Spinal Ultrasound

Number: 0628

Table Of Contents

Policy
Applicable CPT / HCPCS / ICD-10 Codes
Background
References

---

Policy

Scope of Policy

This Clinical Policy Bulletin addresses spinal ultrasound.

1. Medical Necessity

   Aetna considers ultrasound of the spine and para-spinal tissues medically necessary for the following indications:

   1. In newborns and infants for the following indications:

      1. Detection of sequelae of injury (e.g., hematoma after spinal tap or birth injury; post-traumatic leakage of cerebrospinal fluid; and sequelae of prior instrumentation, infection, or hemorrhage);
      2. Evaluation of suspected defects such as cord tethering, diastematomyelia, hydromyelia, and syringomyelia;
      3. Guidance for lumbar puncture;
      4. Lumbosacral stigmata known to be associated with spinal dysraphism;
      5. Post-operative assessment for cord retethering;
      6. Spectrum of caudal regression syndrome (e.g., anal atresia or stenosis; sacral agenesis);
      7. Visualization of fluid with characteristics of blood products within the spinal canal in neonates and infants with intra-cranial hemorrhage;

   2. When performed intra-operatively.

2. Experimental, Investigational, or Unproven

   Ultrasound of the spine and para-spinal tissues is considered experimental, investigational, or unproven for any of the following (not an all-inclusive list) because its effectiveness has not been established:

   1. Diagnostic ultrasound of the spine and para-spinal tissues for evaluation of neuro-musculoskeletal conditions and all other indications (e.g., evaluation of curve flexibility before surgical intervention for scoliosis, evaluation and management of spinal epidural abscess, in the practice of neuraxial (epidural and subarachnoid) blocks, and to assist in lumbar puncture (except in newborns and infants));
   2. Management of individuals with spinal muscular atrophy;
   3. SonixGPS (a real-time ultrasound-guided spinal anesthesia system).

---

Table:

CPT Codes / HCPCS Codes / ICD-10 Codes

Code	Code Description
Information in the [brackets] below has been added for clarification purposes.   Codes requiring a 7th character are represented by "+":
CPT codes covered if selection criteria are met:
76800	Ultrasound, spinal canal and contents
Other CPT codes related to the CPB:
62320 - 62323	Injection(s), of diagnostic or therapeutic substance(s) (eg, anesthetic, antispasmodic, opioid, steroid, other solution), not including neurolytic substances, including needle or catheter placement, interlaminar epidural or subarachnoid
62324 - 62327	Injection(s), including indwelling catheter placement, continuous infusion or intermittent bolus, of diagnostic or therapeutic substance(s) (eg, anesthetic, antispasmodic, opioid, steroid, other solution), not including neurolytic substances, interlaminar epidural or subarachnoid
64400 - 64530	Introduction/injection of anesthetic agent (nerve block), diagnostic or therapeutic
HCPCS codes not covered for indications listed in the CPB:
SonixGPS:
No specific code
ICD-10 codes covered if selection criteria are met:
G96.0	Cerebrospinal fluid leak [post-trauma]
G97.51	Postprocedural hemorrhage of a nervous system organ or structure following a nervous system procedure [following lumbar puncture]
G97.61	Postprocedural hematoma of a nervous system organ or structure following a nervous system procedure
G97.63	Postprocedural seroma of a nervous system organ or structure following a nervous system procedure
P10.0 - P10.3, P10.8 - P10.9	Subdural and cerebral hemorrhage [due to birth trauma]
P11.5	Birth injury to spine and spinal cord
P52.0 - P52.22	Intracranial nontraumatic hemorrhage of newborn [grades 1 through 4]
P52.3	Unspecified intraventricular (nontraumatic) hemorrhage of newborn
P52.5	Subarachnoid (nontraumatic) hemorrhage of newborn
Q05.0 - Q05.9	Spina bifida
Q06.0 - Q06.9	Other congenital malformations of spinal cord
Q07.01 - Q07.03	Arnold-Chiari syndrome with spina bifida
Q42.2	Congenital absence, atresia and stenosis of anus with fistula
Q42.3	Congenital absence, atresia and stenosis of anus without fistula
Q76.49	Other congenital malformations of spine, not associated with scoliosis [sacrum]
ICD-10 codes not covered for indications listed in the CPB:
G06.1	Intraspinal abscess and granuloma
G12.0 – G12.9	Spinal muscular atrophy and related syndromes
G54.0 - G59	Nerve, nerve root and plexus disorders
G60.0 - G65.2	Polyneuropathies and other disorders of the peripheral nervous system
G70.00 - G73.7	Diseases of myoneural junction and muscle
M41.00 - M41.9	Scoliosis
M50.00 - M51.9, M51.A0 -M51.A5	Cervical, thoracic, thoracolumbar, and lumbosacral intervertebral disc disorders
M53.0 - M53.9	Other and unspecified dorsopathies, not elsewhere classified
M54.00 - M54.9	Dorsalgia

---

Background

Spinal ultrasound (US) is a non-invasive diagnostic imaging technique used to evaluate individuals for possible defects of the spinal column or spinal cord.

The ACR (1996) adopted the following statement on spinal US: "Over the past several years interest has developed in the use of ultrasound technology for the evaluation of the spine and paraspinal regions in adults.  While diagnostic ultrasound is appropriately used 1) intraoperatively; 2) in the newborn and infants for the evaluation of the spinal cord and canal; and 3) for multiple musculoskeletal applications in adults, there is currently no documented scientific evidence of the efficacy of this modality in the evaluation of the paraspinal tissues and the spine in adults.  Any claims or inferences that the use of spinal or paraspinal ultrasound is more advantageous or has a greater diagnostic accuracy than established procedures such as computed tomography (CT) or magnetic resonance imaging (MRI) cannot be made today based on recognized medical research".

