ANATOMY OF SPINAL CORD AND VERTEBRAL COLOUMN ,.pptx

Explains the basic anatomy of spinal cord

1. ANATOMY OF SPINAL CORD AND VERTEBRAL COLOUMN,CSF PHYSIOLOGY PRESENTOR :DR.THANMAYA J MODERATOR : DR.PRIYA C

2. VERTEBRAL COLUMN -EMBYOLOGY -ANATOMY SPINAL CORD -DEVELOPMENTAL ANATOMY -CROSS SECTION OF SPINAL CORD -SPINAL TRACTS -MENINGES -BLOOD SUPPLY OF SPINE CSF PHYSIOLOGY OBJECTIVES

3. EMBRYOLOGY OF VERTEBRAL COLUMN Vertebra develops from 3 primary ossification centre -2 lateral for arch -1 central for the body Ossification granules - 8 th month of embryonic life Transverse processes later project They develop in 2 directions -Anterior and posterior

4. At 16 th year of life -5 secondary centres of ossification appears 1-tip of spinous process 1-tip of each transverse process 1 –tip each for upper and lower surface of the body of vertebrae

5. Anatomy of vertebral column The vertebral arch, spinous process, pedicles, laminae form the posterior elements of the vertebra. The vertebral body forms the anterior. 7 Processes or projection - 3 Muscular process [2 Transverse +1Spinous process] - 2 Articular process [2 upper +2 lower]

6. Vertebrae differ in shape and size at the various levels. The first cervical vertebra, the atlas , lacks a body and has unique articulations with the base of the skull and the second vertebra. The second vertebra, called the axis , consequently has atypical articulating surfaces. All 12 thoracic vertebrae articulate with their corresponding rib.

7. In surgical and obstetric patients, neuraxial block is usually accomplished without the aid of imaging. Commonly identified landmarks include the - C7 spinous process (vertebra prominens ), - 12 TH rib - The iliac crest - the line between the iliac crests ( Tuffier line ) to identify the L4–L5 interspace

8. The vertebrae are joined together -anteriorly by the fibrocartilaginous joints with the central disks containing the nucleus pulposus - posteriorly by the zygapophyseal (facet) joints . The thoracic spinous process is angulated steeply caudad horizontal angulation of the lumbar spinous process.

9. ANATOMY OF LIGAMENTS Ligamentous elements provide structural support, and, together with supporting muscles, help to maintain the unique shape. Ventrally - the vertebral bodies and intervertebral disks are connected and supported by the anterior and posterior longitudinal ligaments

10. Dorsally -the ligamentum flavum, interspinous ligament, and supraspinous ligament provide additional stability.

11. Subarachnoid puncture below L1 in an adult ( L3 in a child) usually avoids potential needle trauma to the cord; damage to the cauda equina is unlikely, as these nerve roots float in the dural sac below L1 and tend to be pushed away (rather than pierced) by an advancing needle

12. supraspinous ligament – Strong ,thick ,fibrous heavy band that runs along the tips of the spinous processes, becomes thinner in the lumbar region. Connects apices of spines from C 7 vertebra to sacrum continues as the ligamentum nuchae above T7 and attaches to the occipital external protuberance at the base of the skull

13. Interspinous ligament – A thin fibrous tissue narrow web of tissue that attaches between spinous processes It may contain slit-like, fat-filled cavities that can create a false loss of resistance during attempts to identify the epidural space Anteriorly it fuses with the ligamentum flavum Posteriorly with the supraspinous ligament

14. ligamentum flavum – Consists of yellow elastic tissue The fibres are perpendicular in direction They extend from lamina-Anterior inferior surface of upper lamina downward to anterior superior surface of lower lamina . This halves fuses with thin central midline

15. When attempting to locate the epidural space, try to appreciate the “ snap ” of the supraspinous ligament the “ mushy ” intraspinous ligament the “ gritty ” ligamentum flavum .

16. 1. The lateral intervertebral gap . superior and inferior (the deeper) notches form a large lateral opening named the intervertebral foramen. The spinal nerves emerge through this gap.

17. 2. The posterior interlaminar gap . This is the region for the conventional technique of spinal puncture, subarachnoid or epidural. normal or extended position, the interlaminar foramen is small and triangular . During flexion , the inferior articular process slide upward and enlarge the foramen into a diamond-shaped opening.

