Spinal cord- gross anatomy,

internal features, blood supply

Dr.G.Arthi

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NERVOUS SYSTEM

• Neurons

• Neuroglial cells

• Meninges

• Neurons+neuroglial cells

– Inside cns=grey mater/nuclei

– Outside cns=ganglia

• Nerve fibers

– Inside cns – tracts/

– Outside cns - nerves

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INTRODUCTION

NERVOUS SYSTEM

CENTRAL

BRAIN SPINAL CORD

PERIPHERAL

CRANIAL-12

SPINAL-31 AUTONOMIC

SYMPATHETIC PARASYMPATHETIC

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GROSS FEATURES

• Elongated cylindrical portion of

CNS

– Outside the cranium

– Inside the vertebral column

• In fetus occupies whole Vertebral

column till 3rd month IUL

• Adult upper 2/3 of vertebral

column

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SPINAL CORD

• Spinal cord is the lower elongated part of the CNS

• Lies extra cranially and inside vertebral canal

• Occupies upper two third of vertebral canal

• Cylindrical in shape flattened anteroposteriorly

• Ends in conus medularis and filum terminale

• Functions:

a. Execution of simple reflexus

b. Transmission of impulses to and from brain

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SPINAL CORD

• EXTERNAL FEATURES

• BLOOD SUPPLY

• APPLIED ASPECTS

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• Measurements:

• Length: Adult male: 45cms

Adult female:42cms

• Average diameter: 1.25 cm

• Weight: 30gms

• Extension:

Downward continuation of the medulla oblongata.

• Upper end: First cervical vertebra{C1 }

• Lower end: Conus medularis { L1}

• Conamedularis continues as filum terminale

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FACTORS PROTECTING THE

CORD:

• Bony cage of vertebral canal

• Spinal meninges

• Hydrostatic cushion of CSF

FACTORS KEEPING THE CORD

IN POSITION:

• Rostral continuity with

medulla oblongata

• Caudal fixation with filum

terminale and cauda equina

• Laterl suspension with

ligamentum denticulatum

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ENLARGEMENTS

• ENLARGEMENTS contains more motor neurons to supply the limbs

• Cervical:

Extends from C5 to T1 segments to form brachial plexus

widest circumferance-38mm

at C6

• Lumbosacral:

Extends from L2toS3 to form lumbosacral plexus.

Widest circumferance -35mm at S1

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FILUM TERMINALE

• At L1 Lower end of spinal cord

ie Conamedularis continues as

filum terminale

• length: 20 cm

• Filum terminale interna: 15cm

in length, lies within dural sac

• Filum terminale externa:

5cm in length, lies outside

dural sac below the level of S2

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CAUDA EQUINA

• The nerve roots of 5

lumbar, 5 sacral and 1

coccygeal nerves take a

vertical course to form

a bunch of nerve fibres

around the filum

terminale.

• Resemblance :

cauda - tail

equina - horse

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EXTERNAL FEATURES OF SPINAL CORD

• Fissures and sulci

• Attachment of spinal

nerves

• Enlargements

• Corda equina

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Fissures and sulci

Anterior aspect:

Anteromedian fissure:3mm width. It is deep and extends the entire length of the cord with:

• Anterior spinal artery in it

• Two anterolateral sulci on either side

• Linea splendens

Posterior aspect:

Posteromedian sulcus: 1.5-2.5mm. Its a faint longitudinal groove with 2 posterolateral and two posterointermediate sulci.

The posteromedian sulcus contains a septum of neuroglial tissue

( posterior median septum).

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• Each half of the cord is further sudivided into posterior , lateral and anterior region by anterolateral and posterolateral sulci

• Ventral root spinal fibres emerge from Anterolateral sulcus

• Through posterolateral sulcus enter dorsal root spinal fibres

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ATTACHMENT OF SPINAL NERVES

• Emerges 31 pairs of spinal nerves from the side.

• Cervical -8, thoracic-12,lumbar-5,sacral-5,coccygeal-1.