An AAN Report (1998) on spinal US for the evaluation of back pain and radicular disorders concluded: "Currently, no published peer reviewed literature supports the use of diagnostic ultrasound in the evaluation of patients with back pain or radicular symptoms.  The procedure cannot be recommended for use in the clinical evaluation of such patients".

The American Institute of Ultrasound Medicine (AIUM, 2002) made the following official statement: "There is insufficient evidence in the peer-reviewed medical literature establishing the value of non-operative spinal/paraspinal ultrasound in adults.  Therefore, the AIUM states that, at this time, the use of non-operative spinal/paraspinal ultrasound in adults (for study of facet joints and capsules, nerve and fascial edema, and other subtle paraspinous abnormalities) for diagnostic evaluation, for evaluation of pain or radiculopathy syndromes, and for monitoring of therapy has no proven clinical utility.  Non-operative spinal/paraspinal ultrasound in adults should be considered investigational.  The AIUM urges investigators to perform proper double-blind research projects to evaluate the efficacy of these diagnostic spinal ultrasound examinations".

Glotzbecker and colleagues (2009) noted that the risk of thrombo-embolic disease is well-studied for some orthopedic procedures.  However, the incidence of post-operative thrombo-embolic disease is less well-defined in patients who have had spinal surgery.  These investigators performed a systematic review on thrombo-embolic disease in spinal surgery.  The Medline database was queried using the search terms deep venous thrombosis or DVT, pulmonary embolus, thromboembolic disease, and spinal or spine surgery.  Abstracts of all identified articles were reviewed.  Detailed information from eligible articles was extracted.  Data were compiled and analyzed by simple summation methods when possible to stratify rates of DVT and/or pulmonary embolus for a given prophylaxis protocol, screening method, and type of spinal surgery.  A total of 25 articles were eligible for full review.  The risk of DVT ranged from 0.3 % to 31 %, varying between patient populations and methods of surveillance.  Pooling data from the 25 studies, the overall rate of DVT was 2.1 %.  The rate of DVT was influenced by prophylaxis method: no prophylaxis, 2.7 %; compression stockings (CS), 2.7 %; pneumatic sequential compression device (PSCD), 4.6 %; PSCD and CS, 1.3 %; chemical anti-coagulants, 0.6 %; and inferior vena cava filters with/without another method of prophylaxis, 22 %.  The rate of DVT was also influenced by the method of diagnosis, ranging from 1 % to 12.3 %.  The authors concluded that as risk of DVT after routine elective spinal surgery is fairly low, it seems reasonable to use CS with PSCD as a primary method of prophylaxis.  There is insufficient evidence to support or refute the use of chemical anti-coagulants in routine elective spinal surgery.  Furthermore, there is insufficient evidence to suggest that screening patients undergoing elective spinal surgery with ultrasound or venogram is routinely warranted.

Tsui and Suresh (2010) presented a comprehensive review of the evidence pertaining to techniques described and outcomes evaluated for US imaging in pediatric neuraxial anesthesia.  Neuraxial anesthesia pertains to local anesthetics placed around the nerves of the central nervous system, such as spinal anesthesia also called subarachnoid anesthesia and epidural anesthesia.  These researchers described and illustrated the anatomy related to each block to serve as a foundation for better understanding the block techniques described.  For neuraxial blockade, US may fairly reliably predict the depth to loss of resistance and can enable a dynamic view of the needle and catheter after entry into the spinal canal.  Particularly, in young infants, direct visualization of the needle and catheter tip may be possible, whereas in older children surrogate markers including the displacement of dura mater by the injection of fluid may be necessary for confirming needle and catheter placement.  The authors stated that more outcome-based, prospective, randomized, controlled trials are needed to prove the benefits of US when compared with conventional methods.

1. ultrasound-assisted neuraxial techniques and
2. real-time ultrasound-guided neuraxial techniques.

The author concluded that neuraxial US has been recently introduced to regional anesthesia practice.  The limited data available to date suggested that it is a useful adjunct to physical examination, allowing for a highly precise identification of regional landmarks and a precise estimation of epidural space depth, thus facilitating epidural catheter insertion.  Moreover, they stated that further research is needed to conclusively establish its impact on procedure success and safety profile, especially in the adult non-obstetric population.  This is in agreement with Tsui and Pillay (2010) who noted that although there is some evidence to support US for various outcomes in pediatric regional anesthesia, more randomized controlled studies with sufficient power are needed to further support these findings and to evaluate the potential for US to reduce complications for regional anesthesia in children.

