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Neuroscience Exam III > Clinical Aspects of Spinal Cord > Flashcards

Clinical Aspects of Spinal Cord Flashcards

1
Q

What are the common features of a Conscious Sensory Pathway?

A

1 neuron: pseudounipolar neuron who cell body is the the spinal ganglia
2 neuron: located in the spinal cord(pain/temp) and medulla (2pt./prioprio) has decussated
3 neuron: dorsal thalamus (usually VPL)
Primary Somesthetic cortex

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2
Q

All motor activity is base upon ____ ____ ____?

A

Spinal Cord Reflexes

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3
Q

Describe Myotatic reflex.

A

Stimulus: rapid stretch

receptor: neuromuscular spindle
afferent: neuron
efferent: alpha motor neuron
effector: extrafusal muscles
response: contraction of the muscles

Ex: patellar tendon

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4
Q

What does the gamma efferent pathway control?

A

Muscle tone and proprioceptive input to the CNS

receives input from descending pathways( frontal lobes, basal ganglia or reticular formation)

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5
Q

Describe the gamma efferent pathway.

A

gamma motor neurons travel through ventral root and spinal nerve terminating on specialized intrafusal muscle fibers encapsulated in the NMS
Intrafusal muscle cells control the amount of tension and sensitivity of the NMS (tighter spindles are more sensitive to being stretched)

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6
Q

What are the causes of the gamma efferent pathway?

A

increased gamma motor activity cause hypertonia and hypereflexia

decreased gamma motor activity causes hypotonia and hyporeflexia

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7
Q

What are the 5 sensory nuclei? and Function?

A 
Substantia Gelationsa (SG): pain/temp
Nucleus Proprius (NP): pain/ temp (indirect spinothalamic pathway) 
Nucleus Dorsalis: unconscious proprioceptive pathway 
Visceral Afferent nucleus: visceral sensory integration and reflex
Intermediate Gray: sensorimotor integration center
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8
Q

What are the 6 motor nuclei (and function)?

A

Medial Motor Cell Column( MMCC): axial musculature
Lateral Motor Cell Column: (LLCC): muscles of extremities
Phrenic Nucleus: subdivision of MMCC and Respiratory diaphragm
Spinal Accessory Nucleus: cont. w/ nucleus ambigus SCM and Trap
Intermediolateral Nucleus: Send preganglionic sympathetic fibers to visceral structures
Sacral Autonomic nucleus: send preganglionic parasympathetic fiber to bowel and bladder

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9
Q

What are the tracts of the spinal cord subdivide into sensory and motor tracts?

A 
Sensory:
1.dorsal root
2. posterior column
3. lateral spinothalamic tracts
4. Anterior White Commissure 
Motor:
5. lateral corticospinal tract
6. lateral reticulospinal tract 
7. anterior horns
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10
Q

Describe a lesion to the dorsal root?

A

anesthesia of the corresponding sensory dermatome
affects motor unit= diminished muscle tone and reflex
as a result atonic bladder

EX: Tabes dorsalis

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11
Q

Overview of Posterior column.

A

descending and acending fibers conveying info. about 2pt./proprio

  1. Long ascending fibers: form FG and FC
  2. short ascending fiber: apart of the ventral spinothalamic pathway (passive touch and pressure info)
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12
Q

Overview of the lateral Corticospinal Tract (LCST).

A 
LCST descends in the lateral funiculus  and terminates in the anterior horns and IG at all spinal levels 
function via intrinsic spinal reflex circuits
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13
Q

Overview of the Lateral Spinothalamic Tract (LSTT).

A

LSTT ascends as a somatotopically organized tract in the anterolateral portion of the spinal cord. It conveys pain/temp info. to the VPL

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14
Q

Overview of the Reticulospinal Tract.

A

Principal descending pathway of the autonomic responses (slow pain fibers (‘C’ fibers))
bladder and bowel function

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15
Q

Overview of Anterior White Commissure.

A

2 axons from the SG that decussate in the AWC and ascend as the LSTT.

a lesion results in bilateral loss of pain/temp in the associated spinal dermatomes

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16
Q

Overview of the Anterior (Ventral) Motor Neurons.

A

anterior horn as both alpha and gamma motor neurons

alpha axons travel into ventral root and innervate striated muscles (LMN)

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17
Q

How does a lesion of the dorsal root present?

A

ipsilateral sensory dermatomal anesthesia

ipsilateral diminished muscle tone/reflex

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18
Q

How does a lesion of the posterior column present?

