USMLE Step 2 Quiz: Localization And Neurologic Examination
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Localization And Neurologic ExaminationQuestion 1 of 20

A 55-year-old woman is evaluated for new-onset neurologic deficits. Physical examination reveals weakness of the right lower face, arm, and leg. She has a loss of proprioception and vibration sense in the right arm and leg. She has a loss of pain and temperature sensation in the left arm and leg. Which of the following is the most likely location of the lesion?

Which of the following is the most likely location of the lesion?

Left thalamus
Right spinal cord at C5
Left medial medulla
Right pons
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USMLE Step 2 Quiz

USMLE Step 2 Quiz: Localization And Neurologic Examination

Practice Localization And Neurologic Examination in USMLE Step 2 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

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This quiz focuses on Localization And Neurologic Examination, giving you a quick way to practice the rules, question types, and explanations that matter most for USMLE Step 2.

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Question 1

A 55-year-old woman is evaluated for new-onset neurologic deficits. Physical examination reveals weakness of the right lower face, arm, and leg. She has a loss of proprioception and vibration sense in the right arm and leg. She has a loss of pain and temperature sensation in the left arm and leg. Which of the following is the most likely location of the lesion?

Which of the following is the most likely location of the lesion?

  1. Left thalamus
  2. Right spinal cord at C5 (correct answer)
  3. Left medial medulla
  4. Right pons
Explanation: This patient's findings are classic for Brown-Séquard syndrome (spinal cord hemisection). The lesion is on the right side at the C5 level, causing ipsilateral (right-sided) motor weakness (corticospinal tract) and loss of proprioception/vibration (dorsal columns), and contralateral (left-sided) loss of pain and temperature (spinothalamic tract, which decussates at the level of the cord).

Question 2

A 68-year-old man with a history of hypertension and type 2 diabetes mellitus is brought to the emergency department after his wife noted a sudden onset of neurologic symptoms. On examination, he has a drooped left eyelid and his left eye is deviated down and out. His left pupil is dilated and nonreactive to light. He also has weakness of his right arm and right leg. Sensation is intact throughout. Which of the following is the most likely location of the lesion responsible for his symptoms?

Which of the following is the most likely location of the lesion responsible for this patient's symptoms?

  1. Left cerebral peduncle of the midbrain (correct answer)
  2. Right medial pons
  3. Left lateral medulla
  4. Right internal capsule
Explanation: This patient presents with a left oculomotor nerve (CN III) palsy (ptosis, 'down and out' gaze, mydriasis) and contralateral (right-sided) hemiparesis. This constellation of findings is characteristic of Weber syndrome, which is caused by a lesion in the left cerebral peduncle of the midbrain, affecting the exiting CN III fascicles and the adjacent corticospinal tract.

Question 3

A 72-year-old right-handed man is brought to the hospital after a stroke. He is alert and follows commands. His speech is fluent but nonsensical, with frequent word substitutions. He has difficulty comprehending simple spoken and written commands. On examination, he also has a right superior quadrantanopia. Motor strength and sensation are intact. Where is the lesion most likely located?

Where is the lesion most likely located?

  1. Left frontal lobe
  2. Right parietal lobe
  3. Left temporal lobe (correct answer)
  4. Right occipital lobe
Explanation: This patient has fluent (Wernicke's) aphasia, characterized by impaired comprehension and fluent but meaningless speech. This localizes to Wernicke's area in the dominant (usually left) superior temporal gyrus. The associated right superior quadrantanopia ('pie in the sky') is caused by involvement of the lower optic radiation (Meyer's loop), which also passes through the temporal lobe.

Question 4

A 75-year-old man presents with vertigo, nausea, and difficulty swallowing. On neurologic examination, he has decreased pain and temperature sensation on the right side of his face and the left side of his body. He has hoarseness and a diminished gag reflex on the right. He also exhibits ataxia of his right arm and leg and has a right-sided Horner syndrome (ptosis, miosis). Which of the following locations best explains this patient's presentation?

