Cauda equina compression in metastatic prostate cancer
- Raheel Shakoor Siddiqui 1,
- Manikandar Srinivas Cheruvu 1 , 2,
- Hamza Ansari 1 and
- Marck van Liefland 1 , 2
- 1 Department of Trauma & Orthopaedic Surgery, Royal Shrewsbury Hospital, The Shrewsbury & Telford Hospital NHS Trust, Shrewsbury, UK
- 2 Deparment of Trauma & Orthopaedic Surgery, Robert Jones & Agnes Hunt Orthopaedic Hospital NHS Foundation Trust, Oswestry, UK
- Correspondence to Mr Marck van Liefland; mvanliefland@nhs.net
Abstract
A 67-year-old man presented to his general practitioner with intermittent episodes of unilateral sciatica over a 2-month period for which he was referred for an outpatient MRI of his spine. This evidenced a significant lumbar vertebral mass that showed tight canal stenosis and compression of the cauda equina. The patient was sent to the emergency department for management by orthopaedic surgeons. He was mobilising independently, pain free on arrival and without neurological deficit on assessment. Clinically, this patient presented with no red flag symptoms of cauda equina syndrome or reason to suspect malignancy. In these circumstances, National Institute for Health and Care Excellence guidelines do not support radiological investigation of the spine outside of specialist services. However, in this case, investigation helped deliver urgent care for cancer that otherwise may have been delayed. This leads to the question, do the current guidelines meet clinical requirements?
Background
Sciatica is pain along the dermatomal pattern and distribution of the sciatic nerve and may be unilateral or bilateral.1 The incidence of having sciatica in a lifetime is between 13% and 40%.2
This differs from cauda equina syndrome (CES), which is a clinical emergency consisting of compression of the cauda equina with a constellation of motor and sensory neurological deficits respective to the level of pathology.3 It is a rare condition that has an incidence of 1 in 33 000 to 1 in 100 000 of the population of which only 19% of presenting cases are confirmed CES.4 5 It has a significant impact on quality of life (QoL) as a result of morbidity. CES may present as acute lower back pain (LBP) with altered bowel and/or bladder control anal motor and sensory deficits with or without lower limb neurological compromise.4 5 There is considerable variation in both the frequency and severity of symptoms that predisposes a more challenging diagnosis.6 Given the drastic complications mainly affecting the QoL of the patient, there is potential for medicolegal implications.7 Assessment and management of CES involves a multidisciplinary team (MDT) approach including physicians from primary care, emergency department, orthopaedics, spinal surgeons and pain experts.8 Urgent surgical decompression of the spinal canal is treatment of choice for confirmed CES.9
Red flag symptoms of CES include new LBP, bilateral sciatica, saddle anaesthesia, bowel, bladder or sexual dysfunction.7 10 This would warrant the application of a streamlined pathway of referral from admission to discussion with a spinal unit for further investigation to determine the underlying cause including urgent MRI of the spine.11 The aetiology of CES and sciatica can be classified into common and uncommon as shown in table 1.
Aetology of cauda equina syndrome and sciatica
| Common causes | Uncommon causes |
|---|---|
Lumbar disc34:
Spinal canal stenosis.34 |
|
Case presentation
A 67-year-old man presented to his general practitioner (GP) with intermittent episodes of unilateral left-sided sciatica over a 2-month period. The patient denied any change in bowel habit, urinary retention or incontinence symptoms and did not present with any constitutive symptoms of malignancy. Following assessment by his GP, he was referred for MRI of the lumbosacral spine. His routine outpatient scan evidenced concerning pathology such that he was immediately transferred to the emergency department and referred onwards to the on-call Trauma & Orthopaedics team as is the protocol at our hospital.
On examination, the patient was comfortable both at rest and while mobilising independently. There were no red flag symptoms of CES, an unremarkable neurological motor and sensory examination in the upper and lower limbs bilaterally, normal gait, no spinal tenderness and an unremarkable digital rectal examination concluded good anal tone, good sphincter control with no saddle, perianal or genital anaesthesia. A prevoid bladder scan showed approximately 311 mL, but postvoid bladder scan was not performed as patient had normal flow sensation and no difficulty in voiding urine. Review of MRI presented a large space occupying lesion at the level of lumbar 4 (L4) arising from the posterior aspect of the vertebral body with severe canal stenosis and the lesion displacing the cauda equina as shown in figure 1.
MRI spine lumbar and sacral T2 sagittal view portraying tight spinal canal stenosis at the level of L4 vertebrae caused by a space-occupying lesion (arrow) arising from the posterior aspect of the L4 vertebral body extending down to the back of L5 vertebrae. L4, lumbar 4; L5, lumbar 5.