A

ipsilateral loss of 2pt./proprio below level of lesion

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19
Q

How does a lesion of the lateral funiculus present?

A

ipsilateral UMN paralysis/paresis below level of lesion

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20
Q

How does a lesion of the anterior funiculus present?

A

contralateral loss of pain and temperature below the level of the lesion
ipsilateral LMN paralysis at the level of lesion
If the lesion is bilateral, volitional control of bladder and bowel

21
Q

Describe the pathway of the Posterior column/Medial Lemniscal System.

A

1 neurons: cell bodies of spinal ganglia enter spinal cord and form FG or FC travel to the medulla terminating at the Tuberculum grascilis or Tuberculum cuneatus.
2 neurons: arise the in medulla from the nucleus gracilis/cuneatus, then decussate as internal arcuate fibers and form the Medial Lemniscus terminating in the dorsal thalamus (VPL)
3 neurons: arises at the VPL send axons to the primary somesthetic cortex via the internal capsule

22
Q

Describe the somatotopic organization of the Medial Lemnsicus.

A

medulla: LE fibers are anterior and UE fiber are located in the posterior
pons: UE and LE fiber are located in the medial and lateral aspects, respectively
midbrain: LE fibers are posterolateral and UE are anteromedial

23
Q

Describe the 3 unilateral lesions of the posterior Column/medial lemniscal system

A
  1. unilateral lesion of the fasiculus gracilis: ipsilateral loss of 2pt/proprio from lower body
  2. Unilateral lesion of the Fasiculus cuneatus: ipsilateral loss of 2pt/proprio from the upper of of the body and face
  3. Unilateral lesions of the Medial Lemniscus: contralateral loss of 2pt/proprio
24
Q

Describe the Ventral Spinothalamic Pathway.

A

Modality: light touch, crude tactile sensation, and pressure
Receptors: free nerve ends, merkel’s tactile disc
1 neurons: central process bifurcates, and ascends 6-10 seg.
2 neurons: in Nucleus Proprius, axon decussates in AWC and ascends as ASTT combs w/ LSTT=spinal lemnsicus
3 neuron: in VPL of thalamus, projects an axon to the primary somesthetic cortex

25
Q

How does a unilateral lesion to the Ventral Spinothalamic Tract present?

A

difficult of loss crude touch sensations (mult. inputs)
and bilaterality

may be masked by the posterior column/medial lemniscus system

26
Q

How does a unilateral lesion of the spinal lemniscus present?

A

contralateral hemianalgesia and thermal hemianesthesia,

loss of passive touch may be masked by the intact posterior column/medial lemniscus system.

27
Q

Describe the Spinocerebellar Pathways.

A

modality: unconscious info. about motor coordination
1. Dorsal Spinocerebellar Tract (DSCT): precise coord., postural adjustments, and movements of individual muscles of the lower limbs and body.
2. Ventral Spinocerebellar Tract(VSCT): gross postural adjustments, and overall proprio of the lower limb.
3. Cuneocerebellar Tract (direct arcuate Fibers): fine coord., postural adjustments, and precise movement of individ. muscles of the UE

28
Q

Describe the Direct Spinothalamic Pathway:

A

Modality: alpha delta pain fibers
1 neuron: spinal ganglia send central process into the spinal cord (SG)
2 neuron: synapse w/ 1 in the SG send axons through the AWC to form the lateral spinothalamic Tract (LSTT)
3 neuron: synapse in the VPL (dorsal thalamus) projects to the primary somesthetic cotrx

29
Q

How does a unilateral lesion of the spinal lemniscus present?

A

contralateral hemianalgesia and thermal hemianesthesia

30
Q

How does a unilateral lesion of the later Spinothalamic Tract present?

A

contralateral loss of pain/temp sensation two sensory dermatomal segments below the level of the lesion

31
Q

Describe the Indirect Spinothalamic pathway.

A

modality: ‘slow’ pain pathway using ‘c’ fiber (unmyelinated)
1 neurons: enter spinal cord at dorsolateral fasciculus of Lissaur which sends collaterals terminals to the nucleus proprius
2 neurons: course bilaterally in the anterior, lateral and posterior regions of the fasciculus proprius terminating on interneurons, forming intersegmental reflexes
some pain info. ascends from NP to the thamalus as spinorecticular fibers which diffuse forming the reticular formation (surrounds the gray matter of the spinal cord)
these fibers terminate in the midline reticular formation of the brainstem, hypothalamus

32
Q

How do a lesion of the spinoreticular fibers present?

A

no significant sensory deficits due to its bilateral nature

33
Q

Describe the the corticospinal pathway (UMN)?