Javanshir and colleagues (2010) reviewed the literature concerning size measurement of cervical muscles using real-time US imaging (RUSI) in patients with neck pain and in healthy populations.  A literature search from 1996 to December 2009 making use of Science Direct and PubMed databases was conducted.  Medical Subject Headings and other terms were as follows: ultrasonography, cervical, muscle, neck, size, pain, validity, reliability, neck pain, and healthy subjects.  These researchers included studies using RUSI for assessing cervical paraspinal muscles both in healthy subjects as well as in patients with neck pain.  They assessed muscles investigated and the reliability and validity of the method used.  The literature search yielded 16 studies – 12 (75 %) studies assessed the posterior muscles, whereas in the remaining 4 (25 %), the anterior muscles were studied.  Three studies quantified the size of the muscles during contraction; 3 assessed the relationship between cross-sectional area, linear dimensions, and anthropometric variables; 1 evaluated the training-induced changes in muscle size; 1 assessed the differences in muscle shape and cross-sectional area of cervical multifidus between patients with chronic neck pain and controls; 8 studies looked at the reliability of using RUSI in patients with neck pain or healthy subjects; and 3 studies evaluated the validity of RUSI compared with magnetic resonance imaging.  The authors concluded that this literature review has shown that there are insufficient studies for assessing neck muscles with RUSI.  It seems that using constant landmarks, knowledge of anatomy and function of target muscle, and a proper definition of muscle borders can help to take a clear image.  Standardized position of the subject, correct placement of the transducer, and using multiple RUSI for statistical analyses may improve results.

The Work Loss Data Institute's clinical practice guideline on "Neck and upper back (acute & chronic)" (2011) listed diagnostic US as one of the interventions that was considered, but was not recommended.

The American Institute of Ultrasound in Medicine's practice guideline for the performance of an US examination of the neonatal spine (2012) states that this guideline has been developed to assist practitioners performing a sonographic examination of the neonatal and infant spine.  In some cases, an additional or specialized examination may be necessary.  While it is not possible to detect every abnormality, following this guideline will maximize the detection of abnormalities of the infant spine.  Sonographic examination of the pediatric spinal canal is accomplished by scanning through the normally incompletely ossified posterior elements.  Therefore, it is most successful in the newborn period and in early infancy.  In infants older than 6 months, the examination can be very limited, although the level of termination of the cord may be identified.  In experienced hands, US imaging of the infant spine has been shown to be an accurate and cost-effective examination that is comparable to magnetic resonance imaging (MRI) for evaluating congenital or acquired abnormalities in the neonate and young infant.

The guideline lists the following indications for US examination of the neonatal spine:

• Detection of sequelae of injury (e.g., hematoma after spinal tap or birth injury; post-traumatic leakage of cerebrospinal fluid; and sequelae of prior instrumentation, infection, or hemorrhage).
• Evaluation of suspected defects such as cord tethering, diastematomyelia, hydromyelia, and syringomyelia.
• Guidance for lumbar puncture.
• Lumbosacral stigmata known to be associated with spinal dysraphism.
• Post-operative assessment for cord retethering.
• Spectrum of caudal regression syndrome (e.g., anal atresia or stenosis; sacral agenesis).
• Visualization of fluid with characteristics of blood products within the spinal canal in neonates and infants with intra-cranial hemorrhage.

Chin and Perlas (2011) stated that the use of US in lumbar plexus blockade has been described in the context of both pre-procedural imaging and real-time needle guidance; however, its clinical benefit in this setting has not yet been clearly established.  These investigators noted that pre-procedural US imaging of the spine may reduce the technical difficulty of neuraxial blockade and also improve clinical efficacy.  Similar benefits are expected in the setting of lumbar plexus blockade although there is currently no evidence to confirm this.  Moreover, they stated that real-time US-guided neuraxial and lumbar plexus blockade are challenging techniques that need further validation.

In a randomized controlled trial (RCT), Arzola et al (2015) examined the impact of pre-procedural spinal US on the ease of insertion of labor epidurals by a group of trainees. These researchers hypothesized that the US-assisted technique would improve the ease of insertion when compared with the conventional palpation technique.  A group of 17 2nd-year anesthesia residents and 5 anesthesia fellows underwent a training program in US assessment of the spine.  Parturients with easily palpable lumbar spines were randomized to either US or palpation group.  Residents and fellows performed both the assessment (US or palpation) and the epidural procedure.  Primary outcome measures were ease of insertion of epidural catheter composed of the time taken to insert the epidural catheter, number of inter-space levels attempted and number of needle passes; secondary outcome measures were total procedural time (assessment and insertion), 1st pass success rate, number of attempts needed to thread the epidural catheter, failure of epidural analgesia, and patient satisfaction.  These investigators analyzed 128 epidural catheter insertions (residents 84, fellows 44).  There was no difference in median (interquartile range, IQR) epidural insertion time between the US and palpation groups [174 (120 to 241) versus 180 (130 to 322.5) s, respectively; p = 0.14].  The number of inter-space levels attempted and needle passes were also similar in both groups.  The total procedural time was longer in the US group.  The authors concluded that the use of pre-procedural spinal US by a cohort of anesthesia trainees did not improve the ease of insertion of labor epidural catheters in patients with easily palpable lumbar spines, as compared with the traditional palpation technique based on anatomical landmarks.

1. Does US accurately identify a given lumbar intervertebral space?
2. Does US accurately predict the needle insertion depth required to reach the epidural or intrathecal space? And
3. Does US improve the safety and effectiveness of spinal or lumbar epidural anesthesia?

