Download MBBS Anatomy PPT 75 Spinal Cord Tracts Notes

White Matter- classification

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Tracts

Ascending Tracts

Descending Tracts

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Clinical Correlates


Mixture of:

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1. Nerve fibers,

2. Neuroglia,

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3. Blood vessels.

surrounds the grey matter

white colour

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myelinated nerve fibres.

Sensory

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Motor

Association

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Anterior white column
(or funiculus)

Lateral white column
(or funiculi)

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Posterior white
column (or funiculus)

Anterior white

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commissure.

Collection of nerve fibres

with same

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Origin,

Course,

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Termination


Spinotectal tract

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Spinoreticular tract

Descending autonomic tract

Spino-olivary tract

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Lateral Spinothalamic Tract

Pain,

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Thermal sensation

Anterior Spinothalamic Tract

Crude (Light) touch, (non-discriminative touch)

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Pressure
Tickle, Itch

Dorsal Column

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Fine touch (discriminative touch)

Fasciculus gracilis

Two point discrimination

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Fasciculus cuneatus

Vibration
Conscious Proprioception

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Anterior Spinocerebellar Tract

Unconscious Proprioception
Gross movements

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Posterior Spinocerebellar Tract

Unconscious Proprioception
Fine movements

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Spinotectal tract

Spinoreticular tract

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Descending autonomic tract

Spino-olivary tract

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Lateral spinothalamic tract

Destination

Posterior central gyrus

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3rd Order Neuron

Ventral posterolateral
nucleus of Thalamus

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Pathways

Lateral spinothalamic,
Spinal lemniscus? Spinotectal

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2nd Order Neuron

? Substantia

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gelatinosa/
Rexed III-VII

1st Order Neuron

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Posterior root ganglion

Decussation

Receptor

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Free nerve endings

Anterior spinothalamic tract

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Destination

Posterior central gyrus

3rd Order Neuron Ventral posterolateral

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nucleus of Thalamus

Pathways

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Anterior spinothalamic,
Medial lemniscus

2nd Order

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? Substantia gelatinosa/

Neuron

Rexed III-VII

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1st Order Neuron

Posterior root ganglion

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Decussation

Receptors

Pacinian Corpuscle

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Posterolateral tract of Lissauer

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1st order neuron enters posterior horn & divides into ascending and

descending branches that travel for 1-2 segments, then terminate

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synapsing with 2nd order neurons in substantia gelatinosa.

Antero-

Spinotectal tract

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Spinoreticular tract

Descending autonomic tract

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Spino-olivary tract


Dorsal Column

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Destination

Posterior central gyrus

3rd Order Neuron

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Ventral posterolateral
nucleus of Thalamus

2nd Order Neuron

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Nuclei gracilis and cuneatus in
medulla oblagata
Few IV-VI

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FC

FG

Pathways

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Ipsilateral Fasciculi gracilis & cuneatus
Medial lemniscus

T 1-6, C

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1st Order Neuron

Posterior root ganglion

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Receptors

Meissner's corpuscles, Pacinian corpuscles,
muscle spindles & tendon organs

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T 7-12, L, S

Axons of the second-order neurons

Called Internal arcuate fibres cross the

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median plane.

Decussate with the corresponding fibres of

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the opposite side in the medulla as sensory

FC

FG

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Decussation

Fibres ascend as a single compact bundle

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T 1-6, C

called medial lemniscus through the

brainstem.

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T 7-12, L, S


Spinotectal tract

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Spinoreticular tract

Descending autonomic tract

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Spino-olivary tract

Spinocerebellar Tracts

Destination

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Cerebellar Cortex

Through Superior & Inferior Cerebellar peduncles

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Pathways

Anterior Spinocerebellar tracts (Superior)
Posterior Spinocerebellar tracts (Inferior)

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2nd Order Neuron

Nucleus Dorsalis/ Clarke's column C8-L3/4
V-VII

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1st Order Neuron

Collateral branches of Ascending tracts of Dorsal Column
from dorsal root ganglion

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Receptors

muscle spindles & tendon organs, joint receptors

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Spinotectal tract

Spinovisual reflexes
Movements of the eyes & head in response to
the source of the stimulation

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Spinoreticular tract

Reticular formation,
Levels of consciousness

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Pain perception

Spino-olivary tract

Conveys cutaneous and proprioceptive

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information to cerebellum

Spino-cervicothalamic

Hair movement, pinch, pressure,

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pathway

thermal stimuli, noxious stimuli
Origin

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Primary motor cortex (area 4),
secondary motor cortex (area 6),
parietal lobe (areas 3, 1, and 2)

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Pass through

Corona radiata,
posterior limb of Internal Capsule
middle 3/5 of basis pedunculi of midbrain

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Site of crossover

pyramids of medulla

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Pathway

Corticospinal tracts

Termination

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98% on contralateral alpha and gamma motor neurons
in grey matter or interneurons.

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also known as pyramidal tracts.

Controls rapid, skilled, non-postural, voluntary movements,

especially distal ends of limbs

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gives branches to cerebral cortex,

? basal nuclei,
? red nucleus,

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? olivary nuclei,
? reticular formation.

These branches keep the subcortical regions aware about the

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cortical motor activity.


Origin

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Red nucleus of midbrain

Site of

Immediately in midbrain

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crossover

Pathway

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Rubrospinal tract

Destination

Motor neurons in grey matter

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Function

Facilitates activity of flexor muscles and
inhibits activity of extensor muscles in

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the upper limb

? Red nucleus receive afferent impulses through connections with the :
? 1. cerebral cortex
? 2. cerebellum.