18. ANATOMY OF INTERVERTEBRAL DISC Fibro cartilaginous structure Contributes 25% of the height of spinal column. Function of shock absorption, transmitting compressive loads between vertebral bodies.. Composed of the central nucleus pulposus (NP), the peripheral annulus fibrosus (AF) and the end plates (EP ). The end plate is a bilayer of cartilage that separate the IVD from the vertebral body(VB) and serves as growth plate for the VB.

19. SPINAL CORD

20. Spinal cord is continuous with the brainstem proximally and terminates distally in the conus medullaris as the: filum terminale - fibrous extension cauda equina - neural extension This distal termination varies: - L3 in infants - the lower border of L1 in adults -because of differential growth rates between the bony vertebral canal and the central nervous system.

21. DEVELEPMENTAL ANATOMY OF THE SPINAL CORD EARLY FETAL LIFE –Spinal cord is as long as the vertebral column,with meningeal coverings ,fills the canal 3 MONTHS OF FETAL LIFE -Tip of the cord is located at the 2 nd coccygeal vertebrae 6 MONTHS OF FETAL LIFE -Conus is at the level of the 1st sacral vertebra AT BIRTH - Tip of the spinal cord lies at the level of the lower border of the 3 rd lumbar vertebra and dural sac at the S3 AT 1YEAR OF AGE –Conus medullaris at the lower border of 2 nd lumbar vertebra and dural sac ends at S2

22. AT 12-16 YEARS OF AGE –Adult relations attained -Spinal cord is located at the lower border of 1 st lumbar vertebra[50 percent], L2 [40 percent], T12 [10 percent] Average length of the spinal cord in adult - male : 45cm - female : 42cm Average weight is approximately 30 g

23. CROSS SECTION OF SPINAL CORD The spinal cord is incompletely divided into two equal parts, - anteriorly by a short, shallow median fissure - posteriorly by a deep narrow septum, the posterior median sulcus. Composed of grey matter in the center surrounded by white matter supported by neuroglia .

24. Commissures : connections between left and right halves - Grey with central canal in the center - White commissure

25. Grey matter ● The arrangement of grey matter resembles the shape of the letter H having two posterior, two anterior and two lateral horns/columns. ● Consists of nerve cell bodies and their processes, neuroglia , and blood vessels ● The nerve cells are multipolar and are of three main categories: Sensory neurons . Lower motor neurons Interneurons [ connector neurons]

26. White matter The white matter of the spinal cord is formed by the axons that make up their respective ascending and descending tracts. This area of the spinal cord is divided into - dorsal - lateral - ventral columns . The dorsal column of the spinal cord is composed of spinothalamic tracts that transmit touch and pain impulses to the brain.

27. SPINAL NERVES There are 31 pairs of spinal nerves, - 8 pair cervical -12 pair thoracic -5 pair lumbar -5 pair sacral -1 pair coccygeal each with an anterior motor root and a posterior sensory root . These nerve roots arise from individual spinal cord segments. Each posterior sensory root innervates a specific dermatome .

28. The sympathetic nervous system arises from the intermediolateral grey matter of the T1 to L2 spinal cord segments. This grey matter contains the cell bodies of the preganglionic sympathetic neurons, which travel with the corresponding spinal nerve through the intervertebral foramen. They then diverge and join the sympathetic chain ganglia.

29. In 31 pairs of spinal nerve, - first pair exit vertebral column between skull and atlas - last four pair exit via the sacral foramina - others exit through intervertebral foramina . Each spinal nerve arises as rootlets which then combine to form dorsal purely sensory & ventral purely motor Roots. Two roots merge laterally and form the spinal nerve.

30. Dorsal root has a ganglion (dorsal root/sensory ganglion) that contains the cell bodies of the sensory neurons. Each spinal nerve then divides into a MIXED smaller dorsal and a larger ventral Ramus.