Which of the following locations best explains this patient's presentation?

  1. Right cerebellar hemisphere
  2. Left midbrain
  3. Right lateral medulla (correct answer)
  4. Left internal capsule
Explanation: This is a classic presentation of Wallenberg syndrome, or lateral medullary syndrome, typically caused by an occlusion of the posterior inferior cerebellar artery (PICA). The lesion in the right lateral medulla affects the spinal trigeminal nucleus (ipsilateral face sensation), spinothalamic tract (contralateral body sensation), nucleus ambiguus (dysphagia, hoarseness), inferior cerebellar peduncle (ipsilateral ataxia), and descending sympathetic fibers (ipsilateral Horner syndrome).

Question 5

A 30-year-old woman comes to the office because of facial weakness that started this morning. On examination, she has drooping of the left corner of her mouth. She is unable to close her left eye tightly or raise her left eyebrow. Her forehead is smooth on the left side when she attempts to look up. Sensation over her face is intact. The remainder of her neurologic exam is normal. A lesion in which of the following locations would best explain her symptoms?

A lesion in which of the following locations would best explain her symptoms?

  1. Right motor cortex
  2. Left facial nerve nucleus or nerve (correct answer)
  3. Right internal capsule
  4. Left trigeminal nerve
Explanation: This patient has a left-sided lower motor neuron (LMN) facial palsy, involving both the upper (forehead) and lower face. This localizes the lesion to the facial nerve nucleus in the pons or the peripheral facial nerve (CN VII) itself after it exits the brainstem. In contrast, an upper motor neuron (UMN) lesion, such as in the motor cortex or internal capsule, would spare the forehead due to bilateral cortical innervation of the upper face.

Question 6

A 66-year-old right-handed woman is evaluated after a stroke. Her family reports that she seems to ignore people and objects on her left side. On examination, when asked to draw a clock, she crams all the numbers into the right half. When asked to bisect a line, she marks it far to the right of the midpoint. She has mild left-sided weakness. What is the most likely location of this patient's lesion?

What is the most likely location of this patient's lesion?

  1. Right parietal lobe (correct answer)
  2. Left frontal lobe
  3. Corpus callosum
  4. Right temporal lobe
Explanation: This patient is demonstrating contralateral hemispatial neglect, a condition where she is unaware of or fails to attend to stimuli on the left side of her body and space. This is a classic sign of a lesion in the non-dominant (usually right) parietal lobe, which is responsible for spatial awareness and attention.

Question 7

A 58-year-old woman presents with double vision. On examination, she is unable to adduct her right eye on left lateral gaze. When looking to the right, her left eye does not adduct, and there is nystagmus of the abducting right eye. Convergence is intact. This patient's signs are best explained by a lesion in which of the following structures?

This patient's signs are best explained by a lesion in which of the following structures?

  1. Right oculomotor nerve (CN III)
  2. Left abducens nucleus (CN VI)
  3. Right medial longitudinal fasciculus (MLF) (correct answer)
  4. Optic chiasm
Explanation: This patient has internuclear ophthalmoplegia (INO) affecting the right eye's adduction. INO is caused by a lesion in the medial longitudinal fasciculus (MLF), a white matter tract that coordinates horizontal eye movements by connecting the contralateral abducens nucleus (CN VI) with the ipsilateral oculomotor nucleus (CN III). A lesion in the right MLF prevents the right medial rectus from firing when the left eye abducts, causing impaired adduction of the right eye on leftward gaze. The nystagmus in the abducting eye is also characteristic. Convergence is spared as it does not rely on the MLF.

Question 8

A 62-year-old right-handed man presents with difficulty speaking after an acute stroke. His speech is slow, effortful, and consists of short, agrammatical phrases. He appears frustrated by his inability to articulate his thoughts but seems to understand questions well and can follow complex commands. He also has weakness of the right side of his face and right arm. Where is the infarct most likely located?

