Diagnosis of spinal pain in the clinic using SPECT/CT: A personal journey, current evidence and clinical applications

By Mark Miller

Mark Miller is an independent pain management consultant retired from clinical practice as of end 2024. He continues to provide pain medicine medico-legal reports and is an Associate of the Faculty of Forensic & Legal Medicine of the Royal College of Physicians.

Introduction

Chronic back pain is by far the most common presentation in the pain management clinic. I write this article from a somewhat historical perspective when the first person the patient saw in the clinic was a doctor in a hospital outpatient clinic. The more common scenario now after GP referral is a first assessment by a physiotherapist in a musculoskeletal clinic in the community. Pain management clinics in the NHS are fewer and fewer. Orthopaedic spinal clinics however continue and are therefore faced with the same issues that pain clinics were, including the complication of added biopsychosocial issues often previously filtered by pain clinics and now missed by community-based clinics.

In the pain clinics I worked in, both independently and in the NHS, issues of acute pathologies secondary to infection, instability and cancer had almost always been excluded by others, as had any possible operative intervention. Diagnosis frequently remained elusive, however occasionally a first MRI ordered by the pain clinic could find evidence of instability with pars interarticularis defects and subsequent spinal clinic referral was warranted.

The lack of diagnostic sensitivity and specificity using X-rays, MRI and CT scans to find the cause of mechanical spinal pain can be evidenced from the way pain clinicians historically used diagnostic and therapeutic injections en masse despite the results of such investigations to hand. The failure of pain clinics to audit these treatments for long-term outcomes may be a part of the reason funding has reduced in secondary care. Another major reason is the loss of interest in a career in management by trainees. Many of these clinics have disappeared as a result with funding diverted to the non-hospital environment given the supporting evidence base for community based functional restoration programmes¹.

Further issues arise with repeated spinal steroid injections sometimes no matter what. In addition to cost, this can reinforce a medical causation in the sufferer with a significant psychosocial input to their presentation, failure to help because the wrong site has been injected and the inherent risks of needling the spine. In my own practice, I found nothing more frustrating than failed injections until I happened across SPECT-CT scanning.

The first SPECT-CT scan of one of my patients was one of the most pivotal points of my career. The case itself was serendipitous. An employed family man with health insurance (he was first seen in the NHS) in his twenties presented with significant mechanical lumbar back pain, yet his MRI scan was completely normal. I sent a general enquiry to the radiology department, asking if there were any further investigations they could perform that might provide an answer. One month later, I had one. A SPECT-CT scan revealed significant L5 endplate (disc) inflammation where no abnormality had been seen on his MRI. I tried L5 transforaminal root blocks, but they failed to provide any short-term relief (I will discuss this later). Ultimately, he underwent a spinal fusion, which he reported to me at follow-up a few months later, had helped his pain greatly. The Spinus 1 Study² published in 2023 involved single level fusion in 38 patients after SPECT-CT positive findings and noted a substantial clinical improvement and satisfaction with treatment.

I approached the nuclear medicine radiologist after I had received his report on the scan. Soon I was ordering SPECT-CT scans very frequently. Radiology reports were picking out particular facet, sacro-iliac and endplate inflammatory changes. My clinical experience following subsequent treatment was to trust the moderate and marked changes as significant. This means that unlike X-ray, CT and MRI, SPECT-CT is as good as it gets in unearthing active inflammatory changes when other investigations are equivocal or negative.

Following this discovery, I ordered dozens of SPECT-CT scans in my clinics. With the positive scan results, I then injected steroid in and around the abnormalities with impressive short-term outcomes reported at follow-up. The only available assessment of longer-term outcome related to whether they returned to the clinic after discharge.

The cost of SPECT-CT is (far) greater than MRI. In the NHS, this became a factor in managerial discussions and as often happens in such a scenario, they were ‘redlined’ and stopped without discussion. This had the positive effect of my subsequent evaluation of who would benefit from a SPECT-CT in addition to an MRI and with the passing years, I honed this to offering them to a few select paying patients. MRI and scans and a careful history do most of the work, a SPECT-CT is a valuable conclusion in a few.

