Deck · USMLE Step 1
Nervous System & Special Senses
Neuroanatomy, neurophysiology, neuropathology, peripheral nerve and NMJ disorders, and the eye and ear — including stroke syndromes, neurodegeneration, and neuropharmacology.
110 cards · audited · SM-2 spaced repetition
Included with the full USMLE Step 1 program — 14 decks, 1,546 cards.
Sample cards
Which ascending tract carries fine touch, vibration, and proprioception, and where does it decussate?
The dorsal column–medial lemniscus pathway. First-order neurons ascend ipsilaterally in the dorsal columns and synapse in the nucleus gracilis/cuneatus of the caudal medulla; second-order fibers decussate there as the internal arcuate fibers and ascend as the medial lemniscus.
Where does the spinothalamic tract decussate, and what does it carry?
It carries pain and temperature (and crude touch). Second-order neurons decussate within 1–2 levels of entry at the anterior white commissure of the spinal cord, then ascend contralaterally.
Where does the lateral corticospinal tract decussate, and what is the consequence for lesion localization?
~90% of fibers decussate at the pyramidal decussation in the caudal medulla. Lesions above the decussation cause contralateral weakness; lesions below (in the cord) cause ipsilateral weakness.
What is the classic presentation of Brown-Séquard syndrome (spinal cord hemisection)?
Below the lesion: ipsilateral loss of motor (corticospinal) and dorsal column (touch/vibration/proprioception), with contralateral loss of pain/temperature (spinothalamic, beginning 1–2 levels below). At the level: ipsilateral LMN signs and a band of ipsilateral sensory loss.
Distinguish upper motor neuron (UMN) from lower motor neuron (LMN) lesion signs.
UMN: spasticity, hyperreflexia, increased tone, positive Babinski, minimal atrophy, no fasciculations. LMN: flaccid paralysis, hyporeflexia, decreased tone, atrophy, fasciculations, no Babinski.
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