A 68-year-old man comes to the physician because of double vision and unilateral right eye pain that began this morning. His vision improves when he covers either eye. He has hypertension, mild cognitive impairment, and type 2 diabetes mellitus. The patient has smoked two packs of cigarettes daily for 40 years. His current medications include lisinopril, donepezil, metformin, and insulin with meals. His temperature is 37°C (98.6°F), pulse is 85/minute, respirations are 12/minute, and blood pressure is 132/75 mm Hg. His right eye is abducted and depressed with slight intorsion. He can only minimally adduct the right eye. Visual acuity is 20/20 in both eyes. Extraocular movements of the left eye are normal. An MRI of the head shows no abnormalities. His fingerstick blood glucose concentration is 325 mg/dL. Further evaluation is most likely to show which of the following?
Q22
A 28-year-old man presents with visual disturbances. He says that he is having double vision since he woke up this morning. His past medical history is insignificant except for occasional mild headaches. The patient is afebrile and his vitals are within normal limits. On physical examination of his eyes, there is paralysis of left lateral gaze. Also, at rest, there is esotropia of the left eye. A noncontrast CT scan of the head reveals a tumor impinging on one of his cranial nerves. Which of the following nerves is most likely affected?
Q23
A 20-year-old man is brought to the emergency department 20 minutes after he sustained a stab wound to his back during an altercation. He reports weakness and numbness of the lower extremities. He has no history of serious illness. On arrival, he is alert and cooperative. His pulse is 90/min, and blood pressure is 100/65 mm Hg. Examination shows a deep 4-cm laceration on his back next to the vertebral column at the level of the T10 vertebra. Neurologic examination shows right-sided motor weakness with diminished vibratory sense ipsilaterally, decreased sensation to light touch at the level of his laceration and below, and left-sided loss of hot, cold, and pin-prick sensation at the level of the umbilicus and below. Deep tendon reflexes of his right lower extremity are 4+ and symmetrical. Babinski sign is absent bilaterally. The remainder of the examination shows no abnormalities. Which of the following is the most likely diagnosis?
Q24
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?
Q25
A 54-year-old man with hypertension and congenital blindness comes to the physician because he is unable to recognize objects by touch with his right hand. The symptoms started about 2 hours ago. When given a house key, he can feel the object in his right hand but is not able to identify what it is. This patient's condition is most likely caused by a lesion in which of the following locations?
Q26
A 78-year-old right-handed man with hypertension and hyperlipidemia is brought to the emergency department for sudden onset of nausea and vertigo one hour ago. Physical examination shows 5/5 strength in all extremities. Sensation to light touch and pinprick is decreased in the right arm and leg. A CT scan of the brain shows an acute infarction in the distribution of the left posterior cerebral artery. Further evaluation of this patient is most likely to show which of the following findings?
Q27
A 61-year-old man is found dead in his home after his neighbors became concerned when they did not see him for several days. The man was described as a "recluse" who lived alone and mostly kept to himself. Medical records reveal that he had not seen a physician in over a decade. He had a known history of vascular disease including hypertension, hyperlipidemia, and diabetes mellitus. He did not take any medications for these conditions. An autopsy is performed to identify the cause of death. Although it is determined that the patient suffered from a massive cerebrovascular accident as the cause of death, an incidental finding of a tumor arising from the spinal cord meninges is noted. The tumor significantly compresses the left anterolateral lower thoracic spinal cord. The right side of the spinal cord and the posterior spinal cord appear normal. Which of the following would most likely be impaired due to this lesion?
Q28
A 33-year-old man is brought to the emergency department 20 minutes after he fell from the roof of his house. On arrival, he is unresponsive to verbal and painful stimuli. His pulse is 72/min and blood pressure is 132/86 mm Hg. A CT scan of the head shows a fracture in the anterior cranial fossa and a 1-cm laceration in the left anterior orbital gyrus. If the patient survives, which of the following would ultimately be the most common cell type at the injured region of the frontal lobe?
