Anatomy and physiology of spinal anaesthesia.

1. Spinal Anaesthesia
Appliedanatomyand
physiology
CHAIRPERSON:DR.S.B GANGADHAR
MODERATOR :DR. PRAKASH
PRESENTOR: DR.DABER PAREED

2. INTRODUCTION
• Spine is one of the most important part
of human body
• It gives structure and support
• Protect the spinal cord

3. • There are
• 7 cervical vertebra
• 12 thoracic vertebra
• 5 lumbar vertebra
• There are five sacral and four coccyx vertebra
which are fused segments

6. PARTS OF THE VERTEBRA
• All vertebra consists of BODY anteriorly
• Two pedicles that project posteriorly
• Two lamella that connect the pedicles
• Lamella gives rise to the transverse process that project
laterally and spinous process that project posteriorly

7. `• The pedicles of these vertebra are notched and
these notches of the each adjacent pair form an
intervertebral foramen through which the spinal
nerves exit the vertebral canal
• Superior and inferior articular processes arise at
the junction of the lamella and the pedicles and
form joints with the adjoining vertebrae

8. LIGAMENTS
• The vertebral bodies are stablized by ligaments that increase in size between the
cervical and lumbar vertebra.. They are
• Supraspinous ligament – stong, thick, fibrous band
from C7 to sacrum
Supraspinous continue as ligamentum nuchae from C7 and attach
to the occipital protruberence at the base of the skull
• Interspinous ligament - Thin , fibrous structure
Extend from the apex & upper surface of a lower spine toward the
root and inferior surface of the next higher vertebrae
• Ligamentum flavum

10. LIGAMENTUM FLAVUM
• The ligamentum flavum consists of yellow elastic tissue
• They extend in perpendicular direction between the
anterior inferior surface of the upper lamina downward
to the anterior superior surface of the lower lamina
• Thus the ligament exists as right and left half in each
intervertebral space with the halves fusing in the
midline

11. Ligamentum flavum
IN NORMAL ADULTS
Thickness- 3-5mm
Height- 15-16mm
Width- 16-20 mm

12. CERVICAL VERTEBRAE
• The 1st cervical vertebra (atlas)has no body
• It consists of an anterior and posterior arch
joined by the thick lateral mass.
• The superior articular facets are strongly
concave for articulation with the occipital
condyles.

13. CERVICAL VERTEBRAE
• The second cervical vertebrae also has similar articulating
surfaces
• The superior articulating facets are large oval and they face
upwards and outwards
• The inferior facets resemble that of a typical cervical
vertebrae
• They have a small transverse process and laminae are thick
and the spine is large strong and bifid

14. • The typical cervical vertebrae are C3–C6.
• Each of these has a small flattened body and a triangular,
relatively large vertebral foramen.
• The pedicles project laterally as well as backwards, and
their superior and inferior notches are about equal.
• The transverse process is short and is pierced by the
foramen transversarium which transmits the vertebral
vessels

15. CERVICAL VERTEBRAE
• The first vertebrae to be clearly palpable while running down the
finger through the nuchal furrow of the spine is C7.
• There are 8 cervical nerves
• All the nerves emerge from C1 to C7 that emerge above their
corresponding vertebrae
• C 8 lies above the first thoracic vertebrae and the remaining spinal
nerves emerge below their corresponding vertebrae.

16. Thoracic vertebrae
• The typical thoracic body is the conventional heart shaped
• The upper 2 bodies show a transition from the cervical type,
whereas the lower vertebrae show some similarity to the
lumbar bodies.
• The bodies of T5-T8 are flattened on their left side; this
asymmetry is produced by the pressure of the descending
aorta & it is these 4 vertebra that become eroded by an
aneurysm of this aortic segment.

17. • The vertebral foramen is circular, diameter relatively
small.
• The spines are long and T1 projects almost horizontally
backwards and is readily felt below the vertebra
prominens.
• It is necessary to give a markedly cephalad angulation to
pass between the spines since the spines of mid thoracic
vertebrae are angled caudally

18. Lumbar vertebrae
• Lumber vertebrae is large kidney shaped.
• Vertebral foramen is roughly triangular, larger than the
thoracic and smaller than the cervical region.
• The pedicles are thick and transverse process are slender
• They increase in length from Ll to L3,then becomes shorter
again so that the third transverse process is longest

19. SACRAL VERTEBRAE
• The sacrum conists of 5 fused vertebrae
• In childhood the sacral vertebrae are connected by
cartilage.
• But progressively fuse into single structure after puberty.
• In the adult only a narrow residue of the sacral discs
persists.
• The fusion of adjacent vertebrae eliminates the
intervertebral foramina.

