Transcript Spinal Cord 14th sept

Spinal Cord
 Runs through the vertebral canal
 Extends from foramen magnum to
second lumbar vertebra
 Regions
 Cervical
 Thoracic
 Lumbar
 Sacral
 Coccygeal
 Gives rise to 31 pairs of spinal nerves
 All are mixed nerves
 Spinal cord Enlargements
 Cervical enlargement: supplies
upper limbs
 Lumbo -sacral enlargement:
supplies lower limbs
 Conus medullaris- tapered inferior
end
 Ends between L1 and L2
Spinal Segments & Roots
Spinal segment
C8, T12, L5, S5, Cx1
Anterior (Ventral) Root
Posterior (Dorsal) Root
Dorsal Root (Spinal) Ganglion
Root - Rootlets
Spinal Segments
 Importance of the
spinal segments
Spinal Cord
 White Matter
Anterior Funiculus (Anterior White Column)
Posterior Funiculus (Posterior White Column)
Lateral Funiculus (Lateral White Column)

Gray Matter
Anterior Horn ------------
motor
Posterior Horn -------------- sensory
Lateral Horn -----------------autonomic (sympathetic)
Gray Commissure -------- anterior and posterior
Cord Organization
 Principles of Cord Organization
1) Longitudinal Arrangement
Fibers (White Matter) ------------ White Column
Cell Groups (Gray Matter) ------- Gray Column
2) Transverse Arrangement
Afferent & Efferent Fibers
Crossing (Commissural and Decussating) Fibers
3) Somatotopical Arrangement
Clinical Case
 A 55 year old woman complained of pain in her right breast
and progressive weakness of her right lower limb for a period
of two months, she contacted her Family physician, Her
Family physician referred her to a neurologist.
 The neurologic evaluation revealed weakness in the right
lower limb. This was associated with spasticity (increased
tone), hyperreflexia (increased deep tendon reflexes) at the
knee and ankle, which also demonstrated clonus.
 On the right side there was loss of two-point discrimination,
touch ,vibratory sense and proprioception at levels below the
hip. The left side showed a loss of pain and temperature
sensation below dermatome T-7.
Clinical Case cont..
 MRI of a patient indicated to have an extramedullary
tumor expanding from the dorsal roots at spinal cord
levels T-5,6.
 Based on the symptoms and clinical findings what is your
diagnosis ?
 loss of two-point discrimination, touch ,vibratory sense and
proprioception at levels below the hip due to lesion in
which pathway in the spinal cord?
The somatosensory system
 The somatosensory system includes multiple types
of sensation from the body.
 There are several general modalities of sensations.






Touch,
Pressure,
Vibration ,
Proprioception, (Conscious and Unconscious)
Stereognosis,
pain and temperature.
 These modalities of sensations are grouped into three
different pathways in the spinal cord and have different
targets in the brain
The somatosensory
system…
 The first modality is called discriminative touch,
which includes touch, pressure, and vibration
perception.
 The second modality is called proprioception,

