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US-guided interventional techniques at the cervical region

서울 학교 의과 학 마취통증의학교실

김 용 철

Fig. 1. Anatomy of the stellate ganglion.

최근 들어서 음 가 통증 역의 치료에 도입되면서 신속 정확하게 시술을 시행할 수 있게 되었고 그 만큼 시술에 따른

합병증도 어들게 되었다. 한 C-arm 유도 하에서 시행되었던 많은 술기들이 음 유도 하에서 시술이 가능해짐으로써

의료인과 환자의 방사선 노출도 어들게 되었다.

본 강의에서는 경추부에서 음 유도 하에 시술할 수 있는 표 인 질환들인 stellate ganglion block, brachial plexus

block with interscalene approach, superficial cervical plexus block, cervical facet joint injection, cervical medial branch block, spinal

accessory nerve block에 해서 간략히 설명하고자 한다. SGB는 prevertebral fascia 아래, longus colli 에 치하고 있다.

Stellate ganglion block

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128

Fig. 2. Annotated version of US anatomy of SGB.

Fig. 3. US anatomy at the C6 and C7 levels. A yellow arrow depicts path of needle. Place US probe medial to the anterior

tubercle of C6 to avoid any obstacle of the needle advancement. Block at the C7 level is not recommended. Using the anterior

approach, the needle is inserted through the thyroid gland, adjacent to the carotid artery and close to the inferior thyroid artery

and the recurrent laryngeal nerve. In addition, this approach requires the application of pressure to the anterior neck, which is

troubling for most patients [2].

Longus colli muscle의 근막을 뚫자 마자 5 ml 정도를 주사하면 즉시 블록이 일어 난다[1].

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Fig. 4. US anatomy at the mid level interscalene region.

Arrowheads = nerve roots. The ASM is now larger in

size at this level and more NRs are seen in the

interscalene groove.

Fig. 5. US anatomy at the lower level interscalene

region. Move the transducer caudad to visualize

branching of NRs (arrowheads) into trunks which travel

superficially towards the skin surface. The vertebral

artery (VA) usually becomes visible below the C6

transverse process.

Fig. 6. In Plane Approach (LEFT PANEL) and Out of Plane Approach (RIGHT PANEL). Clear identification of the needle

tip can be technically challenging in out of plane approach. It is advantageous to inject a small volume of local anesthetic (1

mL) during needle advancement to facilitate tracking of the needle tip [3].

Brachial plexus block with interscalene approach

Mid level interscalene region (C6 level)

Lower interscalene region (Below C6)

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Fig. 8. Schematic drawings of greater auricular nerve from the superficial cervical plexus and its US image. The plexus lies

on the SCM just posterior to the EJV.

Fig. 7. US image (RIGHT PANEL) and its annotated version (RIGHT PANEL) for injection during BPB [3].

주사 시에는 그림에서 보는 바와 같이 이상감각을 유발하지 않고 신경 주 에 주사를 하여야 신경 손상을 피할 수 있다.

Superficial cervical plexus block

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Fig. 9. Landmarks for superficial cervical plexus block: mastoid process, sternocleidomastoid muscle, posterior border of the

clavicular head, and transverse process of C6.

Fig. 10. A schematic drawing of spinal accessory nerve from the superficial cervical plexus and its US image. The nerve have

motor innervation of the SCM and TZ. However, it has no sensory component. It emerges under the SCM to lie on the levator

scapulae and middle scalene muscles ventral to the anterior border of the TZ.

Spinal accessory NB

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Fig. 12. Targets for cervical facet joints (LEFT PANEL) and medial

branch blocks (RIGHT PANEL).Fig. 11. A schematic drawing of the referred pain area of cervical facet

joints.

Fig. 13. A schematic illustrations of the location of medial branches (LEFT PANEL) and an annotated version of lateral image

of C-spine for the paths of cervical medial branches.

Cervical facet joint injection

문진 시에 어디로 연 통이 발생했느냐에 따라 블록을 시행할 경추 이나 후지들을 결정한다.

Cervical medial branch block

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Table 1. The Diameter and Distance from Bone of the Cervical

Medial Branches

Fig. 14. A US image of cervical spine. Yellow straight arrows indicates cervical facet joints and dark yellow arrows indicates

medial branches.

References

1. Shibata Y, Fujiwara Y, Komatsu T. A new approach of ultrasound-guided stellate ganglion block. Anesth Analg 2007; 105: 550-1.