The patient’s medical history consists of hypertension controlled on amlodipine. He is a non-smoker, non-drinker and is independent with activities of daily living with no positive family history of malignancy.
This clinical history would not warrant imaging of the spine as per National Institute for Health and Care Excellence (NICE) guidelines. However, MRI showed significant compression of the cauda equina, which one would typically associate with severe symptoms of CES.
Investigations
This patient had an elevated prostate-specific antigen (PSA) of 97 µg/L; therefore, the urology team proceeded with a transrectal ultrasound-guided prostate biopsy of which histology report confirmed adenocarcinoma of the prostate, Gleason score 4+4 on the left prostate gland. Staging: T3, N0, M1b (tumour3, node0, metastasis1b).
In addition, he had staging CT of the thorax, abdomen and pelvis to further investigate for malignancy. Spinal views of the CT confirmed the space occupying lesion as shown in figure 2. This also showed a solitary 6 mm size right middle lobe lung nodule and hypodense area in the liver. These findings were discussed in the uro-oncology MDT; it was determined that these findings were insignificant, and there was no evidence of metastases to other areas of spine. He also had a nuclear medicine whole body bone scan that reported increased activity within the L4 vertebral body keeping with known metastatic deposit as shown in figures 3 and 4.
MRI spine lumbar and sacral T2 axial view of L4 vertebral body (arrow) indicating a space-occupying lesion causing compression of the cauda equina nerve roots. L4, lumbar 4.
CT sagittal view of spine part of the staging CT series showing multilevel degenerative changes noted in spine and an ill-defined mixed lytic sclerotic bone lesion (arrow) involving L4 vertebral body with destruction of posterior cortex. L4, lumbar 4.
NM whole body bone scan anterior view showing an area (arrow) of increased activity within the L4 vertebral body in keeping with known metastatic deposit. L4, lumbar 4; NM, nuclear medicine.
NM whole body bone scan posterior view showing an area (arrow) of metastatic deposit at the L4 vertebral body. L4, lumbar 4.
Differential diagnosis
The final diagnosis of prostate cancer with metastasis to the spine was confirmed with CT and MRI as shown in figures 1, 2 and 5 as well as histological analysis from the prostate tissue. The man presented with a short course history of intermittent episodes of unilateral sciatica to his GP. We have described a multitude of differentials related to CES and sciatica (table 1), although the clinical history does not definitively support a particular differential. Given the mild and intermittent nature of symptoms one would not expect significant pathology, indeed it is unlikely that he would be investigated prior to conservative treatments such as physiotherapy.
Treatment
A diagnosis of prostate adenocarcinoma with spinal metastasis was concluded from the MDT assessment. Following comprehensive discussion and counselling with the patient, the decision was made to pursue palliative non-operative treatment. The patient was placed on oral bicalutamide, a non-steroidal antiandrogen 50 mg once a day for 28 days and monthly goserelin subcutaneous injections, a gonadotropin-releasing hormone (GnRH) agonist treatment for metastatic prostate malignancy.14 15 Acute oncology services commenced oral dexametasone for inflammation and oedema control around spinal metastasis however gradually tapered this regime after 1 month of treatment.16 He received palliative radiotherapy of 20 grays (gy), which was delivered in five sessions over five consecutive days to the lumbar 3–sacral 1 vertebral bodies.
Outcome and follow-up
The patient experienced a resolution of episodes of sciatica after palliative radiotherapy, and the following stage of treatment would include chemotherapy with docetaxel (synthetic taxane). PSA had reduced to 7.3 µg/L after 2 months of antiandrogen and GnRH treatment. Given the global pandemic of SARS-CoV-2 (ie, COVID-19) and risk of immunocompromise following chemotherapy, the decision was made to defer treatment. Following discussion with the patient and his family, it was decided that he would continue with the bicalutamide and GnRH injection treatment with PSA monitoring. Follow-up was arranged for 3 months to discuss treatment options depending on the COVID-19 situation.
Discussion
CES is a surgical emergency, and delay in treatment can lead to significant morbidity and impairment to quality of life.17 LBP or unilateral leg pain can be diagnosed as sciatica and is not routinely investigated in the community unless there is a progressive neurological deficit, worsening symptoms, trauma or suspicion of malignancy.18 Suspected CES with red flag symptoms under current guidelines indicates the need for urgent imaging with access to a local 24-hour MRI scanning service and immediate decompressive surgery where there is benefit in long-term morbidity.19 20
This case is an unusual presentation to acute services with non-specific intermittent symptoms and a chance radiological result. The patient’s symptoms did not warrant an urgent MRI of the spine to rule out cauda equina compression due to the lack of classic red flag symptoms. The two important non-specific red flags in our case would be the patient’s age and symptoms lasting more than 6 weeks.