Where is the infarct most likely located?

  1. Left inferior frontal gyrus (correct answer)
  2. Right superior temporal gyrus
  3. Left angular gyrus
  4. Right medial temporal lobe
Explanation: The patient's clinical presentation is consistent with Broca's aphasia, an expressive aphasia characterized by non-fluent, agrammatical speech with intact comprehension. This localizes the lesion to Broca's area, which is located in the inferior frontal gyrus of the dominant (usually left) hemisphere. The proximity of this area to the primary motor cortex explains the associated contralateral face and arm weakness.

Question 9

A 45-year-old woman with a history of pituitary adenoma presents with a severe headache, blurry vision, and double vision. On examination, she has ptosis of the left eyelid. Her left eye is deviated inferiorly and laterally. She has complete paralysis of adduction, elevation, and depression of the left eye. She also reports numbness over her left forehead and cheek. Her right eye movements are normal. Which of the following locations best explains this constellation of findings?

Which of the following locations best explains this constellation of findings?

  1. Left midbrain
  2. Left orbit
  3. Left cavernous sinus (correct answer)
  4. Brainstem tegmentum
Explanation: This patient has multiple cranial neuropathies affecting the left eye. The ptosis and 'down and out' gaze indicate a CN III palsy. The numbness over the forehead and cheek corresponds to the V1 and V2 divisions of the trigeminal nerve. The cavernous sinus is a unique anatomical space through which CN III, IV, VI, V1, and V2 travel. A single lesion here, such as from pituitary apoplexy or thrombosis, can affect all these nerves simultaneously.

Question 10

A 35-year-old man presents with a 6-month history of a 'clumsy' right hand and difficulty with balance. On examination, he has an intention tremor and dysmetria (past-pointing on finger-to-nose testing) with his right arm. When walking, he tends to sway and fall towards the right. His strength, sensation, and reflexes are normal. Where is the lesion most likely located?

Where is the lesion most likely located?

  1. Left basal ganglia
  2. Right cerebellar hemisphere (correct answer)
  3. Cervical spinal cord
  4. Left parietal lobe
Explanation: The patient's signs of ipsilateral limb ataxia (dysmetria, intention tremor) and truncal ataxia (falling to the right) are classic for a lesion in the right cerebellar hemisphere. The cerebellum is responsible for coordinating voluntary movements, posture, balance, and motor learning. Cerebellar lesions cause deficits on the same side of the body.

Question 11

A 65-year-old man is evaluated for an acute stroke. His neurologic examination is notable for dense weakness of the right face, arm, and leg. Sensation, including pain, temperature, vibration, and proprioception, is completely absent on the entire right side of his body. He has no aphasia, neglect, or visual field deficits. An MRI of the brain would most likely show an infarct in which location?

An MRI of the brain would most likely show an infarct in which location?

  1. Left parietal lobe
  2. Right midbrain
  3. Left posterolateral thalamus (correct answer)
  4. Left precentral gyrus
Explanation: This patient presents with a combined sensorimotor stroke affecting the left posterolateral thalamus. The thalamus contains both the ventral posterior lateral (VPL) and ventral posterior medial (VPM) nuclei, which relay sensory information, as well as motor relay nuclei. A strategic infarct in this region can cause both contralateral hemiparesis and complete sensory loss affecting all modalities on the face, arm, and leg. The absence of cortical signs (aphasia, neglect) helps localize this to a subcortical structure.

Question 12

A 59-year-old woman with a history of atrial fibrillation who is not on anticoagulation presents with acute onset of weakness. On examination, she has paralysis of her left face, arm, and leg, with equal severity in all three areas. Her speech, comprehension, and vision are entirely normal. She has no sensory deficits. This presentation is most characteristic of a lacunar infarct in which of the following locations?

This presentation is most characteristic of a lacunar infarct in which of the following locations?