20. • The sacral hiatus is triangular and obliquely
placed at the lower end of the sacrum
• It is formed as a result from the failure of fusion
of the laminae of the 5th sacral segment
• The epidural space terminates here and hence
forms a convinient portal of entry into this
compartment

21. EMBRYOLOGY
• Embryologically each vertebra develops from 3 primary ossification
centres two lateral for the arch and one central body
• Osific granules appear about the eight month of the embryonic life
where the tranverse processes laterally project
• They travel in 2 directions: backward to form lamina and by
meeting in the midline to form spinous process.
• Anteriorly to meet the body and to form pedicles

22. • In the early fetal life spinal cord is as long as that of the vertebral
column
• At 3 month of the fetal life the tip of the cord is present at the 2nd
coccygeal vertebra
• At 6 month of life it comes to the level of S5
• At birth the spinal cord is at the lower border of L3 vertebrae
• After 1 year of age it comes at the level of L2
DEVELOPMENT

23. Curvature of the spine
• Cervical curve - Convex anterior
• Thoracic curve - Convex posterior
• Lumbar curve - Convex anterior
• Sacrococcygeal – Convex posterior

24. VERTEBRAL ANAMOLIES
 Kyphosis
 Scoliosis
 Spina bifida
 Spina bifida occulta
 Meningocoele
 Myelomeningocoele
 Myelocoele

25. Kyphosis
• Kyphosis is an exaggerated
anterior flexion of the spine
resulting in a rounded or
hunchback appearance.
• Scoliosis and kyphosis are
often seen together.
• More common in women,

26. scoliosis
• Scoliosis is a complex
deformity of the spine
resulting in lateral curvature
and rotation of the vertebrae
as well as deformity of the rib
cage.
• There is usually secondary
with involvement of
respiratory, cardiovascular and
neurological symptoms.

27. Spina bifida
• Neural arch defects result from the failure of fusion of 2 arch
centers.
• Usually this is not associated with any neurological
abnormality(spina bifida occulta), although in such cases
there may be an overlying dimple, lipoma or tuft of hair to
warn the observant of a bony anomaly beneath.
• It may occur any where in the vertebral column but majority
of defects involve L5 or upper sacral regions

28. • Spina bifida occulta – failure
of vertebral arch fusion only.
Meninges and nervous tissue
are normal.
• Meningocele – protrusion of
meninges through a posterior
vertebral defect.

29. • Myelomeningocele – neural
tissue protrudes into, & may
be adherent to, the meningeal
sac.
• Myelocele ( rachischisis) –
failure of fusion of neural tube
results in the production of an
open spinal plate. This
condition is incompatible with
survival.

30. MENINGES
• The spinal meninges consists of three protective
membranes which are continuous with the cranial
meninges.They are
 Dura mater
Arachnoid mater
Pia mater

31. DURA MATER
• The outermost and thickest meningeal layer is the dura mater
• It is the continuation of the inner (meningeal) layer of the cerebral
dura which is made up of dense fibrous tissue
• It extends foramen magnum and ends at the level of S2 where it
fuses with the filum terminale
• The dura is thickest in the posterior midline and thinner in the
lumber area.
• It is largely acellular except for a layer that forms the border
between the dura and the arachnoid matter

32. Arachnoid
• It is a delicate avascular membrane which lies next to the dura
matter
• Thin membrane that encloses the subarachnoid space and CSF.
• It is continuous with the cerebral arachnoid, which loosely invests
the brain, and dips into the longitudinal fissure between the
cerebral hemispheres.

33. Piamater
• It is the innermost layer of the 3 membranes
• It is a vascular connective tissue sheath that closely
invests the brain & spinal cord, and projects into
their sulci and fissures.
• The pia matter extends upto the tip of the spinal
cord where it becomes filum terminale which
anchors the spinal cord to the sacrum

34. Subarachnoid space
• It is the space that lies between the arachnoid matter and pia matter
• It contains the CSF.
• This space communicates with the tissue spaces around the vessels in
the pia matter that accompany them as they penetrate into the
cord.These extensions of the subarachnoid space is termed as the
Virchow Robin Space.
• Its contents are CSF, nerve roots, blood vessels that suply the spinal cord

36. Subdural space
• The arachnoid is in close contact with the dural
sheath & is separated from it by a thin film of serous
fluid.
• Accidental placement of a catheter during epidural
anaesthesia and subsequent injection of local
anesthetic results in patchy anesthesia which is often
unilateral and extensive

37. Epidural space
• It is a space in the spinal canal that is occupied by dura and its
contents
• It Extends from the foramen magnum to end by the fusion of
its lining membranes at the sacrococcygeal membrane.
• It contains fat, vessels , nerve and lymphatics.
• Cranial epidural space is entirely empty.
• The distance from the skin to the lumbar epidural space in the
midline is on average about 5 cm.

