Chapter 45 Selective Nerve Root Blocks and Transforaminal Epidural Steroid Injections

Question 1

The pain from “sciatica”

can be caused by

Answer 1

mechanical compression by herniated discs, chemical irritation from ruptured disc, foraminal stenosis secondary to spondylosis, or vascular compromise.

Question 2

the most likely cause of radicular pain is from

Answer 2

chemical inflammation around the nerve root

Question 3

Human discs contain high levels of

Answer 3

phospholipase A2
(PLA 2) along with other inflammatory mediators such as metalloproteases and nitric oxide

Question 4

phospholipase A2 PLA2

Answer 4

the enzyme
responsible for the liberation of arachidonic acid from cell
membranes at the site of inflammation, and levels are increased
in herniated discs relative to normal discs. PLA 2 also acts as a catalyst in generating prostaglandins, leukotrienes, platelet activating factor, and lysophospholipids, all
of which cause inflammation

Question 5

methylprednisolone was applied directly to neural structures.

Answer 5

a reduction of inflammation

Question 6

Corticosteroids suppress inflammation by

Answer 6

The mechanism of action is most likely related to the steroids ability to inhibit phospholipase A2 activity.

Question 7

Steroids may also have a

Answer 7

local anesthetic and antinociceptive effect

Question 8

mainstay of conservative

management of radicular pain

Answer 8

Epidural steroid injections

Question 9

The evolution of the transforaminal approach was based on the idea that

Answer 9

injecting a concentrated steroid around inflamed neural structures will provide better and longer lasting relief of radicular
pain than introducing the same steroids in the dorsal epidural space.

Question 10

radicular pain occurs because of pathology in the

Answer 10

ventral epidural space from disc protrusion, extrusion, leakage of
nucleus pulposus, or mechanical compression. Axial back
and neck pain are more complicated in that it can be caused by both ventral and dorsal elements.

Question 11

Irritation of the posterior longitudinal ligament or internal disc disruption can cause the same type of pain that

Answer 11

muscle strains/ sprains, facet arthropathy, or ligamentum flavum pain.

Question 12

The more cephalad the

injection, the higher the risk for

Answer 12

catastrophic complications such as spinal cord injury or stroke.

Question 13

The cervical level is the most “risky” in that the

Answer 13

vascularity in the foramen is extensive,

and susceptible arteries are in the immediate vicinity of the foramen at the C3–C6 levels.

Question 14

The foramen at the cervical level face slightly

Answer 14

anterior and oblique; thus, the supine or lateral position is optimal.

Question 15

The cervical foramina are bounded

Answer 15

posteriorly by the superior articular process (SAP) of the lower vertebra and anteriorly by the lower end of the upper vertebral body, the uncinate process of the lower vertebra, and the intervertebral disc. Its
roof and floor are formed by the pedicles of consecutive vertebrae.

Question 16

The superior and lower portion of the foramen contains

Answer 16

The superior portion of the foramen contains epiradicular veins and the lower most portion contains the spinal
nerve.

Question 17

Arterial branches arise either from the

Answer 17

vertebral arteries
or the deep or ascending cervical arteries to supply the
nerve roots (radicular arteries) and spinal cord (medullary arteries).

Question 18

at most risk of penetration during a cervical transforaminal epidural
steroid injection (TFESI) or SNRB.

Answer 18

branches off of the cervical arteries

Question 19

At the thoracic level, the foramen faces more

Answer 19

posterior and lateral relative to the cervical level.

Question 20

at risk of penetration at the lower

thoracic levels.

Answer 20

the ribs, pleura, and mediastinum are the surrounding structures along with the radicularis magna

Question 21

The foramina at the lumbar levels face

Answer 21

laterally.

Question 22

Border of foramina at the lumbar levels

Answer 22

The anterior border includes the upper vertebra and intervertebral disc, the posterosuperior and the posteroinferior borders are comprised of the inferior articular process
(IAP) and SAP, respectively, with the pedicles forming the
roof and the floor.

Question 23

main arterial supply to the lower two-thirds of the spinal cord.

Answer 23

artery of Adamkiewicz. It enters the spinal canal anywhere from T7 to L4, usually on the left side between T9 and L1 vertebrae.

