Download Dorsal Spinocerebellar Tract

Modalities
Touch (and Pressure), Vibration Sense, Proprioception, Kinesthesia, Stereognosis
Proprioception - sense of static and dynamic position of limbs and body
Kinesthesia - the ability to feel movements of the limbs and body
Stereognosis – ability to recognize objects based on touch alone
Today – Proprioception
 Dorsal Column-Medial Lemniscus Pathway –Fine Touch from Body
 Main Trigeminal Nucleus – Fine Touch from Head
 Cerebellar Pathways – Non-Conscious Proprioception
The Basic Plan for Somatosensory Information to
Consciousness
Quaternary (4o )
4
C
o
rte
x
:
rig
h
t
le
ft
Te r t ia r y
o
(3 )
3
Thalamus: left
•
right
•
R e c e p to r
S
e
c
o
n
d
a
ry
o
(2C
r
o
s
s
e
s
)
o
Primary (1 )
Adequate Stimulus – The stimulus
modality to which a sense organ
responds optimally.
Generator Potentials are
depolarizations in receptors that are
graded relative to the intensity and form
of the stimulus.
2
1
S k in
Serial Path to consciousness involves 4 neurons and 3 synapses
Result of a lesion at each level
Spinal
Cord
Dorsal Root
Ganglion
Action Potential
Initiation Site
left
Midline
Outside the CNS!
right
Sensory information from the body to Consciousness: 2 Systems
Anterolateral
pain & temp,
gross touch
Dorsal Column
fine touch discrimination
4th
Ventricle
Spinal
Lemni
scus
Superior
Middle
Cerebellar
Peduncle
V
Medial
Lemniscus
anterolateral
dorsal
protopathic
epicritic
primitive
recent
Spinal Lemniscus
Pontocerebellar
Fibers
Medial Lemniscus
Dorsal / Posterior
midline
1
Ventral / Anterior
Lateral
1
An important anatomical
difference is where they cross
(spinal cord vs brainstem).
Key Elements - Divisions
Dorsal Column – FAST and Discrete allowing fine
discrimination. Modality is Fine
Discrimination Touch (vibration,
pressure, conscious proprioception)
Anterolateral System = Lateral and Anterior Spinothalamic
Tracts – Slow and Crude. Modalities
are Pain, Temperature and Course
Touch.
Afferent Fiber Types – vary in conduction speed and modality
Gr
oup
FAST
I
II
II
SLOW
IV
Fiber
Type
A alpha
A beta
A delta
C
Fiber
Diamet
er (mm)
12 - 22
5 - 12
1-5
0.1 –
1.5
Conduction
Speed
(m/sec)
Entire Peripheral Nerve
Receptor
Type
Modality
80 – 120
Spindles & GTO
Conscious and
Nonconscious
Proprioception
35 – 75
Spindles &
Cutaneous
Mechanorecepto
rs
Touch,
Pressure, and
Vibration
5 – 30
Free Nerve
Endings, noci-,
thermo-, & other
mechanoreceptors
Fast Pain,
Temp, Touch
0.5 – 2.0
Free Nerve
Endings, noci-,
thermo-, & other
mechanoreceptors
Slow Pain,
Temp, Touch,
itch
Haines, p42.
Afferent Fiber Types – also vary in myelination and point of entry into the
spinal cord
Haines, Fundamental Neuroanatomy, p254
Somatosensory Information from the Body to Consciousness
Dorsal Column – Medial Lemniscus Pathway
QUATERNARY 4o
Primary Somatosensory Cortex
High degree of spatial and temporal
resolution.
4
Modalities: tactile (2-point discrimination),
vibration, pressure, position sense.
TERTIARY 3o
3
SECONDARY 2o
2
Internal Arcuate Fibers =
Sensory Decussation:
Crosses the midline
Medulla
Dorsal Funiculus
DRG
1
PRIMARY 1o
Receptor skin/muscle/tendon
MIDLINE
Spinal Cord
Thalamus - VPL
Medial Lemniscus
osum
all
nx
For
Co
rpus C
Gracilius and Cuneatus: Lower body and Upper Body Aspects of the Dorsal
Columns
i
T
h
a
l
a
m
u
s
sup
inf
Colliculi
T6+
Posterior
Intermediate Sulcus
o live
Pons
Sensory Decussation
Gracile
Cuneate
*
Spinal
Trigeminal
Nucleus
Central processes of the primary afferent’s axon are located in the
dorsal funiculus of the spinal cord.
Lower body is represented Medially = Gracilius
Upper body is represented laterally = Cuneatus
*
*
*
Pyramidal
Tract
Key Questions for the Touch Pathway from the Body
The second order neuron crosses the midline.
Where does the crossing occur for the Dorsal Column-Medial
Lemniscus System?
Second order neuron is located in the brainstem.
Therefore the CROSSING occurs in the brainstem
Medial Lemniscus – Cells of origin?