38. Cerebrospinal fluid (CSF)
• The CSF is the clear
watery fluid contained
within the cerebral
ventricles and the
subarachnoid space.
• The total volume of CSF is
about 100 to 160ml in
adult humans and it is
produced at a rate of 20
to 25ml/hr

39. • CSF is an ultra filtrate formed by active process
from the choroid plexus of the lateral ventricles
• The epidymal cells of pia covering the blood
vessels play the secretary role
• At 600ml of CSF is formed per day

40. • About 20-25 ml of CSF is present in the ventricles
• 90 ml of the CSF in reservoirs in the brain
• 25-30 ml of CSF occupy the sub arachnoid space
• It is produced at a rate of 0.4ml/min
• It is around 25ml/hr

41. • About 4/5th of the fluid is reabsorbed via the
arachnoid villi.
• The remaining 1/5th of the CSF is absorbed via similar
spinal arachnoid villi or escapes along the nerve
sheaths in to the lymphatics.

42. • The specific gravity of CSF is 1.003-1.009
• Its PH is 7.4 - 7.6
• Na - 140-150 meq/L
• Chloride - 120-130 meq/L
• Bicarbonate - 25-30 meq/L
• Proteins – 15-45 mg/dl
• Glucose – 50-80 mg/dl

43. Spinal cord
• The adult spinal cord measures approximately 41 to 48
cm in length.
• Weight of spinal cord is between 24 to 36 gm.
• It is about 1 cm in diameter with cervical and
lumbosacral expansion.
• The spinal cord extends caudally from the brain. Its upper end
is continuous with the brain (medulla oblongata).

44. • In the newborn the spinal cord terminates in the lower border of 3rd
lumber vertebrae.
• In the adult spinal cord terminates at the disc between 1st and 2nd
lumber vertebrae.
• The spinal cord consists of 31 pairs of spinal nerves
• After L1 the nerve roots course for some distance before exiting the
intervertebral formina forming cauda equina (horse tail)

45. Cauda equina syndrome
• It is a lower motor neuron lesion which occurs due to the damage to
cauda equina
• It is caused due to trauma, tumours and lesions, spinal stenosis and
inflammatory conditions
• Symptoms include weakness of the muscles of the lower
extremities, urinary retention, fecal incontinence, sexual dysfunction
• Treatment of cauda equina syndrome is surgical decompression

46. Structure of spinal cord
• Spinal cord presents an
anterior median fissure and a
shallow posterior median
sulcus from which a glial
posterior median septum
extends half-way into the
substance of the cord.

47. Contd….
In transverse section, the cord comprises a central canal an H-shaped zone of
grey matter(nerve cells) and an outer zone of white matter(nerve fibers).
• The H shaped grey matter is termed as the transverse commisure. Each
limb consists of an short broad anterior column (anterior horn) containing
large motor cells and thin pointed posterior column (posterior horn)
capped by substantia gelatinosa
• the amount of white matter declines progressively from cervical down to
the lumbar region.
• Grey matter is greatly increased in both cervical and lumbar enlargements,
which correspond to the zones of origin of motor nerves to the upper and
lower limbs.

48. • The central canal continues downwards from the 4th
ventricle as a narrow tube lined with ciliated ependymal
cells and contains csf
• It transverses the whole length of the cord, dilates
somewhat within the connus medularis and continues for a
short distance within the filum terminale

49. `
• The tracts that originate from the white matter of the spinal cord can be classified as Descending
tracts
Ascending tracts
• Descending tracts are
1. Lateral cerebrospinal or pyramidal tract
2. Anterior cerebrospinal or uncrossed motor tract
• Ascending tracts are
1. Posterior column
2. Spinothalamic tracts
3. Anterior and posterior spinocerebellar tracts

50. Blood supply of spinal cord

51. • The spinal cord is supplied by the anterior and posterior spinal arteries
which both descend down from the level of the foramen magnum
• The anterior spinal artery is formed at the level of the foramen magnum
by the union of the branch from each vertebral artery.
• It is the largest of the two arteries and it supplies the upper two third of
the spinal cord
• The posterior spinal arteries are paired arteries and they arise from the
posterior inferior cerebellar arteries
• They supply the posterior one third of the cord

