Tophaceous spinal gout in a young man with complete spinal cord injury

Abstract

Gout is a common inflammatory arthritis, caused by monosodium urate crystal deposition in the joints. Gout typically affects peripheral joints but less commonly it affects the spine. We report a case of a man in his 30s with chronic gout who presented acutely with thoracic back pain and flaccid paralysis of his lower limbs. CT showed abnormal facet joints at T8/9 with lucency suggestive of septic arthritis and MRI showed signal changes suggestive of epidural collection. The patient underwent emergency spinal surgery to evacuate the collection, followed by broad-spectrum antibiotic treatment. Cultures were negative; however, histopathology was suggestive of gout tophi. The patient was subsequently treated for spinal gout with prednisolone, allopurinol and colchicine and saw significant improvement in symptoms though he sustained a complete spinal cord injury. This case demonstrates that spinal gout is an important differential to consider in patients with chronic gout, presenting with acute back pain.

Background

Gout is a form of inflammatory arthritis that develops from sustained hyperuricaemia and subsequent deposition of monosodium urate (MSU) crystals. It is the most common form of inflammatory arthritis worldwide. In the UK, it has a growing disease burden, evidenced by a 63.9% increase in prevalence over a 15-year period (1997–2012).¹

In >90% of patients, gout is due to reduced clearance of uric acid rather than increased synthesis.² As such, risk factors for gout are often related to the mechanics of physiological urate clearance, such as chronic kidney disease and diuretic use. It is reported with higher prevalence in men, the elderly and certain ethnic groups such as Han Chinese, New Zealand Māori and African Americans.³

While gout is a chronic disease with a wide spectrum of sequelae and clinical manifestations, the typical initial presentation is an acute ‘flare’, of pain, fever and monoarticular inflammation of a peripheral joint, commonly the first metatarsophalangeal. Less commonly, gout affects the axial joints—the sacroiliac joint and the spinal vertebrae, with up to 35% prevalence in those with chronic gout.⁴ Tophi formation can also occur during chronic gout, which is a result of the body’s inflammatory response to MSU crystals, leading to granuloma formation.

An important differential diagnosis to rule out for patients with suspected gout is septic arthritis as it can present identically to acute gout. Both pathologies are known to acutely demonstrate elevations in inflammatory markers such as white cell count (WCC), erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) which present diagnostic uncertainty. The gold standard for diagnosis is synovial fluid aspiration and microscopy analysis for the presence of MSU crystals. Serum urate level can also be measured, though it is not diagnostic especially among patients on urate lowering therapy.

Case presentation

A man in his 30s presented to his local emergency department with acute-onset thoracic back pain and flaccid paralysis of his lower limbs. He was assessed by the medical team in his local emergency department, who performed a neurological examination and found MRC grade 0/5 power in all lower limb myotomes bilaterally, absent lower limb reflexes and reduced sensation with a T11 sensory level. He was also found to be in painless urinary retention with a prevoid bladder scan result of 800 mL and was thus catheterised.

The patient’s medical history includes a 10-year history of gout with peripheral cutaneous tophi, obesity and asthma. His alcohol consumption was estimated at 12–15 units per week, and he drank one sugary carbonated drink per day. His gout history incorporated polyarticular flare-ups affecting his hands, elbows, knees, ankles and first metatarsophalangeal joints, which he self-managed with colchicine and non-steroidal anti-inflammatory analgesics. Prior to this presentation, the frequency of flares had increased notably in the preceding 12 months. His first-ever treatment with urate lowering medication, allopurinol 100 mg once a day, commenced 1 month prior to this presentation. Otherwise, he was prescribed a salbutamol inhaler which he used as required for asthma.

Initial investigations at the emergency department revealed a serum WCC of 8.6 (3.5–9.5), CRP 134 (0–5) and normal renal function. Plain CT of the thoracolumbar spine was performed which showed abnormal facet joints at T8/9 with evidence of erosion which prompted suspicion of septic arthritis(figure 1).

Figure 1.

CT thoracolumbar spine showing T8/9 facet erosive lucency (arrow mark refers to erosive lucency).

The patient had an acute flare of gout 1 week prior to presentation to the emergency department. He experienced a painful, swollen and red left elbow-and-hand. He managed this episode with naproxen and colchicine. A few days later, he developed ‘dull’ character mid-thoracic back pain which persisted for several days, followed by right lower limb sciatica which worsened on weight-bearing. Overnight, the patient noticed his legs becoming numb and that he was beginning to lose power in his lower limbs which led to his presentation to his local emergency department via ambulance.