This modality primarily targets the cerebellum, which needs
minute-by-minute feedback on what the muscles are doing.
 The third grouping is pain and temperature, which
also includes the sensations of itch and tickle.
Somatosensory Pathway(Dorsal Column)
Somatosensory Pathway
Posterior column pathway
carries sensation of highly
localized touch, pressure,
vibration.
Posterior column pathway
includes:
 Fasciculus cuneatus tract
 Fasciculus gracilus tract Carries fine touch, pressure,
vibration, stereognosis and
conscious Proprioceptive
sensations.
Posterior column pathway
 Large, myelinated sensory nerve fibers that conduct
these modalities are located in the medial aspect of
the dorsal root as it enters the spinal cord.
 Some of these sensory fibers terminate directly at the
level of the spinal cord where they participate in
reflex responses to touch and also are involved in
inhibiting pain transmission through the substantia
gelatinosa. However, the great majority of these
large-diameter sensory fibers enter the dorsal
column of the spinal cord.
Posterior column pathway
 The first order sensory fibers in the dorsal column tracts
ascend to the level of the medulla. Here they synapse in
the dorsal column nuclei, which include the nucleus
gracilis and nucleus cuneatus located within the dorsal
aspect of the caudal medulla.
 Projection neurons of the nucleui gracilis and cuneatus,
that is, the second order neurons, give rise to axons that
arch ventrally within the medulla (internal arcuate
fibers). These axons decussate and reach the medial
lemniscus.
 The medial lemniscus is a tract consisting of axons that
connect the dorsal column nuclei with the ventral
posterolateral nucleus of the thalamus.
 The medial lemniscus terminates in the VPL of the
thalamus. The third order neuron in the VPL relays
to the primary somatosensory cortex (postcentral
gurus; cortical areas 3, 1, 2).
 The portions of the parietal lobe immediately
posterior to the postcentral gyrus are responsible for
synthesizing cortical information into a recognizable
pattern.
 Damage to this somatosensory "association cortex"
produces an inability to interpret a sensory signal,
even though it can be detected (somatosensory
agnosia).
Dorsal Column tracts
dorsal
cloumn
pathway
Dorsal Column Lesion
dorsal column
pathway
Left
spinal cord injury
Loss of sense of:
•touch
•proprioception
•vibration in left leg
Dorsal Column Lesions
 Sensory ataxia
 Patient staggers; cannot
perceive position or
movement of legs.
 Visual clues help
movements
 Rombergism..
Assessment of Dorsal
Column
Case ….
An 85-year-old man is being evaluated for gait
difficulties. On examination it is found that joint
proprioception is absent in his toes. People with
impaired position sense will usually fall if they stand
with their feet together and do which of the
following?
 Flex the neck
 Extend their arms in front of them
 Flex the knees
 Turn the head
 Close their eyes
Anterolateral system
The Anterolateral Pathway
 Provides sensations of
“crude” touch, pressure,
pain, and temperature
 Ascend within the anterior
or lateral spinothalamic
tracts:
What is Pain?
 “An unpleasant sensory & emotional experience associated with
actual or potential tissue damage, or described in terms of such
damage” –
 Subjective sensation
 Pain Perceptions – based on expectations, past experience, anxiety,




suggestions
 Affective – one’s emotional factors that can affect pain
experience
 Behavioral – how one expresses or controls pain
 Cognitive – one’s beliefs (attitudes) about pain
Physiological response produced by activation of specific types of
nerve fibers
Experienced because of nociceptors being sensitive to extreme
mechanical, thermal, & chemical energy.
Composed of a variety of discomforts
One of the body’s defense mechanism (warns the brain that tissues
may be in jeopardy)
Where Does Pain Come
From?
 Cutaneous Pain – sharp, bright, burning; can
have a fast or slow onset
 Deep Somatic Pain – stems from tendons,
muscles, joints, periosteum, & b. vessels
 Visceral Pain – originates from internal
organs; diffused @ 1st & later may be localized
(i.e. appendicitis)
 Psychogenic Pain – individual feels pain but
cause is emotional rather than physical
Anterolateral System (Pain &Temp)
spinothalamic pathway
Left
spinal cord injury
Loss of sense of:
•Touch
•Pain
•Warmth/cold
in right leg
Spinothalamic Tracts
 Located lateral and ventral to




