Gross Anatomy:

Spinal Cord and Meninges

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 of termination is slightly more superior in flexion

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

Coracobrachialis

Latissimus Dorsi

Anconeus

Triceps

Serratus Anterior

Subscapularis

Pectoralis Major

Pectoralis Minor

Biceps

Brachialis

T1

Teres Minor

Supraspinatus

Rhomboids

Infraspinatus

Deltoid

C5 C6 C7 C8

Teres Major

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.

“The Heavenly Seven”

Nerve Roots

Nerve Roots and IV Discs

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

Muscle Stretch 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

Note the position of SPINAL CORD SEGMENTS relative to VERTEBRAL BODIES!

Student Dr. Spencer?A compression fracture of the L2

vertebral body would most directly affect what level of the SPINAL CORD?

A. T12B. L1C. L2D. L4E. Cx1

Blood Supply to the Spinal Cord• Branches from the Vertebral Artery - Anterior and Posterior

Spinal Arteries • Segmental Spinal Arteries

– anterior radicular– posterior radicular – variable segmental medullary arteries

Blood Supply to the Spinal Cord

Venous Drainage of the Spinal Cord

Intervertebral veins: follow arteries and nerves. They are draining spinal veins

Spinal Veins:Internal Venous Plexus: communicates

with the external spinal venous plexus

Venous Drainage of the Vertebral Column

External Spinal Venous Plexus:Basivertebral Veins: they drain the

vertebral bodies

A 66-year-old male presents with the chief complaint of increased urinary frequency, back pain, lower limb weakness and numbness of two weeks duration. A digital rectal exam suggests prostate cancer. A gadolinium-enhanced MRI of the spine reveals:

Think/Pair/Share

A 12-year-old male presents with the chief complaint of fever, headaches, nuchal rigidity, nausea and lethargy of two days duration. History and physical exam leads to the suspicion of meningitis.

You need to sample cerebrospinal fluid. Where is it?

What layers do you need to go through to sample CSF?

Where should you stick your needle?

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 mater2. Arachnoid mater3. Pia mater

Spinal Meninges

The dura mater:• is the outermost covering of the

spinal cord

• is a thick and dense inelastic membrane

• is attached around the foramen magnum and 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

The epidural space: • is between the dura and the

periostium of the vertebrae

• extends to the skull - fluids put into the sacral hiatus can spread to the base of the skull

The subdural space:• is a potential space between

dura and the arachnoid that contains only a serous fluid

• ends at the level of S2

Potential spaces can become REAL spaces when they fill with blood, air, etc.

Spinal Meninges

The arachnoid is a delicate membrane, that is separated from the dura by a potential subdural space. The arachnoid is not attached to the dura, but held to it by the normal pressure of CSF

The subarachnoid space:• is 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:

Sampling CSF:Lumbar puncture and intracranial pressure:- What about a newborn?

Lumbar Cistern

Lumbar Puncture

Spinal Meninges

The pia mater:

• faithfully invests the spinal cord and brain

• is a vascular membrane (holds all the vessels like posterior and anterior spinal artery)

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 MeningesSpinal block: Epidural block: injecting anesthesia outside the dura