Spinal Cord

Spinal cord

The caudal elongated part of the CNS. Medulla oblongata continues as spinal cord from foramen magnum to the L1 –L2 junction.

Almost every skeletal muscle in the body below the head is under the spinal cord control. Most of the cutaneous sensation below the neck is carried by spinal cord.

In addition, the sympathetic and lower part of parasympathetic systems(non vagal) is carried by the spinal cord. •Sympathetic system is also called •‘thoracolumbar out flow’ •Parasympathetic system is called •‘cranio sacral out flow’

structure Centrally has grey matter. Peripherally has white matter. Gray matter has ventral and dorsal horns White matter is composed fibers only

mainly of nerve

the center of the cord is traversed by a central canal connecting with the ventricles of the brain and contains cerebrospinal fluid.

enlargements

cervical enlargement A swelling in the spinal cord in the region of C3-4 - T1-2 supplies the upper limb muscles.

lumbar enlargement A Swelling in the spinal cord in the region of T10-12 - L1-2 supplies the lower limb muscles.

Conus medullaris  The

tapering lower end of spinal cord.  Filum terminale begins here.

Filum terminale ?

A slender thread like prolongation of pia mater Starting from conus medullaris extends up to the back of coccyx.

Stabilizes the spinal cord within the vertebral canal.

cauda equina The spinal nerve roots in the the lower part of the vertebral canal in the region of the lower lumbar vertebrae, sacrum and coccyx; Somewhat resemble a "horse's tail."

The spinal cord terminates at L1/2 in adults and at L3 in infants.

The line joining the iliac crests is at L3/4 and is called Tuffier’s line. The subarachnoid space ends at S2 in adults and lies lower in children.

SPINAL MENINGES

Spaces around the cord

The epidural space exits as a potential space, between the dura and the ligamenta flava. Used for anesthesia.

•Membrane around the spinal cord (1) •Epidural space(2). In Blue the veins of this space •Ligamentum flavum(3) •Interspinous ligament(4) •supraspinous ligament(5)

Lumbar puncture

Horns and funiculi (Gray)

(white)

Lateral horn?

External features(topography)

Anterior median fissure The groove along the anterior midline of the spinal cord that incompletely divides it into symmetrical halves.

Posterior median septum

Lies in a groove along the posterior midline of the spinal cord that incompletely divides it.

Spinal segment  The

part of the spinal cord that gives rise to a pair of spinal nerves is called a “spinal segment”  There are 31spinal segments.

Levels(regions) of the spinal cord and  differences Note the gray and white matters(ratio wise)

The spinal cord is suspended in the dural sac by pairs of tooth-like ligaments made up of pia mater. “Denticulate ligaments”

Ligamentum denticulatum There are 21 pairs of these ligaments, each arising from the side of the spinal cord midway between the dorsal and ventral nerve roots.

Ligamentum denticulatum The highest projection is at the level of foramen magnum and the lowest - at T12-L1 junction. These ligaments are surgeon’s guides to the spinal nerves

Blood supply of the spinal cord 3 longitudinal vessels; 1 anterior spinal artery and 2 posterior spinal arteries

Anterior Spinal Artery runs down the entire length of the spinal cord in the anterior median fissure and supplies the anterior 2/3of the spinal cord. It is smallest in the area of T4 to T8.

Posterior Spinal Artery

arises from either the vertebral arteries or the posterior inferior cerebellar arteries(PICA) and passes down the posterior aspect of the spinal cord.

These arteries have extensive anastomoses between themselves and the anterior spinal artery. In general, the posterior spinal arteries supply posterior 1/3of the cord.

The central branches that enter the spinal medulla are end arteries. This pattern of surface anastomoses and perforating end arteries is seen throughout the CNS.

The anterior and posterior arteries alone can only supply the upper cervical segments of the spinal cord.

Radicular arteries(feeder arteries) feed the “spinal arteries”

Feeder arteries enter through the intervertebral foramina and pass along the ventral and dorsal roots of the spinal nerves to reach the cord.

Anterior radicular arteries supply the anterior spinal artery.

Posterior radicular arteries supply the posterior spinal arteries.

The Great Radicular Artery (“artery of Adamkiewicz”)  usually

one of the anterior radiculars

•also known as the arteria radicularis magna. •It is important because it is the major blood supply to the inferior 2/3 of the spinal cord

Artery of Adamkiewicz

1/3

2/3

Clinical relevance Damage to the radicular arteries may seriously affect the functions of spinal cord and cause muscular weakness and paralysis The areas that are most vulnerable to ischaemia are T1–3,T5 and L1.

Blockage of a posterior spinal artery may have little effect because of the extensive anastomoses!

but occlusion of an anterior spinal artery often produces ischaemia of the anterior central part of the cord causing flaccid paralysis and loss of pain and temperature sensation.

**Thrombosis of the great radicular artery(of Adamkiewicz) may produce a paraplegia because it makes a major contribution to the blood supply of the lower two-thirds of the spinal cord.

Spinal cord injury(SCI)

SCI at cervical levels usually causes a loss of independent breathing and loss of function to the arms and legs, thereby resulting in quadriplegia. Thoracic level injuries usually affect the chest and the legs and result in paraplegia. Lumbar level injury typically results in loss of control of the legs, bladder, bowel and sexual functions. Sacral level injuries generally cause lower motor neuron flaccid paralysis type lesions involving some loss of function in the legs and difficulty with bowel, bladder and sexual control.

Venous drainage The veins of the spinal cord are distributed similar to the arteries. There are usually 3 anterior veins and 3 posterior veins.

These veins communicate extensively with each other and are drained via radicular veins, then into intervertebral veins then to vertebral veins, ascending lumbar veins, and to the azygos system.

Summary

The position of the spinal cord varies with the movements of the vertebral column, its lower extremity being drawn slightly upward when the column is flexed.

It also varies at different periods of life; up to the third month of fetal life it is as long as the vertebral canal, but from this stage onward the vertebral column elongates more rapidly than the spinal cord.

by the end of the fifth month the cord ends at the base of the sacrum and at birth ends at the level of third lumbar vertebra.

The adult spinal cord is(45cm) considerably shorter than its vertebral column so the spinal segments and the vertebral levels do not correspond.

Important levels Spinal segment

vertebral level(spines)

Cervical 1-8

foramen magnum to C6 (add 1 to the spine)

Thoracic 1-6

C6 –T4(add 2 to the spine)

Thoracic 7 –12

T4-T9(add 3 to the spine)

Lumbar and sacral

T10-L1

Syringomyelia (dilatation of central canal) •Usually beginning in the cervical region. •There will be bilateral loss of pain and temperature in the affected region. •Touch and proprioception are not affected. •Thus the patient has dissociation of sensory loss.

myelogram  X-ray

of spinal cord  Taken by injecting contrast medium into the subarachnoid space by lumbar puncture.  The technique is called “myelography”

HEMISECTION OF THE SPINAL CORD (BROWN-SEQUARD SYNDROME) Pure hemisection of the cord rarely occurs but it is among the best cases for illustrating the features of spinal cord injury.

symptoms include: spastic paralysis, loss of position sense, discriminative touch and vibratory sense on the side of the lesion - this represents involvement of the lateral corticospinal tract and the posterior white column on the side of the lesion.

On the side opposite the lesion there is a loss of pain and temperature due to involvement of the lateral spinothalamic tract.