Spinal cord Anatomy by Dr. Naseer (RMC)

Anatomy of the Spinal CordAnatomy of the Spinal Cord
 Structure of the spinal cordStructure of the spinal cord
 Tracts of the spinal cordTracts of the spinal cord
 Spinal cord syndromesSpinal cord syndromes
ByBy
Dr. NaseerDr. Naseer

- Comparable to- Comparable to
Input-Output (IO) System of the ComputerInput-Output (IO) System of the Computer
- Spinal Nerves (C8, T12, L5, S5, Cx1)- Spinal Nerves (C8, T12, L5, S5, Cx1)
- Segmental Structure of Neural Tube Origin- Segmental Structure of Neural Tube Origin
Spinal CordSpinal CordSpinal CordSpinal Cord

Spinal segmentsSpinal segments
C8, T12, L5, S5, Cx1C8, T12, L5, S5, Cx1
Anterior (Ventral) RootAnterior (Ventral) Root
Posterior (Dorsal) RootPosterior (Dorsal) Root
Dorsal Root (Spinal) GanglionDorsal Root (Spinal) Ganglion
Root - RootletsRoot - Rootlets

Conus MedullarisConus Medullaris (L1-2)(L1-2)
Spinomedullary JunctionSpinomedullary Junction
- Foramen Magnum, Pyramidal decussation, C1 ventral root
EnlargementsEnlargements
- cervical (C5-T1) & lumbosacral (L1-L4)
Longitudinal FissuresLongitudinal Fissures
- anterior median fissure
- anterolateral fissure
- posterior median sulcus
- posterolateral sulcus
Spinomedullary JunctionSpinomedullary Junction
- Foramen Magnum, Pyramidal decussation, C1 ventral root
EnlargementsEnlargements
- cervical (C5-T1) & lumbosacral (L1-L4)
Longitudinal FissuresLongitudinal Fissures
- anterior median fissure
- anterolateral fissure
- posterior median sulcus
- posterolateral sulcus
Spinal CordSpinal Cord External FeaturesExternal FeaturesSpinal CordSpinal Cord External FeaturesExternal Features

Cauda EquinaCauda Equina
Anterior median fissureAnterior median fissure
Anterolateral fissureAnterolateral fissure

PosteriorPosterior
median sulcusmedian sulcus
PosterolateralPosterolateral
sulcussulcus
PosteriorPosterior
intermediateintermediate
sulcussulcus
FasciculusFasciculus
cuneatuscuneatus
FasciculusFasciculus
gracilisgracilis
Posterior surface of the spinal cordPosterior surface of the spinal cord

Periosteum of VertebraPeriosteum of Vertebra
-- Epidural SpaceEpidural Space ---------------------------------- epidural anesthesiaepidural anesthesia
Dura Mater SpinalisDura Mater Spinalis
Arachnoid MaterArachnoid Mater
-- Subarachnoid Space --------Subarachnoid Space -------- Lumbar PunctureLumbar Puncture
Spinal AnesthesiaSpinal Anesthesia
Pia Mater SpinalisPia Mater Spinalis
- Denticulate Ligament- Denticulate Ligament ------------------ CordotomyCordotomy
- Filum Terminale- Filum Terminale
Periosteum of VertebraPeriosteum of Vertebra
-- Epidural SpaceEpidural Space ---------------------------------- epidural anesthesiaepidural anesthesia
Dura Mater SpinalisDura Mater Spinalis
Arachnoid MaterArachnoid Mater
-- Subarachnoid Space --------Subarachnoid Space -------- Lumbar PunctureLumbar Puncture
Spinal AnesthesiaSpinal Anesthesia
Pia Mater SpinalisPia Mater Spinalis
- Denticulate Ligament- Denticulate Ligament ------------------ CordotomyCordotomy
- Filum Terminale- Filum Terminale
Spinal Cord MeningesSpinal Cord MeningesSpinal Cord MeningesSpinal Cord Meninges

