Spinal Cord MCQs

Explanation: LP is performed below the termination of spinal cord, and the most preferred site is the disc between L3 and L4 vertebra. This space is safely located below conus medullaris and provides a roomy subarachnoid space containing only cauda equina nerve roots.

The patient's ataxia and swaying, which persist even when his eyes are open, suggest a problem with the cerebellum. The cerebellum is responsible for coordinating movement and maintaining balance. Damage to the cerebellum can result in unsteady and uncoordinated movements, leading to ataxia. The normal vibration sense on all four limbs indicates that the dorsal columns, which transmit sensory information such as vibration sense, are intact. The cerebral peduncles, posterior limb of the internal capsule, and ventral horns of the spinal cord are not directly involved in coordinating movement and balance, making them less likely to be the cause of the patient's symptoms. Reference : Textbook of Gray's Anatomy for students, 3rd Edition, Head and Neck, Page number - 841

After entering the spinal cord the first order neurons synapse (in the nucleus proprius), and the second order neurons decussate via the anterior white commissure. These second order neurons ascend synapsing in the VPL of the thalamus. Incoming first order neurons can ascend or descend via the Lissauer tract. Reference - Textbook of Gray's Anatomy for students, 3rd Edition, Back Page number - 901

The dorsal root of a spinal nerve contains afferent sensory nerve fibers and no efferent autonomic nerve fibers. The efferent autonomic nerve fibers, which originate in the lateral horn of the spinal nerve, travel out of the spinal cord through the ventral root of the spinal nerve. As the ventral and dorsal roots join to form the spinal nerve, the fibers from both roots intermingle, and the dorsal and ventral primary rami take a mix of fibers, including afferent sensory fibers from the dorsal root, and efferent motor fibers from the ventral root. Postganglionic sympathetic efferent fibers join each spinal nerve via a gray ramus communicans. So, all of the other nerves listed do contain efferent autonomic fibers. Reference : Textbook of Gray's Anatomy for students, 3rd Edition, Head and neck, Page number - 841

Lumbar puncture is performed below the level of L2 to avoid needle damage to the spinal cord, which may extend to level L2 vertebra. Reference: Textbook of Gray's Anatomy for students, 3rd Edition, Back, Page number - 104

In an adult, the spinal cord usually ends at the inferior border of L1 or the superior border of L2. Therefore, it is relatively safe to insert a needle above or below L4. At this level, the nerve roots are suspended in the CSF and can float away from the pressure of the needle, so these roots will not be damaged by the needle. How can you find the L4 level on a patient? If you find the tops of the 2 iliac crests and draw a line connecting them, that line should be going through the spinous processes of the L4 vertebra. Reference: Textbook of Gray's Anatomy for students, 3rd Edition, Back, Page number - 104

The previous question stated that a myelogram is a radiograph taken following injection of a radio-opaque dye into the subarachnoid space. So, it should make sense that the arachnoid must be ruptured for the dye to leak out following this procedure. Denticulate ligaments are specializations of the pia mater that form a longitudinal shelf separating the dorsal and ventral rootlets. They suspend the spinal cord in the subarachnoid space. These ligaments would not be disturbed during a myelogram. Periostium is a fibrous connective tissue that invests bones, and perineurium is a connective tissue covering that encloses a fasicle of peripheral nerve fibers. The pia mater is the innermost covering of the spinal cord. It closely follows the entire spinal cord and is not penetrated during a myelogram Reference: Textbook of Gray's Anatomy for students, 3rd Edition, Back, Page number - 103

This is straight from lab: To expose the spinal cord, it was necessary to remove the laminae, spinous processes, and ligamenta flavum. The supraspinous ligament and the interspinous ligament also needed to be removed. Reference: Textbook of Gray's Anatomy for students, 3rd Edition, Back, Page number - 104