Q29
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?
Q30
A 69-year-old man undergoes modified radical neck dissection for an oropharyngeal tumor. During the procedure, he requires multiple blood transfusions. Four hours after the surgery, examination shows that the right and left pupils do not constrict when a light is shone into the left eye. When light is shone into the right eye, both pupils constrict. Fundoscopic examination shows no abnormalities. Which of the following is the most likely location of the lesion?
Neuroanatomy US Medical PG Practice Questions and MCQs
Question 21: A 68-year-old man comes to the physician because of double vision and unilateral right eye pain that began this morning. His vision improves when he covers either eye. He has hypertension, mild cognitive impairment, and type 2 diabetes mellitus. The patient has smoked two packs of cigarettes daily for 40 years. His current medications include lisinopril, donepezil, metformin, and insulin with meals. His temperature is 37°C (98.6°F), pulse is 85/minute, respirations are 12/minute, and blood pressure is 132/75 mm Hg. His right eye is abducted and depressed with slight intorsion. He can only minimally adduct the right eye. Visual acuity is 20/20 in both eyes. Extraocular movements of the left eye are normal. An MRI of the head shows no abnormalities. His fingerstick blood glucose concentration is 325 mg/dL. Further evaluation is most likely to show which of the following?
A. Ptosis (Correct Answer)
B. Dilated and fixed pupil
C. Bitemporal hemianopsia
D. Miosis and anhidrosis
E. Positive swinging-flashlight test
Explanation: ***Ptosis***
- The patient's presentation of an **abducted and depressed right eye with minimal adduction** is highly suggestive of an **ischemic (diabetic) third nerve palsy**.
- Ischemic third nerve palsies characteristically **spare the pupillary fibers** (pupil remains normal in size and reactive) but affect the **somatomotor fibers** that innervate the extraocular muscles and the **levator palpebrae superioris**, leading to **ptosis**.
- The key clinical feature distinguishing ischemic from compressive CN III palsy is **pupil-sparing**, which is present in this case.
*Dilated and fixed pupil*
- A dilated and fixed pupil would indicate **compression of the oculomotor nerve**, often by an aneurysm (e.g., posterior communicating artery aneurysm).
- Compressive lesions affect the superficial **pupillomotor fibers** first, while ischemic third nerve palsies, as seen in patients with **diabetes**, typically affect the inner somatomotor fibers while **sparing the pupil**.
*Bitemporal hemianopsia*
- This visual field defect is characteristic of **optic chiasm compression**, commonly caused by a **pituitary adenoma**.
- This patient's symptoms are localized to a single eye and involve extraocular muscle dysfunction, not visual field loss.
*Miosis and anhidrosis*
- **Miosis** (constricted pupil) and **anhidrosis** (decreased sweating) on one side of the face, accompanied by **ptosis**, are classic signs of **Horner syndrome**.
- Horner syndrome results from a lesion in the **sympathetic pathway**, which is inconsistent with the extraocular muscle deficits observed in this patient.
*Positive swinging-flashlight test*
- A positive swinging-flashlight test (Marcus Gunn pupil) indicates an **afferent pupillary defect**, often seen in conditions affecting the **optic nerve** (e.g., optic neuritis, severe retinal disease).
- This patient's symptoms point to a **cranial nerve III palsy**, which affects efferent ocular movements and typically does not cause an afferent pupillary defect.
Question 22: A 28-year-old man presents with visual disturbances. He says that he is having double vision since he woke up this morning. His past medical history is insignificant except for occasional mild headaches. The patient is afebrile and his vitals are within normal limits. On physical examination of his eyes, there is paralysis of left lateral gaze. Also, at rest, there is esotropia of the left eye. A noncontrast CT scan of the head reveals a tumor impinging on one of his cranial nerves. Which of the following nerves is most likely affected?
