Mohammad Sami Walid 1, Joshua C. Yelverton 2, Mohammed Ajjan 3, Arthur A. Grigorian 3
Medical Center of Central Georgia 1, Mercer University 2, Georgia Neurosurgical Institute 3, USA
Objective & Importance: Crystal-induced arthritis (gout and pseudogout) usually affects peripheral joints whereas spine involvement with severe myelopathy is extremely rare. PubMed search yielded 42 results for “gout myelopathy” and 35 results for “pseudogout myelopathy”.
Clinical Presentation: We are reporting the case of a 62 years old female Caucasian who presented with severe thoracic myelopathy. MRI of the spine with contrast showed a 1.0´1.7 cm epidural soft tissue nodule with peripheral enhancement posterior to the thoracic cord at T9-10.
Intervention: Decompression and excision of the lesion was performed. Pathology revealed rhomboid-shaped, positively birefringent crystals. Uric acid was normal. The diagnosis of pseudogout was established.
Conclusion: Spinal crystal arthropathy should be considered in the differential diagnosis when a patient presents with symptoms of myelopathy and imaging shows an epidural lesion in the spinal canal.
Keywords: pseudogout, spine, myelopathy.
Crystal-induced arthritis usually affects peripheral joints, including the knee, ankle, wrist, and metacarpophalangeal and metatarsophalangeal joints. There are two types of arthritis caused by deposition of crystals: gout and pseudogout. Gout is a common differential diagnosis of acute arthropathy. It is caused by the deposition of monosodium urate crystals in the tissue or synovial fluid and the formation of tophi with recurrent attacks. Pseudogout is caused by the deposition of calcium pyrophosphate dihydrate (CPPD) crystals, which leads to acute, subacute or chronic inflammation of the joints.
Pseudogout, also known as CPPD deposition disease (CPPDDD), can cause severe episodes of localized pain and swelling resulting in incapacitation for days or weeks. It can also cause more chronic arthritis that mimics osteoarthritis or rheumatoid arthritis. The most common sites of pseudogout arthritis are the knee, wrist, and shoulder. In the literature, there are rare case reports of pseudogout forming masses in the spinal ligamentum flavum . Four cases have been reported by Lam et al., 2007, with gout or pseudogout in the lumbar spine . Two had cauda equina syndrome and another two had spinal stenosis. Yen et al., 2002, reported the case of a 68-year-old male with a long history of diabetes mellitus and hyperuricemic gout where neck pain developed over two weeks with subsequent quadriparesis and concomitant subcutaneous deposition of gouty tophi in the right elbow . Kao et al., 2000, reported the case of an 82-year-old man who developed progressive weakness of both legs 1 month prior to admission . MRI of the spine disclosed segmental stenosis with cord compression at T10-11 due to an extradural soft tissue lesion. Pathology proved it to be a gouty lesion. PubMed search yielded 42 results for “gout myelopathy” and 35 results for “pseudogout myelopathy”.
We are reporting the case of a 62 year-old female who developed severe myelopathy over three weeks. MRI of the spine showed a compressing lesion in the thoracic spine which later proved to be a pseudogout lesion.
A 62-year-old female Caucasian presented following three weeks of severe back pain which radiated down the left leg. The left leg had weakened and the patient required a walker for ambulation inside the house. She noticed increased urine urgency and several bouts of uncontrolled bowel movements. Past medical and surgical history included high blood pressure, two neck surgeries and one back surgery. Her father died of an unknown-type neck cancer. There were signs of severe thoracic myelopathy. CT of the thoracic spine without contrast revealed a 1.5´0.9 cm posterior epidural soft tissue nodule encroaching upon the thoracic spinal cord at the T9-10 level. MRI of the thoracic spine with contrast showed a prominent 1.0´1.7 cm soft tissue focus in the posterior central spinal canal at the T9-10 level with significant anterior displacement and flattening of the thoracic cord resulting in abnormal cord signal at this level (Figure 1).
Decompressive laminectomy, T9 through T11, was performed. An epidural mass originating from the yellow ligamentum was exposed which severe compression of the dorsal spinal cord. Material was sent for frozen section examination which came back indicating the presence of crystals. Eventually, the entire lesion was resected. The examination of these crystals under polarized light showed yellow rhomboid-shaped crystals perpendicular to the slow wave length indicating they are pseudogout (Figure 2). There was no evidence of malignancy in the specimen. Uric acid level was then checked and proved normal.
CPPD deposits seen in pseudogout affect approximately 3% of people in their sixties and as many as 50% of those in their nineties . CPPD crystals are produced by nucleoside triphosphate pyrophosphohydrolase (NTPPPH), a catalytic enzyme found in vesicles that develop within osteoarthritic cartilage . The exact pathogenesis is not clear, but the chondrocyte and surrounding matrix appear to be involved. Some noxious event (physical or chemical) appears to incite a cascade that evolves toward the hypertrophy and degeneration of chondrocytes. Intracellular material escapes to the surrounding matrix and potentially alters the calcium-binding effect of the matrix proteoglycans. Calcium pyrophosphate crystals grow adjacent to these hypertrophic chondrocytes within the affected matrix . The breakdown of collagen cells has been proposed as the source of the inorganic pyrophosphate.
Because the condition sometimes runs in families, genetic factors have been suspected of contributing to the disorder like a severely underactive thyroid, subclinical anomalies in iron storage, low magnesium levels in blood, an overactive parathyroid gland and other causes of excessive calcium in the blood (hypercalcemia) [3, 6]. Any kind of insult to the joint can trigger the release of the calcium crystals, inducing a painful inflammatory response. Attacks of pseudogout also can develop following joint surgery. They have also been reported following etidronate disodium therapy and post vascular angiography .
While gout may affect younger male patients, both gout and pseudogout occur more often in both genders of the older population [3, 8]. They cannot reliably be distinguished on clinical grounds, but a tendency exists for gout symptoms to develop rapidly over a few hours, whereas the onset of symptoms in pseudogout is usually more insidious and may occur over several days. When the joint fluid is aspirated and examined under the microscope, gouty arthritis is characterised by needle-shaped, negatively birefringent crystals under polarised light, whereas pseudogout shows rod- or rhomboid-shaped, positively birefringent crystals. When monosodium urate is aligned with the slow vibration, it appears yellow, a sign of negative birefringence, whereas calcium pyrophosphate is blue and positively birefringent (Figure 2). Likewise, when the crystals are aligned opposite the slow vibration, monosodium urate will appear blue and calcium pysophosphate will appear yellow.
It should be noted that cases of thoracic ligamentum flavum ossification may present similarly . In every such case, the excised specimen should be examined with polarized-light microscopy. This simple, inexpensive method will probably lead to the recognition of more CPPDDD cases.
In the rare cases of crystal-induced arthritis (gout or pseudogout) affecting the spine, diagnosis may be suspected clinically, but can be confirmed only through pathological examination. Crystal-induced arthritis should be considered in the differential diagnosis of patients with space-occupying lesions of the spine.