A 55-year-old construction worker falls off a 2-story scaffolding and injures his back. His coworkers bring him to the urgent care clinic within 30 minutes of the fall. He complains of left lower-limb weakness and loss of sensation in the right lower limb. He does not have any past medical history. His vital signs are stable. A neurologic examination reveals a total loss of motor function when testing left knee extension, along with the left-sided loss of light touch sensation from the mid-thigh and below. There is a right-sided loss of pin-prick sensation of the lateral leg and entire foot. At this time of acute injury, what other finding is most likely to be found in this patient?
Q12
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?
Q13
An otherwise healthy 58-year-old man comes to the physician because of a 1-year history of episodic coughing whenever he cleans his left ear. There is no history of hearing loss, tinnitus, or vertigo. Stimulating his left ear canal with a cotton swab triggers a bout of coughing. The physician informs him that these symptoms are caused by hypersensitivity of a cranial nerve. A peripheral lesion of this nerve is most likely to manifest with which of the following findings on physical examination?
Q14
A 25-year-old woman presents to the physician with a complaint of several episodes of headaches in the past 4 weeks that are affecting her school performance. These episodes are getting progressively worse, and over-the-counter medications do not seem to help. She also mentions having to raise her head each time to look at the board while taking notes; she cannot simply glance up with just her eyes. She has no significant past medical or family history and was otherwise well prior to this visit. Physical examination shows an upward gaze palsy and convergence-retraction nystagmus. What structure is most likely to be affected in this patient?
Q15
A 78-year-old woman is accompanied by her family for a routine visit to her primary care provider. The family states that 5 months prior, the patient had a stroke and is currently undergoing physical therapy. Today, her temperature is 98.2°F (36.8°C), blood pressure is 112/72 mmHg, pulse is 64/min, and respirations are 12/min. On exam, she is alert and oriented with no deficits in speech. Additionally, her strength and sensation are symmetric and preserved bilaterally. However, on further neurologic testing, she appears to have some difficulty with balance and a propensity to fall to her right side. Which of the following deficits does the patient also likely have?
Q16
A previously well 25-year-old woman was brought to the emergency department by her boyfriend because of progressive blurred vision. Examination of the eyes reveals loss of horizontal gaze, intact convergence, and nystagmus. A clinical diagnosis of multiple sclerosis is made and the patient is started on a course of corticosteroids. What is the most likely etiology for her eye examination findings?
Q17
A 21-year-old male presents to the ED with a stab wound to the right neck. The patient is alert and responsive, and vital signs are stable. Which of the following neurologic findings would most likely support the diagnosis of right-sided spinal cord hemisection?
Q18
A 63-year-old man presents to the clinic concerned about numbness and weakness in his bilateral shoulders and arms for the past 8 weeks. The symptoms started when he fell from scaffolding at work and landed on his back. Initial workup was benign and he returned to normal duty. However, his symptoms have progressively worsened since the fall. He denies fever, back pain, preceding vomiting, and diarrhea. He has a history of type 2 diabetes mellitus, hypertension, hypercholesterolemia, ischemic heart disease, and a 48-pack-year cigarette smoking history. He takes atorvastatin, hydrochlorothiazide, lisinopril, labetalol, and metformin. His blood pressure is 132/82 mm Hg, the pulse is 72/min, and the respiratory rate is 15/min. All cranial nerves are intact. Muscle strength is reduced in the upper limbs (4/5 bilaterally) but normal in the lower limbs. Perception of sharp stimuli and temperature is reduced on his shoulders and upper arms. The vibratory sense is preserved. Sensory examination is normal in the lower limbs. What is the most likely diagnosis?
Q19
A 22-year-old man is brought to the emergency department after he was impaled by a metal rod during a work accident. The rod went into his back around the level of T9 but was removed before arrival. He has no past medical history and does not take any medications. On physical examination, he has significant muscle weakness in his entire left lower body. He also exhibits impaired vibration and proprioception in his left leg as well as loss of pain and temperature sensation in his right leg. Which of the following sections of the spinal cord was most likely damaged in this patient?