  1. Right primary motor cortex
  2. Right posterior limb of the internal capsule (correct answer)
  3. Left medial lemniscus
  4. Right pons
Explanation: This is a classic 'pure motor stroke,' characterized by contralateral hemiparesis affecting the face, arm, and leg equally, without any sensory, visual, or cognitive deficits. This syndrome is caused by a small, deep lacunar infarct in the posterior limb of the internal capsule, where the corticospinal and corticobulbar motor fibers are densely packed. A cortical stroke would typically show disproportionate weakness (e.g., face/arm more than leg) and would likely have associated cortical signs (aphasia, neglect).

Question 13

A 50-year-old man presents with back pain radiating down his right leg. On examination, he has weakness of right foot dorsiflexion and great toe extension. His ankle reflex is normal, but he has difficulty walking on his right heel. There is sensory loss over the dorsum of his right foot and the first web space. A lesion affecting which of the following nerve roots is the most likely cause?

A lesion affecting which of the following nerve roots is the most likely cause?

  1. L3
  2. L4
  3. L5 (correct answer)
  4. S1
Explanation: The patient's symptoms localize to the L5 nerve root. Weakness of foot dorsiflexion and great toe extension is primarily an L5 myotome function. The sensory loss on the dorsum of the foot is consistent with the L5 dermatome. The ankle reflex (S1) is preserved, and weakness of knee extension (L4) is absent, making L5 the most likely affected root.

Question 14

A 77-year-old woman with a history of atrial fibrillation presents to the emergency department with vision changes. She reports that she suddenly cannot see anything on the right side. On examination, she has a right homonymous hemianopia. Pupillary light reflexes are normal. Notably, her central vision seems to be spared when tested with a central target. This specific visual field defect is most likely caused by an occlusion of which artery?

This specific visual field defect is most likely caused by an occlusion of which artery?

  1. Left middle cerebral artery
  2. Right middle cerebral artery
  3. Left posterior cerebral artery (correct answer)
  4. Right posterior cerebral artery
Explanation: A right homonymous hemianopia localizes the lesion to the left optic tract, optic radiation, or primary visual cortex. The presence of macular sparing is a key localizing sign, suggesting an infarct in the primary visual cortex located in the occipital lobe. The occipital lobe is primarily supplied by the posterior cerebral artery (PCA). Macular sparing occurs because the macular area of the visual cortex often has a dual blood supply from both the PCA and the middle cerebral artery (MCA). Therefore, a left PCA occlusion is the most likely cause.

Question 15

A 40-year-old office worker presents with numbness and tingling in his right hand that is worse at night. He describes the sensation in his thumb, index, and middle fingers. On examination, there is weakness of thumb abduction and opposition. Tapping over the volar aspect of his wrist elicits tingling in the fingers. Which of the following is the most likely site of nerve compression?

Which of the following is the most likely site of nerve compression?

  1. Cubital tunnel at the elbow
  2. Carpal tunnel at the wrist (correct answer)
  3. Axilla
  4. Cervical spine at C6-C7
Explanation: This patient's symptoms and signs are classic for carpal tunnel syndrome, which is caused by compression of the median nerve as it passes through the carpal tunnel at the wrist. The sensory distribution (first 3.5 digits) and motor weakness (thenar muscles) are specific to the median nerve. The positive Tinel sign (tapping on the nerve) further supports this diagnosis.

Question 16

A 70-year-old man with a history of poorly controlled hypertension presents with the abrupt onset of flailing, involuntary movements of his left arm and leg. The movements are high-amplitude and continuous. A non-contrast CT scan of the head is performed. A lesion in which of the following structures is most likely responsible for his symptoms?

A lesion in which of the following structures is most likely responsible for his symptoms?

  1. Left caudate nucleus
  2. Right subthalamic nucleus (correct answer)
  3. Left substantia nigra
  4. Right cerebellum
Explanation: The patient is exhibiting hemiballismus, a hyperkinetic movement disorder characterized by violent, flinging movements of the limbs on one side of the body. This condition is most commonly caused by a contralateral lesion in the subthalamic nucleus, which is part of the basal ganglia motor circuit. A small lacunar stroke is a common etiology.