31. Branches of Spinal Nerves Dorsal Rami : innervate Deep muscles of the trunk responsible for movements of the vertebral column and Skin near the midline of the back. Ventral Rami : In the thoracic region form Intercostal nerves that innervate the intercostal muscles and the skin over the thorax Remaining ventral rami form five plexuses: C1 - C4 = Cervical plexus . C5 - T1 = Brachial plexus. L1 - L4 = Lumbar plexus . L4 - S4 = Sacral plexus . S5 & Co = Coccygeal plexus . Communicating Rami: Is connection between spinal nerves and sympathetic chain of ganglia

32. The spinal nerves and their corresponding dermatomes are named for the foramina through which they exit the vertebral column. In the cervical region , spinal nerves are named after the lower vertebrae (i.e., C5 exits between C4 and C5). Elsewhere, the roots are named by the upper vertebrae (L2 emerges between L2 and L3).

33. Since the vertebral column is longer than the spinal cord, the thoracic, lumbar, and sacral nerve roots traverse progressively greater distances from their originating spinal cord segment to their exiting foramina. The lumbar and sacral spinal nerves that extend beyond the tip of the cord are called the cauda equina . These nerve roots, covered only by pia mater , may be more susceptible to chemical injury than more proximal roots.

34. MENINGES OF SPINAL CORD Spinal cord has three covering membranes: - the dura -arachnoid - pia mater . These membranes concentrically divide the vertebral canal into three distinct compartments: Epidural Subdural Subarachnoid spaces .

35. DURAL LAYER The dura mater (hard mother) is the thickest, outermost meningeal layer. It is 270 to 280 μm thick and consists mostly of collagen fibers arranged in about 80 layers of very fine lamellae . The external (epidural surface) contains bands of collagen fibers running in different directions. The dura also contains thick elastic fibers and fine granular material. The inner (subarachnoid) surface includes fine fibers that fuse with the arachnoid mater.

36. The dura is a continuation of the spinal meninges, extending from the foramen magnum to approximately S2 It extends laterally with individual nerve roots and fuses with the epineurium near the intervertebral foramina. spreads distally to cover the filum terminale . In children, the dural sac terminates lower In adults, the sac termination can be as high as L5

37. ARACHNOID MATTER The arachnoid mater (spider mother) lies within the dura. It has two portions. A compact laminar layer of flattened epithelial-like cells that are tightly connected to one another covers the inner surface of the dura. A trabecular web-like portion extends to the pia mater .Because of this cellular architecture, the arachnoid, not the dura, hinders drug movement through meninges. The low permeability of the arachnoid mater keeps the CSF in the subarachnoid, not the subdural space. Specialized intercellular junctions within the internal portion of the arachnoid mater explain its selective permeability .

38. PIA MATTER The innermost layer of the spinal meninges is the pia mater (soft mother). The pia consists of flat overlapping cells that coat the spinal cord and nerve roots. The pial cells contain numerous fenestrations along the lumbar spinal cord and nerve roots . Any role these fenestrations might play in the action of subarachnoid or epidural medications is speculative.

39. Epidural space The epidural space is bound anteriorly by the posterior longitudinal ligament Laterally by the pedicles and intervertebral foramina Posteriorly by the ligamentum flavum . Contents : 1.nerve roots and fat 2.areolar tissue 3.lymphatics 4.blood vessels including Batson venous plexus

40. The remainder of the space consists of discontinuous, fat-filled pockets that open readily upon injection of air or liquid. The cervical level contains no epidural fat. In the lumbar region , fat in the anterior and posterior aspects of the epidural space forms multiple, metameric, discrete collections . This fat may play an important role in the kinetics of epidural medications .

41. Epidural veins are located mostly in the anterior epidural space. The intervertebral foramina allow transmission of intra-abdominal pressure into the epidural space. Conditions that increase intra-abdominal pressure (i.e., pregnancy) can cause engorgement of epidural veins, leading to more frequent venous cannulation and possibly enhancing the spread of injected medications .

42. Subdural space Potential space between the dura and the arachnoid and contains a serous fluid. Formed by flat neuroepithelial cells . These cells are in close contact with the inner dural layers

43. When needle is inserted to subarachnoid space,following structures are traversed Skin and subcutaneous tissue Supraspinous ligaments Interspinous ligaments ligamentum flavum Areolar tissue or epidural space Dura spinalis matter

44. CURVES OF THE SPINE When patient is in supine position High point of spinal curve – L3 Low point of spinal curve – T5 Denser fluid pool in L3 than csf flow and tend to pool in T5 and in lower lumbar area Lighter solution pool in L3