Q20
An 8-year-old boy is brought to the physician by his mother because of a 3-week history of irritability and frequent bed wetting. She also reports that he has been unable to look upward without tilting his head back for the past 2 months. He is at the 50th percentile for height and weight. His vital signs are within normal limits. Ophthalmological examination shows dilated pupils that are not reactive to light and bilateral optic disc swelling. Pubic hair development is Tanner stage 2. The most likely cause of this patient's condition is a tumor in which of the following locations?
Neuroanatomy US Medical PG Practice Questions and MCQs
Question 11: A 55-year-old construction worker falls off a 2-story scaffolding and injures his back. His coworkers bring him to the urgent care clinic within 30 minutes of the fall. He complains of left lower-limb weakness and loss of sensation in the right lower limb. He does not have any past medical history. His vital signs are stable. A neurologic examination reveals a total loss of motor function when testing left knee extension, along with the left-sided loss of light touch sensation from the mid-thigh and below. There is a right-sided loss of pin-prick sensation of the lateral leg and entire foot. At this time of acute injury, what other finding is most likely to be found in this patient?
A. Left-sided extensor plantar response
B. Intact voluntary anal contraction
C. Left-sided spastic paralysis below the lesion
D. Left-sided numbness at the level of the lesion
E. Left-sided loss of proprioception and vibration sensation (Correct Answer)
Explanation: ***Left-sided loss of proprioception and vibration sensation***
- The presented symptoms (left lower-limb weakness/motor loss, left-sided loss of light touch, and right-sided loss of pin-prick sensation) are classic for **Brown-Séquard syndrome**, resulting from a **hemicord lesion on the LEFT side**.
- **Proprioception** and **vibration sensation** are carried by the **dorsal columns**, which ascend **ipsilaterally** (same side) in the spinal cord and decussate in the **medulla** (lower brainstem).
- Therefore, a lesion on the **left side** of the spinal cord would result in **ipsilateral (left-sided) loss** of proprioception and vibration sensation below the level of the lesion.
- The right-sided loss of pain/temperature occurs because the spinothalamic tract decussates at the spinal level of entry, making pain/temperature deficits contralateral to the lesion.
*Left-sided extensor plantar response*
- An **extensor plantar response (Babinski sign)**, indicating an upper motor neuron lesion, is typically present in the **chronic phase** of spinal cord injury.
- In the **acute phase (spinal shock)**, **flaccid paralysis** and **absent reflexes** are more common, not hyperreflexia or Babinski signs.
*Intact voluntary anal contraction*
- **Voluntary anal contraction** indicates preserved sacral spinal cord function, which is assessed to determine if an injury is **complete or incomplete**.
- Given the severe motor and sensory deficits described, this would suggest an incomplete lesion, but the classic Brown-Séquard presentation makes this less likely as the primary finding.
*Left-sided spastic paralysis below the lesion*
- **Spastic paralysis** is a sign of an upper motor neuron lesion that emerges **weeks to months** after the initial injury, typically after spinal shock resolves.
- In the **acute phase (spinal shock)**, the patient would experience **flaccid paralysis** and hyporeflexia below the level of the lesion.
*Left-sided numbness at the level of the lesion*
- Sensory loss **at the level of the lesion** can occur due to damage to the dorsal horn at that specific spinal segment.
- However, the question describes **left-sided loss of light touch from the mid-thigh down**, which represents loss **below** the lesion level.
- **Brown-Séquard syndrome** can cause a narrow band of bilateral sensory loss at the lesion level, but the most clinically significant and testable finding in the acute phase is the **ipsilateral loss of proprioception and vibration** below the lesion.
Question 12: 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 13: An otherwise healthy 58-year-old man comes to the physician because of a 1-year history of episodic coughing whenever he cleans his left ear. There is no history of hearing loss, tinnitus, or vertigo. Stimulating his left ear canal with a cotton swab triggers a bout of coughing. The physician informs him that these symptoms are caused by hypersensitivity of a cranial nerve. A peripheral lesion of this nerve is most likely to manifest with which of the following findings on physical examination?
