Transcript Test yourself on lesions in section pictures

Specific Lesions
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Carpenter, Human Neuroanatomy, p271
1. Loss or reduction in pain and
temperature sensation of the legs and
lower body (below segment of injury)
on the right side.
This lesion is eliminating the anterolateral
system or lateral and anterior spinothalamic
tracts. The main effect is loss of pain and temp
due to lesion of the lateral spinothalamic tract. It
is a contralateral loss because the tract consists of
the second order fibers that have already crossed
the midline. Remember the cell bodies
contributing these axons are located in the dorsal
horn; and the axon crosses in the ventral white
commissure and then ascends in the lateral
funiculus.
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Specific Lesions
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Carpenter, Human Neuroanatomy, p271
2. Bilateral loss in pain and temperature
sensitivity of the body, specifically the
trunk (head and face not affected)
Here you have bilateral loss of pain and
temperature due to lesion of the second order
fibers as they are crossing the midline prior to
ascending as the lateral spinothalamic tract.
This lesion will affect primarily dermatomes at
the level of the lesion and 2 segments below. It
will affect those 2 segments below, because the
primary afferent in this pathway ascends
several spinal segments within Lissauer’s tract
(the cap of the dorsal horn) before synapsing on
the second order neurons crossing here.
Dermatomes more than 2 segments below the
level of the lesion will be little affected because
the fibers subserving those regions have
already crossed in segments below the lesion
and are now traveling out laterally in the
funiculus as the lateral spinothalamic tract.
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Specific Lesions
This lesion induces an ipsilateral loss because the
cell bodies of the second order neurons in the
Anterolateral System (ALS) pathway are being
eliminated. It is not contralateral because the axons
have not yet crossed. The main region affected will
be 2 dermatomes below the level of the lesion since
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the primary afferents synapsing on these second
order neurons entered the spinal cord ~2 segments
below and then ascended to this level in Lissauer’s
tract. This lesion would affect all of the right leg if
it extended in caudal spinal cord segments. If the
lesion was more focal it may only affect the upper
part of the leg, since neurons receiving input from
Carpenter, Human Neuroanatomy, p271
the lower leg would be located in the dorsal horn of
more caudal segments and the axons of those
3. Loss of pain and temperature
neurons would be unaffected by a focal lesion,
sensation in right leg and trunk (begins
since they are traveling out laterally in the lateral
two dermatomes below)
spinothalamic tract.
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Specific Lesions
Loss of pain and temperature in the
ipsilateral face is due to elimination of the
spinal trigeminal tract and nucleus. This
pathway has not yet crossed, since these
are the primary afferents and cell bodies of
the second order neurons. Loss of pain
and temperature in the contralateral body
occurs due to elimination of the lateral
spinothalamic tract. This tract crossed
back in the spinal cord, so effects are
contralateral. Loss of fine discrimination
touch in the ipsilateral arm is due to lesion
of the cuneate nucleus. These are the cell
bodies of the second order neurons, so this
information has not yet crossed the
midline and the cuneate is specifically for
fine discrimination touch from the upper
body. The ataxia would be due to lesion
of the spinocerebellar tracts which are
located in the lateral part of the section.
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4. Loss of pain and temperature
sensation on the left side of the face,
loss of pain and temperature sensation
in the right leg, arm and trunk. ALSO
– dorsal column effects – some loss of
fine discrimination touch in the left arm.
Also ataxia could be present.
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Specific Spinal Cord Lesions
5.
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Carpenter, Human Neuroanatomy, p271
5. Loss or reduction in discriminative,
positional, and vibratory tactile
sensations of the legs and lower body
(below segment of injury) on the right
side.
The lesioned area is the Gracile
Fasciculus. This contains the central
processes of the primary afferents
subserving fine discrimination
(conscious proprioception) from the legs
and lower part of the body. Because
these are the first order neurons, the
pathway has NOT yet crossed. If the
pathway hasn’t crossed, the lesion is
ipsilateral. This will affect the
dermatomes subserving segments below
the level of the lesion. This is true
because the information from these
lower dermatomes has already entered
the dorsal horn and is now traveling
within this medial location. Information
from the upper part of the body is
traveling more laterally.
