Functional neuroanatomy of vision — MCQs

10 questions

A 58-year-old woman presents with vision loss in her right eye. She noticed the visual changes the morning of presentation and has never experienced this visual disturbance before. Her medical history is significant for hypertension, hypercholesterolemia, and type II diabetes mellitus. She is currently on lisinopril, lovastatin, and metformin. She has smoked a pack of cigarettes daily for the last 25 years and also is a social drinker. On physical exam, her lids and lashes appear normal and there is no conjunctival injection. Both pupils are equal, round, and reactive to light; however, when the penlight is swung from the left eye to the right eye, there is bilateral pupillary dilation. The nerve that is most likely defective in this patient relays information to which of the following?

A 34-year-old woman comes to the physician because she has not had her period for 4 months. Menses had previously occurred at regular 28-day intervals with moderate flow. A home pregnancy test was negative. She also reports recurrent headaches and has noticed that when she goes to the movies she cannot see the outer edges of the screen without turning her head to each side. This patient's symptoms are most likely caused by abnormal growth of which of the following?

A 22-year-old man is brought to the physician by his mother because of concerns about his recent behavior. Three months ago, the patient first reported hearing loud voices coming from the ceiling of his room. During this time, he has also become increasingly worried that visitors to the house were placing secret surveillance cameras. Mental status examination shows tangential speech with paranoid thoughts. Treatment for this patient's condition predominantly targets which of the following dopaminergic pathways?

An 82-year-old right-handed woman is brought in by ambulance after being found down in her home. On presentation, she is found to be awake but does not follow directions or respond to questions. She is able to speak and produces a fluent string of nonsensical words and sounds. She does not appear to be bothered by her deficits. Subsequent neurologic exam finds that the patient is unable to comprehend any instructions and is also unable to repeat phrases. CT scan reveals an acute stroke to her left hemisphere. Damage to which of the following structures would be most likely to result in this pattern of deficits?

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 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 25-year-old previously healthy woman presents to her PCP reporting cessation of menses for the past 6 months. Previously, her period occurred regularly, every 30 days. She also complains of decreased peripheral vision, most noticeably when she is driving her car. She denies any recent sexual activity and a pregnancy test is negative. Upon further work-up, what physical exam finding is most likely to be identified?

A 32-year-old previously healthy female presents to her primary care physician with double vision. She first noted the double vision yesterday and saw no improvement this morning. She does not think it is worsening. She has not had any changes in her normal routine though she recalls one episode of right arm weakness 2 months ago. She did not seek treatment and the weakness subsided after several days. She does not have a history of head trauma. She denies headache, fever, chills, nausea, vomiting, paresthesias, extremity pain, or weakness. On exam she has right adduction palsy on leftward gaze. She has no focal weakness. Which of the following additional physical exam findings is associated with the lesion responsible for her ocular findings?

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?

Q10

At what age does maximum brain growth occur?

Functional neuroanatomy of vision US Medical PG Practice Questions and MCQs

Question 1: A 58-year-old woman presents with vision loss in her right eye. She noticed the visual changes the morning of presentation and has never experienced this visual disturbance before. Her medical history is significant for hypertension, hypercholesterolemia, and type II diabetes mellitus. She is currently on lisinopril, lovastatin, and metformin. She has smoked a pack of cigarettes daily for the last 25 years and also is a social drinker. On physical exam, her lids and lashes appear normal and there is no conjunctival injection. Both pupils are equal, round, and reactive to light; however, when the penlight is swung from the left eye to the right eye, there is bilateral pupillary dilation. The nerve that is most likely defective in this patient relays information to which of the following?

A. Oculomotor nucleus
B. Edinger-Westphal nucleus
C. Medial geniculate nucleus
D. Lateral geniculate nucleus (Correct Answer)
E. Ventral posteromedial nucleus