A. Ipsilateral sensorineural hearing loss
B. Ipsilateral deviation of the tongue
C. Inability to raise ipsilateral eyebrow
D. Decreased secretion from ipsilateral sublingual gland
E. Ipsilateral vocal cord palsy (Correct Answer)
Explanation: ***Ipsilateral vocal cord palsy***
- The sensation in the external auditory canal that triggers a cough reflex is mediated by the **auricular branch of the vagus nerve (CN X)**, also known as Arnold's nerve.
- A peripheral lesion of the vagus nerve would most likely affect its motor functions, including the innervation of the **larynx**, leading to **ipsilateral vocal cord palsy** and hoarseness.
*Ipsilateral sensorineural hearing loss*
- Hearing loss is primarily associated with pathology of the **vestibulocochlear nerve (CN VIII)**, not the vagus nerve.
- The patient's presentation does not describe any auditory symptoms.
*Ipsilateral deviation of the tongue*
- Tongue deviation is a sign of compromise of the **hypoglossal nerve (CN XII)**, which controls the intrinsic and extrinsic muscles of the tongue.
- This is not a function of the vagus nerve.
*Inability to raise ipsilateral eyebrow*
- The ability to raise the eyebrow is controlled by the **facial nerve (CN VII)**, which innervates the muscles of facial expression.
- Vagus nerve lesions do not typically present with facial weakness.
*Decreased secretion from ipsilateral sublingual gland*
- Secretion from the sublingual gland is controlled by the **facial nerve (CN VII)** via the submandibular ganglion.
- While the vagus nerve has autonomic functions, it does not directly control sublingual gland secretion.
Question 14: A 25-year-old woman presents to the physician with a complaint of several episodes of headaches in the past 4 weeks that are affecting her school performance. These episodes are getting progressively worse, and over-the-counter medications do not seem to help. She also mentions having to raise her head each time to look at the board while taking notes; she cannot simply glance up with just her eyes. She has no significant past medical or family history and was otherwise well prior to this visit. Physical examination shows an upward gaze palsy and convergence-retraction nystagmus. What structure is most likely to be affected in this patient?
A. Aqueduct of Sylvius
B. Inferior colliculi
C. 3rd ventricle
D. Tegmentum
E. Corpora quadrigemina (Correct Answer)
Explanation: ***Corpora quadrigemina***
- The patient presents with classic **Parinaud syndrome** (dorsal midbrain syndrome), characterized by **upward gaze palsy** and **convergence-retraction nystagmus**.
- These specific oculomotor signs result from direct damage to the **superior colliculi** and **pretectal area**, which are anatomical components of the **corpora quadrigemina** in the tectal region of the midbrain.
- The superior colliculi control vertical gaze, and the pretectal area coordinates pupillary reflexes and convergence movements. Compression or infiltration of this region (commonly by pineal tumors) produces the characteristic eye movement abnormalities.
- Progressive headaches indicate increased intracranial pressure, often from associated **aqueduct obstruction** causing hydrocephalus, which in turn compresses the tectal structures.
*Aqueduct of Sylvius*
- While obstruction of the aqueduct of Sylvius commonly **causes** Parinaud syndrome by leading to hydrocephalus and mass effect, the aqueduct itself is a CSF pathway and does not directly produce the eye movement abnormalities.
- The question asks which structure is "**affected**" - the affected structure producing these specific symptoms is the tectal region (corpora quadrigemina), not the obstructed aqueduct.
- This is an important distinction: the aqueduct is obstructed, but the corpora quadrigemina is compressed/affected.
*Inferior colliculi*
- The inferior colliculi are part of the corpora quadrigemina but serve the **auditory pathway**, not visual or oculomotor functions.
- Isolated lesions here would cause hearing deficits, not upward gaze palsy or convergence-retraction nystagmus.
*3rd ventricle*
- Lesions obstructing the third ventricle can cause hydrocephalus and headaches but do not directly affect the midbrain tectum unless they extend posteriorly.