A total of 31 clinical trials and 1 meta-analysis were included in this review.  Data from 8 studies indicated that neuraxial US can identify a given lumbar intervertebral space more accurately than by landmark palpation alone; 13 studies reported an excellent correlation between US-measured depth and needle insertion depth to the epidural or intrathecal space.  The mean difference between the 2 measurements was within 3 mm in most studies; 13 RCTs, 5 cohort studies, and 1 meta-analysis reported data on safety and effectiveness outcomes.  Results consistently showed that US resulted in increased success and ease of performance.  Ultrasound appeared to reduce the risk of traumatic procedures but there was otherwise insufficient evidence to conclude if it significantly improves safety.  The authors concluded that there is significant evidence supporting the role of neuraxial US in improving the precision and effectiveness of neuraxial anesthetic techniques.  Moreover, the authors noted they know that neuraxial US is a useful complement to clinical examination when performing lumbar central neuraxial blocks.  It provides anatomical information including the depth of the epidural space, the identity of a given intervertebral level, and the location of the midline and inter-spinous/inter-laminar spaces.  This information can be used to successfully guide subsequent needle insertion.  Since 2010, new data from RCTs and 1 meta-analysis suggested that neuraxial US increases the success and reduces the technical difficulty of lumbar central neuraxial blocks.  They stated that findings from the meta-analysis suggested that neuraxial US reduces the risk of traumatic procedures, and thus may possibly contribute to the safety of lumbar central neuraxial blocks.

The SonixGPS

Wong and colleagues (2013) stated that the SonixGPS is an electromagnetic needle tracking system for US-guided needle intervention.  Both current and predicted needle tip position are displayed on the ultrasound screen in real-time, facilitating needle-beam alignment and guidance to the target.  This case report illustrated the use of the SonixGPS system for successful performance of real-time US-guided spinal anesthesia in a patient with difficult spinal anatomy.  A 67-year old man was admitted to the authors’ hospital to undergo revision of total right hip arthroplasty.  His 4 previous arthroplasties for hip revision were performed under general anesthesia because he had undergone L3 to L5 instrumentation for spinal stenosis.  The L4 to L5 inter-space was viewed with the patient in the left lateral decubitus position.  A 19-G 80-mm proprietary needle (Ultrasonix Medical Corp, Richmond, BC, Canada) was inserted and directed through the para-spinal muscles to the ligamentum flavum in plane to the US beam.  A 120-mm 25-G Whitacre spinal needle was then inserted through the introducer needle in a conventional fashion.  Successful dural puncture was achieved on the second attempt, as indicated by a flow of clear cerebrospinal fluid (CSF).  The patient tolerated the procedure well, and the spinal anesthetic was adequate for the duration of the surgery.  The authors concluded that the SonixGPS is a novel technology that can reduce the technical difficulty of real-time US-guided neuraxial blockade.  It may also have applications in other advanced US-guided regional anesthesia techniques where needle-beam alignment is critical.

Brinkman et al (2013) noted that the SonixGPS is a novel needle tracking system that has recently been approved in Canada for US-guided needle interventions.  It allows optimization of needle-beam alignment by providing a real-time display of current and predicted needle tip position.  Currently, there is limited evidence on the effectiveness of this technique for performance of real-time spinal anesthesia.  This case-series reported performance of the SonixGPS system for real-time US-guided spinal anesthesia in elective patients scheduled for joint arthroplasty.  In this single-center case-series study, a total of 20 American Society of Anesthesiologists' class I to II patients scheduled for lower limb joint arthroplasty were recruited to undergo real-time US-guided spinal anesthesia with the SonixGPS after written informed consent.  The primary outcome for this clinical cases-series was the success rate of spinal anesthesia, and the main secondary outcome was time required to perform spinal anesthesia.  Successful spinal anesthesia for joint arthroplasty was achieved in 18/20 patients, and 17 of these required only a single skin puncture.  In 7/20 (35 %) patients, dural puncture was achieved on the first needle pass, and in 11/20 (55 %) patients, dural puncture was achieved with 2 or 3 needle re-directions.  Median (range) time taken to perform the block was 8 (5 to 14) mins.  The study procedure was aborted in 2 cases because the clinical protocol dictated using a standard approach if spinal anesthesia was unsuccessful after 3 US-guided insertion attempts.  These 2 cases were classified as failures.  No complications, including paresthesia, were observed during the procedure.  All patients with successful spinal anesthesia found the technique acceptable and were willing to undergo a repeat procedure if deemed necessary.  The authors concluded that the findings of this case-series study showed that real-time US-guided spinal anesthesia with the SonixGPS system is possible within an acceptable time frame.  It proved effective with a low rate of failure and a low rate of complications.  They stated that their clinical experience suggested that a randomized trial is needed to compare the SonixGPS with a standard block technique.

Niazi and colleagues (2014) noted that real-time US-guided neuraxial blockade remains a largely experimental technique.  SonixGPS is a new needle tracking system that displays needle tip position on the US screen.  In a feasibility study, these researchers investigated if this novel technology might aid performance of real-time US-guided spinal anesthesia.  A total of 20 patients with body mass index (BMI) less than 35 kg/m(2) undergoing elective total joint arthroplasty under spinal anesthesia were recruited.  Patients with previous back surgery and spinal abnormalities were excluded.  Following a pre-procedural US scan, a 17-G proprietary needle-sensor assembly was inserted in-plane to the transducer in 4 patients and out-of-plane in 16 patients.  In both approaches, the trajectory of insertion was adjusted in real-time until the needle tip lay just superficial to the ligamentum flavum-dura mater complex.  At this point, a 25-G 120 mm Whitacre spinal needle was inserted through the 17-G SonixGPS needle.  Successful dural puncture was confirmed by backflow of CSF from the spinal needle.  An overall success rate of 14/20 (70 %) was seen with 2 failures (50 %) and 4 failures (25 %) in the in-plane and out-of-plane groups, respectively.  Dural puncture was successful on the first skin puncture in 71 % of patients and in a single needle pass in 57 % of patients.  The median total procedure time was 16.4 and 11.1 mins in the in-plane and out-of-plane groups, respectively.  The authors concluded that the SonixGPS system simplified real-time US-guided spinal anesthesia to a large extent, especially the out-of-plane approach.  Nevertheless, it remains a complex multi-step procedure that requires time, specialized equipment, and a working knowledge of spinal sonoanatomy.

