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Principles 2 > Neuraxial Overview/Anatomy > Flashcards

Neuraxial Overview/Anatomy Flashcards

1
Q

How many bones are in the spinal column (in each section)?

A

33 total
-7 Cervical
-12 Thoracic
-5 Lumbar
-5 Sacral (fused)
-4 Coccygeal

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2
Q

Describe how the angle of the spinous process changes as you move from cervical/thoracic down to lumbar.

A

-Cervical & Thoracic Spinous Processes point caudal
-Lumbar spinous processes point more posteriorly

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3
Q

What type of joints are the 2 facet joints between each vertebrae?

A

Synovial (movement)

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4
Q

How many pairs of spinal nerves are there?

A

31
-Mixed nerves: Motor, sensory, and ANS nerve fibers

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5
Q

Which vertebrae form the Atlanto-Axial Joint?

A

-C1 (Atlas)
-C2 (Axis)

Allow for side to side movement

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6
Q

How do spinal nerves exit the spinal column?

A

Via intervertebral foramina and sacral foramen.

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7
Q

When does the spinal cord stop in adults?

A

-L1
-10% of people at L2 (1% of the population it extends to L2-L3)

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8
Q

When does the spinal cord stop in a child/infant?

A

L3

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9
Q

What is the Conus Medullaris?

A

Where the spinal cord tapers to an end. This gives off large rootlets that are free flowing in CSF (Cauda Equina)

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10
Q

What does the Cauda Equina terminate into?

A

The Filum Terminale, which extends down and anchors lower sacrum.

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11
Q

What are the Bulbous Portions of the Spinal Cord?

A

-Consist of more gray matter.
-Cervical enlargement: C5-T1, anterior motor, upper limb muscles
-Lumbar enlargement: L2-S3, lower limb muscles

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12
Q

What is Pia Mater?

A

Thin, delicate vascular membrane that covers the spinal cord and as far laterally as the intervertebral foramen.
-Terminates inferiorly as the filum terminale
-Has projections that help connect it to Arachnoid Mater as well as Dura Mater.

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13
Q

What is between the Pia Mater and Arachnoid Mater?

A

CSF

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14
Q

What is Arachnoid Mater?

A

Non-vascular, delicate, impermeable membrane.
-Separated from the Pia Mater by the Subarachnoid space (filled with CSF)
-Continuous throughout the brain, cord, and ends in the Filum Terminale

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15
Q

What is Dura Mater?

A

A dense, fibrous sheath that encloses the spinal cord and extends throughout the brain and ends at the Filum Terminale.
-Thickest of the meninges
-Overlies the brainstem
-Covers the outer periosteal layer (cranium) and the Meningeal layer
-Forms a fold called the Falx Cerebri that separates the Cerebral Hemispheres
-Covers the nerve roots
-Is continuous with the connective tissue surrounding each spinal nerve (epineurium) as it goes through the intervertebral foramen.

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16
Q

When your spinal needle penetrates the _____, you will feel a distinct pop!

A

Dura

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17
Q

What separates the inner surface of the Dura and the Arachnoid Space?

A

Subdural Space (potential space)

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18
Q

What occurs if you inject anesthesia within the Subdural Space?

A

-Delayed Block (10-25 minutes)
-Very Dangerous High Block!!!

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19
Q

The lateral gray horn of T1-L2 contains Corticospinal Tracts for what motor neurons?

A

Sympathetic Motor Neurons (SNS)

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20
Q

The lateral gray horn of S2-S4 contains Corticospinal Tracts for what neurons?

A

Parasympathetic - pre & post ganglionic, splenic, descending colon

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21
Q

Where are Cranial Parasympathetic nerves derived from?

A

Fibers of the Vagus Nerve
-This is important because the Cranial parasympathetic fibers are outside of a spinal and will not be affected by it.

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22
Q

Why is it important that the Cranial Parasympathetic nerves are derived from fibers of the Vagus Nerve?

A

-Vagus parasympathetic nerve fibers lie outside of the Subarachnoid space
-They are little affected by the Spinal or Epidural anesthesia.
-Cranial PNS fibers enter the abdomen with Vagus nerve.
-Ex: Retractor on Mesentery during surgery - pt can have vagal response (N/V, bradycardia, hypotension, pain).

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23
Q

What can you do to combat the vagal response from stimulation of the mesentery during surgery?

A

Surgeon can block the Vagus Nerve as it enters the abdomen, or can add GETA.

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24
Q

What are the 4 things (nuclei?) contained in the Posterior Gray Column?

A

1) Substantia Gelatinosa
2) Nucleus Proprius
3) Nucelus Dorsalis
4) Visceral Afferent Nucleus

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25
Q

What is the Substantia Gelatinosa?

