Download MBBS Anatomy PPT 50 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,

3. Blood vessels.

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surrounds the grey matter

white colour

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myelinated nerve fibres.

Sensory

Motor

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Association


Anterior white column

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(or funiculus)

Lateral white column
(or funiculi)

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Posterior white
column (or funiculus)

Anterior white
commissure.

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Collection of nerve fibres

with same

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Origin,

Course,

Termination

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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

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

Lateral spinothalamic tract

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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

gelatinosa/

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Rexed III-VII

1st Order Neuron

Posterior root ganglion

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Decussation

Receptor

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Free nerve endings

Anterior spinothalamic tract

Destination

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Posterior central gyrus

3rd Order Neuron Ventral posterolateral

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nucleus of Thalamus

Pathways

Anterior spinothalamic,

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Medial lemniscus

2nd Order

? Substantia gelatinosa/

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Neuron

Rexed III-VII

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1st Order Neuron

Posterior root ganglion

Decussation

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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

synapsing with 2nd order neurons in substantia gelatinosa.

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Antero-

Spinotectal tract

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Spinoreticular tract

Descending autonomic tract

Spino-olivary tract

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Dorsal Column

Destination

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Posterior central gyrus

3rd Order Neuron

Ventral posterolateral

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nucleus of Thalamus

2nd Order Neuron

Nuclei gracilis and cuneatus in

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medulla oblagata
Few IV-VI

FC

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FG

Pathways

Ipsilateral Fasciculi gracilis & cuneatus

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Medial lemniscus

T 1-6, C

1st Order Neuron

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Posterior root ganglion

Receptors

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

T 7-12, L, S

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Axons of the second-order neurons

Called Internal arcuate fibres cross the

median plane.

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Decussate with the corresponding fibres of

the opposite side in the medulla as sensory

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FC

FG

Decussation

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Fibres ascend as a single compact bundle

T 1-6, C

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called medial lemniscus through the

brainstem.

T 7-12, L, S

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Spinotectal tract

Spinoreticular tract

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Descending autonomic tract

Spino-olivary tract

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Spinocerebellar Tracts

Destination

Cerebellar Cortex

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Through Superior & Inferior Cerebellar peduncles

Pathways

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

2nd Order Neuron

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

1st Order Neuron

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

Receptors

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muscle spindles & tendon organs, joint receptors

Spinotectal tract

Spinovisual reflexes

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

Spinoreticular tract

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Reticular formation,
Levels of consciousness
Pain perception

Spino-olivary tract

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Conveys cutaneous and proprioceptive
information to cerebellum

Spino-cervicothalamic

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Hair movement, pinch, pressure,

pathway

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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)

Pass through

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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

Pathway

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Corticospinal tracts

Termination

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

also known as pyramidal tracts.

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

especially distal ends of limbs

gives branches to cerebral cortex,

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? basal nuclei,
? red nucleus,
? olivary nuclei,
? reticular formation.

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These branches keep the subcortical regions aware about the

cortical motor activity.

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Origin

Red nucleus of midbrain

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Site of

Immediately in midbrain

crossover

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Pathway

Rubrospinal tract

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Destination

Motor neurons in grey matter

Function

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Facilitates activity of flexor muscles and
inhibits activity of extensor muscles in
the upper limb

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? Red nucleus receive afferent impulses through connections with the :
? 1. cerebral cortex
? 2. cerebellum.
? 3. Globus Pallidus
? Extends as far as corticospinal tract

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? Cortico-rubral connections from ipsilateral red nucleus
? indirect pathway by which the cerebral cortex and the cerebellum

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

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Extrapyramidal Tracts

Reticulospinal tract

Inhibit or facilitate voluntary movement, reflex activity,

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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

The patient will

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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

point of entrance of the posterior root into the

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spinal cord,

specially in the lower thoracic and lumbosacral

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regions.

Results in loss of some sensation &

hypersensitivity of others.

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Upper Motor Neuron (UMN) Lesions:

Lesions of corticospinal tracts (Pyramidal Tracts)

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Lesions of Extrapyramidal Tracts

Lesions of corticospinal tracts (Pyramidal Tracts)

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Babinski sign is present.

superficial abdominal reflexes are absent.

cremasteric reflex is absent.

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There is loss of performance of fine-skilled,

voluntary movements, especially at the distal

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end, of the limbs.

Lesions of Extrapyramidal Tracts lesions:

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

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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

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

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Clinical signs:

1.

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Flaccid paralysis

2.

Muscular Atrophy

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3.

Loss of muscular reflexes

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4. Muscular fasciculation

5. Muscular contracture and degeneration .

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Following a spinal cord injury there will be :

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.

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

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.

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

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.

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

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

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following pathways most likely have been damaged?

A.

Lateral spinothalamic

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B.

Ventral spinothalamic

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C.

Dorsal spinocerebellar

D.

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Cuneocerebellar

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

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

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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.

Complete transection of the spinal cord

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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?

A.

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Spastic paralysis

B.

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Hyperreflexia

C.

Increased muscle tone

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D.

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

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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.

Lesion the most lateral aspect of the left spinothalamic tract

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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

D.

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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

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

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A.

Touch, pressure, vibratory sense from ipsilateral leg

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B.

Pain and temperature sense from contralateral leg

C.

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Pain from ipsilateral face

D.

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Pain and temperature sense from contralateral arm

5 year painter was rushed to the ER after he fell from a high building and fractured

his cervical vertebra and damaged his spinal cord. During examination of his

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reflexes immediately after the accident, which of the following are most likely to be

seen?

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A.

Increased reflexes

B.

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Decreased reflexes

C.

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Rigidity

D.

Fasiculations

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