McVicar et al (2015) stated that US-guided needle placement is a widely used technical skill that can be challenging to learn.  The SonixGPS is a novel ultrasound needle-tracking system that has the potential to improve performance over traditional US systems.  These researchers examined if the use of the SonixGPS US system improves performance of novice practitioners in ultrasound-guided needle placement compared with conventional US in the out-of-plane approach on a simulation model.  A total of 26 medical students without previous US experience were randomized into 2 groups.  Each group performed 30 simulated US nerve blocks on a porcine meat tissue simulation (phantom) model.  Both groups used the SonixGPS US; however, the study group had the needle-tracking system activated, whereas the control group did not.  The participants were assessed for success rate, technical aspects of block performance, and certain behaviors that could compromise the quality of the block.  Learning curves were developed to assess competence.  The needle guidance group reached competence more often.  This group had fewer attempts and quality-compromising behaviors than did those using conventional US.  The authors concluded that use of the SonixGPS US needle guidance system improved the performance of technical needling skills of novice trainees in an ex-vivo model.  They stated that the place of this technology in the wider education of US-guided regional anesthesia remains to be established.

Li et al (2017) noted that SonixGPS is a novel real-time US navigation technology, which has been shown to promote accuracy of puncture in surgical operations.  In a retrospective study, these researchers examined its use in guiding the puncture during percutaneous nephrolithotomy (PCNL).  They reviewed their experience in treating a total of 74 patients with complex kidney stones with PCNL, in which puncture in 37 cases were guided by SonixGPS system, while the other 37 by conventional US.  The effectiveness of operation was examined in terms of stone clearance rate, operation time, time to successful puncture, number of attempts for successful puncture and hospital stay.  The safety of operation was examined by evaluating post-operative complications.  This retrospective review showed that although there were no significant differences in stone clearance rates between the groups, SonixGPS guidance resulted in more puncture accuracy with shorter puncture time and higher successful puncture rate.  Under the help of SonixGPS, most patients (92 %) had no or just mild complications, compared to that (73 %) in the conventional US group.  Post-operative decrease of hemoglobin in SonixGPS group was 13.79 (7 to 33) mg/dL, significantly lower than 20.97 (8 to 41) mg/dL in conventional US group.  The authors concluded that this study was the first to systematically compare the cutting-edge guiding modality of SonixGPS with conventional guiding modalities in terms of their use in the treatment of complex kidney stones with PCNL.  These investigators stated that effective with good stone clearance rate, the SonixGPS system appeared to facilitate puncture accuracy; thereby, reducing complications and blood loss.  They stated that the SonixGPS system may represent a new generation of real-time guidance modality for accurate puncture in PCNL treatment.  Moreover, these researchers stated that like any other retrospective study, this trial was susceptible to the limitations and biases inherent in a retrospective design.

Evaluation of Curve Flexibility Before Surgical Intervention for Scoliosis

In a pilot study, Zheng and colleagues (2017) examined the use of US imaging to evaluate the spinal curve flexibility of scoliotic surgical candidates; a total of 15 patients were enrolled in this study.  Pre-operative radiographs and US images in both standing and bending positions were acquired.  The post-operative standing radiographs were obtained 1 week after surgery; 2 raters measured the ultrasound images twice, 1 week apart.  A curve correction index was developed to estimate the curve flexibility.  The correction index from the pre-operative bending radiograph, US and post-operative radiograph were 0.51 ± 0.18; R1: 0.74 ± 0.08 versus R2: 0.72 ± 0.09 and 0.60 ± 0.10, respectively.  The correlation of correction index between US and post-operative radiography was slightly higher than the pre-operative bending and post-operative radiography.  The authors concluded that the findings of this pilot study showed that the bending US method is a promising supplemental tool to assess curve flexibility before surgical intervention for scoliotic surgical candidates.  These preliminary findings need to be validated by well-designed studies.

Evaluation and Management of Spinal Epidural Abscess

DeFroda and associates (2016) noted that spinal epidural abscess (SEA) is an uncommon and potentially catastrophic condition; it often presents a diagnostic challenge, as the "classic triad" of fever, spinal pain, and neurological deficit is evident in only a minority of patients.  When diagnosis is delayed, irreversible neurological damage may ensue.  To minimize morbidity, an appropriate level of suspicion and an understanding of the diagnostic evaluation are essential.  Infection should be suspected in patients presenting with axial pain, fever, or elevated inflammatory markers.  Although patients with no known risk factors can develop SEA, clinical concern should be heightened in the presence of diabetes, intravenous drug use, chronic renal failure, immunosuppressant therapy, or a recent invasive spine procedure.  The authors stated that when the clinical profile is consistent with the diagnosis of SEA, gadolinium-enhanced MRI of the spinal column should be obtained on an emergent basis to delineate the location and neural compressive effect of the abscess.  Spinal US was not mentioned as a management tool.