the ventral horn
Carry impulses concerned
with pain and thermal
sensations (lateral tract) and
also non- discriminative touch
and pressure (medial tract)
Fibers of the two tracts are
intermingled to some extent
In brain stem, constitute the
spinal lemniscus
Fibers are highly somatotopically arranged, with those
for the lower limb lying most
superficially and those for the
upper limb lying deeply
Lateral Spinothalamic Tract
 Carries impulses concerned
with pain and thermal
sensations.
 Axons of 1st order neurons
terminate in the dorsal horn
 Axons of 2nd order neuron
(mostly in the nucleus
proprius), decussate within one
segment of their origin, by
passing through the ventral
white commissure & terminate
on 3rd order neurons in ventral
posterior nucleus of the
thalamus
 Thalamic neurons project to
the somatosensory cortex
Anterior Spinothalamic Tract
 Carries impulses concerned
with non- discriminative touch
and pressure
 Axons of 1st order neurons
enter cord terminate in the
dorsal horn
 Axons of 2nd order neuron
(mostly in the nucleus proprius)
may ascend several segments
before crossing to opposite
side by passing through the
ventral white commissure &
terminate on 3rd order neurons
in ventral posterior nucleus of
the thalamus
 Thalamic neurons project to the
somatosensory cortex
Spino-reticulo-thalamic System
 The system represents an additional route by which
dull, aching pain is transmitted to a conscious level
 Some 2nd order neurons terminate in the reticular
formation of the brain stem, mainly within the
medulla
 Reticulothalamic fibers ascend to intralaminar nuclei
of thalamus, which in turn activate the cerebral
cortex
Pain Control Theories
 Gate Control Theory
 Endogenous Opiates Theory
 Phantom Pain
 Refferd Pain
Gate Control Theory
 Melzack & Wall, 1965
 Substantia Gelatinosa (SG) in dorsal horn of
spinal cord acts as a ‘gate’
 SG cells of Lamina II act as a inhibitory neurons
and inhibit “T” cells of lamina IV
 Larger diameter afferent fibers of touch excite
both SG and T cells, Therefore afferent signals of
pain sensation from T cells is blocked by
stimulation of inhibitory SG cells.
 Small diameter afferent fibers excite T cells and
Inhibit SG cells Therefore Gate is kept
Descending Pain Inhibition
 Descending Pain Modulation (Descending Pain Control
Mechanism)
 Periaqueductal Gray Area (PGA) – release enkephalins
 Nucleus Raphe Magnus (NRM) – release serotonin
 The release of these neurotransmitters inhibit ascending
neurons
 Stimulation of the PGA in the midbrain & NRM in the
pons & medulla causes analgesia.
 Endogenous opioid peptides - endorphins &
enkephalins
Referred Pain?
 Dermatomal rule
 Convergence
 Facilitation
Grey Matter Of Spinal cord
White Matter
Anterior Funiculus (Anterior White Column)
Posterior Funiculus (Posterior White Column)
Lateral Funiculus (Lateral White Column)
Gray Matter
Anterior Horn -----------motor
Posterior Horn -------------- sensory
Lateral Horn ----------------- autonomic
(sympathetic)
Gray Commissure -------- anterior and posterior
Principles of Cord Organization
1) Longitudinal Arrangement
Fibers (White Matter) ------------- White Column
Cell Groups (Gray Matter) ------- Gray Column
2) Transverse Arrangement
Afferent & Efferent Fibers
Crossing (Commissural and Decussating) Fibers
3) Somatotopical Arrangement
Principles of Cord Organization
Lamina of Rexed
Lamina I ---------- posteromarginal nucleus
Lamina II ---------- substantia gelatinosa of Rolando
Lamina III, IV ----- nucleus proprius
Lamina V, VI
Lamina VII --------- intermediate gray
intermediolateral cell column (ILM)
Clarke’s column (Nucleus dorsalis)
intermediomedial cell column (IMM)
Lamina VIII
Lamina IX ---------- anterior horn (motor) cell
Lamina X ----------- gray commissure
Alpha Motor Neurons
 Motor Unit
 Motor End Plate
 Phasic
 Tonic
Muscle Spindle
Motor Pathways
 CNS issues motor commands in response to information
provided by sensory systems, sent by the somatic nervous
system (SNS) and the autonomic nervous system (ANS)
 Conscious and subconscious motor commands control
skeletal muscles by traveling over 3 integrated motor
pathways
 The corticospinal pathway – voluntary control of motor activity
 Corticobulbar tracts
 Corticospinal tracts
 The medial and lateral pathways – modify or direct skeletal
muscle contractions by stimulating, facilitating, or inhibiting
lower motor neurons
Motor Pathways
• Contain a sequence of TWO
neurons from the cerebral
cortex or brain stem to the
muscles
• Upper motor neuron : has cell
body in the cerebral cortex or
brain stem, axon decussates
before terminating on the
lower motor neuron
• Lower motor neuron: has cell
body in the ventral horn of the
spinal cord, axon runs in the
ipsilateral ventral root of the
spinal nerve and supply the
muscle.
UMN
LMN
Descending Spinal Tracts