- Third ventricular masses more commonly produce **endocrine disturbances** (hypothalamic-pituitary axis dysfunction) rather than the specific dorsal midbrain syndrome seen here.
*Tegmentum*
- The tegmentum is the ventral portion of the midbrain containing the **red nucleus**, **substantia nigra**, and **cranial nerve nuclei (III, IV)**.
- Tegmental lesions produce different oculomotor deficits (e.g., internuclear ophthalmoplegia, third nerve palsy) and movement disorders, not the dorsal midbrain syndrome pattern of Parinaud.
Question 15: A 78-year-old woman is accompanied by her family for a routine visit to her primary care provider. The family states that 5 months prior, the patient had a stroke and is currently undergoing physical therapy. Today, her temperature is 98.2°F (36.8°C), blood pressure is 112/72 mmHg, pulse is 64/min, and respirations are 12/min. On exam, she is alert and oriented with no deficits in speech. Additionally, her strength and sensation are symmetric and preserved bilaterally. However, on further neurologic testing, she appears to have some difficulty with balance and a propensity to fall to her right side. Which of the following deficits does the patient also likely have?
A. Hemiballismus
B. Hemispatial neglect
C. Intention tremor
D. Contralateral eye deviation
E. Truncal ataxia (Correct Answer)
Explanation: ***Truncal ataxia***
- This patient's symptoms of **difficulty with balance** and a **propensity to fall to her right side** are highly suggestive of truncal ataxia.
- While she had a stroke, her preserved speech, symmetric strength and sensation, and alertness rule out typical hemiparesis or aphasia, pointing towards a **cerebellar lesion** affecting balance and coordination.
*Hemiballismus*
- This condition involves **flailing, high-amplitude, involuntary movements** typically affecting one side of the body.
- The patient's description of balance issues and falling, without mention of such specific movements, makes hemiballismus less likely.
*Hemispatial neglect*
- Characterized by the **inability to attend to one side of the environment**, usually the left side following a right parietal stroke.
- The patient's presentation does not describe an indifference to one side of her visual or personal space.
*Intention tremor*
- An **intention tremor** is a tremor that worsens during purposeful movement towards a target.
- While it can be associated with cerebellar dysfunction, the primary deficit described is imbalance and falling to one side, not specifically a tremor.
*Contralateral eye deviation*
- This typically occurs in acute stroke scenarios as part of a **gaze preference**, where the eyes deviate towards the side of the lesion (or away from the hemiparesis).
- The patient is 5 months post-stroke and is alert with no acute focal deficits, making acute eye deviation unlikely as a chronic presenting symptom here.
Question 16: A previously well 25-year-old woman was brought to the emergency department by her boyfriend because of progressive blurred vision. Examination of the eyes reveals loss of horizontal gaze, intact convergence, and nystagmus. A clinical diagnosis of multiple sclerosis is made and the patient is started on a course of corticosteroids. What is the most likely etiology for her eye examination findings?
A. Loss of reticular formations
B. Loss of bilateral medial longitudinal fasciculus (Correct Answer)
C. Loss of frontal eye fields
D. Loss of cranial nerve VI
E. Loss of cranial nerve III
Explanation: ***Loss of bilateral medial longitudinal fasciculus***
- This constellation of symptoms, including **loss of horizontal gaze (specifically adduction deficits)** with intact convergence and nystagmus, is characteristic of **internuclear ophthalmoplegia (INO)**.
- INO is caused by a lesion in the **medial longitudinal fasciculus (MLF)**, which connects the abducens nucleus (CN VI) to the contralateral oculomotor nucleus (CN III) to coordinate horizontal gaze.
- **Bilateral MLF involvement** is highly characteristic of **multiple sclerosis** in young adults, particularly young women, as demyelinating plaques frequently affect these structures in the brainstem.
- The key clinical finding is **impaired adduction on attempted lateral gaze** with **contralateral abducting nystagmus**, while **convergence remains intact** (since convergence uses a different pathway).