Chima-Melton and colleagues (2017) stated that SEA is a rare but serious cause of back pain in the critical care setting; it occurs most commonly in adults in their 5th and 6th decades of life.  Risk factors include diabetes mellitus, alcoholism, AIDS or other immunocompromised states, cancer, intravenous drug use, trauma and spinal surgery.  The clinical presentation can be non-specific but the classical triad includes back pain, fever and neurological deficits; MRI with gadolinium is the diagnostic imaging modality of choice.  These investigators reported a case of SEA in a 63-year old man with type II diabetes who presented with severe low back pain (LBP).  He was found to have SEA likely secondary to a hip joint injection.  The diagnosis was delayed due an earlier non-gadolinium-enhanced MRI of the spine showing no epidural abscess.  The authors concluded that this case emphasized the need for the definitive diagnostic study, MRI with gadolinium, in patients whose SEA is high on the list of differential diagnoses.  Spinal US was not mentioned as a management tool.

Furthermore, an UpToDate review on "Spinal epidural abscess" (Sexton and Sampson, 2017) does not mention spinal US as a management tool.

Injection for Low Back Pain

In a systematic review, Hofmeister and colleagues (2019) evaluated the literature comparing US-guided injections to fluoroscopy-guided injections for the management of low back pain (LBP).  Medline, Cochrane CENTRAL Register of Controlled Trials, Embase, and NHSEED were searched from 2007 to September 26, 2017.  Inclusion criteria included: RCT design, compared US-guided and fluoroscopy-guided injections for LBP; dose and volume of medications injected were identical between trial arms, and reported original data.  A total of 101 unique records were identified, and 21 studies were considered for full-text inclusion; 9 studies formed the final data set.  Studies comparing US- and fluoroscopy-guided injections for LBP management reported no difference in pain relief, procedure time, number of needle passes, changes in disability indices, complications or AEs, post-procedure opioid consumption, or patient satisfaction.  The authors concluded that fluoroscopic guidance of injections for the management of LBP was similar in efficacy to US guidance.  These researchers stated that further study is needed to understand the exact role of US in image-guided injections.

In a cadaveric, pilot study, Plaikner and colleagues (2019) described a new simple US approach for para-radicular injections of the sacral spinal nerves and examined the feasibility and accuracy by means of CT and anatomic dissection.  A total of 8 US-guided injections at 4 different levels of the sacral spine on a human ethanol-glycerol-embalmed cadaver (S1 to S4) were performed.  By means of sonography the sacral foramina were identified and the spinal needles were advanced in "in-plane technique" to the medial margin of the respective sacral foramen.  Subsequently a solution of blue dye and contrast agent were injected.  Then CT scans and anatomic dissection of the cadaver were performed to verify the correct placement of the needle tips and to visualize the dispersion of the injected solution in the respective compartment.  Altogether a 100 % success rate for a correct injection could be achieved; CT examination confirmed the correct placement of every needle tip within the intended compartment.  Furthermore, the anatomic dissections affirmed the appropriate needle positioning.  Moreover, the blue dye dispersion was observed in the correct compartments and around the targeted spinal nerves.  The authors concluded that although this study was only performed on cadaveric models, this new sonographic approach for para-radicular injections in the sacral spine allowed an easy, precise and un-erring needle placement within the dorsal sacral foramen.  These preliminary findings need to be validated by well-designed studies.

Nerve Ultrasound for Detection of Chronic Inflammatory Neuropathies

Kerasnoudis (2013) stated that chronic inflammatory demyelinating polyneuropathy (CIDP) is the most common acquired immune-mediated inflammatory disorder of the peripheral nervous system.  The diagnosis is based mainly on the clinical presentation and electrophysiological detection of demyelination.  Several MRI studies have demonstrated hypertrophy and abnormal enhancement of spinal nerve roots or brachial plexus in CIDP, but there have been only anecdotal reports of similar sonographic findings.  These investigators reported the sonographic findings of a CIDP case and included a review of the literature and previously reported cases.  The authors concluded that this case report highlighted the importance of sonography in the localization and recognition of focal nerve enlargements in patients with CIDP.  This method could be a helpful tool in the diagnosis of conduction block in CIDP, especially in cases where a nerve segment could not be examined easily with the inching technique.  Moreover, these researchers stated that systematic data are needed to confirm this finding.

Goedee and associates (2019) presented a case series of 6 treatment-naive patients with clinical phenotypes compatible with CIDP and multifocal motor neuropathy (MMN) without electrodiagnostic features of demyelination but with abnormal peripheral US findings who responded to treatment.  All 6 patients underwent a complete set of ancillary investigations, including extensive nerve conduction studies (NCS).  These researchers also carried out standardized nerve US of median nerves and brachial plexus as part of a larger effort to examine diagnostic value of sonography.  Nerve conduction studies did not show conduction block or other signs of demyelination in any of the 6 patients.  Sonographic nerve enlargement was present in all patients and was most prominent in proximal segments of the median nerve and brachial plexus.  Treatment with intravenous immunoglobulin (IVIG) resulted in objective clinical improvement.  Th authors concluded that the findings of this study provided evidence that nerve US represented a useful complementary diagnostic tool for the identification of treatment-responsive inflammatory neuropathies.  These preliminary findings need to be validated by well-designed studies.

