SDL 7 - SPINAL CORD & SPINAL NERVES

Question 1

What is the functional difference between the dorsal and ventral nerve roots?

Answer 1

dorsal root:

• has a dorsal root ganglion containing the cell bodies of sensory neurones

ventral root:

• consists of axons from the lower motor neurones in the ventral horn of the spinal cord

Question 2

Where do the dorsal and ventral roots unite to form the spinal nerves?

Answer 2

the dorsal and ventral roots unite together within the intervertebral foramen to form the spinal nerve

the nerve emerges through the intervertebral foramen and gives off recurrent meningeal branches

it then divides immediately into a dorsal​ and a ventral ramus

Question 3

What are the dorsal and ventral rami of spinal nerves?

What does each supply?

Answer 3

dorsal ramus:

• posterior division of a spinal nerve
• carries information that supplies muscles and sensation to the human back

ventral ramus:

• anterior division of a spinal nerve
• supply the antero-lateral parts of the trunk and the limbs

Question 4

Where is the epidural space found?

Answer 4

between the dura mater and the bone of the vertebral canal

Question 5

What happens at the end of the spinal cord?

Answer 5

the end of the spinal cord is tapered and a thin pial thread continues downwards to attach to the coccyx

Question 6

What is the composition of the cauda equina like?

How does it descend?

Answer 6

it is made up of lower lumbar, sacral and coccygeal nerve roots

these descend through the lumbar cistern

this is the region of subarachnoid space between the level of termination of the cord and the level at which the “tubes” of dura and arachnoid terminate (about S2)

Question 7

Complete the table

Answer 7

Question 8

What spinal level is the cauda equina level?

Answer 8

L3 - L5

Question 9

What is contained within the subarachnoid space?

Answer 9

cerebrospinal fluid (CSF)

the composition of CSF is altered in certain clinical conditions, so sometimes it is useful to obtain samples of the fluid for diagnostic purposes

Question 10

In which 3 conditions may the composition of CSF be altered?

Answer 10

• meningitis
• encephalitis
• tuberculosis

Question 11

What is the most common site to obtain CSF?

How is this procedure carried out?

Answer 11

the lumbar cistern is the most common site from which CSF is sampled, using a lumbar puncture

the patient is positioned on one side, perpendicular to the bed and curled up as much as possible

a needle is inserted in the midline between the L3 and L4 vertebrae

Question 12

What surface landmarks would you use to determine the point at which to insert the lumbar puncture needle?

Answer 12

The L3/L4 interspinal space is a few mm above the spinous process of L4

this is done by palpating the iliac crests

Question 13

Starting with the skin, which layers are pierced by the lumbar puncture needle?

Answer 13

• skin
• subcutaneous layer
• back muscles
• supraspinous ligament
• interspinous ligament
• ligamentum flavum

Question 14

What is meant by a “pop” or a “give” when the lumbar cistern is reached?

Answer 14

this occurs when the lumbar puncture needle is moved through the ligamentum flavum and enters the lumbar cistern

Question 15

label the diagram showing the relationships between the vertebral bodies, intervertebral discs, intervertebral foramina and nerve roots

Answer 15

Question 16

In what way is bladder function affected by compression of the cauda equina?

Answer 16

the nerves of the cauda equina provide motor and sensory function to the legs and the bladder

bladder and bowel dysfunction can occur

there may be permanent paralysis in the muscles of one or both of the legs

Question 17

What causes cauda equina syndrome?

Answer 17

symptoms that result from damage to the nerves of the cauda equina

this may be caused by disc herniation and compression by tumours