Occipital diploic cranial fasciitis after radiotherapy for a cerebellar medulloblastoma.

Radiation-induced cranial fasciitis is a rare complication of radiotherapy, especially in an intradiploic location. The authors report such a case of cranial fasciitis in a 13-year-old girl previously subjected to cranial radiotherapy for a recurrent cerebellar medulloblastoma. The patient had undergone a gross-total removal of a medulloblastoma followed by no radiation therapy at the age of 10 years. The tumor recurred at the original site 2 years later, warranting a repeat operation with a gross-total tumor removal and subsequent radiation therapy. The follow-up MRI sequence demonstrated no abnormal appearance for 1 year, until a new enhancing mass was found within the occipital bone adjacent to the prior bone window. Following its resection, the new lesion was histologically identified as cranial fasciitis. Differential diagnosis of a well-circumscribed bone lesion should include cranial fasciitis, especially in young children with radiotherapy for a previous intracranial malignancy. Radiotherapy should be considered among the inciting factors in the development of cranial fasciitis. The osteolytic lesions of cranial fasciitis, although nontumoral and self-limited in duration, should be eligible candidates for early, total resection to avoid potential intracranial expansion.