Meninges ofMeninges of
the spinal cordthe spinal cord
• Dura materDura mater
• Arachnoid materArachnoid mater
• Pia materPia mater
Denticulate ligamentDenticulate ligament
- specialization of the pia mater- specialization of the pia mater
-- landmark for cordotomylandmark for cordotomy

Meninges of the spinal cordMeninges of the spinal cord

Lumbar Puncture – lumbar (terminal) cisternLumbar Puncture – lumbar (terminal) cistern

Arterial SupplyArterial Supply
- Spinal Arteries- Spinal Arteries
Anterior (1) & Posterior (2) Spinal ArteryAnterior (1) & Posterior (2) Spinal Artery
fromfrom Vertebral arteryVertebral artery
- Radicular Arteries ----- Segmental arteries- Radicular Arteries ----- Segmental arteries
fromfrom Vertebral, Ascending Cervical, Intercostal andVertebral, Ascending Cervical, Intercostal and
Lumbar ArteryLumbar Artery
Venous DrainageVenous Drainage
-- Longitudinal & Radicular VeinsLongitudinal & Radicular Veins
toto Intervertebral veinsIntervertebral veins ---- to---- to Internal Vertebral Venous PlexusInternal Vertebral Venous Plexus
toto external vertebral venous plexusexternal vertebral venous plexus ---- to---- to segmental veinssegmental veins
Arterial SupplyArterial Supply
- Spinal Arteries- Spinal Arteries
Anterior (1) & Posterior (2) Spinal ArteryAnterior (1) & Posterior (2) Spinal Artery
fromfrom Vertebral arteryVertebral artery
- Radicular Arteries ----- Segmental arteries- Radicular Arteries ----- Segmental arteries
fromfrom Vertebral, Ascending Cervical, Intercostal andVertebral, Ascending Cervical, Intercostal and
Lumbar ArteryLumbar Artery
Venous DrainageVenous Drainage
-- Longitudinal & Radicular VeinsLongitudinal & Radicular Veins
toto Intervertebral veinsIntervertebral veins ---- to---- to Internal Vertebral Venous PlexusInternal Vertebral Venous Plexus
toto external vertebral venous plexusexternal vertebral venous plexus ---- to---- to segmental veinssegmental veins
Spinal CordSpinal Cord Vascular SupplyVascular SupplySpinal CordSpinal Cord Vascular SupplyVascular Supply

anterior spinal arteryanterior spinal artery segmental arteriessegmental arteries
5. Adamkiwicz artery5. Adamkiwicz artery

White MatterWhite Matter
Anterior Funiculus (Anterior White Column)Anterior Funiculus (Anterior White Column)
Posterior Funiculus (Posterior White Column)Posterior Funiculus (Posterior White Column)
Fasciculus Gracilis & Fasciculus CuneatusFasciculus Gracilis & Fasciculus Cuneatus
Lateral Funiculus (Lateral White Column)Lateral Funiculus (Lateral White Column)
Gray MatterGray Matter
Anterior Horn ------------Anterior Horn ------------------ motormotor
Posterior Horn --------------Posterior Horn -------------- sensorysensory
Lateral Horn -----------------Lateral Horn ----------------- autonomic (sympathetic)autonomic (sympathetic)
Gray Commissure --------Gray Commissure -------- anterior and posterioranterior and posterior
White MatterWhite Matter
Anterior Funiculus (Anterior White Column)Anterior Funiculus (Anterior White Column)
Posterior Funiculus (Posterior White Column)Posterior Funiculus (Posterior White Column)
Fasciculus Gracilis & Fasciculus CuneatusFasciculus Gracilis & Fasciculus Cuneatus
Lateral Funiculus (Lateral White Column)Lateral Funiculus (Lateral White Column)
Gray MatterGray Matter
Anterior Horn ------------Anterior Horn ------------------ motormotor
Posterior Horn --------------Posterior Horn -------------- sensorysensory
Lateral Horn -----------------Lateral Horn ----------------- autonomic (sympathetic)autonomic (sympathetic)
Gray Commissure --------Gray Commissure -------- anterior and posterioranterior and posterior
Spinal CordSpinal Cord Internal StructureInternal StructureSpinal CordSpinal Cord Internal StructureInternal Structure