A. Trigeminal nerve
B. Optic nerve
C. Oculomotor nerve
D. Trochlear nerve
E. Abducens nerve (Correct Answer)
Explanation: ***Abducens nerve***
- **Paralysis of left lateral gaze** and **esotropia** (inward turning of the eye) at rest are classic signs of a **left abducens nerve (CN VI) palsy**. This nerve exclusively innervates the **lateral rectus muscle**, which is responsible for abducting (moving outward) the eye.
- Impingement from a **tumor** is a common cause of cranial nerve palsies, and the presentation perfectly matches the function of the abducens nerve.
*Trigeminal nerve*
- The **trigeminal nerve (CN V)** is responsible for **facial sensation** and **mastication** (chewing).
- Dysfunction would present as facial numbness, pain, or weakness in chewing, not visual disturbances or eye movement issues.
*Optic nerve*
- The **optic nerve (CN II)** transmits **visual information** from the retina to the brain.
- Lesions typically cause **vision loss** (e.g., blindness, scotoma, visual field defects), not double vision or eye movement paralysis.
*Oculomotor nerve*
- The **oculomotor nerve (CN III)** controls most **extraocular muscles** (medial, superior, inferior rectus, inferior oblique) and the **levator palpebrae superioris** (eyelid elevation), as well as pupillary constriction.
- A palsy would typically present with a **"down and out" eye**, **ptosis** (drooping eyelid), and **mydriasis** (dilated pupil), which are not described.
*Trochlear nerve*
- The **trochlear nerve (CN IV)** innervates the **superior oblique muscle**, which depresses and intorts the eye.
- A palsy typically causes **vertical double vision**, especially when looking down and inward, and a compensatory head tilt away from the affected side. This does not match the described lateral gaze paralysis.
Question 23: A 20-year-old man is brought to the emergency department 20 minutes after he sustained a stab wound to his back during an altercation. He reports weakness and numbness of the lower extremities. He has no history of serious illness. On arrival, he is alert and cooperative. His pulse is 90/min, and blood pressure is 100/65 mm Hg. Examination shows a deep 4-cm laceration on his back next to the vertebral column at the level of the T10 vertebra. Neurologic examination shows right-sided motor weakness with diminished vibratory sense ipsilaterally, decreased sensation to light touch at the level of his laceration and below, and left-sided loss of hot, cold, and pin-prick sensation at the level of the umbilicus and below. Deep tendon reflexes of his right lower extremity are 4+ and symmetrical. Babinski sign is absent bilaterally. The remainder of the examination shows no abnormalities. Which of the following is the most likely diagnosis?
A. Brown-Sequard syndrome (Correct Answer)
B. Anterior cord syndrome
C. Posterior cord syndrome
D. Cauda equina syndrome
E. Central cord syndrome
Explanation: ***Brown-Sequard syndrome***
- This syndrome is characterized by **ipsilateral motor paresis** and **loss of proprioception/vibration sensation**, along with **contralateral loss of pain and temperature sensation**.
- The patient's presentation of right-sided motor weakness and diminished vibratory sense ipsilaterally, coupled with left-sided loss of hot, cold, and pin-prick sensation, perfectly matches the classic signs of **Brown-Sequard syndrome** from a hemisection of the spinal cord (due to the stab wound).
*Anterior cord syndrome*
- This syndrome typically presents with **paraplegia or quadriplegia** and loss of pain and temperature sensation below the level of the lesion, with **preservation of proprioception and vibratory sensation**.
- The patient maintains **ipsilateral vibratory sensation** and has differential sensory loss, which is inconsistent with anterior cord syndrome where all distal sensation is broadly affected.
*Posterior cord syndrome*
- This syndrome is marked by a predominant loss of **proprioception and vibratory sensation** below the level of the lesion, with **preserved motor function** and pain/temperature sensation.
- The patient exhibits significant **motor weakness** and **contralateral loss of pain and temperature**, which are not typical features of posterior cord syndrome.
