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Homunculus

Topic updated on 06/14/17 12:44pm

Overview
 

 
Snapshot
  • A 67-year-old man is brought to the emergency department due to dysarthria and right-sided facial and arm weakness. These symptoms occured approximately two hours ago. Pertinent past medical history includes hypertension, diabetes, and migraine headaches. Head CT is negative for bleeding. Appropriate medication is initiated.
Introduction
  • Primary sensory and motor cortices
    • the primary sensory cortex receives sensory information from the opposite side of the body
      • this cortex is in the post-central gyrus
    • the primary motor cortex controls movement of the opposite side of the body
      • this cortex is in the pre-central gyrus
  • Typically the sensory and motor circuit is somatotopically organized 
    • for example, a region involved in the sensory and motor function of the hand is
      • next to the region involved in the sensory and motor function of the arm
    • the somatotopic cortical maps can be referred to as a homunculus ("little man")
  • Clinical correlate
    • lesions affecting certain areas of the primary motor and somatosensory cortex → contralateral spastic paresis and hemihypesthesia, respectively
      • e.g., stroke involving the anterior cerebral artery will lead to
        • contralateral muscle weakness and sensory loss of the lower limb

 



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