In a prospective, cohort study, Herraets and colleagues (2020) examined the diagnostic accuracy of nerve US of patients with a clinical suspicion of chronic inflammatory neuropathies, including CIDP, Lewis-Sumner syndrome, and MMN, and determined the added value in the detection of treatment-responsive patients.  Between February 2015 and July 2018, these researchers included 100 consecutive incident patients with a clinical suspicion of chronic inflammatory neuropathy.  All patients underwent nerve US, extensive standardized NCS, and other relevant diagnostic investigations.  They examined treatment response using pre-defined criteria.  A diagnosis of chronic inflammatory neuropathy was established when NCS were abnormal (fulfilling criteria of demyelination of the European Federation of Neurological Societies/Peripheral Nerve Society) or when the degree of nerve enlargement detected by sonography was compatible with chronic inflammatory neuropathy and there was response to treatment.  A diagnosis of chronic inflammatory neuropathy was established in 38 patients.  Sensitivity and specificity of nerve US and NCS were 97.4 % and 69.4 %, and 78.9 % and 93.5%, respectively.  The added value of nerve US in detection of treatment-responsive chronic inflammatory neuropathy was 21.1 % compared to NCS alone.  The authors concluded that nerve US and NCS were complementary techniques with superior sensitivity in the former and specificity in the latter.  These researchers stated that the addition of nerve US significantly improved the detection of chronic inflammatory neuropathies; thus, it deserved a prominent place in the diagnostic work-up of chronic inflammatory neuropathies.  This study provided Class IV evidence that nerve US is an accurate diagnostic tool to detect chronic inflammatory neuropathies.

Furthermore, an UpToDate review on "Chronic inflammatory demyelinating polyneuropathy: Etiology, clinical features, and diagnosis" (Lewis, 2020) states that "Nerve ultrasound – When appropriate expertise is available, neuromuscular ultrasound can also be used to detect nerve hypertrophy in patients with acquired and hereditary forms of chronic demyelinating neuropathies. Although the findings are not specific for CIDP, they may help indicate regions of involvement".  Moreover, nerve ultrasound is not listed in the Summary and Recommendations section of this review.

Pre-Procedural Lumbar Neuraxial Ultrasound

Sidiropoulou and colleagues (2021) noted that a pre-procedural US of the lumbar spine is frequently used to facilitate neuraxial procedures.  In a systematic review and and meta-analysis, these researchers examined the available evidence on the use of pre-procedural neuraxial US compared to conventional methods.  They carried out a review of RCTs with meta-analyses.  These investigators searched the electronic databases Medline, Cochrane Central, Science Direct and Scopus up to June 1, 2019.  They included trials comparing a pre-procedural lumbar spinal US to a non-US-assisted method.  The primary endpoints were technical failure rate, 1st-attempt success rate, number of needle re-directions and procedure time.  These researchers retrieved 32 trials (3,439 patients) comparing pre-procedural lumbar US to palpations for neuraxial procedures in various clinical settings.  Pre-procedural US decreased the overall risk of technical failure (risk ratio (RR) 0.69 (99 % confidence interval [CI]: 0.43 to 1.10), p = 0.04) but not in obese and difficult spinal patients (RR 0.53, p = 0.06) and increased the 1st-attempt success rate (RR 1.5 (99 % CI: 1.22 to 1.86), p < 0.0001, numbers needed to treat [NNT] = 5).  In difficult spines and obese patients, the RR was 1.84 (99 % CI: 1.44 to 2.3; p < 0.0001, NNT = 3).  The number of needle re-directions was lower with pre-procedural US (standardized mean difference [SMD] = -0.55 (99 % CI: -0.81 to -0.29), p < 0.0001), as was the case in difficult spines and obese patients (SMD = -0.85 (99 % CI: -1.08 to -0.61), p < 0.0001).  No differences were observed in procedural times.  The authors concluded that a pre-procedural US provided significant benefit in terms of technical failure, number of needle re-directions and 1st attempt-success rate.  These effects of pre-procedural US scanning of the lumbar spine was more significant in a subgroup analysis of difficult spines and obese patients.

The authors stated that this systematic review had several drawbacks.  First, the included studies involved miscellaneous procedures and patients (e.g., obstetric, emergency room, surgical patients).  These researchers deliberately included the afore-mentioned procedures to broaden the sample of the analysis and increase the power of synthesis.  It was likely that this approach contributed to the observed heterogeneity.  Second, there was a lack of blinding among trials.  Some studies attempted to circumvent this problem; 3 studies performed an US of the lumbar spine in both study groups to blind patients on group allocation.  In the sham-US group, no skin marking was performed.  Nomura et al (2007) carried out skin markings for each group with different shapes, using an ultraviolet ink pen not visible without an ultraviolet light source, before randomization.  When the patient was randomized, then the investigator marked the desired puncture site with a visible pen according to the allocated group; thus, the operator of the lumbar puncture and the patient were both blinded to group allocation.  While blinding the operator performing the US was often impossible, there was no reason to avoid blinding the personnel and patients by means of a sham US in the control group.  Third, other potential sources of biases were related to the study design (e.g., pooling together midline and paramedian approaches).  Although the majority of studies used a midline transverse approach to the lumbar spine, 2 studies used a paramedian approach in the experimental group to perform spinal anesthesia.  In 2 studies, a pre-determined inter-space level (L5 to S1) was used for the experimental group compared to the best inter-space level palpated for the control group.  These investigators strongly believed that this negated one of the major benefits of pre-procedural US, which was the choice of the wider and better accessible intervertebral level insonated.