Back pain does not necessarily arise from tissue destruction rather when that tissue collapses, fractures, becomes ischaemic or causes nerve compression (neurogenic claudication). If the spine is stable and vertebral bodies, pedicles, posterior elements are in balance, it is not necessary to have back pain in CES.21 Studies have shown that up to 30% of patients with true CES do not present with LBP.22 Many patients who present with large metastasis of the spine or elsewhere are picked up as incidental findings as well.23 24
Based on current knowledge and literature, we suggest that non-specific intermittent symptoms without neurological deficit may be due to a radiological displacement of the nerve roots from a sinister pathology rather than complete obliteration. MRI is useful to identify cord changes due to the size; however, it cannot identify pressure or ischaemic changes within the nerve root. Another hypothesis could be the soft consistency of the tumour itself pushing against nerve roots but not necessarily compressing them. The decision to undertake an MRI scan was made purely on clinician intuition and diagnosed a life-changing pathology for this patient.
Despite having a large metastic lesion at his L4 vertebral body with complete compression of the cauda equina, this patient did not experience neurological deficit and immobility and remained fully active with no consitutional symptoms of cancer. Given his MRI results, we would expect symptoms of unilateral or bilateral sciatica, profound lower limb neurological motor and/or sensory deficit, urinary incontience or retention and bowel or sexual dysfunction. The most common presentation of CES is back pain and sciatica in 97%, saddle anaesthesia in 93%, bladder incontinence or retention in 92% and bowel incontinence or retention in 72% of patients.25 Symptoms such as bowel or urinary dysfunction and saddle anaesthesia are most commonly associated with MRI findings of compression.26 A systematic review showed that around 32% of cases with ‘red flag symptoms’ were of patients with confirmed irreversible CES.10
There are a multitude of unusual presentations of CES case reports in literature. One particular case presented with painless urinary retention but no signs or symptoms of any lower limb neurological deficit.27 Another case of CES secondary to lumbar disc herniation presented with saddle anaesthesia and bowel incontinence but again no significant lower limb neurological compromise.28 The unique feature in our article is the intermittent presentation of this patient to acute services with absence of any neurological, bladder or bowel dysfunction that would not draw undue concern under most circumstances. Another similar case was described by Nagaria et al secondary to intradural disc herniation at lumbar 5–sacral 1 of a 53-year-old man with no pain and intermittent symptoms.29 There are no other cases of intermittent CES clearly reported. Furthermore, there are many published cases of patients with CES and cancer as the underlying pathology; however, these have been true CES and not intermittent CES.30–33
The key learning point is that unexplained LBP and/or sciatica symptoms may warrant imaging, although this is not currently recommended under NICE guidance. Guidelines are produced based on evidence from randomised prospective clinical trials and cannot always include and cover all individual patient presentations. This case emphasises and demonstrates the importance of the clinician’s intuition where guidance would have failed the patient. A thorough clinical history and examination may provide some guidance although as in this case may not be indicative of pathology. We suggest a low threshold for radiological assessment of unexplained LBP/sciatica as early diagnosis and possible intervention can be life changing.
Learning points
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Compression of the cauda equina may not always present with red flag symptoms.
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It is never too early to investigate for cauda equina syndrome (CES) as patients presenting with red flag symptoms may already have irreversible CES.
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Urgent MRI scanning is essential in early diagnosis, treatment and prognosis in patients with compression of the cauda equina.
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As of yet, there is no validated quantitative measuring score or tool that can help assesing physicians determine the urgency in MRI of the spine to confirm CES.
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As per current National Institute for Health and Care Excellence guidelines, unilateral sciatica does not warrant an MRI of the spine unless in a specialist centre.
Footnotes
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RSS and MSC are joint first authors.
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Twitter @DrKingKong_
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Contributors I, RSS, first author contributed to the patient consent, planning, conduct, write up, editing, final review and revision of the case report. MSC contributed to the planning, write up, editing, final review and revision of the case report and would be a joint first author. HA contributed by providing anonymised radiological images with arrows, relevant clinical information from the hospital system and was involved in reviewing the write up and would be third author. MvL contributed by reviewing, editing the write up, providing expertise, advice, final review, revision and supervising the case report and is the corresponding author.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Competing interests None declared.
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Patient consent for publication Obtained.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.
References
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