Spinal Cord and Meninges
Objectives:
1. Describe the segmental nature and external structure of the
spinal cord.
2. 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?)
3. Describe the blood supply and venous drainage of the spinal
cord.
4. Describe the structure of the meninges and the associated
spaces.
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
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
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:
Dermatomes, Myotomes and Sclerotomes
C5
C6
C7
Teres Minor
Supraspinatus
Rhomboids
Infraspinatus
Deltoid
Teres Major
Biceps
Brachialis
Serratus Anterior
Subscapularis
Pectoralis Major
Pectoralis Minor
Coracobrachialis
Latissimus Dorsi
Anconeus
Triceps
C8
T1
“The Heavenly Seven”
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.
Nerve Roots
Nerve Roots
Cauda equina:
Nerve Roots and IV Discs
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)
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
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
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
Blood Supply to the Spinal Cord
Venous Drainage of the Spinal Cord
Spinal Veins:
Internal Venous Plexus:
Intervertebral veins:
Venous Drainage of the Spinal Cord
External Spinal Venous Plexus:
Basivertebral Veins:
Venous Drainage of the
Spinal Cord
BATSON’S PLEXUS
*Know 2 facts…see notes below
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:
1. Dura mater
2.Arachnoid mater
3.Pia mater
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
Spinal Meninges
Epidural 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
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
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.
Lumbar Cistern
Lumbar Puncture
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.
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
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)
Spinal Meninges
Spinal block:
Epidural block:
Spinal Meninges