Neuroanatomy USMLE Step 1 Practice Question
A 56-year-old woman is brought to the emergency department after a motor vehicle collision. She reports immediate onset of complete paralysis of both legs and loss of all sensation below the umbilicus. On examination, she has flaccid paralysis of the lower extremities with absent patellar and Achilles reflexes bilaterally. Rectal examination reveals absent anal sphincter tone and sensation. MRI of the spine shows complete transection of the spinal cord at the T10 level with surrounding edema. Which of the following anatomical structures is primarily responsible for the immediate loss of voluntary motor control in her lower extremities?
Answer choices
- ADorsal columns carrying proprioceptive and vibration sense from lower extremities
- BCorticospinal tracts carrying descending motor commands to lower spinal cord segmentsCorrect answer
- CSpinothalamic tracts carrying pain and temperature sensation from below the lesion
- DVentral horn motor neurons whose axons form the lower extremity peripheral nerves
- ESpinocerebellar tracts mediating coordination and balance reflexes
- FRubrospinal and vestibulospinal tracts controlling antigravity muscles
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