Bilateral intracranial subdural osteomas of varying sizes imaged 7 years apart: illustrative case

BACKGROUND: Previously, solitary and unilateral aggregates of intracranial subdural osteomas have been described. These tumors are thought to be slow growing and at times inconsequential on the basis of characteristics of subjacent brain. Unilateral location and history of traumas have led to the thought that the head trauma may play a role in pathogenesis. OBSERVATIONS: The authors describe a unique case of a patient who was found to have bilateral intracranial subdural osteomas of unequal size on the basis of computed tomography and magnetic resonance imaging. The presenting symptom was headache. Initially small and thought to be irrelevant, these tumors grew over the course of 7 years to cause mass effect and effacement of the sulci and gyri. The larger 15-cm-long tumor was excised and was sent for pathology, which showed classic histology for subdural osteoma. LESSONS: The described case uniquely demonstrates evidence of the slow growth of intracranial subdural osteomas over the course of years. It is crucial not to disregard the tumor because it can grow over time to cause mass effect. Patient follow-up is strongly recommended. Bilateral tumor occurrence at a similar location in this case supports an etiology other than trauma. Further research is necessary.