- Contralateral brainstem: Gracile Nucleus - Lower Body;
Cuneate Nucleus – Upper Body)
Medial Lemniscus – projects to (terminates in):
- Ipsilateral VPL of thalamus
Dorsal Column System
– Symptoms Associated
with Lesions
What is the symptom associated
with the lesion?
Lesions and Clinical Deficits - Syringomyelia
Gliosis and cavitation in midline of the spinal cord – CSF enters the
cord. The larger the cavitation, the more tracts affected. One possible cause is a Chiari
Malformation. Other causes include trauma, infection. (anything that compresses the
CSF)
Symptoms:
Bilateral loss of pain and temperature at the level of the lesion (segments involved).
Area of lesion
http://www.asap4sm.com/
Lesions and Clinical Deficits - Wallenberg’s
Lateral Medullary (Wallenberg’s) Syndrome – Symptoms include loss of pain and
temperature on the ipsilateral head/face, contralateral loss of pain and temperature in
the body, and ataxia.
Spinal Trigeminal Tract
Trigeminal Nucleus
Dorsal
Spinocerebellar Tract
Ventral
Spinocerebellar Tract
ALS (lateral spinothalamic tract)
Lesions and Clinical Deficits – Tabes Dorsalis
Degeneration of myelinated afferent fibers in the dorsal columns, (destroys large
diameter axons), is a late stage of syphilis.
Symptoms:
Severe deficits in touch and position sense but often little loss of temperature perception and of
nociception. Bilateral lesion = bilateral effects.
Area of Lesion
LESIONS and Clinical Deficits – Brown-Sequard Syndrome
Hemisection of the spinal cord, often in the cervical spinal cord – (it is rare for the entire
hemisection to be affected, but this does occur, more often incomplete hemisection is found).
Symptoms:
a) Loss of fine discrimination touch, vibration, and position sense ipsilaterally for body regions
from affected dermatome and down
b) Loss of pain and temperature contralaterally for body regions from affected dermatome
and down (small region of bilateral loss of pain and temp at level of lesion and 2 segments
below)
c) Motor Effects: – Ipsilateral Spasticity and Weakness
DC
Arch Neurol (2001) 58: 1470.
Non-conscious
Proprioception
Conscious Somatosensation
Spinocerebellar Tracts
BODY
HEAD
Trigeminal
System
PAIN
& Temp
Fine
Touch
Pain
Lateral
SpinoThalamic
Dorsal
Column
System
Spinal
Touch
Principal
(Main)
(IPSILATERAL)
Trigeminal Nerve – Sensory Component – pain, temperature,
touch, position sense
Trigeminal
Ganglion
Opthalmic
Maxillary
Mandibular
TRIGEMINAL NUCLEUS
Mesencephalic Nucleus (Proprioceptive)
Main Sensory Nucleus (fine touch, pressure)
Spinal Trigeminal Nucleus (pain, temp)
Trigeminal System: Touch Component
C
o
rte
x
Tr igeminal
NUCLEUS
Mesencepahl ic
VPM
PONS
1
Mandibular
MEDULLA
2
2
2
SPINAL
CORD
3
3
Pain & Temp
Main
MIDLINE
Maxillary
1
2
2
2
T
h
a
la
m
u
s
Touch
1
Spinal
Opthalmic
Br anches
of t he
Tr igeminal
(V) Ner ve
Tr igeminal
Gangl ion
1
1
1
VPL
Tr igeminal
Ner ve
4 4
VENTRAL
TRIGEMIN0THALAMIC
TRACT
Principal or Main Trigeminal Nucleus –
Touch Sensation from the Face
SI Cortex
SI Cortex
VPM
Contralateral
VPM
synapse
synapse
Dorsal
Trigeminothalamic
Tract
Principal Sensory
Nucleus
Second Order Neurons
midline
Mid Pons
cross midline
Ventral
Trigeminothalamic
Tract
Similarities Between Body and Head Pathways
The trigeminal ganglion is functionally similar to what in the body
representation pathway? Answer: Dorsal Root Ganglion
Both contain cell bodies of the first
? order neurons of what
morphological cell type? Answer: pseudounipolar neurons
The Mesencephalic Nucleus of V is a special case why?
Answer: It is the only place within the CENTRAL nervous
system that contains primary afferent cell bodies.
Key Questions for the Ventral Trigeminal Thalamic Tract
What sensory modalities are associated with the Ventral Trigeminal Thalamic
Tract at the level of the pons?
Touch (conscious proprioception), Pain & Temperature
Where are the cell bodies of origin of the Ventral Trigeminal Thalamic Tract?
Contralateral Trigeminal Nucleus (Spinal & Main Components)
Where does the VTT terminate?
