ANATOMY

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