Treatment

The patient was referred to our regional neurosurgery centre for further management. MRI examination was not possible at the patient’s local hospital because the patient was too wide to fit within their standard MRI bore. Therefore, urgent CT of the thoracolumbar spine was performed locally prior to transfer.

MRI lumbosacral spine examination was performed on admission to our neurosurgical unit, using the wide bore scanner available at our regional neurosurgery centre. There was evidence of cord signal change at T8/T9, and high T2 signal surrounding the cord at T8–T10 suggestive of an epidural collection(figure 2). The patient underwent an emergency T8–T10 posterior thoracic decompression and epidural collection evacuation. The aim of the operation was to prevent further neurological deterioration, aid with potential recovery and elicit diagnosis of the compressive lesion. Intraoperatively, white ‘cheese-like’ substance was evacuated. This material was sent for further histopathology and microbiology analysis.

Figure 2.

T2-weighted MR showing T8/9 cord signal change with high T2 surrounding cord suggestive of epidural collection.

Postoperatively, the patient was treated as a spinal epidural abscess with input from the infectious diseases and microbiology physicians. He was initially treated empirically with intravenous flucloxacillin 2 g four times per day and intravenous ceftriaxone 2 g four times per day.

Initial gram film was negative for both organisms and leucocytes, and no organisms were cultured during extended incubation. Extended testing was negative for staphylococcus, group A Streptococcus, group B Streptococcus, pneumococcal DNA and bacterial 16S rRNA.

Despite being on broad-spectrum antimicrobial treatment, there was a significant rise in the patient’s CRP (rising to a peak of 360) and WCC (20.8) during the week following surgery, with accompanied recurrent fever.

He was discussed with the rheumatology team 4 days postsurgery due to a concurrent episode of acute gout affecting his elbows and wrists bilaterally. They advised to commence colchicine 500 µg BD for treatment of an acute gout flare.

The samples from surgery were sent for histopathology examination and were formally reported 1-week postsurgery. Histological examination revealed foci of amorphous material surrounded by chronic inflammation, including occasional giant cells, and no evidence of acute inflammation or abscess(figure 3). Morphological appearances were suggestive of tophaceous spinal gout.

Figure 3.

Microscopy revealed amorphous material surrounded by chronic inflammation, including occasional giant cells.

The rheumatology team reviewed the patient in the neurosurgical unit and given the clinical picture and laboratory findings, diagnosed the patient with chronic polyarticular gout with spinal tophi. The patient’s serum urate level was within normal range, at 423 umol/L, this level was considered within the context of the patient having started urate lowering therapy 1 month prior. The rheumatology team advised commencing the patient on prednisolone 30 mg once daily, allopurinol increased to 200 mg once a day and colchicine reduced to 500 µg once a day. During clinical follow-up, the rheumatology team defined a 4-week weaning regimen for the prednisolone and adjusted the dose of allopurinol to 300 mg once a day.

Outcome and follow-up

The patient’s elbow pain and back pain improved significantly in the days immediately following commencement of the prednisolone, allopurinol and colchicine regimen as per the rheumatology team. He remained paraplegic with 0/5 power in his lower limb myotomes and was managed for neuropathic bladder and bowel, with catheterisation and nurse-led bowel care. One month later, the patient was transferred to the regional neurorehabilitation unit, for inpatient spinal injuries rehabilitation. All markers of inflammatory response improved following commencement of steroids and the anti-inflammatories, whereas they had continued to climb following surgery and commencement of intravenous antibiotics: CRP had improved from 360 to 14, WCC had improved from 20.8 to 9.3. No further fever was noted during the 1-month admission stay in the neurosurgery unit, once treatment for spinal gout was commenced. Antibiotics were discontinued following microbiology team consultation, following the significant clinical and biochemical improvement coincident with prednisolone, colchicine and allopurinol treatment. The patient was transferred to the neurorehabilitation unit 1 month after admission to the neurosurgery department.

Two months postpresentation, the patient continues to undergo inpatient based care in the neurorehabilitation unit. On the MRC power grading scale, he remains 5/5 in his upper limbs and 0/5 in his lower limbs. He has a T10 ASIA type-A spinal cord injury with spastic (initially flaccid) paralysis of both lower limbs and impaired sensation below his abdomen. He mobilises with a wheelchair and has an indwelling catheter, but requires assistance with washing and dressing, and is a full hoist transfer currently. The goals of his inpatient rehabilitation will be to maximise independence in bed mobility, transfers, wheelchair mobility and self-care.

