White Matter- classification
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TractsAscending 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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MotorAssociation
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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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TerminationSpinotectal tract
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Spinoreticular tractDescending autonomic tract
Spino-olivary tract
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Lateral Spinothalamic Tract
Pain,
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Thermal sensationAnterior Spinothalamic Tract
Crude (Light) touch, (non-discriminative touch)
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PressureTickle, 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 tractSpino-olivary tract
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Lateral spinothalamic tractDestination
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 ganglionDecussation
Receptor
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Free nerve endings
Anterior spinothalamic tract
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DestinationPosterior 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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DecussationReceptors
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 tractDorsal Column
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DestinationPosterior 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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FCFG
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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ReceptorsMeissner's corpuscles, Pacinian corpuscles,
muscle spindles & tendon organs
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T 7-12, L, SAxons 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 sensoryFC
FG
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Decussation
Fibres ascend as a single compact bundle
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T 1-6, Ccalled 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 tractSpinocerebellar Tracts
Destination
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Cerebellar Cortex
Through Superior & Inferior Cerebellar peduncles
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PathwaysAnterior Spinocerebellar tracts (Superior)
Posterior Spinocerebellar tracts (Inferior)
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2nd Order NeuronNucleus Dorsalis/ Clarke's column C8-L3/4
V-VII
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1st Order NeuronCollateral branches of Ascending tracts of Dorsal Column
from dorsal root ganglion
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Receptorsmuscle spindles & tendon organs, joint receptors
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Spinotectal tractSpinovisual 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 perceptionSpino-olivary tract
Conveys cutaneous and proprioceptive
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information to cerebellumSpino-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 throughCorona 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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PathwayCorticospinal 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 midbrainSite of
Immediately in midbrain
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crossover
Pathway
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Rubrospinal tractDestination
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 willnot 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 lumbosacralregions.
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 distalend, 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 Atrophy3.
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 lesion3. 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 andproprioception 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 andpressure 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 spinocerebellarD.
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 rightbelow 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 cordC. 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 toneD.
Flaccid paralysis
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A pain researcher wants to make a lesion to the Spinothalamic tract so that hissubjects 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 tractB.
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
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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RigidityD.
Fasiculations
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