1. Spinal Cord Injuries

2. Objectives Review anatomy of the spinal cord
Review the physiology of the spinal cord
Cross and uncrossed tracts
Spinal cord injury
Etiology
Signs and symptoms
Classification

3. Readings Lundy-Ekman, Chapter 12 Saladin and Fredericks, Chapter 17
Also chapters on motor and sensory systems
Saladin and Fredericks, Chapter 17

4. Spinal Cord
How far down does the spinal cord travel down the vertebral column?
What about the nerve roots below this level?

5. Gross spinal cord anatomy
Outer layer
matter
Inner core

6. White Matter Arranged in columns Dorsal funiculus Lateral funiculus
Ventral funiculus

7. Fasciculi (tracts)
Fiber bundles that have same course and same terminations
Location of tracts in funiculi
Descending tracts:
Ascending tracts:

8. Organization of tracts
Longer tracts
Shorter tracts
Propriospinal tract (connect spinal levels)

9. Descending Spinal Tracts
From cerebral cortex
Corticospinal (pyramidal) tracts
Medial and lateral
From midbrain
Tectospinal
Rubrospinal
Interstitiospinal

10. From pons and medulla Medial and lateral vestibulospinal tracts
Pontine reticulospinal tract
Medullary reticulospinal tract
Both reticulospinal pathways has direct inputs from the cerebral cortex

12. Corticospinal tracts What regions of cortex? Fiber bundle in forebrain
Primary motor cortex
Supplementary motor cortex
Premotor cortex
Primary somatosensory cortex
Fiber bundle in forebrain
Posterior limb of internal capsule

13. Some fibers cross in caudal medulla
Base of brainstem
Pyramids in medulla
Some fibers cross in caudal medulla
Crossed: 85% - lateral corticospinal tract
Whole spinal cord – intermediate gray matter
Uncrossed: 15% - ventral corticospinal tract
Mostly cervical and thoracic
Anterior horn and intermediate gray matter

14. Descending axons terminate on:
Somatotopy
Fibers to legs lateral to fibers to arms
Descending axons terminate on:
Alpha and gamma motor neurons
Spinal interneurons

15. Rubrospinal tract Origin:
Receives input from cerebral cortex and cerebellum
Fibers cross and descend into spinal cord
Travel near lateral corticospinal tract
Function: control of muscle tone, particularly in contralateral upper extremity
May serve some function after injury to LatCS

17. Tectospinal Tract Origin: superior colliculus
Crosses and descend into spinal cord
Only to cervical regions of the cord
Function
Control of head, shoulder and upper trunk movements
Orientation movements of the head and neck to visual and possibly auditory input

19. Lateral vestibulospinal tract
Origin: lateral vestibular nucleus
Fibers: ipsilateral in anterior funiculus
Function:
Excites extensors motor neurons
Inhibits flexor motor neurons
Acts at many levels

20. Medial vestibulospinal tract
Origin: Medial vestibular nucleus
Fibers: only descend to cervical region
Function:
Influences neck and upper back muscles
Controls head position

21. Pontine (medial) reticulospinal tract
Origin: reticular formation in pons
Fibers: uncrossed in anterior funiculus
Function
Enhances postural and extensor muscle tone

22. Medullary (lateral) reticulospinal tract
Origin: reticular formation in medulla
Fibers: bilaterally in lateral funiculus
Function
In general, facilitates flexors and inhibits extensors, though the actions may be reversed under some conditions
Regulates voluntary movements, reflex activities, and muscle tone

23. ASCENDING SPINAL TRACTS
Transmit sensory information to:
Cerebellum
Thalamus
To Cerebral cortex
Tracts that carry information to thalamus
Dorsal columns-medial lemniscus pathway
Anterolateral (spinothalamic) pathway

24. Why do we care about sensation in a motor control class?
Needed for smooth, coordinated and movements
Protection from injury
Understanding our environment (perception)

25. Dorsal Columns – medial lemniscus pathway
Fibers
Large myelinated
Information
From mechanoreceptors
What modalities?
Proprioception
Touch
vibration

26. Fibers in DC-ML
Ascend in ipsilateral dorsal columns (funiculi) to caudal medulla
Cross in caudal medulla  thalamus  cerebral cortex
More distal regions on the body are more medial in the DC

27. DC fig

28. Lesions of DC Impair tactile and kinesthetic sense
Do not see abolition of sensation since the information also reaches the cortex by other routes

29. Spinothalamic tracts AKA: anterolateral system Modalities Pain
Temperature (hot and cold)
Crude touch
light touch, tickle, itch, pressure sensations from bladder and bowel, sexual sensations

30. Fibers Primary fibers synapse in dorsal horn
Second order neurons have axons which cross the midline
Fibers ascend in anterolateral white matter
Lateral fibers are for more caudal parts of body though the somatotopy is not as precise as for the DC

31. Function of spinothalamic tract
Primary pathway for pain and temperature sensation
Effects of injury
Most information ascends bilaterally (except for itch) so unilateral damage usually causes little impairment

32. Spinocerebellar pathways
Sensory information transmitted to cerebellum
Travels bilateral in spinal cord
Unconscious sensory information
Muscle, joint and cutaneous proprioceptors
Position of body in space
Relative position of body segments

33. Injury to spinocerebellar pathways
Clinically detectable deficits due to injury are rare
Other areas of cord are usually affected
No conscious sensation
Damage to tracts should result in ataxia

34. Gray matter in the spinal cord
What is in gray matter?
Cell bodies
Dendrites
Myelinated and unmyelinated axons
Glial cells

