Spinal Red Flags

Spinal Red Flags

Sinister pathologies of the spine, aka red flags. Now, if reading that sentence sent shivers up your back like uttering the word ‘Lord Voldemort’ in a HPaz film, this blog might be for you. Fortunately, red flags account for <1% of all low back pain (LBP) (1) so for the vast majority we can apply the maxim of Dr Theodore Woodward, “when you hear hoofbeats, think of horses, not zebras”. However, this potentially means 1/100 LBP cases could be a sinister pathology and with LBP being the leading cause of disability worldwide to which patients seek healthcare advice, clinicians should take the trouble to learn about these red flags (or zebras) (2,3). 

For the purpose of this blog, I will discuss four sinister pathologies associated with LBP. But before that, what exactly is a red flag? Currently, there are 163 signs and symptoms designed to raise our ‘suspicion’. Although, when considered in isolation, they lack any robust diagnostic utility (4). So, what should we do? Well, clusters of features might increase the probability, but this still lacks validation across each of the four pathologies (4,5,6,7). Their limited accuracy appears to be a running theme as >90% of almost ten thousand patients said yes to at least one red flag screening question, yet only 8% had a formal diagnosis (5). So, join me as I attempt to improve your knowledge towards identifying them.      

Vertebral Compression Fractures (VCF’s) 

VCF’s account for 1-4.5% of acute back pain cases with an annual incidence of 120,000 per annum in the United Kingdom (8,9). Early detection is challenging because up to 75% are asymptomatic. This is a problem because VCF’s correlate with significant morbidity, their presence is a marker for osteoporosis which requires further diagnostic work-up and they increase the risk of future fragility fractures (10). Currently, there are no robust diagnostic features which can help screen for VCF’s, and care must be taken to avoid unnecessary overreliance on imaging/further investigations to accommodate for this (8). For those who are symptomatic, patients usually present with a sudden onset of localised pain in the thoracolumbar region which requires strong analgesia (4). Additional clues are, 

•      Older age, especially in those over seventy. 
•      Comorbidities such as cancer, osteoporosis and vitamin D deficiency. 
•      Excessive alcohol intake, smoking and steroid history. 
•      Trauma. Often innocuous, think sneezing, bending, lifting mechanisms. 

Spinal Metastases  

These are cancer lesions which spread from the primary cancer site to a different area (bone being a common source). With regards to the spine, approximately 70% metastasise in the thoracic region (4) and this is because of its large vasculature network known as the Venous Bastons Plexus which promotes haematogenous spread. A useful acronym to remember the most common primaries which have a predilection towards bone (especially if you are a James Bond fan) is the following, 

1.      Piers – prostate 
2.      Brosnan – breast 
3.      License – lung 
4.      To – thyroid 
5.      Kill – kidney 

Confidently detecting metastatic bone disease (MBD) is a challenge. However, a history of cancer does have the highest post-test probability (6). Weight loss is a feature drilled into us at university when screening, but often the answer is vague and the cause multifactorial.  Spinal pain is often the presenting complaint. This occurs due to osteolytic lesions which form within the bone and their associated inflammation (11). Deciphering this from mechanical LBP can be challenging. Symptoms are rarely linear, instead they may wax and wane, but take heed in those with deteriorating pain which is non-mechanical, nocturnal and have a low threshold for referring these on.  Metastatic cord compression can be a consequence of MBD secondary to insufficiency fractures or the tumour encroaching onto the spinal cord (4). Thorough screening for neurological and autonomic changes is vital and if present, is treated as an oncological emergency with same day assessment at A/E (12). 

Cauda Equina Syndrome (CES) 

CES has a prevalence of 1-3 per 100,000 back pain cases and is the result of compression towards the 20 caudal nerve roots, usually secondary to a large, central disc herniation (13). There are four cardinal symptoms which may occur due to injury towards the S2-5 nerve roots and be mindful we do not need a full house to have CES, one is sufficient! These are, 

1.      Bladder Dysfunction 
2.      Bowel Dysfunction 
3.      Sexual Dysfunction 
4.      Saddle Anaesthesia 

With regards to presentation, there is no set menu. LBP and radicular symptoms are common tagalongs, but saddle anaesthesia and bladder dysfunction are the most frequently associated with radiologically confirmed CES (14,15). Remember, symptoms such as incontinence and retention are late-stage manifestations of the syndrome which has worse prognosis. It is vital we pick up earlier symptoms and a useful acronym described by Tom Jesson and Rob Tyer to screen for earlier bladder dysfunction is ‘FFS’, 

•      Flow 
•      Frequency 
•      Sensation 

We can classify CES into stages too. 