Question 17

A 45-year-old man presents to the clinic with a 2-month history of progressive difficulty walking. Examination reveals weakness and spasticity in both lower extremities. He has a bilateral loss of pain and temperature sensation from the umbilicus downwards. However, his ability to sense vibration and joint position in his legs is completely preserved. What is the most likely site of the lesion?

What is the most likely site of the lesion?

  1. Anterior spinal cord (correct answer)
  2. Posterior columns of the spinal cord
  3. Bilateral parietal lobes
  4. Central cervical cord
Explanation: This clinical picture is characteristic of anterior cord syndrome. The lesion affects the anterior two-thirds of the spinal cord, damaging the corticospinal tracts (causing bilateral spastic weakness below the lesion) and the spinothalamic tracts (causing bilateral loss of pain and temperature). The dorsal columns, which transmit vibration and proprioception, are spared because they are located in the posterior cord and have a separate blood supply (posterior spinal arteries).

Question 18

A 22-year-old man is involved in a motor vehicle collision where he sustained a hyperextension injury to his neck. In the emergency department, he has marked weakness in both of his arms, with relative sparing of his legs. He also reports a loss of pain and temperature sensation in a 'cape-like' distribution across his shoulders and upper arms. Proprioception and vibration sense are intact. Which of the following is the most likely site of injury?

Which of the following is the most likely site of injury?

  1. Anterior horns of the lumbar cord
  2. Bilateral brachial plexus
  3. Central cervical spinal cord (correct answer)
  4. Medial lemniscus in the brainstem
Explanation: This patient's presentation is classic for central cord syndrome. This syndrome is often caused by a hyperextension injury, leading to damage to the central part of the cervical spinal cord. This affects the spinothalamic fibers crossing in the anterior commissure (causing the 'cape-like' sensory loss) and the medial aspects of the corticospinal tracts, which control the arms, leading to upper extremity weakness that is greater than lower extremity weakness.

Question 19

A 25-year-old man sustained a fracture of the midshaft of the humerus. After casting, he is unable to extend his wrist or fingers on the affected side. He also reports decreased sensation over the posterior forearm and the dorsal surface of the first three and a half digits. Which nerve is most likely injured?

Which nerve is most likely injured?

  1. Median nerve
  2. Ulnar nerve
  3. Radial nerve (correct answer)
  4. Musculocutaneous nerve
Explanation: The clinical presentation of 'wrist drop' (inability to extend the wrist and fingers) combined with sensory loss on the posterior forearm and dorsolateral hand is pathognomonic for a radial nerve injury. The radial nerve runs in the spiral groove of the humerus, making it particularly vulnerable to injury with midshaft humeral fractures.

Question 20

A 62-year-old man presents with difficulty using his left hand. Examination reveals atrophy of the hypothenar eminence and interosseous muscles. He is unable to adduct or abduct his fingers. When asked to make a fist, his 4th and 5th digits remain partially extended. There is sensory loss over the medial one and a half digits. Sensation over the medial forearm is intact. The lesion is most likely located at which of the following sites?

The lesion is most likely located at which of the following sites?

  1. Medial cord of the brachial plexus
  2. Lower trunk of the brachial plexus
  3. Ulnar nerve at the elbow (correct answer)
  4. Ulnar nerve at the wrist (Guyon's canal)
Explanation: This patient has a classic ulnar neuropathy, with weakness of intrinsic hand muscles (interossei, hypothenar) leading to a 'claw hand' deformity, and sensory loss in the ulnar distribution. The most common site of ulnar nerve compression is the cubital tunnel at the elbow. Sparing of sensation over the medial forearm (innervated by the medial antebrachial cutaneous nerve, which branches off the medial cord) helps to distinguish this from a more proximal brachial plexus lesion. A lesion at Guyon's canal would typically spare the ulnar-innervated muscles in the forearm.