Spinal Ultrasound for the Management of Spinal Muscular Atrophy

In an observational study, Wu et al (2010) examined the value of quantitative US in patients with type-2 and type-3 spinal muscular atrophy (SMA).  A total of 25 patients with SMA (15 type-2, and 10 type-3) and 21 normal subjects were enrolled in this trial.  Strength of biceps brachii, wrist extensors, quadriceps, and tibialis anterior were measured with hand-held dynamometry.  Furthermore, these 4 muscles were studied with a standard US system using a 5-MHz probe, and luminosity values for each muscle and the overlying subcutaneous fat were obtained by subsequent image analysis.  A luminosity ratio (LR) for each muscle was calculated by dividing the muscle by the subcutaneous fat luminosity.  The LR and strength scores for all 4 muscles were averaged to provide a single summary value for each patient.  The LRs increased with disease severity: 1.27 +/- 0.26 for normal subjects, 2.43 +/- 0.78 for type-3 SMA, and 3.85 +/- 1.3 for type-2 SMA (p < 0.001).  Taking all the normal subject and patient data together, there was a good correlation between strength and LR (r = -0.711, p < 0.001).  There was also a moderate relationship between LR and strength in the patients with SMA alone (r = -0.588, p = 0.008), and, as expected, a non-significant relationship between LR and strength in normal subjects (r = -0.011).  The authors concluded that quantitative US has the potential of serving as a marker of SMA severity and may be useful in future clinical trials.  These researchers stated that although the focus of this study was on establishing quantitative US as a means of discriminating disease type, the next, more challenging question will be to examine if US is capable of detecting alterations in SMA disease severity over time.  If it is, it could provide a simple, non-invasive method for evaluating the effectiveness of treatment in future clinical trials.

The authors stated that this study had several drawbacks.  First, dynamometry measurements in children, especially young ones, could be unreliable; thus, the robustness of an association between an US parameter and the measured muscle strength needs to be interpreted cautiously.  Second, there was inevitable variation in the process of selecting the areas of subcutaneous fat and muscle for grayscale analysis.  These researchers tried to do this consistently and also carried out the entire analysis in a blinded fashion.  Third, it was possible that differences in US devices, transducer frequency, gain, compression, and time-gain compensation may affect the data.  Theoretically, variations in each of these US characteristics and settings could impact the image echo intensity.  Complicating these variations further was the fact that US systems calculate the echo intensity data via complex formulas that were often proprietary.  Furthermore, a higher frequency transducer may produce an image with differing echo intensity values when compared to a lower frequency transducer.  Therefore, additional studies, examining the robustness of these findings and whether they hold across a variety of US systems, would be useful.  Finally, these investigators restricted this study to only patients with type-2 and type-3 disease, and did not attempt to evaluate the most severely affected, younger patients (e.g., type-1), in whom US may also be useful.

Gonzalez and Hobson-Webb (2019) stated that neuromuscular US (NMUS) is becoming a standard element in the evaluation of peripheral nerve and muscle disease.  When obtained simultaneously to electrodiagnostic studies, it provides dynamic, structural information that could refine a diagnosis or identify a structural etiology.  NMUS could improve patient care for those with mononeuropathies, polyneuropathy, motor neuron disease (MND) and muscle disorders.  The authors concluded that although it is most commonly used in the diagnosis of focal neuropathies, the field of NMUS has expanded to include polyneuropathy, myopathy, and MND.  Moreover, these researchers stated that although the quality of US study was operator-dependent, the development of quantitative measures appeared promising in its ability to improve patient care.

Carroll and Simon (2020) noted that NMUS is a rapidly evolving technique used in neuromuscular medicine to provide complimentary information to standard electrodiagnostic studies.  NMUS provides a dynamic, real-time evaluation of anatomy that could change diagnostic as well as management pathways in peripheral nerve diseases.  These investigators described the current and future techniques used in NMUS and detailed the uses and developments in the diagnosis and monitoring of compressive, hereditary, immune-mediated and axonal peripheral nerve diseases, and motor neuron diseases (MNDs).  The authors concluded that improved understanding of current and novel NMUS techniques will provide increasing insights into the pathophysiology of peripheral nerve diseases, and comparisons with clinical, electrodiagnostic and histopathological characteristics is needed to clarify the roles of NMUS in the future.

Hannaford et al (2021) stated that neuromuscular US is rapidly becoming incorporated into clinical practice as a standard tool in the assessment of peripheral nerve diseases.  Ultrasound complements clinical phenotyping as well as electrodiagnostic evaluation, providing critical structural anatomical information to enhance diagnosis and identify structural pathology.  These investigators examined the available evidence supporting neuromuscular US in the diagnosis of compressive mononeuropathies, traumatic nerve injury, generalized peripheral neuropathy as well as MND.  The authors concluded that extending the sonographic evaluation of nerves beyond simple morphological measurements has the potential to improve diagnostics in peripheral neuropathy, as well as advancing the understanding of pathological mechanisms, which in turn will promote precise therapies and improve therapeutic outcomes.  In particular, these investigators noted that MNDs include amyotrophic lateral sclerosis (ALS), poliomyelitis, spinal bulbar muscular atrophy (SBMA or Kennedy’s disease), and SMA.  Diagnostic delay is a significant issue in these disorders, for instance in ALS the median time to diagnosis is 11.5 months after onset of symptoms.  In SMA, the emergence of disease-modifying therapy has generated the need for accessible, accurate, responsive, and reliable outcome measures; thus, US has clear potential to improve the diagnosis and monitoring of MNDs.  Moreover, these researchers stated that further development of quantitative measures, standardized protocols as well as consensus scoring frame-works will aid in widening the use of spinal US and may result in improved diagnosis of peripheral nerve diseases.

Furthermore, an UpToDate review on “Spinal muscular atrophy” (Bodamer, 2024) does not mention spinal ultrasound as a management option. 

---

References