Originate from the cerebral cortex & brain
stem
 Concerned with:
 Control of movements
 Muscle tone
 Spinal reflexes & equilibrium
 Modulation of sensory transmission to
higher centers
 Spinal autonomic functions
 The motor pathways are
divided into two groups
 Direct pathways
(voluntary motion
pathways) - the
pyramidal tracts
 Indirect pathways
(postural pathways),
essentially all others the extrapyramidal
pathways
Direct (Pyramidal) System
 Regulates fast and fine (skilled) movements
 Originate in the pyramidal neurons in the
precentral gyri,
 Impulses are sent through the corticospinal
tracts and synapse in the anterior horn
 Stimulation of anterior horn neurons activates
skeletal muscles
 Part of the direct pathway, called corticobulbar
tracts, innervates cranial nerve nuclei
Indirect (Extrapyramidal) System
 Complex and multisynaptic pathways
 The system includes:
• Rubrospinal tracts: control flexor muscles
• Vestibulospinal tracts: maintain balance and
posture
• Tectospinal tracts: mediate head neck, and eye
movement
• Reticulospinal tracts
Descending Spinal Tracts
 Pyramidal
 Corticospinal
 Extrapyramidal
 Rubrospinal
 Tectospinal
 Vestibulospinal
 Olivospinal
 Reticulospinal
 Descending
Autonomic Fibers
Corticospinal Tracts
 Concerned with voluntary,
discrete, skilled
movements, especially
those of distal parts of the
limbs (fractionated
movements)
 Innervate the contralateral
side of the spinal cord
 Provide rapid direct
method for controlling
skeletal muscle
 Origin: motor and sensory
cortices
 Axons pass through corona
radiata, internal capsule, crus
cerebri and pyramid of
medulla oblongata
 In the caudal medulla about
75-90% of the fibers
decussate and form the
lateral corticospinal tract
 Rest of the fibers remain
ipsilateral and form anterior
corticospinal tract. They
also decussate before
termination
 Distribution:
 55% terminate at
cervical region
 20% at thoracic
 25% at lumbosacral
level
 Termination: Ventral horn
neurons (mostly through
interneurons, a few fibers
terminate directly)
 Corticobulbar tracts end
at the motor nuclei of CNs
of the contralateral side
Rubrospinal Tract
 Controls the tone of limb
flexor muscles, being
excitatory to motor neurons
of these muscles
 Origin: Red nucleus
 Axons course ventromedially, cross in ventral
tegmental decussation,
descend in spinal cord
ventral to the lateral
corticospinal tract
 Cortico-rubro-spinal pathway
(Extrapyramidal)
Tectospinal Tract
 Mediates reflex movements of
the head and neck in response
to visual stimuli
 Origin: Superior colliculus
 Axons course ventro-medially
around the periaqueductal gray
matter, cross in dorsal
tegmental decussation,
descend in spinal cord near the
ventral median fissure,
terminate mainly in cervical
segments
 Cortico-tecto-spinal pathway
(Extrapyramidal)
Vestibulospinal Tracts
 Lateral Vestibulospinal
Tracts