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? 3. Globus Pallidus
? Extends as far as corticospinal tract
? Cortico-rubral connections from ipsilateral red nucleus
? indirect pathway by which the cerebral cortex and the cerebellum

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can influence the activity of motor neurons of the spinal cord.
Extrapyramidal Tracts

Reticulospinal tract

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Inhibit or facilitate voluntary movement, reflex activity,
assist hypothalamus controls sympathetic,
parasympathetic outflows.

Tectospinal tract

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Reflex postural movements of head concerning visual
stimuli

Vestibulospinal tract

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Unconscious maintenance of posture and balance; acts
on extensors
mediates head & neck movements in response to
vestibular sensory input

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Descending autonomic Control sympathetic and parasympathetic
fibers

systems

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Anterior Spinothalamic Tract

contralateral loss of light touch sensations below the level of the

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lesion

contralateral loss of pressure sensations below the level of the lesion

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The patient will

not feel the light touch of a piece of cotton placed against the skin

and cant feel pressure from a blunt object placed against the skin.

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is caused by syphilis.

a selective destruction of nerve fibres at the

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point of entrance of the posterior root into the

spinal cord,

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specially in the lower thoracic and lumbosacral

regions.

Results in loss of some sensation &

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hypersensitivity of others.


Upper Motor Neuron (UMN) Lesions:

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Lesions of corticospinal tracts (Pyramidal Tracts)

Lesions of Extrapyramidal Tracts

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Lesions of corticospinal tracts (Pyramidal Tracts)

Babinski sign is present.

superficial abdominal reflexes are absent.

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cremasteric reflex is absent.

There is loss of performance of fine-skilled,

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voluntary movements, especially at the distal

end, of the limbs.
Lesions of Extrapyramidal Tracts lesions:

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Spastic paralysis, (lower limb extended, and the upper limb flexed),

Exaggerated deep muscle reflexes in some flexors,

Clasp-knife reaction -the muscles, after resistance on stretching,

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suddenly give way.

By any lesion ( ex. Poliomyelitis) destroying neurons in the anterior grey

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column or its axon in the anterior root or spinal nerve.

Clinical signs:

1.

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Flaccid paralysis

2.

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Muscular Atrophy

3.

Loss of muscular reflexes

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4. Muscular fasciculation

5. Muscular contracture and degeneration .
Following a spinal cord injury there will be :

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a short term loss of all neurological activity below the level of injury.

loss of motor, sensory reflex & autonomic function.

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due to temporary physiologic disorganisation of spinal cord function,

may last 30-60 minutes or up to 6 weeks.

It can be caused by fracture dislocation of the vertebral column,

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Clinical features :

1. Bilateral LMN paralysis

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2. Bilateral spastic paralysis below the level of the lesion

3. Bilateral loss of all sensations below the level of the lesion.

4. Bladder and bowel functions are no longer under voluntary control

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1. Bilateral LMN paralysis in the segment of lesion,

2. Bilateral spastic paralysis below level of the lesion,

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3. Bilateral loss of pain, temprature & light touch

below the level of the lesion,

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4. Two point discrimination & vibratory and

proprioception sensations are preserved.

1. Bilateral LMN paralysis in the segment of lesion,

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2. Bilateral spastic paralysis below the level of the

lesion with characteristic sacral sparing,

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3. Bilateral loss of pain, temperature & light touch and

pressure sensations below the level of the lesion with

characteristic sacral sparing.

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A 36 year old male is observed to have difficulty in walking during a clinic visit.

Testing indicates that his joint position sense is intact. However, his reflexes in his

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lower limbs are diminished. Based on the findings in this patient, which of the

following pathways most likely have been damaged?

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A.

Lateral spinothalamic

B.

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Ventral spinothalamic

C.

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Dorsal spinocerebellar

D.

Cuneocerebellar

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A 19 year old gang member presented in the ER with a stab wound of the neck.

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Neurological examination revealed left hemiparesis with complete loss of vibratory

and joint position sense below C6 on the same side as the weakness. Loss of pain

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and temperature sensation was elicited on the left at C6 only and on the right

below C6. An MRI of the cervical spinal cord will reveal which of these findings?

A.

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Hemisection of the left spinal cord

B.

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Complete transection of the spinal cord

C. Lesion of the left anterolateral white mater only of the spinal cord

D. Damage to the cervical dorsal roots at C6 on the left side only

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A patient has an injury that results in damage to the lower motor neurons. Which of

the following would you expect to see in the patient?

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A.

Spastic paralysis

B.

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Hyperreflexia

C.

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Increased muscle tone

D.

Flaccid paralysis

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A pain researcher wants to make a lesion to the Spinothalamic tract so that his

subjects feel no pain and temperature sensation from the right leg, but leaves pain

and temperature sensation rostral to the arm. Where would you advise this

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researcher to make his lesion?

A.

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Lesion the most lateral aspect of the left spinothalamic tract

B.

Lesion the most medial aspect of the left spinothalamic tract

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C.

Lesion the most lateral aspect of the right spinothalamic tract

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D.

Lesion the most medial aspect of the right spinothalamic tract

During a play-off game, a college hockey player is struck hard on the back of his

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neck with a hockey stick. A CT scan reveals a bone fragment lodged into the

medial aspect of his dorsal columns in the cervical spinal cord. Which of the

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following functions will most likely be affected given this patient's presentation?

A.

Touch, pressure, vibratory sense from ipsilateral leg

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B.

Pain and temperature sense from contralateral leg

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C.

Pain from ipsilateral face

D.

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Pain and temperature sense from contralateral arm