Principles of SPECT/CT

This a two-in-one scan. It combines:

SPECT (Single Photon Emission Computed Tomography) — shows function by detecting a tiny amount of radioactive tracer in the body.

CT (Computed Tomography) — shows structure by taking detailed X-ray pictures of anatomy.

After injection of a radioactive tracer, Technetium 99 in spinal studies, it is preferentially taken up in greater quantities by actively dividing osteoblastic bone cells. A gamma camera picks up signals from the tracer, the SPECT part. A low voltage CT scan follows and a computer merges the two. The report will usually describe the level of activity as mild, moderate and marked or avid.

Clinical indications for SPECT/CT in back pain

Unlike X-ray, CT and MRI, SPECT-CT appears to be the most sensitive radiological investigation for active inflammatory changes when other investigations are equivocal or negative. Discussion with radiology colleagues informed me it is important to caution that SPECT can be positive and provide red herrings for around two years after uncomplicated surgical intervention.

I used these scans to help with diagnosis for some 20 years, not just in spinal pain but also in peripheral musculoskeletal complaints. I subsequently referred these patients onto orthopaedics and rheumatology with irrefutable evidence of pathology.

These scans were now providing me with definitive proof of the causes of mechanical back pain in individual patients. In real time, they uncovered active degeneration in

• Facet joint arthropathy
• Sacroiliac joint dysfunction
• Pars interarticularis defects (spondylolysis)
• Vertebral fractures (acute vs. old)
• Pseudarthrosis after spinal fusion
• Discogenic pain

As I have already described, it was discogenic mechanical lumbar pain that my first patient had and for me was the most revelatory. The inflammatory changes are seen in the endplates. It was a proof to me this can occur without a referred radicular element. Although supporting evidence³ using selective nerve root blocks supports this finding, it was following this discovery that I started to use these blocks in a therapeutic manner. I found the greater the level of uptake the greater the subjective response. The root blocks in turn appeared only to work if an MRI found annulus fibrosis changes and, along with the history and examination, excluded most of the presentation as degenerative with co-existent spinal morphological changes and neurogenic claudication.

From a cautionary perspective, I have found that a negative SPECT-CT does not mean symptomatic degeneration is absent. An intervertebral disc with an annular tear can be symptomatic and respond to a root block without associated bony endplate changes. Sacro-iliac joints, the largest surface area synovial joints in the body can be symptomatic from a synovitis without underlying bony involvement. I have never diagnosed Coccydynia from a SPECT-CT; this has always been a clinical presentation.

A final point is the de novo diagnosis of autoimmune, seronegative and gouty spondyloarthropathy by these scans when none had been considered or previous blood tests and investigations were equivocal. Basra et al.⁴ looked at MRI and PET-CT (rather than SPECT-CT) imaging to evaluate patients with known spondyloarthropathies and sacro-ileitis and concluded PET-CT was another option when focusing on detecting early inflammation and bone remodelling changes because it has a greater ability to detect erosions, sclerosis, and ankylosis.

Diagnostic accuracy

CT, MRI and SPECT-CT differ in anatomical detail, functional information, radiation exposure, and clinical suitability:

CT excels in fast acquisition and high-resolution bone/structural imaging but lacks patient-specific data in the atraumatic scenario.

MRI offers superior soft-tissue contrast without ionising radiation, but acquisition is slower and more expensive.

SPECT-CT combines nuclear medicine functional imaging (SPECT) with anatomical localisation from CT, making it valuable for functional–structural correlation. The CT component is low voltage.

Evidence-base

My own clinical findings are generously supported by published evidence.