45. Abnormal curvature

46. BLOOD SUPPLY Arterial supply One anterior spinal artery (originating from the vertebral artery )-supply major portion of anterior 2/3 rd of spinal cord Two posterior spinal arteries (originating from the posterior inferior cerebellar artery )-supply posterior 1/3 rd of spinal cord in front of dorsal roots

47. The segmental spinal arteries (originating from the intercostal and lumbar arteries). The spinal arteries enter the spinal canal at each intervertebral foramen and give off branches to both the nerve roots and the medullary branches to the spinal cord

48. Artery of Adamkiewicz Known as the arteria radicularis magna One of the larger anterior radicular artery- Major segmental artery, variably entering between T7 and L4 on the left 79% arise from Left T8and L1, 30% from right Branch – anterior spinal artery and another branch anastomose with the division of posterior spinal artery

49. Arterial supply is delicate system – vulnerable to minor trauma and to vasoconstrictor drugs Anterior spinal artery syndrome – lower limb paralysis without loss of posterior coloumn sensation [ touch,position,vibratory,joint senses] Cauda equina syndrome - characterized by loss of urinary and fecal continence denoted by sphincteric disturbances

50. The radicular arteries - are branches of the spinal arteries and run within the vertebral canal and supply the vertebral column. Radicular veins - drain blood from the vertebral venous plexus and eventually drain into the major venous system: - the superior and inferior vena cava - the azygos venous system of the thorax.

51. Venous supply Follows a similar distribution as the spinal arteries. Three longitudinal anterior spinal veins and three posterior spinal veins that communicate with the segmental anterior and posterior radicular veins draining into the internal vertebral venous plexus in the medial and lateral components of the epidural space. There are no veins in the posterior epidural space except those caudal to the L5-S1 disk.

52. SPINAL CORD BLOOD FLOW Mimics brain blood flow in perfusion pressure - 60 to 120 mmHG The average flow is about 60ml/gm/min at 60 mmHG Difference in flow between gray and white matter exist -Gray matter - 40ml/100g/min [half of cerebral gray matter] - White matter - 8-12ml/100g/min [one third of cerebral white matter] Lumbar and cervical regions have higher blood flow than thoracic

53. Regulation of spinal cord blood flow Spinal cord perfusion pressure- MAP-CSFP: 60-120mmhg In this range of this arterial pressure autoregulation of circulation and constancy of blood flow maintained Within this range intrinsic factors regulate and outside the range perfusion pressure gradient follows Intrinsic Factors -co2,Paco2,Po2 and pH ,cord temperature Hypoxia ,hypercarbia –increases spinal cord blood flow Hypocarbia –reduces spinal cord blood flow

54. CEREBRO SPINAL FLUID The cerebrospinal fluid (CSF) resides in the space between the pia mater and the arachnoid mater. Total volume in adults - 120ml to 150ml -20 to 25ml – in ventricles -30 to 90 ml –large cisternal reservoirs [ 25 to 30ml occupy spinal subarachnoid space ] Approximately 500 mL of CSF is formed daily by the choroid plexuses of the cerebral ventricles, with 30 to 80 mL occupying the subarachnoid space from T11 to T12 downward. Lumbosacral CSF has a constant pressure of approximately 15 cm H2O

55. Lumbosacral CSF has a constant pressure of approximately 15 cm H2O, but its volume varies by patient, because of differences in body habitus and weight. CSF volume accounts for 80% of the variability in peak block height and regression of sensory and motor blockade. The volume of CSF correlate with body weight -less CSF in subjects with high body mass index [BMI]

56. Formation of cerebrospinal fluid Cerebrospinal fluid is formed by a process of ultra filtration through the choroid plexus The plexus consists of network of small blood vessels surrounded by the pia matter which projects into cerebral ventricles The ependymal cells of pia matter cover the vessels and play the secretory role. About 0.6ml/min or 25ml/hr[600ml/day] formed in adults There is replacement of total spinal fluid under ordinary normal physiological circumstances over 6 hrs A moderate loss of fluid of 20-30m l will be replaced in 1 hr if leakage doesnot occur

57. Control of production Secretion of CSF is under sympathetic control . Histologically the epithelium and vessels of choroid plexus receive noradrenergic innervation from sympathetic chain [ through superior cervical ganglia] Stimulation of superior cervical ganglia increases the production and fluid pressure . This secretary innervation is mediated by b-adrenergic receptors ,located on cell membranes and coupled with adenylcyclase When neurotransmitters or beta agonists are present ,the receptor binding leads to intracellular synthesis of cyclic AMP leading extensive stimulation of fluid production .

