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023 - 023 - Fracture of the dens of the axis with posterior dislocation may crush the spinal cord at the level of the __________ first cervical vertebra with terminal paralysis of respiratory musculature.

024 - The cruciform ligament is the principal structure preventing subluxation at the atlantoaxial joint because the articular surfaces between the axis and __________ atlas are nearly horizontal and there is no intervertebral disk.

025 - Herniation usually occurs in the fourth or fifth intevertebral disks because of the pronounced lumbar curvature and the considerable body mass __________ superior to this region.

026 - The anterior and posterior longitudinal ligaments reinforce the underlying annulus fibrosus but do not meet __________ posterolaterally, resulting in a weak area predisposed to herniation.

027 - Lumbar puncture and intrathecal anesthesia should be introduced below the third lumbar vertebra as the spinal cord usually __________ terminates between the first and second lumbar vertebrae.

028 - Posterolateral disk prolapse impinges upon the spinal nerve of the next lower vertebral level, causing symptoms associated with the __________ dermatomic and myotomal distribuations of that nerve.

029 -
Hernia involvement, signs, and reflex test:
Hernia Involvement Signs Reflex Test
C3-C4 __________ C4 (Phrenic, C3-C5) Weak diaphragmatic Respiration  
C4-C5 C5 (Suprascapular, C4-C6) __________ Weak arm abduction  
C5-C6 C6 (Musculocutaneous, C5-C6) Weak forearm flexion __________ Biceps
__________ C6-C7 C7 (Radial, C6-C8) Weak forearm extension Triceps
C7-C8 __________ C8 ( Ulnar, C7-T1) Weak thumb adduction  
L1-L2 L2 (Genitofemoral, L1-L2) __________ Weak hip flexion Cremaster
L2-L3 __________ L3 (Obturator, L2-L4) Weak knee extension  
L3-L4 L4 (Femoral, L1-L4) Weak leg extension __________ Knee jerk
__________ L4-L5 L5 (Fibular, L4-S1) Weak dorsiflexion  
L5-S1 S1 (Tibial, L5-S2) __________ Weak plantar flexion Ankle jerk
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