*Loss of reticular formations*
- Damage to the **pontine reticular formation** (paramedian pontine reticular formation or PPRF) would typically lead to a **conjugate gaze palsy** (inability to move both eyes past the midline) rather than INO.
- This would affect both eyes moving together in the same direction, not the dissociated eye movements seen in INO.
*Loss of frontal eye fields*
- Lesions in the **frontal eye fields** (Brodmann area 8) result in a temporary **conjugate gaze deviation** towards the side of the lesion and an inability to perform voluntary saccades to the contralateral side.
- This does not explain the specific findings of adduction deficit in one eye with preserved convergence.
*Loss of cranial nerve VI*
- A lesion of **cranial nerve VI (abducens nerve)** would cause paralysis of the **lateral rectus muscle**, leading to an inability to **abduct** the affected eye and potentially esotropia.
- It would not cause an **adduction deficit** or the dissociated eye movements characteristic of INO.
*Loss of cranial nerve III*
- A lesion of **cranial nerve III (oculomotor nerve)** would result in a drooping eyelid (**ptosis**), outward and downward deviation of the eye, and pupillary dilation.
- This is a much more extensive deficit than the specific adduction problems described, and the pupillary findings are absent.
Question 17: A 21-year-old male presents to the ED with a stab wound to the right neck. The patient is alert and responsive, and vital signs are stable. Which of the following neurologic findings would most likely support the diagnosis of right-sided spinal cord hemisection?
A. Left-sided tactile, vibration, and proprioception loss; right-sided pain and temperature sensation loss; left-sided paresis
B. Right-sided tactile, vibration, and proprioception loss; left-sided pain and temperature sensation loss; right-sided paresis (Correct Answer)
C. Right-sided tactile, vibration, and proprioception loss; right-sided pain and temperature sensation loss; right-sided paresis
D. Bilateral tactile, vibration, and proprioception loss; bilateral pain and temperature sensation loss; bilateral paresis
E. Right-sided tactile, vibration, and proprioception loss; left-sided pain and temperature sensation loss; left-sided paresis
Explanation: ***Right-sided tactile, vibration, and proprioception loss; left-sided pain and temperature sensation loss; right-sided paresis***
- This symptom complex describes **Brown-Séquard syndrome**, resulting from a **hemisection of the spinal cord**, where the damage affects one side.
- On the ipsilateral side (same side as the lesion), there is a loss of **motor function (paresis/paralysis)** and **proprioception**, **vibration**, and **fine touch sensation** due to damage to the **corticospinal tract** and **dorsal columns**.
- On the contralateral side (opposite side of the lesion), there is a loss of **pain** and **temperature sensation** because the **spinothalamic tracts** cross over lower down in the spinal cord and ascend on the opposite side.
*Left-sided tactile, vibration, and proprioception loss; right-sided pain and temperature sensation loss; left-sided paresis*
- This pattern suggests a **left-sided hemisection**, as the motor and dorsal column deficits are ipsilateral to the lesion, and pain/temperature loss is contralateral.
- The question specifies a **right-sided spinal cord hemisection**, so the motor and proprioceptive deficits should be on the right.
*Right-sided tactile, vibration, and proprioception loss; right-sided pain and temperature sensation loss; right-sided paresis*
- This pattern would indicate ipsilateral loss of **all sensory modalities** (pain, temperature, touch, proprioception) along with motor deficit.
- This is not consistent with a hemisection because **pain and temperature pathways (spinothalamic tracts) cross over** at the level of entry, meaning their loss would be contralateral to the lesion.
*Right-sided tactile, vibration, and proprioception loss, left-sided pain and temperature sensation loss; left-sided paresis*
- This combination presents a mixed picture where tactile and proprioception loss is ipsilateral, pain and temperature loss is contralateral, but **paresis is also contralateral**.
- According to Brown-Séquard syndrome, **motor deficit (paresis)** should be ipsilateral to the lesion due to damage to the corticospinal tract before decussation in the medulla.
