title: Osteomalacia caused by skull base tumors: report of 2 cases.
abstract: BACKGROUND
  Tumor-induced osteomalacia (TIO) is an uncommon paraneoplastic syndrome rarely encountered in neurosurgical practice. We report on 2 cases of TIO caused by skull base tumors. Although the diagnosis of TIO is difficult to make and often is delayed because of the insidious nature of the symptoms, mostly systemic pain and weakness, it is curable once it is diagnosed and properly treated.
  
  
  METHODS
  Both patients presented with severe pain developing in the lower extremities and moving out to the entire body, as well as difficulty moving. They were diagnosed with TIO several years after onset. A high level of serum FGF23 was confirmed, and whole-body imaging studies demonstrated tumors in the middle and anterior cranial base, respectively. The patient with the anterior cranial base tumor had a history of hemorrhage into the frontal lobe and partial resection. En bloc resection of tumor with surrounding skull bone was performed. The histological diagnosis for both cases was phosphaturic mesenchymal tumor, mixed connective tissue variant.
  
  
  CONCLUSIONS
  The level of FGF23 normalized immediately after surgery. Both patients experienced a dramatic relief of pain and recovery of muscle power. Although reports of osteomalacia caused by tumors in the neurosurgical field are extremely rare in the literature, its true incidence is unknown. We emphasize the importance of recognition of this syndrome and recommend total resection of tumors when possible.
authors.affiliation: Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan. unot-tky@umin.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Uno
authors.forename: Kensuke
authors.initials: K
authors.lastname: Kawai
authors.forename: Naoto
authors.initials: N
authors.lastname: Kunii
authors.forename: Seiji
authors.initials: S
authors.lastname: Fukumoto
authors.forename: Junji
authors.initials: J
authors.lastname: Shibahara
authors.forename: Toru
authors.initials: T
authors.lastname: Motoi
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Saito
mesh_terms: D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000378:metabolism; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology; D008579:Meningioma / Q000150:complications* / Q000175:diagnosis / Q000601:surgery; D008637:Mesenchymoma / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D008875:Middle Aged; D010018:Osteomalacia / Q000175:diagnosis / Q000209:etiology* / Q000601:surgery; D019292:Skull Base Neoplasms / Q000150:complications* / Q000175:diagnosis / Q000556:secondary / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23