Clinical Aspects of Spinal Cord

Question 1

What are the common features of a Conscious Sensory Pathway?

Answer 1

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

Question 2

All motor activity is base upon ____ ____ ____?

Answer 2

Spinal Cord Reflexes

Question 3

Describe Myotatic reflex.

Answer 3

Stimulus: rapid stretch

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

Ex: patellar tendon

Question 4

What does the gamma efferent pathway control?

Answer 4

Muscle tone and proprioceptive input to the CNS

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

Question 5

Describe the gamma efferent pathway.

Answer 5

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)

Question 6

What are the causes of the gamma efferent pathway?

Answer 6

increased gamma motor activity cause hypertonia and hypereflexia

decreased gamma motor activity causes hypotonia and hyporeflexia

Question 7

What are the 5 sensory nuclei? and Function?

Answer 7

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

Question 8

What are the 6 motor nuclei (and function)?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

Describe a lesion to the dorsal root?

Answer 10

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

EX: Tabes dorsalis

Question 11

Overview of Posterior column.

Answer 11

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)

Question 12

Overview of the lateral Corticospinal Tract (LCST).

Answer 12

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

Question 13

Overview of the Lateral Spinothalamic Tract (LSTT).

Answer 13

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

Question 14

Overview of the Reticulospinal Tract.

Answer 14

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

Question 15

Overview of Anterior White Commissure.

Answer 15

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

Question 16

Overview of the Anterior (Ventral) Motor Neurons.

Answer 16

anterior horn as both alpha and gamma motor neurons

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

Question 17

How does a lesion of the dorsal root present?

Answer 17

ipsilateral sensory dermatomal anesthesia

ipsilateral diminished muscle tone/reflex

Question 18

How does a lesion of the posterior column present?

Answer 18

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

Question 19

How does a lesion of the lateral funiculus present?

Answer 19

ipsilateral UMN paralysis/paresis below level of lesion

Question 20

How does a lesion of the anterior funiculus present?

Answer 20

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

Question 21

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

Answer 21

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

Question 22

Describe the somatotopic organization of the Medial Lemnsicus.

Answer 22

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

Question 23

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

Answer 23

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

Question 24

Describe the Ventral Spinothalamic Pathway.

Answer 24

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

Question 25

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

Answer 25

difficult of loss crude touch sensations (mult. inputs) and bilaterality may be masked by the posterior column/medial lemniscus system

Question 26

How does a unilateral lesion of the spinal lemniscus present?

Answer 26

contralateral hemianalgesia and thermal hemianesthesia, | loss of passive touch may be masked by the intact posterior column/medial lemniscus system.

Question 27

Describe the Spinocerebellar Pathways.

Answer 27

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

Question 28

Describe the Direct Spinothalamic Pathway:

Answer 28

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

Question 29

How does a unilateral lesion of the spinal lemniscus present?

Answer 29

contralateral hemianalgesia and thermal hemianesthesia

Question 30

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

Answer 30

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

Question 31

Describe the Indirect Spinothalamic pathway.

Answer 31

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

Question 32

How do a lesion of the spinoreticular fibers present?

Answer 32

no significant sensory deficits due to its bilateral nature

Question 33

Describe the the corticospinal pathway (UMN)?

Answer 33

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

Question 34

describe the descending tracts of the lateral corticospinal tracts.

Answer 34

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

Question 35

How does a unilateral lesion of the corticospinal tract present?

Answer 35

contralateral spastic hemiplegia or spastic hemiparesis

Question 36

How does a unilateral lesion of the lateral corticospinal tract?

Answer 36

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

Question 37

Describe the Lateral Reticulosponal Tract.

Answer 37

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

Question 38

Urinary Bladder Reflex

Answer 38

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)

Question 39

How does a lesion of the LMN present?

Answer 39

``` Flaccid paralysis Areflexia Atonia Atropy Fasciculations ```

Question 40

What is the anterior white commissure?

Answer 40

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

Question 41

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

Answer 41

bilateral loss of pain and temperature of the corresponding sensory dermatome

Question 42

What are the ascending tracts?

Answer 42

dorsal spinocerebelllar tract ventral spinocerebellar tract ventral spinothalamic tract Spinoreticular Fibers

Question 43

Describe the clinical presentation of Tabes Dorsalis.

Answer 43

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

Question 44

Describe the clinical presentation of Poliomyeltis.

Answer 44

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

Question 45

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

Answer 45

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

Question 46

Describe the clinical presentation of Brown-Sequard Syndrome.

Answer 46

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)

Question 47

Describe the clinical presentation of Syringomyelia.

Answer 47

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

Question 48

Describe the clinical presentation of Amyotrophic Lateral Sclerosis.

Answer 48

NO SENSORY DEFICITS LMN: anterior horn, hypoglossal nucleus, nucleus ambigus, facial motor nucleus UMN: chronic, progressive degeneration of the CST