Origin: lateral vestibular
(Deiter’s) nucleus
 Axons descend ipsilaterally in
the ventral funiculus
 Terminate on ventral horn
cells throughout the length of
spinal cord
 Has excitatory influences
upon extensor motor neurons,
control extensor muscle tone
in the antigravity maintenance
of posture
Case ..
 Following an automobile accident, an eighteen year
old male was hospitalized for several weeks. A
neurological exam at that time revealed the
following:
1. Complete loss of conscious proprioception in the
right lower limb.
2. Babinski sign on the right.
3. Inability to detect pain and temperature sensation
on the medial side of the antecubital fossa
(medialepicondyle) on both upper limbs.
4. Inability to detect pain and temperature at the apex
of the left axilla, in all the intercostal spaces on the
left, and in the left lower limb.
5. The patient could feel a gentle squeezing of both
thumbs, right and left middle fingers, and the left
little finger.
6. No sensation to squeezing could be detected in the
right little finger.
 Ipsilateral paralysis below the lesion. Paralysis is
the "Upper Motor Neuron" or spastic type; there is
spasticity, slow (disuse) muscle atrophy, hypertonia,
ankle clonus and a positive Babinski sign. Superficial
reflexes, e.g., the abdominal and cremasteric are lost.
 Spastic paralysis is attributed to interruption of the
lateral corticospinal tract and the accompanying lateral
reticulospinal tract. Loss of these upper motor neurons
deprives the anterior horn cells, i.e., lower motor
neurons, of the impulses which generate contraction of
skeletal muscle, hence, weakness (paresis) or paralysis.
 Hypertonia and hyperreflexia appear to result from loss
of the inhibitory effects of these two descending motor
pathways on the stretch reflexes, leaving them
hyperexcitable to segmental muscle afferents
 It may be possible to also demonstrate a "Lower
Motor Neuron Syndrome" or flaccid paralysis
ipsilaterally at the level of the lesion. If the anterior
horn cells supplying the skeletal muscles are injured
at the level of the lesion then these muscles are
denervated. This paralysis is of the flaccid type;
muscles undergo rapid atrophy due to loss of the
trophic influence of the nerves as well as disuse.
 Tone and tendon reflexes are diminished since they
are reflex responses and the injured lower motor
neurons are the "final common pathway" to the
muscle in the stretch reflex, hence, there is no
reflex.
 Loss of conscious proprioception, two-point
discrimination and vibratory sense ipsilaterally is due to
interruption of the posterior white columns (fasciculus
gracilis/cuneatus). This is frequently accompanied by a Romberg
sign. A normal individual, standing erect with heels together and
eyes closed, sways only slightly. Stable posture is achieve by
 1) a sense of position from the vestibular system,
 2) awareness of the position and status of muscles and joints by
conscious proprioception and 3) visual input regarding our position.
Closing the eyes has only slight effect on the normal individual's
stance since the vestibular and conscious proprioception systems
are sufficient. In a patient with an impaired posterior column
conscious proprioception is diminished; when the eyes are closed
loss of both systems renders the patient unstable and they are likely
to sway or fall to the side.
 Pain and temperature sensation is lost below the
lesion, on the opposite side beginning about one
dermatomal segment below the level of the lesion. These
sensations are carried by the lateral spinothalamic tract
whose fibers originated on the side opposite the lesion
but which crossed in the anterior white commissure.
 Dorsal root afferents carrying pain and temperature
synapse in the dorsal gray; the second order neuron
crosses in the anterior white commissure along an
ascending path for a distance of about one spinal
segment. Because of the oblique ascent of the crossing
fibers in the anterior white commissure, injury of the
spinothalamic tract is not likely to be carrying sensation
from that level.
 A careful sensory evaluation may reveal that at the
dermatomal level of the lesion there is a bilateral
loss of pain and temperature sensation. Since the
second order neurons from both sides cross in the