1. posterior horn1. posterior horn
2. anterior horn2. anterior horn
3. intermediate zone3. intermediate zone
(intermediate gray)(intermediate gray)
4. lateral horn4. lateral horn
5. posterior funiculus5. posterior funiculus
6. anterior funiculus6. anterior funiculus
7. lateral funiculus7. lateral funiculus
8. Lissauer's tract8. Lissauer's tract
9. anterior median9. anterior median
fissurefissure
10. posterior median10. posterior median
sulcussulcus
11. anterolateral11. anterolateral
sulcussulcus
12. posterolateral12. posterolateral
sulcussulcus
13. Posterior13. Posterior
intermediateintermediate
sulcussulcus

cervical enlargement (C8)cervical enlargement (C8) thoracic cord (T8)thoracic cord (T8)
lumbal enlargement (L3)lumbal enlargement (L3) sacral cord (S1)sacral cord (S1)

Principles of Cord OrganizationPrinciples of Cord Organization
1) Longitudinal Arrangement1) Longitudinal Arrangement
Fibers (White Matter) ------------- White ColumnFibers (White Matter) ------------- White Column
Cell Groups (Gray Matter) ------- Gray HornCell Groups (Gray Matter) ------- Gray Horn
2) Transverse Arrangement2) Transverse Arrangement
Afferent & Efferent FibersAfferent & Efferent Fibers
Crossing (Commissural and Decussating) FibersCrossing (Commissural and Decussating) Fibers
3) Somatotopical Arrangement3) Somatotopical Arrangement
Principles of Cord OrganizationPrinciples of Cord Organization
1) Longitudinal Arrangement1) Longitudinal Arrangement
Fibers (White Matter) ------------- White ColumnFibers (White Matter) ------------- White Column
Cell Groups (Gray Matter) ------- Gray HornCell Groups (Gray Matter) ------- Gray Horn
2) Transverse Arrangement2) Transverse Arrangement
Afferent & Efferent FibersAfferent & Efferent Fibers
Crossing (Commissural and Decussating) FibersCrossing (Commissural and Decussating) Fibers
3) Somatotopical Arrangement3) Somatotopical Arrangement

Columnnar arrangement somatotopical arrangementColumnnar arrangement somatotopical arrangement

Lamina of RexedLamina of Rexed
Lamina I ---------- posteromarginal nucleusLamina I ---------- posteromarginal nucleus
Lamina II ----------Lamina II ---------- substantia gelatinosa of Rolandosubstantia gelatinosa of Rolando
Lamina III, IV ----- nucleus propriusLamina III, IV ----- nucleus proprius
Lamina V, VILamina V, VI
Lamina VII --------- intermediate grayLamina VII --------- intermediate gray
intermediolateral cell column (IML)intermediolateral cell column (IML)
Clarke’s column (Nucleus dorsalis)Clarke’s column (Nucleus dorsalis)
intermediomedial cell column (IMM)intermediomedial cell column (IMM)
Lamina VIIILamina VIII
Lamina IX ----------Lamina IX ---------- anterior horn (motor) cellanterior horn (motor) cell
Lamina X ----------- gray commissureLamina X ----------- gray commissure
Lamina I ---------- posteromarginal nucleusLamina I ---------- posteromarginal nucleus
Lamina II ----------Lamina II ---------- substantia gelatinosa of Rolandosubstantia gelatinosa of Rolando
Lamina III, IV ----- nucleus propriusLamina III, IV ----- nucleus proprius
Lamina V, VILamina V, VI
Lamina VII --------- intermediate grayLamina VII --------- intermediate gray
intermediolateral cell column (IML)intermediolateral cell column (IML)
Clarke’s column (Nucleus dorsalis)Clarke’s column (Nucleus dorsalis)
intermediomedial cell column (IMM)intermediomedial cell column (IMM)
Lamina VIIILamina VIII
Lamina IX ----------Lamina IX ---------- anterior horn (motor) cellanterior horn (motor) cell
Lamina X ----------- gray commissureLamina X ----------- gray commissure

