Fibrous Dysplasia of the Parietal Bone with Focal Motor Seizures: A Case Report.

BACKGROUND Monostotic fibrous dysplasia is a benign proliferation of fibrous and osseous tissues that expand medullary bone to cause symptoms due to compression of adjacent organs and anatomical structures. Focal seizures are rarely the first sign of this kind of lesion. This report describes a young female patient with left-sided focal motor seizures associated with fibrous dysplasia presenting as a mass in the right parietal bone. CASE REPORT An 18-year-old female student with left-sided focal motor seizures presented with a mass in the right parietal bone. Computed tomography revealed an expansile mixed-density lesion on the right parietal bone, a relatively homogeneous ground-glass appearance in the outer circumferential portion, and a lucent eccentric area with thinned but sclerotic borders. Magnetic resonance imaging revealed a homogeneously hypointense signal on T1WI, a small hyperintense signal on T2WI, and avid enhancement signal intensity on post-contrast T1. Electroencephalogram showed inter-ictal epileptiform activities derived from the right fronto-central lobe. Surgical en bloc resection with a margin of normal bone and cranioplasty were performed. Histopathology showed features indicative of fibrous dysplasia, including osteoid trabeculae arranged haphazardly in a dense fibroblastic stroma, irregular trabeculae lacking conspicuous osteoblastic rimming, and intervening fibrous stroma containing cytologically bland spindle cells. The patient achieved seizure control and has remained neurologically intact. CONCLUSIONS This report has highlighted the importance of early diagnosis of fibrous dysplasia of bone to exclude primary bone malignancy or bone metastasis, to ensure rapid management and symptom control.