2. Gofeld M, Bhatia A, Abbas S, Ganapathy S, Johnson M. Development and Validation of a New Technique for Ultrasound-Guided Stellate

Ganglion Block. Reg Anesth Pain Med 2009; 34: 475-9.

3. http://www.neuraxiom.com/index.php: useful internet site for US-guided techniques.

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가톨릭 학교 의과 학 마취통증의학교실

문 동 언

Ultrasound guided neuroaxial block and Ultrasonography in

pain medicine (USPM) is a rapidly growing medical field in

interventional pain management. Traditionally, spine interven-

tional procedures for pain management are performed with

imaging guidance such as fluoroscopy and computed tomog-

raphy (CT) scan. In the last few years, there has been tremen-

dous growth in USPM interest as evidenced by the remarkable

increase in the publication of literature on ultrasound (US)

guided injections. There is a growing trend in using ultra-

sonography in pain medicine as evident by the plethora of

published reports. Ultrasound (US) provides direct visualization

of various soft tissues and real-time needle advancement and

avoids exposing both the health care provider and the patient

to the risks of radiation. The US machine is more affordable

and transferrable than fluoroscopy, computed tomography scan,

or magnetic resonance imaging machine. In a previous review,

we discussed the challenges and limitations of US, anatomy,

sonoanatomy, and techniques of interventional procedures of

peripheral structures. In the present lecture, I will discuss the

sonoanatomy, and US-guided techniques of interventional pain

procedures for axial structures, paraspinal structure for example

quadrates lumborum muscle block, piriformis muscle block and

sacroiliac joint block.

Ultrasound imaging of the lumbar spine

For a transverse scan of the lumbar spine, the US transducer

is positioned over the spinous process with the patient in the

sitting or lateral position. On a transverse sonogram the spi-

nous process is seen as a hyperechoic reflection under the skin

and subcutaneous tissue, anterior to which there is a dark

acoustic shadow that completely obscures the underlying spinal

canal and thus the neuraxial structures. Therefore, this view is

not ideal for imaging the neuraxial structures but is useful for

identifying the midline when the spinous processes cannot be

palpated (obesity and in those with edema in their backs).

However, if one now slides the transducer slightly cranially or

caudally, it is possible to perform a transverse scan of the

lumbar spine with the US beam being insonated through the

interspinous space (interspinous view). Because the US signal

is now not impeded by the spinous process, the ligamentum

flavum, posterior dura, thecal sac, and the anterior complex

(discussed below) are visualized in the midline (from a posteri-

or-to-anterior direction) within the spinal canal, and laterally

the articular process of the facet joints and the transverse

processes are visible. The resultant sonogram produces a pat-

tern that Carvalho likens to a “flying bat. The interspinous

view can also be used to determine whether there is any rota-

tion in the vertebra, such as in scoliosis. Normally, the articu-

lar processes of the facet joint on either side are symmetrically

located. However, if they are asymmetrical or either one of

the articular processes is not visible, then one should suspect

rotation of the spine (provided the transducer is correctly posi-

tioned and aligned) and anticipate a potentially difficult spinal

or epidural. For a sagittal scan of the lumbar spine, the author

prefers to position the patient in the left lateral position with

the knees and hips slightly flexed. The transducer is positioned

1−2 cm lateral to the spinous process (midline) at the lower

back on the nondependent side with its orientation marker di-

rected cranially. The transducer is also tilted slightly medially

during the scan so the US beam is insonated in a PMOS

plane. During the scout scan, the L3/4 and L4/5 interlaminar

spaces are located as described above. On a PMOS sonogram

of the lumbar spine, the erector spinae muscles are clearly de-

lineated and lie superficial to the lamina. The lamina appears

hyperechoic and is the first osseous structure visualized.

Because bone impedes the passage of US, there is an acoustic

shadow anterior to each lamina. The sonographic appearance of

the lamina produces a pattern that resembles the head and

neck of a horse, which we refer to as the “horse head sign”.