Sensory & MotorSensory & Motor
PathwaysPathways

• There is a continuous flow of information between the brain,
spinal cord, and peripheral nerves. This information is
relayed by sensory (ascending) and motor (descending)
‘pathways’.
• Generally the pathways:
 Consists of a chain of tracts, associated nuclei and
varying number of relays (synapses)
 Consist of two or three neurons
 Exhibit somatotopy (precise spatial relationships)
 Decussate
 Involve both the brain and spinal cord
 Are paired (bilaterally and symmetrically)

Somatic Sensory PathwaysSomatic Sensory Pathways

Sensory Pathways
• Monitor conditions both inside the body and in the
external environment
• Sensation-stimulated receptor passes information to
the CNS via afferent (sensory) fibers
• Most sensory information is processed in the spinal
cord , thalamus, or brain stem. Only 1% reaches the
cerebral cortex and our conscious awareness
• Processing in the spinal cord can produce a rapid
motor response (stretch reflex)
• Processing within the brain stem may result in
complex motor activities (positional changes in the
eye, head, trunk)

Sensory Pathways
• Contain a sequence of THREE
neurons from the receptor to the
cerebral cortex
• First order neuron: Sensory
neuron that delivers information
from the receptor to the CNS.
• Cell body located in the dorsal
root ganglion. The Axon (central
process) passes to the spinal cord
through the dorsal root of spinal
nerve gives many collaterals
which take part in spinal cord
reflexes runs ipsilaterally and
synapses with second-order
neurons in the cord and medulla
oblongata
11
22
33

• Second order neuron:
–Has cell body in the
spinal cord or medulla
oblongata
–Axon decussate &
–Terminate on 3rd order
neuron
• Third order neuron:
–Has cell body in thalamus
–Axon terminates on
cerebral cortex
ipsilaterally

White Matter: Pathway GeneralizationsWhite Matter: Pathway Generalizations
• Ascending and descending fibers are organized in distinct
bundles which occupy particular areas and regions in the
white matter
• Generally long tracts are located peripherally in the white
matter, while shorter tracts are found near the gray matter
• The TRACT is a bundle of nerve fibers (within CNS)
having the same origin, course, destination & function
• The name of the tract indicates the origin and
destination of its fibers
• The axons within each tract are grouped according to
the body region innervated

Tracts of the Spinal CordTracts of the Spinal Cord
• Tracts that serve to join brain to the spinalTracts that serve to join brain to the spinal
cordcord
– AscendingAscending
– DescendingDescending
• Fibers that interconnect adjacent or distantFibers that interconnect adjacent or distant
segments of the spinal cordsegments of the spinal cord
– IntersegmentalIntersegmental (propriospinal)(propriospinal)

Intersegmental TractsIntersegmental Tracts
• Extensive fiber connections
between spinal segments
• Fasciculus proprius
– Short ascending &
descending fibers
– Both crossed & uncrossed
– Begin and end within the
spinal cord
– Participate in
intersegmental spinal
reflexes
– Present in all funiculi
adjacent to gray matter

Intersegmental Tracts
• Dorsolateral tract of Lissauer:
Primary sensory fibers
carrying pain, temperature and
touch information bifurcate
upon entering the spinal cord.
Their branches ascend and
descend for several spinal
segments in the dorsolateral
tract, before synapsing in the
dorsal horn
Intersegmental fibers, establishing connections with
neurons in the opposite half of the spinal cord, cross
the midline in the anterior white commissure

