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Spinal Cord Injuries.

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Presentation on theme: "Spinal Cord Injuries."— Presentation transcript:

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

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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

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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

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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

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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

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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


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