1.
SPINAL CORD ANATOMY
DR. UTKARSSH A W

2.
Gross Appearance
• Cylindrical in shape
• Foramen magnum  L1/L2 (adult)
• L3 (newborn)
• Occupies upper ⅔ of vertebral canal
• Surrounded by 3 layers of meniges:
– dura mater
– arachnoid mater
– pia mater
• CSF in subarachnoid space

3.
31 pairs of spinal nerves:
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

4.
 With increasing age, the vertebral column and
dura lengthen more rapidly than the neural tube,
and the terminal end of the spinal cord gradually
shifts to a higher level.
 At birth, this end is at the level of the third
lumbar vertebra.
 As a result of this disproportionate growth, spinal
nerves run obliquely from their segment of origin
in the spinal cord to the corresponding level of the
vertebral column.

5.
• Dorsal root – sensory fibres
• Ventral root – motor fibres
• Dorsal and ventral roots join at
intervertebral foramen to form the spinal
nerve

6.
Structure Of The Spinal Cord

7.
Gray Matter
• H-shaped pillar with anterior & posterior gray horns
• United by gray commissure containing the central
canal
• Lateral gray column (horn) present in thoracic & upper
lumbar segments
• Amount of gray matter related to the amount of
muscle innervated
• Consists of nerve cells, neuroglia, blood vessels

8.
Nerve cells in the anterior gray columns
• Large & multipolar
• Axons pass out in the anterior nerve roots as
α-efferents
• Smaller nerve cells are multipolar
• Axons pass out in anterior roots as -ɣ
efferents

9.
Nerve cells in the posterior gray columns
• 4 nerve cell groups
• Substantia gelatinosa
– situated at the apex
– throughout the length of spinal cord
– composed mainly of Golgi Type II neurons
– receives afferent fibres concerning with pain,
temperature & touch from posterior root

10.
• Nucleus proprius
– anterior to substantia gelatinosa
– present throughout the whole length of spinal
cord
– main bulk of cells in posterior gray column
– receives fibers from posterior white column that
are assoc with proprioception, 2-point
discrimination & vibration

11.
• Nucleus dorsalis (Clark’s column)
– base of posterior column
– C8 – L3 / L4
– associated with proprioceptive endings
(neuromuscular spindles & tendon spindles)
• Visceral afferent nucleus
– lateral to nucleus dorsalis
– T1 – L3
– receives visceral afferent info

12.
• Nerve cells in the lateral gray columns
• Formed by the intermediolateral group of
cells
• T1 – L2 / L3
• Cells give rise to preganglionic sympathetic
fibres
• In S2, S3, S4; they give rise to preganglionic
parasympathetic fibres

13.
The gray commissure & central canal
◦ connects the gray on each side
◦ central canal in the centre
◦ posterior gray commissure
◦ anterior gray commissure
◦ central canal present throughout
◦ superiorly continuous with the central canal of
medulla oblongata
◦ inferiorly, expands as terminal ventricle
◦ terminates within the root of filum terminale

14.
White Matter
• Divided into
– anterior white column
– lateral white column
– posterior white column
• Consists of nerve fibres, neuroglia, blood
vessels
• White due to myelinated fibres

15.
Tracts
• Ascending
• Descending
• Intersegmental

16.
Ascending Tracts
• Fibres that ascend from spinal cord to higher
centres
• Conduct afferent information which may or
may not reach consciousness
• Information may be
– exteroceptive (pain, Tº, touch)
– proprioceptive (from muscles & joints)

17.
Organization
• Ascending pathway that reach consciousness
consists of 3 neurons:
– 1st
-order neuron
– 2nd
-order neuron
– 3rd
-order neuron
• Branch to reticular formation (wakefulness)
• Branch to motor neurons (reflex activity)

18.
• Lateral spinothalamic tract
– pain & Tº
• Anterior spinothalamic tract
– light (crude) touch & pressure
• Fasciculus cuneatus
• Fasciculus gracilis
– discriminatory touch, vibration, info from muscles &
joints
• Anterior spinocerebellar tract
• Posterior spinocerebellar tract
– unconscious info from muscles, joints, skin, subcut

19.
• Spinotectal tract
– spinovisual reflexes
• Spinoreticular tract
– info from muscles, joints & skin to reticular
formation
• Spino-olivary tract
– indirect pathway to cerebellum

20.
Lateral spinothalamic tract
• Pain & temp pathways
• 1st
-order neurons
• Pain conducted by δ A-type fibres & C-type fibres
• 2nd
-order neurons
– decussate to the opposite side
– ends in thalamus (ventral posterolateral nucleus
• 3rd
-order neurons
– ends in sensory area in postcentral gyrus