Discussion

We present a case of tophaceous spinal gout causing spinal cord compression in a young man who has sustained a complete atraumatic spinal cord injury. Spinal gout is defined by the deposition of MSU crystals in the axial skeleton.⁵ Spinal manifestations of gout were thought to be rare, with the prevalence reported as low as 0.1%.⁶ However, some studies have reported the prevalence between 22% and 35%.⁴ Reporting the true prevalence of spinal gout is challenging for multiple reasons. The first epidemiological challenge is defining the study population. The prevalence of spinal gout has been reported within the context of patients presenting with back pain, and separately within the context of spinal gout among patients with chronic gout.^{7 8} Given that over 80% of the global population will report low back pain at some point during their lifetime, within the back pain population spinal gout will be far less common, compared with the prevalence of spinal gout in patients that are already known to have gout.⁹ Another challenge is the modality of diagnosis. Some studies have reported the finding of spinal gout, in symptomatic patients who met the clinical indication for surgical or radiological intervention and were diagnosed following histopathology examination, whereas in another study spinal gout was diagnosed based on CT imaging features.^{7 8} However, in this CT-diagnostic study, eight out of nine patients with radiological evidence of spinal gout were asymptomatic, which raises the third challenge of determining whether there is a subgroup of patients with chronic gout, who have radiological evidence of spinal gout, but who are asymptomatic and therefore remain undiagnosed.

Spinal gout is more common in men in their early 60s, and most patients diagnosed have a history of chronic gout.¹⁰ One review paper of 68 published cases of spinal gout reported back pain in 69% of patients, symptomatic spinal cord compression in 38% (myelopathic weakness, bladder and bowel dysfunction), radiculopathy in 25% (myotome distribution lower motor neuron weakness and dermatomal sensory disturbance) and fever in 19%. The lumbar spine was the most common location affecting 55% of cases. Uricaemia was noted in 66% of patients. Elevated ESR, CRP and WCC were reported in 25%, 16% and 13% of cases, respectively.¹⁰ Spinal gout is often misdiagnosed initially, common differentials include epidural abscess, cauda equina syndrome, chronic back pain, infective discitis and metastatic disease.^11–13

Imaging is an important part of the diagnostic workup of acute spinal disease. However, in this context MR is non-specific, with T1 and T2 signal changes ruling in abscess, discitis and malignancy. Similarly, standard CT modality is also non-specific as gout tophi are indistinguishable from degenerative and inflammatory processes. However, it should be noted that the imaging in this case showed changes in keeping with pressure erosion, a sign which should stimulate consideration of gout. Dual energy CT (DECT), originally used to diagnose urate nephrolithiasis, is an emerging technology which has been reported as being 90% sensitive and 83% for the diagnosis of gout.⁵ DECT is more tissue-specific because it uses X-rays of two different energy levels to differentiate one tissue-type from another based on their differential attenuation pattern. Urate has a specific attenuation signature with each beam, and therefore, gout tophi can be identified within the axial skeleton as distinct from other normal and pathological spinal formations. Presently, this emerging imaging modality is not yet widely available.

At present, there is no international guideline on the specific management of spinal gout, as such there is heterogeneity in the management of these patients. In the literature, management most involved combined surgical and medical management, though a minority of patients were managed with medical management alone. Most patients who had surgical intervention had a laminectomy; a small proportion also have spinal fusion.¹⁰ The role of fusion at the time of spinal decompression and washout remains controversial. This is because of the potential for uncertainty surrounding the diagnosis: spinal epidural abscess is an important differential that can cause rapid permanent neurological deterioration because of spinal cord infarction due to a combination of mechanical cord compression and infective thrombophlebitis, therefore, urgent surgical evacuation is generally indicated in the case of spinal epidural abscess even if the patient is on appropriate antimicrobial agent.¹⁴ Further to this, introducing spinal instrumentation into a septic surgical field could precipitate chronic infection, requiring revision surgery and significant morbidity for the patient.

There are limited outcome data in the literature in patients who have been treated surgically or medically for spinal gout.

In conclusion, spinal gout is a rare cause of acute spinal cord disease but is an important differential to consider especially in patients known to have chronic gout. Early surgical decompression where there is aetiological uncertainty and minimal neurology can aid in diagnosis and prevent rapid neurological deterioration. Instrumentation at the time of surgical decompression remains controversial.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).