58. Active secretion of spinal fluid Through electrochemical work there occurs active secretion of CSF High concentration of carbonic anhydrase in choroid plexus is essential for active secretion Administration of acetazolamide which inhibit carbonic anhydrase ,will inhibit the formation and rate of production of csf Through electrochemical work there occurs active secretion of CSF High concentration of carbonic anhydrase in choroid plexus is essential for active secretion Administration of acetazolamide which inhibit carbonic anhydrase ,will inhibit the formation and rate of production of csf

59. Secretion and absorption In children [4-12years]-formation of csf is slower rate than adults The mean rate of formation is set at 0.35ml/min Absorption of csf is through cerebral arachnoid villi ,which penetrate into venous sinuses . The principle drainage route is superior saggital sinus The force required for absorption is provided by hydrostatic pressure [intraventricular pressure – saggital sinus blood pressure ] In children [4-12years]-formation of csf is slower rate than adults The mean rate of formation is set at 0.35ml/min Absorption of csf is through cerebral arachnoid villi ,which penetrate into venous sinuses . The principle drainage route is superior saggital sinus The force required for absorption is provided by hydrostatic pressure [intraventricular pressure – saggital sinus blood pressure ]

60. Effects of induction of drugs on CSF At low doses of thiopental,etomidate ,midazolam csf formation is not different ,but at higher doses of each drug the rate of fluid formation reduced Thiopental –reabsorption is increased at lower dose but reduced at higher doses Midazolam –reabsorption elevated at both low and high doses Etomidate -at low doses –normal rate of reabsorption but reduced highest dose In general – csf volume and pressure increases with doses of thiopental or midazolam

61. Composition of cerebrospinal fluid Composition/Characteristic Normal range Protein 15-45mg/dl Glucose 50-80mg/dl Non protein nitrogen 20-30mg/dl Chloride 120-130mEq/L Sodium 140-150mEq/L Bicarbonate 25-30mEq/L pH 7.4-7.6 Specific gravity 1.003-1.009 Volume 130-150ml Volume of fluid about cord 20ml Average pressure 110mmwater

62. DENSITY OF CSF Density of any solution is the weight in grams of 1 ml of the solution at a standard temperature. Density varies inversely with temperature. Specific gravity is the density of a solutions compared in a ratio with the density of water. Baricity is a ratio comparing the density of one solution to another. Density of normal human. CSF at 370C is 1.0001 to 1.00055 Specific gravity of spinal fluid 1.003 to 1.008

63. ISOBARIC SOLUTIONS 1)Densities between 0.9998 and 1.0008 ISOBARIC SOLUTIONS Densities between 0.9998 and 1.00082 Solutions are mixed with physiological saline Solutions with out added glucose Bupivacaine, ropivacaine, levobupivacaine Spread not influenced by position 2) Solutions are mixed with physiological saline 3) Solutions with out added glucose 4) Bupivacaine, ropivacaine, levobupivacaine

64. HYPOBARIC SOLUTIONS . Baricity less than 0.9998 at 370C. Prepared by diluting with distilled water HYPERBARIC SOLUTIONS . Solutions at 370c with baricity greater than 1.0008. Made by addition of 5-9.5% dextrose.

65. Circulation of cerebrospinal fluid

67. ABSORPTION OF CEREBROSPINALFLUID Absorption of CSF in cranial region occurs in supratentorial region through arachnoid villi and Pacchionian bodies or granulations. These granulations are bulges of the arachnoid into and through the meningeal dura into the great venous sinuses.

68. From the spinal dural sac, CSF is absorbed in two ways:. Most passes directly from the -subarachnoid space into venous plexuses of the pial meninges - - Virchow-Robin spaces to parenchymal-capillaries and then pial venules. -The pial veins communicate with the internal vertebral plexus directly or via venous channels in the nerve roots Some passes from the dural sac in the dural sleeves along the course of the spinal nerve roots as they exit through the intervertebral foramina . It passes into paravertebral interstitial space and then to lymphatics

69. Spinal pathway of absorbtion of CSF

70. THANK YOU

71. REFERENCE Millers anesthesia 9 th edition Regional collins Morgan and mikhails clinical anesthesia