*Bilateral tactile, vibration, and proprioception loss; bilateral pain and temperature sensation loss; bilateral paresis*
- This describes a **complete spinal cord transection** or a highly severe, **bilateral injury** affecting both sides of the cord.
- A hemisection, by definition, implies damage to only **one side** of the spinal cord, leading to more specific, asymmetric deficits.
Question 18: A 63-year-old man presents to the clinic concerned about numbness and weakness in his bilateral shoulders and arms for the past 8 weeks. The symptoms started when he fell from scaffolding at work and landed on his back. Initial workup was benign and he returned to normal duty. However, his symptoms have progressively worsened since the fall. He denies fever, back pain, preceding vomiting, and diarrhea. He has a history of type 2 diabetes mellitus, hypertension, hypercholesterolemia, ischemic heart disease, and a 48-pack-year cigarette smoking history. He takes atorvastatin, hydrochlorothiazide, lisinopril, labetalol, and metformin. His blood pressure is 132/82 mm Hg, the pulse is 72/min, and the respiratory rate is 15/min. All cranial nerves are intact. Muscle strength is reduced in the upper limbs (4/5 bilaterally) but normal in the lower limbs. Perception of sharp stimuli and temperature is reduced on his shoulders and upper arms. The vibratory sense is preserved. Sensory examination is normal in the lower limbs. What is the most likely diagnosis?
A. Anterior cord syndrome
B. Central cord syndrome (Correct Answer)
C. Guillain-Barre syndrome
D. Vitamin B12 deficiency
E. Pontine infarction
Explanation: ***Central cord syndrome***
- This syndrome typically results from a **hyperextension injury** in patients with pre-existing cervical spinal stenosis, leading to damage to the central gray matter and surrounding tracts.
- It classically presents with greater **motor weakness in the upper extremities** than in the lower extremities, and a **"cape-like" distribution of sensory loss** (impaired pain and temperature sensation) over the shoulders and arms due to spinothalamic tract involvement, as seen in this patient.
*Anterior cord syndrome*
- This syndrome is characterized by **paraplegia/quadriplegia**, dissociated sensory loss (loss of **pain and temperature sensation**), and bowel/bladder dysfunction below the level of the lesion.
- It spares **proprioception and vibratory sensation** since the posterior columns remain intact, which is not fully consistent with the patient's presentation of primarily sensory symptoms in the upper limbs with normal strength.
*Guillain-Barre syndrome*
- This is an **acute demyelinating polyneuropathy** that typically presents with **progressive, ascending weakness** and often **areflexia**, usually following an infection.
- The patient's symptoms are primarily sensory, descending, and lack significant weakness or preceding infection, making this diagnosis less likely.
*Vitamin B12 deficiency*
- This deficiency can cause **subacute combined degeneration** of the spinal cord, affecting the **posterior columns** (vibratory and proprioception loss) and **corticospinal tracts** (weakness, spasticity).
- The patient primarily has loss of pain and temperature sensation with preserved vibratory sense and normal strength, which is inconsistent with B12 deficiency.
*Pontine infarction*
- A pontine infarction would present with a constellation of cranial nerve deficits, motor weakness (hemiparesis or quadriplegia), and cerebellar signs due to its location in the brainstem.
- The patient has intact cranial nerves, normal muscle strength, and specific sensory deficits limited to the shoulders and arms, which does not align with a brainstem stroke.
Question 19: A 22-year-old man is brought to the emergency department after he was impaled by a metal rod during a work accident. The rod went into his back around the level of T9 but was removed before arrival. He has no past medical history and does not take any medications. On physical examination, he has significant muscle weakness in his entire left lower body. He also exhibits impaired vibration and proprioception in his left leg as well as loss of pain and temperature sensation in his right leg. Which of the following sections of the spinal cord was most likely damaged in this patient?
