Spinal Cord Anatomy

Question 1

Thoracic vertebrae parts

Answer 1

-Body- held together by ligaments
-Spinous process- prominent in T1,T2 which makes it easier to count
-transverse process (lateral sides)

Question 2

Intervertebral disk

Answer 2

-acts as a cushion
-gel like substance which comes out when you herniate a disc, which applies pressure to spinal cord

Question 3

Vertebral column

Answer 3

-spinal cord runs through the vertebral column and nerves exit at intervertebral foramen
-vertebrae transition directions at T11 (anticlinal vertebra- all spinous process point cranial after this point)

Question 4

Special vertebrae

Answer 4

-C1 (atlas)- has very wide transverse processes and is generally wider/flatter, prominent spinal process not present
-C2 (axis)- dens extends cranially; prominent spinal process not present

Question 5

CNS vasculature

Answer 5

-the spinal cord supplied by segmental vessels (Aorta) and the vertebral arteries (vertebral, costocervical, intercostal, lumbar)
-dorsal: dorsal spinal arteries (paired)
-ventral: ventral spinal
artery (single;midline)- most of blood supply from ventral side
-the blood supply from the brain comes from the ventral aspect (basilary artery and internal carotid)

Question 6

Greatest blood supplier

Answer 6

-ventral spinal artery supplied most of the spinal cord (~2/3rds)

Question 7

Segments of spinal cord

Answer 7

-cervical
-thoracic
-lumbar
-sacral

Question 8

Where do spinal nerves exit?

Answer 8

-exit vertebral canal via intervertebral foramen

Question 9

Cervical and lumbosacral enlargements

Answer 9

-important for the limbs, more neurons present, especially for the dexterity required

Question 10

Peripheral nerves

Answer 10

-mixed nerves (dorsal sensory root and ventral motor root)
-these mixed nerves will then give rise to a dorsal and ventral branch (“rami”) to innervate targets

Question 11

Conus medularis

Answer 11

-end of spinal cord
-segments are compressed as you move caudally and multiple segments fit within a single vertebrae
-the spinal cord (dura mater) ends, but these nerves will extend out and come out further down=cauda equina

Question 12

Cauda Equina

Answer 12

-the lumbosacral junction marks the end of the spinal cord but the cauda equina continues as spinal nerves that move caudally to exit at their corresponding vertebral segment (spinal nerves are outside of the CNS because outside the dura mater)
considered a group of nerves

Question 13

Nerves of cauda equina

Answer 13

-nerves will contributes to innervation of the pelvis and perineum
-S1-S3 form the pudendal nerve, which is a convenient location for local anesthesia
**a distal lumbar or sacral fracture will damage all of these nerves together (L7-Ca5) and result in cauda equina syndrome= damage to PNS, so no CNS signs

Question 14

Meninges in spinal cord

Answer 14

-the dura mater is not fused to periosteum in vertebral column (whereas it is in the brain)

Question 15

Epidural space

Answer 15

-the space between the dura and vertebral body
-space contains fat, blood vessels, and spinal nerves

Question 16

Anesthesia in epidural space

Answer 16

-anesthetic solution will diffuse locally cranial/caudal through the epidural space to bather the spinal nerves and provide the nerve block
-most local anesthetics agents work by inhibiting sodium channels, therefore action potentials (nerve conduction) is stopped
**typically done caudally to anesthetize structures of the cauda equina (perineum) without causing motor deficits to pelvic limbs

Question 17

Subdural space

Answer 17

-this is the potential space between the arachnoid and the dura
-can be a site of hemorrhage and subsequent CNS compression

Question 18

Subarachnoid space

Answer 18

-space created by the arachnoid trabeculae
-filled with CSF (collection sites for CSF)

Question 19

Locations of spinal taps

Answer 19

1.cisternal tap (cerebellomedullary cistern, atlanto-occipital site)- used when brain lesion
2. lumbar tap (caudal lumbar site)- used when spinal cord lesion
Tap where fluid would drain from the injury

Question 20

How much CSF to collect?

Answer 20

-collect 2 tubes (1ml/5kg)
-used for cytology or protein analysis

Question 21

Spinal cord injuries

Answer 21

-soft tissue trauma (IVDD)
-vascular injury
-fracture
-disease (demyelination, cell death, electrolyte imbalance)
-toxin/infection
-neoplasia

Question 22

Difficulties of treating spinal cord injuries

Answer 22

-CNS tissues are very delicate and damaged more easily
-neural tissue has limited regenerative capacity
-many drugs used to treat other soft tissue injuries are ineffective in the CNS due to the protective BBB and B-CSF barriers

Question 23

Spinal cord compression

Answer 23

-compression of spinal cord or peripheral nerves will cause neurological deficits and/or pain
-from herniation of disc

Question 24

IVDD (intervertebral disc disease)

Answer 24

-common in small breed dogs, middle-aged to geriatric
-Breeds: daschunds, bulldogs, boston terriers, beagles, shih tzu, corgis

Question 25

Wobbler’s syndrome

Answer 25

-cervical spondylomyelopathy
-unknown cause, but may be due to growth discrepancy between spinal cord and vertebral column resulting in a narrowed spinal canal and/or compression of the cervical cord OR from bony changes to the vertebral column that cause compression
-Breeds: Dobermans, great danes, weimaraners, other giant breeds