21.
Anterior spinothalamic tracts
• Light (crude) touch & pressure pathways

22.
Posterior white column
• Discriminative touch, vibratory sense,
conscious muscle joint sense (conscious
proprioception)

23.
Posterior spinocerebellar tract
• Muscle joint sense pathways to cerebellum
• Unconscious proprioception
• Muscle joint info from muscle spindles, GTO,
joint receptors of the trunk & lower limbs
• Info is used by the cerebellum in the
coordination of movements & maintenance
of posture

24.
Anterior spinocerebellar tract
• Majority of 2nd
-order neurons cross to the
opposite side
• Enter cerebellum through superior cerebellar
peduncle
• Info from trunk, upper & lower limbs
• Also carries info from skin & subcut tissue

25.
Descending Tracts
• Lower motor neurons
• Upper motor neurons
• Corticospinal tracts
– concerned with voluntary, discrete, skilled
movements

26.
• Reticulospinal tract
– facilitates or inhibits voluntary movement or reflex
activity
• Tectospinal tract
– reflex postural movements in response to visual
stimuli
• Rubrospinal tract
– facilitates activity of flexor muscles & inhibits
activity of extensor muscles
• Vestibulospinal tract
– facilitates extensor muscles, inhibits flexor muscles

27.
Meninges
• Dura mater
• Arachnoid mater
• Pia mater

28.
Dura mater
• Dense, strong fibrous membrane
• Encloses the spinal cord & cauda equina
• Continuous above with meningeal layer of
dura covering the brain
• Ends at the level of S2
• Separated from wall of vertebral canal by the
extradural space
• Contains loose areolar tissue & internal
vertebral venous space

29.
Arachnoid mater
• Delicate impermeable membrane
• Lies between pia and dura mater
• Separated from pia mater by subarachnoid
space
• Continuous above with arachnoid mater
covering the brain
• Ends on filum terminale at level of S2

30.
Pia mater
• Vascular membrane
• Closely covers spinal cord
• Thickened on either side between nerve
roots to form the ligamentum denticulatum

31.
Blood supply
Arteries of the spinal cord
• Anterior spinal artery
• Posterior spinal artery
• Segmental spinal arteries

32.
Anterior spinal artery
• Formed by the union of 2 arteries
• From vertebral artery
• Supply anterior ⅔ of spinal cord
Posterior spinal arteries
• Arise from vertebral artery or posterior
inferior cerebellar arteries (PICA)
• Descend close to the posterior roots
• Supply posterior ⅓ of spinal cord

33.
Segmental spinal arteries
• Branches of arteries outside the vertebral
column
• Gives off the anterior & posterior radicular
arteries
• Arise from lateral intercostal artery or
lumbar artery at any level from T8 – L3

34.
DERMATOMES
• Area of skin innervated by sensory axons
within a particular segmental nerve root
• Knowledge is essential in determining level
of injury
• Useful in assessing improvement or
deterioration

35.
MYOTOMES
• Segmental nerve root innervating a muscle
• important in determining level of injury
• Upper limbs:
C5 - Deltoid
C6 - Wrist extensors
C7 - Elbow extensors
C8 - Long finger flexors
T 1 - Small hand muscles

36.
• Lower Limbs :
L2 - Hip flexors
L3,4 - Knee extensors
L4,5– S1 - Knee flexion
L5 - Ankle dorsiflexion
S1 - Ankle plantar flexion

37.
Sign Upper motor neurone Lower motor neurone
1) Weakness Voluntary movements
are disturbed
Paralysis of muscles
supplied by that segment
or nerve
2) Tone Hypertonia (clasp- knife
spasticity
Hypotonia
3) Reflex ( tendon) Increased,+- clonus Decreased or absent
4) Reflex ( superficial) Absent or decreased Absent or decreased
5) Plantar response Extensor Flexor or absent
6) Muscle nutrition Disuse atrophy Marked atrophy
7) Fasciculations Absent Present
8) Reaction of
degeneration
Absent Present

38.
SPINAL CORD INJURIES CLASSIFICATION
• Quadriplegia :
injury in cervical region
all 4 extremities affected
• Paraplegia :
injury in thoracic, lumbar or sacral segments
2 extremities affected

39.
Injury either:
1) Complete
2) Incomplete

40.
Complete:
i) Loss of voluntary movement of parts
innervated by segment, this is irreversible
ii) Loss of sensation
iii) Spinal shock

41.
Incomplete:
i) Some function is present below site of
injury
ii) More favourable prognosis overall
iii) Are recognisable patterns of injury,
although they are rarely pure and
variations occur