midline below the central canal, a hemisection of
the cord may interrupt the crossing fibers from both
sides and produce this limited bilateral deficit.
Hemisection of Spinalcord
At the level of
lesion
side
Sensory
disturbance
Motor
disturbance
Reflexes
On the same side
Below
On the Opposite
side
Loss of all sensation
Loss of the dorsal
Loss of
1-superfecial sensations column due to
1-pain & temp.
2-deep sensations
damage of gracil &
due to damage of
cunite leading to loss lateral
of
spinothalamic tract.
1. fine touch
2-crude touch due
2. kinesthetic
to damage of
3. vibration
ventral
4. sterognosis
spinothalamic tract.
1-LMNL
UMNL due to
2-paralysis of muscles damage of pyramidal
which its supply arising tract
from damage
Loss of all reflexes
which its centers in
damage segments
On the same side
1-loss of flexor
withdrawal reflex
2-increase crossed
extensor reflex
Above
On the same side
Hyperanasthesia
(Hypersensitivity)
increase sensitivity to
1. pain
2. touch
3. Temp.
Case 2….
• A 55 year old man noticed a weakness of his left hand
and loss of pain in his both arms which was progressing
and causing him mental apathy and he felt he should
visit neurologist .
• On examination he demonstrated bilateral weakness,
atrophy, and fasciculations of the intrinsic muscles of his
hands and shoulders. Upper motor neuron syndrome
signs, i.e., weakness, hypertonia, hyperreflexia, positive
Babinski, were evident in both lower extremities.
Dermatomes C-2 through T-6 demonstrated bilateral
loss of pain and temperature sensation. There was
bilateral impairment of position and vibratory sense
below the hips.
Case 2 cont..
 MRI investigation showed a central cavitation at C-2
through T-7 which expanded symmetrically in all
directions.
 It involved the anterior white commissure
(spinothalamic fibers) and included portions of the
posterior white columns, lateral white funiculus, and
anterior gray horns.
Syringomyelia
Syringomyelia
 the result of central cord cavitation affecting a few segments,
and usually involving the cervical spinal cord
 frequently found in Arnold-Chiari malformations affecting the upper
cervical cord and medulla
 mainly affects the crossing fibres of the spinothalamic tract as they
decussate in the ventral white commissure => bilateral paintemperature sensory loss over a few segments eg. only
affecting the neck and upper shoulders in a cape-like distribution (or
only affecting the upper limbs) with normal sensation above and
below the affected dermatomes
 does not affect the spinothalamic tracts in the early stages => no
initial lower trunk or lower limb pain-temperature sensory loss
 does not usually affect the dorsal columns => normal position sense
("dissociative" sensory loss)
 may rarely affect the lower motor neurons to the upper limbs early in
the disease course, and may eventually affect the corticospinal tracts
 A 66-year-old man found that, over a period of time, he
developed progressive bilateral weakness of both upper
and lower limbs beginning with the muscles of the hands.
However, testing revealed that sensory functions appeared
normal. Eventually, this individual was found to have
wasting of muscles, fasciculations, and evidence of upper
motor neuron (UMN) dysfunction, together with an
increase in tendon reflexes. After a few additional
Months, the patient developed facial weakness and an
inability to swallow (dysphagia). Further analysis revealed
abnormalities in the electromyegram (EMG) of the upper
and lower extremities, denervation atrophy. However, the
cerebrospinal fluid (CSF) remained normal.
Which of the following is the most likely
diagnosis?
 MS
 Amyotrophic lateral sclerosis (ALS)
 Poliomyelitis
 Myasthenia gravis
 A cerebral cortical stroke
Coverings of Spinal cord
 Dura mater: outermost layer;
continuous with epineurium of the
spinal nerves
 Arachnoid mater: thin and web
like
 Pia mater: bound tightly to
surface

Ligamentum Denticulatum
Cordotomy

Forms the filum terminale


anchors spinal cord to coccyx
 Spaces
 Epidural: external to the dura
 Anesthestics injected here
 Epidural Anesthesia
 Subdural space: serous fluid
 Subarachnoid: between pia and
arachnoid

Filled with CSF
Coverings of Spinal cord cont…
Lumbar Puncture
Lumbar Puncture – lumbar (terminal) cistern