Spinal cord injury

Spinal cord injury leads to either temporary or permanent dysfunction. Dysfunction of spinal cord occurs because of:

1. Direct injury due to bullet firing or accidents (on road, in working place, during communal violence,

etc.)

2. Compression by bone fragments, hematoma or disk material

3. Ischemia due to rupture of spinal arteries.

During mechanical injury, spinal cord may be cut into two or one lateral half of the spinal cord may be

damaged or diffused crushing of several segments of spinal cord may also occur. Accordingly, dysfunction of spinal cord is classified into four types:

A. Complete transection

B. Incomplete transection

C. Hemisection

D. Diseases of spinal cord.

COMPLETE TRANSECTION OF SPINAL CORD

Complete transection of spinal cord occurs due to:

1. Bullet injury, which causes dislocation of spinal cord

2. Accidents, which cause dislocation of spinal cord or occlusion of blood vessels.

Complete transection causes immediate loss of sensation and voluntary movement below the level of

lesion. In quick transection of spinal cord, the patient feels himself cut into two. For a while, his mind remains clear but he feels as if his lower part of the body below the injury does not exist. It is because his higher centers remain unaffected but the spinal centers below the level of injury loose the function.

Then the effects (symptoms) of complete transection of spinal cord start appearing. Effects occur in three stages:

1. Stage of spinal shock

2. Stage of reflex activity

3. Stage of reflex failure.

Stage of Spinal Shock

Stage of spinal shock is the first stage of effects that occurs immediately after injury. It is also called stage

of flaccidity. Following are the signs and symptoms that develop during this stage:

i. Paralysis of limbs

Paralysis occurs in two limbs or in all four limbs. Paralysis of limbs depends upon the level of Injury:

a. Injury at the cervical region of the spinal cord leads to the paralysis of all the four limbs. Paralysis

of all the four limbs is called quadriplegia or tetraplegia

b. Injury at the thoracic, lumbar or sacral segments including cauda equina and conus medullaris

causes paralysis of lower limbs. Paralysis of lower limbs is called paraplegia.

ii. Flaccid paralysis

Paralyzed muscles become flaccid, i.e. loose stiffness because of loss of tone. This type of paralysis is called flaccid paralysis.

iii. Loss of reflexes

All the reflexes are lost because of the injury to anterior and posterior nerve roots.

iv. Loss of sensations

All the sensations are lost because of the injury to posterior nerve roots and sensory neurons in the

posterior gray horn.

v. Effect on visceral organs

Some of the visceral organs are also affected; especially, urinary bladder and rectum are paralyzed.

vi. Heart rate

Heart rate is decreased and pulse becomes weak and thready.

vii. Venous return

Venous return is very much decreased. Venous return depends upon the muscle tone during resting

condition. During activity it depends upon contraction of skeletal muscle.

But, in complete transection of spinal cord, muscle tone is lost and flaccid paralysis occurs. This leads to

decrease in venous return. In addition, the limbs are immobile and smooth muscles of blood vessels loose the tone. So, the blood gets accumulated in blood vessels of limbs, particularly in lower limbs. And, the lower limbs become cold and blue.

viii. Effect on blood pressure

Effect on blood pressure depends upon the level of injury:

a. Lesion anywhere below L2 segment

Blood pressure is not affected much because the sympathetic vasoconstrictor fibers leave

the spinal cord between T1 and L2 segments.

b. Lesion at or above T1 segment

All the sympathetic vasoconstrictor fibers leaving the spinal cord from T1 and L2

segments are transected and are completely cut off from higher medullary cardiovascular

centers, which regulate the blood pressure. So the blood pressure falls drastically. Mean

arterial pressure falls below 40 mm Hg. Severity of complete transection depends upon

the level of lesion. Complete transection at the level of cervical region can be very fatal. Because, the

diaphragm and other respiratory muscles are cut off from respiratory centers. It causes paralysis of respiratory muscles leading to sudden arrest of breathing.

The crushing injury at sacral segments of spinal cord results in atonic bladder and loss of micturition

Reflex.

Stage of Reflex Activity

Stage of reflex activity is also called stage of recovery. After 3 weeks period, depending largely upon the

general health of the patient, the reflex activity begins to return to the isolated segments of spinal cord below the level of lesion.

Stage of Reflex Failure

Though the reflex movements return, muscles below the level of injury have less power and less resistance. Usually, general condition of the patient starts deteriorating. General infection or toxemia becomes common. Due to this, the failure of reflex function develops. The reflexes become more difficult to elicit. The threshold for stimulus increases. Mass reflex is abolished and the muscles become extremely flaccid and undergo wasting.