Ultimate Neuroanatomy & Neurology Practice
Examination 2026 | Preparation | Advanced
Clinical Reasoning & Neurological Localization
Questions
1. A 68-year-old man suddenly develops weakness of the right
face, arm, and leg accompanied by hemisensory loss and a
right homonymous hemianopia. He has no aphasia, neglect, or
cortical sensory deficits. MRI demonstrates a small infarct
involving the left posterior limb of the internal capsule and
adjacent thalamus. Which vascular territory is most likely
compromised?
A. Anterior cerebral artery
B. Middle cerebral artery superior division
C. Thalamogeniculate and lenticulostriate perforating
branches of the posterior circulation
D. Posterior cerebral artery cortical branches
Answer: C
Rationale: The combination of dense contralateral motor and
sensory deficits with a homonymous visual field defect suggests
involvement of compact subcortical pathways in the internal
,capsule and adjacent thalamus. Small penetrating vessels—
including lenticulostriate and thalamic perforators—can
produce severe deficits without cortical signs. A large MCA
cortical infarction would more commonly produce aphasia or
neglect depending on hemispheric dominance.
2. A 24-year-old woman develops diplopia, ipsilateral ptosis,
and a dilated pupil. The affected eye is deviated "down and
out." She also has contralateral hemiparesis. Where is the
lesion most likely located?
A. Cavernous sinus
B. Superior orbital fissure
C. Midbrain cerebral peduncle involving CN III fascicles
D. Lateral medulla
Answer: C
Rationale: Ipsilateral oculomotor nerve palsy combined with
contralateral corticospinal tract weakness is characteristic of a
midbrain lesion involving CN III fascicles and the cerebral
peduncle. This classic crossed brainstem syndrome is often
termed Weber syndrome. A cavernous sinus lesion would affect
multiple cranial nerves but would not produce contralateral
hemiparesis.
,3. A patient has loss of pain and temperature sensation on the
right side of the body and loss of pain and temperature
sensation on the left side of the face. He also has ipsilateral
Horner syndrome, dysphagia, hoarseness, and ataxia. Which
structure is most likely involved?
A. Medial lemniscus
B. Corticospinal tract
C. Lateral medulla
D. Medial pons
Answer: C
Rationale: This is the classic pattern of lateral medullary
(Wallenberg) syndrome. Damage to the spinal trigeminal
nucleus causes ipsilateral facial pain and temperature loss,
while interruption of the spinothalamic tract causes
contralateral body pain and temperature loss. Nucleus
ambiguus involvement produces dysphagia and hoarseness,
while descending sympathetic fibers produce ipsilateral Horner
syndrome.
4. A patient develops sudden inability to abduct the right eye.
Examination reveals horizontal diplopia that worsens when
looking to the right. The lesion is most likely located in which
structure?
, A. Oculomotor nucleus
B. Medial longitudinal fasciculus
C. Abducens nerve or nucleus
D. Trochlear nerve
Answer: C
Rationale: CN VI innervates the lateral rectus muscle, which
abducts the eye. A CN VI lesion causes impaired ipsilateral eye
abduction and horizontal diplopia, especially when looking
toward the affected side. A medial longitudinal fasciculus lesion
instead produces internuclear ophthalmoplegia with impaired
adduction.
5. A 32-year-old woman develops episodes of neurologic
dysfunction separated by several months. MRI reveals
multiple periventricular, juxtacortical, infratentorial, and
spinal cord lesions, some enhancing with gadolinium and
others not. Which pathophysiologic process best explains this
pattern?
A. Degeneration of anterior horn cells
B. Peripheral nerve demyelination
C. CNS inflammatory demyelination with dissemination in
time and space
D. Primary degeneration of basal ganglia neurons
Examination 2026 | Preparation | Advanced
Clinical Reasoning & Neurological Localization
Questions
1. A 68-year-old man suddenly develops weakness of the right
face, arm, and leg accompanied by hemisensory loss and a
right homonymous hemianopia. He has no aphasia, neglect, or
cortical sensory deficits. MRI demonstrates a small infarct
involving the left posterior limb of the internal capsule and
adjacent thalamus. Which vascular territory is most likely
compromised?
A. Anterior cerebral artery
B. Middle cerebral artery superior division
C. Thalamogeniculate and lenticulostriate perforating
branches of the posterior circulation
D. Posterior cerebral artery cortical branches
Answer: C
Rationale: The combination of dense contralateral motor and
sensory deficits with a homonymous visual field defect suggests
involvement of compact subcortical pathways in the internal
,capsule and adjacent thalamus. Small penetrating vessels—
including lenticulostriate and thalamic perforators—can
produce severe deficits without cortical signs. A large MCA
cortical infarction would more commonly produce aphasia or
neglect depending on hemispheric dominance.
2. A 24-year-old woman develops diplopia, ipsilateral ptosis,
and a dilated pupil. The affected eye is deviated "down and
out." She also has contralateral hemiparesis. Where is the
lesion most likely located?
A. Cavernous sinus
B. Superior orbital fissure
C. Midbrain cerebral peduncle involving CN III fascicles
D. Lateral medulla
Answer: C
Rationale: Ipsilateral oculomotor nerve palsy combined with
contralateral corticospinal tract weakness is characteristic of a
midbrain lesion involving CN III fascicles and the cerebral
peduncle. This classic crossed brainstem syndrome is often
termed Weber syndrome. A cavernous sinus lesion would affect
multiple cranial nerves but would not produce contralateral
hemiparesis.
,3. A patient has loss of pain and temperature sensation on the
right side of the body and loss of pain and temperature
sensation on the left side of the face. He also has ipsilateral
Horner syndrome, dysphagia, hoarseness, and ataxia. Which
structure is most likely involved?
A. Medial lemniscus
B. Corticospinal tract
C. Lateral medulla
D. Medial pons
Answer: C
Rationale: This is the classic pattern of lateral medullary
(Wallenberg) syndrome. Damage to the spinal trigeminal
nucleus causes ipsilateral facial pain and temperature loss,
while interruption of the spinothalamic tract causes
contralateral body pain and temperature loss. Nucleus
ambiguus involvement produces dysphagia and hoarseness,
while descending sympathetic fibers produce ipsilateral Horner
syndrome.
4. A patient develops sudden inability to abduct the right eye.
Examination reveals horizontal diplopia that worsens when
looking to the right. The lesion is most likely located in which
structure?
, A. Oculomotor nucleus
B. Medial longitudinal fasciculus
C. Abducens nerve or nucleus
D. Trochlear nerve
Answer: C
Rationale: CN VI innervates the lateral rectus muscle, which
abducts the eye. A CN VI lesion causes impaired ipsilateral eye
abduction and horizontal diplopia, especially when looking
toward the affected side. A medial longitudinal fasciculus lesion
instead produces internuclear ophthalmoplegia with impaired
adduction.
5. A 32-year-old woman develops episodes of neurologic
dysfunction separated by several months. MRI reveals
multiple periventricular, juxtacortical, infratentorial, and
spinal cord lesions, some enhancing with gadolinium and
others not. Which pathophysiologic process best explains this
pattern?
A. Degeneration of anterior horn cells
B. Peripheral nerve demyelination
C. CNS inflammatory demyelination with dissemination in
time and space
D. Primary degeneration of basal ganglia neurons
