Tophaceous Gout of the Spine Causing Neural Compression
A 64-year-old man was admitted to our clinic with weeklong weakness of both lower extremities. The patient also complained of back pain radiating to his left anterior chest for 4 weeks. Eight years prior, the patient had acute gout arthritis of the right knee. At that time, the symptoms spontaneously resolved, and the patient received no subsequent management for the condition. The back and chest pain had increased gradually and had become more severe over the previous month in spite of conservative treatment. A week before admission, paraparesis progressed to difficulty walking. The patient had no sphincter function impairment, fever, or weight loss.\nNeurological examination showed paraparesis with grade IV motor weakness of both the hip and knee with no sensory impairment. Reflexes were normoactive and within normal ranges as assessed using the straight leg raise test. The patient's white blood cell count was slightly increased to 10,960/mm3 (normal range: 4,000-10,000/mm3); erythrocyte sedimentation rate was 5mm/h (normal range: lower than 9mm/h); C-reactive protein level was 0.9mg/dL (normal range: lower than 0.5mg/dL); and serum uric acid level was 12.2mg/dL (normal range: lower than 7.0mg/dL). No symptoms of gouty arthritis such as pain or swelling were reported for other joints of the appendicular skeleton.\nComputed tomography (CT) demonstrated a low-density mass with calcification surrounding the T6/7 left facet articulation and T6 and T7 left lamina. Bony erosion was also observed at the T6/7 left facet articulation (). Magnetic resonance imaging (MRI) of the thoracic spine revealed an extradural mass compressing the posterior of the spinal cord at T5-7, with heterogeneous high and low signal on T2-weighted images and low signal on T1-weighted images. The small amount of the low signal intensity of the mass on T2-weighted MRI corresponded to the calcified lesion on CT, and this lesion showed peripheral enhancement on post-contrast MRI ().\nWe made a tentative diagnosis based on the imaging findings of an epidural cyst or benign bone-originating tumor. Thoracic laminectomy from T5 to T7 was performed for the purpose of neural decompression and for histopathological confirmation. Intraoperatively, a chalky white material was found at the interlaminar space. This material extended to the dorsal space of the thoracic dura and the T5/6, T6/7 left foramen (). After left T5/6, T6/7 facetectomy, the mass that was compressing the cord and root was removed and T5, 6, and 7 both pedicle screw fixation with posterolateral fusion was performed.\nHistopathological examination of the specimen by polarized light microscope demonstrated a granular material with a needle pattern and negative birefringence (). This finding confirmed a diagnosis of a gouty tophus. No neoplastic tissue was found in the specimen. Postoperatively, the patient regained strength in both lower extremities, and his back and chest pain attenuated. After being discharged from the hospital, the patient has been treated with medication.