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.
0 Comments