1. Spinal Cord and Meninges

2. Objectives:
Describe the segmental nature and external structure of the spinal cord.
Indicate the relationship of spinal roots/nerves to intervertebral discs (what cord levels will be affected with a disc protrusion in cervical or lower lumbar levels?)
Describe the blood supply and venous drainage of the spinal cord.
Describe the structure of the meninges and the associated spaces.

3. What is the most likely etiology for these findings?
A 18-year-old female presents with pain in her neck and in her right arm. Physical exam reveals pain along the lateral arm, involving the thumb. Grip strength is normal. Her upper limb reflexes on the right side are:
biceps = 1/4
brachioradialis = 0/4
triceps = 2/4
What is the most likely etiology for these findings?
CLINICAL CONCEPT
Muscle Strength is measured on a scale of 0 to 5.
> Normal strength is 5/5
> Paralysis is 0/5
Reflexes are measure on a scale of 0 to 4.
> Normal is 2/4
> PNS lesions are 0 or 1/4
> CNS lesions are 3 or 4/4

4. Spinal Cord The spinal cord: occupies the vertebral canal
in infants the spinal cord extends into the sacrum
in the adult the cord extends from the cranial border of the atlas to L2
level is slightly higher when the column is flexed

5. Spinal Cord The spinal cord is: part of the central nervous system.
segmental in nature
What is a spinal cord segment?
How many segments are there?
Note the relationship of the “nerves” to the spinal cord:

6. Dermatomes, Myotomes and Sclerotomes

7. “The Heavenly Seven”

8. Spinal Cord Enlargements
Cervical Enlargement
the larger and more pronounced of the enlargements
extends from about C3 to T2
Lumbar Enlargement
extends from L1 to S3
Below the lumbar enlargement, the cord tapers to the conus medullaris.
Why does the spinal cord have enlarged areas? B/C btwn. C5-C8 and L3-S2 you have a need for more neurons in order to innervate the appendages….the upper limbs and the lower limbs.

9. Nerve Roots

10. Nerve Roots
Cauda equina:

11. Nerve Roots and IV Discs

12. Position of spinal segments relative to vertebra
Cervical – tip of the spine corresponds to the succeeding segment (C6 spine = C5 cord level)
Upper Thoracic – tip of the spine corresponds to 2 segments lower in number (T4 spine = T6 segment)
Lower Thoracic – 3 segments difference (T10 spine = L1 segment)

13. A 43-year-old female presents with abdominal pain of gradual onset
A 43-year-old female presents with abdominal pain of gradual onset. Physical exam reveals a non-tender, pulsating mass on the left side of the abdomen.
An MRI and angiography reveals an aortic aneurysm. She elects for surgical repair.
Physical exam following the surgery reveals on the left: a hypoactive patellar reflex [1/4] and weakness in the quadriceps [3/5].
What happened? artery of Adamkiewicz is blocked

14. Blood Supply to the Spinal Cord
Branches from the Vertebral Artery – 1 Anterior and 2 Posterior Spinal Arteries
Feeder Vessels – highly variable; artery of Adamkiewicz (lumbar)
Radicular arteries – supply the roots
There are 2 Posterior spinal arteries and ONE anterior spinal artery. If artery of Adamkiewicz is blocked, the spinal cord dies.

15. Blood Supply to the Spinal Cord
Spinal arteries
Postcentral
Radicular arteries = supply the dorsal and ventral roots, some branches (feeder vessels) join the anterior and posterior spinal arteries
Prelaminar

16. Blood Supply to the Spinal Cord

17. Venous Drainage of the Spinal Cord
Spinal Veins:
Internal Venous Plexus:
Intervertebral veins:

18. Venous Drainage of the Spinal Cord
External Spinal Venous Plexus:
Basivertebral Veins:

19. Venous Drainage of the Spinal Cord
BATSON’S PLEXUS
*Know 2 facts…see notes below
BATSON’S PLEXUS 1- connected to veins in abdomen, pelvis, head and neck 2-this plexus of veins has no valves, so there can be backflow (blood can go in both directions)…cancer can get all over body if it reaches the Batson’s Plexus

20. Spinal Meninges
The spinal cord (in fact the entire CNS) is enclosed in three layers of tissue, the meninges.
The meninges are from external to internal:
Dura mater
Arachnoid mater
Pia mater

21. Spinal Meninges The dura mater:
is the outermost covering of the spinal cord.
is a thick and dense inelastic membrane
forms a loose sheath around the cord
attaches around the foramen magnum and to the bodies of the 2nd and 3rd cervical vertebrae
has tubular extensions for the roots of the spinal nerve as they pass thorough the IV foramen
Blue= dural sac. Dura follows the outer cover of the nerves, the epineurium. The subdural sac ends at S2. Subdural is a potential space inside the dura, normally NOT filled with anything….is located btwn. The dura and the arachnoid.

22. Spinal Meninges Epidural space: Subdural space:
between the dura and the periostium of the vertebrae
fluids put into the sacral hiatus can spread to the base of the skull
Subdural space:
potential space between dura and the arachnoid that contains only a serous fluid
the arachnoid is not attached to the dura, but held to it by the normal pressure of CSF
ends at the level of S2

23. Spinal Meninges
The arachnoid is a delicate membrane, that is separated from the dura by a potential subdural space.
Subarachnoid space: A REAL SPACE, NOT A POTENTIAL SPACE!
between the arachnoid and the pia
contains cerebrospinal fluid (CSF), blood vessels and connective tissue
surrounds the cord and spinal nerves, ends at the level of S2

24. Spinal Meninges
The arachnoid is only loosely related to the underlying pia mater.
the spinal cord ends at L2
the dural sac and arachnoid end at S2
As a result there is a large space between the arachnoid and pia in the lumbar region:
Lumbar Cistern:
Go below L3 w/needle, which will push nerve roots out of the way and will penetrate the subarachnoid space to get a CSF sample.
Sampling CSF:
Lumbar puncture and intracranial pressure:-
What about a newborn? Extends into sacrum in newborn.

25. Lumbar Cistern

26. Lumbar Puncture

27. Spinal Meninges The pia mater:
faithfully invests the spinal cord and brain
is a vascular membrane
Contains denticulate ligaments, delicate little transparent-like tissue that look like teeth coming off. ..see next slide.

28. Spinal Meninges Denticulate ligaments:
continuous with the pia on the cord, between the dorsal and ventral roots
tooth-like process, 21 in number, stops at the T12 level
serves to stabilize the cord within the dura
White sheath of tissue is the denticulate ligament, which acts as a tether to keep the spinal cord from swaying side to side in the vertebral column.

29. Spinal Meninges The filum terminale:
is a fine filament of pia and connective tissue that descends from the conus medullaris
descends to the level of S2 where it is joined by dura (filum terminale internum)
descends to coccygeal levels and anchors the spinal cord in the dura sac (filum terminale externum)

30. Spinal Meninges
Spinal block:
Epidural block:

31. Spinal Meninges