1. Neuroanatomy of Spinal cord
Presentor: Dr.Deepika.T
Post graduate student
Moderator: Dr.Byrareddy
Professor
Department of General Medicine,
RRMCH, Bengaluru
3. Gross Anatomy
Spinal cord lies in vertebral canal
Extends from level of cranial border of atlas to lower border of L1
or upper border of L2 vertebrae in adults
About 18 inches (45 cm) long
1/2 inch (14 mm) wide
Approx weight = 30 gms
Corresponding average length of spinal column is 70cm
Anchored to duramater by dentate ligament
Cylindrical in shape & flattened dorso ventrally
4. Gross Anatomy
Has cervical (C5 to T1) and lumbar (L3 to S2) enlargements
Below Lumbar enlargement, spinal cord narrows ending as conus
medullaris
CNS tissue ends between vertebrae L1 and L2 whereas in neonates
ends at upper border of L3
At birth, cord and vertebrae are about the same size but cord stops
elongating at around age 4
Although it is a continuous & non segmental structure, 31 pair of
originating nerves give it a segmental appearance
31 pairs of spinal nerves: 8C, 12T, 5L, 5S & 1Co
Each pair of nerves exits the vertebral column at the level it initially
lined up with at birth
5. Gross Anatomy
Conus medullaris:
thin, conical end of the spinal cord
Cauda equina:
nerve roots extending below conus medullaris
Filum terminale:
thin thread of fibrous tissue at end of conus medullaris
attaches to coccygeal ligament
8. Epidural space :
between spinal duramater and walls of spinal column,
contains loose connective and areolar tissue
Subdural space
between arachnoid mater and dura mater
Subarachnoid space:
between arachnoid mater and pia mater
filled with cerebrospinal fluid (CSF)
SPACES
9. Structures of the Spinal Cord
Paired denticulate
ligaments:
extend from pia mater to dura
mater
stabilize side-to-side movement
Blood vessels:
along surface of spinal pia mater
within subarachnoid space
10.
11. Cross Sectional Anatomy
Anterior median fissure – separates anterior funiculi
Posterior median sulcus – divides posterior funiculi
12. Cross Sectional Anatomy
Spinal cord has a narrow, fluid filled central canal
Central canal is surrounded by butterfly or H-shaped
gray matter containing sensory and motor nuclei
(soma), unmyelinated processes, and neuroglia
White matter is on the outside of the gray matter
(opposite of the brain) and contains myelinated and
unmyelinated fibers
14. Gray Matter: Organization
Dorsal half – sensory roots and ganglia
Ventral half – motor roots
Dorsal and ventral roots fuse laterally to form spinal nerves
Four zones are evident within the gray matter – somatic sensory
(SS), visceral sensory (VS), visceral motor (VM), and somatic
motor (SM)
15. SENSORY NUCLEUS
Substantia gelatinosa- relay station for spinothalamic tract
Nucleus proprius(largest nucleus)- relay station for dorsal column
tracts
Nucleus dorsalis(clarkes column)- relay station for spinocerebellar
tracts
INTERMEDIOLATERAL NUCLEUS
It extends from T1 to L2 , and contains autonomic motor neurons
that give rise to preganglionic fibres of sympathetic nervous system
MOTOR NEURONS
They innervate the visceral and skeletal muscles. Lateral nucleus
innervates the limb muscles and medial nucleus innervates the
midline/ axial muscles
NUCLEI IN GRAY MATER
16. White matter
Tracts (or fasciculi):
bundles of axons in the white columns
relay certain type of information in same direction
Ascending tracts:
carry information to brain
Descending tracts:
carry motor commands to spinal cord
17. Cross-sectional anatomy – white mater
White matter
3 funiculi (posterior, lateral,
anterior)
Ascending, descending,
transverse
Consist of “tracts” containing
similarly functional axons
All tracts are paired
Most cross over (decussate) at
some point
Most consist of a chain of 2 or 3
successive neurons
19. ASCENDING TRACTS
LATERAL SPINOTHALAMIC TRACT:
Pain and temperature
ANTERIOR SPINOTHALAMIC TRACT:
Crude touch and pressure
DORSAL COLUMN TRACT { Fasciculus gracilis(LL), Fasciculus
cuneatus(UL) } :
Carries conncious proprioception , fine touch , vibration, pressure
and stereognossus
DORSAL SPINOCEREBELLAR AND VENTRAL
SPINOCEREBELLAR TRACT:
Carries unconscious proprioception
20. Spinothalamic tract
First order neuron
impulses from free nerve endings transmitted to spinal cord
Central processes enters the spinal cord through posterior nerve root, proceed to the tip
of dorsal gray column
Second order neuron
In the dorsal horn cross to the opposite side (decussates)
Ascends in the contralateral ventral & lateral column
Ends in VPL nucleus of thalamus
Third order neuron
From the VPL nucleus of thalamus projects to cerebral cortex (area 3,1,2)
21.