Explanation: ***Lateral geniculate nucleus*** - The patient presents with unilateral vision loss (right eye) and a **relative afferent pupillary defect (RAPD)**, demonstrated by bilateral pupillary dilation when light swings from the unaffected left eye to the affected right eye. - An RAPD localizes the lesion to the **afferent visual pathway anterior to the optic chiasm**, specifically the **retina or optic nerve (CN II)** of the affected eye. - The **optic nerve** relays visual information TO the **lateral geniculate nucleus (LGN)** of the thalamus, making this the correct answer to the question "which structure does the defective nerve relay information to?" - Note: A lesion directly AT the LGN (post-chiasmal) would cause vision loss but would NOT produce an RAPD, as the pupillary reflex integrates bilaterally at the pretectal nucleus before reaching the LGN. *Oculomotor nucleus* - The **oculomotor nucleus** contains motor neurons for CN III, controlling most extraocular muscles and providing parasympathetic innervation to the pupil via the Edinger-Westphal nucleus. - A lesion here would cause **efferent deficits**: ipsilateral ptosis, eye positioned "down and out," and a dilated, fixed pupil - but NOT vision loss or RAPD. - This is an efferent pathway issue, not an afferent visual pathway problem. *Edinger-Westphal nucleus* - The **Edinger-Westphal nucleus** provides preganglionic parasympathetic fibers via CN III to the ciliary ganglion, controlling pupillary constriction and accommodation. - A lesion would cause a **dilated pupil with impaired direct and consensual light reflex** and impaired accommodation, but NOT vision loss or RAPD. - This affects the efferent limb of the pupillary reflex, not the afferent visual pathway. *Medial geniculate nucleus* - The **medial geniculate nucleus (MGN)** is a thalamic relay nucleus in the **auditory pathway**, receiving input from the inferior colliculus. - A lesion would cause hearing deficits, not visual symptoms or pupillary abnormalities. *Ventral posteromedial nucleus* - The **ventral posteromedial nucleus (VPM)** of the thalamus relays sensory information from the face (via trigeminal nerve) and taste sensation. - A lesion would cause **facial sensory deficits** (numbness, altered sensation) or taste disturbances, not vision loss or RAPD.

Question 2: A 34-year-old woman comes to the physician because she has not had her period for 4 months. Menses had previously occurred at regular 28-day intervals with moderate flow. A home pregnancy test was negative. She also reports recurrent headaches and has noticed that when she goes to the movies she cannot see the outer edges of the screen without turning her head to each side. This patient's symptoms are most likely caused by abnormal growth of which of the following?

A. Adenohypophysis (Correct Answer)
B. Astrocytes
C. Schwann cells
D. Pineal gland
E. Arachnoid cap cells

Explanation: ***Adenohypophysis*** - The patient's symptoms of **amenorrhea**, recurrent headaches, and **bitemporal hemianopsia** (cannot see the outer edges of the screen) strongly suggest a **pituitary adenoma**. - Pituitary adenomas typically arise from the **adenohypophysis** and can cause hormonal imbalances (leading to amenorrhea) and compress the **optic chiasm** (leading to visual field defects). *Astrocytes* - **Astrocytes** are glial cells that support neurons and form the **blood-brain barrier**; their abnormal growth typically leads to **gliomas**, which present with different symptoms like seizures, focal neurological deficits, or increased intracranial pressure, rather than specific endocrine dysfunction and bitemporal hemianopsia. - While gliomas can cause headaches and visual field defects, the combination with **amenorrhea** points away from this diagnosis. *Schwann cells* - **Schwann cells** produce myelin in the peripheral nervous system; abnormal growth usually results in **schwannomas**, which present with symptoms related to cranial nerve or spinal nerve compression (e.g., hearing loss in acoustic neuroma), not typically bitemporal hemianopsia or amenorrhea. - Schwannomas are derived from the myelin sheaths of peripheral nerves and would not explain the endocrine disturbances seen here. *Pineal gland* - Lesions of the **pineal gland** often cause **Parinaud syndrome** (failure of upward gaze, pupillary abnormalities) due to compression of the superior colliculi, and can also lead to **hydrocephalus** or precocious puberty. - While headaches can occur, **bitemporal hemianopsia** and **amenorrhea** are not characteristic presentations of pineal gland tumors. *Arachnoid cap cells* - Abnormal growth of **arachnoid cap cells** leads to **meningiomas**, which are typically slow-growing tumors arising from the meninges. - Meningiomas can cause headaches and focal neurological deficits depending on their location, but they do **not typically cause bitemporal hemianopsia** or **endocrine dysfunction** like amenorrhea, as they are usually external to the brain tissue.

Question 3: A 22-year-old man is brought to the physician by his mother because of concerns about his recent behavior. Three months ago, the patient first reported hearing loud voices coming from the ceiling of his room. During this time, he has also become increasingly worried that visitors to the house were placing secret surveillance cameras. Mental status examination shows tangential speech with paranoid thoughts. Treatment for this patient's condition predominantly targets which of the following dopaminergic pathways?

