptic pruning** and refinement of neural networks rather than volumetric growth.
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