22. Lateral spinothalamic tract
Clinical application
Destruction of LSTT
Loss of pain & thermal sensation
- Below the level of lesion
- On the contralateral side of the body
Patient will not respond to pinprick & cannot recognise
hot & cold
23. Anterior spinothalamic tract
Clinical application
Destruction of ASTT
Loss of light touch & pressure sense
- Below the level of lesion
- On the contralateral side of the body
(Discriminative touch will still be present, as this infprmation is carried by posterior
column)
24. Fasciculus gracilis & cuneatus
Occupy the posterior white column of the cord
FG being medial to FC
FG contains fibers received at SACRAL,
LUMBAR and LOWER THORACIC levels
FC contains fibers received at UPPER
THORACIC & CERVICAL levels
25. Fasciculus gracilis & cuneatus
First order neuron
Ascend without interruption and terminate upon 2nd
order neurons in NUCLEUS GRACILIS & NUCLEUS
CUNEATUS
Second order neuron
Axons of 2nd order neurons decussate in the
medulla as internal arcuate fibers and ascend through
the brain as medial lemniscus
Third order neuron
Medial lemniscus terminates in the VENTRAL
POSTERIOR nucleus of THALAMUS,3rd order neurons
project to somatosensory cortex
26. Fasciculus gracilis & cuneatus
Clinical application
Destruction of Fasciculus gracilia & cuneatus
Loss of muscle joint sense, position sense, vibration sense
& tactile discrimination light touch & pressure sense
- Below the level of lesion
- On the same side of the body
27. POSTERIOR & ANTERIOR SPINOCEREBELLAR TRACT
Transmit unconscious proprioceptive information to the cerebellum
Receive input from muscle spindles and pressure receptors
Involved in coordination of posture and movement of individual muscles of the lower limb
SPINOTECTAL TRACT
Transmits pain, thermal, tactile information to superior colliculus for spinovisual reflexes
Integrate visual and somatic sensory information (it brings about the movement of eye and
head towards the source of information)
SPINORETICULAR TRACT
Uncrossed fibers, synapse with neurons of reticular formation (important role in influencing
level of consciousness)
SPINO-OLIVARY TRACT
Located in anterior funiculus
Carries unconscious proprioception as well as cutaneous impulses from ipsilateral side of
the body to the olivary bodies and involved in maintaining balance.