Question 24

Trauma to artery of Adamkiewicz

Answer 24

lead to anterior spinal artery syndrome and paraplegia

Question 25

The indications for SNRBs and transforaminal epidural steroid injections are the same and include:

Answer 25

l Radiculitis/radiculopathy l Lumbar disc displacement without myelopathy l Axial pain l Diagnostic for vague symptoms or multilevel pathology l Postlaminectomy with recurrent pain l Spinal/foraminal stenosis

Question 26

Contraindications SNRBs and transforaminal epidural | steroid injections

Answer 26

l Patient refusal l Bleeding disorders l Elevated coagulation studies

Question 27

Equipment and materials for SNRBs and transforaminal epidural steroid injections include the following:

Answer 27

l C-arm fluoroscope (CT also used) and fluoroscopic table l Monitors l 22- or 25-gauge Quincke needle, variable length up to 7 in, depending on patient size l Corticosteroid—methylprednisolone, triamcinolone, betamethasone, dexamethasone l Contrast dye—Omnipaque M-185 or Isovue M-200

Question 28

techniques for SNRB and transforaminal epidural steroid injection are essentially the same except for the final needle location

Answer 28

The final needle position is slightly lateral to the intervertebral foramen for the SNRB, and the tip is guided more toward the center rather than subpedicular and anterior. For the cervical level, the needle is kept more lateral to the foramen to avoid spread of contrast to adjacent levels along with lower volumes of local anesthetic

Question 29

LUMBAR TECHNIQUE

Answer 29

The procedure can be done prone or lateral, most practitioners prefer prone. Fluoroscopy is utilized to determine the correct level of injection and approach. The area is prepped with either chlorohexanol or Betadine and draped in usual sterile fashion.

Question 30

LUMBAR TECHNIQUE | The C-arm is then positioned

Answer 30

obliquely to visualize the foramen optimally, usually 15 to 30 degrees, Scotty dog view, with the transverse process over the vertebral body. A less oblique view can be utilized to keep the needle lateral to the foramen and better target a single nerve

Question 31

Lumbar Techniques | The goal is for the needle to be

Answer 31

coaxial with the C-arm, just under the pedicle and lateral to the pars interarticularis, above the superior articular process inferiorly. This approach avoids the nerve root, and thus avoids periprocedural paresthesias.

Question 32

Lumbar Techniques | An anteroposterior view is obtained with the fluoroscope to determine the

Answer 32

mediolateral location of the needle

Question 33

Lumbar Techniques If the needle tip encounters bony resistance, this is most likely

Answer 33

the pars interarticularis and the needle should be walked just inferior, anterior, and medial past this level.

Question 34

Lumbar technique | Once the needle tip is just under the pedicle medially, the fluoroscope is rotated to the

Answer 34

lateral view and the needle is advanced slowly into the foramen until the tip is in the anterior one-third of the foramen, just under the pedicle

Question 35

Lumbar Techniques The patient may experience a paresthesia, at which point it is best to

Answer 35

slightly withdraw; the paresthesia must disappear prior to injection of contrast. After negative aspiration for blood, 1 to 2 ml of radiographic contrast is injected under live fluoroscopy to confirm anterior epidural spread in the case of the transforaminal injection, or nerve root spread for the SNRB

Question 36

For the L1 and L2 levels, digital subtraction angiography should be utilized in the AP and lateral view to better

Answer 36

detect potential vascular spread and the needle tip should be kept slightly posterior in the foramen to avoid the artery of Adamkiewicz.

Question 37

L5 level presents unique challenges

Answer 37

iliac crest is in the line of the needle and may obstruct its path to the foramen. Normally, this can be avoided by angling the C-arm more cephalad to line up the inferior end plates of the L5 vertebral body.

Question 38

At the L5 level the path | of the needle is

Answer 38

a triangular area formed by the superior articulating process of S1, the inferior border of the transverse process of L5, and the iliac crest. The needle is advanced from a lateral to a medial direction, medial to the iliac crest, until the tip of the needle projects inferior to the pedicle.

Question 39

Patient and C arm position for blockade of the S1 nerve root.

Answer 39

The patient lies prone for blockade of the S1 nerve root. The C-arm is in straight anterior–posterior (AP) projection or with 5 to 10 degrees of ipsilateral lateral angulation

Question 40

blockade of the S1 nerve root

Answer 40

The needle is advanced through the posterior sacral foramen until the first sacral root is encountered.

Question 41

in the lumabr technique, Once the appropriate contrast pattern is seen in the anterior epidural space, an AP image is then obtained to confirm

Answer 41

spread of contrast perineurally and/or epidurally as well as | confirmation that no vascular or intrathecal spread has occurred

Question 42

in the lumbar technique the final target for the SNRB is for the needle

Answer 42

to be extraforaminal whereas with the transforaminal epidural, it is ideal to be in the anterior and superior portion of the foramen

Question 43

in the lumbar technique, Once appropriate spread of contrast is seen in the ventral epidural space without vascular or intrathecal uptake

Answer 43

a mixture of 1 ml of saline (or 1% lidocaine or 0.25% bupivicaine) and either 40 to 80 mg of triamcinolone, 6 mg of betamethasone, or 4 to 8 mg of dexamethasone are injected incrementally

Question 44

THORACIC TECHNIQUE | The C-arm position

Answer 44

The T9 to T12 levels are done similarly to the L1 and L2 levels. The C-arm is not rotated quite as oblique to avoid potential pneumothorax, and the needle is not advanced quite as anterior to avoid the artery of Adamkeiwicz For the T1 to T8 levels, the C-arm should not be rotated more than 15 degrees to avoid pneumothorax, and to maintain better visualization of the foramen.