*Cauda equina syndrome*
- Cauda equina syndrome involves injury to the **nerve roots below the conus medullaris** and presents with **flaccid paralysis**, **saddle anesthesia**, and **bowel/bladder dysfunction**.
- The patient's presentation of spastic signs (4+ DTRs) and specific sensory deficits of a spinal cord lesion are inconsistent with the **lower motor neuron** signs of cauda equina syndrome.
*Central cord syndrome*
- This syndrome typically results in **greater motor impairment in the upper extremities than in the lower extremities**, along with a **variable sensory loss** below the level of the lesion, often involving a "cape-like" distribution of sensory loss.
- The patient's injury is at T10, and while there is motor weakness, the specific pattern of ipsilateral motor with contralateral pain/temperature loss is not characteristic of central cord syndrome, which usually affects the cervical region and has a different motor pattern.
Question 24: 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
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.
Question 25: A 54-year-old man with hypertension and congenital blindness comes to the physician because he is unable to recognize objects by touch with his right hand. The symptoms started about 2 hours ago. When given a house key, he can feel the object in his right hand but is not able to identify what it is. This patient's condition is most likely caused by a lesion in which of the following locations?
A. Ipsilateral cingulate gyrus
B. Contralateral superior parietal lobule (Correct Answer)
C. Ipsilateral inferior frontal gyrus
D. Ipsilateral superior temporal gyrus
E. Contralateral precentral gyrus
Explanation: ***Contralateral superior parietal lobule***
- The patient exhibits **astereognosis**, which is the inability to recognize objects by touch despite intact sensation, suggesting a lesion in the **parietal association cortex**.
- Since the deficit is in the **right hand**, the lesion must be on the **contralateral side**, which is the left superior parietal lobule.
*Ipsilateral cingulate gyrus*
- The **cingulate gyrus** is primarily involved in emotion, learning, and memory, and a lesion here would not typically cause isolated astereognosis.
- Furthermore, astereognosis with the right hand implies a contralateral lesion, not an ipsilateral one.
*Ipsilateral inferior frontal gyrus*
- The **inferior frontal gyrus** (Broca's area) is crucial for speech production; damage here usually results in **expressive aphasia**.
- A lesion in this area would not explain the patient's specific difficulty with tactile object recognition in the right hand.
*Ipsilateral superior temporal gyrus*
- The **superior temporal gyrus** (Wernicke's area) is concerned with language comprehension; damage typically causes **receptive aphasia**.
- This location is not associated with astereognosis, nor would an ipsilateral lesion explain a right-hand deficit.
*Contralateral precentral gyrus*
- The **precentral gyrus** is the primary motor cortex; a lesion here would cause **motor deficits** such as weakness or paralysis of the contralateral side, not an inability to recognize objects by touch while sensation is intact.
- The patient can feel the object, indicating intact sensation and motor function, merely difficulty identifying it.
Question 26: A 78-year-old right-handed man with hypertension and hyperlipidemia is brought to the emergency department for sudden onset of nausea and vertigo one hour ago. Physical examination shows 5/5 strength in all extremities. Sensation to light touch and pinprick is decreased in the right arm and leg. A CT scan of the brain shows an acute infarction in the distribution of the left posterior cerebral artery. Further evaluation of this patient is most likely to show which of the following findings?
A. Right-sided homonymous hemianopia (Correct Answer)
B. Prosopagnosia
C. Left-sided gaze deviation
D. Left-sided hemineglect
E. Right-sided superior quadrantanopia
Explanation: ***Right-sided homonymous hemianopia***
- A **left PCA infarct** typically affects the **occipital lobe**, specifically the visual cortex or optic radiations, leading to a contralateral visual field deficit.
- The **right visual field** from both eyes projects to the left occipital lobe, so infarction here causes a **right homonymous hemianopia**.
*Prosopagnosia*
- **Prosopagnosia**, the inability to recognize faces, is associated with infarction of the **fusiform gyrus**, often a bilateral PCA territory infarction or an infarct affecting the right occipital or temporal lobe.