A

-Where afferent nerves from the dorsal roots (pain, temperature, and crude touch via the Spinothalamic tract) synapse
-Contains Opioid receptors

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26
Q

What do neuraxial opioids do?

A

-Inhibit the release of excitatory neurotransmitters (Substance P, Glutamate)
-Inhibit afferent neural transmission to the brain from peripheral nerves

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27
Q

What is the Nucleus Proprius?

A

Ascending pathways for general sensation, pain, temperature, and tactile sensation

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28
Q

What is the Nucleus Dorsalis?

A

Only in the cervical and lower lumbar regions
-Project to Cerebellum for Proprioception

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29
Q

What is the Visceral Afferent Nucleus?

A

Receives visceral information

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30
Q

Where does the action for Neuraxial Blocks primarily occur?

A

On the nerve roots

31
Q

What does the Posterior Primary Rami innervate?

A

-Lateral Branch: motor to Muscle
-Medial Branch: sensation to skin

32
Q

What does the Anterior Primary Rami innervate?

A

-Cervical Plexus (C1-C4)
-Brachial Plexus (C5-T1)
-Lumbosacral Plexus (L1-S4)
-Coccygeal Plexus (S4-S5, 1st Coccygeal)

33
Q

What is the White Matter?

A

The external portion of the cord.
-Axons have myelin (lipid/protein - makes it white)
-Cluster of axons forms the “Tracts”
-Has Ascending Pathways (Sensory) and Descending Pathways (Motor)

34
Q

What are the 3 components of the Ascending Pathways (White Matter- Sensory)?

A

1) Tract of Lissauer
2) Posterior White Columns
3) Ant/Posterior Spinocerebellar Tracts

35
Q

What are the 4 components of the Descending Pathways (White Matter- Motor)?

A

1) Corticospinal Tracts
2) Reticulospinal Tracts
3) Vestibulospinal Tracts
4) Rubrospinal Tracts

36
Q

What is the Tract of Lissauer?

A

-Part of the pain pathway
-Have sensation, then jump 1-2 vertebral levels, then cross at the spinothalamic tract and then enter the posterior gray horn

37
Q

What are the Posterior White Columns?

A

-Fascicularis Gracilis (Legs) and Fascicularis Cuneatus (arms)
-Touch, discriminate touch, vibration, conscious muscle joint sense, proprioception

38
Q

What is the function of the Ant/Posterior Spinocerebellar Tracts?

A

Carries proprioception info to the Cerebellum

39
Q

What are the Corticospinal Tracts?

A

-Lateral and Anterior
-Gross motor movement
-Fine motor, voluntary

40
Q

What are the Reticulospinal Tracts?

A

-Awake and voluntary movement
-Reflexes
-Works by getting constant stimulation from body. When you block afferent impulses, they have less stimulation, so patient gets sleepy/somnolent.

41
Q

What are the Vestibulospinal Tracts?

A

-Balance traverses the inner ear and cerebellum via this tract
-Facilitates extensor muscles
-Inhibits flexor muscles to maintain balance

42
Q

What are the Rubrospinal Tracts?

A

Alpha motor neurons that facilitate flexor muscles

43
Q

How does blockade of dorsal roots compare to blockade of ventral root?

A

-Dorsal: Somatic/visceral, sensory
-Ventral: Autonomic, Motor

44
Q

What are the 3 ways the Spinal Cord receives blood supply?

A

1) Posterior Spinal Arteries
2) Anterior Spinal Artery (singular)
3) Artery of Adamkiewicz (Arteria radicularis magna)

45
Q

What are the Posterior Spinal Arteries?

A

-Derived from the cerebral arterial system
-Rich supply of collateral flow from the Subclavian, Intercostal Lumbar, and Sacral arteries
-Supplies Posterior 1/3 of the cord; has contributions from radicular arteries
-Descend on each side of the cord and increase in blood supply as they go down from radicular arteries that feed into it

46
Q

What is the Anterior Spinal Artery?

A

-A single artery that is derived from both Vertebral arteries and transverses down the midline of the cord in the Anterior Median Fissure
-Has contributions from radicular arteries
-As it moves down, gets smaller
-Becomes extremely small in the mid to lower thoracic region
-Can be problematic if radicular arteries are occluded (feeder arteries)
-Supplies 2/3 of the Anterior Cord

47
Q

What is the Artery of Adamkiewicz (Arteria Radicularis Magna)?

A

The most important radicular artery from a single segmental branch of the aorta.
-Supplies nearly all of the flow to the lower thoracic and lumbar segments (Lower 1/3 of Anterior cord)
-Injury to this artery = increased risk for ischemia.

48
Q

What causes Anterior Spinal Artery Syndrome?

A

Damage, ischemia, hypoperfusion, or occlusion to the Artery of Adamkiewicz.

49
Q

What are the S/Sx of Anterior Spinal Artery Syndrome?

