Brown tumor due to primary hyperparathyroidism resulting in acute paraparesis: Case report and literature review
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How to cite this article: Shaaban AT, Ibrahem M, Saleh A, Haider A, Alyafai A. Brown tumor due to primary hyperparathyroidism resulting in acute paraparesis: Case report and literature review. Surg Neurol Int 2020;11:355.
Abstract
Background:
Brown tumor (Osteoclastoma) is a rare benign, focal, lytic bone lesion most commonly attributed to a parathyroid adenoma; it occurs in approximately 5% of patients with primary hyperparathyroidism, and 13% of patients with secondary hyperparathyroidism. Most tumors are located in the mandible, pelvis, ribs, and large bones; only rarely is it found in the axial spine.
Case Description:
A 37-year-old male with primary hyperparathyroidism presented with an MR-documented T4 and T5 brown tumor (Osteitis Fibrosa Cystica) resulting in an acute paraparesis. The patient successfully underwent excisional biopsy of an expansile, enhancing, bony destructive lesion at the T4-5 level. Subsequently, he required subtotal excision of a left upper parathyroid tumor.
Conclusion:
Patient with primary hyperparathyroidism may acutely present with paraparesis attributed to brown tumors of the spine warranting emergent operative decompression.
Keywords
INTRODUCTION
Brown tumor (Osteoclastoma) is a rare, benign, and focal lytic bone lesion that is most commonly attributed to a parathyroid adenoma. It occurs in 5% of primary and 13% of secondary cases of hyperparathyroidism.[8] These lesions are typically found in the mandible, pelvis, ribs, and large bones; only rarely do they involved the axial spine.[3] They are called brown tumors due to their high hemosiderin content. The term osteitis fibrosa cystica reflects their intrinsic peri trabecular bone fibrosis (osteitis fibrosa), and increased osteoclastic activity causing lytic bone lesions.[8] Notably, they may mimic metastatic lesions. Here, we present a 37-year-old male with an MR-documented T4-T5 thoracic brown tumor resulting in paraparesis due to primary hyperparathyroidism.
CASE PRESENTATION
For 2 months, a 37-year-old male demonstrated a slow-growing lesion involving the dendro-alveolar segment of the left upper maxilla (rounded mass of 4 × 4 cm, nonulcerated with normal oral mucosa) [Figure 1]. The biopsy was consistent with a peripheral giant cell granuloma. Two months later, he newly presented with back pain, and 6 days of the lower extremity weakness. On examination, he exhibited bilateral iliopsoas/ quadriceps (4/5)/bilateral extensor hallucis/dorsiflexor (2/5) weakness, and a left Babinski response. The laboratory studies revealed a marked elevation in both the calcium-corrected and alkaline phosphatase levels.
Holospinal contrast enhanced MR
Multiple, expansile, enhancing, and bony destructive lesions were seen at many thoracic, lumbar, and sacral spinal levels (e.g., involving mainly the neural arches, and adjacent soft tissues). The largest lesions were at the T4/T5 level; the first contributed to marked central cord compression, while an additional very large, expansile, destructive bony lesion involved the left – T4-T5 ribs, and infiltrated into the adjacent paraspinal muscles. Other similar and/or smaller lesions involved multiple spinous processes, lamina, and/or vertebral bodies (e.g., of C5-6, L2-L4, S1-S2, and the left iliac bone). There was also an accompanying dorsal thoracic scoliotic deformity convex to the right side [Figure 2].
Surgery
Due to significant cord compression, a T4/T5 coronal hemilaminectomy was performed with medial facetectomy/ foraminotomy; care was taken to preserve the lateral two-third of the facet joints, and thus maintain stability. The soft and highly vascular T4-T5 tumor clearly compressed the thoracic cord, and infiltrated the para spinal ribs/muscle; tumor was readily debulked. The histopathology confirmed a brown tumor attributed to primary hyperparathyroidism [Figure 3]. Up to 2 years postoperatively, the patient remained neurologically intact with continued spinal stability.
Diagnosis of primary hyperparathyroidism
Primary hyperparathyroidism attributed to a parathyroid adenoma caused this patient’s elevated parathyroid hormone (PTH) level (e.g., 1900 ph\ml). The patient subsequently required excision of the left upper parathyroid gland, following which calcium levels normalized [Figures 4-6].
DISCUSSION
Brown tumors are rare benign, lytic bone lesions that appear grossly as soft, red brown expansile masses within the bone. They occur due to primary, secondary, or tertiary hyperparathyroidism.[6] Twenty-five similar cases of spinal brown tumors due to primary hyperparathyroidism have been described in the literature (e.g., 1968 to the present) [Table 1].[1-10] Patients typically range from 16 to 69 years of age, and more females than males are impacted (e.g., 15 females vs. 10 males). The most common location for brown tumors is the thoracic spine where presenting symptoms/signs typically range from back pain/ radiculopathy, to myelopathy with paralysis with/without sphincter disturbances. Treatment options typically include: conservative management or surgery (e.g., biopsy/ resection with/without instrumentation). Of the 25 prior cases reviewed, all except two underwent additional parathyroidectomy.
Pathogenesis of brown tumors
Primary hyperparathyroidism and resultant spinal brown tumors are attributed to adenomas, resulting in elevated PTH, and heightened calcium levels; both contribute to abnormal bone mineralization. They also result in decreased bone density, and increased bone resorption (e.g., due to heightened osteoclastic activity that progressively thins the bony cortex, and trabeculae). Resultant microfractures/microhemorrhages increase the activity of multinucleated macrophages, contributing to the formation of fibrous tissue resulting in osteitis fibrosa cystica. Notably, the typical brown tumors reflect the accumulation of hemosiderin.[6]
Differential diagnosis of brown tumors
The differential diagnoses for brown tumors include: metastases, multiple myeloma, sarcomas, giant cell reparative granulomas, lymphangiomatosis, leukemia, Langerhans cell histiocytosis, multiple bone cysts, aneurysmal bone cysts, and nonossifying fibromas.[2,6,8]
Treatment of brown tumors: medical versus surgical management
There is an ongoing controversy regarding the comparative efficacy of parathyroidectomy with/without the need for attendant spine surgery.[4] Treatment of spinal brown tumors due to primary hyperparathyroidism typically includes initial resection of the parathyroid adenomas often normalizing PTH levels, contributing to remineralization, and the resorption of spinal lesions.[4] However, for patients presenting with significant spinal cord compression due to brown tumors, immediate operative decompression/ stabilization may be necessary, followed secondarily by resection of parathyroid adenomas.[1,3,5,8,9] For the case presented, the patient’s initial significant paraparesis due to the T4-T5 largest compressive spinal lesions warranted operative decompression, both to reverse the neurological deficit/paraparesis, and provide a tissue-diagnosis.
CONCLUSION
Patients with primary hyperparathyroidism may acutely present with paraparesis attributed to thoracic brown tumors warranting emergent operative decompression, followed by resection of parathyroid adenomas.
Declaration of patient consent
Institutional Review Board (IRB) permission obtained for the study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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