A. Mesocortical pathway
B. Thalamocortical pathway
C. Nigrostriatal pathway
D. Corticostriatal pathway
E. Mesolimbic pathway (Correct Answer)

Explanation: ***Mesolimbic pathway*** - The patient's symptoms of **auditory hallucinations** and **paranoid delusions** are **positive symptoms** of psychosis consistent with **schizophrenia**. - **Hyperactivity** of the **mesolimbic dopaminergic pathway** is strongly associated with the positive symptoms of schizophrenia, making it the primary target for antipsychotic treatment. *Mesocortical pathway* - The **mesocortical pathway** is primarily involved in **cognition, motivation, and executive functions**, originating from the ventral tegmental area and projecting to the prefrontal cortex. - **Hypoactivity** in this pathway is thought to contribute to the **negative and cognitive symptoms** of schizophrenia, not the positive symptoms described. *Thalamocortical pathway* - The **thalamocortical pathway** connects the **thalamus to the cerebral cortex** and is crucial for sensory processing, arousal, and consciousness. - While involved in neural circuits, it is not considered a primary dopaminergic pathway targeted for the treatment of positive psychotic symptoms. *Nigrostriatal pathway* - The **nigrostriatal pathway** projects from the **substantia nigra to the striatum** and is primarily involved in **motor control**. - Blocking dopamine receptors in this pathway by antipsychotic medications can cause **extrapyramidal symptoms (EPS)**, but it is not the main pathway responsible for positive psychotic symptoms or their treatment. *Corticostriatal pathway* - The **corticostriatal pathway** is **predominantly a glutamatergic pathway** connecting the **cerebral cortex to the striatum**, playing a role in motor control and habit formation. - This is not a primary dopaminergic pathway and is not directly implicated in the positive symptoms of schizophrenia or their pharmacological treatment.

Question 4: An 82-year-old right-handed woman is brought in by ambulance after being found down in her home. On presentation, she is found to be awake but does not follow directions or respond to questions. She is able to speak and produces a fluent string of nonsensical words and sounds. She does not appear to be bothered by her deficits. Subsequent neurologic exam finds that the patient is unable to comprehend any instructions and is also unable to repeat phrases. CT scan reveals an acute stroke to her left hemisphere. Damage to which of the following structures would be most likely to result in this pattern of deficits?

A. Precentral gyrus
B. Superior temporal gyrus (Correct Answer)
C. Arcuate fasciculus
D. Inferior frontal gyrus
E. Watershed zone

Explanation: ***Superior temporal gyrus*** - This patient presents with **fluent aphasia** (speaking nonsensical words), severely impaired **comprehension**, and impaired **repetition**. This triad is characteristic of **Wernicke's aphasia**. - **Wernicke's area**, responsible for language comprehension, is located in the **posterior part of the superior temporal gyrus** in the dominant hemisphere (typically left). *Precentral gyrus* - The **precentral gyrus** contains the **primary motor cortex** and its damage would primarily cause contralateral motor deficits (e.g., **hemiparesis** or **hemiplegia**). - This area is not directly involved in language comprehension or production of fluent but nonsensical speech. *Arcuate fasciculus* - Damage to the **arcuate fasciculus**, a white matter tract connecting Broca's and Wernicke's areas, results in **conduction aphasia**. - In **conduction aphasia**, comprehension and fluency are relatively preserved, but **repetition is severely impaired**. This patient also has impaired comprehension. *Inferior frontal gyrus* - The **inferior frontal gyrus** houses **Broca's area**, which is responsible for **language production and motor aspects of speech**. - Damage to this area typically causes **Broca's aphasia**, characterized by **non-fluent speech**, preserved comprehension, and impaired repetition. This patient has fluent speech. *Watershed zone* - **Watershed infarcts** occur at the borders between major arterial territories due to hypoperfusion, often leading to **transcortical aphasias**. - While transcortical sensory aphasia involves impaired comprehension and fluent speech, **repetition is preserved**, which is not the case here.