The interlaminar space is the gap between the adjoining

lamina. In contrast, the articular processes of the facet joints

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appear as one continuous hyperechoic wavy line with no inter-

vening gaps as seen at the level of the lamina and are the

usual clues to differentiate the lamina from the articular

processes. In between the dark acoustic shadows of adjacent

lamina, there is a rectangular area in the sonogram where the

neuraxial structures are visualized. This is the “acoustic win-

dow” and results from reflections of the US signal from the

neuraxial structures within the spinal canal. The ligamentum

flavum is also hyperechoic and is often seen as a thick band

across two adjacent lamina. The posterior dura is the next hy-

perechoic structure anterior to the ligamentum flavum, and the

epidural space is the hypoechoic area (few millimeters wide)

between the ligamentum flavum and the posterior dura. The

thecal sac with the cerebrospinal fluid is the anechoic space

anterior to the posterior dura. The cauda equina, which is lo-

cated within the thecal sac, is often seen as multiple horizontal

hyperechoic shadows within the anechoic thecal sac, and their

location can vary with posture. Pulsations of the cauda equina

are also identified in some patients. The anterior dura is also

hyperechoic, but it is often difficult to differentiate it from the

posterior longitudinal ligament and the vertebral body as they

are of the same echogenicity (isoechoic) and very closely ap-

posed to each. This often results in a single, composite, hyper-

echoic reflection anteriorly that is also referred to as the

“anterior complex”.

Lumbar epidural injection

During lumbar epidural access, US imaging can be used to

preview the underlying spinal anatomy or to guide the needle

in real-time. As described above, real-time US guidance for

epidural access is performed either as a twooperator or as a

single-operator technique. In the former technique, which was

described by Grau and coworkers for combined spinal epidural

anesthesia, the first operator performs the US scan via the par-

amedian axis while the second operator performs the epidural

access via the midline using the traditional “loss-of-resistance”

technique. Grau and coworkers were able to visualize the ad-

vancing needle in all their cases despite the axis of the US

scan and the needle insertion being different. Moreover, they

were also able to visualize the dural puncture in all their pa-

tients and dural tenting in a few cases during the nee-

dle-through-needle spinal puncture. Recently, Karmakar have

described the successful use of real-time US guidance in con-

junction with loss of resistance to saline for paramedian epi-

dural access, performed by a single operator, with the epidural

needle inserted in the plane of the US beam. With this techni-

que, because the epidural needle is inserted in-plane, it is pos-

sible to visualize the advancing needle in real-time until it is

seen to engage in the ligamentum flavum. Anterior displace-

ment of the posterior dura and widening of the posterior epi-

dural space were the most frequently visualized changes within

the spinal canal, but compression of the thecal sac was also

seen in a few patients. These are objective signs of a correct

epidural injection and have previously been described in

children. The neuraxial changes that occur within the spinal

canal following the “loss of resistance” to saline may have

clinical significance and are discussed in detail in our report.

Despite our success with real-time USG epidural access, we

haven’t been able to visualize an indwelling epidural catheter

to date in adults. However, Karmakar has occasionally ob-

served changes within the spinal canal, for example, anterior

displacement of the posterior dura and widening of the posteri-

or epidural space, after an epidural bolus injection via the

catheter. These are surrogate markers of the location of the

catheter tip and are of limited value in clinical practice. There

is a need to develop new epidural catheter designs with im-

proved echogenicity.

Currently, there are limited outcome data following USG

lumbar epidural access, and the majority of the publications

have evaluated the use of performing a prepuncture US scan

or scout scan. A scout scan allows one to identify the midline

and accurately determine the interspace for needle insertion,

which are useful in patients in whom anatomical landmarks are

difficult to palpate, such as in those with obesity, edema of

the back, or abnormal anatomy (scoliosis, post laminectomy

surgery, or spinal instrumentation).

It also allows the operator to preview the neuraxial anatomy

accurately predict the depth to the epidural space, and de-

termine the optimal site and trajectory for needle insertion.

Cumulative evidence suggests that, when an US examination is

performed before the epidural puncture, it improves the success

rate of epidural access on the first attempt, reduces the number

of puncture attempts or the need to puncture multiple levels,

and also improves patient comfort during the procedure.

Lumbar medial-branch block

The patient is placed in the prone position, and a low-

frequency curvilinear transducer is used. First, a longitudinal

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midline sonogram is obtained to identify the correct spinal

level. The dorsal surface of the sacrum is easily identified, and

the lumbar spinal processes can be counted from caudal to

cephalad. By sliding the transducer laterally, a longitudinal par-

avertebral image is obtained, and the corresponding transverse

processes can be easily seen. Once the appropriate level is

identified, the transducer can be rotated transversely to obtain

a short-axis view showing the transverse process and the corre-

sponding SAP. The target is the groove at the junction be-

tween the base of the SAP and the superior border of the

transverse process. A 20-gauge needle is advanced in-plane

with the US beam from lateral to medial under real-time ultra-

sonography aiming toward the target. Once the bone is con-

tacted, a longitudinal paravertebral image is obtained to make

sure that the needle is at the cephalad margin of the corre-

sponding transverse process. L5 dorsal ramus block is usually

more difficult secondary to the US bony artifacts from the

iliac bone.