42.
Injury defined by ASIA Impairment
Scale
ASIA – American Spinal Injury Association :
A – Complete: no sensory or motor function
preserved in sacral segments S4– S5
B – Incomplete: sensory, but no motor function
in sacral segments

43.
C – Incomplete: motor function preserved
below level and power graded < 3
D – Incomplete: motor function preserved
below level and power graded 3 or more
E – Normal: sensory and motor function normal

44.
MUSCLE STRENGTH GRADING
• 5 – Normal strength
• 4 – Full range of motion, but less than
normal strength against resistance
• 3 – Full range of motion against gravity
• 2 – Movement with gravity eliminated
• 1 – Flicker of movement
• 0 – Total paralysis

45.
Spinal Shock :
• Transient reflex depression of cord function
below level of injury
• Initially hypertension due to release of
catecholamines
• Followed by hypotension
• Flaccid paralysis
• Bowel and bladder involved
• Sometimes priaprism develops
• Persists for less than 24 hours (may be as
long as 1 – 4 weeks)

46.
Neurogenic shock:
• Triad of i) hypotension
ii) bradycardia
iii) hypothermia
• More commonly in injuries above T6
• Secondaryto disruption of sympathetic
outflow from T1– L2

47.
• Loss of vasomotor tone – pooling of blood
• Loss of cardiac sympathetic tone – bradycardia
• Blood pressure will not be restored by fluid
infusion alone
• Massive fluid administration may lead to
overload and pulmonary edema
• Vasopressors may be indicated
• Atropine used to treat bradycardia

48.
TYPES OF INCOMPLETE INJURIES
i) Central Cord Syndrome
ii) Anterior Cord Syndrome
iii) Posterior Cord Syndrome
iv) Brown – Sequard Syndrome
v) Cauda Equina Syndrome

49.
CENTRAL CORD SYNDROME
• Also associated with fracture dislocation and
compression fractures
• More centrally situated cervical tracts tend
to be more involved hence
flaccid weakness of arms > legs
• Perianal sensation & some lower extremity
movement and sensation may be preserved

50.
CENTRAL CORD SYNDROME

51.
ANTERIOR CORD SYNDROME
• Due to flexion / rotation
• Anterior dislocation / compression fracture
of a vertebral body encroaching the ventral
canal
• Corticospinal and spinothalamic tracts are
damaged either by direct trauma or ischemia
of blood supply (anterior spinal arteries)

52.
Clinically:
• Loss of power
• Decrease in pain and sensation below lesion
• Dorsal columns remain intact

53.
ANTERIOR CORD SYNDROME

54.
POSTERIOR CORD SYNDROME
Hyperextension injuries with fractures of
the posterior elements of the vertebrae
Clinically:
• Proprioception affected – ataxia and
faltering gait
• Usually good power and sensation

55.
POSTERIOR CORD SYNDROME

56.
Brown – Sequard Syndrome
• Hemi-section of the cord
• Either due to penetrating injuries:
i) stab wounds
ii) gunshot wounds
• Fractures of lateral mass of vertebrae

57.
Clinically:
• Paralysis on affected side (corticospinal)
• Loss of proprioception and fine
discrimination (dorsal columns)
• Pain and temperature loss on the opposite
side below the lesion (spinothalamic)

58.
Brown – Sequard Syndrome

59.
CAUDA EQUINA SYNDROME
• Due to bony compression or disc
protrusions in lumbar or sacral region
Clinically
• Non specific symptoms – back pain
- bowel and bladder dysfunction
- leg numbness and weakness
- saddle parasthesia

60.
Poliomyelitis
• Acute viral infection of the neurones of
anterior gray column
• Motor nuclei of cranial nerves
• Death of motor neurone cells → paralysis &
wasting of muscles
• Muscles of lower limb more often affected

61.
SPINAL TUMOURS

62.
• The first order sensory neurons are in the dorsal
root ganglia or the sensory ganglia of cranial
nerves.
2. The second order sensory neurons are in the
dorsal gray column or various sensory nuclei of
the brainstem.
3. The third order sensory neurons are in the
thalamic nuclei.
The long ascending sensory tracts found in the
spinal cord or the brainstem are formed by
either the first or the second order neurons.

63.
• EXAMPLE:
Typically, the perception of pain travels
through three orders of neurons. The first-
order neurons carry signals from the
periphery to the spinal cord; the second-
order neurons relay this information from
the spinal cord to the thalamus; and the
third-order neurons transmit the information
from the thalamus to the primary sensory
cortex, where the information is processed,
resulting in the "feeling" of pain.