A

-Flaccid paralysis
-Variable loss of sensation of pain and temperature at and below the level of injury.
-Preservation of proprioception and light touch

50
Q

When does Anterior Spinal Artery Syndrome occur?

A

-Most common in Aortic Surgery with prolonged cross clamping or direct injury
-Risk factors: Atherosclerosis, prolonged hypotension, embolic issues.

51
Q

Motor paralysis is due to disruption of what?

A

Motor paralysis = disruption of cord at the Corticospinal Tract. (!)

52
Q

Loss of pain and temp at and below injury is due to the disruption of what?

A

Loss of pain and temp at and below injury = disruption of spinothalamic tract.

53
Q

Why are proprioception and vibratory sensation retained with ASA syndrome?

A

Intact dorsal columns

54
Q

What is unique to a Partial Complex injury (Anterior Spinal Artery Syndrome)?

A

-Posterior cord can remain intact
-Sensory fascicularis gracilis intact as well as proprioception

55
Q

What is the Anterior Longitudinal Ligament (ALL)?

A

-A continuous band running down the anterior surface of the vertebral column from the skull to sacrum.
-Holds the vertebrae together firmly, while allowing some movement
-Tapers inferior to superior.
-More likely to have a cervical disc herniation ANTERIORLY (ACDF)

56
Q

What is the Posterior Longitudinal Ligament (PLL)?

A

-A continuous band running down the posterior surface of the vertebral column from the skull to sacrum.
-Holds the vertebrae together firmly, while allowing some movement
-Tapers superior to inferior.
-More likely to have posterior lumbar herniation (Lumbar Lami & Discectomy)

57
Q

What is the Supraspinous Ligament?

A

The most superificial
-Runs between adjacent spines
-Thickest/broadest in Lumbar Region

58
Q

What is the Interspinous Ligament?

A

-Thin ligament
-Connects the adjacent spines
-Fills in between the Ligamentum Flavum and the Supraspinous Ligaments

59
Q

What is the Ligamentum Flavum?

A

-Elastic fibers and membranous material
-Thinnest in cervical region
-Thickest in lumbar region
-Attaches to the anterior and inferior aspect of the Lamina below
-Blends laterally with the joint capsule between the articular processes and fuses posteriorly with the interspinous ligament.
-Does contain small vessels from the vertebral plexuses (can have blood tinge in syringe)
-Normally lies 3-4 cm from the spinous process in the lumbar region

60
Q

Why do we care that the Ligamentum Flavum is two halves that are fused in the middle?

A

-We rely on the LOR technique, and most epidurals are done medially
-In very rare cases, the ligament does not fuse midline (usually occurs at L1-L2)

61
Q

What is important to know with NA anesthesia and the elderly?

A

-Ligamentum Flavum can become calcified
-Disc height may diminish (decreasing interspace)

62
Q

Where is the Epidural Space located?

A

Between the periosteal lining of the canal and the dura.
-Extends from the base of the skull to the level of the sacral hiatus (S4)

63
Q

What are the borders of the Epidural Space?

A

Anterior: Posterior Longitudinal Ligament (PLL)

Posterior: Ligamentum Flavum & Vertebral Pedicles

Lateral: Intervertebral Foramen

Runs from the Foramen Magnum to the Sacral Hiatus (last sacral opening)

64
Q

What is the usual distance of Ligamentum Flavum to Dura?

A

-Smallest where cord is present (Upper lumbar, thoracic, and cervical). Around 3-4 mm
-After cord ends (L2), can be 5-7 mm

65
Q

What is the normal distance from skin to epidural?

A

Usually 4-5 cm
-Can be 2-9 cm depending on patient size

66
Q

What is contained in the Epidural Space?

A

-Fatty tissue with bands of connective tissue that may hold the fatty globules together (this can divert catheter direction or obstruct flow of LA)

67
Q

What is the pressure in the Epidural Space?

A

Slightly negative pressure: -1 to -7 cmH2O (except in the sacral area)

68
Q

What is the widest and narrowest part of the Epidural Space?

A

-Widest: L2 (5-6 mm)
-Narrowest: C5 (1-1.5 mm)

69
Q

Where is the Subarachnoid Space (Intrathecal Space) located?

A

Between the Pia Mater and the Arachnoid Mater

70
Q

Where is CSF produced?

A

Choroid Plexus in the ventricles in the brain (2 lateral ventricles & 3rd ventricle)

71
Q

Where does CSF get absorbed?

A

Arachnoid Villi

72
Q

How much CSF is produced per day?

A

21 mL/hour or 500 mL/day
-150 mL present at any given time, with 30-80 mL of that in the spinal subarachnoid space

73
Q

What is the specific gravity of CSF?

A

1.003 - 1.009
-Isobaric
-Contains trace amounts of glucose and protein

Principles 2 (45 decks)

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