Lumbar facet intra-articular injection

The patient is placed in the prone position, and a low-

frequency curvilinear transducer is used. Once the appropriate

level is identified as above, the transducer can be rotated

transversely to obtain a short-axis view showing the facet joint

space between the inferior articular process and SAP. The tar-

get is the midpoint of the joint space. A 20-gauge needle is

advanced in-plane with the US beam from lateral to medial

under real-time ultrasonography aiming toward the target. Often

it is difficult to see the entire needle shaft clearly while it is

advanced because the needle angle is usually between 45 and

60 degrees.

As mentioned earlier, the major limitation of ultrasonography

is the inability to obtain a high-resolution image at such depth

needed for facet injections. That is why visualizing the sacral

hiatus, and as the lateral edge of the sacrum is identified, the

transducer is moved laterally and cephalad until the bony con-

tour of the ileum is identified. The cleft between the ileum

and the lateral sacral edge represents the SIJ, and the target is

the most inferior part. A 22-gauge needle is then inserted at the

medial end of the transducer and advanced laterally under direct

vision in-plane with the US beam until it enters the joint.

The major limitation is the potential for periarticular rather

than intra-articular injection compared with fluoroscopy, where

one can reliably obtain an arthrogram with contrast agent in-

jection in most cases. Also, US is not entirely reliable in de-

tecting intravascular injection while performing SIJ injections

secondary to the bony artifacts casted by the iliac bone.

Caudal epidural injection

With the patient in the prone position, the sacral hiatus is

palpated, and a linear high-frequency transducer (curved low-

frequency transducer in obese patients) is placed transversely at

the midline to obtain a sonographic transverse view of the sa-

cral hiatus. The 2 bony prominences of sacral cornua appear

as 2 hyperechoic reversed U-shaped structures. Between the 2

cornua, one can identify 2 hyperechoic band-like structures: the

sacrococcygeal ligament on top and the dorsal bony surface of

the sacrum at the bottom and the sacral hiatus as the hypo-

echoic area in between. A 22-gauge needle is then inserted be-

tween the 2 cornua into the sacral hiatus. A Bpop is usually

felt as the sacrococcygeal ligament is penetrated. The trans-

ducer was then rotated 90 degrees to obtain a longitudinal

view of the sacrum and sacral hiatus, and the needle is ad-

vanced into the sacral canal under real-time sonographic in the

longitudinal view. In adults, it is usually difficult to follow the

needle once in the sacral canal secondary to the bony artifacts

from the sacrum wall. After negative aspiration for cere-

brospinal fluid and blood, injection is carried out under re-

al-time sonography, where one can notice turbulence in the sa-

cral canal and monitor the spread of the injectate cephalad,

which is not an easy task in adults. Color Doppler mode may

be used as discussed above; however, it is very subjective and

unreliable because turbulence from the injectate can be in-

terpreted as flow in many directions with different colors and

can be misinterpreted as intravascular injection. The best way

to rule out unintentional intravascular or intrathecal injection is

still by contrast fluoroscopy. Ultrasound can be used if fluoro-

scopy is not available or to guide needle placement into the

sacral canal as an adjuvant to fluoroscopy.

Limitations of US in neuroaxial applications are discussed

earlier, and the authors feel that neuroaxial (intrathecal and

spinal) applications of US should be limited to regional anes-

thesia and obstetric anesthesia practice where fluoroscopy is

not readily available. Until we have better technology, US

should have no role in neuroaxial (intrathecal, epidural) blocks

in chronic pain practice as fluoroscopy (which is superior) is

readily available; hence, these applications will not be dis-

cussed in this review.

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Piriformis muscle injection

The key to successful needle placement is to locate the sci-

atic notch. Proximal to the sciatic notch is the ilium, which is

visualized as a hyperechoic line running across the scan image

from medial to lateral positions. Moving the probe medially,

the sacrum and SIJ are visualized. When the scan is in the

sciatic notch, the hyperechoic shadow of bone (ischium) is

seen only in the lateral part of the scan image. At this level,

2 layers of muscles, gluteus maximus muscle dorsally and pir-

iformis ventrally, will be visualized. By rotating the hip in-

ternally and externally with the knee flexed, the piriformis

muscle will be seen gliding underneath the gluteus maximus

muscle. By moving the probe in a medial-to-lateral position,

the origin and the insertion of the piriformis muscle can be

traced.

