Neurosciences Module
25 Month 2010
Dr. Aguilar
SPINAL CORD AND MENINGES
OUTLINE
A.
B.
C.
D.
E.
F.
G.
H.
External Anatomy
Spinal Nerves
White Matter
Gray Matter
Meninges
Blood Supply
Anatomical-Clinical Correlation
Spinal Cord Syndromes
I.
Sample Questions
A.
External Anatomy
Weight: 35g
Length: 45 cm (male), 43cm (female)
Vertebra: 70cm
Diameters (mm)
Cervical (c6)
Mid thoracic
Lumbar (l3)
Transverse
13-14
10
12


Sagittal
9
8
8.5
Spinal Cord
 Surrounded by a single layered dura mater,
arachnoid and pia mater
 Terminates in cone shaped structure called the
conus medullaris
 The filum terminale, a fibrous extension of the pia
mater extends to the posterior surface of the
coccyx to anchor the spinal cord
 Cord does not extend the entire length of the
vertebral column
Spinal Cord Segments and nerves

8 cervical (only 7 vertebrae)

12 thoracic

5 lumbar

5 sacral (fused)

1 coccygeal
31 Nerves total
Spinal Cord segments and vertebral body relationship
Cord Segment
V. Body
S. Process
C8
c6-c7
c6
T6
t4-t5
t3
L1
t11
t10
Sacral
t12-l1
t12-l1
Segment of the cord is not at the exact same level of bone
Cervical and Lumbar enlargement – due to nerve plexuses
Group 5
Cervical -> c4 to t1 segments – brachial plexus
Lumbar -> L1 to s3 segments – lumbar plexus
Conus medullaris

terminal termination of the spinal cord

s2-s4 cord segments

autonomic functions (urination)

vertebral body level
o 3rd fetal month – cord occupies entire canal
o birth – l3 vertebral body
o adult – l1-l2 vertebral body
Importance: in spinal tap/lumbar punctures you stick the needle in
the portion where you will not damage the cord (adults usually
below the L2, baby usually lower than L3 because if not you
puncture the spinal cord)
Cauda equina (horse’s tail)

lumbosacral nerve roots

distal to l2 vertebra (because conus medullaris ends at
L1-L2)
FIlum terminale

fibrous strand at the inferior end of conus medullaris

inserts at dorsum of coccyx

dural covering may be at the S2 level

continuation of conus medullaris

included in cauda equina

not even a nerve, no neurological function
B.
Spinal nerves
Structure

Ventral roots (motor)

Dorsal roots (sensory)

Spinal ganglion
Rons | Mikes | Chins | Sibs| Daves? | Carls | Ais| bex | Treex | Carols
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BATCH 2014  SPINAL CORD AND MENINGES
Fissures and sulci

Dorsal (posterior) medial septum

Ventral (anterior) median fissure

Dorsolateral sulcus
o Entry of dorsal root fibers

Ventrolateral sulcus
Spinal Nerves

Each connects to the spinal cord by 2 roots – dorsal
and ventral

The 2 roots join to form a spinal nerve prior to
exiting the vertebral column

Roots are short and horizontal in the cervical and
thoracic regions while they are

Each ramus is mixed

Joined to the base of the ventral rami of spinal
nerves in the thoracic region are the rami
communicates, these are sympathetic fibers

Dorsal rami supply the posterior body trunk
whereas the thicker ventral rami supplies the rest
of the body trunk and the limbs
C.
Lateral columns

lateral spinothalamic tract (pain and temperature)

anterior spinothalamic tract (light touch sensation)

corticospinal tract (motor)

2 lateral gray masses connected by the gray commisure

posterior projections are the posterior or dorsal horn

anterior projections are the anterior or ventral horn
D.
Gray Matter




Spinal cord white matter (funiculi)




Posterior funiculi (columns)

In the spinal cord, white matter is peripheral, gray
matter is central

White matter on each side of the cord is divided
into columns or funiculi
o Posterior, lateral and ventral divisions
o ascending or descending fibers

Fasciculus gracilis – medial leg area

fasciculus cuneatus – lateral

Myelinated nerve fibers

functions
1. vibratory sense
2. position sense
3. two point discrimination
4. touch
5. weight perception
Group 5
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


E.
Posterior dorsal horns contain interneurons
Anterior horn contain some interneuron as well as the
cell bodies of motor neurons
Lateral horns contain sympathetic motor neurons,
services visceral organs
 Axons exit via ventral root
 Afferent sensory fibers for the dorsal root (dorsal
ganglian – afferent)
 Ventral roots are efferent
 Dorsal and venral form the spinal ganglion
These cell bodies project their axons via the ventral
roots of the spinal cord to the skeletal muscle
The amount of ventral gray matter at a given level of the
spinal cord is proportional to the amount of skeletal
muscle innervated
Divided into 9 layers from dorsal going ventral (REXED’s
NUCLEI)
o Dorsal horn – substantia gelatinosa
o Clarke’s nucleus – Rexed nucie laminae #7
Where do you expect the ventral horns to be big?
o Lumbar and cervical
Spinal nerves divide into:

Ventral ramus

Dorsal ramus

Ramus communicans
Each root gives rise to rootlets
Roots are short in the horizontal portions of the cervical
and thoracic regions
Dorsal and ventral roots form fuse to form spinal nerves
Spinal Cord Meninges
Dura matter (hard mother)

white fibroelastic tissue

continuation of meningeal layer of cranial dura

ends at s2 level
Epidural Space

areolar tissue, fat + internal vertebral venous plexus
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BATCH 2014  SPINAL CORD AND MENINGES

negative pressure, epidural anesthesia
Subdural Space

only a potential space
Arachnoid mater

attached to dura

no true subdural space

arachnoid trabeculae

subarachnoid space contain CSF

lumbar cistern (l2-s2)

puncture to arachnoid causes CSF to rush out
Pia Mater

two layers
o intima pia
o epi-pial layer (covers blood vessels)

pial specializations:
o denticulate igaments (18-24 pairs)

achor to cord to the spinal canal

triangularly shapes
o linea splendens
o filum terminale
F.
Spinal cord blood supply
Vertebral arteries

anterior spinal artery – supplies anterior 2/3

posterior spinal artery – supplies posterior 1/3

two posterior arteries going dorsally

forms a single anterior spinal artery
G.
Anatomical-Clinical Correlation
Triad of symptoms in spinal cord disorders:

sensory level - the hallmark of a spinal cord lesion

distal, symmetric spastic weakness

bowel and bladder problems

corticospinal tract – leg area is more lateral

sphenothalamic tract – same as corticospinal

dorsal columns – opposite, limbs are more lateral
Sensory levels

shoulders

lateral arm and deltoid

inner and outer aspects
of the forearms

thumbs and little fingers

level of nipple

xiphoid

umbilicus

groin

front of both thighs

knee

medial and lateral aspect
of both calves

little toes
c4
c5
c6 & t1
c6 and c8
t4
t6
t10
l1
l2
l3
l4 and l5
s1
Radicular Artery

From segmental vessels originating from the aorta

Coming from aorta towards down to thoracic

Vulnerable “watershed” areas of the spinal cord:
t1-t3 and l1 cord segments

Artery of Adamkiewics:
o Artery of the lumbar enlargement
o Anterior spinal artery for 50% of cord
(lower 2/3)
o L1-l2 root (t7-l3)
o Left side in 2/3 of cases
o Ligation in surgery leads to paralysis
Venous drainage

3 anterior and 3 posterior spinal sinuses/veins

internal vertebral plexus (epidural)
o Batson’s plexus

Valveless – can go retrograde to brain

pathway for metastatic spread (prostatic
CA)
Group 5
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BATCH 2014  SPINAL CORD AND MENINGES

H.
Spinal cord Syndromes
Complete cord transaction

complete loss of neural function below level of
lesion

spinal shock 1-6 wks mean 3wks

spastic paralysis with hyperreflexia
Anterior spinal artery syndrome

bilateral motor and sensory loss below level of
lesion

posterior column function preserved

anterior 2/3 is damaged
Brown-sequard (hemisection) syndrome

one side of cord affected

loss of motor function and position sense on
ipsilateral side of lesion and pain and temperature
sense contralateral to the lesion
Central cord syndrome

central portion of cord affected

parts of 3 main tracts affected

upper limbs more affected than lower limbs
Dorsal column syndrome

uncommon

tabes dorsalis (neurosyphillis)

position and vibratory sense lost below lesion

motor and sensory function preserved
Conus medullaris syndrome

S2-s4

Pain is rare

Bilateral and symmetric sensory loss

Symmetric motor loss

Early autonomic symptoms

Tumor inside the spinal cord
Addressed by cutting the filum terminale and not the
spinal cord
1.
Which part of the spinal cord mainly controls urination and
defecation?
a. Cauda equine
b. Conus medullaris
c. Filum terminale
d. Fasciculus gracilis
2.
Which of the following is not a function of the posterior
funiculus?
a. Two-point discrimination
b. Weight perception
c. Pain
d. Position sense
3.
Dura mater ends at what vertebral body level?
a. S1
b. S2
c. S3
d. S4
4.
The groin area is supplied by what nerve?
a. T10
b. L1
c. L2
d. L3
5.
Which of the following is not part of Cauda Equina
syndrome?
a. Rare pain
b. Inulateral sensory loss
c. Asymmetric motor loss
d. Late autonomic symptoms
Answers: B, C, B, B, A
Cauda equina syndrome

Problem is nerve roots

Prominent pain

Unilateral asymmetric sensory loss

Asymmetric motor loss

Late autonomic symptoms

Tumor outside the spinal cord
Tethered Cord Syndrome

Spinal cord remains tethered to the coccyx

Normally, cord should be higher

Filum terminale is thickened and pulls the spinal
cord down

If ignored, child may have problems with the spinal
cord and present with motor sensory problems
Group 5
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