29. PYRAMIDAL TRACT ( ANTERIOR AND LATERAL
CORTICOSPINAL TRACT):
Skilled voluntary movements
RUBROSPINAL TRACT:
Facilitates flexors
Inhibits extensors
TECTOSPINAL TRACT:
Responsible for coordinated movements of head and neck,
eyeball and limbs based on visual stimulus
VESTIBULOSPINAL TRACT
Also called as postural tract
Helps in maintaining posture
DESCENDING TRACTS
30. CORTICOSPINAL TRACT
Arises from the pyramidal cells of cerebral cortex
Fibers travel through
Corona radiata
Posterior limb of internal capsule
Cerebral peduncle (middle 3/5th)
Pons
Medulla oblongata
90% of the fibers crosses the midline in medulla to travel down as lateral
corticospinal tract
Remaining uncrossed fibers travel down as anterior corticospinal tract
Eventually fibers cross midline and terminate on LMN of anterior gray column
of respective spinal cord segments
31. RUBROSPINAL TRACT
Nerve cells in Red nucleus
Nerve fibers / axons
Cross the midline
Descend as rubrospinal tract
Terminate in anterior gray column of spinal cord
Facilitate the activity of flexor muscles
32. TECTOSPINAL TRACT
Nerve cells in superior colliculus of midbrain
Nerve fibers / axons
Cross the midline
Descend close to medial longitudinal fasciculus
Terminate in the anterior gray column of upper cervical segments of spinal
cord
Responsible for reflex movement of head & neck in response to visual
stimuli
33. VESTIBULOSPINAL TRACT
Nerve cells in vestibular nucleus in pons and medulla
oblongata
Nerve fibers / axons
Descends uncrossed through medulla and through the length of
spinal cord
Synapse with neuron in anterior gray column of spinal cord
Helps in maintaining the balance by facilitating the activity
of extensor muscles
34. RETICULOSPINAL TRACT
Nerve cells in reticular formation of caudal pons & rostral
medulla
Nerve fibers / axons
Consists of 2 separate pathways (Pontine reticulospinal tract &
medullary reticulospinal tract)
Pass through pons & medulla
Ends at anterior gray column (mainly uncrossed)
Facilitates voluntary and reflex activity
They influence the action of motor neurons of phrenic and
intercostal nerves, thus control RESPIRATION.
38. ANTERIOR SPINAL ARTERY
Origin : formed by union of 2 small spinal branches
of right & left vertebral arteries in the upper cervical
canal
Course : runs caudally in the anterior median fissure
Termination : filum terminale
Supplies : anterior 2/3rd of the cord
39. ANTERIOR SPINAL ARTERY
Due to occlusion (thrombosis or compression) of
anterior spinal artery
Results in
Motor symptoms: coz of involvement of corticospinal tracts
and anterior gray columns
Bilateral loss of pain & temperature sensation due to
ischemia of spinothalamic tracts
40. POSTERIOR SPINAL ARTERY
Origin : branched from either
Vertebral
Posterior inferior cerebellar arteries
Course :
runs down in posterolateral sulcus, divides into 2 collateral arteries
medial and lateral along the posterior nerve roots
Thus there are 5 longitudinal arteries around the spinal cord. These
arteries reinforced by the segmental arteries to form 5 longitudinal
arterial trunks
These communicate around the cord forming pial plexus, the arterial
vaso-corona
Supplies : posterior 1/3rd of the spinal cord
41.
42. SEGMENTAL ARTERIES
They reach the spinal cord as anterior and posterior radicular
arteries along the corresponding roots of the spinal nerves
respectively and nourish the nerve roots
Anterior radicular arteries: larger and less in number
Posterior radicular arteries: smaller and more in number
Importance: end arteries, if anyone of them is blocked, there
will not be any collateral circulation
Branches of
Deep cervical
Ascending cervical
Intercostal &
Lumbar
43. CLINICAL CORRELATION
Artery of T11/ T12 spinal segment (arteria radicularis magna)
is remarkably large, arises directly from aorta on its left side
A fracture of vertebra involving this artery leads to ischemia of
several segments of the cord
T1, T4 and L1 segments – the meeting places of different
major arteries are vulnerable to ischemic necrosis
44. VENOUS DRAINAGE
Two median longitudinal – one in the anterior median
fissure another in posteromedian sulcus
Two anterolateral - one on either side posterior to
the anterior nerve roots
Two posterlateral – one on either side posterior to
posterior nerve roots
45. VENOUS DRAINAGE
Drain below through internal vertebral venous
plexus into the vertebral posterior intercostal, lumbar
and lateral scral veins
Internal vertebral venous plexus communicates
above with the basilar venous plexus.