Download Spinal Cord

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
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
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
Somatosensory Pathway(Dorsal Colum)
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,
sterognosis and conscious
Proprioceptive sensations.
Dorsal Colum tracts
dorsal
cloumn
pathway
Dorsal Colum Lesion
Left
spinal cord injury
dorsal column
pathway
Loss of sense of:
•touch
•proprioception
•vibration
in left leg
Dorsal Colum Lesions
 Sensory ataxia
 Patient staggers; cannot
perceive position or
movement of legs
 Visual clues help
movement
 Rhombergism
Assessment of Dorsal Colum
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
Clinical Case
 A 45 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 Of Spinal Cord 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 ?
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
Spinocerebellar Tracts
 The spinocerebellar system




consists of a sequence of
only two neurons
Two tracts: Posterior &
Anterior
Located near the dorsolateral
and ventrolateral surfaces of
the cord
Contain axons of the second
order neurons
Carry information derived
from muscle spindles, Golgi
tendon organs and tectile
receptors to the cerebellum
for the control of posture and
coordination of movements
Posterior Spinocerebellar Tracts
 Present only above level
L3
 The cell bodies of 2nd
order neuron lie in Clark’s
column
 Axons of 2nd order neuron
terminate ipsilaterally
(uncrossed) in the
cerebellar cortex by
entering through the
inferior cerebellar
peduncle
Ventral Spinocerebellar Tracts
 The cell bodies of 2nd order neuron
lie in base of the dorsal horn of the
lumbosacral segments
 Axons of 2nd order neuron cross to
opposite side, ascend as far as the
midbrain, and then make a sharp
turn caudally and enter the
superior cerebellar peduncle
 The fibers cross the midline for a
second time within the cerebellum
before terminating in the cerebellar
cortex
 Both spinocerebellar tracts convey
sensory information to the same
side of the cerebellum
Spinotectal Tract
 Ascends in the anterolateral
part in close association with
spinothalamic system
 Primary afferents reach dorsal
horn through dorsal roots and
terminate on 2nd order neurons
 The cell bodies of 2nd order
neuron lie in base of the dorsal
horn
 Axons of 2nd order neuron
cross to opposite side, and
project to the periaquiductal
gray matter and superior
colliculus in the midbrain
Spino - olivary Tract
 Indirect spinocerebellar pathway (spino-olivo-
cerebellar)
 Impulses from the spinal cord are relayed to the
cerebellum via inferior olivary nucleus
 Conveys sensory information to the cerebellum
 Fibers arise at all level of the spinal cord
Spinoreticular Tract
 Originates in laminae IVVIII
 Contains uncrossed
fibers that end in
medullary reticular
formation & crossed &
uncrossed fibers that
terminate in pontine
reticular formation
 Form part of the
ascending reticular
activating system
Spino-Olivary Tracts
 Project to accessory olivary nuclei and cerebellum.
 Contribute to movement coordination associated
primarily with balance.
Spinotectal Tracts
 Project to superior colliculi of midbrain.
 Involved in reflexive turning of the head and eyes
toward a point of cutaneous stimulation.
Spinoreticular Tracts
 Involved in arousing consciousness in the reticular
activating system through cutaneous stimulation.
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