52. • The anterior and posterior spinal arteries receive additional blood
supply from the intercoastal arteries in the thorax and lumbar
arteries in the abdomen
• One of these arteries is typically large which is the artery of
Adamakiewicz or arteria radicularis magna arising from the aorta
• It is typically unilateral and always arises on the left side providing
major blood supply to anterior and lower two third of the spinal
cord

53. Anterior Spinal artery syndrome
• Ischemia or infarction occurs in the spinal cord in the distribution of
the anterior spinal artery which supplies the anterior two third of
the spinal cord
• It s usually associated with atherosclerosis of the aorta
• It causes quadriparesis and impaired pain and temperature
sensation
• Complete motor paralysis below the level of lesion due to the
interruption of the corticospinal tract and loss of pain and
temperature below the level of the lesion

55. • The venous drianage comprises a plexus of
anterior and posterior spinal veins that drain
along the nerve roots through the intervertebral
foramina into the segmental veins azygos veins in
the thorax and lumbar veins in the abdomen and
lateral sacral veins in the pelvis

56. Spinal nerves
• There are 8 cervical nerves(C), 12 thoracic(T), 5 lumbar (L), 5
sacral (S), and 1 coccygeal .
• Each is formed by the fusion of an anterior & posterior
spinal root.
• Each pair of spinal nerves passes through a pair of
intervertebral foramina.

57. Layers of spinal nerve
• A series of connective tissue layer surrounds each
spinal nerve.
• Epineurium-outermost layer, consists of a dense
network of collagen fibers.
• Perineurium-extend inward from the epineurium,
dividing the nerve into a series of compartments.
• Endoneurium-delicate connective tissue fibers.

58. • The 31 pairs of spinal nerves each of them are composed
of anterior motor root and a posterior sensory root
• These nerve roots are compose of multiple rootlets
• The portion of the spinal cord that give rise to all of the
rootlets of a single spinal nerve is called as cord segment
• The skin area innervated by the given spinal nerve and its
corresponding cord segment is called a dermatome

60. SPINAL ANAESTHESIA
• Spinal anaesthesia is the regional anaesthesia obtained
by blocking the nerve roots in the subarachnoid space
• The spinal subarachnoid space extends from foramen
magnum to s2 in adults and s3 in children

61. HISTORY
• Corning accidentally administered cocaine intrathecally in order to
insert a catheter into the urethra in 1885
• The first spinal anaesthesia in humans was given by Beir from
Germany in 1898 using 0.5% cocaine.
• In 1908 Einhorm discovered procaine and synthetised the agent
• In 1905 Pitkin popularized the method of introducing the agents
intrathecally

62. STRUCTURES PIERCED
• The spinal needle is passed
through the following
structure…
1. Skin
2. Subcutaneous tissue
3. Supraspinous ligament
4. Interspinous ligament
5. Ligamentum flavum
6. duramater

63. Physiological responses on CVS
• Hypotension
• Symphathetic denervation
• Loss of vasomotor tone
• Arterial and venous dilation
• Decreased periperal vascular resistance and
peripheral pooling of blood
• Decreased venous return to heart and hence
hypotension

64. • Relaxation of the skeletal muscles of the leg
causes pooling of the blood and decreased
venous return to heart which results in
hypotension
• There occurs blockage of the cardio accelerator
fibres located in T1 to T4 and hence it causes
bradycardia and hypotension

65. Respiratory system
• There is a little effect on pulmonary function in patient
without pre-existing lung disease.
• Patient with severe chronic lung disease mainly rely upon
intercostals and abdominal muscles for respiration
• This causes relaxation of these muscles and thus causes
decrease in expiration and also associate with decreased
clearance of the tracheo bronchial secretions

66. AFFECTIVE DYSPNEA
• With the blockade of the sensory input patient may
complain of difficulty in breathing
• The mechanism is described as an inappropriate response
to the given muscular effort
• The patient believes that he/she is not exerting efforts
suficient to maintain breathing
• It is managed by asking the patient to take deep breaths,
providing supplementary oxygen

67. GASTRO INTESTINAL SYSTEM
• The gastrointestinal effect due to sympathetic blockade.
• The abdominal organ derive there sympathetic innervation from T6-L2.
• Blockade of these fibers result in unopposed parasympathetic activity by
vagus nerve.
• It increases the contractility of the gut with normal peristalsis and relaxed
sphincters
• Nausea is common complication of spinal and epidural.
• Shivering is commonly observed during spinal anaesthesia due to
decrease in core temperature which is the main cause of hypothermia
during spinal