Specific Spinal Cord Lesions
6.
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This is an ipsilateral effect because this
region contains the central processes of
the primary afferent neurons. The
upper body is affected because this
region is the cuneate fasciculus and
lower body information is carried more
medially in the gracile fasciculus.
6. Loss or reduction in discriminative,
positional, and vibratory tactile
sensations of the arms and upper body
(below segment of injury) on the left
side.
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Specific Brain Stem Lesions
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These lesions will result in loss of conscious proprioception (fine discrimination touch,
pressure, vibratory sense) in the right leg and lower trunk. What is lesioned = Gracile
fasciculus. This contains the central processes of the primary afferents ascending to
ultimately synapse in the nearby Gracile nucleus. The pathway has not crossed! So the
effect is ipsilateral. This region carries information from the lower part of the body. This
is the dorsal column system so it mediates conscious proprioception.
Specific Brain Stem Lesions
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Result is loss of conscious proprioception in the left leg and lower body. What is
lesioned = Gracile nucleus. These are the cell bodies of the second order neurons. The
pathway has not yet crossed so the effect is ipsilateral. It is lower body because it is
Gracile nucleus (not Cuneate which carries upper body info). It is conscious
proprioception because these are components of the dorsal column system.
Specific Brain Stem Lesions
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The result is a loss in conscious proprioception in the right arm and upper body. What is
lesioned is the cuneate nucleus. It is ipsilateral because these are the cell bodies of the
second order neurons and the pathway has not yet crossed. It is the upper body because
it is the cuneate nucleus (lower body = gracile nucleus). It is conscious proprioception
because this is part of the dorsal column system.
Specific Brain Stem Lesions
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The effect is loss of conscious proprioception on the right side of the body. What is
lesioned = internal arcuate fibers. These are the axons of the second order neurons just
BEFORE they have crossed the midline. The effect is ipsilateral because they have
not YET crossed. It will affect both upper and lower parts of the body because axons
from both gracile and cuneate nuclei are running here. Modality is conscious
proprioception (fine discrimination touch) because these are part of the dorsal column
system.
Specific Brain Stem Lesions
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Dorsal
Ventral
Result is loss of conscious proprioception (fine discrimination touch) on the right side of
the body. What is lesioned = medial lemniscus. The effect is contralateral because the
axons of this tract have crossed the midline (as the internal arcuate fibers). Both upper
and lower parts of body will be affected, because the axons of both the gracile and
cuneate nuclei contribute to this tract. The gracile neurons send their axons to the ventral
portion of the tract and the cuneate neurons send their axons to the dorsal portion of the
tract.
Practice Question 1
Which statement is true regarding the shaded area below?
A.
B.
C.
D.
E.
Pathway terminates on the left side of the spinal cord
Pathway arises from cells in the dorsal horn on the left side of the spinal cord
Pathway terminates in the left VPL
Pathway arises from cells in the dorsal root ganglion on the right
Pathway arises from cells in the right motor cortex
Level of section = pyramidal decussation. Lesioned = lateral
spinothalamic tract. Answer = C
Answer: C
A is wrong because this pathway is ascending it will
terminate above the level of this lesion, not below in the
spinal cord. B is wrong because these are the second order
fibers in the pathway, so they crossed the midline near the
level of their cell bodies – crossed back in the ventral white
commissure of the spinal cord. So the pathway actually
arises from the right spinal cord. C is correct the lateral
spinothalamic tract ascends to terminate in the ipsilateral
VPL of the thalamus. D is wrong because these fibers are
the second order neurons, not the first order neurons. This
pathway WILL receive input from the cells in the right
dorsal root ganglion. E is wrong because this is ascending
sensory information, not a descending motor tract.
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Practice Question 2
Which statement is true regarding the shaded area below?