Ascending Spinal Tracts
Transmit impulses:
• Concerned with specific sensory modalities: pain,
temperature, touch, proprioception, that reach a
conscious level (cerebral cortex)
–Dorsal column funiculi
–Spinothalamic tracts
• From tactile and stretch receptors to subconscious
centers (cerebellum)
–Spinocerebellar tracts

• Three major pathways carry sensory information
Posterior column pathway (gracile & cuneate
fasciculi)
Anterolateral pathway (spinothalamic)
Spinocerebellar pathway

Ascending Spinal Tracts
• Dorsal white column
• Lateral spinothalamic
• Anterior spinothalamic
• Anterior spinocerebellar
• Posterior spinocerebellar
• Cuneocerebellar
• Spinotectal
• Spinoreticular
• Spino-olivary
• Visceral sensory tracts

Dorsal ColumnDorsal Column
• Contains two tracts,
Fasciculus gracilis (FG)
& fasciculus cuneatus
(FC)
• Carry impulses
concerned with
proprioception and
discriminative touch
from ipsilateral side of
body
• Contain the axons of
primary afferent
neurons that have
FG contains fibers received at sacral,
lumbar and lower thoracic levels, FC
contains fibers received at upper

• Fibers ascend without
interruption where they
terminate upon 2nd
order neurons
in nucleus gracilis and nucleus
cuneatus
• The axons of the 2nd
order
neurons decussate in the
medulla as internal arcuate
fibers and ascend through the
brain stem as medial lemniscus.
• The medial lemniscus terminates
in the ventral posterior nucleus
of the thalamus upon 3rd
order
neurons, which project to the
somatosensory cortex
(thalamocortical fibers)
•

Posterior White Column -Posterior White Column -
Medial Lemniscal PathwayMedial Lemniscal Pathway
Posterior White Column -Posterior White Column -
Medial Lemniscal PathwayMedial Lemniscal Pathway
medial lemniscusmedial lemniscus
LemniscalLemniscal
decussationdecussation
internal arcuate fiberinternal arcuate fiber
posterior whiteposterior white
columncolumn
posterior rootposterior root
-- ipsilateralipsilateral loss of discriminative touchloss of discriminative touch
sensation and conscious proprioceptionsensation and conscious proprioception
belowbelow the level of lesionthe level of lesion
Lower limb position sense is tested by standing upright with feetLower limb position sense is tested by standing upright with feet
together and then closing the eyes. There will be loss of balancetogether and then closing the eyes. There will be loss of balance
with the eyes shutwith the eyes shut (Romberg,s sign).(Romberg,s sign). For the same reason thereFor the same reason there
will be difficulty with walking in dark or keeping the balancewill be difficulty with walking in dark or keeping the balance
when washing the face with eyes shut. These are examples ofwhen washing the face with eyes shut. These are examples of
sensory ataxia.sensory ataxia.

Spinothalamic TractsSpinothalamic 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 somato-
topically arranged, with those
for the lower limb lying most
superficially and those for the
upper limb lying deeply
Information is sent to the
primary sensory cortex on
the opposite side of the
body

Spinothalamic TractSpinothalamic TractSpinothalamic TractSpinothalamic Tract
spinothalamicspinothalamic
tracttract
anterior whiteanterior white
commissurecommissure
posterior rootposterior root
decussationdecussation
-- contra lateralcontra lateral loss of pain and temperatureloss of pain and temperature
sensationsensation belowbelow the level of lesionthe level of lesion

Lateral Spinothalamic TractLateral 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 substantia gelatinosa),
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

Anterior Spinothalamic TractAnterior 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

Spino-reticulo-thalamic SystemSpino-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