A

Primary Motor Cortex, to the precentral gyrus, to the corticospinal tract, then posterior limb of internal capsule, cerebral pedunce, pyramid, pyramidal decussations,

forming the Lateral corticospinal tract
involved in fractionation of movement
fibers that do not decussate form the anterior corticospinal tract

34
Q

describe the descending tracts of the lateral corticospinal tracts.

A

descending tracts convey facilitatory or inhibitory influences upon UMN. These terminate in lower Motor neuron “pool” in the IG. The ‘pool’ functions to integrating descending motor info. with the incoming “current status” sensory information

35
Q

How does a unilateral lesion of the corticospinal tract present?

A

contralateral spastic hemiplegia or spastic hemiparesis

36
Q

How does a unilateral lesion of the lateral corticospinal tract?

A

ipsilateral paralysis or paresis of the distal limb musculature innervated by the spinal segment below the level of the lesion

37
Q

Describe the Lateral Reticulosponal Tract.

A

originates in the a group of medullary reticular nuclei
travel bilaterally descend adjacent to the spinal gray in the anterolateral funiculus, and terminate in the IG of all level of the spinal cord

autonomic responses

38
Q

Urinary Bladder Reflex

A

bladder fills up: stretch receptors are activated traveling to the VAN located in sacral seg( S2-4)
interneurons convey the stim. to the sacral autonomic nucleus (SAN). Efferent fibers then stim. the muscles of the bladder

detrusor muscles is under parasympathetic control of sacral spinal cord seg (S2-4)

39
Q

How does a lesion of the LMN present?

A 
Flaccid paralysis
Areflexia
Atonia 
Atropy 
Fasciculations
40
Q

What is the anterior white commissure?

A

comprised secondary axons in the direct spinothalamic pathway (pain and temperature)

41
Q

How does a central cord lesions, vascular occlusion (syringomyelia or tumors) on the AWC present?

A

bilateral loss of pain and temperature of the corresponding sensory dermatome

42
Q

What are the ascending tracts?

A

dorsal spinocerebelllar tract
ventral spinocerebellar tract
ventral spinothalamic tract
Spinoreticular Fibers

43
Q

Describe the clinical presentation of Tabes Dorsalis.

A

It is a meningovascular inflammation of the blood vessels as they pierce through the pia junction of the dorsal root and posterior column

Lighting pains of lower limbs: hypersensitivity
Atonic bladder and painless retention of urine
locomotor ataxia
loss of proprio info of LE
postive Romberg test

44
Q

Describe the clinical presentation of Poliomyeltis.

A

involves the motor neurons of the anterior horns and the CN motor nuclei

present with fever, vomiting, neck stiffness, pain in back and LE

flaccid paralysis, atonia, areflexia, fasciculations, atrophy

45
Q

Describe the clinical presentation of complete Transection of the Spinal Cord.

A

at level C5-6: quadriplegia
at level T1-L2: paraplegia

3 phases of spinal cord lesions:

  1. spinal shock: loss of all sensation, reflex activities, bilateral flaccid paralysis, atonic bladder, Horner’s
  2. appearance of any spinal reflex activity distal to the lesion
  3. affected muscle groups will exhibit tonic muscles spasms of the extensors
46
Q

Describe the clinical presentation of Brown-Sequard Syndrome.

A

unilateral wound to the spinal cord

  1. ipsilateral loss of proprio/2pt (posterior columns)
  2. ipsilateral spastic paralysis ( descending motor tracts)
  3. Contralateral loss of pain and temperature (sensation from the body 2 sensory dermatomal segments below the level of the lesion (LSTT)
47
Q

Describe the clinical presentation of Syringomyelia.

A

a gross cavitation and gliosis of the central canal occurring in the cervical regions of the spinal cord ( secondary to central cord syndrome)

  1. destruction of AWC: bilateral bloss of pain/temp in UE
  2. destruction of the LCST (UMN) results in spastic paralysis, hyperreflexia, and hypertonia of the LE
  3. The anterior horn (LMN) may be destroyed unilateraly or bilaterally: flaccid paralysis, atrophy, atonia, areflexia
  4. some posterior column may be affected resulting in loss of ipsilateral anesthesia
48
Q

Describe the clinical presentation of Amyotrophic Lateral Sclerosis.

A

NO SENSORY DEFICITS

LMN: anterior horn, hypoglossal nucleus, nucleus ambigus,
facial motor nucleus
UMN: chronic, progressive degeneration of the CST

Neuroscience Exam III (9 decks)

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