Spinal nerve attachments

anterior posterior motor sensory

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MENINGES OF SPINAL CORD

• Pachymeninges – DURA

• Lepto meninges – Arachnoid + Pia mater

• Dura

– Meningeal dura of cranium continues

– Foramen magnum to S2

– Continues as dura of filum up to Coccyx

– Epidural space between bone and dura

– Subdural space between dura and arachnoid

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MENINGES

• Arachnoid mater

– Thin and transparent

– Subdural space separates

from dura

– Subarachnoid space from pia

– Extends up to S2

• Pia mater

– Extends along filum

terminale

– Vessels lie along this layer

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MENINGES

• Modifications of pia mater

– Linea splendens

– Ligamentum denticulatum

• Filum terminale

– Internum 15 cm

– Externum 5 cm

• Lumbar cistern

– L1-S2

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SPINAL SEGMENTS

• Part of the spinal cord were pair of spinal nerves– { right and left } attached.

• The spinal segments corresponds to the vertebral level in thoracic, lumbar and sacral regions but not in cervical region.

• The spinal segments has a rule lie above the numerically corresponding vertebral spines

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SPINAL SEGMENT

• Segment of cord with a

pair of spinal nerves

• 31 segments

• Cervical 8

• Thoracic 12

• Lumbar 5

• Sacral 5

• Coccygeal 1

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LOCALIZATION OF SPINAL SEGMENTS

• Localization of spinal segment is important to locate cord lesion or the site of surgical approach

Region Spine Cord segment

Cervical C6 +1 C7

Upper thoracic T3 +2 T5

Lower thoracic T7 +3 T10

Sacral T12-L1 S1-S5

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REGIONS

SPINAL

SEGMENTS

VERTEBRAL

LEVEL

GENERAL

RULE

Upper

cervical

C2 C2

Same level

Lower

cervical

C6 C5 One

vertebra

above

Upper

thoracic

T5 T3 Two above

Lower

thoracic

T10 T7 Three above

lumbar L1 TO L5 T10 TO T11 Three to five

above

Sacral and

coccygeal

S1 TO S5

C X 1

T12 TO L1 Six to ten

above 22

SPINAL CORD

EXTERNAL AND INTERNAL FEATURES

• White mater

• Anterior, lateral and

posterior funiculus

• Grey mater

• Anterior, posterior and

lateral horns

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MACROSCOPIC APPEARANCE

cervical

Thoracic

Lumbar sacral

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CHARACTERSTIC FEATURES OF SPINAL SEGMENTS AT

VARIOUS T.S LEVELS

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CHARACTERSTIC FEATURES OF SPINAL SEGMENTS AT

VARIOUS T.S LEVELS

Features

Levels

Cervical Thoracic Lumbar Sacral

Outline of section Oval Oval to circular Nearly circular Circular to

quadrilateral

Gray matter

•Posterior horn

•Lateral horn

•Anterior horn

Large

Slender, extends

far posteriorly

Massive

Absent

Small

Slender

Slender

Present

Large

Bulbous

Bulbous

Present only in

L1,L2

Relatively large

Massive

Massive

Present only in

S2,3,4

Reticular formation W ell developed Poorly

developed

Absent Absent

Amount of white

matter

Massive ++++ Large+++ Less+++ Very less+

Postero intermediate

sulcus

Present through

out

Present in

upper 7 T seg

Absent Absent

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BLOOD SUPPLY

ARTERIAL SUPPLY

1. Anterior spinal artery:

ORIGIN: Branches of right and left vertebral arteries in the upper cervical canal.

COURSE: runs caudally in the anterior median fissure. Joins with the fellow of the opposite side to form anterior arterial trunk.

TERMINATION: filum terminale

SUPPLIES: Anterior two third of the cord

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BLOOD SUPPLY Contd

2. Two posterior spinal arteries:

ORIGIN : Branched from either

1. Vertebral

2.Posterior inferior cerebellar arteries. COURSE: Runs down in the posterolateral sulcus divides into two collateral arteries medial and lateral along the posterior nerve roots.

Thus there are 5 longitudinal arteries around the spinal cord.

These arteries reinforced by the segmental arteries to form 5 longitudinal arterial trunks

These communicate around the cord forming pial plexus{ arterial vaso corona/arteriae coronae.

SUPPLIES :Posterior one third of the cord

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BLOOD SUPPLY Contd

3. Segmental arteries:

Branches of

Deep cervical,

Ascending cervical,

Intercostal and

Lumbar

Segmental arterial feeders reach the cord as anterior and posterior radicular arteries.{8 to 12}

ANTERIOR RADICULAR ARTERIES: Larger and less in number.