- This patient has a **left PCA infarct**, so isolated prosopagnosia is less likely.
*Left-sided gaze deviation*
- **Gaze deviation** usually occurs in lesions of the **frontal eye fields** (Brodmann area 8), which are supplied by the middle cerebral artery, causing the eyes to deviate towards the side of the lesion in acute stages.
- A **PCA infarct** typically spares the frontal eye fields and the brainstem gaze centers.
*Left-sided hemineglect*
- **Hemineglect** is most commonly associated with lesions of the **right parietal lobe** or right frontal lobe, primarily in the territory of the right middle cerebral artery.
- With a **left PCA infarct**, left-sided hemineglect is an unexpected finding.
*Right-sided superior quadrantanopia*
- A **superior quadrantanopia** is caused by damage to the **inferior optic radiations** (Meyer's loop), which typically carry information from the superior visual field.
- A complete **homonymous hemianopia** involving the entire right visual field is more characteristic of an occipital lobe lesion due to a PCA infarct, rather than an isolated quadrantanopia.
Question 27: A 61-year-old man is found dead in his home after his neighbors became concerned when they did not see him for several days. The man was described as a "recluse" who lived alone and mostly kept to himself. Medical records reveal that he had not seen a physician in over a decade. He had a known history of vascular disease including hypertension, hyperlipidemia, and diabetes mellitus. He did not take any medications for these conditions. An autopsy is performed to identify the cause of death. Although it is determined that the patient suffered from a massive cerebrovascular accident as the cause of death, an incidental finding of a tumor arising from the spinal cord meninges is noted. The tumor significantly compresses the left anterolateral lower thoracic spinal cord. The right side of the spinal cord and the posterior spinal cord appear normal. Which of the following would most likely be impaired due to this lesion?
A. Pain sensation from the right side of the body (Correct Answer)
B. Proprioceptive sensation from the left side of the body
C. Temperature sensation from the left side of the body
D. Pressure sensation from the left side of the body
E. Vibratory sensation from the right side of the body
Explanation: ***Pain sensation from the right side of the body***
- Compression of the **left anterolateral lower thoracic spinal cord** would affect the **spinothalamic tract** on that side. The spinothalamic tract carries **pain and temperature** sensations from the **contralateral** side of the body.
- Since the fibers decussate (cross over) at the level of the spinal cord entry, a lesion on the left side of the cord would impair pain sensation from the right side of the body.
*Proprioceptive sensation from the left side of the body*
- Proprioception is carried by the **dorsal columns**, which are located in the posterior part of the spinal cord and decussate in the brainstem.
- The lesion is described as affecting the **anterolateral** left spinal cord, and the posterior cord is noted as normal, making this unlikely.
*Temperature sensation from the left side of the body*
- Temperature sensation is carried by the **spinothalamic tract**, similar to pain.
- This tract decussates at the level of entry into the spinal cord, so a lesion on the left anterolateral cord would impair temperature sensation from the **contralateral (right)** side, not the ipsilateral (left) side.
*Pressure sensation from the left side of the body*
- **Crude touch and pressure** are partially carried by the **spinothalamic tract** and partially by the **dorsal columns**.
- Impairment of pressure sensation on the left side would primarily indicate damage to the ipsilateral dorsal column pathway or significant bilateral spinothalamic involvement, neither of which is consistent with an isolated left anterolateral lesion affecting ipsilateral sensation.
*Vibratory sensation from the right side of the body*
- Vibratory sensation is carried by the **dorsal columns**, which are in the posterior spinal cord and decussate in the medulla oblongata.
- The lesion is in the **anterolateral** left spinal cord, and the posterior cord is noted as normal, making this an unlikely finding.
