Quiz Page September 2008: Progressive Paraplegia in a Long-term Hemodialysis Patient

Clinical Presentation 

A 47-year-old man with a 6-year history of end-stage renal disease managed by hemodialysis therapy was admitted for rapidly progressive bilateral lower-extremity weakness and numbness. The weakness had started 4 days earlier and was not associated with trauma or injury. Neurological examination showed spastic paralysis of bilateral lower extremities. The tendon reflex was symmetrically hyperactive in the lower extremities, and Babinski sign was elicited bilaterally. Sensory examination showed hypoesthesia to touch, pain, and temperature below the level of the umbilicus, and muscle strength of the lower limbs was decreased to 4 of 5. Laboratory tests showed the following values: slightly increased total serum calcium, 10.3 mg/dL (2.56 mmol/L); serum phosphorus, 5.8 mg/dL (1.87 mmol/L); serum alkaline phosphatase, 350 U/L; and intact parathyroid hormone level (iPTH), 1,301 pg/mL (normal range, 0 to 62 pg/mL) measured using enzyme-linked immunosorbent assay. Magnetic resonance imaging (MRI) for the spine was performed.

■ What do you observe on the spine magnetic resonance image in Fig 1?

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Figure 1. Magnetic resonance image of the spine.

■ What is your diagnosis?

■ What is the treatment?

Discussion 

■ What do you observe on the spine magnetic resonance image in Fig 1?

MRI showed a tumor in the T4 vertebral body and left neural arch. Spinal compression is caused by protrusion of the posterior wall of the T4 vertebral body into the spinal canal (Fig 1A to C). The differential diagnosis includes spinal tuberculosis, bacterial or fungal abscess, and metastatic tumor.

■ What is your diagnosis?

This patient on long-term hemodialysis therapy with progressive paraplegia, a tumor detected by using MRI, and increased alkaline phosphatase and iPTH levels is suspected to have a brown tumor. Brown tumors are caused by hyperparathyroidism1, 2 and characterized by increased osteoclastic activity and mass effect, resulting in paraplegia when involving the spine.3, 4 Secondary hyperparathyroidism is common in patients on long-term hemodialysis therapy.4 The pathophysiological process of this disorder is related to phosphate retention, altered metabolism of vitamin D, skeletal resistance to PTH, impaired degradation of PTH, and altered regulatory feedback of PTH by calcium. Osteoclast activation is induced by the high level of PTH, resulting in aggressive bone resorption and osteitis fibrosa. Histological studies found that this appears as microfractures and microhemorrhages, with hemosiderin-filled macrophages and osteoclasts dispersed throughout fibrous tissue within the marrow spaces. Progressive focal bone resorption and fibrosis result in visible cysts that coalesce to form brown tumors.4 Tests for prostate-specific antigen, radionuclide bone scanning, and abdominal and thyroid gland ultrasonography should be performed to exclude other primary tumors. Histological examination confirmed brown tumor (Fig 2).

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Figure 2. Histological examination of T4 brown tumor. Among sheets of fibroblasts are numerous giant cells and microfoci of hemosiderin deposition. (Hematoxylin and eosin stain; original magnification ×400.)

■ What is the treatment?

The T4 vertebral body, left neural arch, and vertebral plate were surgically removed and replaced with a titanium cage filled with autologous bone, followed by internal fixation with a nickel clad that connected to the bone with screws from T3 to T5 (Fig 3). General treatments for patients with brown tumors are to control serum phosphate levels by restriction of dietary phosphorus intake and phosphate-binding antacids and to select a high phosphate clearance dialyzer. Adequate calcium intake should be ensured with oral calcium supplements. With the development of skeletal disease and uncontrolled severe hyperparathyroidism, pulse therapy with calcitriol or a subtotal or total parathyroidectomy may need to be performed.

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Figure 3. Postoperative (A) anteroposterior and (B) lateral radiographs 1 year after internal fixation from T3 to T5.

Final Diagnosis 

Brown tumor compressing the thoracic spinal column.