T1 and T11 are very large – Arteria radicularis magna

{Artery of adamkiewicz}

POSTERIOR RADICULAR ARTERIES: Smaller and more in number.

FEEDER ARTERIES: Great anterior medullary artery of

Adamkiewicz-arises from aorta at T12 or L1 vertebral level unilateral left side

Importance: major source of blood to the lower 2/3 of the spinal cord

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BLOOD SUPPLY Contd

• Anterior arterial trunk-

formed by union of two

anterior spinal arteries

arising from vertebral

arteries and a branch of

Arteria magna

• Posterior spinal trunk-

formed by two posterior

spinal arteries and posterior

radicular arteries

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Area of supply:

• Anterior trunk supplies : ventral two third of cross

section of spinal cord– anterior gray columns, bases

of posterior gray column and adjoining portions of

white mater.

• Pair of posterior arterial trunks and vasa corona

supply-- Rest of the cord They are end arteries.

• Spinal branches of vertebral arteries supply: Upper

cervical cord segments

• Radicular branches of ascending cervical and deep

cervical supply: C7 to T2 spinal segments.

• Radicular branches of aortic intercostal and lumbar

arteries supply: spinal segments below T2.

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BLOOD SUPPLY Contd

CLINICAL CORELATION:

• Anterior spinal artery syndrome:

• The artery of T11 spinal segment (arteria radicularis magna)

is remarkably large. A fracture of vertebra involving this

artery leeds to softening of several segments of the cord

• The artery of T1 spinal segment anastamoses with other

arteries in a valvular fashion so that its supply is directed

only downwards. Therefore C8 segment is most affected.

• T1,T4 and L1 segments -- the meeting places of different

major arteries are vulnerable to ischemic necrosis.

• Anterior medullary syndrome.

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VENUS DRAINAGE

• Two median longitudinal- one in

the anterior median fissure

another in posteromedian sulcus

• Two anterolaterlal – one on either

side posterior to the anterior nerve

roots

• Two posterolateral-one on either

side posterior posterior nerve roots

• Drain below through internal

vertebral venous plexus into the

vertebral posterior intercostal,

lumbar, and lateral sacral veins.

And drain above into the basilar

venous plexus.

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APPLIED AND CLINICAL ANATOMY

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SPINAL CORD- LESIONS

• Trauma

• Infection

• Vascular

• Tumors/Neoplasm-

*Extradural Osteosarcoma

Chondroma

*Intradural Meningioma

Neurofibroma

*Intramedullary Glioma

SPINAL CORD LESIONS contd

• Compression of nerve roots

* Radicular pain

* Paresthesia

* Localised muscular atrophy

* paralysis due to ventral root

Compression of cord

* anterior horn cells defect

* sensory loss

* corticospinal defect

* bladder and bowl sphincter disturbances

Surgical procedure

* Laminectomy

SPINAL CORD

TRAUMATIC INJURY-contd

• Hemisection: Brown –Sequard syndrome

• Lateral hemisection: due to trauma or compression of extramedullary tumors.

On the side of the lesion:

1. loss of position and vibratory sense, disturbances of stereognosis and tactile discrimination below the level of lesion – damage of posterior funiculus

2. Spastic paralysis, exaggerated tendon reflexes, positive Babi ski’s sig - involvement of pyramidal tract

Conralateral side:

loss of pain and temp- damage of lateral spinothalamic tract

at the site of lesion:

Irritation of dorsal root produces radicular pain ,parasthesia

Irritation of ventral root produces flacid paralysis of muscles

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SPINAL CORD

SUDDEN VASCULAR LESIONS

Thrombosis in Anterior spinal artery

Spinal segment C8 is vulnerable

Involvement of anterior horn cells-flaccid type of palsy

Lateral corticospinal tract-spastic type

Loss of pain and temperature- lateral spinothalamic tract

Ischemia of arteria radicularis magna

Cauda equina paraplegia

SPINAL CORD

CLINICAL ANATOMY

• Lumbar Puncture L3-L4 L4-L5

• Collection of CSF 1 drop/sec

• Injection of radio opaque dye Lipiodal

• Spinal block (anesthesia) – 2% Procaine

• Measurement of intracranial pressure

• Injection of drugs

REFERENCES

• Gray’s a ato y-39th edition

• Clinical neuroanatomy – 2nd edition by VisramSing

• Clinical neuroanatomy – 3nd edition by A.K.Dutta

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