Carstensen et al.⁵ published a case report on SPECT-CT imaging of the lumber spine in a chiropractic journal. They found a hot lumbar facet joint and concluded the ability of these scans to precisely localise metabolically active facet joints may provide direction of treatment to manual therapies focused on improving spinal function.

Harisanker et al.⁶ concluded all patients with low back pain are likely to have some MRI abnormality and most are likely to have MRI abnormalities at multiple sites. Addition of SPECT/CT is invaluable in differentiating significant from incidental non‑significant findings on MRI.

Matar et al.⁷ performed cervical and lumbar SPECT-CT scans in 72 people. Hybrid SPECT/CT imaging identified potential pain generators in 92% of cervical spine scans and 86% of lumbar spine scans. The scan precisely localised SPECT positive facet joint targets in 65% of the referral population and a clinical decision to inject was made in 60% of these cases.

Malham et al.⁸ looked at SPECT-CT in diagnosis of discogenic pain. They stated in the identification of disk pathology, it is reasonable to use either conventional bone SPECT or bone SPECT-CT; however, bone SPECT-CT is more reliable for facet joint pathology. The support for facet joint pathology diagnosis is supported by Shur et al.⁹ and Oosterwyck et al.¹⁰.

Kim et al.¹¹ published a review of diagnostic technology for spine pathology. They noted “Studies have shown that SPECT/CT can be a useful diagnostic method for detecting spinal diseases, including malignant tumors, active phases of arthritis, minor trauma, infections, pseudoarthrosis, and postoperative pain caused by minor factors.”

Hirsch et al.¹² published “Applications of SPECT/CT in the Evaluation of Spinal Pathology: A Review”. They concluded, “SPECT/CT is a promising imaging modality in the evaluation of low back pain, particularly in cases where magnetic resonance imaging and CT are inconclusive or equivocal. However, the current level of evidence is limited, and additional research is needed to determine its overall clinical relevance.”

Yang and Chang¹³ performed a retrospective analysis of 102 patients who had intra-articular facet joint corticosteroid injections between March 2010 and December 2020. Patients were stratified into two groups based on bone SPECT findings: 60 with increased cervical facet radiotracer uptake and 42 without. Pain intensity was assessed using the numeric rating scale (NRS) before treatment and at the one-month follow-up. Treatment success was defined as a ≥50% reduction in NRS scores. Statistical analyses were performed to compare outcomes between groups.

They found both groups exhibited a significant pain reduction following injection (P < 0.001 for both groups). However, the SPECT positive group demonstrated significantly greater pain relief compared to the SPECT negative group at one-month follow-up (P = 0.007). The treatment success rate was significantly higher in the SPECT positive group (63.3%) than in the SPECT negative group (38.1%) (P = 0.012).

They concluded bone SPECT is a valuable imaging modality for predicting the therapeutic efficacy of intra-articular corticosteroid injections in patients with cervical facet joint pain. The findings suggest that increased CFJ radiotracer uptake is associated with a greater likelihood of achieving significant pain relief, underscoring the potential role of inflammation in treatment response.

Conclusion

My clinical experience of using SPECT-CT scanning to aid diagnosis of mechanical spinal pain is of it as an invaluable tool. This is supported by the positive evidence base that I have described. Nothing beats the basics of history and examination, but I found SPECT-CT revelatory when I discovered it and ever since. Against it is that it is expensive and not universally available; I attempted to find somewhere in Scotland a few years ago that would perform a private scan and had to give up. I have however never had a patient who regretted paying for one. My hope is this article will add to the armamentarium of clinicians who deal with patients with mechanical spinal pain. It should not be overlooked that it is useful throughout musculoskeletal practice and I have used it personally for investigation of chronic pain in other bodily presentations.

References

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2. Kaiser R, Varga M, Lang O, Waldauf P, Vaněk P, Saur K, et al. Spinal fusion for single-level SPECT/CT positive lumbar degenerative disc disease: the SPINUS I study. Acta Neurochir (Wien). 2023;165(9):2633-40.
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