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Group A
5%
251/4813
Group B
2%
75/4813
Group C
14%
656/4813
Group D
74%
3555/4813
Group E
224/4813
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Group D correctly matches the nerve roots with the correct vertebral neuroforamen. Understanding the nerve root anatomy in relation to the anatomic structures of the vertebral motion segment is critical when evaluating patients with cervical and lumbar radiculopathy. One important concept to understand is that in the cervical spine the nerve roots exit above the corresponding pedicle. Therefore, the C7 nerve root exits above the C7 pedicle. This is different than in the lumbar spine where the nerve roots exit below the corresponding pedicle. Therefore, the L3 nerve root travels below the L3 pedicle. The difference can be explained by an extra nerve root (C8) in the cervical spine that does not have a corresponding pedicle (there is no C8 vertebral body). Therefore, C8 exits below the pedicle of C7. T1 is the first nerve root to exit below the corresponding pedicle (T1 travels below the T1 pedicle). Devlin et al. discussed methods to monitor nerve root function during surgery. They report electromyograpy can be classified into two categories based on method of elicitation — mechanical and electrical. Mechanically elicited electromyography (EMG), also called spontaneous or free-running EMG, may be useful during the dynamic phases of surgery (eg, implant placement, nerve root manipulation). Electrically elicited EMG, also called stimulus-evoked EMG or triggered EMG, may be useful during static phases of surgery (eg, testing pedicle screws after placement). Together, these electromyographic techniques encourage early detection of excessive nerve root traction, mechanical injury, or cortical breach. Illustration A shows a labeled version of Figure A. Illustration B illustrates the difference between the horizontal nature of the cervical nerve roots and the vertical nature of the lumbar nerve roots. The horizontal nature in the cervical spine explains why both a central and foraminal disc herniation affect the same nerve root. Additionally, because the spinal cord ends at L2, large central herniations can cause upper motor symptoms in the cervical spine, but similar large central discs can cause cauda equina syndrome below L2. Illustration V is a video showing how to read an MRI of the cervical spine and identify foraminal stenosis. Incorrect Answers: Group A,B,C and E: These groups have a least one nerve root which is incorrectly placed in the neuroforamen.
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