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Chapter 8: Back

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A 16-year-old female is admitted to the emergency department with fever, neck stiffness, and a change in mental status. Her mother reports that she had complained of a headache and had become progressively tired and confused over the past 48 hours. Bacterial meningitis is suspected and a lumbar puncture is performed to assess cerebrospinal fluid. Which structure would not be pierced when performing this procedure?

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A. Arachnoid mater

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B. Dura mater

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C. Ligamentum flavum

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D. Pia mater

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E. All of the above would be pierced.

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Answer D. Cerebrospinal fluid is contained in the subarachnoid space. To reach this space, the needle would pass through (in order) ligamentum flavum, dura mater, and arachnoid mater. Pia mater intimately invests the surface of the spinal cord and would not be penetrated during a successful lumbar puncture.

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A 16-year-old female is admitted to the emergency department with fever, neck stiffness, and a change in mental status. Her mother reports that she had complained of a headache and had become progressively tired and confused over the past 48 hours. Bacterial meningitis is suspected and a lumbar puncture is performed to assess cerebrospinal fluid. Which is the palpable bony landmark may be used to identify a safe vertebral "level" to perform the lumbar puncture?

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A. Coccyx

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B. Rib 12

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C. Spinous process of L2

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D. Supracristal plane

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E. Transverse process of L4

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Answer D. To avoid spinal cord damage during a lumbar puncture, the needle should be introduced inferior to the medullary cone (conus medullaris). This cone most frequently lies at the L2 vertebral level and, thus, a needle introduced at the L3-L4 vertebral level is considered safe. A commonly accepted landmark for this level is the supracristal plane, a transverse plane connecting the superior-most aspect of the iliac crests.

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A 16-year-old female is admitted to the emergency department with fever, neck stiffness, and a change in mental status. Her mother reports that she had complained of a headache and had become progressively tired and confused over the past 48 hours. Bacterial meningitis is suspected and a lumbar puncture is performed to assess cerebrospinal fluid. Lumbar puncture is facilitated by the fact that the needle is inserted into the region of the vertebral canal occupied by the cauda equina. Which statement best describes the cauda equina?

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