35. Regions of the gray matter
Dorsal horn
Ventral horn
Intermediate zone
Intermediate horn
Thoracic and upper lumbar levels

36. Rexed’s Laminae
The cells in the gray matter are organized in groups by histology
Similar neurons have a similar function
Dorsal horn: Laminae I – VI
Intermediate zone: Lamina VII
Ventral horn: Laminae VII – IX
Area surrounding central canal: Lamina X

37. Organization of motor neurons in the ventral horn
Motor neurons for proximal muscles
Motor neurons for flexor muscles

39. Lesions of the Spinal Cord General Principles
If we know what regions of the spinal cord are injured, we have a basis for understanding the functional deficits in the patient
Motor vs. sensory
Anatomic level of the lesion
Somatotopy of the involved tracts
Whether the tracts are crossed or uncrossed

40. Anatomic Level of the Lesion
Lesions of the spinal cord often give rise to motor and sensory deficits that are specifically related to the involvement of particular spinal segments
C.M. Fredericks

41. Damage to white matter
What structures in the spinal cord are lesioned?
Signs and symptoms will be seen in what parts of the body?

42. Damage to gray matter What structures in the spinal cord are lesioned?
Signs and symptoms will be seen in what parts of the body?

43. When both gray and white matter are injured, there is a mixture of deficits
Muscle weakness, atrophy, and abnormal DTR may provide a good indicator of the level of spinal cord injury
Particularly true for extremities
Lesion level may not be as clear on the trunk
The pattern of sensory losses may provide an even better indicator of spinal level

44. Tract Somatotopy Most caudal level on body: DC: Spinothalamic tract
Lateral corticospinal tract

45. Crossed or Uncrossed Tracts
Where do they cross?
Spinothalamic fibers
DC tract
Lateral corticospinal tract

46. So, can we reliably predict deficits?No
Anatomic variation among individuals
Collateral connections between tracts
Similar information can travel in different tracts
Overlap of somatotopic areas
Redundant innervation
Some information is carried bilaterally

47. Signs and Symptoms Caused by Spinal Cord Lesions
Pain
Paresthesias and numbness
Muscle weakness
Abnormal somatic reflexes and muscle tone
Autonomic dysfunctions

48. 3 types of Pain Local Pain
From damage to bony and ligamentous structures surrounding the cord
Can develop rapidly (trauma, infarction, herniation) or slowly (tumor, transverse myelitis, syringomyelia)
More severe over vertebral column at level of lesion but may spread to more distal areas

49. Radicular pain Damage to sensory nerve roots Pain may be excrutiating
May be associated with local pain
Dermatomal pattern

50. Diffuse Aching or Burning Pain
Occasionally seen
Due to dysfunction in spinal cord pain pathways
Usually in patients with traumatic SCI
Can develop late (months after injury)
Not localized to level of lesion
Can be well below level of lesion

51. Sensory abnormalities
Paresthesias
Abnormal activity in dorsal roots and DC pathways
Loss of sensation
All modalities or just some
DC – numbness or deadness
ALS - analgesia

52. Muscle Weakness Present in most disorders of the spinal cord
UMN weakness
Injury to:
Characteristics: hyperreflexia, spasticity, abnormal reflex responses
LMN weakness
Characteristics: atrophy, hypotonia, hyporeflexia or areflexia, fasciculations

53. Abnormal Reflexes and Muscle Tone
Spinal shock
Extensive spinal cord lesions
Trauma, infarction, hemorrhage, transverse myelitis
Transient state of markedly depressed spinal cord activity
Anesthesia, somatic and visceral areflexia, paralysis and atonia below level of lesion
Usually resolves within several weeks, and have an evolving state of hyperreflexia and spasticity

54. More slowly developing conditions
May have hyperreflexia and hyperrerflexia from their onset
Hyperreflexia eventually present in all spinal cord disorders, particularly in the extermities
Some diseases damage both UMN and LMN (ALS)
As LMN are destroyed, areflexia and hypotonia may predominate

55. Babinski’s sign
Early sign on UMN disease
Level of abnormal reflexes can be an indicator of the site of spinal cord lesion

56. Pelvic Organ Function Bowel Bladder Genital organs
Involve sympathetic, parasympathetic and somatic nervous systems

57. Anatomy of the bladder Muscles Note the innervation Bladder wall
Internal sphincter
External sphincter
Note the innervation

58. Control of the bladder - infant
All involuntary control
Bladder filling
Sympathetic fibers from T11 to L2
Inhibit contraction of bladder wall
Maintain contraction of internal sphincter

60. Bladder Emptying
When the bladder becomes full, stretch receptors in the bladder wall are activated
Afferent information goes to the reflex center in the sacral cord
Parasympathetic fibers produce contraction of bladder wall and open internal sphincter
Somatic fibers (S2-S4) open the external sphincter

61. Bladder Emptying Sensory afferents Parasympathetic efferents Somatic

62. Reflexive bladder control
Does not involve conscious control
Requires
Sensory afferents
T11 to L2 and S2-S4 spinal cord levels
Somatic, sympathetic and parasympathetic efferents

63. Voluntary Control
Sensory information sent from reflex center in the spinal cord to the brain
If the decision is made for micturition
Corticospinal inhibition of external sphincter muscle
Brainstem pathways to autonomic efferents

64. Bowel control Very similar to bladder control
Stimulus is stretch of the rectum

65. Sexual function Erection of penis or clitoris Ejaculation
Parasympathetic fibers from S2-S4
Ejaculation
Sympathetic fibers from L1-L2
Pudendal nerve from S2-S4, somatic efferent