Fast PainFast Pain Slow PainSlow Pain
Sharp, prickingSharp, pricking Dull, burningDull, burning
Group III (AGroup III (Aδδ) fiber) fiber Group IV (C) fiberGroup IV (C) fiber
Short latencyShort latency Slower onsetSlower onset
Well localizedWell localized DiffuseDiffuse
Short durationShort duration Long durationLong duration
Less emotionalLess emotional Emotional, autonomic responseEmotional, autonomic response
Not blocked by morphineNot blocked by morphine Blocked by morphineBlocked by morphine
Neospinothalamic TractNeospinothalamic Tract Paleospinothalamic TractPaleospinothalamic Tract
Comparison of Fast and Slow PainComparison of Fast and Slow Pain ------ Spinothalamic Tract------ Spinothalamic TractComparison of Fast and Slow PainComparison of Fast and Slow Pain ------ Spinothalamic Tract------ Spinothalamic Tract

Spinocerebellar TractsSpinocerebellar 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 tactile receptors to
the cerebellum for the control
of posture and coordination of
movements

Posterior Spinocerebellar TractsPosterior 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 TractsVentral Spinocerebellar Tracts
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

Spinocerebellar TractSpinocerebellar TractSpinocerebellar TractSpinocerebellar Tract

Spinotectal TractSpinotectal 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
order
neuron lie in base of the dorsal
horn
• Axons of 2nd
order neuron cross
to opposite side, and project to
the periaqueductal gray matter
and superior colliculus in the
midbrain

Spino - olivary TractSpino - 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 TractSpinoreticular Tract
• Originates in laminae IV-
VIII
• 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

Somatic Motor PathwaysSomatic Motor Pathways

Motor PathwaysMotor 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 PathwaysMotor 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) SystemDirect (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 (Extra pyramidal) SystemIndirect (Extra pyramidal) 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 TractsDescending Spinal Tracts
• Pyramidal
– Corticospinal
• Extra pyramidal
– 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 contra lateral side

-- ipsilateralipsilateral UMN syndromeUMN syndrome
atat the level of lesionthe level of lesion
Corticospinal TractCorticospinal TractCorticospinal TractCorticospinal Tract
Corona RadiataCorona Radiata
internal Capsule, Posterior Limbinternal Capsule, Posterior Limb
Crus Cerebri, Middle PortionCrus Cerebri, Middle Portion
Longitudinal Pontine FiberLongitudinal Pontine Fiber
PyramidPyramid
Pyramidal DecussationPyramidal Decussation
Corticospinal TractCorticospinal Tract
- Lateral and Anterior- Lateral and Anterior
CR
IC
LPF
Pyr
PD LCST
ACST

Rubrospinal TractRubrospinal Tract
• Controls the tone of limb flexor
muscles, being excitatory to
motor neurons of these
muscles
• Origin: Red nucleus
• Axons course ventro-medially,
cross in ventral tegmental
decussation, descend in spinal
cord ventral to the lateral
corticospinal tract
• Cortico-rubro-spinal pathway
(Extra pyramidal)

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
(Extra pyramidal)

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

Reticulospinal Tracts
• Influence voluntary movement, reflex
activity and muscle tone by
controlling the activity of both alpha
and gamma motor neurons
• Mediate pressor and depressor
effect on the circulatory system
• Are involved in control of breathing
• Origin: pontine & medullary reticular
formation
• Medial (pontine) reticulospinal tract
descends ipsilaterally
• Lateral (medullary) reticulospinal
tract descends bilaterally
• Both tracts located in the ventral
funiculus

Descending Autonomic
Fibers(Hypothalamospinal tract)
• The higher centers associated
with the control of autonomic
activity are situated mainly in
the hypothalamus
• The fibers run in the
reticulospinal tracts
• Terminate on the autonomic
neurons in the lateral horn of
thoracic & upper lumbar
(sympathetic) and sacral
segments (parasympathetic)
levels of the spinal cord

upper motor neuronupper motor neuron
UMNUMN
upper motor neuronupper motor neuron
UMNUMN
SOMATIC MOTOR SYSTEMSOMATIC MOTOR SYSTEMSOMATIC MOTOR SYSTEMSOMATIC MOTOR SYSTEM
lower motor neuron
LMNLMN
Brain StemBrain Stem
DescendingDescending
PathwayPathway
Final Common PathwayFinal Common Pathway
EFFECTORS
skeletal muscle
Pyramidal Tract
VOLUNTARY
CONTROL
AUTOMATIC CONTROL
Rubrospinal TractRubrospinal Tract
Tectospinal TractTectospinal Tract
Vestibulospinal TractVestibulospinal Tract
MLFMLF
Reticulospinal TractReticulospinal Tract
REFLEX