CES Suspected 

•  Associated solely with bilateral radicular symptoms in the lower limb. 

CES Incomplete 

•      Usually earlier, more subtle changes towards the bladder +/- saddle sensation. 

CES Retention 

•     Insensate bladder. Other CES symptoms are likely to progress as well. 

CES Complete 

•     Complete loss of function of all caudal nerve roots 
•     These are considered ‘White Flags’, meaning changes are likely to be irreversible (also a great song by Dido, IYKYK) (16).  

Spinal Infections 

These are a rare cause of LBP, often because of a primary pyogenic spondylodiscitis that has a preponderance towards the lumbar spine (4). The majority tend to have a prodromal period early doors which make them difficult to detect but consider a triad of features (17). 

1.      Spinal Pain 
2.      Fever 
3.      Neurological Symptoms 

Some caveats. Fever is a late-stage symptom and is detected in approximately half of patients. Neurological signs are rarer, they present in only a third and would indicate the infection has spread posteriorly into the epidural space (aka big problemo) (17). The complexity lies with the fact people can remain healthy until the latter stages of the disease. Earlier detection is paramount, and this is where our subjective questioning is vital. Consider asking about, 

•     Travel history to lower income/tropical countries 
•     Recent spinal surgery 

Comorbidities (obesity, poorly controlled diabetes and immunosuppression) 

•      History of intravenous drug use 
•      Environmental factors 

If you have someone with spinal pain that is worsening and appears non-mechanical accompanied with some of these risk factors, have a low threshold for further investigation. 

To conclude, sinister pathologies of the spine are rare! Hopefully this blog has provided a flavour towards some of the key features we can screen for. Remember, clusters > single features 99% of the time. A higher level of concern warrants onwards referral and investigation, so awareness of your local pathways is paramount to ensure treatment is not delayed and if in doubt, liaise with someone more senior! I will leave you with this excellent tool by Finucane and colleagues (2020) to help guide your decision-making in these scenarios. 

Reference List 

1.  Maher, C., Underwood, M. and Buchbinder, R. (2017) Non-specific low back pain, The Lancet, 389(10070), pp. 736-747. 

2.  Ferreira et al., (2021) Global, regional and national burden of low back pain, 1990-2020, it’s attributable ri. sk factors and projections to 2050: a systematic analysis of the Global Burden of Disease Study 2021, The Lancet Rheumatology, 5(6), pp. 316-329. 

3.  Dickinson, J.A. (2016) Lesser-spotted zebras, The College of Family Physicians of Canada, 62(8), pp. 620-621. 

4.  Finucane et al., (2020) International framework for red flags for potential serious spinal pathologies, JOSPT, 50(7), pp. 350-372. 

5.  Premkumar et al., (2018) Red flags for low back pain are not always really red, The Journal of Joint and Bone Surgery, 100(5), pp. 368-374. 

6.  Downie et al., (2013) Red flags to screen for malignancy and fracrture in patients with low back pain: systematic review, The BMJ, pp. 1-9. 

7.  Henschke et al., (2009) Prevalence of and screening for serious spinal pathology in patients presenting to primary care settings with acute low back pain, Journal of Arthritis and Rheumatism, 60(10), pp. 3072-3080. 

8.  Williams et al., (2023) Red flags to screen for vertebral fracture in patients presenting with low-back pain, Cochrane Library, vol 11, pp. 1-46. 

9.  Musbahi et al., (2018) Vertebral compression fractures, British Journal of Hospital Medicine, 79(1), pp. 36-40. 

10.  Razi, A.E. and Hershman, S.H. (2020) Vertebral compression fractures in osteoporotic and pathologic bone: A clinical guide to diagnosis and management, Springer Nature Switzerland, pp. 1-233. 

11.  Coleman, R.E. (2006) Clinical features of metastatic bone disease and risk of skeletal morbidity, Clinical Cancer Research, 12(20), pp. 6243-6249. 

12.  NICE Guidelines, (2023), Spinal metastases and metastatic cord compression, Available at; Overview | Spinal metastases and metas tatic spinal cord compression | Guidance | NICE 

13.  Woodfield et al., (2023) Presentation, management and outcomes of Cauda Equina Syndrome up to one year after surgery, using clinician and participant reporting: a multi-centre prospective cohort study, The Lancet, vol 24, pp. 1-16. 

14.  Korse et al., (2017) Cauda Equina Syndrome: presentation, outcome and predictors with focus on micturition, defecation and sexual dysfunction, European Spine Journal, vol 26, pp. 894-904.