A. Posterior cord
B. Anterior cord
C. Left hemicord (Correct Answer)
D. Central cord
E. Right hemicord
Explanation: ***Left hemicord***
- The combination of **ipsilateral motor weakness** and **loss of vibration/proprioception** (damage to the **corticospinal tract** and **dorsal column**) along with **contralateral loss of pain/temperature** (damage to the **spinothalamic tract**) is the classic presentation of **Brown-Séquard syndrome**, which results from a lesion affecting one side (hemicord) of the spinal cord.
- The injury at **T9** is consistent with lower body symptoms, as tracts for the legs would be affected at this level.
*Posterior cord*
- Damage to the **posterior cord** primarily affects the **dorsal columns**, leading to **ipsilateral loss of vibration and proprioception**.
- It would not explain the **ipsilateral motor weakness** or the **contralateral loss of pain and temperature sensation**.
*Anterior cord*
- **Anterior cord syndrome** typically presents with **bilateral loss of motor function** (due to damage to the corticospinal tracts) and **bilateral loss of pain and temperature sensation** (due to damage to the spinothalamic tracts).
- **Vibration and proprioception** are usually preserved because the dorsal columns are spared.
*Central cord*
- **Central cord syndrome** most commonly results from hyperextension injuries, particularly in the cervical spine, affecting the central gray matter.
- It typically causes greater **weakness in the upper extremities** than the lower extremities and a variable sensory loss, often in a **"cape-like" distribution**.
*Right hemicord*
- A **right hemicord** lesion would cause **right-sided motor weakness** and **loss of vibration/proprioception**, along with **left-sided loss of pain/temperature sensation**.
- The patient's symptoms are on the **left side for motor/proprioception** and the **right side for pain/temperature**, indicating a left hemicord lesion.
Question 20: An 8-year-old boy is brought to the physician by his mother because of a 3-week history of irritability and frequent bed wetting. She also reports that he has been unable to look upward without tilting his head back for the past 2 months. He is at the 50th percentile for height and weight. His vital signs are within normal limits. Ophthalmological examination shows dilated pupils that are not reactive to light and bilateral optic disc swelling. Pubic hair development is Tanner stage 2. The most likely cause of this patient's condition is a tumor in which of the following locations?
A. Fourth ventricle
B. Sella turcica
C. Cerebellar vermis
D. Cerebral falx
E. Dorsal midbrain (Correct Answer)
Explanation: ***Dorsal midbrain***
- The inability to look upward (**Parinaud's syndrome**), dilated pupils with poor light reflex, and **optic disc swelling** (indicating increased intracranial pressure) are classic signs of a mass lesion compressing the **dorsal midbrain**, specifically the **tectal plate**.
- **Irritability and bedwetting** are nonspecific symptoms, but in this context, they could be related to **hydrocephalus** due to **aqueductal compression** by the tumor.
*Fourth ventricle*
- Tumors of the fourth ventricle typically present with symptoms related to **hydrocephalus** (headache, nausea, vomiting, papilledema) and **ataxia** due to cerebellar involvement, but not specifically with **Parinaud's syndrome**.
- **Truncal ataxia** and **gait instability** are common with posterior fossa tumors affecting the cerebellum.
*Sella turcica*
- Tumors in the sella turcica primarily affect the **pituitary gland** and **optic chiasm**, leading to **endocrine dysfunction** (e.g., growth retardation, precocious puberty, hypogonadism) and **bitemporal hemianopsia**.
- **Parinaud's syndrome** and **dilated, unreactive pupils** are not typical presentations for sellar tumors.
*Cerebral falx*
- Tumors associated with the cerebral falx (e.g., meningiomas) are often located **supratentorially** and can cause focal neurological deficits like **seizures** or **hemiparesis**, depending on their location and size.
- They do not typically cause the specific eye movement disorders or pupillary abnormalities seen in this patient.
*Cerebellar vermis*
- Cerebellar vermis tumors often lead to **truncal ataxia**, **gait disturbance**, and **hydrocephalus** due to compression of the aqueduct or fourth ventricle outflow.
- While they can cause increased intracranial pressure, they do not directly cause **Parinaud's syndrome** or isolated deficits of upward gaze.