Spinal Cord SyndromeSpinal Cord SyndromeSpinal Cord SyndromeSpinal Cord Syndrome
Location ofLocation of
Symptoms inSymptoms in
Spinal DiseaseSpinal Disease
ipsilateral to lesion contralateral to lesion

Upper Motor Neuron (UMN) vs Lower Motor Neuron (LMN) SyndromeUpper Motor Neuron (UMN) vs Lower Motor Neuron (LMN) Syndrome
UMN syndromeUMN syndrome LMN SyndromeLMN Syndrome
Type of ParalysisType of Paralysis Spastic ParesisSpastic Paresis Flaccid ParalysisFlaccid Paralysis
AtrophyAtrophy No (Disuse) AtrophyNo (Disuse) Atrophy SevereSevere AtrophyAtrophy
Deep Tendon ReflexDeep Tendon Reflex IncreaseIncrease Absent DTRAbsent DTR
Pathological ReflexPathological Reflex PositivePositive BabinskiBabinski SignSign AbsentAbsent
Superficial ReflexSuperficial Reflex AbsentAbsent PresentPresent
Fasciculation andFasciculation and AbsentAbsent Could beCould be
FibrillationFibrillation PresentPresent

Predominantly Motor SyndromesPredominantly Motor Syndromes
• Poliomyelitis (Infantile Paralysis)Poliomyelitis (Infantile Paralysis)
- viral infection of lower motor neuron- viral infection of lower motor neuron
- LMN syndrome at the level of lesion- LMN syndrome at the level of lesion
• Amyotrophic Lateral Sclerosis (ALS)Amyotrophic Lateral Sclerosis (ALS)
- combined LMN and UMN lesion- combined LMN and UMN lesion
- LMN syndrome at the level of lesion- LMN syndrome at the level of lesion
- UMN syndrome below the level of lesion- UMN syndrome below the level of lesion
- Lou Gehrig’s disease in USA- Lou Gehrig’s disease in USA

Amyotrophic Lateral SclerosisAmyotrophic Lateral SclerosisAmyotrophic Lateral SclerosisAmyotrophic Lateral Sclerosis
1. corticospinal
tract
2. lower motor
neuron (LMN)

Spinal CordSpinal Cord
SyndromeSyndrome
AmyotrophicAmyotrophic
Lateral SclerosisLateral Sclerosis
(ALS)(ALS)
Lou Gherig’sLou Gherig’s
DiseaseDisease
SyndromeSyndrome
(ALS)(ALS)
DiseaseDisease
Lou "The Iron Horse" Gehrig (1903-41)Lou "The Iron Horse" Gehrig (1903-41)
3.40, 2131(1925-39), 23 GSH, 147 RBI avg.

SyndromeSyndrome
(ALS)(ALS)
DiseaseDisease
SyndromeSyndrome
(ALS)(ALS)
DiseaseDisease Stephen Haking (1946- )Stephen Haking (1946- )
British Physicist, A Brif History of Time