Ipsilateral Ventral Posterior MEDIAL (VPM) Nucleus of the Thalamus
Trigeminal System – Symptoms Associated with Lesions
VPM
Non-conscious
Proprioception
Conscious Somatosensation
Spinocerebellar Tracts
BODY
HEAD
Trigeminal
System
PAIN
& Temp
Fine
Touch
Pain
Lateral
SpinoThalamic
Dorsal
Column
System
Spinal
Touch
Principal
(Main)
(IPSILATERAL)
Cerebellar Tracts: Non-Conscious Proprioception
Cerebellum – Master coordinator of movement, does not initiate.
Limb position, joint angles, muscle tension, muscle length.
1.
Dorsal Spinocerebellar Tract - coordination of individual muscles of the lower
trunk and lower extremity during postural adjustments and movements.
2.
Ventral Spinocerebellar Tract - general coordination of muscles of the lower
part of the body during movement (walking).
3.
Cuneocerebellar Tract - coordination of individual muscles in the upper trunk
and upper extremity. C2 – T4
The general rule is that the cerebellum receives
information from the ipsilateral side of the body
Cerebellar Tracts: Non-Conscious Proprioception
Dorsal Spinocerebellar Tract
Spinocerebellum
Anterior Lobe
Posterior Lobe
Paramedian Lobule
Flocculonodular Lobe
Cerebellar
Nuclei
Dorsal
SpinoCerebellar
Tract
Inferior Cerebellar Peduncle
Restiform Body
Kandel and Schwartz 1985, p506.
Secondary 2
T1 to L2
DRG
o
Spinal Cord:
Dorsal Nucleus of Clarke
o
Primary 1
Receptor
Key Elements for Dorsal Spinocerebellar Tract
The dorsal spinocerebellar tract carries information from the lower
part of the body and synapses within the cerebellum in such a
way to maintain the somatotopic map of the body within the
cerebellum.
Key Questions for the Dorsal Spinocerebellar Tract
Where are the Cells of Origin for the Dorsal Spinocerebellar Tract?
Ipsilateral Spinal Cord: Dorsal Nucleus of Clarke
Where does the tract terminate?
Ipsilateral Spinocerebellum
Cerebellar Tracts: Non-Conscious Proprioception
Dorsal Spinocerebellar Tract
Cuneocerebellar Tract
Anterior Lobe
Posterior Lobe
Paramedian Lobule
Flocculonodular Lobe
Cerebellar
Nuclei
Dorsal
SpinoCerebellar
Tract
CuneoCerebellar
Tract
Inferior Cerebellar Peduncle
Restiform Body
Restiform Body
DRG
Secondary 2o
Lateral Cuneate
Nucleus
Spinal Cord:
Dorsal Nucleus of Clarke
o
Primary 1
Receptor
DRG
o
Primary 1
Receptor
C2 to T4
ps
e
T1 to L2
o
sy
na
Secondary 2
Medulla
Key Elements for the Cuneocerebellar Tract
The Cuneocerebellar tract originates in the brainstem
and ascends ipsilaterally to the cerebellum, carrying
information from the upper body (C2-T4).
Cerebellar Tracts: Non-Conscious Proprioception
Ventral Spinocerebellar Tract
Recrosses in
Cerebellum
Superior
Peduncle
Ventral
Spinocerebellar
Tract
Ventral
Spinocerebellar
Tract
L3
to
S1
DRG
Spinal Cord:
Lamina V-VII + border
Primary 1o
Receptor
ps
e
Secondary 2o
sy
na
midline
Crosses in
a nterior white
commissure
Spinal border
cells
Lesions and Clinical Deficits - Wallenberg’s
Lateral Medullary (Wallenberg’s) Syndrome – Symptoms include loss of pain and
temperature on the ipsilateral head/face, contralateral loss of pain and temperature in
the body, and ataxia.
Trigeminal Tract
Trigeminal Nucleus
Dorsal
Spinocerebellar Tract
Ventral
Spinocerebellar Tract
ALS (lateral spinothalamic tract)
Lesions and Clinical Deficits – Tabes Dorsalis
Degeneration of myelinated afferent fibers in the dorsal columns, (destroys large
diameter axons), is a late stage of syphilis.
Symptoms:
Severe deficits in touch and position sense but often little loss of temperature perception and of
nociception. Bilateral lesion = bilateral effects.
LESIONS and Clinical Deficits – Brown-Sequard Syndrome
Hemisection of the spinal cord, often in the cervical spinal cord – (it is rare for the entire
hemisection to be affected, but this does occur, more often incomplete hemisection is found).
Symptoms:
a) Loss of fine discrimination touch, vibration, and position sense ipsilaterally for body regions
from affected dermatome and down
b) Loss of pain and temperature contralaterally for body regions from affected dermatome
and down (small region of bilateral loss of pain and temp at level of lesion and 2 segments
below)
c) Motor Effects: – Ipsilateral Spasticity and Weakness
DC
Arch Neurol (2001) 58: 1470.