Question 28: A 33-year-old man is brought to the emergency department 20 minutes after he fell from the roof of his house. On arrival, he is unresponsive to verbal and painful stimuli. His pulse is 72/min and blood pressure is 132/86 mm Hg. A CT scan of the head shows a fracture in the anterior cranial fossa and a 1-cm laceration in the left anterior orbital gyrus. If the patient survives, which of the following would ultimately be the most common cell type at the injured region of the frontal lobe?
A. Microglia
B. Oligodendrocytes
C. Neurons
D. Schwann cells
E. Astrocytes (Correct Answer)
Explanation: ***Astrocytes***
- Following **neuronal injury**, astrocytes proliferate rapidly and form a **glial scar** around the damaged area to isolate it and prevent further spread of damage.
- This process, known as **astrogliosis**, leads to astrocytes becoming the most abundant cell type in the chronically injured region of the central nervous system.
*Microglia*
- **Microglia** are the brain's resident immune cells and are primarily involved in **phagocytosis** of cellular debris and pathogens after injury.
- While they are activated and proliferate early after injury, they typically do not become the most common cell type in the *chronically injured* region.
*Oligodendrocytes*
- **Oligodendrocytes** are responsible for forming the **myelin sheath** around axons in the central nervous system.
- They are often damaged during acute brain injury and do not typically proliferate to become the most common cell type in the scar tissue.
*Neurons*
- **Neurons** are the primary cells affected by acute brain injury, and many are irrecoverably lost at the site of trauma.
- The adult central nervous system has very limited capacity for neurogenesis, so neurons do not regenerate or become the most common cell type after injury.
*Schwann cells*
- **Schwann cells** are responsible for myelinating axons in the **peripheral nervous system (PNS)**.
- They are not found in the central nervous system (CNS) region of brain injury and therefore would not be involved in the repair or scarring process there.
Question 29: 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
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.
Question 30: A 69-year-old man undergoes modified radical neck dissection for an oropharyngeal tumor. During the procedure, he requires multiple blood transfusions. Four hours after the surgery, examination shows that the right and left pupils do not constrict when a light is shone into the left eye. When light is shone into the right eye, both pupils constrict. Fundoscopic examination shows no abnormalities. Which of the following is the most likely location of the lesion?
A. Ciliary ganglion
B. Pretectal nuclei
C. Edinger-Westphal nucleus
D. Optic nerve (Correct Answer)
E. Superior cervical ganglion
Explanation: ***Optic nerve***
- The finding that pupils **do not constrict** when light is shone into the left eye (afferent defect) but both pupils constrict when light is shone into the right eye (intact efferent pathway) indicates a lesion in the **afferent limb** of the pupillary light reflex on the left side.
- The **optic nerve** (cranial nerve II) transmits afferent signals from the retina to the brainstem. A lesion here prevents the signal from reaching the pretectal nuclei, thus bilateral pupillary constriction does not occur when the affected eye is stimulated.
*Ciliary ganglion*
- A lesion in the **ciliary ganglion** would affect the **efferent pathway** of pupillary constriction, typically leading to a dilated, unreactive pupil (e.g., Adie's tonic pupil).
- This would mean that the affected pupil would not constrict when *either* eye is stimulated, which is not consistent with the described findings.
*Pretectal nuclei*
- The **pretectal nuclei** receive afferent input from both optic tracts and project to the Edinger-Westphal nuclei, mediating the consensual light reflex.
- A lesion here would typically affect both direct and consensual light reflexes, or cause selective deficits not limited to a single afferent pathway.
*Edinger-Westphal nucleus*
- The **Edinger-Westphal nucleus** is the parasympathetic nucleus of the oculomotor nerve (CN III) and controls pupillary constriction.
- A lesion would disrupt the **efferent pathway** unilaterally or bilaterally, leading to a fixed, dilated pupil.
*Superior cervical ganglion*
- Lesions of the **superior cervical ganglion** affect the **sympathetic pathway** to the eye, resulting in **Horner's syndrome** (miosis, ptosis, anhidrosis).
- This would cause a miotic (constricted) pupil, not the failure of constriction described in the scenario.
