Spinal cord lesion

1. SPINAL CORD
LESION
By Shama Praveen
Physiology department

2. This Photo by Unknown Author is licensed under CC BY-SA-NC

3. Spinal cord
■ Extends from medulla oblongata in the brainstem to the lumbar region of
vertebral column after that it becomes caudal equina.
■ Afferent fibers enter spinal cord through dorsal root.
■ Efferent fibers leave spinal cord through ventral root.
■ Ventral root afferents are usually small unmyelinated nociceptors arising from
visceral structures.
■ Spinal connections
■ Afferent fibers after entering spinal cord may have following destinations:
■ Dorsal column to second order of neuron in medulla.
■ Dorsal column to second neuron in same segment and same side of spinal cord.
■ Directly or indirectly contact the corresponding motor neuronsin anterior horn
cells.

4. Spinal cord laminae
■ Laminae I to VI : Sensory laminae. They accommodate afferent fibers.
■ Lamina IX : Motor lamina
■ Laminae VII to VIII : contain motor neurons as well as interneurons.
■ Lamina X : Intercommissural lamina.
■ Lamina I : Receives small nociceptive Aδ and C fiber inputs. They send axons
to lateral cervical nucleus, dorsal column nuclei, thalamus etc.
■ Lamina II : Known as substantia gelatinous. It receives primarily C fiber inputs.
Mostly they respond to nociceptive or strong mechanical stimuli.
■ Lamina III- VI : Receives myelinated A fiber inputs. These neurons respond to
fine touch, vibration and proprioception.

6. ■ Sensory functions : Conveys fine touch, tactile localization and
discrimination, pressure, proprioception and kinesthetic sensation and
vibration sense in the dorsal column of the same side.
■ In the spinothalamic tracts of the opposite side: Anterior tract conveys gross
touch and tactile localization whereas lateral tract conveys pain and
temperature sensations.
■ Motor functions: Tone and power of the muscles, movements of
muscle and joints, deep reflexes, superficial reflexes
■ Autonomic functions: Body temperature, visceral functions.
Functions of spinal cord

7. Spinal cord lesion
■ Complete transection of the spinal cord.
■ Incomplete transection of the spinal cord.
■ Hemisection of the spinal cord: Brown Sequard syndrome.
Sensory disturbances
• Syringomyelia
• Tales dorsalis
• Deafferentation: Section of dorsal nerve root
• Disseminated (multiple) sclerosis

8. Complete transection of the spinal
cord
■ It is seen in 2 stages: Stage of spinal shock or stage of flaccidity and stage of reflex activity.
■ Stage of spinal shock or stage of flaccidity
• Lost power of mediating reflex functions. Therefore, muscles are completely
paralyzed.
• If the transection occurs in the cervical cord, the patient becomes
quadriplegic. If the site of lesion is between C1 and C4, it is called high
quadriplegia and causes respiratory paralysis due to the involvement of the
phrenic nerve. These patients require respiratory support. If the site of lesion
is between C5 and C8, it is called low quadriplegia.
• Paraplegia: Lower limb paralysis
• Quadriplegia: All 4 limbs paralyzed.
• Paralysis of muscles decreases venous return producing cold and blue extremities,
skin becomes dry and scaly and bed sores develop.
• Muscle tone, all reflexes, all sensations are lost.
• The penis is flaccid and erection is impossible.

9. Causes of spinal shock
■ It may be due to stoppage of tonic bombardment of spinal motor neurons by excitatory
impulses in the desending Pathways.
■ Stages of reflex activity
■ Immediate Grey column of spinal cord are rich in NE and 5HT, Therefore after a week of
cord transection, when the autonomic reflexes are hyperactive, NE and 5HT content of cord
below transection are markedly reduced.
■ After a week, spinal sympathetic cell bodies appear to recover some tonic discharge.
■ Tone in the skeletal muscle returns slowly after 2 or 3weeksthis returning tone is reflex in
character and is produced by impulses entering the spinal cord.
■ Limbs adopts a position of slight flexionand paraplegia is therefore known as paraplegia in
flexion.
■ Reflex movements: Recovery of reflex excitability is due to the development of denervation
hypersensitivity to the mediators released by the remaining spinal excitability endings

10. ■ Flexor reflex: Reflex movement return first are the flexor reflex or withdrawal
reflex.
■ Mass reflex: Seen several months after original lesion due to irradiation of
afferent stimuli from one reflex centre to another.
 Flexor spasm of both lower extremities and contraction of anterior abdominal
wall.
 Evacuation of urinary bladder and rectum.
 Profuse sweating below the level of lesion : Causes sweating of whole body
when mass reflex is obtained.
 Deep reflex: The knee jerk or ankle jerk returns about 1 to 5weeks later than
flexor response.
 Stages of failure of reflex activity
 Malnutrition, infection or toxemia causes failure
 Disappear reflexes

11. Incomplete transaction of spinal cord
■ Lesion of spinal cord although the cord is severely injured but few tracts
escape injury and are not cut.
■ Stage of spinal shock same as complete transection.
■ Stage of reflex activity: Extensor thrust reflex, crossed extensor reflex and
Phillipson’s reflex.

12. Hemisection of the spinal cord:
Brown Sequard syndrome
■ Changes below the level of the hemisection on same side
 Sensory changes
 Fine touch, tactile localization and tactile discrimination, vibration sense and
kinesthetic senseslost
 Pain, temperature and crude touchremain unaffected
 Motor changes
 Extensive motor loss

13. ■ Opposite side
 Extensive sensory loss but little motor loss
• Changes at the level of hemisection
 Complete anesthesia occurs due to damage to the posterior nerve root,
posterior horn cells and spinothalamic fibers on the same side
 Damage anterior horn cells: Complete lower motor neuron type paralysis on
the same side
 Loss of pain sensation on the opposite side.
 Very slightly due to damage of some pyramidal tracts.

14. ■ Syringomyelia: Involving Grey matter round the central canal of spinal cord in
which excessive growth of neuroglial tissue occurs with cavity formation.
■ Tabes dorsalis: Degeneration of dorsal nerve roots occur. Caused by syphilis.
■ Deafferentation: Section of dorsal nerve root: Effect of injury to
afferent nerves.
■ Disseminated sclerosis: Disseminated means widespread throughout an
organ; sclerosis means increase of connective tissue in the nervous system.
■ Subacute combined degeneration of the spinal cord: Associated
with demyelinated of white fibers of the spinal cord affecting the dorsal column
and later lateral columns.

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