Question 45

THORACIC TECHNIQUE | patient's position

Answer 45

At these levels, only the prone position is utilized, but theoretically, the lateral position can be used.

Question 46

THORACIC TECHNIQUE

Answer 46

a needle is advanced coaxially with the C-arm of the fluoroscope to the posterior and medial portion of the foramen. Once the needle tip is seen just medial and inferior to the pedicle, real-time fluoroscopy with the injection of 1 to 2 ml of contrast under AP and lateral imaging is utilized to confirm appropriate spread

Question 47

THORACIC TECHNIQUE | substance injected

Answer 47

The substances injected are the same as for the lumbar technique, but, methylprednisolone is not recommended because of its larger particle size

Question 48

CERVICAL TECHNIQUE | patients position

Answer 48

The cervical level is usually approached in the supine position with the head neutral and a shoulder roll in place. A cushion is useful to keep the patient comfortable and to keep the head in place. The head maybe turned for the lower levels if it makes the needle entry easier. For C1 to C4 levels, the lateral position may be ideal, but for C4 to C8, the supine position is better to keep the shoulders out of the way of the image

Question 49

CERVICAL TECHNIQUE | C-arm position

Answer 49

image is now a PA rather than an AP image unless the C-arm is inverted.24 The fluoroscope is rotated oblique ipsilaterally to visualize all of the borders of the foramen.

Question 50

CERVICAL TECHNIQUE | The initial target is the

Answer 50

most posterior and inferior part of the foramen in order to avoid the vertebral artery anteriorly or placing the needle to medially into the spinal canal

Question 51

CERVICAL TECHNIQUE Goal

Answer 51

The goal is to make contact with the superior articular process posteriorly to gauge the medial safety margin. In order to do this, a coaxial view of the needle is crucial. Once the needle contacts the posterior portion of the foramen, the needle can be walked slightly anteriorly into the foramen. The fluoroscope is then rotated back to PA to determine the medial location of the needle tip.

Question 52

Digital subtraction | angiography (DSA) should be used for all

Answer 52

cervical transforaminal or selective nerve root injections because the consequence of not detecting intravascular spread of contrast can lead to catastrophic complications

Question 53

CERVICAL TECHNIQUE Needle postion

Answer 53

The needle should not be advanced more than one-third of the facet column on the AP view. If perineural or epidural spread is not noted, the needle can be advanced slightly farther in the PA plane. Once appropriate epidural or perineural spread is noted without vascular uptake, a mixture of 1 ml of saline (or 1% lidocaine) and either 40 mg of triamcinolone, 6 mg of betamethasone, or 4 mg of dexamethasone are injected slowly.

Question 54

The presence of pain during an SNRB is not a very reliable sign that

Answer 54

needle touched the nerve root sheath.The needle may have irritated sensitive structures such as the joint capsule, periosteum, and annulus fibrosus and may cause referred pain to the leg

Question 55

Causes of SELECTIVE NERVE ROOT BLOCKS

Answer 55

herniated disc, | lateral recess stenosis, central canal stenosis, or pedicular kinking

Question 56

COMPLICATIONS

Answer 56

Spinal injections may cause infectious, cardiovascular, neurologic, and bleeding complications. Exposure to x-ray radiation and adverse, allergic, and anaphylactic reactions to the medications and the dye are added risks

Question 57

Risks specific to TFESI and SNRBs include

Answer 57

trauma to the spinal nerve, intrathecal injection if the needle penetrates the dural root sleeve, or segmental epidural when the medication is injected into the epidural space via the neural foramen

Question 58

Trauma to the artery of Adamkiewicz may cause

Answer 58

paraplegia and trauma to the segmental artery, which travels with the nerve root, may result in segmental cord infarct.

Question 59

Cervical TFESIs and SNRBs are inherently riskier

Answer 59

Spinal cord trauma, arterial injury, blindness, and brain or spinal cord infarct are added risks

Question 60

methylprednisolone use in lumbar selective nerve root injections NOT cervical SNRBs

Answer 60

methylprednisolone has the largest particle size of all of the steroids and easily precipitates. If injected through the any of the susceptible arteries including the vertebral, ascending cervical and deep cervical arteries, it may cause a segmental spinal cord infarct or settle in an end-artery in the brain causing a small infarct.

Question 61

Steroids used in cervical SNRBs

Answer 61

Triamcinolone has intermediate particle and maybe used. Betamethasone has the smallest size and should preferably be used if available

Question 62

indication for epidural steroid injections is

Answer 62

nerve root irritation

Question 63

The lumbar stabilization program consisted of

Answer 63

exercises emphasizing hip and hamstring flexibility and abdominal and lumbar paraspinal strengthening.