The ultrasound-guided techniques described in the literature

are quite similar. The patient is placed in the prone position.

With the use of a curvilinear probe with low frequency (2−5

Hz), scanning is performed in the transverse plane with the

probe placed caudad to the posterior superior iliac spine so

that the SIJ can be seen. The probe is then moved caudally to

the sciatic notch. The piriformis muscle is demonstrated by ro-

tating the hip internally and externally with the knee flexed.

The needle is inserted from medial to lateral using an in-plane

technique. It is important to scan from the ilium and move the

probe caudally to ensure the location of the sciatic notch, as

an inexperienced practitioner may mistake the other external

hip rotators (obturator externus, superior and inferior gemellus

muscle forming the tricipital tendons below the ischial spine)

for the piriformis.

Because of the anatomic anomalies of the sciatic nerve with-

in and below the piriformis muscle, we strongly suggest the

use of the nerve stimulator in preventing unintentional injection

in the vicinity of the sciatic nerve. For injection outside the

piriformis muscle, a small amount of normal saline (＜0.5 mL)

isinjected, which will confirm the location between the 2 mus-

cle layers (gluteus maximus and piriformis). If intramuscular

injection is attempted, the needle should be advanced further to

elicit strong muscle contractions. A very small amount of nor-

mal saline (＜0.5 mL) is injected to confirm the intramuscular

location of the needle. It is not uncommon for sciatic nerve

stimulation to be observed when the needle is advanced

through the piriformis muscle.

Sacroiliac joint injection

US was performed with a curved array transducer and oper-

ating at a gray-scale frequency between 2.5 and 6.0 MHz, ad-

justed to the frequency needed according to the penetration

depth. US scanning and needle insertion were performed by a

musculoskeletal radiologist with 5 years of experience in

US-guided injections. An axial US scan of the posterior area

of the cadavers was used to identify landmarks of the 2 dif-

ferent levels (puncture sites).

Upper level. For primary orientation, the posterior superior

iliac spine was visualized laterally, and the spinous process of

the fifth lumbar vertebra medially. Then the transducer was

moved caudally, depicting the dorsal surface of the sacrum

with the median and lateral sacral crest, the gluteal surface of

the ilium, and the posterior sacral foramen 1. The needle was

inserted into the hypoechoic cleft located between the surface

of the sacrum and the contour of the ilium

Lower level. For the lower level, the transducer was moved

downward by delineation of the median and lateral sacral crest,

at the dorsal surface of the sacrum and the gluteal surface of

the ilium until the posterior sacral foramen 2 was visualized.

As with the upper level, the needle was inserted into the hy-

poechoic cleft between the sacrum and ilium.

The SI joint consists of ear-shaped auricular surfaces of the

ilium and sacrum, resulting in a mainly vertical and antero-

lateral orientation. The posterosuperior compartment is fibrous,

whereas the anteroinferior compartment is synovial. The carti-

lage-lined portion extends more superiorly along the anterior

aspect of the joint, so that the few inferior centimeters repre-

sent a chondral joint from front to back. The transition line

between the cartilage and syndesmotic portions is inferiorly

convex. The entire joint is superficially stabilized by strong an-

terior and posterior ligaments to the interosseous ligaments and

the joint capsule.

Needle insertion using a 21-gauge needle was performed at

both levels under US guidance by freehand needle placement.

The tip of the needle was placed cranially to the puncture lev-

el by using a paraaxial transducer position first. Angulations of

needle insertion were determined according to the orientation

of the hypoechoic cleft. The hypoechoic cleft of the SI joint

shows cranially a more medial to lateral orientation, which be-

comes slightly more caudally vertically oriented. Therefore,

needle orientation is mainly vertical with only slight angula-

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tions from medial at the upper level and vertical at the lower

level. After needle positioning under the skin by a paraaxial

US scan, the needle was inserted toward the SI joint using a

longitudinal transducer position, visualizing the needle parallel

to the US beam. After reaching the entrance of the SI joint

with the tip of the needle, a paraaxial transducer position al-

lowed for further vertically oriented needle introduction under

a perpendicular US beam, so that the tip of the needle could

be visualized in the hypoechoic cleft. Care was taken to insert

the needle directly toward the hypoechoic cleft, to avoid any

bony spurs. Once the needle tip was depicted in the hypo-

echoic cleft, a further insertion of less than 1 cm was at-

tempted by pushing the needle into the joint space.