A. Cells project to the left VPM
B. Pathway arises from cells in the right trigeminal ganglion
C. Pathway arises from cells in the dorsal horn on the left side of the spinal cord
D. Cells project to the right VPL
E. Cells project to the right VPM
Area lesioned = Spinal trigeminal Nucleus. Answer = E
Answer: E
A is wrong because this nucleus contains the cell bodies
of the second order neurons whose axons have not yet
crossed the midline, so they will project to the
contralateral hemisphere. B is wrong because the axons
arising from the trigeminal ganglion neurons are located
in the spinal trigeminal tract, just lateral to this nucleus,
but also that afferent input comes from the ipsilateral
side. C is wrong because the dorsal horn cells carry
information about the body and do not project into the
trigeminal system. D is wrong because this information
is about the face and head – all somatosensory info from
the face head goes to VPM. E is correct, these second
order neurons will project to the contralateral thalamus.
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Practice Question 3
Which statement is true regarding the shaded area below?
A. Lesion results in loss of pain and temperature from the right side of the face
B. Axons end in the left VPM
C. Axons arise from the right trigeminal ganglion
D. Axons arise from the right ganglion of IX
E. Lesion results in a loss of pain and temperature from the left side of the face
Area lesioned = Spinal Trigeminal Nucleus
Answer: E
Right
Left
Midline
A is incorrect because these are the cell bodies of the
second order neurons, so the pathway has not yet crossed,
thus sensory deficits would be ipsilateral. B is incorrect
because the axons of these neurons cross the midline in the
reticular formation to terminate in the contralateral (right)
VPM. C is incorrect because the axons terminating on
these second order neurons arise from the left trigeminal
ganglion and left geniculate ganglion and superior ganglia
of IX and X. D is incorrect for the same reason. E is
correct because these second order neurons receive
information from the ipsilateral head and face via the
trigeminal nerves and tract.
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Clinical Problems
Where is the lesion??
Q1. Loss of muscle joint sense of the left leg. Right trunk and leg
- total analgesia, thermoanesthesia
A1. Left hemisection at thoracic level
With a hemisection, the dorsal column system and the anterolateral system
will be eliminated. The dorsal column system carries muscle joint sense
(as well as tactile discrimination, vibration, and pressure sense). This
information travels ipsilateral within the dorsal funiculus of the spinal cord
(to synapse in the brainstem where the second order fibers cross the
midline). The anterolateral system carries pain and temperature senses.
Analgesia = absence of pain, thermoanesthesia = absence of temperature
sense. A lesion in the left spinal cord will affect the right side of the body
because the fibers in the lateral spinothalamic tract have already crossed
the midline. Lower body lesion, including the trunk area suggests thoracic
level since dermatomes at and below the level of the lesion will be
affected. Upper body is not affected, so it cannot be cervical cord.
Clinical Problems
What is the clinical problem and where is the lesion?
Q2. Analgesia and thermoanesthesia on the left hand, had previously burned the little finger of left
hand but was unaware until smelled the burning skin. On Exam: Reduced pain and temperature sense
involving the 8th cervical and first thoracic dermatomes of the left hand, but tactile discrimination
normal. Right arm similar but much less severe.
A2. Early signs of syringomyelia. Gliosis and cavitation interrupts ALS at the level of the 8 th cervical
and 1st thoracic segments of cord. Uneven growth of cavitation – causes one side to be worse – not
that large since does not involve fasciculus cuneatus.
Syringomyelia is expansion of the CSF into the spinal cord (starting from the central
canal). This causes a midline lesion and interruption of the fibers crossing from both
sides to ascend as the lateral spinothalamic tract. This tract carries pain and temperature
information.
Clinical Problems
Q3. 60 yr old man – raises his feet unnecessarily high and brings them to the ground in a stamping
manner, stands with feet wide apart. Finding it difficult to walk, especially in dark. Asked to stand
with toes and heels together and then close eyes – patient begins to sway. Loss of muscle joint sense,
vibration sense of both legs.
A3. Lesion involving fasciculus gracilus in both posterior white columns – learn that patient has
previously had syphilis. Diagnosis = Tabes Dorsalis.
Both legs are affected, so the lesion is bilateral. It is the lower part of the body,
therefore gracilus. As part of the dorsal column system, this region conveys
conscious proprioception, which includes a sense of the location of your body in
space (muscle joint sense, as well as vibration, pressure, and fine tactile
discrimination).