Multiple brown tumors within the cranium, in a patient with primary hyperparathyroidism. A case report and review of the literature

Background: Brown tumors are benign, lytic, expansile bony lesions that represent a delayed manifestation of untreated hyperparathyroidism (HPT). Although they can affect any part of the skeleton, brown tumors of the calvaria or skull base are extremely rare. Accurate diagnosis is challenging, particularly in patients without other signs and symptoms of HPT. We report a rare case of brown tumors in a patient who presented with more than 4 sizable lesions that showed aggressive behavior and contributed to the patient's near-total blindness. To our knowledge, this is only the fourth case of brown tumors of the skull base and calvaria reported in the literature. Case description: A 28-year-old pregnant woman presented with a 2-month history of gradual right eye proptosis and decreased vision, a 1-day history of acute left eye visual loss, and epistaxis. Brain magnetic resonance imaging revealed multiple lesions, the largest measuring (4 x 5.3 x 5 cm) at the skull base, which occupied the nasopharynx and involved the clivus and sphenoid sinus. Another large lesion was detected at the right sphenoid bone with invasion of the right orbital wall. A nasopharyngeal biopsy showed multiple giant cells, and investigations revealed primary HPT. The patient had parathyroid adenoma resection, followed by right decompressive craniotomy to salvage vision in her right eye. She recovered well with improved right eye movements and vision. Conclusions: Diagnosis of brown tumors of the skull base requires a high index of clinical suspicion, and it should be included in the differential diagnosis in patients who present with any lytic bony lesion, even in cases of multiple lesions. Management includes accurate diagnosis and prompt treatment of the etiopathogenetic factors associated with HPT and biopsy of the bony lesions to rule out other likely conditions. However, this should not preclude decompressive surgery for neural compression-induced acute deficits.