Question 5: 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 6: 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 7: A 25-year-old previously healthy woman presents to her PCP reporting cessation of menses for the past 6 months. Previously, her period occurred regularly, every 30 days. She also complains of decreased peripheral vision, most noticeably when she is driving her car. She denies any recent sexual activity and a pregnancy test is negative. Upon further work-up, what physical exam finding is most likely to be identified?

A. Breast mass
B. Enlarged thyroid
C. Bitemporal hemianopsia (Correct Answer)
D. Renal failure
E. Pregnancy

Explanation: ***Bitemporal hemianopsia*** - The patient's symptoms of **amenorrhea** and **decreased peripheral vision** are highly suggestive of a **pituitary adenoma**, specifically one that causes mass effect on the optic chiasm. - A pituitary adenoma can compress the **optic chiasm**, leading to the classic visual field defect known as **bitemporal hemianopsia**, where the temporal (peripheral) vision in both eyes is lost. *Breast mass* - While breast masses are common, they are generally **not associated** with amenorrhea or peripheral vision loss. - A breast mass would typically present with a palpable lump or imaging abnormality of the breast. *Enlarged thyroid* - An enlarged thyroid (goiter) can be associated with thyroid dysfunction, which can cause menstrual irregularities, but it typically **does not cause peripheral vision loss**. - Visual field defects point towards a problem with the **optic pathways**, not thyroid pathology. *Renal failure* - **Chronic renal failure** can cause menstrual irregularities due to hormonal imbalances, but it is **not directly linked** to visual field defects like bitemporal hemianopsia. - Renal failure would present with symptoms like edema, fatigue, and changes in urination. *Pregnancy* - Although amenorrhea is a hallmark of pregnancy, the patient has explicitly **denied recent sexual activity** and a **negative pregnancy test** rules this out. - Pregnancy does not cause **bitemporal hemianopsia** as a primary symptom.

Question 8: A 32-year-old previously healthy female presents to her primary care physician with double vision. She first noted the double vision yesterday and saw no improvement this morning. She does not think it is worsening. She has not had any changes in her normal routine though she recalls one episode of right arm weakness 2 months ago. She did not seek treatment and the weakness subsided after several days. She does not have a history of head trauma. She denies headache, fever, chills, nausea, vomiting, paresthesias, extremity pain, or weakness. On exam she has right adduction palsy on leftward gaze. She has no focal weakness. Which of the following additional physical exam findings is associated with the lesion responsible for her ocular findings?

A. Afferent pupillary defect in the left eye
B. Horizontal nystagmus in the left eye on leftward gaze (Correct Answer)
C. Ptosis on the right
D. Left abduction palsy on leftward gaze
E. Proptosis of the right eye

Explanation: **Horizontal nystagmus in the left eye on leftward gaze** - The patient presents with **double vision** and **right adduction palsy on leftward gaze**, indicative of an **internuclear ophthalmoplegia (INO)**, highly suggestive of **multiple sclerosis (MS)** in a young adult with a history of transient neurological symptoms (right arm weakness). - In INO, the eye attempting to adduct (in this case, the right eye on leftward gaze) has impaired movement, while the contralateral abducting eye (left eye on leftward gaze) often exhibits **horizontal nystagmus**. *Afferent pupillary defect in the left eye* - An **afferent pupillary defect (APD)**, also known as a **Marcus Gunn pupil**, indicates a lesion to the **afferent visual pathway** (retina, optic nerve, or optic chiasm). - While MS can cause optic neuritis leading to APD, it is not a direct consequence or associated finding of an INO itself. *Ptosis on the right* - **Ptosis** (drooping eyelid) is typically caused by dysfunction of the **oculomotor nerve (cranial nerve III)** or the **sympathetic pathway (Horner's syndrome)**. - While MS can affect cranial nerves, ptosis is not a characteristic finding specifically associated with INO. *Left abduction palsy on leftward gaze* - A **left abduction palsy on leftward gaze** would mean the left eye is unable to fully abduct, indicating a problem with the **left abducens nerve (cranial nerve VI)** or its nucleus. - In INO, it is the **adduction** of the ipsilateral eye that is impaired, and the contralateral eye typically **abducts normally** but with nystagmus. *Proptosis of the right eye* - **Proptosis** (exophthalmos) is the bulging of the eye from the orbit, usually caused by retro-orbital mass lesions (e.g., **thyroid eye disease**, orbital tumors) or inflammation. - This finding is unrelated to the neurological lesion causing an INO.

Question 9: 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

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.

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

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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