1. Fibrous Dysplasia Jan M. Eckermann, MD Department of Neurosurgery

2. Definition Benign condition in which normal bone is replaced by fibrous connective tissue due to a defect in osteoblast differentiation and maturation

3. Epidemiology Incidence not known Females > males No race predilection Initial symptoms manifest age 3-15 Not heritable Questionable genetic transformation Malignant transformation in < 1%

4. Variations Cystic (21%) -Radiolucency surrounded by solid rim Sclerotic (23%) -Dense and homogenous Mixed (56%) -“Ground glass appearance”

5. Variations, cont’d Monostotic -Most common -25% involve head and neck Polyostotic -15% of cases -50% involve head and neck

6. Whereyouat?

7. Images Left temporal bone involvement

8. Images Right temporal bone lesion

9. Images

10. Presentation Local pain Swelling Abnormal pigmentation CN compression Spontaneous scalp hemorrhage Part of McCune-Albright’s syndrome

11. McCune-Albright’s Syndrome Polyostotic fibrous dysplasia Café-au-lait spots Endocrinopathology: -Hyperthyroidism -Precocious puberty in females

12. Imaging Plain radiography is first line Computed tomography for complex regions

13. Histology Fibroblasts within woven cancellous bone

14. Whereyouat?

15. Differential Diagnosis Eosinophilic granuloma Nonossifying fibroma Bone hemangioma Hyperparathyroidism Paget’s disease Brown’s tumor Aneurysmal bone cyst

16. Treatment No available cure Curettage Cranioplasty Calcitonin

17. The One Slide To Remember Genetic, non-heritable disorder <1% transformation to malignancy Treatment is curretage or cranioplasty

18. Whereyouat?

19. References Greenberg, M. Handbook of Neurosurgery 6 th Edition. Thieme: New York 2006 Kaye AH, Black P McL. Operative Neurosurgery Vol 2. Harcourt Publishing: New York 2000 Dal Cin P, Sciot R, Spelenberg F, et al. Chromosome Aberration in Fibrous Dysplasia. Cancer Genet Cytegent 1994 Oct15;77(2) 114-7