Predominantly Sensory SyndromesPredominantly Sensory Syndromes
• Herpes ZosterHerpes Zoster
- inflammatory reactions of spinal ganglion- inflammatory reactions of spinal ganglion
- severe pain on the dermatomes of affected ganglion- severe pain on the dermatomes of affected ganglion
• Tabes DorsalisTabes Dorsalis
- common variety of neurosyphilis- common variety of neurosyphilis
- posterior column and spinal posterior root lesion- posterior column and spinal posterior root lesion
- loss of discriminative touch sensation and conscious- loss of discriminative touch sensation and conscious
proprioception below the level of lesionproprioception below the level of lesion
- posterior column ataxia- posterior column ataxia
- lancinating pain- lancinating pain
- loss of deep tendon reflex (DTR)- loss of deep tendon reflex (DTR)

Herpes Zoster (Shingles)Herpes Zoster (Shingles)
• varicella-zoster virusvaricella-zoster virus
reactivation fromreactivation from
the dorsal root gangliathe dorsal root ganglia
• unilateral vesicularunilateral vesicular
eruption withineruption within
a dermatomea dermatome
• T3 to L3 dermatomeT3 to L3 dermatome
lesions are frequentlesions are frequent
• zoster ophtahalmicuszoster ophtahalmicus
(ophthalmic division(ophthalmic division
of trigeminal n., Vof trigeminal n., V11))
• Ramsey-Hunt syndromeRamsey-Hunt syndrome
(sensory br. of VII)(sensory br. of VII)
• acyclovir, antiviral agentacyclovir, antiviral agent

Sub acute Combined DegenerationSub acute Combined Degeneration
(Combined System Disease)(Combined System Disease)
LesionLesion
- posterior white column- posterior white column
- corticospinal tract (UMN)- corticospinal tract (UMN)
SymptomSymptom
- loss of discriminative touch sensation and conscious- loss of discriminative touch sensation and conscious
proprioception below the level of lesionproprioception below the level of lesion
- ipsilateral UMN syndrome below the level of lesion- ipsilateral UMN syndrome below the level of lesion

Subacute Combined DegenerationSubacute Combined DegenerationSubacute Combined DegenerationSubacute Combined Degeneration
1. corticospinal
tract
2. posterior
white column

Syringomyelia, HematomyeliaSyringomyelia, Hematomyelia
LesionLesion
- central canal of spinal cord- central canal of spinal cord
- gradually extended to peripheral part of the cord- gradually extended to peripheral part of the cord
SymptomSymptom
- initial symptom is bilateral loss of pain- initial symptom is bilateral loss of pain
(compression of anterior white commissure)(compression of anterior white commissure)
- variety of symptoms appear- variety of symptoms appear
according to the lesion extended from central canalaccording to the lesion extended from central canal

Syringomyelia - Initial SymptomsSyringomyelia - Initial SymptomsSyringomyelia - Initial SymptomsSyringomyelia - Initial Symptoms

Brown-Sequard syndromeBrown-Sequard syndrome
(spinal cord hemi section)(spinal cord hemi section)
Major SymptomsMajor Symptoms
1. ipsilateral1. ipsilateral UMN syndromeUMN syndrome belowbelow the level of lesionthe level of lesion
2. ipsilateral2. ipsilateral LMN syndromeLMN syndrome atat the level of lesionthe level of lesion
3. ipsilateral loss of3. ipsilateral loss of discriminative touch sensationdiscriminative touch sensation andand
conscious proprioceptionconscious proprioception belowbelow the level of lesionthe level of lesion
(posterior white column lesion)(posterior white column lesion)
4.4. contra lateralcontra lateral loss ofloss of pain and temperaturepain and temperature sensationsensation
belowbelow the level of lesionthe level of lesion (spinothalamic tract lesion)(spinothalamic tract lesion)

Brown-Sequard Syndrome (Spinal Cord Hemisection)Brown-Sequard Syndrome (Spinal Cord Hemisection)Brown-Sequard Syndrome (Spinal Cord Hemisection)Brown-Sequard Syndrome (Spinal Cord Hemisection)
1
1 '
1 '
2 ' 2
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1
1
3
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44 '
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55 '

Spinal cord Anatomy by Dr. Naseer (RMC)

Spinal cord Anatomy by Dr. Naseer (RMC)

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